IGC. 50 th. 50 th INDIAN GEOTECHNICAL CONFERENCE STUDY OF BLACK COTTON SOIL AND LOCAL CLAY SOIL FOR SUB-GRADE CHARACTERISTIC

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1 5 th 5 th INDIAN GEOTECHNICAL CONFERENCE 17 th 19 th DECEMBER 215, Pune, Maharashtra, India STUDY OF BLACK COTTON SOIL AND LOCAL CLAY SOIL FOR SUB-GRADE CHARACTERISTIC Chayan Gupta 1, R.K. Sharma 2 ABSTRACT As the development of industries increase, produced quantity of waste materials also increases. As resulted, the demand for disposing these industries wastes is increasing. The land disposal method for disposing these industries waste materials is one of the common conventional method which is requires a large area of land, but on the basis of present scenario due to scarcity of land in India but by default these waste materials generate a big problem to the humans being surrounding that area as well as act as a pollutant and contaminant the ground water so basically affect the ecological system of the environment. It shows that there is urgent need for exploring the alternative of disposal of these materials hence the necessity of area for arranging these materials is additionally a troublesome undertaking. From geotechnical point of view, these waste materials having effective characteristics required for a good soil stabilization admixture. These waste materials used as a soil stabilizing agents in soil modification approaches. The utilization of these waste materials as a constructional material, passage quantifiable advantage on the economy as well as the strength, when used as construction materials in infrastructure projects like pavements, hydraulics structures, clay liners etc and makes the environment eco-friendly. This paper shows the comparative study for geotechnical characteristics of black cotton as well as locally available clayey soil blended with river ganga sand and fly ash with an approach is made towards the way of improvement in the various geotechnical properties of black cotton soil as well as clayey soil such as compaction properties, hydraulic conductivity characteristics and sub grade characteristics by blending them with waste materials such as river sand and fly ash. Hence from these approaches the impacting effect of waste materials on the environment is reduces due to optimum utilization of these waste materials in the improvement in various geotechnical properties of both soils. From geotechnical point of view both soils having an impervious nature with poor geotechnical sub grade characteristics which creates the considerable time taken in consolidation i.e. pore water dissipation. In this study, the optimum mixtures of black cotton and clayey soil blended sand and fly ash were identified by compaction tests and economical use. The optimum mix of black cotton and clayey soil with sand was 7:3. The 15 % and 1 % of fly ash was obtained as optimum for sand blended black cotton soil as well as clayey soil optimum mixture. It was also seen that the addition of optimum percentage of fly ash increased the sub grade characteristic i.e. CBR value of both black cotton and clayey soil mixture with sand. The soaked CBR values of black cotton soil and local soil blended with waste materials were increased from 2.69 to 5.97 i.e. up to % increases and from 2.39 to 5.12 i.e % increases respectively similarly the unsoaked CBR values of black cotton soil and local soil were increased from 7.34 to i.e. up to % increases and from 5.61 to 8.73 i.e % increases respectively, Also the permeability values of black cotton soil and local soil after stabilization were increased from cm/sec to cm/sec and cm/sec to cm/sec respectively which shows that the stabilized soil taken less time for consolidation. The cost analysis of

2 Chayan Gupta 1, R.K. Sharma 2 this studies in pavement application were also concluded on the basis of local schedule of rate and it is resulted that these study will implies the good reduction factor in cost of construction of pavements. Keywords: Black cotton soil, Local Clay, Sand, Fly Ash, Compaction Characteristics, California Bearing Ratio, Permeability and Cost Analysis. 1 Gupta Chayan, Research Scholar, Civil Engineering Department, IIT(BHU), Varanasi, India, chayanbagli@gmail.com 1 Sharma R.K, Professor, Civil Engineering Department, NITH, Hamirpur, India, rksnthp61@gmail.com

