Importance of exploration program, Methods of exploration: Boring, sounding tests, geophysical methods-Electrical resistivity and Seismic refraction methods.Types of samples- undisturbed, disturbed and representative samples Samplers, sample disturbance, area ratio, Recovery ratio, clearance Stabilisation of boreholes - Typical bore log. Number and depth of borings for various civil engineering structures, soil exploration report.
Location of ground water table in fine and coarse grained soils. Determination of ground water level by Hvorselev’s method. Control of ground water during exavation: Dewatering- Ditches and sumps, well point system, Shallow well system, Deep well system, Vaccum method, Electro- Osmosis method.
Boussinesq’s and Westergaard’s theories for concentrated, circular, rectangular, line and strip loads. Comparison of Boussinesq’s and westergaard’s analysis. Pressure distribution diagrams, contact pressure, Newmark’s chart.
Laplace equation (no derivation) assumptions and limitations only, characteristics and uses of flownets, Methods of drawing flownets for Dams and sheet piles. Estimating quantity of seepage and Exit gradient. Determination of phreatic line in earth dams with and without filter.Piping and protective filter, graded filter.
LATERAL EARTH PRESSURE: Active and Passive earth pressures, Earth pressure at rest, Earth pressure coefficient. Earth pressure theories- Rankine’s and Coulomb’s –assumptions and limitations, Graphical solutions for active earth pressure (cohesionless soil only) –Culmann’s and Rebhann’s methods Lateral earth pressure in cohesive and cohesionless soils, Earth pressure distribution.
Types of slopes, causes and type of failure of slopes. Definition of factor of safety, Stability of finite and infinite slopes- Method of slices, Friction Circle method, Fellineous method, Taylor’s stability number.
Definitions of ultimate, net and safe bearing capacities, Allowable bearing pressure. Terzaghi’s and Brinch Hansen’s bearing capacity equations-assumptions and limitations Bearing capacity of footing subjected to eccentric loading. Effect of ground water table on bearing capacity.Plate load test, Standard penetration test, cone penetration test.
Settlement Analysis, Data for settlement analysis, computation of settlement, Concept, immediate, consolidation and secondary settlements (no derivations), Tolerance. BIS specifications for total and differential settlements of footings and rafts.