TOPIC 2

FOUNDATION & RETAINING WALL

TOPIC CONTENT: FOUNDATION & RETAINING WALL
2.1 SETTING OUT2.2 SHALLOW FOUNDATION 2.2.1 Soil Bearing Capacity 2.2.2 Pad Foundation 2.2.3 Strip Foundation 2.2.4 Raft Foundation 2.2.5 Shallow Foundation Failures 2.2.6 Work Procedures for Shallow Foundation2.3 DEEP FOUNDATION : PILE FOUNDATION 2.3.1 Driven Pile / Displacement Pile 2.3.2 Bored Pile / Replacement Pile 2.3.3 Sheet Pile2.4 RETAINING WALL 2.4.1 Gravity Wall 2.4.2 Cantilever Wall 2.4.3 Piling Wall 2.4.4 Anchored Wall 2.4.5 Counterfort / Buttress Wall 2.4.6 Mechanically Stabilized Earth (MSE) Wall

2.1 SETTING OUT

Setting out involves transferring details of the positioning of the building from a drawing onto the site. It requires a number of setting-out lines and pegs. The pegs are positioned away from construction activities in order to ensure that they remain undisturbed.
The major goal of setting out is to guarantee that the construction stays within the legal bounds. This guarantees that there won’t be any legal problems in the future over things like property lines and access rights.

PPT - STEPS IN SETTING OUT A BUILDING PowerPoint Presentation, free download - ID:544650STEPS IN SETTING OUT A BUILDING. MINIMUM SIZES FOR FOUNDATIONS. SETTING OUT CORNER PROFILES. MARKING OUT FOUNDATION AND WALL THICKNESSES. MARKING OUT ON THE GROUND FROM THE PROFILES. EXCAVATION OF FOUNDATION. SETTING OUT LEVELS FOR THE HEIGHT OF THE CONCRETE.

2.2 SHALLOW FOUNDATION

PURPOSE OF FOUNDATION:to transmit the combined, dead, imposed and wind loads on a building to the ground safely and without causing deflection or deformation of the building or movement/settlement of the ground that would impair the stability of the building and/or neighboring structures.

SHALLOW FOUNDATION

type of foundation that is characterized by its relatively shallow depth compared to its width. Shallow foundations are typically used when the upper soil layers have sufficient bearing capacity to support the load of the structure. These foundations transfer the building loads to the soil near the surface.

GENERAL CRITERIA FOR SHALLOW FOUNDATION:

For depth less than 3 meters (10 feet) below the ground surface, depending on the soil strength and structural requirement
Load from the structure is distributed over a wide area, directly to the soil beneath them to prevent excessive soil pressure, settlement and ensuring building remains stable
Appropriate when the upper layers of soil have sufficient bearing capacity
Cost-effective and easier to construct compared to deep foundations, as they do not required specialized construction equipment or tools.
Not suitable for structures with heavy loads or in areas where the soil has poor bearing capacity

2.2.1 SOIL BEARING CAPACITY

a measure of the ability of a soil to support loads applied to it. The bearing capacity of soil is influenced by various soil properties and conditions. The bearing capacity is typically expressed in terms of force per unit area (e.g., pounds per square foot or kilonewtons per square meter) that the soil can withstand without excessive settlement or failure. There are three main types of bearing capacity:

Ultimate Bearing Capacity (qult): This is the maximum pressure that can be applied to the soil without causing shear failure. It is the point at which the soil starts to fail and undergoes excessive deformation.
Allowable Bearing Capacity (qallow): To ensure a factor of safety, the ultimate bearing capacity is divided by a safety factor to determine the allowable bearing capacity. The safety factor accounts for uncertainties in soil properties, variations in loading conditions, and other factors.

FACTORS:

Soil Type: Different soil types have varying bearing capacities. Cohesive soils (such as clays) generally have lower bearing capacities compared to cohesionless soils (such as sands and gravels).
Moisture Content: The moisture content of the soil affects its cohesion and internal friction. Saturated soils often have reduced bearing capacity compared to well-drained soils.
Depth of Foundation: The bearing capacity can vary with the depth of the foundation. Shallow foundations may experience different soil conditions than deep foundations.
Foundation Size and Shape: The size and shape of the foundation also influence the bearing capacity. Larger foundations typically distribute loads over a larger area, resulting in lower bearing pressures.

