calculation of factors of safety against overturning and sliding for a cantilever retaining wall with uniform surcharge loading. therefore, the coefficient of active earth pressure is equal to one minus the sine of the angle of internal friction divided by one plus the sine of the angle of internal friction.
there are various types of loads and forces acting on retaining wall, which are: lateral earth pressure. surcharge loads. axial loads. wind on projecting stem. impact forces. seismic earth pressure. seismic wall self-weight forces.
while designing an excavation retaining system with an adjacent building resting on strip footings, a common practice is to consider the building load as surcharge load i.e. having an earth
if you are trying to analize the stability of the wall then think of the surcharge as part of a slope stability analysis where the slip surface includes the surcharge. remember that earth pressure analysis on a retaining wall is simply a special case of slope stability.
discussion. you will note that the pressure increases significantly as the surcharge gets nearer the wall again fairly obviously ; which is why we need to account for surcharges within our 45 zone of influence; and the surcharge will have much less effect as m exceeds 1, when the surcharge lies outside the 45 zone of influence.
if a wall is constructed downward, from the top of the wall to the bottom, it is considered a topdown type of wall. this generally requires - the insertion of some type of wall support member below the existing ground, and then excavation in front of the wall to the bottom of the exposed face.
calculate the lateral earth force acting on a retaining wall using the rankine formula. design problem 3: check the sliding resistance for a retaining wall. design problem 4: check the resistance to sliding, the turnover stability, the bearing capacity and calculate the required areas of steel reinforcement for a proposed retaining wall.
surcharge pressure on retaining walls 8. if you are trying to analize the stability of the wall then think of the surcharge as part of a slope stability analysis where the slip surface includes the surcharge. remember that earth pressure analysis on a retaining wall is simply a special case of slope stability.
the earth pressure is acting. the wall could be a basement wall, retaining wall, earth support system such as sheet piling or soldier pile and lagging etc. the three categories are: at rest earth pressure active earth pressure passive earth pressure the at rest pressure develops when the wall experiences no lateral movement. this
the actual load imposed on a semi-vertical retaining wall is dependent on eight aspects of its construction: 1. the degree of saturation of the wall backfill in the zone of active or at-rest earth pressure. 2. the degree of relative compaction of the wall backfill within the active or at-rest envelopes.
surcharge on retaining walls: a retaining wall which retains earth level upto the top of the retaining wall is a wall without surcharge. if the earth on the earth retained side is not level or the earth carries loads, the earth is said to have surcharge. the pressure exerted by the earth on the retaining wall will be more in this case.
cantilevered retaining wall. calculation of a factored load eccentricity would give soil pressure diagrams that would not always represent the actual soil pressure distribution under the footing, and yield unreasonable results. factored lateral earth pressure, however, is always used for concrete stem design.
wall 4 high x 12 wide x 9 deep product to 2 feet in height or six blocks in height total. height or six blocks in height total. retaining wall is supporting a sloping backfill, any other surcharge or a solid fence. one another, are used in lieu of a single tall retaining wall.
a treat block of active soil as a surcharge of density of soil x f when f can vary as the height of the soil block increase away from the face of the wall, then add horizontal force at the top of wall equivalent to the active thrust of the soil block being modeled as a surcharge.
for the reinforced concrete cantilever retaining wall shown below, calculate the factor of safety against overturning and sliding given the following parameters: cohesionless soil, c = 0
figure 1. traditional method of estimating lateral pressure due to surcharge load. ies in which the magnitude and distribution of lateral pressures on a retaining wall caused by the application of a concentrated load on the surface of the backfill were meas ured.
any added weight above a retaining wall is called a surcharge. patios, swimming pools and driveways are common residential surcharges. your wall may need additional support if a surcharge is present. setback. the amount your wall leans into the hill is called setback. ab blocks come in approximate setbacks of 6 and 12 .
when the gabion retaining wall is subjected to a additional surcharges, from a driveway or other loads, the designer will most likely increase the thickness of the gabions, to handle the higher expected loads. most gabion retaining walls can be built on soils with a minimum bearing capacity of 100kpa.
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. design relationships table 1 summarizes the influence of increasing the wall batter, increasing the unit width, increasing the units in-place density, and using better quality backfill on the maximum constructible height of a gravity srw to satisfy sliding and overturning.
a retaining wall is a structure exposed to lateral pressures from the retained soil plus any other surcharges and external loads. all overall stability failure modes must be thoroughly checked, including the bearing capacity of the supporting soil.
in this post, i will go over the third example in our foundation design course covering retaining walls. the goal of this foundation design example is to calculate the factors of safety against overturning and sliding for a cantilever retaining wall with uniform surcharge loading.
figure 1 illustrates how this pressure is applied to a retaining wall, and is calculated as follows: h kq where: h = surcharge pressure on wall k = lateral earth pressure coefficient q = surcharge load. the total horizontal pressure acting on a retaining wall can be found by summing the soil pressure and surcharge pressure.
wall backface to vertical surcharge r = ft. live load surcharge height hsur = ft. aashto table -2 vehicle collision load tl-4 pct = kip aashto table a13.2-1 collision load distribution lt = ft. aashto table a13.2-1 top of wall to point of collision impact on rail hct = ft. 1. stability checks 1. eccentricity 2. sliding 3. bearing applied loads
in the retaining wall components stem, toe and heel . equation to calculate effective depth, d: three basic equations will be used to develop an equation for d.