Sensitivity Analyses of the Seepage and Stability of Layered Rock Slope Based on the Anisotropy of Hydraulic Conductivity: A Case Study in the Pulang Region of Southwestern China

Abstract

In the study of the seepage characteristics of layered rock slope under rainfall conditions, the majority of previous research has considered the hydraulic conduction to be isotropic, or only considered the anisotropy ratio of the hydraulic conductivity, ignoring the anisotropy angle. In the current study, a layered rock slope in the Pulang region was selected as an example. Then, based on the fitting parameters of the Van Genuchten model, pore water pressure sensitivity analyses of the layered rock slope were carried out. The anisotropy ratio and anisotropy angle were used to analyze the sensitivity of the seepage and stability of the layered rock slopes. The results show that as the anisotropy angle of hydraulic conductivity of layered rock slope decreased, the maximum volume water content of surface (MWCS) of layered rock slope gradually increased. Additionally, as the anisotropy ratio decreased and the anisotropy angle increased, the rising heights of the groundwater (RHG) of layered rock slope gradually increased. When the hydraulic conduction of layered rock slope was considered isotropic, the factor of safety (FS) tended to be overestimated. As the anisotropy ratio decreased and the anisotropy angle increased, the factor of safety (FS) of layered rock slope decreased. Prevention should be the objective for rock slopes with larger dip angles in the bedding plane in the Pulang region. This study provides feasible schemes for the evaluation of the seepage and stability of layered rock slopes in Pulang region of southwestern China.

Deformation and Stability Characteristics of Layered Rock Slope Affected by Rainfall Based on Anisotropy of Strength and Hydraulic Conductivity

“…The slope in the present study is located on the west side of the slope in a previous study [9], and the difference of unsaturated parameters between the two rock slopes is negligible. Therefore, the parameters of the water retention curve of the present slope were referred from a previous study [9]. The unsaturated parameter values are shown in Table 1 [9].…”

“…To simulate the seepage processes of rock slopes, rainfall infiltration was regarded as the variable flow boundary of the unsaturated zone, and a saturated-unsaturated seepage theory was applied to perform the simulations. Under the principle of mass conservation, the saturated-unsaturated seepage control differential equation is as follows [3,9,30]:…”

“…The extent of the initial maximum matric suction may have varied, and the seepage states and stability levels of slopes may have also been quite different. Therefore, to make the initial matric suction more in line with the actual situation (refer to previous studies [9,35]), this study set the different maximum initial matric suctions as −50, −75, and −100 kPa, respectively, and the annual average rainfall of the Pulang area as 0.06 mm/h in the steady-state comparative analysis process. As detailed in Figure 5, the changes in the matric suction of the average annual rainfall were similar to the setting of the maximum initial matric suction of −75 kPa.…”

“…Rainfall is one of the main factors that trigger landslides [1]. In the past two decades, research on rainfall-induced soil landslides has been gaining popularity [2][3][4][5][6], but research on rock landslides is less reported [1,[7][8][9][10][11][12]. According to available statistical data, more than 90% of rock slope failures are related to fluid hydraulic conduction [13].…”

“…However, the rock slope was seriously weathered, while the Poisson's ratio and elastic modulus used for numerical simulation were from intact rocks, which would lead to inaccurate results. Yu et al [3] and Xia et al [9] studied the seepage, deformation, and stability of soil slopes based on the anisotropy of hydraulic conductivity; however, the influence of the anisotropy of elastic modulus and Poisson's ratio on the slope deformation and stability was ignored.…”