Chapter – 1INTRODUCTIONGENERALThe main task of the impermeable land fill liners is to reduce the migration of leachate to the ground water and to reduce its rate to reasonable amount. The import ants of landfill throughout world increases and need of engineered waste dumps is necessary. Land fill liners are exposed to various types of physical, chemical and biological processes and are affected by leach ate produced from the decomposition of waste dumps. Due to these the importance of Geo-technical characteristics of clay liners are determined in the laboratory. The main criteria for impermeable liners are their hydraulic conductivity, in present study, the characteristics of clay bentonite and quarry dust is determined with 3%, 6%, 9%,12% and 15%.
The main reason for using these mixers is to reduce the hydraulic conductivity, which eliminates the movement of leachate from bottom of the landfills.1.1.1 CLAYEY SOIL: Clayey soil occurs in three types of minerals such as montmorillonite, kaolanite and illite. Montmorillonite type of clay has more swelling and shrinkage, due to these shrinkage cracks may develop increases migration of leach ate to ground water. Present study these type of clayey soil not useful.
Kaolanite type of has less swelling and shrinkage property arrest the leachate. Illite type of clay has intermediate between Montmorillonite and Kaolanite. In the present study, Kaolanite and illite type of clay is used for landfill liner material.
Cohesive fine grained soils such as locally available clay, bentonite, and quarry dust were used as barrier to landfill liners. The mineral present in bentonite type of clay is montmorillonite. Montmorillonite has large specific surface area is about 800 m2/gm. Montmorillonite has large negative charge ,due to this it absorbs large quantity of hydrated cat ions and also it absorbs water moleculesGrim, R.E 1968, Clay mineralogy. Due to hydration intermolecular separation may takes place and pore space may developed. Relatively montmorillonite has less pore space Mesri G.
and Olson.relatively small pore spaces occupied by water and which leads to reduction of hydraulic conductivity of montmorillonite. Bentonite can also increase the plasticity index of clayey soil in mm Ziaie – Moyed, R and Naein.
Design of landfill liners is dependent on geo-technical properties of materials such as clay, bentonite, and quarry dust used as landfill. So, prior to construction stage, geo-technical properties are determined and these applicable to design framework. Engineering and index properties of soils are determined using distilled and tap water such as Atterberg’s limits, compaction tests, hydraulic conductivity and unconfined compressive strength. Clay liners are exposed to various chemical, biological and physical processes produced from leachate and biodegradation process.Atterberg’s limits are used for representative parameter estimate the clay behavior. These limits are depended on various engineering properties such as permeability, compressibility etc. Liquid limit more influenced on clay behavior.
The liquid limit and plasticity index are highly influenced by the ability of clay minerals. When liquid interact with clay minerals, the properties are increased and hydraulic conductivity tends to decreases Alawaji H.A and Met, I, et al in 2005.In recent years, number of researchers determined the interaction of clay with different types of fluids. For landfill liners hydraulic conductivity is one of the important soil characteristics which is always less than or equal to 10-7cm/sec. Fluids are more effect on geotechnical properties of clayey soil. 1.
2 NEED OF THE PROJECTClay-Bentonite mixer is used for avoid of leachate produced from leachate production. Present days number of governments have interested to constructed engineered landfills prevention of contamination of ground water. House wastes, hospital wastes, street etc. collected by various trucks and dumped at common place. Such type of dumps is not treated, which tend to pollution. Leachate produced from waste dumps and causes ground water contamination.
Figure 1.1 Clayey soilDue to these, the study of arrest leach ate to contamination of ground water is needed engineered waste dumps. In the present study was undertaken to investigate the effect of some components produced from leachate. Soil collected from landfill near Devuni Kadapa road by-pass dump site, the properties of clay – bentonite mixers are studied. Tests are carried out on clay alone to determine the amount of bentonite was added. Based on the plasticity character of clay, % of bentonite added is decided. Number of researchers studied on different types of soil mixers.1.
3 SCOPE OF THE PROJECT The present study is numbers of researchers have investigated the clay soil interaction with different type of mixers with different liquids. Some of these studies are to reduce the conductivity of soil-mixers with comp active efforts. Where ever locally available soils are used for liner material with low conductivity clay are available, they give the more economical lining material to landfill. Naturally available clays may satisfy the good liner material.Kabir et al., (2004) studied the plutonic igneous soil as a liner material.
He absorbed the physio-chemical properties concluded that soil satisfies the basic requirements of good barrier to landfill liner. For obtaining uniform soil mixer on site, blending soil with pulverizing mixer reduce the clod size. He given results that high plasticity (35%) depends on workability and exhibit small shrinkage upon drying.Kolawole et al.
, (2005) conducted on three lateritic soils with four comp active efforts hydraulic conductivity reduces to 10-7 cm/sec, lateritic soil known as kaolanite mineral rich in clay. He concludes that soils should be compacted to a minimum dry density of 16 KN/m3 with degree of saturation 86% with minimum comp active effort.Teha et al., (2005) have suggested that granite residual soil is used as compacted liner material.
In the laboratory proctor compaction tests are conducted to soils, by applying compaction energy at moisture content to dry side of 4.2 % and wet 0.4% .from these study he gain the low conductivity to gain adequate strength and minimum shrinkage. Given scope by previous investigators to use kaolanite type of clay (lateritic soil) mixed with bentonite used as liner material. Clay with three percentages 2.
5%, 5.0 % and 7.50 % tests were repeated with three different percentages.1.4 LANDFILLS AND LINERSThe majorities of house waste, street litters, hospital wastes, waste collected from parks are collected from various services provide by municipal authorities and dumped at common point called as landfill. These waste dumps consisting of various materials which are toxics. So, the need of engineered landfills is required to minimize ground water contamination.Design and construction of sanitary dumps has become one of the important responsibilities of various governments throughout the world.
Sanitary landfills are divided into two kinds: Geo-synthetic clay liners (GCLs)Compacted clay liners (CCLs)1. GEOSYNTHETIC CLAY LINERSGCLs are factory-manufactured, hydraulic barriers are consisting of bentonite mix with clay supported by geotextile which replace compacted clay liners or they type of material, or they can be used in a clay with geotextile the more traditional compacted clay or geomembranes materials.2. COMPACTED CLAY LINERThis is a leakage arresting material to construct by a cohesive soil, which is compacted to increases the unit weight of soil and reduce the space between particles and also reduce the flow of water in soil. By using earth, form structure, the compacted clay liner is designed to reduce the seepage of liquid manure.The purpose is to reduce porosity and decrease soil permeability.
Within the earthen manure storage structure, the compacted clay liner is designed to impede seepage of the liquid manure. Requirement for a Compacted Clay Liner – Depending on the site’s geological and hydro geological features, an earthen manure storage structure may be required to contain a liner. The construction of a compacted clay liner is an option.
Present, clay material characteristics are studied. However, a mixer of near available clay such as cohesive soil and bentonite clay may be used as land fill liners.When low-permeability clay is not available locally, in-situ soils may be mixed with medium to high plasticity imported clay to achieve the required low hydraulic conductivity. Few researchers have suggested blending of different soils to be used as a liner material.109537445721 Figure 1.2 Soil collected near ChenurFigure 1.3 Dump site near bypass1.
5 GENERAL REQUIREMENTS FOR DESIGN Design guidelines used to frame regarding the properties of the materials used as a barrier in landfills. Such materials should be chosen according to these criteria. So, the geotechnical properties and suitable to design frame work must be determined before construction Winter.2007.1. Atterberg’s limits, compaction tests and hydraulic etc. tests are executed using distilled or tap water.
