Peck apparent pressures examples

Peck lateral earth pressures example

Peck in 1969 proposed a set of apparent lateral earth pressure diagrams applicable for braced excavations. These diagrams were developed from measured strut loads on a series of excavations primarily in Chicago. The diagrams are supposed to represent only the soil component while the water pressure should be added separetely. Strut loads are calculated by summing the load on the tributary area of each strut. These diagrams should be used with care as they do not account for wall or soil stiffness or other construction staging procedures. Never the less, they can form a good starting point to frame and compare loads for a more advanced non-linear analysis.

With this in mind, we will construct a braced wall with Peck earth pressures.

a) Soil has a unit weight of 20kN/m3, effective friction angle 34 degrees, cohesion 0 kPa, loading modulus of elasticity E= 10000 kPa, and reloading modulus Eur= 30000 kPa.

b) The water table is at 4m depth.

c) The walls will be reinforced concrete soldier piles (berlin type wall) with 60cm diameter piles spaced at 2m apart.

d) A construction surcharge of 15 kPa should be applied from 1m behind the wall for a length of 10m.

e) The excavation is 9m deep, with two levels of bracing placed at 3m and 6m depth.

The purpose of this example is to determine the loads on the struts according to Peck. Thus, we will apply the tributary method within the DeepXcav software to calculate loads in pure agreement with the Peck approach.