IMPROVING SOIL BEARING CAPACITY:

Compaction: the use of dropped weight from certain height or vibratory probes to compact loose or granular soils, to increase soil density and increase bearing caapcity
Soil Stabilization: adding stabilizing agents/chemicals such as lime, cement, bitumen or asphalt to improve strength and stability
Grouting: injecting a cementitious or chemical grout into the soil can improve its strength and cohesion. This method is particularly useful in loose or sandy soils.
Deep Foundations: using driven piles, drilled piers, or caissons, can bypass weak or compressible surface soils and transfer loads to deeper, more competent soil layers.
Geosynthetics: reinforcing the soil with geosynthetic materials, such as geogrids or geotextiles, can improve its mechanical properties and increase bearing capacity.
Water Control: proper drainage and water control can prevent soil saturation, which is especially important for cohesive soils. Excess water can reduce the soil's strength and bearing capacity.
Surfacing: adding a stable and load-distributing layer on the surface, such as gravel or crushed stone, can improve the overall bearing capacity of the soil.

2.2.2 PAD FOUNDATION

(Spread Footing or Isolated footing)

support individual columns or pillars. It distributes the load from the structure over a larger area of soil, preventing excessive settlement and ensuring the stability of the building.
Pad foundations are suitable for relatively small structures with columns spaced at a considerable distance from each other.
The shape of a pad foundation are typically square or rectangle and are usually of reinforced concrete, casted over a mold or formwork.

LOAD DISTRIBUTION FOR PAD FOUNDATION

support the concentrated/point load from a column, transferred vertically through the foundation to the underlying soil.
the larger contact area between the foundation and the soil (the larger the surface of the pad), the lower the pressure will be on the soil.
ideally, uniformly distributed load prevents localized high pressure that leads to soil failure. Hence, the load on each pad foundation should uniform, at best.
depth of the foundation must be calculated to rest on the soil of good load bearing capacity (less than 3 meter above ground) to avoid settlement

Load distribution of building to Pad foundation

TYPES FOR PAD FOUNDATIONPAD FOOTING: a simple, flat, and uniform concrete slab that extends beyond the dimensions of the column. It is suitable for relatively light loads. Its thickness is constant and its shape can be circular, rectangular or square. It is economic and requires less excavation but its size is highly depended on the load and it is less resistant in lateral forces. STEPPED FOOTING: has a stepped or sloped configuration, which is used when the soil near the surface is not suitable for uniform bearing.SLOPED/TRAPEZOIDAL FOOTING: requires less concrete and reinforcements bars than pad footing. It is constructed cautiously in order to maintain a 45-degree inclination from all sides. The concrete mix used must be stiff in order to avoid sustaining viscous deformation. STRAP FOOTING: combined footing, consisting of two or more column footings connected by a concrete strap beam. It is used to help distribute the weight of either heavily or eccentrically loaded column footings to adjacent footings.A strap footing is often used in conjunction with columns that are located along a building’s property or lot line. Typically, columns are centered on column footings, but in conditions where columns are located directly adjacent to the property line, the column footings may be offset so that they do not encroach onto the adjacent property.This results in an eccentric load on a portion of the footing, causing it to tilt to one side. The strap beam restrains the tendency of the footing to overturn by connecting it to nearby footings.

Types of Pad Foundation

Strap Footing

Column Footing Size For Different Storey✔ Column footing size is a critical factor in the design of any building or structure. The size of the footing must be sufficient to support the column's load

2.2.3 STRIP FOUNDATION

(Continuous footing)

continuous strip of concrete that supports the load from the structure and distributes it to the underlying soil. Strip foundations are generally used for load-bearing walls and are particularly suitable for buildings with relatively light loads and uniform soil conditions with good bearing capacity.
Construction of strip footing is quick and straightforward, requiring only the most straightforward formwork construction and rebar installation, making it the most cost-effective type of foundation for any constructionStrip footing may not be suitable on slopes or where retaining walls are required, due to higher possibility of settlementStrip foundation is also used when pad foundations for number of columns in line are so closely spaced that the distance between the pads is approximately equal to the length of the side of pads.

