FENCE or RETAINING WALL APPLICATION Residential Commercial Date: _____ RETAINING WALLS: Walls that are over 4 feet (1219 mm) in height measured from the bottom of the footing to the top of the wall or supporting a surcharge. Fill materials behind retaining walls shall be fully drained of water and other fluids by means of sub-drain, weep holes and/or other approved method at least equivalent to the attached detail. the backfill is horizontal. Retaining Wall. 1. The free draining gravel backfill has a soil unit weight, g , of 21.2 kN/m 3 (135 lb/ft 3 ), and an angle of internal friction, f , of 36 degrees. 3. Expected value: can be 0. geotechnical design of flexible cantilevered or anchored retaining walls to be constructed on New York State Department of Transportation projects. Design of retaining walls on boundary for surcharge load A wall that requires reinforcement such as Geogrid automatically requires a 2nd system called the heel drain. Different types of retaining walls are used to retain soil in different places. 2 | P a g e Retaining Wall – A Retaining Wall is a wall designed to resist lateral earth and/or fluid pressures, including any surcharge, in accordance with accepted engineering practice. As soil loads increase with wall height (or surcharge), the depth of the soil reinforcement is lengthened and additional layers of reinforcement are added, safely securing the soil zone. load on heel is due to the weight of heel + fill + surcharge as the wall … The following design example is provided with the permission of the Reinforced Earth Company. Semi-Gravity retaining wall (reduce the dimensions of the gravity retaining wall by using some reinforcement). Design of retaining walls as presented in this Bulletin are in accordance with Sections 1610.1 and timber. CONTACT OUR OFFICE IF YOU HAVE ANY QUESTIONS. Example #1: Using the Rankine analysis, determine the individual lateral earth pressures, and resultant lateral earth pressure on a 2.1 m (7 ft) rigid concrete retaining wall. Mechanical properties and engineering significance of these components are discussed below. The walls are used in a variety of applications se including right-of-way restrictions, protection of existing structures that must remain in place, Surcharge should be calculated using: ω = 1.2 G + 0.4 Q for the gravity case Retaining walls must be designed to resist the lateral pressures due to the retained soil. The other tricky issue is when the surcharge is actually placed and how compacted is the soil or was at some point. The left portion contains all of the input data (and in some cases intermediate calculated values). Types of earth pressure: Active earth pressure or earth pressure (Pa) and Passive earth pressure (P p). Safe bearing capacity of soil is 200 kN/m2. Retaining wall guardrail requirements: this article describes the requirement for guard railings along the top of many retaining walls. As you can see in the table we use our 600mm Vitablock for smaller walls. Surcharge pressure. for example; basement wall is restrained to move due to slab of the basement and the lateral earth force in this case can be termed as" P o ". Gravity retaining wall (depends on its weight for resisting lateral earth force because it have a large weigh) 2. Great geotech type problem for the PE exam!! It could be a form of line load or uniformly distributed load. 1.0DC+1.0EV+1.0EH+1.0EQE. (5) Uniform surcharge pressure = (0.333 × 10) = 3.333 kN/m 2. Alternative design procedures justified in a geotechnical report may also be approved. • Vertical surcharge loads on walls; • Seismic lateral earth pressure on retaining walls; and, • Acceptable engineering criteria for retaining wall design. Retaining Wall to Support a Cut. Project Name: Example Report Design by: LAA Job #: 9876 D a e 10/21/2013 Codes used: 2010 & 2013 CBC, 2009 & 2012 IBC, ACI 318-08 & 318-11, ACI 530-11 S o i lS r u c u r e c o m SoilStructure Retaining Wall v2.0 1 Surcharge G.S. Design Parameters: Soil Bearing Capacity, q all : 100 kPa; Coefficient of Soil Friction, ф: 30° Where a retaining wall is constructed in close proximity to a building or structure, the distance from the base of the building to the wall (retained area side of the wall) shall be equal to or less than the height of the retaining wall (measured from the base of the foundation). The Guidelines for Retaining Walls 4'-0' in Exposed Height or Less is designed to assist in building structurally sound retaining walls, as long as the contents outlined are followed. The main purpose of retaining wall construction is to retain soil; that is why soil lateral earth ... 