3 5 th 5 th INDIAN GEOTECHNICAL CONFERENCE 17 th 19 th DECEMBER 215, Pune, Maharashtra, India STUDY OF BLACK COTTON SOIL AND LOCAL CLAY SOIL FOR SUB- GRADE CHARACTERISTIC Chayan Gupta, Research scholar, IIT (BHU), Varanasi, India,chayanbagli@gmail.com Ravi Kumar Sharma, Professor, NITH, Hamirpur, India, rksnthp61@gmail.com ABSTRACT: The land disposal method for disposing these industries waste materials is one of the common conventional method which is requires a large area of land, but on the basis of present scenario due to scarcity of land in India but by default these waste materials generate a big problem to the humans being surrounding that area as well as act as a pollutant and contaminant the ground water so basically affect the ecological system of the environment. It shows that there is urgent need for exploring the alternative of disposal of these materials hence the necessity of area for arranging these materials is additionally a troublesome undertaking. From geotechnical point of view, these waste materials having effective characteristics required for a good soil stabilization admixture. In this study, the optimum mixtures of black cotton and clayey soil blended sand and fly ash were identified by compaction tests and economical use. The optimum mix of black cotton and clayey soil with sand was 7:3. The 15 % and 1 % of fly ash was obtained as optimum for sand blended black cotton soil as well as clayey soil optimum mixture. It was also seen that the addition of optimum percentage of fly ash increased the sub grade characteristic i.e. CBR value of both black cotton and clayey soil mixture with sand. INTRODUCTION Soil stabilization is defined as a technique in which interchanging or altering finer particles of soil with coarser particles takes place to enhance the required engineering properties of soil so that mixture of soil contain both cohesion and friction factors as well as high load carrying capacity when properly mixed, placed and compacted at site. The stabilized soil has the beneficial properties which depend upon the applications where soil is being used. Basically stabilized soil reduces the pavement thickness, eliminates the handling and hauling quantity of excavation material, gives higher resistance value, reduce the swelling characteristics and plasticity of clayey soil. The black cotton soil is also known as expansive soil. In India it is found in major parts of Madhya Pradesh and Andhra Pradesh. The Expansive soil covers about 2-25 % land area of India. Due to the cyclic swelling and shrinking behavior of black cotton soil, many problems are created during construction. Generally when the moisture content comes in the contact of Expansive soil its causes swelling and when moisture content reduce in the soil its causes shrinking. The estimated results shows that the expansive soil causes the structural damage about $1 Millions in USA, 15 UK, and many billions pounds in worldwide annually[1]. There are many studies available in the literature regarding expansive soil [2-8] and many more. Similarly there are several works reported by other researchers for the utilization of fly ash [9-15] In present study, black cotton soil and clayey soil are stabilized with the help of Ganga sand and fly ash and were checked for economical uses as subgrade in pavements. TESTING METHODOLOGY All the laboratory tests were conducted in accordance with ASTM standards and Indian standard as shown in Table 1. [15-22] Table 1 List of test standards used Laboratory Test ASTM standards Hydrometer analysis ASTM D422-63

4 Chayan Gupta 1, R.K. Sharma 2 Standard Proctor test ASTM D698-7e1 Specific gravity ASTM D854-1 Soil Classification ASTM D Consistency limit tests ASTM D Particle size distribution ASTM D Falling head permeability ASTM D584-3 Consolidation test ASTM D California bearing ratio ASTM D Swell pressure ASTM D Differential free swell IS 2911 part III-198 index EXPERIMENTAL PROGRAM Materials The materials used in this investigation are black cotton soil, locally available clayey soil, river sand and fly ash. The Black cotton soil, clayey soil, sand and fly ash are collected from Dist. Dewas, Madhya- Pradesh, BHU campus, river Ganga and local thermal power plant respectively. The grain size distributions of these materials are given in Fig. 1. Based on the percentage of finer particles present the black cotton soil and clayey soil are classified as CH and CL (ASTM classification). The geotechnical properties of these materials are given in Table 2. The chemical composition of fly ash is given in Table 3. Table 2: Physical properties of Black cotton Soil,, Sand and Fly Ash Properties Black Soil Clay Sand Fly Ash Specific Gravity Maximum Dry Density (g/cc) Optimum Moisture Content (%) ASTM Classification CH CL SP F class Differential Free Swell Index (%) Liquid Limit (%) Plastic Limit (%) Plasticity Index (%) Uniformity Coefficient, Cu Coefficient Of Curvature, Cc Soaked CBR (%) Table 3: Chemical composition of Fly Ash Chemical Composition Proportion (%) Silica (Sio2) 55.9 Alumina (Al2o3) Calcium oxide (Cao) 3.67 Iron oxide (Fe2O3) 6.12 Potassium Oxide (K2O).89 Sulphur (SO3).41 Magnesium Oxide (Mgo).66 Loss on ignition 5.68 Method of Testing All the laboratory tests were conducted in accordance with various ASTM standards. Compaction tests were conducted on black cotton soil and clayey soil with varying percentages of sand from 1% to 4% and optimum mixes were obtained. %Finer Partical size (mm) Black cotton clay sand fly ash marble dust Fig.1: Particle size distribution of black cotton soil, clayey soil, sand and fly ash After obtaining optimum mix proportion varying percentages of fly ash is added with soil-sand mix from 5 to 25% in increments of 5%. For conducting California bearing ratio tests the size of samples were of 15 mm diameter and 125 mm height. Soaked CBR tests were conducted in standard mold