Atterberg’s limits are the basic parameter to estimate the clay behavior such as properties such as permeability, shrinkage and swelling behavior, shear strength and compressibility of soil.2. Liners are exposed to various chemicals produced from Leachate production .generally tests conducted in laboratory are quite different from in-situ geotechnical properties.
3. Hydraulic conductivity is the other important basic parameter; it is always less than 1×10-7 cm/sec. the conductivity of the material decreases when the liquid limit and plasticity index are increases.4. Bentonite available in two states such as sodium Bentonite and calcium bentonite, based on water adsorption capacity given by Gleason et al. he concluded that the liquid limit and plasticity index decreased with increase of salt concentration.The properties of chemical solutions (NaPo3 and CaCl2)are given by Park et al. on two soil samples (out of percent Kaolanite clay soil and one sixth of Kaolanite and remaining sand) they given that due to calcium chloride no effect on the consistency values decreases by using Kaolanite type of soil.
The present study was taken to know the characteristics of some components found in the waste picked from local land fill site near bypass. Also properties of clay bentonite mixers were studied.5. The thickness of the compacted clay liner shall be 1.0m; it is measures always normal to the slope and floor of the storage structure.6. CCL’S are shall not be constructed below water stagnated areas.
7. The material collected from local should be check before to be used in the construction of liner shall be found for size distribution following ASTM D2487 and ASTM 422-63, and Atterberg’s Limits calculated by using code. 8. Acceptable size of Particle Ranges in terms of weight.• Percent Fines should be greater or equal to 50 %; • Clay percentage above said 20 %; • Sand Content ? 45 %; Fine grained soil is defined as the material which passes through a 75 micron IS sieve; clay and sand are defined as the material which considered from method ASTM D2487-00. Acceptable Atterberg’s Limits: • Plasticity Index is greater or equal to 20%• Liquid Limit is also be same as equal to or greater than 30 % 9.
Poorly graded material with more silt present in the testing not considered. Such type of soil is not compact well.10. Geotechnical information including: • Bore hole logs for the clay borrow pit; • Material specifications; • Description of soil testing and analyses; • All applicable soil testing results; and • Depth to seasonal high ground water. From the above data, Kaolanite type soil is used to reduce the peculation of leach ate.
The area is less as compared to remaining minerals (montmorillonite and illite).the locally available material is used for liner material. Electrical conductivity of the soil is more directly used as barrier. Due to this bentonite, quarry dust, clay mixed with different proportions (3%,6%,9%,12%,15%), the hydraulic conductivity is drastically reduced. upon these percentages the compaction characteristics and axial stress also carried out.
Soil taken from the different places, the pollutants present in the wastes is also carried out. Some of toxic produced from the wastes and are exposed to soil material. The available laboratory, characteristics of clayey soil alone and mixed with bentonite with different proportions, compaction characteristics are checked at each percentage. Finally the properties of soil are carried out soil alone and mixed with proportions. The chemicals present in the wastes are carried out, collected from the landfill.1.6 AREA OF STUDYFrom the above data, Kaolanite type soil is used to reduce the peculation of leach ate. The area is less as compared to remaining minerals (montmorillonite and illite).
the locally available material is used for liner material. Electrical conductivity of the soil is more directly used as barrier. Due to this bentonite clay mixed with different proportions (3,%6%,9%,12,%and 15 %), the hydraulic conductivity is drastically reduced. upon these percentages the compaction characteristics and axial stress also carried out.
Soil taken from the different places, the pollutants present in the wastes is also carried out. Some of toxic produced from the wastes and are exposed to soil material. The available laboratory, characteristics of clayey soil alone and mixed with bentonite with different proportions, compaction characteristics are checked at each percentage.
Finally the properties of soil are carried out soil alone and mixed with proportions. The chemicals present in the wastes are carried out, collected from the landfill.1.7 ORGANIZATION OF THE THESISThe present work has the following organization.Chapter 1: IntroductionThis chapter includes the introduction, need of the project, general requirements and scope of the thesis.
Chapter 2: Literature ReviewThis chapter includes the clayey soil as liner material, efferent types of clayey soils, clay mixed with bentonite and literature summary.Chapter 3: MethodologyMethodology includes the general, soil sampling and testing, index and engineering properties, chemical analysis of waste materials alone and mixed with low permeable soil and leach ate study in kadapa land fill. Chapter 4: Results and discussionsThis chapter includes the results of various tests performed in the laboratory like index and engineering like compaction, ucc’s and chemical properties. Chapter 5: ConclusionThese chapters conclude results shown comparison with the previous authors.Chapter – 2LITERATURE REVIEW2.1 INTRODUCTION The purpose of this study is to know the previous studies are use and naturally available clays as impermeable clays as liner material used for landfills. For the last three decades, throughout the world numbers of landfills were constructed. The main characteristics of the liner soil have a low hydraulic conductivity; the main key function of the liner function is to reduce the flow of contaminants.
The other properties of soils are compaction; unconfined compressive strength, permeability etc. are needed. The properties of the Bentonite are studied and Design of the Land fill are also carried out.2.2 SOILS AS A LINER MATERIAL The practice of compacted clay liners (CCL) started in the last three decades (Daniel, 1993).
Since then, a large number of landfills have been constructed worldwide, based on the performance of the constructed facilities. Researchers have also been trying to use locally available soils as liner material in landfill. Wherever suitable low hydraulic conductivity natural clay materials are available, they provide the most economical lining material and are commonly used. Natural clays usually satisfy basic requirements of the good liner material. When low permeability clay is available locally used for present work. Generally hydraulic conductivity is not supported for compacted clay liners; soil is mixed with high plastic clay such as Bentonite to achieve the required low hydraulic conductivity.
Yahia et al., (2005) studied the possibility of using crushed shales as landfill liners and reported that the crushed shales satisfy the all geotechnical properties and chemical analysis for clay liners and the compacted shales have low compressibility and no serious post construction settlement is expected for all level of compaction. Kabir et al.
, (2004) measured certain physio-chemical properties of the granite residual soil to assess its suitability as a soil liner material. From the physio-chemical properties it was concluded that the granite residual soil can be used as suitable liner material for isolating waste materials in landfills and the sol satisfies all the basic requirements of the suitable liner material. Though, its high plasticity (i.e.35%) proved to be an issue for workability and exhibits small shrinkage potential upon drying. It is recommended that considerable care should be taken during the preparation of soil.
Blending the soil on site with a pulverizing mixer would be helpful in reducing clod size and obtaining uniform moisture content.Kolawole et al., (2005) Hydraulic conductivity tests were conducted on three samples of lateritic soil with four comp active efforts. It was concluded that to achieve a hydraulic conductivity value less than 1×10?7 cm/s, the lateritic soils that should be compacted to a minimum dry unit weight of 16.0kN/m3, with a minimum initial degree of saturation of 86% using a compaction energy that is at least at British Standard Light (BSL).The main reason for using low hydraulic conductivity materials is to arrest the movement of the leachate from bottom of the landfills and produces gases.
Natural clays usually satisfy the specification of liner material. The minerals present in clays are montmorillonite, kaolanite and illite.2.
3 CLAY MIXED WITH BENTONITE AND QUARRY DUSTWhen low-permeability clay is not available locally, in-situ soils may be mixed with medium to high plasticity imported clay to achieve the required low hydraulic conductivity. Few researchers have suggested blending of different soils to be used as a liner material.Ameta et al.
, (2008) reported that the permeability is greatly affected by adding bentonite to dune sand. Hydraulic conductivity reduced from 1×10-4 cm/s to 1×10-8 cm/s after 10% bentonite was added to the dune sand and compacted to maximum dry density at optimum moisture content. The coefficient of consolidation decreases with lower bentonite to dune sand ratios. Gueddouda et al., (2008) studied the hydraulic conductivity of dune sand with bentonite mixers and concluded that 12% bentonite is the minimum requirement in the mix to achieve the require resistance to the percolation of the water.Amedi et al., (2012) studied the acceptable hydraulic conductivity of lateritic soil blended with bentonite clay.