LOAD DISTRIBUTION FOR STRIP FOUNDATION

support the load of a bearing wall, transferred vertically through the foundation to the underlying soil.
the larger contact area between the foundation and the soil (the larger the width of the strip footing), the lower the pressure will be on the soil.
ideally, uniformly distributed load prevents localized high pressure that leads to soil failure. By distributing the loads evenly, engineers aim to minimize differential settlement.
depth of the foundation must be calculated to rest on the soil of good load bearing capacity (less than 3 meter above ground) to avoid settlement

Load Distribution Pad Footing VS Strip Footing

TYPES FOR STRIP FOUNDATION
SHALLOW/TRADITIONAL STRIP FOUNDATION: used for relatively light structures. It consists of a continuous strip of concrete that supports the load-bearing walls. Shallow strip foundations are suitable for buildings with low to moderate loads and stable soil conditions.
DEEP STRIP FOUNDATION: designed to reach deeper soil layers with better bearing capacity. This type is used when the upper layers of soil are not suitable for supporting the loads. Deep strip foundations may be required in areas with expansive or compressible soils. When used on soil with good bearing capacity, this is a cheaper option as it doesn't require too big an excavated trench.
WIDE STRIP FOUNDATION: where the soil has lower bearing capacity, engineers may opt for a wider strip foundation to spread the loads over a larger area.
STEPPED STRIP FOUNDATION: used on sloping site to follow the ground line, primarily to reduce the amount of excavation work.

Shallow Strip VS Deep Strip Foundation

WIDE STRIP FOUNDATION

STEPPED STRIP FOUNDATION

RAFT FOUNDATION

2.2.4 RAFT FOUNDATION

(Mat foundation)

continuously covers the entire footprint of a building. It's a large, solid slab of reinforced concrete that supports and distributes the loads from the structure to the underlying soil. Raft foundations are commonly used when the soil has poor bearing capacity or when the loads from the structure are too heavy for individual footings, particularly for multi-story buildingsThe primary function of a raft foundation is to distribute the loads from the structure evenly to prevent differential settlement and bridge over soft spots within the soil. This is achieved by spreading the loads over a larger area of soil.The construction process for a raft foundation involves excavating the entire area where the building will be located and then pouring a thick layer of concrete to form the slab. Reinforcement is added within the concrete to provide structural strength. This exercise can be more costly compared to other foundation. Raft foundations can be designed to include provisions for basements, providing additional space below ground level. This is common in residential and commercial buildings

TYPES OF RAFT FOUNDATION

FLAT SLAB RAFT FOUNDATIONideal to use when the walls and columns are evenly spaced at small intervals and have to carry relatively small loads. The slab is reinforced in both directions with a steel mesh. The maximum measurement of the concrete slab is 300mm

TWO-WAY BEAM & SLAB RAFT FOUNDATIONthe beams are cast perpendicularly and monolithically with the raft slab connecting the walls and the columns. It is well suited if the columns are spread at a larger distance and carry unequal amounts of load.

PILED RAFT FOUNDATIONused when the water table is high and soil found at a shallow depth is extremely compressed. Piles are placed below the raft to reduce settlement and control the buoyancy effect. The Piles raft foundation increases the load-bearing capacity of the foundation and hence, it is ideal for high-rise buildings.

CELLULAR / RIGID FRAME MAT RAFT FOUNDATIONthe foundation walls act as a deep beam where columns carry extremely heavy loads and the connecting beams exceeds 90cm depth. Here two concrete slabs are placed, one on top of another and connected with foundation walls in both directions and thus forms a cellular raft foundation. This type of raft is very rigid and is economical when the required slab thickness is very high.

THICKENED PLATE RAFT FOUNDATIONthe thickness of the slab is increased under the walls and the columns because the extremely heavy loads from the columns bring diagonal shear and negative bending moments onto the slab. Another way to support the heavy loads is to provide a pedestal below the column and you don’t even have to increase the thickness of the slab with this method.

Shallow Foundation failures

2.2.5 SHALLOW FOUNDATION FAILURES

REASONS:

