Chapter X : Foundation Engineering and Earth Pressure

Loksewa 7th Level -- Civil Engineering -- Chapter 10

Foundation Engineering & Earth Pressure -- Complete Revision Notes

Every definition, theory, formula, comparison table, diagram, mnemonic and exam-style answer you need for this chapter -- built for fast revision and mock practice.

Fig 0 -- Load transfer sequence: Roof to Beam to Column to Foundation to Soil

On this page

1. Part A -- Foundation Engineering
2. What is a Foundation + Functions
3. Requirements of an Ideal Foundation
4. Classification: Shallow vs Deep
5. Types of Shallow Foundations
6. Types of Deep Foundations
7. Bearing Capacity (added)
8. Settlement of Foundations (added)
9. Factors Affecting Selection
10. Loads on Foundation + Depth Criteria
11. Model Answers by Weightage
12. MCQs + Interview Qs
13. Part B -- Earth Pressure & Retaining Walls
14. What is Earth Pressure
15. Types of Earth Pressure
16. Rankine's Theory (+ cohesion, surcharge, water table)
17. Coulomb's Theory + Culmann's Method
18. Types of Retaining Walls
19. Stability of Retaining Walls
20. Model Answers by Weightage
21. MCQs + Interview Qs
22. Full Mock Test (25 Questions)
23. One-Page Summary Sheet

PART A

Foundation Engineering

5-Mark: Define, Differentiate, Requirements, Factors

10-Mark: Types with sketches, Selection criteria, Loads, Depth

1. What is a Foundation? (Definition -- 2/5 marks)

Exam favourite

Foundation is the lowest part of a structure that transfers the load of the superstructure safely to the supporting soil or rock, without causing excessive or differential settlement, and without shear failure of the soil.

Simple line: Foundation is the part of a building below ground that carries all structural loads and spreads them safely into the ground.

Functions of a Foundation (5 Marks)

1. Transfer loads (dead, live, wind, seismic) safely to the ground.
2. Prevent excessive settlement.
3. Prevent differential settlement between different parts of the structure.
4. Provide stability against sliding.
5. Provide stability against overturning.
6. Resist uplift forces (hydrostatic pressure, wind suction).
7. Protect the structure from moisture and groundwater effects.

Exam tip: write these as numbered/bulleted points -- examiners give marks per correct point, not for paragraph style.

2. Requirements of an Ideal Foundation (5 / 10 Marks)

Requirement	Meaning
Safe bearing capacity	Pressure transferred to soil must not exceed allowable bearing capacity.
Minimum settlement	Total settlement must stay within permissible limits.
Uniform settlement	Differential settlement between footings must be minimised.
Stability	Must resist sliding, overturning and uplift.
Economy	Must be safe AND cost-effective -- not necessarily the cheapest.
Durability	Must withstand environmental effects for the design life.

Mnemonic S S U S E D

S - Safe bearingS - Settlement (min)U - Uniform settlement S - StabilityE - EconomyD - Durability

3. Classification of Foundations

Foundations are broadly classified as Shallow (Depth < Width, roughly Df/B ≤ 1) and Deep (Df/B > 1, load carried to strata far below).

Shallow Foundation	Deep Foundation
Small depth, Df ≤ B	Large depth, Df > B (often much greater)
Lower cost	Higher cost
Easier / faster construction	More complex construction, needs machinery
Used when strong soil is near surface	Used when surface soil is weak
Moderate loads	Heavy loads
Examples: isolated, strip, combined, strap, raft	Examples: pile, pier, well/caisson

4. Types of Shallow Foundations (10 Marks -- draw sketches)

Fig 1 -- Types of shallow foundations (sketch outline for exam use)

Type	Supports	Used when
Isolated footing	One column	Columns well spaced, adequate soil bearing capacity -- most common type
Strip footing	Continuous wall / row of close columns	Load-bearing masonry construction
Combined footing	Two or more columns	Columns close together, or a column near a property boundary
Strap footing	Two isolated footings joined by a strap beam	One footing is eccentric due to boundary restriction
Raft (mat) foundation	All columns of the building on one slab	Low bearing capacity soil, closely spaced columns, differential settlement must be reduced