Lateritic soil treated with up to 10% bentonite clay, prepared at various compaction states (dry of optimum, optimum and wet of optimum moisture content) was compacted with four comp active efforts (i.e., the reduced British Standard Light, British Standard Light, West African Standard and British Standard Heavy) to simulate the range of compaction energies expected in the field.
They concluded that lateritic soil with 10% bentonite clay mixture satisfies the minimum hydraulic conductivity requirements on wet side of optimum for clay liner.895350-253365 Figure.2.1 Compaction curve for blended soil923925-133985Figure.
2.2 Hydraulic conductivity for the blended soilAllamprabhu et al., (2012) studied the geotechnical characteristics of clay mixed with marine clay. Lithomarge clay blended with marine clay at 20% satisfies the criteria for hydraulic conductivity at initial degree of saturation of 78.5 % to 96.4 % and also satisfies all other properties of liner systems.Tay et al.
, (2000) studied the shrinkage and desiccation cracking exhibited by Bentonite enhanced sand mixer upon drying. Compacted bed of BES containing 10 % and 20 % bentonite do not shows desiccation cracking, if volumetric shrinkage during drying is less than 4 %.Sahel et al., (2001) studied the locally available materials with high plasticity clayey soil and medium plasticity soil satisfies the all characteristics of soil liner. Composite soil samples made with naturally clay red mud and cement red mud used as additive regain the lower hydraulic conductivity and high compressive strength value. He concluded that this composite soil successfully used for stabilization of clay liner.
2.4 ACCEPTABLE ZONE914400778510After choosing the liner material the further step is to satisfy compaction control, because the compaction control and degree of saturation controls the hydraulic conductivity of the liner material. Figure.
2.3 Acceptable zone based on hydraulic conductivity (Kolawole et al., 2006)Kolawole et al., (2006) compaction proctor tests were conducted on three samples of Kaolanite type of clayey soil with four comp active efforts. They have investigated the acceptable zone (AZ) which was conclude based on the compaction plane meet the design objective for hydraulic conductivity , volumetric shrinkage , unconfined compressive strength as shown in figure.The optimum line identified lower boundary and zero air voids curve as the top limit for overall acceptable zone of kaolanite type of soil. The volume metric shrinkage strain was also identified as the second most important design parameter for kaolanite type of soil.
The shapes of the acceptable zones were affected by the fines contents of the soils.2.5 LITERATURE SUMMARYFrom the literature review it was found that natural clays usually satisfies the specification for liner material; however high plastic dirt’s are not ideal in light of the parching of breaks can prompt the spilling of leachate. Taking into account the water driven conductivity mud’s containing less sensitive mud minerals, for example, Kaolanite and illite were discovered to be unaffected by chemicals.After the review of available literatures the following conclusion can be given. Compaction method should be chosen in the laboratory is no adverse effect on soil liner, it always depend on molding water content to attain maximum dry density. It is not reliant on physical properties of soils.
Several studies are given to reduce hydraulic conductivity to reach; soils should be always compacted on wet side of optimum but not dry of optimum. Soil is mixed with assumed water content for attaining maximum dry density. With increase of dry density, hydraulic conductivity reduces. So, moisture content is always gives the relation between dry density and hydraulic conductivity. There is need of protecting soils after compaction. Naturally available clays satisfy the specification for liner material. Present study highly plastic clays are not preferable due to more shrinkage cracks.
After compaction of soils to react with chemicals produced from leach ate, chemicals present in dumping material may also studied. The hydraulic is more for landfills and reduce amount by using less reactive clays such as Kaolanite and illite type of clay less reactive with chemical solutions. The effect of mineral types and their concentration affect the cat ion exchange capacity of mineral used in landfill liner material. From the last few decades several studies have conducted to minimize the hydraulic conductivity. To accomplish this, soils ought to be on the ideal dampness substance, dry thickness and pressure driven conductivity relationships.
Size of the dirt is additionally vital to keep the stream of contaminants. Soils must be protected against desiccation of both prior and after compaction. Due to these, choose the Kaolanite clay type used for present work and Bentonite soil is mixer satisfies the hydraulic conductivity criterion for the liner material. According to the various investigators soils with following specifications would prove to be suitable for land fill liner construction. It is necessary to perform detailed laboratory test to fine the index properties of soil. Clod size my dependent on movement of leach ate trough soil. Mixer of soils such as percentage sand, silt and clay needed for present work.
Some field tests are also needed prior to construction. Compressive strength of soil is found at molding water content due to settlement of soil to long term. Due to the unconfined compressive strength test were conducted only on clayey soil to determine the shear strength of clayey soil.According to various investigators (Ex: Taha et al., 2004) soils with the following specifications (table 2.1) would prove to be suitable for liner construction: Table 2.1 Recommended specifications for the soils to be used as liner material. (Teha et al 2004) PARAMETER REQUIREMENTSPercentage fines ?50%Clay content 20-25%Liquid limit 25-30%Plasticity index 12-15%Cat ion exchange capacity ? 10 meq/100gCompressive strength of soil ?20 kPaIt is necessary to perform detailed laboratory tests and some field trial tests prior to liner construction to ensure that the requirements pertaining to permeability, compressive strength, leachate compatibility and shrinkage are met.
Chapter – 3METHODOLOGY3.1 GENERALTo fulfill the objectives, the knowledge of the tests to be conducted is essential. This chapter deals with the different type of tests are conducted on soil, the brief explanation on the different type of tests and methods to be adopted during the laboratory experiments.This chapter includes the soil characterization in which all the tests are performed for physical, chemical and geotechnical properties of soil are given in detailed.
All the tests are performed as per the IS specifications and based on code reference are mentioned this chapter.3.2 SOIL SAMPLING AND TESTINGIn the present work, clayey soil available locally was procured from Chenur, approximately 5 kilometers away from the K.
S.R.M College of Engineering. The soil was excavated by shovel at a depth of 0.6 m below the surface to avoid unwanted matter and roots.
It was placed in bags and transported to the geotechnical laboratory at K.S.R.M College of Engineering. The procured soil removed from the bags and air dried to the room temperature. Air dried soil was sieved through 20 mm IS sieve and stored in bags. Index properties of the soil were determined from the sieved sample.Bentonite clay is procured from the Chennai (Titanium Pigments Pvt.
Ltd ISO 9001 Company) and stored in the laboratory. Different types of bentonite were available such as sodium bentonite, calcium bentonite etc. sodium bentonite were extensively used for the preset study because of its lesser swelling capacity, higher cat ion exchangeable capacity and main property is low hydraulic conductivity to water.3.3 INDEX PROPERTIES OF THE SOILDuring this study all the tests are conducted based on Indian standard (part-1) 1987.3.
3.1 Natural moisture contentNatural moisture content is one of the basic tests used in the land fill design it can be determined from the oven dried method. It can be determined by oven-drying method and procedure given in IS 2720 (part 2)-1973 (reaffirmed 1997) has been followed.Take the clean container, dry it and weigh the empty weight of the container with lid taken as W1. Weigh the required quantity of the wet soil sample and placed in dried container, take the weight of the container with lid as W2. Remove the lid, placed in oven at a temperature of 1100 in 24 hours till the moisture escapes completely from the soil sample.
