(SEM V) THEORY EXAMINATION 2017-18 GEOTECHNICAL ENGINEERING

Geotechnical Engineering (NCE-501 / ECE-501)

Section-Wise Important Questions & Study Notes

SECTION–A

(Attempt all questions | 2 × 10 = 20)
This section tests definitions, basic concepts, and short differences.
Write 2–3 lines only, be precise.

Index Properties
Index properties are basic soil characteristics (water content, specific gravity, Atterberg limits, grain size) used to classify soil and predict behavior.

Primary & Secondary Valence Bonds
Primary bonds are strong ionic/covalent bonds within minerals; secondary bonds are weak attractions (van der Waals, hydrogen) between particles.

Methods to Determine Water Content
Oven-drying method, sand bath method, calcium carbide method, torsion balance method.

Bulk Unit Weight & Relation with Dry Unit Weight
Bulk unit weight is weight per unit volume of soil including water.
Relation: γ = γd (1 + w)

Muck
Muck is highly organic, compressible soil with very low strength, unsuitable for foundations.

Consistency Limits (Atterberg Limits)
They are liquid limit, plastic limit, and shrinkage limit, defining soil consistency at different water contents.

Activity vs Sensitivity
Activity relates plasticity to clay content; sensitivity is strength loss on remoulding.

Active vs Passive Earth Pressure
Active pressure occurs when soil mass expands; passive pressure when soil mass is compressed.

Assumptions in Terzaghi’s Bearing Capacity Theory
Soil is homogeneous, isotropic, footing is rigid, load is vertical and central, failure is general shear.

Mohr’s Circle
Graphical representation of stress state showing normal and shear stresses on any plane.

SECTION–B

(Attempt any THREE | 10 × 3 = 30)
Numerical + theory based.

1. Ultimate Bearing Capacity (Terzaghi Theory – Numerical)

Prepare:                                                                                 Formula for strip footing

Bearing capacity factors (Nc, Nq, Nγ)                                   Step-wise solution

2. Shear Failure Mechanisms & Bearing Capacity Terms

Explain:                                                                                  General shear failure

Local shear failure                                                                 Punching shear failure

Differentiate:                                                                         Ultimate bearing capacity

Safe bearing capacity                                                            Safe bearing pressure

Allowable bearing pressure

3. Boussinesq vs Westergaard Theory

Explain:                                                                                  Which is suitable for sedimentary soil

Assumptions of Westergaard theory                                    Numerical for vertical stress increment

Stress variation graph

4. Compaction Control & Filter Design

(i) Proctor’s Needle Method – field compaction control
(ii) Filter Design Conditions – prevent piping in earth dams

5. Residual vs Transported Soils & Soil Relationships

Explain:                                                                                   Residual soils

Transported soils                                                                    Grain size ranges as per IS
Derive: Se = wG

SECTION–C

(Attempt any ONE | 10 × 1 = 10)
Volumetric relationships + soil structure.

3(a) Wax-Coated Sample (Numerical)

Find:                                                                                     Void ratio

Degree of saturation                                                            Use displaced water method clearly.

OR

3(b) Clay Minerals & Saturation Numericals

(i) Formation of kaolinite, illite, montmorillonite (with sketches)
(ii) Water content at saturation and with volume increase