5. Types of Deep Foundations

Fig 2 -- Deep foundations transfer load down to firm strata

Type	Description	Suitable for
Pile foundation	Long slender members driven or bored; load carried by end bearing, skin friction, or both	Weak surface soils, heavy structures, bridges
Pier foundation	Large-diameter drilled shafts	Firm strata available at moderate depth
Well foundation (caisson)	Large hollow foundation sunk into the ground	Bridge piers, river crossings

Added -- commonly asked but missing from notes

Pile Capacity, Group Action & Negative Skin Friction

Ultimate pile capacity:

Static pile capacity formulaQu = Qp + Qs Qu = ultimate load capacity Qp = end (point) bearing resistance Qs = skin friction (shaft) resistance

Pile group efficiency: when piles are placed close together, their individual capacities overlap and the group capacity is usually LESS than the sum of individual pile capacities. This ratio is called group efficiency.

Negative skin friction: when the surrounding soil settles more than the pile (e.g. soft clay under new fill), the soil drags DOWN on the pile instead of supporting it. This adds extra load on the pile and must be added to the design load, not subtracted.

6. Bearing Capacity of Soil (added -- very high exam weightage)

Added topic

Bearing capacity notes were not detailed in the source file but this is one of the most frequently asked topics in the Loksewa foundation engineering paper, so it is added in full below.

Term	Meaning
Ultimate bearing capacity (qu)	Maximum pressure soil can carry before shear failure.
Net ultimate bearing capacity (qnu)	qu minus the original overburden pressure (qnu = qu - gamma x Df).
Safe / Allowable bearing capacity (qsafe)	qu divided by a factor of safety (usually 2.5 to 3); the pressure actually used in design.
Gross bearing capacity	Total pressure including the weight of soil above footing level.

Terzaghi's bearing capacity equation (strip footing)qu = c.Nc + q.Nq + 0.5.gamma.B.Ngamma c = cohesion of soil q = gamma x Df (overburden pressure at footing base) gamma = unit weight of soil B = width of footing Nc, Nq, Ngamma = Terzaghi's bearing capacity factors (depend only on angle of friction, phi)

Assumptions of Terzaghi's theory: shallow foundation (Df ≤ B), soil is homogeneous and isotropic, footing base is rough, failure occurs by general shear failure, soil behind footing level acts as a surcharge.

Factor of safety: qsafe = qu / FS, where FS is typically 2.5 to 3 for shallow foundations.

Methods to Determine Bearing Capacity (added)

Method	Use
Plate load test	Field test -- a steel plate is loaded and settlement is recorded to estimate safe bearing capacity directly at site.
Standard Penetration Test (SPT)	N-value from a split spoon sampler is correlated to bearing capacity, mainly used for sandy soils.
Static cone penetration test	Cone resistance is correlated with bearing capacity, mostly for soft to medium soils.
Analytical methods	Terzaghi's, Meyerhof's, Skempton's equations using c, phi and gamma from lab tests.

7. Settlement of Foundations (added)

Added topic

Total settlement of a foundation has three components:

Type	Cause	Typical soil
Immediate (elastic) settlement	Instant elastic deformation of soil under load, no drainage involved	Sands, and short-term response of clays
Consolidation settlement	Gradual squeezing out of pore water from saturated clay over time	Saturated clays -- the slowest and largest component
Secondary consolidation (creep)	Continued settlement after excess pore pressure has fully dissipated, due to plastic readjustment of soil particles	Highly organic soils, peat, soft clays

Differential settlement is more dangerous than uniform settlement because it causes cracking, tilting and distress in the structure, even when the total settlement is within limits.