5 5 th 5 th INDIAN GEOTECHNICAL CONFERENCE 17 th 19 th DECEMBER 215, Pune, Maharashtra, India for samples compacted statically at maximum dry MDD and OMC. Surcharge weight of 5N was used during the testing. A metal penetration plunger of diameter 5 mm and 1 mm long was used to penetrate the samples at the rate of 1.25 mm/minute using computerized CBR testing machine. RESULTS AND DISCUSSIONS Compaction Tests The maximum dry density and optimum water content for various percentages of black cotton soil and clayey soil with sand and fly ash is given in Table 4. The mixing of black cotton soil with 1, 2, 3 and 4 % of sand shows the increase of MDD and reduction of OMC. The increases in MDD is due to the void spaces between the sand particles are occupied by the black cotton soil particles and reduction of OMC is due to lower quantity of water required to lubricate the sand particles which are coarser compared with clay particles. The mixing of BCS- Sand composite with 5, 1, 15 and 2 % of fly ash content shows the reduction of MDD and increase of OMC even the maximum dry density achieved after the addition of fly ash is lesser compared with black cotton soil- sand mix. This reduction of MDD is due to the reason that the clay particles can fill most of the voids in the sand when mixed in the ratio of 7:3 and Increase in OMC is due to due to the fact that the optimum moisture content of fly ash is higher (since the fly ash particles are much finer and rounded in shape) as compared to that of soil and sand. Table 4 MDDS and OMC For Various Percentages of Black Cotton Soil and Clayey Soil blended with Sand and Fly Ash Materials Composites Proportions (%) Maximum dry density (gm/cc) Black cotton soil Black cotton soil Black cotton soil: waste sand Black cotton soil: waste sand: fly ash 9: : : : :28.5: :27: :25.5: :24: clay clay: waste sand 9: : : : clay: waste sand: fly ash 63:27: :25.5: :24: :22.25: Optimum water content (%) The mixture of clayey soil with 1, 2, 3 and 4 % of sand shows the increase of MDD and decrease of OMC up to 3 % of sand and at 4 % of sand, the clayey soil shows the opposite trend. This occurs due to the reason that the void spaces between the sand particles are occupied by the clay particles are occupied by the clay particles up to a certain percentage thereafter the extra sand content tends to