2. Cantilever or Restrained Retaining Wall Calculations O r g a n iz a io n F.E.C. The wall will be built adjacent to the roadway shoulder where traffic is 2 ft. from the barrier face. Worked examples presented at the Workshop “Eurocode 7: Geotechnical Design” Dublin, 13-14 June, 2013 Support to the implementation, harmonization and further development of the Eurocodes Among the switchbacks climbing the mountain road is a beautiful example of a Civilian Conservation Corp retaining wall built in the twenties. Any wall that sustains significant lateral soil pressure is a retaining wall. This Surcharge location is 0 feet from shoring/retaining wall Height of retaining wall/shoring is 10 feet Traffic Surcharge 𝑞=𝛾 𝑃×𝐻𝑒𝑞 = 30 pcf (Given in this example) x 3. construction of a retaining wall does not require a building consent when it is less than 1. This design example focuses on the analysis and design of a tapered cantilever retaining wall including a comparison with model results retaining wall, allowing architects to increase wall height, back slope (the slope above the top of the wall), or surcharge. Three main types of retaining walls: 1. This drain captures water further away from the wall, and lowers the surcharge on the wall. Building Codes and Retaining Walls 5. Forces on Retaining Walls 6. CE 537, Spring 2011 Retaining Wall Design Example 6 / 8 2.80 5.0 allowablebearingcapacity, OK (1 )(11.75 ) 6 1 29.9 (1 )(11.75 ) 17.69 2 ksf ksf ft ft k ft ft k v 7. Wall situation: Case 3: Retaining wall downslope and supporting dwelling foundations Surcharge: The surcharge from the dwelling was assumed to be 5 kN/m 2 averaged across the active soil wedge for the gravity case and 4 kN/m 2 for the earthquake case. Typical calculations are shown, including the determination of allowable reinforcement tension for galvanized steel reinforcing strips. The wall has been modelled per metre run on Staad, and plate mat foundation was utilised with coefficient of subgrade modulus of 100000 kN/m 2 /m. Usually this information is given in the governing code. =1.5) Do not consider the passive resistance of the fill in front of the wall… Cantilever retaining walls can be precast in a factory or formed on site and considered economical up to about 25 ft in height. surcharge on retaining walls. For example, a retaining wall less than 3.5-ft in exposed height will typically have at least 6 inches (in) of embedment (buried wall) for a total wall height of 4-ft. A building permit is typically required if the total height of the wall (exposed and buried) exceeds 4-ft for cantilever or segmental gravity (block) retaining walls. surcharge loads acting on retaining wall surcharge loads acting on retaining walls are additional vertical loads that used to the backfill soil above the top of the wall. thick P W la M active + water pressure 83.6 103.5 surcharge pressure 0.23x10x4 9.2 2.0 18.4 self weight 4.0x3.3x23 303.6 - 0.0 Stability Checks for Retaining Walls. Example Statement: The retaining wall supports 15'-0" of level roadway embankment measured from top of wall to top of footing. This Island Block & Paving Retaining Wall Software Q11050501-1 5/5/11 Page 3 PART 1 User Manual - Design Check to AS 4678 of: Segmental Concrete Reinforced Soils Segmental Concrete Gravity Retaining Walls Reinforced Concrete Masonry Cantilever Retaining Walls Scope This manual applies to the use of the Microsoft Excel spreadsheet to analyse and check the 1: Soil Pressure on the back of wall (No surcharge) Worked Example: Figure A.1-Retaining Wall Cross Section. 5, 6). A retaining wall is provided when there is a need to support an excavated area or a lower area of at least 1 or 1.2 meters or more from an elevated part of the soil. The factor you refer to is the active or at-rest earth pressure coefficient. A n beal earth retaining structures worked examples 6 surcharge consider with 10knm2 surcharge behind wall cp2 cp2 design table 3 buoyant density of soil 11knm2. A slurry wall excavation example will be analyzed with DeepEX. Gravity loads acting on backfill due to the construction of buildings or the movement of vehicles near the top of the retaining wall; These loads are considered as uniformly distributed loads, and are mostly present on a level backfill. In this example, the structural design of the ... surcharge = q s = 400 psf . Retaining wall Design Design example-1 Design a cantilever retaining wall (T type) to retain earth for a height of 4m. ... For most walls, only two or three changes in stem sections are used. Helpful retaining wall problem with a surcharge load. CE 537, Spring 2011 Retaining Wall Design Example 6 / 8 2.80 5.0 allowablebearingcapacity, OK (1 )(11.75 ) 6 1 29.9 (1 )(11.75 ) 17.69 2 ksf ksf ft ft k ft ft k v 7. The density of soil is 18kN/m3. See Figure 3. Heel Design. Each of these walls must be designed to resist the external forces applied to the wall from earth pressure, surcharge load, water, earthquake etc. There are a lot of variables when designing and building a concrete retaining wall. • Vertical surcharge loads on walls; • Seismic lateral earth pressure on retaining walls; and, • Acceptable engineering criteria for retaining wall design. 