Chartered Civil Engineer (ICE) Geotechnical and Foundation Engineering Syllabus

What is the relationship between the principal effective stresses at failure (Mohr-Coulomb) for a $c'$, $\phi'$ soil?

$$\sigma'_1 = \sigma'_3 \tan^2\!\left(45^\circ + \tfrac{\phi'}{2}\right) + 2c' \tan\!\left(45^\circ + \tfrac{\phi'}{2}\right).$$ The failure plane is inclined at $\theta = 45^\circ + \frac{\phi'}{2}$ to the major principal plane.

What is the purpose of a desk study in a ground investigation, and name typical information sources?

A desk study collects existing information to identify ground conditions, hazards, history and constraints before fieldwork, informing the conceptual ground model and investigation scope. Sources: geological maps/memoirs (BGS), historical OS maps, aerial photos, mining records, previous site investigation reports, groundwater/flood data, Envirocheck/contamination records, utility records.

What is a walkover survey and what features does the engineer look for?

A walkover (site reconnaissance) is a physical inspection of the site to corroborate and supplement the desk study. The engineer notes topography, surface water/springs, vegetation, made ground/fill, existing structures and cracking, slope instability signs, access constraints, nearby structures, evidence of contamination, and disposal/odour indicators.

Distinguish the main intrusive investigation methods: trial pits, cable percussion boring and rotary drilling.

Trial pits: excavator-dug, shallow (up to ~4–5 m), allow direct logging and bulk/block sampling. Cable percussion (shell-and-auger) boring: in soils, gives disturbed/undisturbed (U100) samples and SPTs to moderate depth. Rotary drilling (open-hole/coring): for rock and deep holes, recovers continuous rock cores for logging.

Describe the Standard Penetration Test (SPT) and define the N-value.

The SPT drives a split-spoon sampler with a 63.5 kg hammer falling 760 mm. The sampler is driven 450 mm; blows for the first 150 mm (seating) are discarded and blows for the final 300 mm summed to give $N$. $N$ correlates with relative density of sands and undrained strength of clays. Often corrected to $N_{60}$ and $(N_1)_{60}$.

What is the Cone Penetration Test (CPT) and what parameters does it measure?

The CPT pushes an instrumented cone (60° apex, $1000\ \mathrm{mm^2}$ base) into the ground at constant rate, continuously measuring cone resistance $q_c$, sleeve friction $f_s$ and (CPTu) pore pressure $u$. Friction ratio $R_f = \dfrac{f_s}{q_c}\times100\%$ helps classify soils; gives a near-continuous profile without sampling.

Distinguish disturbed and undisturbed soil samples and name the main quality classes.

Disturbed samples retain particle composition but not in-situ structure (suitable for classification/index tests). Undisturbed samples preserve structure and are used for strength/consolidation testing. Eurocode 7 sampling quality classes 1–5: Class 1 permits all properties; Classes 4–5 only allow sequence/identification. U100/U38 thin-wall and piston samples target high quality.

List the common index/classification laboratory tests performed in a site investigation programme.

Moisture content, Atterberg limits (LL, PL), particle size distribution (sieving + sedimentation/hydrometer), particle density ($G_s$), bulk/dry density, organic content, sulfate/pH (BRE SD1) for concrete aggressivity, and compaction (Proctor) tests. These classify soils and feed into design parameters.

List the main strength/consolidation laboratory tests and the parameters they yield.

Oedometer (one-dimensional consolidation): $m_v$, $c_v$, $C_c$, $C_r$, $\sigma'_c$. Triaxial (UU/CU/CD): $c_u$ or $c', \phi'$ and stiffness. Direct shear box: $c', \phi'$ (incl. residual). California Bearing Ratio (CBR): subgrade strength for pavements. Permeameter: $k$.

What is Eurocode 7 (BS EN 1997) and what are its two parts?

Eurocode 7 is the European standard for geotechnical design. Part 1 (EN 1997-1) covers general rules and design using limit states with partial factors. Part 2 (EN 1997-2) covers ground investigation and testing. Design uses Ultimate (ULS) and Serviceability (SLS) limit states with characteristic values and partial factors via Design Approaches (UK uses DA1).

What are the Ground Investigation Report (GIR) and Geotechnical Design Report (GDR) under Eurocode 7?

