(SEM V) THEORY EXAMINATION 2023-24 GEOTECHNICAL ENGINEERING

Subject Code: KCE501

Subject Name: Geotechnical Engineering

Course: B.Tech (Semester V)

Maximum Marks: 100

Duration: 3 Hours

Exam Year: 2023–24

Sections: A, B, and C

SECTION A – Short Answer Questions (2 × 10 = 20 Marks)

Attempt all questions briefly.

a. Discuss Plasticity Index (PI) and Liquidity Index (LI).
b. Write down expressions for Coefficient of Uniformity (Cu) and Coefficient of Curvature (Cc).
c. What are the limitations of Darcy’s Law?
d. Define Quick Sand Condition.
e. Discuss factors affecting time factor and degree of consolidation.
f. What is meant by Soil Compaction?
g. State assumptions of Westergaard’s Theory.
h. List tests for determining shear strength of soil.
i. Write expression for stability number.
j. Define slope and state its applications.

SECTION B – Medium-Length Questions (10 × 3 = 30 Marks)

Attempt any three of the following.

Numerical:

Given: w=15%,γwet=25 kN/m3,G=2.70,γw=10 kN/m3w = 15\%, \gamma_{wet} = 25 \, kN/m^3, G = 2.70, \gamma_w = 10 \, kN/m^3w=15%,γwet​=25kN/m3,G=2.70,γw​=10kN/m3.

Find: Dry unit weight, void ratio, and degree of saturation.

Describe Darcy’s Law and its validity range.

Write short notes on:

(A) Normally and Over-consolidated soils

(B) Coefficient of compressibility & coefficient of volume change

(C) Compression index, swelling index, recompression index

Vane Shear Test:

Torque = 35 N·m, Diameter = 50 mm, Length = 100 mm.

Find: Undrained shear strength and sensitivity of clay when remoulded torque = 5 N·m.

Explain types of slope failures with neat diagrams.

SECTION C – Long / Analytical Questions (10 × 5 = 50 Marks)

Q3. Soil Properties

a. A saturated clay sample:

Water content = 30.5%, Mass specific gravity (wet) = 1.96, (dry) = 1.60.

Find specific gravity of clay solids.
OR
b. A partially saturated sample (w = 15%, G = 2.70, γ = 1.9 g/cc).

Find: Void ratio, degree of saturation, and saturated unit weight.

Q4. Effective Stress and Seepage

a. A 10 m soil layer over an impermeable stratum with water table 5 m below ground.

Top 2 m above water table: S=50%,e=0.6,G=2.67S = 50\%, e = 0.6, G = 2.67S=50%,e=0.6,G=2.67.

Plot: Total stress, pore pressure, and effective stress.
OR
b. Describe flow net and explain seepage estimation through it.

Q5. Compaction and Consolidation

a. Discuss field compaction equipment: types of rollers suitable for clayey and gravel soils and their specifications.
OR
b. A clay layer (thickness = 5 m) takes 1.5 years for 50% consolidation.

mv=1.5×10−3 m2/kNm_v = 1.5 \times 10^{-3} \, m^2/kNmv​=1.5×10−3m2/kN.

Find: Coefficient of consolidation (C_v) and permeability (k).

Q6. Stress Distribution

a. A concentrated load of 30 kN acts on a soil mass.

Find stress at 8 m depth, (i) below the load and (ii) 6 m horizontally away.
OR
b. Using Boussinesq’s Theory, find vertical stress increment 7 m below the center of a 6 m × 6 m tower carrying 10,000 kN.

Q7. Earth Pressure and Slope Stability

a. Retaining wall with smooth backface retaining c–ϕc–\phic–ϕ soil (γ = 1.9 t/m³, c = 1.7 t/m², ϕ = 15°, h = 6 m).

i. Plot active earth pressure distribution.

ii. Find total thrust & point of application.

iii. Find depth of tension crack zone.
OR
b. Explain Swedish Circle Method for slope stability and derive Factor of Safety (FOS) expression.

Key Topics to Prepare

Soil Properties & Classification

Plasticity & liquidity indices                                                Grain size distribution — Cu, Cc

Three-phase system relationships (e, w, Sr, γd)                  Soil classification: IS & Unified Systems

Permeability & Seepage

Darcy’s law, its limitations, and field applications              Flow nets and effective stress computation

Compaction & Consolidation

Standard & Modified Proctor Tests        Equipment types: smooth-wheel, sheep-foot, pneumatic rollers

Consolidation theories (Terzaghi’s equation)

Stress Distribution & Shear Strength

Boussinesq & Westergaard theories      Shear strength tests: Direct, Triaxial, Unconfined, Vane shear

Sensitivity of clay

Slope Stability & Earth Pressure

Types of slope failures (rotational, planar, wedge)          Swedish Circle method — FOS analysis

Rankine & Coulomb theories                                        Tension cracks and earth pressure distributions

Study Tips

Revise definitions & relationships — they often appear as 2-mark questions.

Solve numericals — especially on unit weights, stress, and consolidation.

Draw clear sketches — soil stress profiles, slope failures, and retaining wall pressures.

Memorize important formulas — Darcy’s Law, Boussinesq stress, consolidation equations.

Understand practical relevance — relate topics to field applications (e.g., retaining wall design, seepage control).