A retaining wall is a structure that holds back soil or rock from a building, structure or area. Retaining walls prevent down slope movement or erosion and provide support for vertical or near-vertical grade changes. A retaining wall is a structure which holds back material on one side. These are particularly useful where there is a change in level within a restricted area and insufficient space for banks of appropriate slope. They can also be used to good effect where ground conditions are such that a sloping bank would slump or fail or where there is an awkward junction between adjacent free- standing walls. Cofferdams and bulkheads, structures that hold back water, are sometimes also considered retaining walls. Retaining walls are generally made of masonry, stone, brick, concrete, vinyl, steel or timber. Once popular as an inexpensive retaining material, railroad ties have fallen out of favor due to environmental concerns. They also decompose over time. They also can be used as a barrier on a beach that stops the earth behind the sand eroding and collapsing. Segmental retaining walls have gained favor over poured-in-place concrete walls or treated-timber walls. They are more economical, easier to install and more environmentally sound. The most important consideration in proper design and installation of retaining walls is that the retained material is attempting to move forward and down slope due to gravity. This creates a lateral earth pressure behind the wall which depends on the angle of internal friction (phi) and the cohesive strength (c) of the retained material, as well as the direction and magnitude of movement the retaining structure undergoes. Lateral earth pressures are typically smallest at the top of the wall and increase toward the bottom. Earth pressures will push the wall forward or overturn it if not properly addressed. Also, any groundwater behind the wall that is not dissipated by a drainage system causes an additional horizontal hydraulic pressure on the wall.

Note: Retaining walls are costly structures that are clearly artificial: a sloping earth bank of gradient to match local landforms that can carry locally characteristic vegetation is normally preferred in rural locations.

A generic structure that is employed to restrain a vertical-faced or near-vertical-faced mass of earth. The earth behind the wall may be either the natural embankment or the backfill material placed adjacent to the retaining wall. Retaining walls must resist the lateral pressure of the earth, which tends to cause the structure to slide or overturn.

There are several types of retaining walls. A gravity wall is typically made of concrete and relies on its weight for stability (illus. a). The mass of the structure must be sufficient to develop enough frictional resistance to sliding, and the base or footing of the structure must be wide enough to develop sufficient moment to resist overturning earth forces. A cantilever retaining wall (illus. b) gains a larger effective mass by virtue of the soil placed on the horizontal cantilevered section of the wall. Reinforced counterforts are spaced along the wall to increase its strength. A variation of the gravity retaining wall is the crib wall (illus. c) is usually constructed of prefabricated interlocking concrete units. The crib is then filled with soil before the backfill adjacent to the crib is placed. Bulkhead retaining walls (illus. d) consist of vertical sheet piling that extends down into the soil and is stabilized by one or more tiebacks and anchors periodically spaced along the structure. The sheet piling may be made of reinforced concrete, steel, or aluminumConstruction & design

Retaining walls are often used in the marine environment, where they separate the retained soil from the water. Gravity walls (known as seawalls) can be constructed where strong wave and current forces are exerted on the wall. Bulkheads are more commonly found in sheltered areas such as harbors and navigation channels

Retaining walls carry a substantial amount of loading from the retained material. This loading is increased by water building up in the ground behind the wall, so drainage is essential (by weep-holes or by French drainage behind the wall). As a rule of thumb, when building a retaining wall its thickness should be at least half the height of the retained ground

Figure 1 a) gravity wall, b)cantiliver wall, c) crib wall, d) bulk head

Retaining walls should be properly designed and constructed under the supervision of a chartered civil engineer, especially if:

  • they are over 1 metre high

  • they support land carrying structures or trees

  • they support land outside your ownership

  • there are concerns about ground conditions (including hydrology)

New retaining walls should be carefully designed to respect local distinctiveness: in Harrogate District, retaining walls of local millstone grit are a traditional and characteristic feature of the upland towns and villages

Retaining Wall Types:

1. Cantilevered Concrete Walls

2. Crib Walls (Gravity)

3. Mechanically Stabilized Earth Walls

4. Soil Nail Walls

5. Tieback Walls (Anchored)

6. Sheet piling

7. Soil-strengthened

7.1 Gabion meshes

7.2 Mechanical stabilization

1. Cantilevered Concrete Walls

Prior to the introduction of modern reinforced-soil gravity walls, cantilevered walls were the most common type of taller retaining wall. Cantilevered walls are made from a relatively thin stem of steel-reinforced, cast-in-place concrete or mortared masonry (often in the shape of an inverted T). These walls cantilever loads (like a beam) to a large, structural footing; converting horizontal pressures from behind the wall to vertical pressures on the ground below. Sometimes cantilevered walls are butressed on the front, or include a counterfort on the back, to improve their stability against high loads. Buttresses are short wing walls at right angles to the main trend of the wall. These walls require rigid concrete footings below seasonal frost depth. This type of wall uses much less material than a traditional gravity wall.

