GATE Civil Engineering Geotechnical Engineering Syllabus

Geotechnical Engineering syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Geotechnical Engineering in GATE Civil Engineering, not a summary of it.

1. 1

   Soil Mechanics

   11 topics

   • Three-phase system and phase relationships
   • Index properties
   • Unified and Indian standard soil classification system
   • Permeability - one dimensional flow
   • Seepage through soils – two-dimensional flow
     • Flow nets
     • Uplift pressure
     • Piping
     • Capillarity
     • Seepage force
   • Principle of effective stress and quicksand condition
   • Compaction of soils
   • One-dimensional consolidation
     • Time rate of consolidation
   • Shear Strength
     • Mohr’s circle
     • Effective and total shear strength parameters
   • Stress-Strain characteristics of clays and sand
   • Stress paths
2. 2

   Foundation Engineering

   10 topics

   • Sub-surface investigations
     • Drilling bore holes
     • Sampling
     • Plate load test
     • Standard penetration test
     • Cone penetration tests
   • Earth pressure theories
     • Rankine
     • Coulomb
   • Stability of slopes
     • Finite and infinite slopes
     • Bishop’s method
   • Stress distribution in soils
     • Boussinesq’s theory
   • Pressure bulbs
   • Shallow foundations
     • Terzaghi’s bearing capacity theories
     • Meyerhoff’s bearing capacity theories
     • Effect of water table
   • Combined footing and raft foundation
   • Contact pressure
   • Settlement analysis in sands and clays
   • Deep foundations
     • Dynamic and static formulae
     • Axial load capacity of piles in sands and clays
     • Pile load test
     • Pile under lateral loading
     • Pile group efficiency
     • Negative skin friction

Geotechnical Engineering flashcards for GATE Civil Engineering

23 of 58 cards from the Geotechnical Engineering deck — real questions with worked answers.

1. In a soil three-phase system, write the relationship between void ratio $e$ and porosity $n$.

   $$e=\frac{n}{1-n}\qquad\text{and}\qquad n=\frac{e}{1+e}$$ where $e=\frac{V_v}{V_s}$ (voids/solids) and $n=\frac{V_v}{V}$ (voids/total).

2. State the fundamental phase relationship linking void ratio $e$, water content $w$, specific gravity $G$ and degree of saturation $S$.

   $$S\,e = w\,G$$ For a fully saturated soil $S=1$, so $e=wG$.

3. Give the formula for the dry unit weight $\gamma_d$ of soil in terms of $G$, $e$ and $\gamma_w$.

   $$\gamma_d=\frac{G\,\gamma_w}{1+e}$$

4. Write the general expression for the bulk (moist) unit weight $\gamma$ in terms of $G$, $S$, $e$.

   $$\gamma=\frac{(G+Se)\,\gamma_w}{1+e}$$ For saturated soil ($S=1$): $\gamma_{sat}=\dfrac{(G+e)\gamma_w}{1+e}$.

5. Define submerged (buoyant) unit weight $\gamma'$ and give its formula.

   It is the effective unit weight of soil below water: $$\gamma'=\gamma_{sat}-\gamma_w=\frac{(G-1)\gamma_w}{1+e}$$

6. How is degree of saturation $S$ defined, and what are its values for dry and saturated soils?

   $$S=\frac{V_w}{V_v}\times 100\%$$ $S=0\%$ for fully dry soil and $S=100\%$ for fully saturated soil.

7. Define water content $w$ and air content $a_c$ of a soil.

   Water content $w=\dfrac{W_w}{W_s}$ (weight of water / weight of solids). Air content $a_c=\dfrac{V_a}{V_v}$ so $a_c=1-S$.

8. What is the percentage air voids $n_a$, and how does it relate to porosity and air content?

   $$n_a=\frac{V_a}{V}=n\,a_c=n(1-S)$$ It is the volume of air expressed as a fraction of total volume.

9. Define the relative density (density index) $I_D$ of a cohesionless soil and give the void-ratio form.

   $$I_D=\frac{e_{max}-e}{e_{max}-e_{min}}\times 100\%$$ where $e$ is the in-situ void ratio. $I_D=0$ at loosest, $100\%$ at densest state.