8. Factors Affecting Selection of Foundation (10 Marks)

Very important subjective question

Group	Factors
Soil factors	Bearing capacity, settlement characteristics, soil type, groundwater level
Structural factors	Magnitude of load, type of structure, column spacing
Site factors	Property boundaries, adjacent buildings, excavation conditions
Economic factors	Construction cost, time, availability of materials and equipment

9. Loads on Foundation & Depth Criteria (10 Marks)

Load type	Examples
Vertical loads	Dead load, live load
Horizontal loads	Wind, earthquake, earth pressure
Uplift forces	Hydrostatic pressure, wind uplift
Dynamic loads	Machinery, vibrations, traffic

Criteria for Selecting Foundation Depth

• Reach competent (strong) soil.
• Avoid seasonal moisture / volume changes.
• Prevent frost effects, where applicable.
• Protect against scour, for bridges.
• Avoid erosion.
• Resist uplift.
• Ensure adequate bearing capacity.

Added -- Rankine's minimum depth of foundation

Rankine's formulaDf = (q / gamma) x [(1 - sin phi) / (1 + sin phi)]^2 Df = minimum depth of foundation q = safe bearing capacity of soil gamma = unit weight of soil phi = angle of internal friction of soil

Foundation Types Commonly Used in Nepal

Structure	Common foundation
Residential buildings	Isolated footing
Load-bearing masonry	Strip footing
Multi-storey buildings	Raft or pile foundation
Bridges	Well or pile foundation
Hydropower structures	Pile, raft or rock foundations depending on geology

10. Model Answers by Weightage

Q. Differentiate shallow and deep foundation. (5 Marks)

Answer using the comparison table in Section 3 above -- write it as a two-column table in the exam, that alone earns most of the marks. Add one line: "Shallow foundations rely on soil strength near the surface, while deep foundations transfer load to strong strata at greater depth through skin friction and/or end bearing."

Q. Explain the functions of a foundation. (5 Marks)

Answer: list the 7 functions from Section 1 as numbered points, one line each. Do not write paragraphs -- Loksewa markers award marks per distinct point.

Q. Explain different types of foundations with neat sketches. (10 Marks)

Answer structure: (1) one-line classification into shallow and deep, (2) sketch + 1-2 line description for isolated, strip, combined, strap, raft (use Fig 1), (3) sketch + description for pile, pier, well (use Fig 2), (4) one line each on when each type is used.

Q. Discuss the factors affecting the selection of a foundation. (10 Marks)

Answer: use the four-group table (soil, structural, site, economic) from Section 8. Expand each group with one example sentence for full marks -- e.g. "Soil factors: a site with low bearing capacity and high groundwater table favours a raft or pile foundation over isolated footings."

Q. Explain the requirements of an ideal foundation. (10 Marks)

Answer: use the SSUSED table in Section 2, expand each requirement with one explanatory sentence, and add a short concluding line that an ideal foundation balances safety, serviceability and economy together.

11. MCQs -- Part A

1. A raft foundation is generally used when:

• A. Soil has high bearing capacity
• B. Soil has low bearing capacity
• C. Only one column exists
• D. Soil is rock

Answer: B

2. A pile foundation is classified as:

• A. Shallow foundation
• B. Deep foundation
• C. Surface foundation
• D. Floating foundation

Answer: B

3. A combined footing supports:

• A. One column
• B. Two or more columns
• C. A wall only
• D. A bridge pier

Answer: B

4. The primary function of a foundation is to:

• A. Increase building height
• B. Transfer structural loads safely to the ground
• C. Improve concrete strength
• D. Reduce roof load

Answer: B

5. Which foundation is commonly used for bridge piers?

• A. Isolated footing
• B. Strip footing
• C. Well foundation
• D. Strap footing

Answer: C

6. (Added) Terzaghi's bearing capacity factors Nc, Nq, Ngamma depend mainly on:

• A. Unit weight of soil only
• B. Angle of internal friction (phi)
• C. Depth of footing only
• D. Water table position only

Answer: B

7. (Added) Negative skin friction on a pile:

• A. Increases pile capacity
• B. Adds extra downward load on the pile
• C. Has no effect on design
• D. Only occurs in dry sand

Answer: B

Interview Questions -- Part A

• Why is differential settlement more dangerous than uniform settlement?
• Why would you choose a raft foundation instead of isolated footings?
• Under what site conditions would a pile foundation be necessary?
• What factors control the depth of a foundation?
• Why is an economical foundation not necessarily the cheapest foundation?
• (Added) Why must negative skin friction be added to, not subtracted from, pile design load?