Unequal settlement of the sub-soil.
- caused by the non-uniform nature of soil throughout foundation, non-uniform loading throughout all parts of foundation & eccentricity of load.
- causes the development of cracks in the superstructure, which may ultimately lead to its collapse.
Change in water table content, causing horizontal movement
- increase in water table content due to heavy rain or seasonal variation may leads to swelling of the soil and lowers the bearing capacity of the soil
- decrease in water table content due to transpiration from nearby trees/shrubs, miscalculation of foundation depth lying over porous soil and extreme dry weather causes shrinkage to the soil, leading to soil cracks
Lateral escape of the soil from below the foundation. This is particularly relevant for foundations on hillsides or areas prone to erosion.
Adjacent excavation or construction altering soil conditions, causing settlement
Natural disaster like earthquakes, flood or soil erosion may change the bearing capacity of the soil, beyond the calculated design
Foundation material deterioration due to environmental exposure.
- Exposure to corrosive environments, such as in coastal areas, can lead to the corrosion of steel reinforcement within the foundation, compromising its strength and integrity.
Poor Design & Construction Practices:
- Miscalculation of structure loading or foundation depth; and inadequate construction techniques, such as improper compaction of soil, insufficient curing of concrete, and inadequate reinforcement, can compromise the integrity of the foundation. Adding additional stories, rooms or heavy equipment to a structure without reinforcing the foundation may lead to overload.

2.2.6 WORK PROCEDURES FOR SHALLOW FOUNDATION

1. Site Clearance2. Setting out3. Excavation & Soil Compaction4. Lean Concreting5. Formwork installation6. Rebar Installation7. Concreting8. Vibration & Consolidation9. Concrete curing10. Formwork removal11. Waterproofing (if needed)12. Backfilling13. Compacting the backfill

1. SITE CLEARANCEto remove obstacles, vegetation, and any existing structures that may interfere with the construction process. -please refer to notes on Site Preparation for further explanation

2. SETTING OUTtransferring details of the positioning of the building from a drawing onto the site using a number of setting-out lines and pegs.
-please refer to notes on Setting Out (on this same page) for further explanation

3. EXCAVATIONremoval of earth, rock, or other materials from a site to create space for foundations, utilities, basements, or other structures -please refer to notes on Site Excavation for further explanation

4. FORMWORK INSTALLATIONformwork is used as a mould for a structure in which fresh concrete is poured to harden. Formwork must be able to withstand both dead and live load of the structure during the entire process of concreting up until full concrete curing.

5. LEAN CONCRETINGto provide the uniform surface to the foundation concrete and to prevent the direct contact of foundation concrete with the soil, plus avoiding concrete loosing water-cement ratio during concreting work.Lean Concrete: A concrete with cement content less than about 10 % of the total contents

6. REBAR INSTALLATIONRebar, short for “reinforcing bar” or “reinforcement bar”, is a metal bar that is used to help increase the tensile strength of concrete. As a result, it helps concrete structures withstand tensile, bending, torsion, and shearing loads

install spacer block onto lean concrete within formwork
install foundation rebar made of two-way perpendicular rebar according to the specified spacing. Tighten the two-way rebar together.
install column starter rebar, tighten to the foundation rebar
For bigger foundation, install form tie or strut to strengthen the formwork or prevent formwork failure and concrete bulging.

7. CONCRETINGPour the concrete into the formwork, ensuring it reaches all areas uniformly. Use concrete with the appropriate mix design for strength and durability (RATIO - cement : sand : aggregate - 1:3:6 for foundation). The pouring process may involve the use of a concrete pump or ready-mix concrete delivery.

8. VIBRATION & CONSOLIDATIONUse vibrators to eliminate air pockets and ensure proper consolidation of the concrete. Proper consolidation enhances the strength and integrity of the foundation

9. CONCRETE CURINGprocess that prevents the recently poured concrete from drying too rapidly. This is to ensure that the concrete will acquire the desired chemical and mechanical properties. If the concrete drying process is uncontrolled, the concrete mix will not acquire the desired binding strength between the constituents.

10. FORMWORK REMOVALFormwork should only be dismantled under supervision to ensure sufficient and timeliness of setting/curing concrete.

11. WATERPROOFING (if needed)Apply waterproofing materials to the foundation walls to prevent water infiltration. This is especially important for below-grade foundations to protect against moisture-related issues. Normally, a type of waterproof liquid sealant is painted or sprayed onto the foundation surface before the backfill.

12. BACKFILLINGBackfill the excavated area around the foundation with suitable material. Proper backfilling helps support the foundation and provides drainage away from the structure.

13. COMPACTING THE BACKFILLCompaction is needed to reduce the amount of soil settlement that occurs with time. Be careful when compacting backfill. Some compactors are powerful enough to damage the foundation.