2. Crib Walls (Gravity)

Gravity walls depend on the weight of their mass (stone, concrete or other heavy material) to resist pressures from behind and will often have a slight ‘batter’ setback, to improve stability by leaning back into the retained soil. For short landscaping walls, they are often made from mortarless stone or segmental concrete units (masonry units) Dry-stacked gravity walls are somewhat flexible and do not require a rigid footing in frost areas.

Earlier in the 20th century, taller retaining walls were often gravity walls made from large masses of concrete or stone. Today, taller retaining walls are increasingly built as composite gravity walls such as: geosynthetic or with precast facing; gabions (stacked steel wire baskets filled with rocks), crib walls (cells built up log cabin style from precast concrete or timber and filled with soil) or soil-nailed walls (soil reinforced in place with steel and concrete rods).

3. Mechanically Stabilized Earth Walls.

Mechanically stabilized earth walls are retaining walls constructed in fill situations and consist of horizontal soil reinforcing elements and a facing to prevent erosion.

Mechanically stabilized earth, also called MSE, is soil constructed with artificial reinforcing via layered horizontal mats (geosynthetics) fixed at their ends. These mats provide added internal shear resistance beyond that of simple gravity wall structures. Other options include steel straps, also layered. This type of soil strengthening usually needs outer facing walls to affix the layers to and vice versa.

The wall face is often of precast concrete units[2] that can tolerate some differential movement. The reinforced soil’s mass, along with the facing, then acts as an improved gravity wall. The reinforced mass must be built large enough to retain the pressures from the soil behind it. Gravity walls usually must be a minimum of 50 to 60 percent as deep or thick as the height of the wall, and may have to be larger if there is a slope or surcharge on the wall.

4. Soil Nail Walls.

Soil nailing is a technique in which soil slopes, excavations or retaining walls are reinforced by the insertion of relatively slender elements – normally steel reinforcing bars. The bars are usually installed into a pre-drilled hole and then grouted into place or drilled and grouted simultaneously. They are usually installed untensioned at a slight downward inclination. A rigid or flexible facing (often sprayed concrete) or isolated soil nail heads may be used at the surface.

Soil nail walls are retaining walls which are built from the top downwards in cut situations where the soil has enough apparent cohesion that it can stand up on its own during construction. The walls consist of soil nails spaced approximately 5 ft. (1.5 m) on center with a shotcrete facing which is often covered with a permanent cast-in-place concrete facing. Soil nailing is not appropriate at sites consisting of clays which creep, clean sands which will not stand up or areas below the water table.

5. Tieback Walls (Anchored)

This version of wall uses cables or other stays anchored in the rock or soil behind it. Usually driven into the material with boring, anchors are then expanded at the end of the cable, either by mechanical means or often by injecting pressurized concrete, which expands to form a bulb in the soil. Technically complex, this method is very useful where high loads are expected, or where the wall itself has to be slender and would otherwise be too weak.

Tieback walls are retaining walls which are built from the top downwards in cut situations and consist of prestressed tieback anchors locked against either a shotcrete facing or soldier piles. The tiebacks may be anchored against a shotcrete facing when the soil has enough apparent cohesion that it can stand up on its own during construction. The alternate tieback system incorporates tiebacks anchored against soldier piles with some sort of whaler system.

6. Sheet piling.

Sheet pile walls are often used in soft soils and tight spaces. Sheet pile walls are made out of steel, vinyl, fiberglass or plastic sheet piles or wood planks driven into the ground. Structural design methods for this type of wall exist but these methods are more complex than for a gravity wall. As a rule of thumb; 1/3 third above ground, 2/3 below ground. Taller sheet pile walls usually require a tie-back anchor “dead-man” placed in the soil some distance behind the wall face, that is tied to the wall face, usually by a cable or a rod. Anchors must be placed behind the potential failure plane in the soil.Proper drainage behind the wall is critical to the performance of retaining walls. Drainage materials will reduce or eliminate the hydrostatic pressure and increase the stability of the fill material behind the wall, assuming that this is not a retaining wall for water.