Memory Box -- Part A

• Foundation = transfers structural load safely to the soil.
• Shallow foundation: strong soil near surface. Deep foundation: weak surface soil, load goes deeper.
• Isolated = one column. Combined = two+ columns. Strap = two footings + rigid beam. Raft = one slab, many columns.
• Pile = end bearing + skin friction. Well foundation = common for bridge piers.
• qsafe = qu / FS. FS is usually 2.5 to 3.
• Settlement = Immediate + Consolidation + Secondary.

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PART B

Earth Pressure & Retaining Structures

5-Mark: Define, Types, Assumptions, Active vs Passive

10-Mark: Rankine's/Coulomb's theory, Stability analysis

1. What is Earth Pressure? (5 Marks)

Earth pressure is the lateral pressure exerted by soil on a retaining structure, due to its own weight and any external loads acting on it.

Unlike water pressure, earth pressure depends on: soil type, soil density, friction angle (phi), wall movement, and groundwater condition.

Acts on: retaining walls, basement walls, bridge abutments, sheet piles, tunnel linings.

If wrongly estimated, may cause: wall overturning, sliding failure, excessive settlement, structural cracking, collapse of the retaining wall.

2. Types of Earth Pressure (5 Marks)

Fig 3 -- At-rest, active and passive earth pressure states

Wall movement	Earth pressure
No movement	At-Rest (K0)
Away from soil	Active (Ka) -- minimum lateral pressure, soil expands slightly
Toward soil	Passive (Kp) -- maximum lateral pressure, soil is compressed

At-rest coefficient (Jaky's equation, normally consolidated soil)K0 = 1 - sin(phi)

Order to always rememberKp > K0 > Ka

3. Rankine's Earth Pressure Theory (10 Marks -- W.J.M. Rankine, 1857)

Favourite 5-mark question Assumptions:

1. Soil is homogeneous.
2. Soil is isotropic.
3. Backfill surface is plane.
4. Backfill is semi-infinite.
5. Wall is vertical.
6. Wall friction is neglected.
7. Failure surface is planar.
8. Soil obeys the Mohr-Coulomb failure criterion.

Active earth pressure coefficient (cohesionless soil)Ka = (1 - sin phi) / (1 + sin phi)

Passive earth pressure coefficient (cohesionless soil)Kp = (1 + sin phi) / (1 - sin phi)

Lateral pressure at depth hActive: sigma_a = Ka . gamma . h Passive: sigma_p = Kp . gamma . h gamma = unit weight of soil, h = depth

Pressure distribution for a horizontal backfill with no surcharge: pressure increases linearly with depth, distribution is triangular, and the resultant force acts at H/3 above the base.

Fig 4 -- Triangular active pressure distribution, resultant at H/3 from base

Added -- cohesive soil, surcharge & submerged backfill

The notes covered only cohesionless soil. The following extensions are frequently tested:

Active pressure for c - phi soil (cohesive backfill)sigma_a = Ka.gamma.h - 2.c.sqrt(Ka) A tension crack of depth zc = 2c / (gamma.sqrt(Ka)) forms near the top, where the net pressure is negative (soil pulls away from the wall).

Effect of uniform surcharge load (w) on backfill surfacesigma_a(surcharge) = Ka . w (constant with depth, added to the triangular soil pressure -> makes distribution trapezoidal)

Effect of submerged soil / water table behind wallBelow water table, use submerged unit weight gamma' = gamma_sat - gamma_water for the soil pressure, AND add full hydrostatic water pressure separately: sigma_w = gamma_water . h Total lateral pressure = earth pressure (with gamma') + water pressure

This is why weep holes are provided in retaining walls -- to drain water from behind the wall and prevent this extra hydrostatic pressure from building up.

