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This paper presents the probabilistic analysis of landslides in spatially variable soil deposits, modeled by a stochastic framework which integrates the random field theory with generalized interpolation material point method (GIMP). Random fields are simulated using Cholesky matrix decomposition (CMD) method and Latin hypercube sampling (LHS) method, which represent material properties discretized into sets of random soil shear strength variables with statistical properties. The approach is applied to landslides in clayey deposits under undrained conditions with random fields of undrained shear strength parameters, in order to quantify the uncertainties of post-failure behavior at different scales of fluctuation (SOF) and coefficients of variation (COV). Results show that the employed approach can reliably simulate the whole landslide process and assess the uncertainties of runout motions. It is demonstrated that the natural heterogeneity of shear strength in landslides notably influences their post-failure behavior. Compared with a homogeneous landslide model which yields conservative results and underestimation of the risks, consideration of heterogeneity shows larger landslide influence zones. With SOF values increasing, the variances of influence zones also increase, and with higher values of COV, the mean values of the influence zone also increase, resulting in higher uncertainties of post-failure behavior.

Rainfall infiltration analysis has a great significance to the mitigation and risk assessment of rainfall-induced landslides. The original Green–Ampt (GA) model ignored the fact that a transitional layer exists in infiltration regions of soils under the rainfall permeation; moreover, it cannot effectively analyze the rainfall-infiltrated heterogeneous slope considering the spatial variability of saturated hydraulic conductivity (ks). In this study, an improved GA model is proposed for the rainfall-infiltration analysis of heterogeneous slopes. Four common slope cases are investigated to validate the effectiveness of the proposed model. An infinite slope model is taken as an illustrative example to investigate the distributions of volumetric water content and slope stability under the rainfall infiltration. The results show that the distributions of volumetric water content and factor of safety (Fs) obtained from the proposed model are in very good agreement with the numerical results of the Richards' equation. In contrast, the modified GA model obtains biased distributions of volumetric water content and smaller Fs for the same cases. The results show that the proposed GA model can accurately identify the location of critical slip surface of the slope, and as such it provides an efficient method for risk analysis and control of slopes susceptible to landslide. [ABSTRACT FROM AUTHOR]

This paper proposes a new method of reusing uncalcined coal gangue (UCG) as a mineral admixture in magnesium ammonium phosphate cement (MAPC) blended with fly ash (FA). The effects of UCG on setting time, workability, hydration heat release, mechanical properties, hydration products, and microstructure of MAPC composites were systematically investigated. The results indicate that the addition of UCG decreased the maximum hydration temperature and extended the setting time of MAPC composites. The compressive strength of MAPC was improved by introducing an optimal amount of UCG. The XRD results showed no new crystal phase in UCG-0 (with 20% FA and 0% UCG) and some secondary hydration products, such as berlinite and lizardite, were observed in MAPC with UCG. The addition of UCG was found to inhibit the generation of dittmarite and promote the development of struvite. Results showed that differences in the crystal morphology of struvite and dittmarite influence the compressive strength of MAPC composites. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of temperature variations on the creep and stress relaxation behavior of clay samples from London Bank Station. The independent and coupled effects of strain rate and temperature on one-dimensional (1D) stress–strain and stress relaxation responses were investigated based on a series of temperature-controlled constant rate of strain (CRS) compression–relaxation tests carried out at fast, intermediate, and slow displacement rates and over 20°C–55°C. The temperature effect on the creep index (Cα) was investigated based on a series of temperature-controlled multistage loading (MSL) oedometer tests. The results of the CRS compression–relaxation tests showed that with the increase in temperature, the coefficient of stress relaxation (Rα) decreases for samples that were loaded at fast and intermediate prerelaxation displacement rates (υ˙); however, it increases for samples loaded at the slow prerelaxation displacement rate. A decrease in υ˙ by a factor of 10 (i.e., from 0.010 to 0.001 mm/min) causes the Rα values to reduce by 55%–11% with the temperature increase. The increase in temperature caused an increase in Cα that were obtained from the MSL tests. The maximum value of Cα increased by 18% from 35°C to 45°C and by 37% from 45°C to 55°C. The temperature effects on other conventional parameters that included the preconsolidation pressure, and the compression and swelling indexes (Cc and Cs) were comparable with the findings reported in the literature. Comparing Cα that were obtained from the MSL tests and Rα that were obtained from the CRS tests supports the validity of Rα=Cα/Cc correlation for thermally influenced saturated reconstituted clays and that the time-dependent soil parameters could be obtained from relatively fast CRS compression–relaxation tests as an alternative to conventional time-consuming oedometer tests. [ABSTRACT FROM AUTHOR]

In landslide analysis, reliable prediction of landslide's influence zone is significantly difficult due to the inherent heterogeneity of soils and their spatially varying geological properties. In this paper, a probabilistic framework is proposed to evaluate the landslide hazard zoning through the prediction of their influence zone considering the effects of heterogeneous soil properties. The material point method is used to simulate the large deformations during landslide failure. The spatial variation in the shear strength parameters of soils at undrained conditions is modeled by random fields, which are discretized by the Cholesky matrix decomposition method to incorporate the effects of the soil spatial heterogeneity on the postfailure deformations. Furthermore, a practical landslide hazard zoning is conducted to quantitively evaluate the level of disaster for facilities or structures located in the vicinity of the slope by using the exceedance probability of influence distance and runout distance. Five categories based on different thresholds of exceedance probability are used to visualize the area potentially affected by the landslide. To demonstrate the capability of the stochastic assessment framework, a benchmark example of the heterogeneous clayey slope is simulated, and the associated hazard zone is predicted and discussed; it presents a practical procedure for improving the landslide influence zone prediction and provides new insights for hazard zoning. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of the soil moisture evaporation rate on the soil water retention curve (SWRC) of clays obtained using the high-capacity tensiometer (HCT) technique and following the continuous drying (dynamic) method. SWRC measurements, with and without soil moisture evaporation rate control, were carried out on reconstituted London clay specimens using 12 performance-improved HCTs recently developed at the University of Warwick. Furthermore, the HCTs' performance in terms of the maximum attainable suction (smax) and maximum measurement duration (tmax) was evaluated. Moreover, the suitability of a curve-fitting-based model, available in the literature, for attaining the entire retention curve (beyond the capacity of HCTs) was evaluated. The SWRCs for the tests with a controlled evaporation rate were found to generally exhibit higher suction at a given water content, hence inducing air-entry values that were on average 16% higher than those obtained from tests without evaporation rate control. It was also found that for suction in excess of 2 MPa, the curve-fitting-based model predictions of data obtained from tests with a controlled evaporation rate exhibited significantly lower suction at a given water content than those without evaporation rate control, suggesting that such curve fitting correlations should be used with caution. [ABSTRACT FROM AUTHOR]