2.3 DEEP FOUNDATION : PILE FOUNDATION

DEEP FOUNDATION is type of foundation that is constructed at a considerable depth below the ground surface to transfer the loads of a structure to deeper, more competent layers of soil or rock, due to weak upper soil conditions, the presence of compressible or expansive soils, or the need to reach a more stable stratum.GENERAL CRITERIA FOR DEEP FOUNDATION:

- 1. constructed at depths greater than 3 meters (10 feet) below the ground surface. The exact depth depends on the soil conditions and the design requirements of the structure.
  2. Materials used can be of:
    - Concrete Piles: Reinforced or prestressed concrete piles are common and can be precast or cast in place.
    - Steel Piles: Steel piles are often used in situations where high load-bearing capacity is required.
    - Timber Piles: Timber piles are less common today but are still used in specific applications.
  3. Commonly used for tall buildings, bridges, waterfront structures and in areas with challenging soil conditions, like earthquake or flood-prone zones.
  4. Used in sites with poor upper soil bearing capacity, offering ability to transfer loads to more competent strata, reducing the risk of settlement and ensuring stability of the structure
  5. Used in situation requiring resistance to horizontal forces (weak soil conditions) and also uplifting forces (very strong wind and sea wave/current)
  6. More expensive and time-consuming to install compared to shallow foundations. The design and construction of deep foundations require careful consideration of soil conditions, load requirements, and other factors, including use of heavy-duty equipment.

PILE FOUNDATION are principally used to transfer the loads from superstructures, through weak, compressible strata or water onto stronger, more compact, less compressible and stiffer soil or rock at depth, increasing the effective size of a foundation and resisting horizontal loads. They are typically used for large structures, and in situations where soil is not suitable to prevent excessive settlement.
Situations requiring Pile Foundation:

Groundwater table is high.
Heavy and non-uniform loads from superstructure are imposed.
Other types of foundations are costlier or not feasible.
Soil at shallow depth is compressible.
Possibility of scouring (erosion), due to its location near the river bed or seashore, etc.
When there is a canal or deep drainage systems near the structure.
Soil excavation is not possible up to the desired depth due to poor soil condition.
When it becomes impossible to keep the foundation trenches dry by pumping or by any other measure due to heavy inflow of seepage.

TYPES OF LOAD TRANSFER ACTION ON PILE FOUNDATION

2.3.1 DRIVEN PILE / DISPLACEMENT PILE

Driven piles are pre-cast or cast in-situ without soil removal
When these piles are driven into the granular soils, they displace the equal volume of soil helping with the compaction of soil around the sides of piles and results in the densification of soil, thus increasing its bearing capacity
This construction technique can be very noisy
Driven and cast in-situ concrete piling is performed by driving a casing closed at its bottom by a disposable or retrievable plate using diesel or hydraulic hammer. Once driving is completed, the steel rebar is installed and concrete is poured into the casing. The casing is then extracted by means of a casing oscillator

Materials for Pre-Cast Piles

DRIVEN PRE-CAST PILES (Concrete/Steel/Timber)

DRIVEN + CAST IN-SITU CONCRETE PILES

HELICAL SCREW PILES

a type of pile foundation with a helix near the pile toe so that the piles can be screwed into the ground. A screw pile may have more than one helix depending on the usage and the ground conditions.
The installation is very quiet, minimal dust and vibration, light-weight, does not involved replacement of spoil, requires non-specialised equipments and can be used in settings where water table is present and close to ground surface.
Helical screw piles is not suitable for rock soil type and the loadbearing capacity is limited.

2.3.2 BORED PILE / REPLACEMENT PILE

the removal of spoil/soil forms a hole for a reinforced concrete pile which is poured in situ.
used primarily in cohesive subsoils for the formation of friction piles and when forming pile foundations close to existing buildings.
popular in urban areas as there is minimal vibration, where headroom is limited, where there is no risk of heave, and if there is a need to vary the length of the piles.

CONTINUOUS FLIGHT AUGER (CFA) PILES

Continuous flight auger piles are constructed rotating an auger string into the ground by injecting concrete under a minimum pressure through the hollow stem of the auger. The soil is replaced with concrete in one continuous movement as the auger is withdrawn. After the pile head is cleared of debris, steel reinforcement is plunged into the pile concrete.The technique requires no additional ground support, such as casing or drilling fluids, because the bore is self-supporting as the auger is rotated into the ground and the concrete supports the bore after extraction. Depth is up to 29mBest and most effective solution when piling is required close to existing buildings, or in built-up areas because this piling approach is virtually vibration free, and it has low noise levels.