4. Coulomb's Earth Pressure Theory (10 Marks -- Charles-Augustin de Coulomb, 1776)

Unlike Rankine, Coulomb's theory considers wall friction, an inclined backfill, and an inclined wall face -- so it is more general and often closer to real field conditions.

Added -- Coulomb's active pressure coefficient

Coulomb's Ka (general form)Ka = sin^2(alpha + phi) / [ sin^2(alpha) . sin(alpha - delta) . { 1 + sqrt( sin(phi + delta).sin(phi - beta) / (sin(alpha - delta).sin(alpha + beta)) ) }^2 ] alpha = angle of wall face with horizontal beta = angle of backfill slope with horizontal delta = angle of wall friction phi = angle of internal friction of soil For a vertical wall, horizontal backfill, and zero wall friction (delta = 0, alpha = 90, beta = 0), this equation reduces exactly to Rankine's Ka.

Rankine Theory	Coulomb Theory
Wall friction neglected	Wall friction considered
Vertical wall only	Inclined wall permitted
Horizontal or simple backfill	Inclined backfill allowed
Simpler calculations	More complex calculations
Analytical (equation based)	Can be solved analytically or graphically

5. Trial Wedge Theory & Culmann's Graphical Method

The soil behind the retaining wall is assumed to form a wedge. Failure occurs along the plane where driving and resisting forces are in equilibrium. This approach is used for more general earth pressure analyses where Rankine's simplifying assumptions do not hold.

Added

Culmann's method is a graphical application of the trial wedge (Coulomb) theory: several trial failure wedges are drawn, the weight of each wedge is plotted to scale, and the maximum resultant force from the force diagram gives the design active earth pressure. It is especially useful for irregular backfill surfaces or surcharge patterns that do not fit a clean formula.

6. Types of Retaining Walls (5 / 10 Marks)

Fig 5 -- Five common types of retaining walls

Type	Key feature
Gravity retaining wall	Resists earth pressure mainly by its own weight; masonry or mass concrete
Cantilever retaining wall	Reinforced concrete, uses cantilever action; economical for moderate heights
Counterfort retaining wall	Reinforced concrete with counterforts; suitable for high walls
Sheet pile wall	Thin steel, timber or concrete sheets driven into ground; waterfront structures, excavations
Reinforced earth wall	Soil reinforced with strips, geogrids or geotextiles; common in highway embankments

7. Stability of Retaining Walls (10 Marks)

A retaining wall must be checked against four failure modes:

Check	Requirement
Overturning	Wall must not rotate about its toe
Sliding	Wall must not slide horizontally along its base
Bearing capacity failure	Pressure under the base must not exceed allowable bearing capacity of soil
Excessive settlement	Settlement must remain within acceptable limits

Added -- factor of safety formulas

FOS against overturningFOS(overturning) = Sum of resisting moments about toe / Sum of overturning moments about toe Required minimum: 1.5 to 2.0

FOS against slidingFOS(sliding) = (W . tan(delta) + adhesion) / Horizontal earth pressure force Required minimum: 1.5

8. Methods to Increase Stability

• Increase the base width.
• Increase wall weight.
• Provide a shear key.
• Improve drainage behind the wall (weep holes, filter material).
• Reduce surcharge loads.
• Use reinforced backfill.
• Improve foundation soil.

Engineering Applications in Nepal

Retaining walls are widely used for: hill roads, bridge approaches, hydropower projects, river training works, basement construction, and landslide protection.

9. Model Answers by Weightage -- Part B

Q. Define earth pressure and its types. (5 Marks)

Answer: give the definition from Section 1, then list the three types (At-Rest, Active, Passive) with the wall-movement table from Section 2, ending with Kp > K0 > Ka.

