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

Abstract

International audienceUsing 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/m(3) 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 A degrees 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

Investigation on chemical effects on GMZ bentonite used as buffer materials

“…The shape of the swelling pressure evolution curve was characterized by these two peaks (Fig. 7) and was in accordance with results achieved in similar studies using GMZ bentonite ( [70,68]) and FEBEX bentonite ( [71]). …”

About differences of swelling pressure — dry density relations of compacted bentonites

“…Furthermore, the swelling pressure significantly depends on the type of water the bentonite is exposed to (Karnland, 1997;Xie et al, 2007;Karnland et al, 2007;Herbert et al, 2008;Lee et al, 2012). Lloret (2004, 2008) and Lee et al (2010) reported decreasing swelling pressure with increasing temperature while Shirazi et al (2010) and Ye et al (2013) found increasing swelling pressure with increasing temperature. Birgersson et al (2010) reported on a theoretical relation of the swelling pressure on the temperature and could prove and calculate a marked drop of the swelling pressure upon freezing.…”

Effect of Sodium Chloride Concentration on Saturated Permeability of Remolded Loess

“…where K sat is the saturated hydraulic conductivity (cm/s), Q is the quantity of water (cm 3 ), A is the cross-sectional area perpendicular to flow (cm 2 ), t is the time (s) required for Q to be discharged, i is hydraulic gradient, h is the head difference between the top and the bottom of the soil specimen (cm), and L is length of the seepage path (i.e., the height of the sample) (cm). The influence of temperature on saturated permeability cannot be neglected [6,[34][35][36]; therefore, the test apparatus was placed in an SHH-C3000 constant temperature controller (China) with a range of 0-60 • C and an accuracy of 0.1 • C. In this study, 20 • C was set as the standard temperature to avoid the correction of K sat [37]. Moreover, the hydraulic gradient was set to 3 to ensure sufficient discharge for the water chemical analysis.…”