Weigh the dried sample with container as W3.The moisture content of the soil sample is determined from the formula,Moisture Content=mass of watermass of dry soilw=w2-w3w3-w1Where w1= weight of empty container with lidw2 = weight of wet soil sample with lidw3 = weight of dried soil with lid3.3.2 FIELD DENSITY OF IN-SITU SAMPLEField density of soil can be determined by core cutter method in actual field condition. In-situ field density determined as per the IS 2720(Part-29)-1975.Soil sample collected from the site used for present work, level the surface small area soil mass is to be tested.
Weigh the clean core cutter (W1). Press the cutter to its full depth with the help of steel rammer. Remove the soil around the cutter by the pick-axe.
Lift up the cutter. Trim the top and bottom surface of the cutter carefully. Clean the outside surface of the cutter. Weigh the core from the cutter and take representative sample in the container to determine the moisture content. Dry density of soil ?d= Bulk density1+moisture content 3.3.
3 SPECIFIC GRAVITY TESTSpecific gravity of soil is defined as the ratio of weight of soil solids to the weight of equal volume of water. Specific gravity test are conducted as per IS 2720-part 3, section 1-1980)If the distribution of the particle size classes and the Atterberg’s limits fall within the ranges given in table 2.1, the material is considered acceptable for compacted clay liner construction without the need for additional laboratory testing, The use of materials as defined above with the appropriate construction methodologies and equipment are expected to produce compacted clay liners with hydraulic conductivities of 1 x 10-9 meters/second or less winter 2007Weigh the clean dry density bottle with a cap accurate to 0.01 gm (W1). Sieve the sample passing through 2.0 mm IS sieve placed in density bottle and weigh as (W2). Fill the water in density bottle with its half of its height and mix it thoroughly with rod. Place the screw at top of bottle, weigh it as (W3).
Remove the contents from the density bottle and clean with distilled water and dry it and weigh as (W4).G= (W2-W1)GTW4-W1-(W3-W2) 3.3.4 PARTICLE SIZE DISTRIBUTIONIn laboratory, wet sieve analysis is conducted to determine the particle distribution.
Sieve analysis is conducted particle retained on 75 micron sieve and it is done based on the IS 2720(PART-4) 1975. Where the fines are defined as the soil fraction which passes through a No. 200 (75-?m) US standard sieve, and clay and sand are defined in the ASTM D2487-00 standard. Poorly graded materials with high silt content may not be considered acceptable. Such materials do not compact well and are highly erodible was considered from winter.2007. Arrange the set of sieve sizes 4.
75 mm, 2.0 mm, 1.00 mm, 600 micron, 425micronn, 300 micron, 150 micron and 75 micron. The decreasing order based on aperture size. Weigh about 1000gms of the given sample and pour it top of the sieve.lid is placed over it.
Shake the sieve for about 15 minutes holding the sieves inclined at an angle 150 to the vertical. The shaking is done in a circular motion. Determine the weight of the soil retained on each sieve and tabulate the results. Draw the grain size distribution curve with a logarithm of the aperture size on X-axis and percentage passing through the sieve on Y- axis. Determine the uniformity coefficient, coefficient curvature and particle size.Effective size of particle= D10Uniformity coefficientCU= D60D10Coefficient of curvatureCc= D302D60XD103.3.5 CONSISTENCY LIMITSThe consistency of the fine grained soil is the physical state in which it exists.
The water content at which the soil changes from one state to the other is known as consistency limits. The consistency limits are liquid limit, plastic limit and shrinkage limit. Generally consistency limits are used for classification of soil. An important step in design of compacted clay liners is to determine the range of acceptable water content for field compaction of the soil. If the soil is too dry during compaction, desired hydraulic conductivity would not be obtained and in case of soil being too wet, it will cause difficulty in compaction as well as may lead to desiccation cracks due to volumetric shrinkage. Thus, it is very important to specify the acceptable range of water contents within which the compacted soil will exhibit hydraulic conductivity ? 1 × 10-7 cm/s, volumetric shrinkage ? 4% and unconfined compressive strength ? 200 kPa was considered from the Allamprabhu et al.
, 2012Acceptable water content was considered from the previous investigator winter 2012Acceptable Atterberg’s Limits: • Plasticity Index (PI): PI ? 20% • Liquid Limit (LL): LL ? 30 % 220.127.116.11 LIQUID LIMITLiquid limit is defined as water content at which soil changes from the liquid state to plastic state. In the laboratory, liquid limit is determined by Casagrande apparatus and test is conducted as per IS: 2720-Part-5-1975.Water content refers to the amount of liquid or free water, contained in a given amount of material. Measuring water content can help determine whether a clay material needs preprocessing, such as moisture adjustment or soil amendments, to yield a specified density or hydraulic conductivity.
Compaction curves can be used to depict moisture and density relationships, using either ASTM D-698 or ASTM D-1557, the standard or modified Proctor test methods, depending on the compaction equipment used and the degree of firmness in the foundation materials.3 The critical relationship between clay soil moisture content and density is explained thoroughly in Chapter 2 of EPA’s 1993 technical guidance document.Weigh about 120gms of soil passing through 425 micron sieve and transfer into china dish. Mix the soil thoroughly with some distilled water in a china dish and form a uniform paste. Place a portion of the paste in the cup of the liquid limit device and smoothen the surface to a maximum depth of 10 mm with the help of the grooving tool. By grooving tool cut the paste, v-shaped gap, 2 mm wide at the bottom and 11 mm at the top and 8 mm deep will be formed.
Rotate the handle at a uniform rate about 2 revolutions per minute and count number revolutions required till the gap between two halves of the soil close through a distance of 10 mm. Take approximately 10gms of soil in a clean evaporation dish for moisture content determination. By changing the water content suitably, repeat the experiment at least 5 times set of values such that number of blows in between 10 and 40.Draw a graph between moisture content(natural scale) and number of blows (logarithmic scale)draw a straight line (mean) passing through as many points as possible read the water content corresponding to 25 blows which gives the liquid limit.Water contentW= Weight of waterWeight of dry soil18.104.22.168 PLASTIC LIMITPlastic limit defined as the water content at which the soil changes from plastic state to semi-solid state, in which soil tends to crumble when rolled into treads of 3 mm.
Plasticity characteristics describe a material’s ability to behave as a plastic or moldable material. Soils containing clay are generally categorized as plastic. Soils that do not contain clay are non-plastic and typically considered unsuitable materials for compacted clay liners, unless soil amendments such as bentonite clay are introduced. Plasticity characteristics are quantified by three parameters: liquid limit, plastic limit, and plasticity index. The liquid limit is defined as the minimum moisture content (in percent of oven-dried weight) at which a soil water mixture can flow.
The plastic limit is the minimum moisture content at which a soil can be molded. The plasticity index is defined as the liquid limit minus the plastic limit and defines the range of moisture content over which a soil exhibits plastic behavior. When soils with high plastic limits are too dry during placement, they tend to form clods, or hardened clumps, that are difficult to break down during compaction. As a result, preferential pathways can form around these clumps allowing leachate to flow through the material at a higher rate.
Soil plasticity indices typically range from 10 percent to 30 percent. Soils with a plasticity index greater than 30 percent are cohesive, sticky, and difficult to work with in the field. Common testing methods for plastic it characteristics include the methods specified in ASTM D-4318, also known as Atterberg’s limits tests.A minimum Plasticity Index of 10% is normally required/ stipulated as soils with a lower plasticity index are unlikely to achieve a sufficiently low permeability.
The authors would generally agree with this viewpoint though some of the low plasticity soils in the northwest (Mayo, Donegal, Sligo) and southwest (Kerry) have produced remolded permeability’s of 1 x 10-9 m/s or less.Take 40 to 50gms of soil in a china dish soil passing through 425 micron sieve; add sufficient quantity of water form as a paste. Make three or four convenient parts of the soil. Roll the soil on the glass plate with the hand until a thread of 3 mm is obtained. Put the crumbled piece of thread in an evaporating dish, and obtained the water content, which gives the plastic limit.3.3.5.
