Mastering Soil Mechanics- Consolidation & Earth Pressure

Understand the Mohr-Coulomb theory of soil shear strength, deriving the effective stress form with friction and cohesion. Compare maximum and mobilized shear parameters, and distinguish safe versus unsafe loading conditions.

Explore failure envelopes for cohesionless, cohesive, and c-phi soils using Coulomb's law and effective shear strength, and how normal stress governs safe and unstable states.

Learn how Mohr's circle computes normal and shear stresses on any plane in a soil element, identify principal stresses, and connect Mohr's circle with Coulomb's theory for soil strength.

Learn how triaxial shear tests determine sigma1 and sigma3 to derive c and phi, and review consolidated drained, consolidated undrained, and unconsolidated undrained variants, including volumetric and axial strains.

Explain the unconfined compression test (UCS) as a zero-confinement triaxial test on cohesive soils, where axial loading yields UCS equal to 2c and reveals soil sensitivity.

Explore the vane shear test for measuring undrained shear strength of soft clays and clay sensitivity, distinguishing one-way and two-way shearing via torque and curved-surface and face resistances.

Explore the Skempton pore pressure parameters B and A, linking pore pressure change to confining and deviatoric stresses in soil, with typical value ranges and practical use.

Explore how sand gains shear strength from friction and interlocking, detailing dense versus loose sand behavior, stress–strain response, volume changes, and the concept of a critical void ratio.

Examine the shear behavior of clays, highlighting how permeability, cohesion, and stress history affect undrained, CU, and CD tests, and how drainage and saturation control Mohr envelopes.

Determine the resultant stress on a cohesionless soil failure plane from normal and shear stresses, and identify the angle of internal friction and failure plane, analytically and graphically.

Solve numericals on cohesionless soil shear strength at 3 m depth with rising water table; compare initial and submerged conditions and observe reduction of shear strength in unconfined compression test.

Solve soil shear strength problems through unconfined and triaxial tests; compute cohesion and friction angle from stresses, and analyze Mohr circle and failure envelope for c, phi, and deviatoric stress.

Solves drained triaxial shear strength problems, deriving cohesion and friction angle from sigma1 and sigma3, and contrasts total vs effective stresses under rapid and slow loading.

Explore lateral earth pressure, its active, passive, and earth pressure at rest states, how horizontal and vertical stresses relate through the coefficients k a, k p, and k not.

Explore active and passive earth pressure behind a retaining wall, focusing on major principal planes, the failure plane, and Ka, Kp, La, Lp with theta.

Analyze submerged soil behind a retaining wall by evaluating effective pressures, pore water pressure, and total earth force using triangular and rectangular diagrams with centroid-based moments.

Explore inclined earth pressure scenarios on a retaining wall, including inclined backfill, inclined wall, and combined inclinations; calculate ka and kp and the resultant force.

Derives earth pressure in cohesive soil under active state, linking horizontal and vertical stresses with cohesion, and explains zero pressure at the critical depth hc.

This lecture solves earth pressure numericals in cohesionless soil, derives dry and submerged unit weights, and computes active and passive pressure coefficients Ka and Kp with total thrust per length.

Outline Coulomb's earth pressure assumptions: homogeneous, isotropic, cohesionless soil; include soil wall friction via an external friction angle. Assume a 2D, rigid wedge with a plane rupture surface, unlike Rankine.

Explore how soil compaction reduces volume by expelling air and rearranging solids using rollers, rammers, or vibratory plates, and examine objectives like increasing shear strength and reducing permeability and settlement.

Explore how water content and lubrication affect soil compaction, leading to maximum dry density and optimum moisture content, and understand air void and zero air void lines.

Explore laboratory soil compaction tests, including standard proctor, modified proctor, Indian standard, Harvard miniature, Abbott, and Deterts tests, and learn to calculate compactive energy using mgh.

Solve numericals on soil compaction for an embankment, relating borrow pit and compacted states via solids mass, compute excavation volume, water addition, dry unit weight, and saturated unit weight.

Explore slope stability in geotechnical engineering, examining natural and man-made slopes, translational, rotational, and wedge failures, and stabilization techniques like drainage, geometry changes, and vegetation.

Identify factors that cause slope failure, including gravity-induced translational and rotational failures, water effects (erosion and seepage), sudden water-table drawdown, vibrations from earthquakes or machinery, and surcharge.

Learn how seepage parallel to the slope alters infinite slope stability by deriving gamma equivalent and pore water pressure to compute the factor of safety, halved after rainfall stops.

Analyze infinite slopes by calculating factors of safety for strength, cohesion, and friction using intergranular pressure 102.5 kN/m^2 and shear strength parameters with mobilized values.

Explore finite slopes with curved failure surfaces and compare the Kalman plane method to circle and slice approaches, highlighting the factor of safety.

Apply bishop's simplified method of slices to account for unequal lateral forces on soil slices in heterogeneous slopes, improving accuracy over the Swedish method.

Apply the Morgenstern method to assess slope stability under sudden water-table drawdown, using the Skempton pore pressure parameter and drawdown ratio to read the factor of safety from charts.

Spencer method of slopes analysis blends Felinas 1927 slices and Bishop's method, using force and moment equilibria to compute the factor of safety via charts.