The purpose of this study was to develop a convenient method for assessing the stability of tiedback structures using the simplified methods of slices. The Load Distribution Method was developed to transmit the load from a row of tiebacks to the potential failure surface for use with the simplified methods of slices. The load from a row of tiebacks is assumed to form a uniform line load that is distributed to the potential failure surface. This distribution is based on Flamant's distribution of stresses through a semi-infinite elastic medium. STABL5 and PCSTABL5 are limiting equilibrium slope stability programs that contain the Load Distribution Method routines. These programs may be used to analyse the stability of tiedback slopes for landslide stabilisation, as well as to determine the overall stability of tiedback walls. The programs consider multiple rows of tiebacks, multiple tiedback structures as well as tieback loads, inclination, and length. The method developed was found to give good results and is applicable to those problems in which the application of a semi-infinite elastic half space may be used to model the slope conditions, and which may be modelled using a two-dimensional analysis. This paper is a brief review of some of the previously available methods for analysing the overall stability of tiedback structures. In addition, a discussion of the capabilities of STABL5 and PCSTABL5 is presented, and the development of the Load Distribution Method is summarised. The assumptions used in the development of the Load Distribution Method are discussed, along with the implications and limitations of using Flamant's distribution. The effect of tieback load on the factor of safety is also presented, along with recommendations concerning factors of safety for overall stability of tiedback slopes and walls.
Abstract