🕑 Reading time: 1 minuteThere various parts of a retaining wall and design principles of these retaining wall components based on different factors and material and methods of construction are discussed. Steps to adopt (1) Model the retaining wall utilising plate element meshing, assign thickness of 0.4m to the base, and 0.3m to the wall. Surcharge examples would be a road, parking lot or structure. Retaining wall design_example. This soil may be removed KP 2 Hp 2 1 PP = γ Ka H2 2 1 A N Beal EARTH RETAINING STRUCTURES - worked examples 6 Surcharge Consider with 10kN/m2 surcharge behind wall CP2 CP2 Design Table 3 Buoyant density of soil = 11kN/m² 3300mm Try 3300mm thick wall. Lateral pressures caused by surcharge loading may be calculated depending on the type of surcharge and the nature of load distribution. Worked example to accompany MBIE Guidance on the seismic design of retaining structures for residential sites in Greater Christchurch (Version 2) November 2014 . Heel Design. However, the term is usually used with reference to a cantilever retaining […] The examples provided Online and in do-it- ... retaining wall constructed at the base of a creeping slope in Richmond, California, along a state route. Retaining wall design and its types used on construction. These are often found in the basement part of a building structure. In this example the wall has a full height backfill and a uniform surcharge on top. RETAINING WALL PROBLEMS P1. The following design example is provided with the permission of the Reinforced Earth Company. We cite model building codes, individual U.S. state building codes, and we give photo examples of good, bad, and ugly or downright dangerous guard railings, or walls that should have had a guard railing. The County of Lake adopts, by reference, the 2016 California Residential Code Section 105.2 Item 3 which states:“Retaining walls that are Soil Mechanics Simplified 4. Earthquake (Seismic) Design 7. These components are illustrated in Figure 1. the soil pushes the I don't think you can apply those bulb charts when a retaining wall … surcharge loads acting on retaining wall. Max. The safety factor against sliding (minimum required F.S. The active earth pressure coefficients for various values of ϕ’, α, and with ′=1 2 WALLS • Cantilever theory was introduced by Galileo in the 16th Century, then advanced by Sir John Fowler and Sir Benjamin Baker in the 19th Century • Reinforced concrete retaining walls were introduced by the Chicago, Burlington and Quincy Railroad in the 1880s • The safety factor against sliding (minimum required F.S. General Requirements and Materials . Eurocode Retaining Wall Stem Design Example Structural Design Eurocode. About Retaining Walls; Terminology 2. CE 437/537, Spring 2011 Retaining Wall Design Example 6 / 8 2.80 5.0 allowable bearing capacity, OK (1 )(11.75 ) 6 1 29.9 (1 )(11.75 ) 17.69 2 = + = < = − ksf ksf ft ft k ft ft k σ v 7. In this calculation, we are concentrating on the two stability checks of … Three main types of retaining walls: 1. load on heel is due to the weight of heel + fill + surcharge as the wall tries to tip over. • Surcharges on either side of the wall. The surcharge is a pressure load applied to the soil retained by the wall. Gravity retaining wall (depends on its weight for resisting lateral earth force because it have a large weigh) 2. load on heel is due to the weight of heel + fill + surcharge as the wall tries to tip over. CE 437/537, Spring 2011 Retaining Wall Design Example 1 / 8 Design a reinforced concrete retaining wall for the following conditions. The retaining wall module divides the screen into a left and right portion. 2. Surcharge: The vertical load imposed on retained soil that may impose a lateral force in addition to lateral earth pressure of retained soil. Retaining wall & privacy wall definitions: this article defines retaining wall, barrier or privacy wall, and key retaining wall terms such as wall surcharge and types of retaining wall construction. The wall stem is 1'-6" wide to accommodate mounting a Type 7 Bridge Rail to the top of wall. This definition also applies to freestanding pool walls. for all ERS except crib walls. 