7. Soil-strengthened.

A number of systems exist that do not simply consist of the wall itself, but reduce the earth pressure acting on the wall itself. These are usually used in combination with one of the other wall types, though some may only use it as facing (i.e. for visual purposes).

7.1 Gabion meshes.

This type of soil strengthening, often also used without an outside wall, consists of wire mesh ‘boxes’ into which roughly cut stone or other material is filled. The mesh cages reduce some internal movement/forces, and also reduce erosive forces.

7.2 Mechanical stabilization.

Mechanically stabilized earth, also called MSE, is soil constructed with artificial reinforcing via layered horizontal mats (geosynthetics) fixed at their ends. These mats provide added internal shear resistance beyond that of simple gravity wall structures. Other options include steel straps, also layered. This type of soil strengthening usually needs outer facing walls to affix the layers to and vice versa.The wall face is often of precast concrete units[2] that can tolerate some differential movement. The reinforced soil’s mass, along with the facing, then acts as an improved gravity wall. The reinforced mass must be built large enough to retain the pressures from the soil behind it. Gravity walls usually must be a minimum of 50 to 60 percent as deep or thick as the height of the wall, and may have to be larger if there is a slope or surcharge on the wall.

1. Retaining Wall:

A retaining wall is generally defined as a vertical wall that holds back earth. However a retaining wall has many uses such as:

  • A retaining wall for roadside embankments

  • A retaining wall can separate older roads from highways

  • A house retaining wall for the garage

  • A retaining wall helps keep river banks from eroding

A retaining wall to keep earth from stairwells and driveways

How to build a retaining wall depends on the type of retaining wall system you choose. During home retaining wall construction, you must choice between the different types of retaining wall construction methods. The most popular choice for retaining wall construction is concrete. Some retaining wall construction types are:

  • A concrete retaining wall

  • An interlocking block retaining wall

  • A Wood retaining wall

  • An Insulated Concrete Form retaining wall or ICF retaining wall

After the retaining wall construction is complete, the retaining wall is then backfilled on one side only. Backfilling on one side of the retaining wall creates an extreme amount of pressure. This pressure comes from the weight of the earth and the moisture in the soil. This pressure can result in cracks and water seepage in the retaining wall. During retaining wall construction you should always remember a proper drainage system. Installing a SUPERSEAL drainage membrane during retaining wall construction will help prevent the effects of water seepage. Some of those effects are:

  • Green slime

  • Efflorescence

  • Mineral deposits

  • Rust from wall tie

Freeze and thaw cycles also creates extra stress on a retaining wall. Expansive and soft soils can also account for some retaining wall problems. Installing a SUPERSEAL drainage membrane with drain tile on the backfilled side during retaining wall construction or during a repair of a retaining wall will help reduce or eliminate most of problems associated with a retaining wall.

2. Installation Tips:

The National Concrete Masonry Association offers installation guidelines in the Segmental Retaining Wall Installation Guide. However, Anchor Wall Systems provides a brief overview of the recommended installation for Anchor products:

2.1 Step One:
Using a shovel or a skid loader, dig a trench about 24 inches wide and deep enough to fit the required amount of buried block and compacted base. For walls four feet high and shorter, bury one course of units. Total wall height includes the height of any buried courses.

2.2 Step Two:
Firmly compact the soil in the bottom of the trench. Lay six inches of compactable base (e.g., sand and gravel) in the bottom of the trench and compact.

2.3 Step Three:
Place the first layer of Anchor units without lips on the prepared base (lips must be manually knocked off units before placement). Position the units side-by-side, in full contact with the base, and level in both directions using your carpenter’s level. Backfill with free-draining aggregate.

2.4 Step Four:
Anchor recommends using a filter fabric, which should be placed directly behind the wall extending from the bottom of the base course to the middle of the top course.

2.5 Step Five:
Continue assembling additional courses in a running bond pattern, pulling each unit forward until secure. Use free-draining aggregate to backfill each additional course as it is installed.

