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In this paper, an anisotropic non-associative constitutive model, based on the well-established critical state soil mechanics framework, is developed for the natural and reconstituted clays subjected to monotonic and cyclic loadings. A robust non-elliptical yield surface is implemented in the model which enables it to capture a wide variety of yield stress points. In addition to a realistic soil stiffness simulation, the employed flexible plastic potential surface equips the proposed model to predict a more accurate coefficient of earth pressure at rest. The model uses a combination of conventional volumetric and comprehensive rotational hardening rules to control the evolution of the yield surface caused by plastic strain increments. The adopted rotational hardening rule uses the concept of governing plastic strain increment which not only ensures the existence of the equilibrium state of anisotropy but also takes the effect of plastic strains at different constant stress ratios into account more sensibly. The proposed model is enhanced with a novel double-image stress point bounding surface plasticity type theory to capture nonlinear behaviour inside the yield surface, and also to simulate the cyclic responses. The detailed model formulation is discussed in both triaxial stress space and the e - ln p plane, and the important features of the model are elaborately explored. The capabilities of the model are also demonstrated by an extensive sensitivity analysis. In the end, the model is used to carry out simulations of monotonic and cyclic element tests on different clays and the results are compared with the available experimental data. [ABSTRACT FROM AUTHOR]

Natural soils often exhibit an anisotropic fabric pattern as a result of soil deposition, weathering, or filling. This paper aims to investigate the effect of soil interdependent anisotropy and fabric orientation on runout motions of landslides and evaluate the most critical fabric orientation for the post-failure behavior. The shear strength properties of soil deposit (i.e., cohesion c and friction angle φ ) are modeled as negatively cross correlated bivariate random fields. The results reveal that the spatial variability and the negative cross-correlation of c and φ notably influence the post-failure behavior. In addition, the rotation of soil layer orientation significantly affects the runout motion. Based on the analyses, the deposition orientation of 30 ∘ is identified to produce the highest mean value and standard deviation of the runout distance. The findings from this study highlight the importance of considering the orientation of soil stratification, rather than only the magnitude of shear strength, in assessing the post-failure behavior of a landslide. [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]

In this paper, an adaptive anisotropic constitutive model, namely AA1‐CLAY, is developed for clays based on the critical state framework. The model has a non‐associated flow rule, and it can also reduce to basic critical state constitutive models. A versatile yield surface (YS) is implemented in the model which can generate a broad range of shapes to improve the possibility of capturing experimental yield points of different clay types with high accuracy. In addition to the isotropic hardening rule, an innovative rotational hardening (RH) rule is also incorporated into the model to control the YS rotation rate. The proposed RH rule uses a transitional function to govern the effect of plastic strains at different constant stress ratios more realistically. Furthermore, the equilibrium state of anisotropy, which the YS tends to reach during plastic straining, is defined uniquely based on the experimental findings. The detailed model formulation is presented, and important features of the model are elaborately discussed. The capabilities of the model are also demonstrated by comparing the simulation results of several element tests on a number of different clays against the available experimental data. [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 this paper, a multi-surface anisotropic constitutive model is proposed for clayey soils, based on bounding surface theory and a classical anisotropic critical state-based model. In the proposed model, in addition to the volumetric hardening law, a rotational hardening rule is also incorporated into the bounding surface formulation with a non-associated flow rule. The model uses the bounding surface plasticity theory to produce a more realistic representation of the nonlinear behavior of clays with high overconsolidation ratios. Detailed model formulation is presented including an innovative approach to find image stress points on the bounding surface which offers an original conception of changing the projection center, even at the absence of plastic loading. A modified procedure is also discussed to improve the performance of the proposed model for simulating the response of highly overconsolidated clays. The proposed modifications, together with the novel mapping rule, form a new framework that can be used to improve the simulation capabilities of different constitutive models that have elliptical yield/bounding surfaces. The efficiency of the framework is demonstrated by comparing the simulation results against element test data from a number of different clays at lightly to highly overconsolidated conditions. The new model shows promising capabilities in capturing the important aspects of natural clays response during straining, in particular for the combined effects of small strain nonlinearity with fabric orientation. [ABSTRACT FROM AUTHOR]