6 Chayan Gupta 1, R.K. Sharma 2 reduce the density. The mixing of this clay-sand composite with fly ash decreases the MDD. This is because the fly ash is a light weight material as compared to clay and sand. Variation of MDD and OMC of optimum mixture of black cotton soil and local clay blended with sand and fly ash is shown by Fig. 2 and Fig.3. Maximum Dry Density (g/cc) BCS: 1 BCS:S AND:: 7:3 BCS:S AND:F A::59.5 :25.5:1 5 MDD OMC Fig. 2: Variation of MDD and OMC of optimum mixture of black cotton soil with sand and fly ash. Maximum Dry Density (g/cc) CLAY:1 Black cotton Local Clay CLAY:S AND::7 :3 CLAY:S AND:F A::63: 27:1 MDD OMC Fig. 3: Variation of MDD and OMC of optimum mixture of local clay blended with sand and fly ash California Bearing Ratio Tests The results of California bearing ratio (CBR) tests on black cotton soil and clayey soil treated with sand and fly ash are shown in Fig. 4. It is observed that soaked CBR value of black cotton soil and clayey soil increased with addition of sand and fly ash. The Optimum Water Content % Optimum Water Content % value of soaked CBR of black cotton and clayey soil increases from 2.69 % to 5.97 % and 2.39% to 5.12 % respectively and similarly unsoaked CBR value of black cotton and clayey soil increases from 7.34 % to % and 5.61% to 8.75 % respectively. CBR Value Black Cotton BCS+SA BCS+SA BCS ND ND+FA Soaked Unsoaked CLAY+S CLAY+S CLAY AND AND+FA Soaked CBR Value Unsoaked Fig. 4- Variation of soaked and unsoaked CBR value with optimum mixes of black cotton soil and local clay blended with sand and fly ash The improvement in CBR value may be attributed to better compaction and packing of the mix particles with addition of sand and fly ash. The California bearing ratio provides a basis of designing the sub-grades of flexible pavements. Usually, a value of CBR more than 5. is considered to be satisfactory for the design of flexible

7 5 th 5 th INDIAN GEOTECHNICAL CONFERENCE 17 th 19 th DECEMBER 215, Pune, Maharashtra, India pavements with traffic intensity of 1 to 1 million standard axles (msa). Thus, the black cotton and clayey soil blended with sand fly ash and marble dust can be effectively used in the construction of sub-grades of roads with low traffic volume. Falling Head Permeability Test Results The permeability or hydraulic conductivity of soil is the most important parameter in designing of hydraulic structure like dams, bridges, embankment, retaining walls etc. Permeability (cm/sec) 1.2E-5 1.E-5 8.E-6 6.E-6 4.E-6 2.E-6 Black Cotton The utilization of river sand and fly ash blended with black cotton soil and local clayey soil influences the hydraulic conductivity of mix at a lager extent. As per ASTM D584-3 the falling head permeability test was conducted in laboratory. A stand pipe of known cross sectional area is fitted over the permeameter and water is allowed to run down. After achieving the steady flow observations are taken in the form of head and time interval so as to calculate the coefficient of permeability by the formula: =. Where, a=cross-sectional area of stand pipe t = time required for head drop h1=initial head h2= final head L= length of soil column A= area of soil column The above results show the permeability value of black cotton soil was (cm/sec). After soil stabilization, the final optimum mix obtained by blending of waste materials in the black cotton soil possess higher permeability value i.e (cm/sec).the comparative results show the impact of these waste materials on the hydraulic conductivity both of soil as shown in Fig.5. Permeability (cm/sec).e+ BCS BCS+SA ND BCS+SA ND+FA Composition 1.12E E E-6 4.5E-7 4.E-7 3.5E-7 3.E-7 2.5E-7 2.E-7 1.5E-7 1.E-7 5.E-8.E+ Clay Clay +SAN D Clay +SAN D +FA Composition 1.45E-7 3.7E E-7 Fig. 5: Variation of coefficient of permeability for optimum mixes of black cotton soil and local clay blended with sand and fly ash soil blended with sand and fly ash DESIGN AND COST ANALYSIS OF FLEXIBLE PAVEMENT According to IRC: (Guide lines for the design of Flexible Pavements), a flexible pavement has to be designed for cumulative traffic of 1, 5 and

8 5 th 5 th INDIAN GEOTECHNICAL CONFERENCE 17 th 19 th DECEMBER 215, Pune, Maharashtra, India Pavement thickness (mm) Black Cotton Cumulative traffic (msa) Unstabilized soil stablized soil Pavement thickness (mm) Cumulative traffic (msa) Unstabilized soil stablized soil Percentage savings in cost per sqm Black cotton cumulative traffic(msa) soaked CBR Percentage savings in cost per sqm cumulative traffic(msa) soaked CBR Cost of pavement in Rupees per sqm Black cotton cumulative traffic (msa) Cost of pavement in Rupees per sqm cumulative traffic (msa) Unstabilized soil Stabilized soil Unstabilized soil Stabilized soil Fig. 6 Comparative variation in thickness of pavement, percentage saving in cost, and cost of pavement in rupees per square meter with optimum mixes of black cotton soil and local clay blended with sand and fly ash

