TABLE OF CONTENTS In soil mechanics the two common limits occur due to:
shear failure of the soil, leading to excessive distortion of a structure or a disruption of highways and services;
excessive displacement of the soil, inducing unacceptably high stresses in a structure as a result of differential movement.
For retaining structures, failure is a performance problem, related to either strength or deformation. A retaining structure can fail to perform in a satisfactory way for a number of reasons, associated with the failure of the structure itself, failure of the soil or because of unacceptable deformation.
Some possible failure situations in retaining structures are shown in Figure 4.10. In general, the design of a retaining structure should considered the following points: moment equilibrium of the system (overturn), horizontal force equilibrium (sliding), vertical equilibrium (bearing capacity), overstress of any part of the structure (bending or shear), and the general stability of the soil around the structure (slope failure, overall stability, basal stability). The stability of the structure should be satisfactory both in short-term and in the long-term. Because many retaining structures are associated with decreased level of total stress, it is normal to carry out long-term analysis in terms of effective stresses and effective strength parameters. This will normally give the worst conditions (Clayton et al. 1993).
On the other hand, a retaining structure may perform unsatisfactorily because of the excessive displacement it undergoes. It is seldom possible...