ROTARY BORED PILES

constructed by rotating a casing into the ground to support poor or granular ground and then removing the pile bore using an auger, bucket or coring unit attached to a telescopic Kelly bar. Once the bore is fully cleaned out to design depth, the pile concrete is tremied into the bore and the casing is extracted leaving a finished pile. Typically, pile reinforcement is cast into the pile during concreting. Depth up to 80m
Rotary piling can be employed in almost all ground conditions from soft ground supported by temporary casing through to high grade very strong rock cored in to open-hole techniques.

MICRO PILES / MINIPILES

very similar in nature to bored piles however on a much smaller scale in terms of pile diameter and depth. Micropiles are generally in the order of 150 to 300mm (6 to 12 inch) diameter whereas bored piles are 300mm and above
A steel casing is first pressed into the soil to the required depth. Soil is then removed using a flushing method. This method involves introducing pressurised water to the soil then the water-soil mixture is literally sucked out of the casing.
Concrete is then placed in the hole using the tremie method. As the concrete placement is occurring from bottom to top, the steel casing is removed at the same time.
Reinforcement is then plunged into the still wet concrete. Due to the small diameter of the pile, instead of a full reinforcement cage being installed, it is usually a single centralised bar.
Advantages of Micro piles: Can be installed in confined spaces, relatively quiet installation with low vibration and minimal spoil material. Ideal for providing additional strength to existing foundation.
Not suitable for large load, large length, limited application in shallow water table setting

2.3.3 SHEET PILE

interlocked steel sheets forming a wall that retain soil and are installed using vibratory and vibration-free rigs
Sheet pile walls have been used to support excavations for below-grade parking structures, basements, pump houses, and foundations, to construct cofferdams, and to construct seawalls and bulkheads.
Advantages of Sheet piles:

A sustainable option as made of recycled steel and the piles can often be reused
Available in numerous combinations of size and weight
Immediate barrier to prevent soil loss and sloughing during excavation
Permanent sheet piles are designed to provide long service life

2.4 RETAINING WALL

A retaining wall is a structure designed to hold back or support the lateral pressure of soil, especially when there is a change in ground elevation that would otherwise cause the soil to slope and potentially erode. These walls are commonly used in landscaping, civil engineering, and construction projects to create level surfaces on sloped terrain, prevent soil erosion, and provide stability to structures built on or near slopes.
Key Components of a Retaining Wall:

Backfill: The soil or material that is retained by the wall. The retaining wall is designed to resist the lateral pressure exerted by the backfill.
Facing: The visible front surface of the retaining wall, which can be constructed using various materials such as concrete, stone, brick, wood, or modular retaining wall blocks. The facing enhances the aesthetics and structural stability of the wall.
Drainage System: To prevent the buildup of water pressure behind the wall, drainage provisions are often incorporated. This may include drainage pipes, gravel backfill, and weep holes to allow water to escape.

2.4.1 GRAVITY WALL

Gravity retaining wall depends only on its own weight to resist lateral earth pressure. Generally, gravity retaining wall is massive because it requires significant gravity load to counter act horizontal soil pressure.
While designing gravity retaining wall, sliding, overturning, and bearing forces shall be taken into consideration. It can be constructed from different materials such as stone, concrete and masonry units.
A gravity retaining wall is generally constructed up to a height of 3 m.

CRIB WALLA crib wall, concrete or timber, is a gravity retaining structure that consists of interlocking concrete or timber elements. Each crib unit is filled with compacted granular soil. It is suitable for supporting planter areas, but it is not recommended for support of slopes or structures.

BIN WALLa gravity retaining wall system made from 10 foot wide corrugated steel panels which are easily bolted together, then backfilled with soil. It protects against shore or bank erosion, provides support and holds back encroaching slopes. This system can also be used for breakwaters and protective blast walls.

GABION WALLGabion walls consist of baskets made of galvanized steel mesh or PVC coated wire mesh. The baskets are filled with durable rock ranging in size from 4 to 8 inches.
Gabion walls are suitable for retained heights typically up to about 10m. Box gabions are normally available in 0.5 m modules of length 2 m to 6 m, width 1 m to 2 m, and in depths of 0.3 m, 0.5 m,and 1 m.