Q. Explain Rankine's Earth Pressure Theory with assumptions and equations. (10 Marks)

Answer structure: (1) one line on who developed it and when, (2) list all 8 assumptions, (3) write Ka and Kp formulas, (4) write sigma_a = Ka.gamma.h and sigma_p = Kp.gamma.h, (5) sketch the triangular pressure distribution (Fig 4) and state the resultant acts at H/3 above base.

Q. Differentiate Rankine's and Coulomb's Earth Pressure Theories. (10 Marks)

Answer: reproduce the comparison table in Section 4, then add one line: "Rankine's theory is a special case of Coulomb's theory when wall friction is zero, the wall is vertical, and the backfill is horizontal."

Q. Explain the stability checks for a retaining wall. (10 Marks)

Answer: cover all four checks (overturning, sliding, bearing capacity, settlement) from Section 7 with the FOS formulas, then briefly mention methods to increase stability (Section 8) as the "remedy" part of the answer.

Q. Differentiate Active, Passive and At-Rest Earth Pressure. (5 Marks)

Answer: use the wall-movement table (Section 2) as a three-row table -- this is the fastest way to score full marks on this question.

MCQs -- Part B

1. Active earth pressure develops when:

• A. Wall moves toward soil
• B. Wall moves away from soil
• C. Wall does not move
• D. Soil is saturated

Answer: B

2. Passive earth pressure is:

• A. Minimum pressure
• B. Maximum pressure
• C. Equal to active pressure
• D. Zero

Answer: B

3. Rankine's theory neglects:

• A. Unit weight of soil
• B. Wall friction
• C. Soil friction angle
• D. Cohesion

Answer: B

4. The resultant active earth pressure acts at:

• A. H/2
• B. H/3 above the base
• C. H/4
• D. Top of the wall

Answer: B

5. Which retaining wall relies mainly on its own weight?

• A. Cantilever wall
• B. Sheet pile wall
• C. Gravity retaining wall
• D. Reinforced earth wall

Answer: C

6. (Added) Weep holes in a retaining wall are provided to:

• A. Increase wall weight
• B. Relieve hydrostatic water pressure behind the wall
• C. Reduce wall friction
• D. Increase passive pressure

Answer: B

7. (Added) In Coulomb's theory, if wall friction = 0, wall is vertical and backfill is horizontal, the equation reduces to:

• A. Terzaghi's equation
• B. Rankine's equation
• C. Jaky's equation
• D. Meyerhof's equation

Answer: B

Interview Questions -- Part B

• Why is passive earth pressure greater than active earth pressure?
• Why is Rankine's theory simpler than Coulomb's theory?
• Why are weep holes provided in retaining walls?
• Which retaining wall would you recommend for a hill road in Nepal, and why?
• What happens if drainage behind a retaining wall is poor?
• (Added) Why does a tension crack form near the top of a cohesive backfill, and why is it ignored in pressure calculations below that depth?

Memory Box -- Part B

• Earth pressure = lateral pressure exerted by soil on a retaining structure.
• Types: Active (Ka), At-Rest (K0), Passive (Kp). Order: Kp > K0 > Ka.
• Rankine: simple, neglects wall friction, vertical wall, horizontal backfill.
• Coulomb: considers wall friction, inclined wall, inclined backfill.
• Resultant active pressure acts at H/3 above the base.
• Stability checks: sliding, overturning, bearing capacity, settlement.
• Cohesive soil reduces active pressure near the top (tension crack); water table adds hydrostatic pressure.

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Full Mock Test -- 25 Questions (Chapter 10)

Attempt all questions first, then expand each answer to check yourself. Mix of Part A and Part B, in exam order.

1. What is the main function of a foundation?

To transfer structural loads safely to the ground without excessive or differential settlement.

2. Give the mnemonic for requirements of an ideal foundation.

S S U S E D -- Safe bearing, Settlement (minimum), Uniform settlement, Stability, Economy, Durability.

3. Name the five types of shallow foundations.

Isolated, strip, combined, strap, raft (mat).

