Course Scheme -UCE501: SOIL MECHANICS L T P Cr 3 1 2 4.5 Course Objective: To expose the students about the various index and engineering properties of soil. Introduction: Soil formation, various soil types. Phase relationships: Index properties, sieve & hydrometer analysis, Atterberg s limits, sensitivity, thixotropy, and plasticity charts. Determination of engineering properties of soil. Indian standard and Unified classification systems of soils. Clay Mineralogy: Introduction to Clay minerals their characteristics. Soil structure, granular soil fabric. Seepage and Permeability: Darcy s law, validity of Darcy s Law, seepage velocity, factors affecting permeability, Laboratory and field determination of permeability. Flow net and its properties, Laplace equation, methods of drawing flownet, seepage through earth dams, exit gradient and seepage pressures, phenomenon of piping and heaving, filters. Anisotropy, Permeability of layered soils. Effective Stress Principle Capillarity, types of head, seepage forces, quick sand condition, and critical hydraulic gradient. Compaction: Compaction tests, OMC, factors affecting compaction, control of compaction, field compaction equipment and their suitability. Stresses in Soils:Stresses beneath various loaded areas, Boussinesq and Westergarrd s formulae, pressure bulbs, Newmark s chart. Approximate methods Compressibility and Consolidation:Terzaghi s theory, time rate of consolidation, consolidation test, Compressibility & Coefficient of Consolidation, NC, OC soils, determination of pre-consolidation pressure, settlement analysis, secondary consolidation. Shear Strength: Definition, Mohr s stress circle, Mohr-Columb strength theory, direct, triaxial, unconfined and vane shear tests. Drainage conditions, Concept of pore pressure coefficients, shear characteristics of normally consolidated, over consolidated clays and dense and loose sands, Dilatancy, residual strength, Introduction to stress path.
Laboratory Work: The students will be introduced to Index and Engineering properties of soils to complement the theory component of the course by performing experiments. They will perform related experiments as per BIS specifications. 1. Determination of water content. 2. Determination of field density by Core cutter method 3. Determination of field density by Sand replacement method 4. Grain size Analysis by Mechanical Method. 5. Grain size Analysis by Hydrometer Method. 6. Determination of Specific Gravity by Psychomotor. 7. Determination of Liquid Limit, Plastic limit. 8. Determination of Shrinkage limit. 9. Determination of Permeability by constant head permeameter. 10. Determination of permeability by variable head permeameter. 11. Consolidation Test 12. Unconfined Compression Test. 13. Direct Shear Test. Experimental Project/assignment/Micro Project: Students in groups of 4 to 6 will do the projects 1. Bringing soil samples from the field classify them by performing lab tests and then determining the optimum moisture content and maximum dry density. 2. Based on OMC and MDD they will prepare samples for determination of CBR. Course Learning Outcome(CLO): Upon completion of this course, the students will be able to: 1. Determine the index and engineering properties of soil 2. Evaluate the influence of water on engineering properties of soil 3. Evaluate the compressibility characteristics of soils in engineering practices 4. Determine the shear strength of soils by various methods
Text Books: 1. Gopal Ranjan & A.S.R. Rao, Basic and Applied Soil mechanics, New Age Publisher, New Delhi(2012). 2. V.N.S. Murthy, A text book on Soil Mechanics and Foundation Engineering, U.B.S. Publisher, New Delhi(2005). 3. Parshotham Raj, Geotechnical Engg., Pearson, New Delhi(2013). Reference Books: 1. Das B.M., Principles of Soil Mechanics, Thomson Publisher, USA(2012). 2. Venkatramaiah Geotechnical Engg., New Age Publisher, New Delhi(2012). 3. Singh Alam Modern Geotechnical Engineering, CBS Publishers, New Delhi(2014). Evaluation Scheme: Sr. No. Evaluation Elements Weightage (%) 1. MST 25 2. EST 35 3. Sessionals (May include Assignments/Projects/Tutorials/Quizes/Lab Evaluations) 40
Soil Formation and Soil Deposits in India
Definition According to Terzaghi, Soil Mechanics is the application of the laws of mechanics and hydraulics to engineering problems dealing with sediments and other unconsolidated accumulations of solid particles produced by the mechanical and chemical disintegration of rocks regardless of whether or not they contain an admixture of organic constituents. The term Soil Mechanics is now accepted quite generally to designate that discipline of engineering science which deals with the properties and behaviour of soil as a structural material
Soil Formation Soil Originated from physical and chemical weathering of parent rock Organic origin Extremely compressible Product of physical weathering Product of chemical weathering To be avoided Due to impact and grinding action of flowing water, ice, wind Due to oxidation, hydration, carbonation, leaching by organic acids and water. Retain the minerals in parent rocks and are COARSE grained (Gravels and sands) Chemical composition may alter, FINE grained (clays and fine silts)
General types of soil Residual soils Term for those products of rock weathering which are still located at the place where they originated. Might be partially disintegrated. Transported soils Term for those rock weathering products that has been transported from it s place of origin. Deposited from suspension in running water Alluvial deposit Deposited from suspension in still, fresh water of lakes Deposited from suspension in sea water Lacustrine deposit Marine deposit Transported by wind Transported by ice Aeolian deposit Glacial deposit
Regional soil deposits of India Marine deposits Laterites Black cotton soils Alluvial soils Desert soils Boulder deposits
Alluvial soil Covers large area north of Vidhya-Satpura range in Indo-Gangetic and Brahmaputra flood plains, from Assam to Punjab, Alternating layers of sand, silt and clay, Fine silty sand deposits are loose, Prone to liquefaction under seismic conditions
Marine deposits All along coast in narrow tidal plains Marine clays are very soft and may contain organic matter, Possess low shear strength and high compressibility
Lateritic deposits Extend over Kerala, Karnataka, Maharashtra, Orissa and West Bengal, Reddish in colour, Hard in dry state, Generally pose no problem as foundation material and retain their slopes well
Black cotton soil Extend over Madhya Pradesh, Karnataka, Maharashtra, Andhra Pradesh, Tamil Nadu and Uttar Pradesh, Formed from basalt or trap, Rich in montmorillonite mineral (responsible for excessive swelling and shrinkage characteristics), Expansive soil, Pile foundation most appropriate in such soils (to transfer load to strata of adequate strength and below zone of moisture variation).
Desert soil Large parts of Rajasthan, Wind blown deposits of sand, Non-plastic uniformly graded fine sand, Problematic if required to be stabilised for roads and runways, Difficult to reduce settlement and permeability (requirement for water reservoir projects)
Nomenclature of soil used in practice GRAVEL SOIL