KEYSTONE WALLKeystone created the mortar less segmental retaining wall market with its patented interlocking modular design. This wall are able to resist lateral pressure with their unit weight and deep embedment shape.

RUBBLE WALLThe wall use of undressed, rough stone, generally in the construction of walls. Its is suitable for smaller retaining wall especially where the finished appearance is important. Rubble walls are suitable for retained heights typically up to 1.5 m (in the case of a simple stem wall) or greater heights (in the case of stepped or buttressed walls)

RUBBLE PITCHING WALLPitching shall consist of irregular stones selected to roughly fit together and placed on bedding material having a mean thickness of 100 mm. Stone pitching are generally used as erosion protection

2.4.2 CANTILEVER WALL

These walls have a base slab and a stem that extends back into the retained soil. The weight of the wall and the soil on the base provide stability.
The base is divided into two parts, namely the heel and toe. The heel is the part of the base under the backfill and the toe is the other part of the base. It uses much less concrete than monolithic gravity walls, but requires more design and careful construction. It can be formed on site or precast in a factory.
Cantilever retaining walls are constructed of reinforced concrete.

PRE-CAST CANTILEVER WALL

2.4.3 PILING WALL

These walls are made of interlocking steel, vinyl, or wood sheets/pile driven into the ground to form a barrier. They are often used in waterfront or limited-space applications.

SHEET PILE WALLInterlocking sheet piles are driven into a slope or excavation to support the soft soils collapse from higher ground to lower ground.

BORED PILE WALLbuilt by assembling a sequence of bored piles, proceeded by excavating away the excess soil. Depending on the project, the bored pile retaining wall may include a series of earth anchors, reinforcing beams, soil improvement operations and shotcrete reinforcement layer.

SOLDIER PILE WALLSoldier Piles are steel H piles that are vertically driven or drilled into the earth at regular intervals prior to excavation. As excavation progresses in stages, horizontal lagging in the form of timber or precast concrete is added behind the flanges to create the Soldier Pile and Lagging Wall.

COFFERDAMTemporary structures designed to keep water and soil out of the excavation area, allowing construction to take place in the dry

2.4.4 ANCHORED WALL

For the construction of high retaining walls, deep cable rods or wires are driven deep sideways into the earth, then the ends are filled with concrete to provide an “anchor”. These are also known as tiebacks.
These types of retaining walls typically consist of the same elements as the non-gravity cantilevered walls but derive additional lateral resistance from one or more tiers of anchors. The anchored walls are typically used in the cut situation, in which the construction proceeds from the top to the base of the wall.

2.4.5 COUNTERFORT / BUTTRESS WALL

Counterfort walls are cantilever walls strengthened with counter forts monolithic with the back of the wall slab and base slab. The counter-forts act as tension stiffeners and connect the wall slab and the base to reduce the bending and shearing stresses. To reduce the bending moments in vertical walls of great height, counterforts are used, spaced at distances from each other equal to or slightly larger than one-half of the height Counter forts are used for high walls with heights greater than 8 to 12 m.
A buttress wall is more economical when compared to a counter-fort retaining wall. Buttress walls are not much preferred due to the provision of buttresses in the wall.
These buttresses reduce the clearance on the front side of the wall. The buttresses act as compression members, supporting the stem and reducing the bending moment in it. It provides support to the toe slab and reduces bending moment in it.

2.4.6 MECHANICALLY STABILIZED EARTH (MSE) WALL

These types of retaining walls normally include a facing element and a reinforcement element embedded in the backfill behind the facing. The facing element can be concrete, segmental block or panel, or steel wire mesh. The reinforcement element can be either geo synthetic (geo textile, geo grid) or metallic (strip, grid, wire mesh). These types of retaining walls are often used to support fills and when substantial total and differential settlement are anticipated

NEHEMIAH WALLNehemiah® Wall is a type of reinforced soil system based on Anchored Earth concept whereby the mode of stress transfer from the back-fill to the reinforcement is by passive resistance in addition to friction. This System is reinforced by galvanised steel bars and anchored by precast concrete blocks. The facing is vertical consisting of modular hexagonal shaped concrete panels interlocked together.
https://www.nehemiah-grp.com/nh-nehemiah-wall

ANCHORSOL WALL
https://www.anchorsolwall.com/documentation.html

RE WALLhttps://reinforcedearth.com.my/retain/reinforced-earth-terrawall/

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