Volumetric Changes and Point of Saturation around a Pressuremeter Probe Used in Unsaturated Soils

Abstract

The interpretation of pressuremeter test results in cohesive soils assumes that the soil is saturated and the rate of loading is such that undrained conditions apply. Pressuremeter tests in compacted soils or heavily overconsolidated clays may have a degree of saturation that is less than 100%. Consequently, the soil may undergo volume changes during the initial stages of loading. Loading of the soil will result in the compression of occluded air and consequently the initial circumferential strains may be a function of volumetric changes and not a result of borehole expansion alone. A method to determine the applied radial total stress that will result in saturation for the pressuremeter test is developed based on Hilf’s method of pore water pressure prediction during compressive loading of an unsaturated soil. A method to quantify the volume change that will occur within the plastic region around the pressuremeter probe prior to saturation is also developed.