Reliability of strength of long fixed-head pile embedded in (p-y) soft clay subiected to cyclic loading

摘要

This paper deals with reliability of strength of fixed-head long pile embedded in (p-y) soft clay subjected to cyclic loading of quasi static type. The (p-y) soft clay model developed by Matlock (1970) is the one dimensional model with respect to space variable x. The pile-(p-y) soft clay system is subjected to lateral load of deterministic type that changes in a discrete fashion. The strength of the system investigated is defined by maximum bending moment M_(Lmax) localized at the pile's head. The physical properties of the pile- (p-y) soil system carry some uncertainties that are considered as random parameters. The uncertainties of physical properties are described by the coefficients of variations COV(...). The determination of second order probabilistic uncertainties of strength Var(M_(Lmax)) of the pile-soil system is conducted in the scope of First Order Second Moment (FOSM) method. The maximum resistance moment M_(Rmax) associated with the investigated system is also regarded as a random property. It is characterized by a lump value of COV(M_(Rmax)). The knowledge of M_(Lmax) and M_(Rmax) forms basis for formulation of state function g(M). The determination of variance Var(g(M)) with aid of Var(M_(Lmax)) and Var(M_(Rmax)) enables one to establish the reliability index β_M of strength of the system. Thus, combining information of β_M and standard deviation σ(g(M)) together with knowledge of the type of the probability density function (normal) of g(M), the probability of failure P_F(g(M)) of the investigated system is determined. Then, the effect of uncertainties of each physical properties on the probability of failure of the system is assessed.