Spatial Variability of the Undrained Strength of Clays

The objective of this study is to provide a simple yet accurate procedure for the description of the spatial variability of the undrained shear strength S_u of soft clays. This is achieved on the basis of experimental findings and field observations of the depth-dependent nature of S_u. The main features of the method are a linear with depth variation of the mean value and standard deviation of S_u and a smooth exponential function that describes the correlation between values received by S_u at different vertical locations. The developed procedure is illustrated in a case study involving actual strength data. Two sites are selected from the general area investigated in connection with the West Side Highway in New York City. Each site is characterized by the values of S_u obtained along two boreholes using field vane shear tests. The results of the applied analysis verify previous findings on the vertical variability of S_u and demonstrates the applicability of the present procedure in the commonly encountered situations with limited data.