The Ground Investigation Report (GIR) presents and assesses all factual and interpreted ground data (factual + interpretative parts). The Geotechnical Design Report (GDR) documents the design assumptions, parameters, calculations, and includes a plan for supervision/monitoring. EC7 also defines Geotechnical Categories 1–3 reflecting complexity/risk.

Define the characteristic value of a geotechnical parameter in Eurocode 7.

The characteristic value is a cautious estimate of the value affecting the occurrence of the limit state — a conservative selection of the mean (not a fixed percentile, though often described as ~95% confidence in the mean of the relevant zone). Design value $X_d = X_k / \gamma_M$ for material-factored approaches.

Outline the source–pathway–receptor concept used in contaminated land risk assessment.

A pollutant linkage requires all three: a Source (contaminant), a Pathway (route by which it reaches the receptor, e.g. ingestion, inhalation, groundwater migration) and a Receptor (human, controlled water, ecosystem, building). Risk exists only if a complete linkage is present; remediation aims to break the linkage.

What are Generic Assessment Criteria (GAC) and the tiered approach to contaminated land assessment in the UK?

Tiered: Tier 1 = preliminary risk assessment (desk study, conceptual model); Tier 2 = generic quantitative risk assessment comparing measured concentrations against GAC (e.g. C4SLs / S4ULs derived from CLEA model); Tier 3 = detailed quantitative risk assessment with site-specific assessment criteria. Land Part 2A and CLR11/LCRM guidance apply.

State Terzaghi's general bearing capacity equation for a strip foundation.

$$q_u = c\,N_c + q\,N_q + \tfrac{1}{2}\gamma B\,N_\gamma,$$ where $q_u$ = ultimate bearing capacity, $c$ = cohesion, $q$ = surcharge ($\gamma D_f$), $\gamma$ = soil unit weight, $B$ = foundation width, and $N_c, N_q, N_\gamma$ = bearing capacity factors (functions of $\phi$).

For undrained ($\phi_u = 0$) conditions, what is the ultimate bearing capacity of a shallow foundation, and the value of $N_c$?

With $\phi_u = 0$: $N_q = 1$, $N_\gamma = 0$, and for a strip footing $N_c = (2+\pi) \approx 5.14$. Net ultimate bearing capacity $$q_{nu} = c_u N_c s_c d_c i_c,$$ for a strip $q_{nu} \approx 5.14\,c_u$. Square/circular footings use $N_c \approx 6.2$ (shape factor $\approx 1.2$).

Define net bearing pressure, allowable bearing capacity and factor of safety for a shallow foundation.

Net pressure = applied pressure minus original overburden at founding level. Allowable bearing capacity $$q_a = \frac{q_{nu}}{F} + q_0,$$ where $q_{nu}$ = net ultimate, $F$ = factor of safety (typically 3 for total stress) and $q_0$ = overburden. The lower of bearing-capacity and settlement criteria governs.

Give the elastic (immediate) settlement formula for a flexible foundation on a deep elastic layer.

$$s_i = q B \frac{(1-\nu^2)}{E}\,I_f,$$ where $q$ = net bearing pressure, $B$ = width, $\nu$ = Poisson's ratio, $E$ = undrained or drained Young's modulus, and $I_f$ = influence factor depending on shape and rigidity.

Distinguish end-bearing piles and friction (shaft) piles, and write the ultimate pile capacity equation.

End-bearing piles transmit load through the toe to a competent stratum; friction piles transfer load via shaft friction along their length. $$Q_u = Q_b + Q_s = q_b A_b + \sum f_s A_s,$$ where $Q_b$ = base resistance, $Q_s$ = shaft resistance, $A_b$ = base area, $A_s$ = shaft area, $f_s$ = unit skin friction.

Compare driven (displacement) and bored (replacement) piles.

Driven piles: pre-formed and hammered/vibrated in, displace and densify surrounding soil, no spoil, but cause noise/vibration; good in granular soils. Bored (cast-in-place) piles: a hole is augured/excavated and filled with concrete, low vibration, allow large diameters and inspection of strata, but generate spoil and can suffer base relaxation/softening.

For piles in clay, what is the alpha method, and for sands the typical base/shaft resistance approach?

