Abstract
Based on the characteristics of an expansive soil slope, the slip mass can be simplified to a simpler model with three-broken line rigid bodies. A solution was formulated to calculate the safety factors of the slope, and the results are similar to those based on the strength reduction method. However, similar to conventional methods to analyze the stability of slopes, the deterministic method to obtain the safety factors only calculates the safety factor using deterministic values without considering the randomness of soil parameters, which leads to unstable results. To improve the rationality of the calculated results, this paper aims to construct a reliability analysis method based on the simplified three-broken line model of a landslide. The reliability is calculated with the response surface method in a spreadsheet with efficiency and convenience. The designed program considers the changes in the strength of the shallow soil and the depth of the strongly weathered layer for different stages of the wetting-drying cycles and solves for the probability of failure of the sliding surface at the interface between the strong and weak weathered layers. Considering an expansive soil slope as an example, the reliability of the slope was analyzed based on laboratory test data and the proposed formula. The results show that multiple wetting-drying cycles significantly increase the probability of failure of an expansive soil slope and that the slope typically becomes unstable after six wetting-drying cycles. Slope cutting helps alleviate the adverse effects of wetting-drying cycles.
Highlights
Expansive soils are typical of problematic soils [1, 2]—a kind of high-plastic clay with an expansive structure, multifissures, strong expansion, and contraction, as well as strength attenuation. ey can be widely discovered all over the world [3], which may cause engineering problems [4, 5]
To verify the accuracy of the model proposed in this paper, FLAC was applied based on the method proposed by Yin and Bin to evaluate the stability of a slope selected near the Qinhuai River in Nanjing, Jiangsu Province, China, and the results were compared with the results obtained with the integral rigid body equilibrium method. e width of the landslide body was about 80 m; the length of the main axis was about 30 m; the width of the back edge crack was 0.3–1.0 m; the depth was 2.0 m; and the height of the back edge wall was 1.0 m
Excel software does not have an inherent quadratic fitting function, it can assume that the quadratic term is a random variable, obtain the response surface function with the help of the built-in function “Linest,” and calculate reliability by Visual Basic for Applications (VBA) programming without the aid of “SOLVER,” which avoids frequent calls to “SOLVER” in the iterative process, and calculation crashes due to parameter problems
Summary
Expansive soils are typical of problematic soils [1, 2]—a kind of high-plastic clay with an expansive structure, multifissures, strong expansion, and contraction, as well as strength attenuation. ey can be widely discovered all over the world [3], which may cause engineering problems [4, 5]. Based on the fuzzy recognition theory and the analytic hierarchy process (AHP), Jian et al [11] worked out a recognition model to evaluate the stability of expansive soil slopes. Wen et al [13] managed to apply a multistage fuzzy comprehensive evaluation model to an unloading high-steep slope, whose stability analysis shows great feasibility. Based on the fish and Gaussian process regression (GPR) model, Peng et al [14] proposed a numerical model and applied it to Mathematical Problems in Engineering dynamic predictions of shallow sliding failures of expansive soil slopes. There are still some deficiencies in the analytical formula of safety factors, which can reflect the stability of expansive soil slopes
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