IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 _______________________________________________________________________________________________ Volume: 06 Issue: 03 | Mar-2017, Available @ https://ijret.org 19 STUDY OF SHEAR BEHAVIOUR OF YAMUNA SAND BLENDED WITH SOFT SOIL Deepak Rana 1 , Ankit Soni 2 , Farukh Ali 3 1 M. Tech (Geotechnical Engineering), Department of Civil Engineering, Delhi Technological University, Delhi, India 2 M. Tech (Geotechnical Engineering), Department of Civil Engineering, Delhi Technological University, Delhi, India 3 Assistant Professor, Department of Civil Engineering, Sanskar College of Engineering & Technology, Ghaziabad, India Abstract The structure resulting from compacting the soil at different water contents and energy levels can have a substantial effect on its shear strength. While the shear strength can be estimated based on the saturated shear strength parameters and the unsaturated angle of shearing resistance, limited studies have explored the variation of shear strength properties with different compaction states. In the present study, shear behavior of virgin Yamuna sand and Yamuna sand blended with two clays of different mineralogy i.e. bentonite and kaolinite was investigated by Direct Shear test and Unconsolidated Undrained Tri-axial test. Index properties and compaction characteristics of soil are also studied in this project. It was aimed to observe the shear behavior of sand-bentonite and sand-kaolinite mixtures. Various tests conducted on virgin soil were performed for the determination of following parameters: field moisture content, Atterberg Limits, Grain Size Analysis, Standard Proctor Compaction test, Direct Shear and Triaxial Unconsolidated Undrained test. Compaction tests were conducted on mixtures of 5%,10%,15%,20% by weight bentonite and kaolinite. Direct Shear test and UU Triaxial tests were performed on mixes with 5%,10%,15%,20% by weight of bentonite and kaolinite. It was found that there is increase in MDD and OMC of the soil mixes for both kaolinite and bentonite. Maximum MDD was achieved with kaolinite clay and maximum OMC with bentonite clay. Direct shear test resulted in the increase in cohesion and decrease in friction angle for both bentonite and kaolinite. Similar results are obtained in UU Triaxial tests. However, shear parameters obtained in Direct Shear test is slightly more than obtained in Triaxial tests. Keywords: Shear Behavior, Yamuna Sand, Bentonite, Kaolinite. --------------------------------------------------------------------***---------------------------------------------------------------------- 1. INTRODUCTION 1.1 General Yamuna sand is chiefly found alongside the river Yamuna in Delhi .It has low load carrying capacity and also get eroded easily. Delhi lies in the seismic zone 4 which is high damage risk or seismic active zone. Moreover, Yamuna sand in Delhi as well as NCR region contains remarkable quantity of silt and thus it is in peril to liquefaction during earth tremor below ground water table. At several places ground water is at shallow depth and structures built over sand under such conditions are not safe. Therefore, understanding the shear behavior of Yamuna sand and its improvement in shear strength is necessary. One of the best method to improve the strength of sand is to blend it with soft soil. Soft soil is mainly clay that is expansive in nature, highly compressible, low permeability; have high specific surface and large water holding capacity as well as cohesion when come in contact with water. There are two type of clays used in the present study namely: 1) bentonite clay and 2) kaolinite clay. Bentonite clay is essentially absorbent aluminum phyllosilicate clay that contains primarily of montmorillonite mineral. It is highly plastic clay formed by the weathering of volcanic ash generally in presence of water. There are three types of bentonite based on the dominant element present in them: 1. Sodium bentonite 2. Potassium bentonite 3. Calcium bentonite Sodium bentonite has property to enlarge several times of its dry mass in presence of water. It is used in several geotechnical explorations such as drilling mud for gas and oil wells,in boreholes ,as a low permeability liner in various landfills etc. Potassium bentonite has potassium as its main element. It is formed from the alteration of volcanic ash and contains illite clay mineral. Calcium bentonite is fundamentally used as adsorbent in ionic solution and also in oils. It is important element in the fuller’s earth which is used as an rinsing agent. Calcium bentonite can be converted into sodium bentonite by ion exchange process. Bentonite is also used in several geotechnical works such as drilling mud, as a binder, purification, ground water barrier and also bentonite slurry walls used in modern construction. Sand- bentonite mixtures have been used as a liner in the landfills due to its low permeability. In the present study Yamuna sand has been mixed with varying proportions of