Alpha (total stress) method: unit shaft friction $f_s = \alpha\,c_u$, with adhesion factor $\alpha \approx 0.4$–1.0 (lower for stiff clays). Effective stress (beta) method: $f_s = \beta\,\sigma'_v$. In sands, shaft $f_s = K\,\sigma'_v \tan\delta$ and base $q_b = N_q\,\sigma'_v$ (capped for displacement piles).

Define active, passive and at-rest earth pressure states.

At-rest ($K_0$): wall does not move; soil in its in-situ state. Active ($K_a$): wall moves away from the soil, which expands and reaches minimum lateral pressure. Passive ($K_p$): wall moves into the soil, which compresses to maximum lateral pressure. Order of magnitude: $K_a < K_0 < K_p$.

Give the Rankine earth pressure coefficients for a smooth vertical wall with horizontal backfill.

$$K_a = \frac{1-\sin\phi'}{1+\sin\phi'} = \tan^2\!\left(45^\circ - \tfrac{\phi'}{2}\right),$$ $$K_p = \frac{1+\sin\phi'}{1-\sin\phi'} = \tan^2\!\left(45^\circ + \tfrac{\phi'}{2}\right),$$ and $K_a = 1/K_p$. The at-rest coefficient (Jaky) is $K_0 = 1 - \sin\phi'$ for normally consolidated soil.

How are active and passive pressures computed for a $c'$–$\phi'$ soil (Rankine with cohesion)?

$$\sigma'_a = K_a \sigma'_v - 2c'\sqrt{K_a}, \qquad \sigma'_p = K_p \sigma'_v + 2c'\sqrt{K_p}.$$ Cohesion reduces active pressure (causing a tension crack to depth $z_0 = \dfrac{2c'}{\gamma\sqrt{K_a}}$) and increases passive resistance.

What stability checks are required for a gravity/cantilever retaining wall, and the typical factors of safety?

Check: (1) sliding along the base — $F = \dfrac{\text{resisting (friction + passive)}}{\text{driving (active thrust)}} \geq 1.5$; (2) overturning about the toe — $F = \dfrac{\text{restoring moments}}{\text{overturning moments}} \geq 2.0$; (3) bearing capacity of foundation soil (with eccentricity); (4) overall/global slope stability; (5) settlement. EC7 uses partial factors instead of lumped FoS.

For a smooth vertical wall retaining dry cohesionless soil of height $H$, what is the total active thrust and its point of application?

$$P_a = \tfrac{1}{2} K_a \gamma H^2,$$ acting horizontally at $H/3$ above the base (triangular pressure distribution). If a uniform surcharge $q$ acts, add $K_a q H$ acting at $H/2$. Water pressure (if present) is added separately as a full hydrostatic triangle.

Compare embedded retaining wall types: cantilever, propped/anchored, and how they resist earth pressure.

Cantilever embedded walls (e.g. sheet/secant piles) rely solely on passive resistance of the embedded depth — economical only for shallow retained heights. Propped or anchored walls add support near the top (prop, raking shore or ground anchor), reducing bending moments and embedment depth, enabling deeper excavations.

Describe the method of slices for slope stability and define the factor of safety.

The potential failure mass above a slip surface is divided into vertical slices; equilibrium of each slice gives the resisting vs disturbing forces/moments. $$F = \frac{\text{available shear strength}}{\text{mobilised shear stress}} = \frac{\sum (c'l + (N - ul)\tan\phi')}{\sum W \sin\alpha}.$$ Methods include Fellenius (Swedish), Bishop's simplified, and Janbu.

For an undrained ($\phi_u = 0$) circular slip analysis, how is the factor of safety expressed?

$$F = \frac{c_u\,L_a\,R}{\sum W\,x} = \frac{c_u\,L_a\,R}{M_d},$$ where $c_u$ = undrained strength, $L_a$ = arc length of the slip circle, $R$ = circle radius, $W$ = weight of slice, $x$ = horizontal lever arm to the centre, and $M_d$ = disturbing moment. Taylor's stability number charts can also be used.

What is the infinite slope stability solution for a cohesionless slope, with and without seepage?

Dry/no seepage cohesionless slope: $$F = \frac{\tan\phi'}{\tan\beta},$$ so the slope is stable while slope angle $\beta < \phi'$. With steady seepage parallel to the slope (fully saturated): $$F = \frac{\gamma'}{\gamma_{sat}}\cdot\frac{\tan\phi'}{\tan\beta},$$ roughly halving the factor of safety.

