Temperature effects on the swelling pressure and saturated hydraulic conductivity of the compacted GMZ01 bentonite

Abstract

Using a newly developed apparatus, swelling pressure tests and saturated hydraulic conductivity tests on the compacted Gao-Miao-Zi (GMZ01) bentonite with an initial dry density of 1.7 Mg/m3 were conducted at various temperatures. Based on the test results, the mechanisms of influence of temperature on the swelling pressure and saturated hydraulic conductivity were analyzed. Results indicate that swelling pressure increases with the increase in temperature. The swelling pressures measured at 20 and 40 °C are 3.02 and 3.41 MPa, respectively. For a given temperature, the swelling pressure increases rapidly at the beginning of the infiltration process and then reaches a first peak value followed by an intermediate period characterized by a decrease of swelling pressure, well before the clay reaches its full saturation. The saturated hydraulic conductivity of the GMZ01 bentonite also shows an increase with temperature rise. The temperature changing paths (heating or cooling) have no effect on the saturated hydraulic conductivity. Based on the test results, models for prediction of saturated hydraulic conductivity of the compacted GMZ01 bentonite have been developed and verified. It was observed that the model that only considers the temperature effect on water viscosity gives predictions with large deviation from the measured values, moreover, the deviation increases with temperature rise. When considering both the temperature influence on water viscosity and the effective flow cross-sectional area of porous channels, the model can satisfactorily account for the temperature effects.