2.6 Step Six:
Place drain tile behind the wall at grade to allow water to drain from the backfill (organic or clay-type soils are not recommended). Outlet the drain tile through the wall at every low point, or every 75 feet of wall length and around the ends of the wall. Backfill with free-draining gravel 12 inches behind the wall, in six-inch layers.

2.7 Step Seven:
Fill any remaining areas behind the wall with soil. Compact every 12 inches. Repeat steps five through seven until the wall reaches the desired height.

2.8 Step Eight:
Firmly compact native soil every 12 inches behind the wall. Do not compact directly on top of the units.

3. Masonry Retaining Wall:

Today’s homeowners are always looking for ways to increase the value of their property. One of the first things people do to increase value is to improve the overall appearance of the home by enhancing its curb appeal with landscaping. The popularity of adding a retaining wall has increased significantly because of the flexibility of design, practical uses and aesthetic options such as shape and color of the blocks.

There are two types of retaining walls: gravity walls and reinforced walls. A gravity wall, or non-reinforced wall, relies on the weight and batter of the retaining wall to resist the loads imposed on the structure by the retaining soil and is usually less than four feet in height. A reinforced wall is designed by a qualified engineer using geosynthetic reinforcement. Reinforced walls are usually greater than four feet tall and have special loading conditions present like slopes or surcharges.

While adding to the look of a landscape, a segmental retaining wall (SRW) can also serve a practical purpose. One of the major uses for SRWs is to help control erosion. For example, steep hills can lead to mudslides, improper drainage and general unsavory appearance of the property. Such was the issue facing upscale homeowners in Deephaven, Minn., who needed to replace a boulder-laden, steep hillside. They wanted a practical wall that was aesthetically pleasing while allowing for decorative options. For a solution, they turned to a local contractor and Anchor Wall Systems.

A curvaceous, tiered retaining wall was suggested to best spruce up the yard. Overall, the entire wall would stand 11 feet tall. The design of the wall would encompass four interconnected levels, each terrace measuring 3.5 feet tall.

With the design and layout of the wall finalized, the homeowners elected to use Anchor Highland Stone¨ and new jumper accessory unit. Highland Stone is a three-piece concrete retaining wall system featuring a face texture that replicates natural stone. The jumper unit is an accessory that has the same color and texture of the other blocks, but it stands vertical in the wall. This breaks the pattern of all horizontal blocks across a typical retaining wall providing the freedom to experiment with different pre-arranged patterns in a wall, or choose random placement for a more customized look.

The project began with major excavation — the landscapers took out 75 to 80 yards of soil and two to three large trees. Once a base had been established, the set-back of the block caused the radius of each course to gradually increase (inside curve)/decrease (outside curve) and eventually affected the running bond of the wall. To maintain proper running bond, partial units were inserted as needed.

The result was a whole new look for the property: a retaining wall, curved with a natural stone look, terraces for plants and flowers, and vertical blocks to vary the look, all while effectively channeling the water run-off from the steep hillside.

Before building your retaining wall project, Anchor Wall recommends key steps to take into consideration in planning, on-site evaluation and installation.

4. Planning:
The first step in building a retaining wall is thorough planning. A site plan, design soils information and a wall construction plan are essential before getting started on a retaining wall project.

4.1 Site Plan:
The site plan is a detailed drawing of the site including wall location, length, elevations, information on grading, underground utilities, erosion control and storm water management.

4.2 Design Soils Information:
The design soils information identifies the kinds of soils on your construction specifications.

4.3 Wall Construction Plan:
The wall construction plan is a blueprint of the wall you’re going to build, and has five requirements: wall, toe and crest elevations; reinforcement location and length; soil conditions and parameters; drainage and other wall details; and wall construction specifications.

When creating a wall construction plan, it is important to consult with an engineer, as it is their job to determine the length and the number of geosynthetic reinforcement material that is required to stabilize a site-specific segmental retaining wall system, as well as provide drawings that show how a wall should be constructed. Geosynthetic reinforcement is a sheet material made from high-tensile strength polypropylene, polyethylene or polyester that, when used properly, helps to support the retaining wall system.

The need for geosynthetic reinforcement depends upon many factors, including wall height, soil conditions, expected loads and earth movement. To determine whether geosynthetic reinforcement is warranted, an engineer should evaluate every retaining wall project, even those lower than four feet. When geosynthetic reinforcement is required, an engineer can specify the appropriate materials, number of layers and correct placement of geosynthetic reinforcement based on the particular site conditions and your project design.