9 5 th 5 th INDIAN GEOTECHNICAL CONFERENCE 17 th 19 th DECEMBER 215, Pune, Maharashtra, India 1 msa (million standard axles) for CBR values of both stabilized and unstabilized soils. Generally, the soaked CBR value greater than 5.5% is preferred for sub-grade of flexible pavements having lighter traffic intensity. The soaked CBR value of unstabilized soil is 2.78% and the soaked CBR value of stabilized soil mix is 8.81% which have been considered for the design purpose. The variation of percentage saving in cost of flexible pavement construction per square meter for cumulative traffic of 1 to 1 msa is shown in Fig.6. It is observed that the saving in cost for the flexible pavement constructed by using stabilized soil subgrade varies from 37 % to 28 % for cumulative traffic of 1 msa to 1 msa respectively. Thus, the stabilization of locally available soil utilizing industrial and construction waste materials along with the natural poorly graded river sand provides improved compaction and strength characteristics and reduces the cost of construction substantially. The degradation caused to the environment due to use of these waste materials can also be controlled to some extent. From the Fig.6 it is clear that the pavement thickness with respect to cumulative traffic (msa), reduces significantly, hence the cost in rupees per m 2 for pavement design, calculated by local standard schedule of rates (SOR), also reduces with stabilization of black cotton soil in the influence of waste materials, shown by Fig.6, which shows that the cost of flexible pavement construction per square meter varies from 168 to Rupees using un-stabilized sub-grade and from 672 to 1356 Rupees using stabilized sub-grade for cumulative traffic of 1-1 msa. CONCLUSIONS Black cotton and clayey soil in this study is stabilized with the addition of sand. The optimum value of maximum dry density is achieved for black cotton soil and clayey soil-sand mix of 7:3 followed by other proportions. On further increasing the percentage of sand in the composite, amount of sand required increases and composite becomes uneconomical. Based upon the test results, it can be concluded that 15% of Fly Ash may be added when 7% black cotton soil+ 3% sand composite and 1 % of Fly Ash may be added when 7% clayey soil+ 3% sand is used. On further increasing the percentage of Fly Ash, the MDD decreases significantly. Hence, higher percentage of Fly Ash should not be used. The soaked CBR value of expansive soil and clayey soil increases significantly i.e % and % respectively and unsoaked CBR value of expansive soil and clayey soil increases significantly i.e % and % respectively with addition of optimum percentage of sand and fly ash. Thus fly ash can be utilized for sub-grade construction as a part in the mixture of black cotton and clayey soil with sand. REFERENCES 1. Gourley C. S., Newill, D., and Shreiner, H. D., (1993), Expansive soils: TRL s research strategy, Proc., 1st Int. Symp. on Engineering Characteristics of Arid Soils. 2. Choudhary AK, Gill KS & Jha KN (211), Improvement in CBR values of expansive soil sub Geotechnical Conference, ElKholy Sherif M. (28), Improving the Characteristics of expansive soil using coarsegrained soil, Journal of Engineering and Computer Sciences, Qassim University, Vol. 1, No. 2, pp Ramana Murthy (1998), Study on swell pressure and the method of controlling swell of expansive soil, Ph.D, thesis, Kakatiya University, NIT, Warangal. 5. Sabat A. K., Effect of marble dust on strength and durability of Rice husk ash stabilised expansive soil, International Journal of Civil and Structural Engineering Volume 1, No 4, Saranjeet Rajesh Soni et al. Disposal of solid waste for expansive soilstabilization, International Journal of Advanced Engineering Sciences and Technologies Vol No. 8,Issue No. 1, Sridharan S. M. Rao and Murthy, N. S. (1985), Free swell index of soils A need for redefinition, Indian Geo-tech. J., 15, 94 99

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