Globally, coal mining wastes (CMWs) are associated with significant environmental and economic costs. Processing CMW into an ingredient of foam concrete is a promising solution but the behaviour of this particular construction material has not been sufficiently evaluated, especially during the initial period of cement hydration. The purpose of this paper is to present novel laboratory set-up and experimental procedures designed to investigate the early age behaviour of hydrating foam concrete samples made with a CMW from Poland. Two types of tests were devised to simulate air-curing conditions and water-curing conditions, respectively. These tests were carried out in custom-built unsaturated oedometer cells, and the matric suction in the test samples was monitored for approximately 14 days, using Warwick high capacity tensiometers. Experimental results show that in both curing conditions, a higher matric suction during cement hydration corresponds to a denser sample at the end of the monitoring period. A comparison of water-cured and air-cured samples also reveals different responses to CMW inclusion in their mix designs. The responses can be convincingly explained based on complementary test data and idealised capillary tube models adapted for the hydrating foam concrete samples. • A novel laboratory set-up, incorporating high capacity tensiometers (HCTs) into purpose-built unsaturated oedometer cells, is proposed to investigate the curing behaviour of foam concrete during early age hydration. The incorporation of the HCTs made it possible to directly monitor the matric suction evolution of the mix and the corresponding interplays depending on the foam concrete samples' (water- or air-) curing conditions. • The influence of natural sand replacement by coal mining waste (CMW) in the foam concrete mix has been studies, together with the corresponding effects on the evolutions of matric suction and porosity during the early age hydration. • Two different types of tests were devised for measuring the impacts of different curing environments on foam concrete properties. The first type was adapted for a water-curing condition and is akin to a chemical shrinkage test. The second type was adapted for an air-curing condition where water inflow was not permitted into the hydrating foam concrete sample over the monitoring period. In both cases. The evolution and interplays of matric suction were studied in correspondence with formation/stabilisation of the pore networks. • Simplified capillary models are proposed that meaningfully describe the rather complex kinetics of foam concrete hydration associated to the matric suction variations. [ABSTRACT FROM AUTHOR]

Coseismic landslides are common secondary earthquake geohazards in meizoseismal areas. Newmark sliding block permanent displacement method has been widely adopted to develop regional coseismic landslide hazard maps. However, uncertainties from the slope parameters (e.g., cohesion, pore water pressure, and block thickness) are not commonly considered in the ground displacement predictions. This study proposes a novel framework that consists of two uncertainty assessment methods of Monte Carlo and logic tree simulations (MCS and LTS) with seven different displacement regression functions to predict the regional coseismic landslides' permanent displacement. Compared with the existing methods, the proposed framework is argument-driven, avoiding huge number of repetitive simulations. The Jiuzhaigou earthquake, in China, is considered as an illustrative example to compare the performance of the framework with considered regression functions. The corresponding results show that using LTS, with a certain regression function, leads to better predictions compared to using MCS. It is demonstrated that the proposed framework can provide a meaningful measure for making informed decisions to diminish the potential risk of earthquake induced landslides, and/or generating emergency strategies to mitigate post-earthquake consequences. It should be noted that the application of the proposed method for deposits where the soil strength parameter values do not fit the normal distribution may be limited as only normal distribution for soil strengths is considered in this study. [ABSTRACT FROM AUTHOR]

Historically coal mining wastes have been viewed as heterogenous and hazard-prone geomaterials. Given that failures of colliery tips and tailing dams are reported on a regular basis, reclamation of coal mining wastes from storage facilities is increasingly being considered. There is a resistance to the use of coal mining waste in construction industry despite scattered but growing reports of successful applications. As the construction industry around the globe seeks to reduce its carbon emissions by looking for supplements for cement, the voluminous amount of coal mining wastes currently stored in spoil heaps and impoundment facilities present a potential source of raw materials. This article reviews the literature on the geochemical, geotechnical and structural engineering properties of coal mining waste geomaterials to assess their suitability as replacement for both aggregates and binders in concrete and cementitious composites (as opposed to reviewing the properties of those products themselves). It is found that coal mining wastes are indeed good candidates (as raw materials) for the uptake and process into higher level construction purposes. Geochemically, the key to a successful upcycling operation is the knowledge of their mineral contents (which is typically diverse and varies from one mine to another) and the processes they undergo while being transformed into constituents of new materials. The few studies on concretes made with coal mining wastes indicate that the mineralogical and mechanical characterization of the wastes to obtain a mix featuring strength and durability performance that meets specification is important to a successful utilization. In the geotechnical literature, coal mining wastes are known to be highly heterogeneous and may host expandable minerals with potential durability problems. However, this review also found that simple geotechnical index tests can be conducted to yield useful information for the initial screening of coal mining wastes into a construction product. The state-dependent properties of coal mining wastes (e.g., water retention, hydraulic conductivity, shear strength) are found to be governed by complex factors such as coal content, particle size and shape, pore size and shape, and the presence and interaction of pore air and pore water in the void space, some of these are well-studied but much of these are to be further researched. [ABSTRACT FROM AUTHOR]