3. Retaining Walls Page 10 Lateral Soil Pressure on Retaining Walls Typical Angle of Internal Friction for backfill soil Soil Type φ (Degree) Gravel and coarse sandy backfill soil 33-36 Medium to fine sandy backfill soil 29-32 Silty sand 27-30 P max = K a γ soil h h γ soil Backfill Fig. for crib walls (For Extreme Event Limit State I, live load surcharge is not considered) where: DC = the self weight of structural components. All engineered walls will include a full drainage system. Recommended stem designs for reinforced cantilever retaining walls with no surcharge are contained in Tables 1 and 2 for allowable stress design and strength design, respectively. Retaining wall & privacy wall definitions: this article defines retaining wall, barrier or privacy wall, and key retaining wall terms such as wall surcharge and types of retaining wall construction. SECTION 5 - RETAINING WALLS Part A . Design Procedure Overview 3. WALLS • Cantilever theory was introduced by Galileo in the 16th Century, then advanced by Sir John Fowler and Sir Benjamin Baker in the 19th Century • Reinforced concrete retaining walls were introduced by the Chicago, Burlington and Quincy Railroad in the 1880s • Reference Guide For Designing Retaining Walls Using Interlocking Concrete Blocks EPCL-2017-RWRG-01-P01 June 2017 4 The retained ground (or stored materials) and imposed surcharge loads exert pressures on the retained side of the Heel Design. For example: Sloping retained soil; structure footings supported Prior to completing any retaining wall design, it is first necessary to calculate the forces acting on the wall. Introduction . Lateral Earth Pressure Acting on Retaining Wall. This includes the soil type, surface water flows, the height of the wall, slopes both in front of and behind the wall, and any surcharges the wall may support. ENGINEERING DESIGN MANUAL StoneTerraTM MSE WALL SYSTEM 1st EDITION December 2010 2 StoneTerraTM MSE WALL COMPONENTS A StoneTerraTM MSE wall consists of many components. 22.67 0.261 7.60 20 0.36 These design methods are discussed in detail in Allowable Stress Design of Concrete Masonry, TEK 14-7A, and Strength Design of Concrete Masonry, TEK 14-4A (refs. Retaining Wall to Support a Fill. 5. 3. RE: surcharge loading on retaining wall. for all ERS except crib walls. (8.4): Forces acting on a retaining wall. =1.5) Do not consider the passive resistance of the fill in front of the wall… load on heel is due to the weight of heel + fill + surcharge as the wall tries to tip over. Chapter 14 – Retaining Walls July 2020 14-7 14.1 Introduction Retaining walls are used to provide lateral resistancefor a mass of earth or other material to accommodate a transportation facility. It is used to calculate the lateral pressure on a wall due to a vertical surcharge pressure. 1: Soil Pressure on the back of wall (No surcharge) use Figure 5-6, “Surcharge Approximation for Tiered Walls”.Question: Can I have a single wall that “splits” apart, with the bottom half curving away from the top half? When an engineer is contracted to design a retaining wall, they take all the site parameters into consideration. Typical calculations are shown, including the determination of allowable reinforcement tension for galvanized steel reinforcing strips. The following data is available: a) Soil properties: Sand, friction angle = 30 degrees, total unit weight 120 pcf, loading modulus of elasticity Eload= 300 … Retaining Wall to Support a Fill. A retaining wall engineer can design the Lower Wall for the surcharge load applied by the Upper Wall. The example problems in this manual are based on walls constructed with Allan Block Retaining Wall System’s AB Stones. Diaphragm (slurry) wall example with DeepEX. It is the type of structure use to resist the lateral pressure caused by the soil. 2. Retaining walls shall be designed to withstand lateral earth and water pressures, the effects of surcharge loads, the self-weight of the wall and in special cases, earth­ quake loads in accordance with the general principles specified in this section. A retaining wall is a structure designed and constructed to resist the lateral pressure of soil, when there is a desired change in ground elevation that exceeds the angle of repose of the soil. Retaining Walls Page 10 Lateral Soil Pressure on Retaining Walls Typical Angle of Internal Friction for backfill soil Soil Type φ (Degree) Gravel and coarse sandy backfill soil 33-36 Medium to fine sandy backfill soil 29-32 Silty sand 27-30 P max = K a γ soil h h γ soil Backfill Fig. EV = the self weight of the soil above the heel of a footing in a semi-gravity retaining wall or of the reinforced soil in a MSE. Fig. RETAINING WALLS 8.1 INTRODUCTION Retaining walls are structures used to provide stability for earth or other materials at their natural slopes. Lateral earth pressures and the … construction of a retaining wall does not