5. On-site Evaluation:

When all plans for the project are in place, the next step is to conduct an on-site evaluation both for materials and for safety.

5.1 Building Materials:
To protect materials from surrounding equipment and construction, lay out a storage area for the block, reinforcement, drainage and base materials. Check the delivered materials carefully. Elevate the blocks on wooden pallets, and keep the reinforcement dry, covered and clean.

5.2 Safety:
Follow the guidelines for worker and job site safety established by your state’s Department of Labor. And take special precautions for OSHA requirements, which include maintaining safe slopes. Coordinate with the foreman to make sure you know the location of underground utilities.

Technology and innovation will undoubtedly continue to fuel and expand the SRW construction market. For example, there is now a special process called global stability analysis that can analyze the projected stability of a wall before it is built by determining how the wall will react to earth pressures. In the meantime, Anchor Wall Systems has professional engineers on staff to answer your questions with preliminary designs using Anchor’s comprehensive software program, Anchor Wall Design

6. Retaining Wall Construction and Maintenance Recommendations:

The following recommendations are based on analysis of recent failures. Issues bearing on the design, construction, and maintenance of retaining walls, with particular emphasis on proprietary Mechanically Stabilized Earth (MSE) walls, include selection of the proper system for a given location, proper construction practices, and proper maintenance and design recommendations, which are important for long-term wall performance.The project engineer must ensure that the retaining wall system selected for a given location is appropriate. MSE wall suppliers are only responsible for the internal stability of their walls. The overall (global) stability of an MSE wall system is the responsibility of the engineer who selects this type of wall for inclusion into the plans.

6.1 Geometry:

Location geometry most often dictates the selection of a retaining wall system. The Geotechnical Manual offers information regarding evaluation of geometry and selection of various wall types. MSE walls are commonly used on TX DOT projects; however, in many situations–especially cuts–MSE may not be the most appropriate wall type. Often the additional excavation and shoring required for installation of MSE walls in cut situations make them uneconomical and difficult to construct. Sometimes MSE walls are selected because only a geometric layout and a standard sheet are required in the plans (the final detailed drawings are produced as shop drawings). This minimal design effort up front makes MSE walls a popular choice among engineers with limited time and resources. Although tied-back, soil nailed, drilled shaft and spread footing walls all require considerably more design effort and time, they are preferable in some cut situations.

The stability of each proposed retaining wall installation must be evaluated. Usually this involves a simple review of the wall height, site geometry, and soil borings. Walls with heights of 20 feet or less, situated on level ground, with soils borings indicating Texas Cone Penetrometer (TCP) blow counts in excess of 20 blows per foot should not require a detailed analysis. Walls taller than 20 feet, situated on slopes, or on soils weaker than 20 blows per foot should be looked at more closely. In general, place walls on any slope steeper than 4:1 only with a careful review of both short and long-term stability. Of particular concern are walls placed on freshly cut slopes, where the soil data may indicate high strengths at the excavation level. Freshly exposed material will soften with time, and an assessment of long-term strengths must be made when analyzing walls in this situation. Local districts may want to modify these guidelines based on their experience with specific projects and local conditions.

6.2 Soil Characteristics :

The Texas Cone Penetrometer is poorly correlated for very low soil strengths and may yield overly conservative results. When evaluating stability of walls on soils weaker than 20 blows per foot, it may be appropriate to conduct laboratory or in-situ testing in addition to the TCP. Triaxial or direct shear laboratory tests will generally yield more accurate soil strengths for this type of analysis.

Engineers in the Geotechnical Branch of the Bridge Division are available to assist with the determination of testing for specific situations and with the slope stability analysis.

6.3 Construction Practices Actual Soil Conditions :

Because soil borings are taken at discrete locations, it is difficult to determine what soils conditions will be experienced over a wider area. During construction of retaining walls, evaluate the proposed retaining wall location and notify the project designers of potential problems. Of concern are soils that are soft or wet, areas that are producing groundwater, and areas that exhibit slope failures during excavation. Each of these indicates potential stability problems and should be brought to the attention of the wall designer. It may be necessary to remove and replace poor soils, install drains, or modify the wall to address such field conditions.

6.4 Base Backfill :

Backfill the excavated area in the base of retaining walls as quickly as possible. Accumulation of groundwater or surface water in this area will soften the soils and reduce the stability of the walls. Excavation at the base of an existing wall for installation of storm sewer, roadway, of other structure should not proceed without a determination of wall stability in the excavated condition.