10. List the Atterberg limits in order of increasing water content and name the consistency states they separate.

    Shrinkage limit ($w_s$) → Plastic limit ($w_p$) → Liquid limit ($w_L$). They separate solid → semi-solid → plastic → liquid states with increasing water content.

11. Define plasticity index $I_P$ and what it physically represents.

    $$I_P=w_L-w_P$$ It is the range of water content over which the soil behaves plastically; larger $I_P$ indicates more clayey, more plastic soil.

12. Define the liquidity index $I_L$ and consistency index $I_C$.

    $$I_L=\frac{w-w_P}{I_P},\qquad I_C=\frac{w_L-w}{I_P}$$ where $w$ is natural water content. Note $I_L+I_C=1$.

13. Define the flow index $I_f$ and toughness index $I_t$ from the liquid limit test.

    Flow index $I_f$ is the slope of the flow curve (water content vs $\log N$): $$I_f=\frac{w_1-w_2}{\log_{10}(N_2/N_1)}$$ Toughness index $I_t=\dfrac{I_P}{I_f}$.

14. What does the activity $A$ of a clay measure, and how is it computed?

    $$A=\frac{I_P}{\text{(\% clay-size, finer than }2\,\mu m)}$$ It indicates swelling potential: $A<0.75$ inactive, $0.75$–$1.25$ normal, $>1.25$ active (e.g., montmorillonite).

15. In the Unified Soil Classification System (USCS), what do the first and second letters of a group symbol denote? Give the prefix letters.

    First letter = primary fraction: G (gravel), S (sand), M (silt), C (clay), O (organic), Pt (peat). Second letter = gradation/plasticity: W (well graded), P (poorly graded), M (silty), C (clayey), L (low plasticity), H (high plasticity).

16. For coarse-grained soils, give the gradation criteria for a well-graded gravel (GW) and well-graded sand (SW).

    Well graded requires $C_u>4$ (gravel) or $C_u>6$ (sand), AND $1\le C_c\le 3$, where $$C_u=\frac{D_{60}}{D_{10}},\qquad C_c=\frac{D_{30}^{2}}{D_{60}\,D_{10}}$$

17. What is the A-line equation on the plasticity chart and what does it separate?

    $$I_P=0.73\,(w_L-20)$$ It separates clays (above A-line, C) from silts and organic soils (below A-line, M/O). The U-line $I_P=0.9(w_L-8)$ is the upper limit of natural soils.

18. In USCS, what liquid-limit boundary separates low (L) from high (H) plasticity fine soils?

    $w_L=50\%$. $w_L<50$ → low plasticity (L); $w_L\ge 50$ → high plasticity (H). Coarse soils are split at the $75\,\mu m$ (No. 200) sieve.

19. State Darcy's law for one-dimensional flow through soil.

    $$v=k\,i=k\frac{h}{L},\qquad Q=k\,i\,A$$ where $v$ is discharge (Darcy) velocity, $i=h/L$ the hydraulic gradient, $k$ the coefficient of permeability, and $A$ the gross cross-sectional area.

20. Distinguish the discharge (Darcy) velocity $v$ from the seepage velocity $v_s$.

    $$v_s=\frac{v}{n}$$ The seepage velocity (actual velocity through voids) equals the Darcy velocity divided by porosity $n$, and is always greater than $v$.

21. How does temperature affect the coefficient of permeability $k$? Give the correction relation.

    $$k=\frac{K\,\gamma_w}{\mu}$$ where $K$ is absolute permeability (property of soil only) and $\mu$ is the fluid viscosity. As temperature rises, $\mu$ falls so $k$ increases; values are normalized to $27^{\circ}$C in India.

22. Give the equivalent permeability for stratified soils for flow parallel to and perpendicular to the bedding planes.

    Parallel (horizontal): $$k_H=\frac{\sum k_i H_i}{\sum H_i}$$ Perpendicular (vertical): $$k_V=\frac{\sum H_i}{\sum \frac{H_i}{k_i}}$$ Always $k_H\ge k_V$.

23. Which lab test suits coarse-grained soils for $k$ and which suits fine-grained soils? Give the falling-head formula.

    Constant-head test → coarse soils; falling-head test → fine soils. Falling head: $$k=\frac{aL}{At}\ln\frac{h_1}{h_2}=2.303\frac{aL}{At}\log_{10}\frac{h_1}{h_2}$$

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