3 SHRINKAGE LIMITShrinkage limit of soil is defined as the maximum water content at which a reduction of water content will not cause any reduction in the volume of the soil mass. Procedure is given in IS: 2720 – Part – 6 – 1972.Liners are commonly composed of compacted natural inorganic clays or clayey soils. Clayey soils are used for constructing landfill liners because they have low hydraulic conductivity and can attenuate inorganic contaminants. If natural clay or clayey soils are not available, kaolinite or commercially available high-swelling clay (bentonite) can be mixed with local soils (Taha et al., 2004). In developing countries these materials have to be imported, if not available locally. This will significantly influence the cost of construction.
Take about 100gms of soil sample passing through 425 micron IS sieve. Place about 30gms of soil in Evaporating dish and mix it thoroughly with distilled water. Water added should be sufficient to fill the voids in the soil completely make the soil paste readily worked into the shrinkage dish without entrapping air bubbles. Clean the dish and determine the weight accurately. To determine its volume place the dish on the evaporating dish and fill the shrinkage dish with mercury till it over flows. Then remove the dish and wife off any mercury adhering to the outside of the shrinkage dish. Transfer the mercury into another evaporating dish and weigh it. Coat the inner side of the shrinkage dish with a thin layer of Vaseline.
In the centre of the dish, place the soil paste about one third portion of the volume of the dish, with of the spatula. Tap the dish gently on rubber sheet and allow the paste to flow towards the edges. Repeat the process till the dish is completely filled and excess soil over flow. Strike off the paste with the help of the straight edge.
Weigh the shrinkage dish and keep it open to air until the color of the pat turns from dark to light. Keep the dish in oven and dry pat to the constant weight at 1050c to 1100c and place dish in a desiccators and weigh it immediately. Keep the glass cup in a china dish. Fill the cup with over flowing with mercury. Remove the excess mercury by pressing the glass plate with the help of the three prongs firmly over the top of the cup.
Transfer the cup to another evaporating dish. Wipe off mercury adhering to the side of the cup. Place the oven dried soil pat on the surface of mercury in the cup and carefully force the pat on the surface of mercury in the cup and carefully force the pat into the mercury. Collecting the displaced mercury and weigh it. The volume of the dry soil pat is then determined by dividing this weight by unit weight of mercury.3.
4 HYDRAULIC CONDUCTIVITYSoils are generally permeable in nature due to the interconnected voids through which water can flow from higher energy point to lower energy points. The study of the flow of water through soil is important for estimating the quantity of underground seepage; yields of wells, stability analysis of earth Dams, settlement of Buildings etc.Compacted clay liners should be at least 2 feet thick and have a maximum hydraulic Conductivity of 1 x 10-7 cm/sec (4 x 10-8 in/sec). Hydraulic conductivity refers to the degree of ease with which a fluid can flow through a material. A low hydraulic conductivity will help minimize leachate migration out of a unit.
Designing a compacted clay liner with a thickness ranging from 2 to 5 feet will help ensure that the liner meets desired hydraulic conductivity standards and will also minimize leachate migration as a result of any cracks or imperfections present in the liner. Thicker compacted clay liners provide additional time to minimize leachate migrationprior to the clay becoming saturated. It is important to select compacted clay liner materials so that remolding and compacting of the materials will produce a low hydraulic conductivity. Factors influencing the hydraulic conductivity at a particular site include: the degree of compaction, compaction method, type of clay material used, soil moisture content, and density of the soil during liner construction. The hydraulic conductivity of a soil also depends on the viscosity and density of the fluid flowing through it. Consider measuring hydraulic conductivity using methods such as American Society of Testing and Materials (ASTM) D-5084. Was considered from Daniel, D.E.
, and R.M. Koerner.
1995A Falling head permeability test was conducted for determining hydraulic conductivity of fine grained soil and soil is compacted to standard proctor test to determine the maximum dry density into the permeability mould.3.5 COMPACTION CHARACTERSTICS OF SOILThe water content corresponding to maximum dry density is the optimum moisture content. If the compaction characteristics of soil increases the strength characteristics of soils, bearing capacity of foundations, decreases the undesirable settlement of structures and hydraulic conductivity of soil. By using standard proctor test, compaction characteristics of soil are determined using the procedure IS: 2720 – part – 7 – 1980/1987.Compaction is a process of reducing the void ratio of a soil by mechanical kneading. The soil is laid out in layers and then subjected to momentary application of load (via rolling, tamping or vibration).
The expulsion of air from the voids occurs without significant change in moisture content. The compaction process creates a denser soil mass and the effect of compaction can be quantitatively described in terms of dry density. Optimum moisture content (OMC) is obtained from compaction testing and this allows comparison with the natural value and provides a maximum dry density (MDD) was considered from Daniel, D.E., and R.M. Koerner.
1995The result shows that on increment of the ceramic tiles wastage in the dune sand, the maximum dry density (M.D.D.) of the mix composition increases. On the other hand, on increasing particle size of the ceramic tiles wastage the maximum dry density (M.D.D.
) increases. The optimum moisture content (O.M.
C.) also increased from 12 to 16 percent was considered from Dr. N. K. AmetaDetermine the weight of the empty mould (W1). Assemble the base and collar, Apply thin coat of oil to the inside. Weigh about 2.
5 kg of soil passing through 4.75 mm IS Sieve into a mixing pan. Add about sufficient water content of about 8 % and mix the soil thoroughly. Place the moist soil into the mould in three layers, each layer has 25 numbers of blows of rammer falling from 30.5 cm.
the blows are uniformly spread over the entire surface of the soil. Trim the soil with a straight edge and level the top of the mould. Remove the base from mould and weigh it (W2). Take representative soil from the mould for determination of water content. Increase the water content by increments of 2 %.Dry density of soil?d= (wet density)(1+water content)Wet density= Weight of wet soilvolume of the soil Water content= weight of waterweight of dry soil3.6 UNCONFINED COMPRESSION TESTUnconfined compressive strength of clayey soil, which can with stand without confinement (confining pressure is zero).
This test is conducted as per IS: 2720 – Part-10 – 1973.The results of compressive stress versus axial strain for various molding water content and the variation of unconfined compression test against molding water content are marine clay mixed with locally available clay respectively. The strength of compacted soil decreases with the increase of molding water content. Compacted soils used for waste contaminant liners must have adequate strength for stability, since waste materials exert compressive stress on liner system.
The compressive stress acting on the liner system depends on the height of the landfill and the unit weight of the waste. Thus to date, the minimum required strength for soil used for liners is not specified. Daniel and Wu (1993) reported that soil used for liner should have minimum unconfined compression strength of 200kPa. 20% marine clay satisfies the criteria for hydraulic conductivity. Hence the blend with 15% and 20% marine clay are considered for further investigation.
Allamprabhu. K, B. M. Sunil et al.,.Apply thin layer of oil inside the mould, collar and base plate. Take 2.5 kg of the clayey soil and mix it thoroughly with water content equal to OMC.
Compact the sample in the mould in three different layers with 25 blows on each layer by standard mould. Extract the sample from the mould and place it in the loading unit. Apply a load at a rate of 1.25 mm/min. Measure the load at regular intervals of strains in the specimen. Tabulate the reading and draw the graph between load and deformations.3.7 LEACHATE STUDIES Leachate is a substance which occurs from solid waste, permeates through solid waste layers in landfill site which consist of some soluble or suspended substances.
Leachate may be more hazardous and corrosive. The study of leachate is important which is no entering to our Environment. Study particular characteristics of leachate such as composition of waste materials, climate, weathering conditions, age, and Design, construction and operation process of Land fill. Leachate samples are collected from the waste disposal site, chemical Analysis is done for collected samples which give the type and amount of different chemical constituents.