4. Name the three types of deep foundations.

Pile, pier, well (caisson).

5. A pile transfers load by which two mechanisms?

End (point) bearing and skin friction.

6. What is negative skin friction?

Downward drag on a pile caused by surrounding soil settling more than the pile; it adds to the design load.

7. Write Terzaghi's bearing capacity equation for a strip footing.

qu = c.Nc + q.Nq + 0.5.gamma.B.Ngamma

8. What is the usual factor of safety for bearing capacity?

2.5 to 3.

9. Name the three components of total settlement.

Immediate (elastic), consolidation, secondary (creep).

10. List the four groups of factors affecting foundation selection.

Soil factors, structural factors, site factors, economic factors.

11. Which foundation is used for bridge piers in rivers?

Well foundation (caisson).

12. Define earth pressure.

Lateral pressure exerted by soil on a retaining structure due to its own weight and external loads.

13. What causes active earth pressure?

The wall moving away from the backfill, reducing lateral pressure to a minimum.

14. What causes passive earth pressure?

The wall moving toward the backfill, compressing soil and increasing lateral pressure to a maximum.

15. Write Jaky's equation for K0.

K0 = 1 - sin(phi)

16. Write Rankine's Ka and Kp formulas.

Ka = (1 - sin phi) / (1 + sin phi); Kp = (1 + sin phi) / (1 - sin phi)

17. Where does the resultant active pressure act, for a horizontal backfill with no surcharge?

At H/3 above the base of the wall.

18. How does cohesion change the active pressure equation?

sigma_a = Ka.gamma.h - 2.c.sqrt(Ka), which creates a tension crack near the top of the backfill.

19. What does Coulomb's theory consider that Rankine's does not?

Wall friction, an inclined wall face, and an inclined backfill surface.

20. What is Culmann's method used for?

A graphical trial-wedge method to find the maximum active earth pressure, useful for irregular backfills or surcharges.

21. Name the five types of retaining walls.

Gravity, cantilever, counterfort, sheet pile, reinforced earth.

22. List the four stability checks for a retaining wall.

Overturning, sliding, bearing capacity failure, excessive settlement.

23. What is the minimum FOS usually required against overturning and sliding?

Overturning: 1.5 to 2.0. Sliding: 1.5.

24. Why are weep holes provided?

To drain water from behind the wall and prevent additional hydrostatic pressure buildup.

25. State the relationship between the three earth pressure coefficients.

Kp > K0 > Ka, always.

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One-Page Summary Sheet (last-minute revision)

Topic	Key point to remember
Foundation	Lowest part of structure; transfers load to soil safely (SSUSED)
Shallow foundations	Isolated, strip, combined, strap, raft -- Df ≤ B
Deep foundations	Pile, pier, well -- Df > B, weak surface soil
Bearing capacity	qu = c.Nc + q.Nq + 0.5.gamma.B.Ngamma; qsafe = qu/FS
Settlement	Immediate + Consolidation + Secondary
Earth pressure types	Active (wall away, min), At-rest (no move), Passive (wall toward, max)
Coefficient order	Kp > K0 > Ka
Rankine's Ka, Kp	Ka = (1-sin phi)/(1+sin phi); Kp = (1+sin phi)/(1-sin phi)
Resultant location	H/3 above base (triangular distribution)
Rankine vs Coulomb	Rankine: no wall friction, vertical wall. Coulomb: wall friction + inclined wall/backfill
Retaining wall types	Gravity, cantilever, counterfort, sheet pile, reinforced earth
Stability checks	Overturning, sliding, bearing capacity, settlement

Blog note

Source notes covered foundation types, functions, classification, loads, Rankine's and Coulomb's earth pressure theories, and retaining wall types and stability. Bearing capacity theory, settlement types, pile group behaviour, cohesive-soil and submerged-soil earth pressure, and Coulomb's full equation were added above because they are regularly tested in the Loksewa 7th level paper but were missing from the original notes.