6.5 Filter Fabric :

Cohesionless select fill is subject to erosion and piping if subjected to large quantities of water flowing into the wall. Filter fabric is required at each panel joint and is designed to retain wall backfill while allowing the water to pass. Gaps or voids in the filter fabric allow fill to escape from behind the wall.

6.6 Sealing :

Sealing of coping joints prevents excessive quantities of water from entering the top of the wall. The current RW(TRF) standard sheet requires all coping joints be sealed. This item of work should be required in the field and monitored for compliance.

6.7 Maintenance:
Periodically inspect walls for evidence of backfill loss, loss of joint seals, or movement. Reseal joints, particularly those that may allow surface water to enter the wall backfill. If evidence of backfill loss is observed, backfill the effected area with select fill if the area is accessible, or use flowable fill if access is restricted. Water infiltration into voids in walls can cause excessive pressures within the wall and result in displaced panels and wall failures. Treat voided areas when they are small and manageable, as they will always increase in size with time.

6.8 Avoid the use of cement-stabilized backfill :

Although cement-stabilized backfill is an option allowed in our standard specifications and is an easy short-term solution, it compromises the long-term performance of the wall because it reduces the wall’s flexibility and it does not allow drainage through the wall. On projects where settlement is anticipated due to soft soil, a general note should be added to the plans eliminating cement-stabilized backfill as an option.

Retaining walls serve well, but there are some key points for successful wall performance: the correct system must be chosen for each location, and proper construction practices must be employed. Also, as described above, there are a number of design and maintenance issues that are equally important.

7. Stability Problems:

A retaining wall is a structure that holds back soil or rock from a building, structure or area. Retaining walls prevent downslope movement or erosion and provide support for vertical or near-vertical grade changes. Cofferdams and bulkheads, structures that hold back water, are sometimes also considered retaining walls. Retaining walls are generally made of masonry, stone, brick, concrete, vinyl, steel or timber. Once popular as an inexpensive retaining material, railroad ties have fallen out of favor due to environmental concerns. Retaining walls are often used as a barrier on a beach that stops the earth behind the sand eroding and collapsing.

Segmental retaining walls have gained favor over poured-in-place concrete walls or treated-timber walls. They are more economical, easier to install and more environmentally sound.

The most important consideration in proper design and installation of retaining walls is that the retained material is attempting to move forward and downslope due to gravity. This creates a lateral earth pressure behind the wall which depends on the angle of internal friction (phi) and the cohesive strength (c) of the retained material, as well as the direction and magnitude of movement the retaining structure undergoes. Lateral earth pressures are typically smallest at the top of the wall and increase toward the bottom. Earth pressures will push the wall forward or overturn it if not properly addressed. Also, any groundwater behind the wall that is not dissipated by a drainage system causes an additional horizontal hydrostatic pressure on the wall.

8. History:

The line of the Great Western Highway in this area does not appear to have altered much since the 1860s. The subdivision that adjoined the area of the highway where the retaining wall is situated was that of the Marmion Estate, which commenced in 1897. A 1907 plan shows the Bathurst Road in this area and noted the presence of old fence stumps along the edge of the roadway. In the nineteenth century the edge of the main road was usually defined by split timber post and railing fencing. The noting of the remains of the old fence but absence of any mention of the retaining wall suggests that it had not yet been constructed. Stylistically the wall appears to date from the early twentieth century, probably the 1920s. The construction of the wall, which supports the road shoulder/embankment above, suggests that it relates to the raising of the level of the road formation, probably by filling, in order to provide a level grade on this section. This type of work is most likely to have been required for early motor vehicles. The wall was probably built by the Main Roads Board between 1925 and 1930 (Lavelle, 2000).

9. Historical Significance

The retaining wall represents the expansion of the NSW road network and the updating of an earlier link in that network. It represents improvements in the local area of Leura by providing the means to accommodate early motor vehicles along a transport route that was durable and reliable in all weather conditions. The wall has been assessed as fulfilling this criterion on a local level

View of masonry retaining wall looking east from adjacent footpath

10. Failures in Retaining Walls:

10.1 Reasons:

Too much pressure for size and type of wall. What’s it made of and how much is it trying to hold back

Failure retaining wall collapse