3.8 HISTORYOF KADAPA LANDFILL SITEThe Dumping yard in Kadapa district near location Devuni kadapa bypass was spread over an area of approximately 10 Acres. The waste consists of different type of domestic waste; papers, plastics, cloths, cardboards, construction, hospital wastes etc. are dumped. The non-engineered open dump yard looks like a house type of waste. By using trucks different type of wastes are collected and bring the waste to this site and dumped at irregular fashion.Solid a waste is the unwanted and unless parts of animal and human activities which are basically solid.
They can be arising from agriculture, industrial and social activates. Solid waste is a consequence of life and its varies from one society to other.In early time human consumed at resources and he had not any problems but deposal of its waste.
Traditional compositing and producing the fertilizers were very typical solutions for most of the organic waste during that time; the disposal of the solid waste can be traced from that time when human started to make community, society and urban life. Municipal solid waste is one of major problem in urban centers. Kadapa city is one of the urban centers of Kadapa district Andhra Pradesh state in India is our study area. The main objective of the study sources of the solid waste generation and disposal. At present study gives the details of municipal solid waste generation, in the forms of residential, industrial, commercial, construction, demolish, and agriculture.
The solid waste collection in the forms of door to door, community bins and storage points. Different types of vehicles are used to transport the municipal solid waste. To study the implementation of disposal methods of solid waste in kadapa city. The population of Kadapa city is 3, 44,309 and area covered 164.08 Sq.Km. the average solid waste generation 206.21 Metric tons was taken from D.
Rama Bhupal Reddy et al.,The kadapa municipality population according to 2011 population 3,44,3.9 covered with an area 164.08 square kilometers. In our Kadapa municipal solid waste in collection of samples depends on utilities in the region.MSW collection points in kadapa are given by municipal authority given below.Table: 3.
1 Kadapa MSW detailsSl.No Collection points Number of collection points1 door to door 72.5262 collection points 1343 community bins 1004 storage bins 08The waste generated from around the area is 206.21 metric tons. There are three Disposal methods are used landfill, incineration and composting. In the solid waste disposal 54 % is disposed in landfill sites, 14 % by using incineration and remaining percentage is by composting method. Out of three methods of disposal techniques, landfill methods are considered because this site is placed away from the urban areas, water entrance is prohibited.
But due to rain water contaminated by these wastes and ground water contamination may occurs. So, we need to apply engineered waste dumps. Before dumping these wastes let us know the properties of contaminants produced and harmful ingredients present. Collect sample from these landfill site at five locations. In kadapa 8 landfill sites located at their respective positions. I selected one of these and properties of landfill design are carried out.
Chapter – 4EXPERIMENTAL RESULTS AND DISCUSSION4.1 GENERAL Compacted soil liners are widely used as engineered hydraulic barriers in waste-containment facilities. Compacted soil liners are composed of clayey materials that are placed and compacted in layers called lifts. The materials used to construct soil liners are locally available soils, very fine clayey soil, blended soil and other materials. Generally compacted soil liners are constructed from naturally available soils that contain a significant amount of fines (silt and clay). In present study an attempt has been made to utilize the locally available natural soil as compacted clay liner material.
It was understood that based on laboratory tests even though the clayey soil contain significant quantity of fines, the hydraulic conductivity requirement was not satisfied. The locally available clayey soil was blended with suitable soil in order to achieve a lower hydraulic conductivity (? 1×10-7 cm/s), which is a basic requirement for a liner material. Hence clayey soil and bentonite clay were mixed in different proportions and their results were analyzed to study the criteria fulfilled by the mixture as a liner material. Analysis and discussion of the test results have been done in this chapter. The experimental investigation of the soil includes its characterization which covers the preliminary investigation, physical, chemical and engineering properties of the soil. Liner material adsorbs various contaminants such as Potassium, Sodium, chloride and chromium were used as contaminants to study the adsorption characteristics of the clayey soil, bentonite clay and their blends. But, in the present study adsorption studies are not carried out.4.2 INDEX PROPERTIES OF TEST SOILS The tests were conducted according to IS specifications (Compendium of Indian standards on soil engineering; SP 36 (Part 1)-1987) for index properties of both clayey soil and bentonite clay and the results have been summarized and are given in Table 4.1.Table 4.1 Index properties of soilclayey Soil Bentonite clayParameters Trial-1 Trial-2 Trial-3 Avg. Trial-1 Trial-2 Trial-3 Avg.In-situ field density (kN/m3) 15.98 16.71 15.31 16.00 – – – -Field moisture content (%) 15.75 15.70 15.65 15.70 – – – Specific gravity 2.57 2.59 2.58 2.58 2.37 2.36 2.35 2.36Grain size analysisGravel (%) 2.00 2.50 3.00 2.50 – – – -Sand (%) 38.00 37.50 38.50 38.00 – – – -Silt (%) 46.00 42.00 45.50 44.50 20.00 20.50 19.50 20.00Clay (%) 14.00 18.00 13.00 15.00 80.00 79.50 80.50 80.00Liquid limit (%) 45.77 45.12 45.61 45.50 295.62 300.53 294.58 296.91Plastic limit (%) 32.33 32.00 31.67 32.00 44.33 45.06 44.33 44.57Shrinkage limit (%) 26.12 27.54 27.34 27.00 10.84 10.60 10.04 10.49Volumetric shrinkage (%) 32.40 29.90 30.70 31.00 462.64 475.18 454.80 464.21Plasticity index (%) 13.12 13.44 13.94 13.50 251.29 255.47 250.25 252.34IS Classification MI MI MI MI CH CH CH CHActivity 0.94 0.75 1.02 0.9 3.14 3.21 3.11 3.15Figure 4.1 Particle size distribution curves of clayey soil and bentonite clayThe particle size analysis (Fig. 4.1) for clayey soil shows that it contains 15% of clay size fraction (? 0.002mm), 44.5% of silt and approximately 38% of sand. Atterberg’s limits of soil i.e. the liquid limit are 45.5%, plastic limit is 32.0% and plasticity index is 13.5%. On the basis of this data the soil can be classified according to IS classification as inorganic silt with medium compressibility (MI). Medium compressibility inorganic silt (MI) requires precise moisture control to achieve the desired compaction and may require a rubber-tired roller or sheep-foot roller. The natural kneading action of the roller feet results in large shear strain within the soil structure. Shear strain cause realignment on the molecular level of the clay structure. The realignment yields a dispersed structure, which gave many beneficial qualities with respect to a compacted soil liner. Dispersed structure of clay layer is able to obtain a lower hydraulic conductivity value that could be obtained at a similar density with static compaction.The particle size analysis (Fig. 4.1) of bentonite clay shows that the soil contains 80% of clay fraction (? 0.002mm) and 20% of silt. Atterberg’s limits of soil tested shows that the liquid limit is 296.91%, plastic limit is 44.57% and therefore plasticity index is 252.34%. On the basis of this data the soil can be classified according to IS soil classification as inorganic clay with high compressibility (CH), Inorganic clay with high plasticity (CH) is typical material for landfill liners (Taha, 2004). 