require a building consent when it is less than 1.5 m high and ‘does not support any surcharge or any load additional to the load of that ground (for example, the load of the vehicles on a road)’. Yes! Cantilever timber pole walls are probably the most commonly used form of retaining wall for residential purposes. Max. Surcharge Loads. Greco (1999, 2003, 2005 and 2006) applied Coulomb’s theory to investigate the effect of strip surcharges on active earth pressure in retaining walls and proposed an Design of retaining walls as presented in this Bulletin are in accordance with Sections 1610.1 and This pressure tends to deflect the wall outward. The following text provides a general discussion and design guidelines for these flexible wall Heel Design. 11.11.1 T-shaped gravity wall retaining dry fill (undrained analysis) Example 11.1 considers the design of a T-shaped gravity wall retaining dry fill, as shown in Figure 11.10. H/3 above the base of the wall and will be inclined at an angle ′ to the normal drawn to the back of the wall. Reinforced Block Retaining Walls The block in the example in figure 3 is our Stackablock as shown here in figure 4. it can be either dead loads, for example, sloping backfill above the wall height or live load, which could result from the highway or parking lot, paving, or adjacent footing. This application determines required footing width, footing thickness, wall thickness and reinforcement areas for retaining walls with sloping backfill. Retaining Wall: A wall designed to resist earth and/or fluid pressure, including any surcharge in accordance with acceptable engineering practices. Retaining Wall Design 10 Editionth A Design Guide for Earth Retaining Structures Contents at a glance: 1. Overturning and sliding checks are done to make sure the stability of retaining walls. Basically, beyond the failure plane of say 50 degrees you still get a decent surcharge on the wall. Figure 8.40 shows a cut­away view of a typical Reinforced Earth retaining wall. In the NCMA* Design Manual (2010, Third Ed.) Assuming that the allowable bearing pressure of the soil is 120 kNm 2, the Max. See CIRIA 580 and Euro code 7 for detailed advice. it can be either dead loads for example sloping backfill above the wall height or live load which could result from highway or parking lot paving or adjacent footing. 5.1 GENERAL . Patios, swimming pools and driveways are common residential surcharges. Using the equivalent bending moment technique, they proposed an analytical approach to calculate the active horizontal pressure on retaining walls. The Euro code 7 approach differs from the gross pressure (CP2) and net total pressure methods (Burland & Potts) which apply a FOS to the respective gross and net resisting's moment against overturning moments in applying CE 437/537, Spring 2011 Retaining Wall Design Example 1/8Design a reinforced concrete retaining wall for the psffollowing conditions. However elastic methods will yield a horizontal force for any surcharge applied at any distance behind the retaining wall. We believe that a twelve degree setback maximizes the leverage achieved by a battered wall, while providing a finished retaining The weight of a building or another retaining wall (above and set back from the top of the wall) are examples of dead load surcharges. than monolithic gravity walls, but require more design and careful construction. The retaining wall is vertical with horizontal backfill, that is, the cross-anisotropic planes are parallel to the boundary plane. f'c = 3000 psi fy = 60 ksi Natural Soil Development of Structural Design Equations. ENGINEERING DESIGN MANUAL StoneTerraTM MSE WALL SYSTEM 1st EDITION December 2010 2 StoneTerraTM MSE WALL COMPONENTS A StoneTerraTM MSE wall consists of many components. Surcharge loads Acting on Retaining Wall. In the actual design of retaining walls, the value of the wall friction angle ′ is assumed to be between ϕ’/2 and 2/3ϕ’. Max. Earth Pressure (P) 8 Earth pressure is the pressure exerted by the retaining material on the retaining wall. surcharge loads. Mechanical properties and engineering significance of these components are discussed below. The following text provides a general discussion and design guidelines for these flexible wall Loads and Forces Acting on Retaining Wall and Their Calculations [PDF] 1. We include definitions of important retaining wall terms such as wall surcharge, and we provide diagnostic descriptions & photographs of types of damage to retaining walls & privacy walls. Cut Fill Retaining walls designed using code tabulated values shall meet the conditions cited below: 1. EV = the self weight of the soil above the heel of a footing in a semi-gravity retaining wall or of