Pore Pressure Rise of Saturated Sands During Cyclic Loading,

摘要

A new method can predict the pore pressure rise in a sand deposit during dynamic loading. The method is applicable to any type of dynamic loading (from uniform cyclic to random time history of loading such as imposed by actual earthquakes). The authors have found that the incremental rise in pore pressure for a given soil under a given condition during one cycle of loading is affected by three major factors--stress history,cyclic effect,and stress intensity. These factors are defined in terms of pore pressure rise at the end of the preceding cycle,the equivalent number of cycles,and the stress ratio. The method presented is used to determine the liquefaction potential of a sand with different densities under various types of loading,including actual earthquakes. Since this method is based on direct laboratory measurements,the authors believe that it is more dependable and easily applicable to various sands. The liquefaction potential of partially saturated sands is also investigated. It is shown that partially saturated loose sands do liquefy and their liquefaction potential decreases with the decrease in the initial degree of saturation of the soil.