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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]

In this paper, the one-dimensional (1D) time-dependent behaviour of natural and reconstituted London Clay samples under saturated and unsaturated conditions is studied. For this purpose, a set of 1D consolidation tests including multi-staged loading (MSL) oedometer tests and single-staged loading (SSL) long-term oedometer creep tests were carried out on saturated and unsaturated specimens. Conventional oedometer cells were used for tests on saturated specimens, whereas a newly designed unsaturated oedometer cell, equipped with two high-capacity tensiometers (HCTs) for suction measurements, was used for unsaturated tests. The tests results revealed stress dependency and suction dependency of primary and secondary consolidation responses of the soil samples. Furthermore, counter to formerly acknowledged suggestions of independency of the slope of normal consolidation line to suction changes, it was observed that an increase in suction results in a decrease of the slope of compression curve ([C.sub.c]) and the creep index ([C.sub.[alpha]e]) values and an increase in yield vertical net stress ([[sigma].sub.p]). Moreover, the [C.sub.[alpha]e]/[C.sub.c] ratio for London Clay was found to be stress- and suction-dependent, unlike the previously suggested hypotheses. Key words: stiff clay, creep, oedometer, suction, unsaturated soils. Dans cet article, le comportement unidimensionnel (1D) dependant du temps d'echantillons d'argile de London naturels et reconstitues dans des conditions saturees et non saturees est etudie. A cette fin, une serie de tests de consolidation 1D, comprenant des tests oedometriques a chargement en plusieurs etapes (MSL) et des tests de fluage a long terme pour un chargement en une etape (SSL), a ete realisee sur des echantillons satures et non satures. Les cellules oedometriques conventionnelles ont ete utilisees pour les tests sur des echantillons satures, tandis qu'une cellule oedometre non saturee de conception nouvelle, equipee de deux tensiometres a haute capacite (HCT) pour les mesures d'aspiration, a ete utilisee pour les tests non satures. Les resultats des tests ont revele une dependance vis-a-vis du stress et de la succion des reponses de consolidation primaire et secondaire des echantillons de sol. En outre, contrairement aux suggestions precedemment admises concernant l'independance de la pente de la ligne de consolidation normale vis-a-vis des modifications de la succion, il a ete observe que l'augmentation de la succion induit une diminution de la pente de la courbe de compression ([C.sub.c]) et des valeurs de fluage ([C.sub.[alpha]e]) et une augmentation de la contrainte nette verticale du rendement ([[sigma].sub.p]). De plus, le rapport [C.sub.[alpha]e]/[C.sub.c] de London Clay etait dependant du stress et de la succion, contrairement aux hypotheses precedemment suggerees. [Traduit par la Redaction] Mots-cles: argile raide, fluage, oedometre, succion, sols non satures., Introduction Experimental investigations have proven dependency of the mechanical behaviour of clays on time effects (Li et al. 2003; Mesri 2009; Karstunen and Yin 2010; Bagheri et al. 2015; Yin [...]

The paper presents an experimental investigation of very small strain stiffness of unsaturated sand. A triaxial test apparatus was equipped with bender elements and compression discs in order to assess the stiffness at very small strains by measuring the velocity of propagation of shear and compression waves through an unsaturated sample. The negative water column method was adopted to apply suction at the base of the sample. The experiments were designed to investigate the independent effect of suction and degree of saturation on the wave propagation velocities. This was achieved by testing the sand sample on both the drying and wetting path.

Abstract: In this paper a new approach is presented, based on evolutionary polynomial regression (EPR), for determination of liquefaction potential of sands. EPR models are developed and validated using a database of 170 liquefaction and non-liquefaction field case histories for sandy soils based on CPT results. Three models are presented to relate liquefaction potential to soil geometric and geotechnical parameters as well as earthquake characteristics. It is shown that the EPR model is able to learn, with a very high accuracy, the complex relationship between liquefaction and its contributing factors in the form of a function. The attained function can then be used to generalize the learning to predict liquefaction potential for new cases not used in the construction of the model. The results of the developed EPR models are compared with a conventional model as well as a number of neural network-based models. It is shown that the proposed EPR model provides more accurate results than the conventional model and the accuracy of the EPR results is better than or at least comparable to that of the neural network-based models proposed in the literature. The advantages of the proposed EPR model over the conventional and neural network-based models are highlighted. [Copyright &y& Elsevier]

Abstract: Determination of liquefaction induced lateral displacements during earthquake is a complex geotechnical engineering problem due to the complex and heterogeneous nature of the soils and the participation of a large number of factors involved. In this paper, a new approach is presented, based on genetic programming (GP), for determination of liquefaction induced lateral spreading. The GP models are trained and validated using a database of SPT-based case histories. Separate models are presented to estimate lateral displacements for free face and for gently sloping ground conditions. It is shown that the GP models are able to learn, with a very high accuracy, the complex relationship between lateral spreading and its contributing factors in the form of a function. The attained function can then be used to generalize the learning to predict liquefaction induced lateral spreading for new cases not used in the construction of the model. The results of the developed GP models are compared with those of a commonly used multi linear regression (MLR) model and the advantages of the proposed GP model over the conventional method are highlighted. [Copyright &y& Elsevier]