Name common ground improvement techniques and the soil conditions each suits.

Vibro-compaction (clean granular soils — densifies); vibro stone columns (soft cohesive/mixed soils — reinforce and drain); dynamic compaction (loose fills/granular); preloading/surcharge with vertical (band) drains (soft clays — accelerate consolidation); deep soil mixing/grouting (weak/contaminated soils); compaction grouting and jet grouting (localised strengthening/sealing).

Explain how vertical (band) drains accelerate consolidation and their effect on the time factor.

Vertical drains shorten the drainage path by providing radial (horizontal) drainage to closely spaced vertical wicks, so excess pore pressure dissipates much faster (radial consolidation governed by $c_h$ and drain spacing). Because consolidation time $\propto d^2$, reducing the drainage path dramatically reduces settlement time, often used with a surcharge preload.

Define optimum moisture content (OMC) and maximum dry density (MDD) from a compaction test, and why they matter in earthworks.

In a Proctor compaction test, dry density is plotted against moisture content; the peak gives the maximum dry density (MDD) at the optimum moisture content (OMC). Compacting fill at around OMC achieves the densest, strongest, least compressible state. Field compaction is controlled to a percentage of MDD (e.g. 95%) within an acceptable moisture range.

What is the coefficient of uniformity $C_u$ and coefficient of curvature $C_c$ (gradation), and what indicates well-graded soil?

$$C_u = \frac{D_{60}}{D_{10}}, \qquad C_c = \frac{(D_{30})^2}{D_{60}\,D_{10}},$$ where $D_{10}, D_{30}, D_{60}$ are particle sizes at 10/30/60% passing. Well-graded: $C_u > 4$ (gravel) or $>6$ (sand) and $1 \le C_c \le 3$. A low $C_u$ indicates uniform (poorly graded) soil.

Define relative density (density index) of a granular soil and its formula.

$$I_D = \frac{e_{max} - e}{e_{max} - e_{min}}\times100\%,$$ where $e$ = in-situ void ratio, $e_{max}$/$e_{min}$ = loosest/densest void ratios. $I_D$: 0–15% very loose, 15–35% loose, 35–65% medium dense, 65–85% dense, 85–100% very dense. Describes packing state of sands/gravels.

What is liquefaction and which conditions make a soil susceptible?

Liquefaction is the sudden loss of shear strength when undrained cyclic loading (e.g. earthquake) generates excess pore pressure that rises to equal total stress, reducing effective stress to zero. Most susceptible: loose, saturated, uniform (poorly graded) fine sands and silts with low relative density below the water table.

Distinguish total stress and effective stress analysis and state when each is appropriate.

Total stress (undrained) analysis uses $c_u$, $\phi_u = 0$ and total stresses — appropriate for short-term stability in low-permeability clays immediately after loading (no drainage). Effective stress (drained) analysis uses $c', \phi'$ with pore pressures — appropriate for long-term conditions and for free-draining granular soils where excess pore pressure dissipates quickly.

For consolidation settlement using the coefficient of volume compressibility $m_v$, what is the formula?

$$s_c = m_v\,\Delta\sigma'\,H,$$ where $m_v$ = coefficient of volume compressibility ($\mathrm{m^2/MN}$), $\Delta\sigma'$ = increase in effective stress, and $H$ = thickness of the compressible layer. $m_v$ is obtained from oedometer test results over the relevant stress range.

What is negative skin friction (downdrag) on a pile and when does it occur?

Negative skin friction occurs when the soil around a pile settles more than the pile (e.g. consolidating soft clay, fill placed over compressible ground, lowered water table). The settling soil drags the pile downward, imposing an additional axial load and reducing net capacity rather than supporting the pile. It is added as a load, not a resistance.

Explain the difference between peak, critical-state and residual shear strength of clay.

Peak strength: maximum shear resistance, mobilised at small strain, associated with dilation/structure (higher $c', \phi'_p$). Critical-state (constant volume): strength at large strain with no volume change ($c'=0$, $\phi'_{cv}$). Residual strength: minimum strength after large displacement with particle re-orientation along a slip surface ($\phi'_r < \phi'_{cv}$) — governs reactivated landslides.