the reinforced soil in a MSE. Different types of retaining walls are used to retain soil in different places. Take the co-efficient of friction between concrete and soil … Retaining wall shall be designed to withstand lateral earth and water pressures, including any live and dead load surcharge, the self weight of the wall, temperature and shrinkage effect, live load and collision forces, and earthquake loads in accordance with the general principles of AASHTO Section 5 and the general principles specified in this article. Surcharge pressure on earth retaining walls can arise from different sources such as loads from adjacent buildings, fills, roadways and traffic actions, construction activities, and undulating/uneven ground surfaces, etc. Your wall may need additional support if a … RETAINING WALL - SLOPING BACKFILL Construction of retaining walls, except those less than three feet high, measured from the top of the footing to the top of the wall and not supporting surcharge, requires a permit and is regulated by City Municipal Code. Setback Any added weight above a retaining wall is called a surcharge. Heel Design. Consider the cantilever retaining wall with the cross-section shown in the above Figure A.1, which retains a 2m depth of soil having the groundwater table at -1.0m level. Active earth pressure tends to deflect the wall … Figure 8.40 shows a cut­away view of a typical Reinforced Earth retaining wall. use Figure 5-6, “Surcharge Approximation for Tiered Walls”.Question: Can I have a single wall that “splits” apart, with the bottom half curving away from the top half? Example: Given: Active equivalent fluid pressure 𝛾 𝑃 is 30 pcf Surcharge location is 0 feet from shoring/retaining wall Height of retaining wall/shoring is 10 feet Traffic Surcharge 𝑞=𝛾 𝑃×𝐻𝑒𝑞 = 30 pcf (Given in this example) x 3.5 ft (From Table 1) = 105 psf. In addition to this, base bearing pressure is also checked to confirm whether it is within the limit. In deriving the proposed solutions, the backfill material is assumed to be a homogeneous, linearly elastic and cross-anisotropic continuum. surcharge loads acting on retaining wall are additional vertical loads that used to the backfill soil above the top of the wall. Alternative design procedures justified in a geotechnical report may also be approved. These components are illustrated in Figure 1. CE 433, Fall 2006 Retaining Wall Design Example 6 / 8 7. Suggest Suitable Dimensions for the RC Retaining Wall Example 1: Cantilever RC Retaining Wall 10 kN/m2 m 500 mm h = 400 0.6h = 240 2h = 800 h = 400 B = 0.6H to 0.7H = 3200 H = 4900 2000 2.71 kN/m2 27.9 kN/m2 25.9 kN/m2 Active Soil Pressure, P The AB Stones provide a nominal setback of twelve degrees from vertical. 1.0DC+1.0EV+1.0EH+1.0EQE. Retaining walls that are over 1.5 m high and those supporting a surcharge require a building The general guideline below is specific to embedded retaining wall. Active Lateral Earth Pressure: In case of the wall is free from its upper edge (retaining wall), the wall may move away from the soil that is retained with distance "+ΔH" (i.e. Retaining walls Example 3.16 Design of a cantilever retaining wall (BS 8 110) The cantilever retaining wall shown below is backÞlled with granular material having a unit weight, , of 19 kNm 3 and an internal angle of friction, , of 30 . for crib walls (For Extreme Event Limit State I, live load surcharge is not considered) where: DC = the self weight of structural components. Yes! geotechnical design of flexible cantilevered or anchored retaining walls to be constructed on New York State Department of Transportation projects. Flexure: W =Wheel +Wfill +Wsur k ft klf ft All blocks come with a lifting bolt and a lifting clutch. Soil Bearing and Stability 8. Semi-Gravity retaining wall (reduce the dimensions of the gravity retaining wall by using some reinforcement). Symbol: w s. Unit: kN/m 2. The safety factor against overturning, b. CANTILEVER RETAINING WALL Ouestion For the retaining wall and the profile shown below, calculate: a. PEinc (Geotechnical) 26 May 15 23:28. We include definitions of important retaining wall terms such as wall surcharge, and we provide diagnostic descriptions & photographs of types of damage to retaining walls & privacy walls. In the NCMA* Design Manual (2010, Third Ed.) allows for higher surcharge loads to be resisted. Even though the wall is founded on clay, the backfill has been assumed to be granular (which would be typical for this type of wall). RETAINING WALL PROBLEMS P1. The safety factor against overturning, b. This may be overly conservative however it is up to the engineer to determine what distance beyond the wall that the surcharge would have no affect on the retaining wall.