For toppling MEd,dst

kNm kNm


AGEO,3 m




Design is unacceptable if degree of utilization is >


© The variable surcharge needs to be considered in different positions depending which situation is being considered. Where the variable surcharge could be regarded as favourable it should not be included in the vertical actions and thus a variable surcharge is normally considered across the whole of the wall width for bearing capacity and overall stability only.

© Simple Rankine earth pressure coefficients have been used, ignoring friction along the virtual plane.

© The formulae for bearing capacity and inclination factors are those given in Annex D to EN 1997-1. Note: shape and depth factors are not included as the footing is considered to be a strip and there is little depth of embedment. As discussed in Chapter 6, EN 1997-1 does not include depth factors.

© The degree of utilization in Design Approach 1 for the undrained case is 59% for Combination 2 (for both sliding and bearing)

® The results for Design Approaches 2 and 3 are presented in summary only. The full calculations are available from the book's website at

Design Approach 2 applies factors greater than 1.0 to actions and resistance. Bearing rather than sliding is critical in DA2 and the degree of utilization (65%) is higher than for DA1.

Design Approach 3 applies factors greater than 1.0 to structural actions (i.e. the self-weight of the concrete) and material properties. Bearing is critical and the degree of utilization (64%) is marginally lower than for DA2.

11.11.2 T-shaped gravity wall retaining dry fill (drained analysis)

Example 11.2 continues the design of the wall from Example 11.1 (as shown in Figure 11.10), but this time using a drained analysis to verify the wall's design under long-term conditions.

All dimensions are the same as in Example 11.1 and the drain is considered to be fully effective. However, for this example, effective stress parameters for the clay, which are appropriate for considering the long-term behaviour of the wall, have been considered.

Notes on Example 11.2

O Similar comments are applicable to aspects of the calculation to those given for the undrained case (see Example 11.1).

Example 11.2

T-shaped gravity wall retaining dry fill (drained analysis) Verification of drained strength (limit state GEO)

Design situation

Re-consider the T-shaped gravity wall from the previous worked example, but now under persistent conditions. The foundation clay's characteristic peak angle of shearing resistance is ^k fdn = 26°, its effective cohesion c'kfdn = 5kPa, and its constant volume angle of shearing resistance

9cv k fdn = 20°. All other parameters remain unchanged from before.

Groundwater has been taken as coincident with the base of the wall.®

Design Approach 1 Actions (from previous calculation)

Characteristic total self-weight of wall is Wgk = 152.6kN/m Characteristic surcharge is QQk = 22 kN/m

Characteristic stabilizing moment (about toe) M^k stb = 233.6 kNm/m

Vertical action (unfavourable) Vd = kN/m v181.2 j

Vertical action (favourable) V^ fav :

Material properties Partial factors from Sets fM1 ^

vM2 j

v1.25 j

Design shearing resistance of clay ^d fdn = tan Design effective cohesion of clay c'd fdn tan

UK NA to BS EN 1997-1 allows <pcvd to be selected directly. Here, take the

0 0

Post a comment