4.3 COMPACTION BEHAVIOUR OF SOIL 9334501147445Compaction of soil results in a homogeneous mass that is free of large, continuous inter-clod voids; increases its density and strength, and reduces its hydraulic conductivity and future settlement. Hydraulic conductivity is the key design parameter when evaluating the acceptability of a barrier material. Low hydraulicFigure 4.2 Compaction characteristics of clayey soil and bentonite clay Conductivity is achieved when the soil is compacted at high dry density and water content on wet side of optimum. Thus compaction tests are performed to determine the maximum dry density and corresponding optimum water content for a soil under specific comp active effort. The results of compaction tests on clayey soil and bentonite are shown graphically in Fig. 4.2. The maximum dry density and the optimum water content obtained from these tests are shown in Table.4.2Table 4.2 Maximum dry density and corresponding optimum water contentS.No Type of soil Compaction test Optimum water content % Maximum dry density ?dmin (kN/m3)Trial-1 Trial-2 Trial-3 Avg. Trial-1 Trial-2 Trial-3 Avg.1 clayey soil Standard proctor 19.50 20.34 18.66 19.50 16.60 16.26 16.64 16.502 Bentonite clay Standard proctor 30.00 35.00 33.00 32.67 13.40 13.00 13.00 13.104.4 HYDRAULIC CONDUCTIVITY OF SOILS The hydraulic conductivity is the most important key parameter for liners and covers materials. The results of the hydraulic conductivity tests for the parent soil (clayey) and the bentonite clay (blend) are shown in Table 4.3Figure. 4.3 Hydraulic conductivity with % bentonite addedTable 4.3 Hydraulic conductivity of soilsSl.No Type of soilCompaction testHydraulic conductivity (cm/s)-4% ( 0) % 2% 4%1 clayey soil Standard Proctor 7.210-6 2.410-6 3.210-7 4.810-62 Bentonite Standard Proctor – Impermeable – -. The criterion for choosing clay as liner materials and is primarily based on the hydraulic conductivity achievable under field conditions. Clayey soil that can be Compacted to obtain a low hydraulic conductivity (1×10-7cm/s or less), when soil compacted to maximum dry density at optimum moister content, the proctor density obtained is always 90-95%. Since the hydraulic conductivity obtained from the experiments is more of clayey soil. The required value of 1×10-7cm/s always less than this value, due to these decided to clayey soil is mixed with bentonite clay to obtain the required value. 4.5 CLAYEY SOIL BLENDED WITH BENTONITE CLAYClayey soil was blended with 9 % and 15% of bentonite clay. The geotechnical properties, compaction curves and the variation in hydraulic conductivity with moisture content were observed in the laboratory. The results of compaction and hydraulic conductivity with varying percentage of bentonite clay added to clayey soil are tabulated in Table 4.4.Figure 4.3 shows the variation of hydraulic conductivity with respect to moisture content. From the graph it is evident that clayey soil mixed with 9% bentonite Quarry dust and clay satisfies the criteria for hydraulic conductivity. Hence the blend with 9% and 15% bentonite clay were considered for further investigation.Table 4.4 Variation of hydraulic conductivity of blended soilsPercentage of bentonite clay added Dry density (kN/m3) Optimum moisture content Permeability in (cm/s)3% 17.52 16.32% 2.54×10-76% 17.24 17.82% 3.25×10-79% 16.95 18.50% 3.51×10-712% 16.43 20.33% 8.51×10-815% 16.40 20.50% 5.83 x10-8 4.5.1 CLAY MIXED WITH 9% BENTONITE CLAY 1028700803910As the required hydraulic conductivity could not be achieved from clayey soil alone, it was blended with 9% bentonite clay and tested the blended soil according to IS specification.Figure 4.4 Standard compaction curve for clayey soil blended with 9% bentonite clayFig. 4.4 shows the compaction test results for 9% blend of bentonite clay. Based on this, the hydraulic conductivity tests were conducted on dry and wet side of the optimum water content. The hydraulic conductivity changes with the change of molding water content. Soils compacted at dry side of optimum water content tend tohave relatively high hydraulic conductivity, whereas soils compacted at wet optimum water content tend to have lower hydraulic conductivity. The minimum hydraulic conductivity at corresponding water content and dry density is presented in Table 4.5. From Fig. 4.5 it is evident that 9% bentonite clay blend satisfies the hydraulic conductivity criteria at initial saturation of 89% at optimum moisture content. Increasing water content generally results in an increased ability to break down clay aggregates and to eliminate inter aggregate pores.Table 4.5 Variation of hydraulic conductivity with molding water content of clayey soil blended with 9% bentonite clayDry density (kN/m3) Molding water content Permeability (cm/s)15.8 16.33 % 6.56 x10-716.2 18.33 % 3.49 x 10-716.43(MDD) 20.33 %(OMC) 8.51 x 10-816.2 22.33 % 5.18 x 10-815.9 24.33 % 6.19 x 10-22.214.171.124UNCONFINED COMPRESSIVE STRENGTH (UCS) The results obtained from the laboratory test, at molding water content i.e. 2%, 4% etc. plot graph between strength vs. strain shown in fig 4.6 and the variation of unconfined compression test against molding water content at 5% bentonite mix is shown in figure 4.8. The compressive strength of compacted soil always decreases with an increase in moisture content.Figure. 4.5 Variation of unconfined compressive strength with axial strain (clayey soil + +10% Quarry Dust + 9% bentonite clay)Figure.4.6 unconfined compressive strengthThe soil used for liner material to arrest the flow of contaminants, liner have adequate strength to with loads acting on material by waste, the compressive stresses acting on the liner material to resist these stresses, stabiles the soil at field condition. The compressive stress acting on the liner system is always two parameters such as the height of the landfill and the unit weight of the waste. But up to date, the strength required to retain the liner material is not specified. some of the literatures given minimum strength, Daniel and Wu (1993) reported based on his experiments, present study the minimum strength required for liner system should have unconfined compression strength of 200kPa (0.2N/mm2).In the present study, test results on blended soils show that the soil possesses higher strength is always more than recommended minimum strength of 200 kPa for molding water content of 20.33% and 22.3%.Different thicknesses are used for liner material; it is always less than 1 and compacted to a maximum dry density achieved in the field at molding water content. Peak point obtained from graph is alarm to strength. Strength obtained from this mixer is not a maximum value it is always increase by increasing % of bentonite. At particular mix, the strength goes down at particular water content.923925-156210Figure. 4.7 Variation of unconfined compressive strength with molding water content (clayey soil+10% Quarry Dust+ 9% bentonite clay)4.5.2 CLAY MIXED 15% BENTONITE CLAY AND 10% QUARRY DUST1000125413385The percentage of bentonite – clay was increased from 9% to 15% to achieve better. Figure 4.8 Standard compaction curve of clayey soil blended with 15% bentonite clayThe results obtained from standard compaction tests for clayey soil mixed by with 15% of bentonite clay are shown in Fig. 4.8. Based on these tests results the hydraulic conductivity tests were conducted on dry moisture content and wet of moisture content. It was found that the mixed soil satisfies the criteria for hydraulic conductivity at initial saturation of 86% at optimum moisture content.Figure 4.9 Variation of hydraulic conductivity with molding water content (clayey soil+ 10% Quarry Dust +15% bentonite clayTable 4.6 Variation of hydraulic conductivity with molding water content of clayey soil blended with 15% bentonite, 10% Quarry Dust ; clayDry density (kN/m3) Molding water content Permeability (cm/s) 16.1 16.5 % 10-7 16.25 18.5 % 2.12 10-7 16.4(MDD) 20.5 %(OMC) 5.83 10-8 16.0 22.5 % 10-8 15.4 24.5 % 5.20 10-8 126.96.36.199 UNCONFINED COMPRESSIVE STRENGTH Figure. 