An analysis of secondary toppling rock failures—the stress redistribution method

Summary Following the terminology of Goodman & Bray (1976), several examples of secondary toppling failures are presented. Six possible failure mechanisms are considered; bearing capacity failure or differential settlement due to weathering and creep with associated stress redistribution are concluded to be the most likely failure mechanisms; however, the former is not supported by field evidence. The differential settlement mechanism involves stress relaxation in the basal softer rocks (claystones) whereby the overburden load is redistributed to the fresher materials, thus reducing the amount of differential settlement likely to occur. The lateral constraints provided by horizontal stresses may temporarily inhibit this mechanism.