Instability of High Liquid Limit Soil Slope for the Expressway Induced by Rainfall

Abstract

The instability of high liquid limit soil slope is a common engineering problem in highway construction. This study focused on the slope at section K79 + 880 of the Guang-Le Expressway in Guangdong Province, China. In order to reduce the landslide and learn the mechanism of the high liquid limited soil slope, the effects of different rainfall intensities and rainfall time on the high liquid limit soil slope were studied by in-site monitoring and numerical simulation. According to the characteristics of the slope deformation and the monitoring data, the slope landslide is divided into three grades. Numerical simulation results show that the influence of rainfall intensity on the safety factor of high liquid limit soil slope is greater than that of rainfall time. At the slope top, the cumulative changes of Mises stress in Group B and Group C were −2.19 kPa and −2.91 kPa, respectively, and the cumulative decreases were −7.22% and −9.60%, respectively. At the slope bottom, the cumulative changes of Mises stress in Group B and Group C were −2.05 kPa and −4.32 kPa, respectively, and the cumulative decreases were −4.50% and −9.48%, respectively. With the increase of rainfall for 24 h, the safety factor of Group C decreased by an average of 0.0408, and with the increase of rainfall time, the safety factor increased, and the safety factor of 96 h of rainfall in Group C was 0.1249 lower than that of 24 h of rainfall. The greater the rainfall intensity, the greater the change of matrix suction at the top of the slope, and the more prone the top of the slope to shallow landslides. For the high liquid limit soil slope, slope instability phenomena such as surface flow collapse occur easily and have little impact on the deep sliding surface. The dimensionless displacement coefficient K is proposed to quantify the landslide displacement under different rainfall. A general method is proposed to measure the cumulative displacement of the K79 + 880 slope where the sensor is not placed.