4.10 Variation of unconfined compressive strength with axial strain (clayey soil+10% Quarry Dust+ 15% bentonite clay)Figure 4.11 Variation of unconfined compressive strength with molding water content (clayey soil+ 15% bentonite +10% Quarry Dust)The results obtained from the unconfined compression test for different molding water content at different percentage are shown in Fig. 4.10 and variation of unconfined compression test with respect to molding content for clay soil blended with 15% bentonite clay are shown in Fig. 4.11.The strength of the compacted soil decreases with the increase in the molding water content. Test results for than the recommended minimum strength of 200kPa at 20.5% and 22.5% water content.4.5.3INDEX PROPERTIES OF BLENDED SOILMany researchers have proposed the desirable index properties for a liner material based on the experience and performance study of the landfill liner materials; hence in this study an effort was made to bring out the index properties of liner material to assess its behavior. Table 4.8 lists the index properties of clayey soil blended with 9% and 15% bentonite clay.A marginal increase in plasticity index and percent fines was observed compared to that of natural clayey soil. The plasticity index increased by 7.23% and 10.24% for clayey soils blended with 9% and 15% bentonite clay respectively, and percentage of fines increased by 1.02 and 1.62 in both the cases.A marginal increase in plasticity index and percent fines was observed compared to that of natural clayey soil. The plasticity index increased by 7.23% and 10.24% for clayey soils blended with 9% and 15% bentonite clay respectively, and percentage of fines increased by 1.02 and 1.62 in both the cases.The plasticity index and the percentage fines are the most important criteria for selection of soil for liner system construction. They are the key property in achieving low hydraulic conductivity. Literature suggests that plasticity index greater than 10% have been used successfully to construct soil liners with extremely low in-situ hydraulic conductivity and, Daniel (1991) states that if the plasticity index is less than 35, low shrinkage can be expected. Soils with inadequate fines typically have too little silt and clay sized particles to produce high hydraulic conductivity. Hence a minimum of 50% fines is usually recommended for achieving low hydraulic conductivity. In addition shrinkage potential of a soil is directly related to its shrinkage limit. The shrinkage limit of the clayey soil blended with 9% and 15% bentonite clay obtained from laboratory tests are 18.64% and 18.42% respectively. Table 4.7 Index properties of blended soil.clayey soil+9% bentonite clay clayeysoil+15%bentonite clayParameters Trial-1 Trial-2 Trial-3 Avg. Trial-1 Trial-2 Trial-3 Avg.Specific gravity 2.57 2.56 2.56 2.56 2.53 2.54 2.54 2.54Grain size analysisGravel (%) 1.55 1.77 1.67 1.66 1.96 1.69 1.84 1.83Sand ( %) 36.84 37.68 38.95 37.82 36.42 37.01 37.70 37.04Silt ( %) 42.61 41.55 41.38 41.85 39.62 40.30 39.46 39.79Clay (%) 19.00 19.00 18.00 18.67 22.00 21.00 21.00 21.33Liquid limit (%) 48.11 47.72 46.97 47.60 51.55 50.43 50.47 50.82Plastic limit (%) 26.79 27.21 26.60 26.87 27.20 26.71 27.31 27.07Shrinkage limit (%) 18.91 18.40 18.61 18.64 19.80 17.32 18.14 18.42Volumetric shrinkage (%) 50.16 49.37 49.46 49.66 54.44 58.51 55.29 56.08Plasticity index (%) 21.32 20.51 20.37 20.73 24.35 23.72 23.16 23.74IS Classification CI CI CI CI CH CH CH CHActivity 1.12 1.08 1.13 1.11 1.11 1.13 1.1 1.11Soils with high shrinkage limit will show little volume change potential. Shrinkage limit obtained from blended soil sample is close to the range of water content required to achieve the hydraulic conductivity of 1 10-7 cm/s, which signifies that the blended soil sample is less susceptible to volume change. The plasticity index of the blended soils is greater than 15% which indicates that the soil is workable. Thus the blended soil would be preferable as the liner material. The Activity (Ip / % clay fraction) of the blended soil is found out to be 1.11 for both 9% and 15% blend. According to Skempton’s classification it is classified as normal clay. Activity is an index of the surface activity of the clay fraction. Soils with higher activity are likely to consist of smaller particles having larger specific surface area and thicker electrical double layer. Therefore hydraulic conductivity generally decreases with increasing activity. However soils with high activity are more readily affected by pollutant if they are used in containment structures hence less active clayey soils are preferred for landfill liners (Rowe et. al, 1995). Compacted soil liners are subjected to frequent desiccation due to evaporate water losses. Desiccation leads to development of shrinkage cracks. Cracks provide pathways for moisture migration into the landfill cell, which increases the generation of waste leach ate, and ultimately increases the potential for soil and ground water contamination, thus, the soil liner significantly losses its effectiveness as an impermeable barrier. Literature suggests that a soil liner does not exhibit desiccation cracking if the volume change upon drying of the compacted soil used as the liner is less than 4% (Daniel et. al., 1990 and Wu et. al., 1993). Test results indicate that the optimum moisture content is lessthan the shrinkage limit hence volumetric shrinkage does not play any role in deciding the sacceptable zone. Chapter – 5CONCLUSION5.1 SUMMARYClayey soil satisfies the basic properties for liners except the hydraulic conductivity parameter, which is considered to be the most important property of liner material. The index properties of clayey soil are inorganic silt and moderately plasticity. Clayey soil have plasticity index and shrinkage limit are 13.5% and 27 % respectively; thus from experimental values clayey exhibit Low shrinkage. The clayey soil having normal activity (Activity = 0.9), which indicates that the soil would be less affected by contaminants or Leachate. The clayey soil was mixed with different proportions of Bentonite clay and a suitable mix was found at which the desired permeability was achieved. It was found to be addition of 15 % of bentonite clay, clayey soil behaved as a good barrier. Hence further studies were carried out on the clayey soil blended with 15 % bentonite clay, to assess the other properties such as volumetric shrinkage, unconfined compression strength, cat ion exchange capacity etc.To determine the suitability of the blended soil as a liner material. Based on the studies land fill Design were carried out.5.2 CONCLUSIONSAn extensive Laboratory testing was carried out on clayey soil for the purpose of evaluating its potential use as a liner material. Based on the experimental investigation the following are some of the important conclusions.Hydraulic conductivity of clayey soil was found to be 2.4 x 10-6 cm/sec which is not acceptable as per the relevant standards. Hence clayey soil was mixed with bentonite clay.Based on the Hydraulic conductivity (1×10-7 cm/sec), the clayey soil mixed with 15% bentonite clay satisfies the criteria for hydraulic conductivity. To achieve the desired hydraulic conductivity, degree of saturation shall be maintained 95% to 88%. Also hen the saturation level is 95 % to 88 % the observed maximum dry density and OMC values were in range (i.e. ? d max = 16. 4 KN/m2 to15.4 KN/m2 and OMC = 20.5 % to 22.5 % )When mixed soil is compacted to desired maximum dry density (i.e. ? d max = 16. 4 KN/m2 to15.4 KN/m2) at acceptable water content.(i.e. 20.5 % to 22.5%) its compressive strength was 280.1 KPa and 227.51 KPa (>200 KPa) with minimum shrinkage potential. Based on the index properties and chemical properties of the blended soils, it can be concluded that the clayey soil blended with 15% bentonite clay proves to be a better liner material compared to the clayey soil blended with 9% bentonite clay. REFERENCEGrim, R.E.: 1968, Clay mineralogy, 2nd edi. McGraw-Hill, New York.Mitchel, j.k.: 1993, Fundamentals of soil behavior, 2nd ed., Wiley, New York.Shang, J.Q. and Rowe, R.K.:2003, detecting landfill leachate contamination using soil electrical properties, practice periodical of Hazardous, Toxics, and Radioactive waste Management.Mersi, G. and Olson, R.F.:1971, Mechanics controlling the permeability of clays, clays and clay mineralogy.Ziaie -Moayed, R. and Naeini, S.A.:2009, Effect of plasticity index and reinforcement on the CBR value of soft clay, international general on civil engineering. 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