One-Dimensional Shock-Induced Pore Pressure Response in Saturated Carbonate Sand

Abstract

Abstract Experiments were performed to investigate the transient undrained pore water pressure response of a shock-loaded saturated carbonate sand (Enewetak coral sand). Specimens were dynamically loaded using an experimental laboratory facility capable of generating compressive shock pulses with millisecond rise times to peak stress. Boundary conditions were for one-dimensional confined compressive loadings without drainage. Pore water pressure increases of 50% or more were observed at compressive strains above about 0.01%. For most tests, liquefaction was observed at peak compressive strains in excess of about 0.10%. An empirical equation for estimating pore water pressure increases from transient compressional shock loadings was developed from a statistical analysis of the data. A silica sand, Monterey No. 0/30, has also been previously tested in this apparatus and a comparison is made. The residual excess pore water pressure equations for Enewetak coral and Monterey No. 0/30 sands are presented. Test results indicate that the response of these two sands is markedly different. Residual excess pore water pressures are proportional to approximately the square root of peak compressive strain for Enewetak coral sand and approximately the cube root of peak compressive strain for Monterey No. 0/30 silica sand. Measured static C parameter values were consistently less than unity for all saturated specimens of Enewetak coral sand tested. The C parameter decreased with increasing specimen density and effective stress.