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Studies of the volume change behaviour of saturated and unsaturated fine-grained soils upon exposure to various types of fluid are of significant interest while dealing with contaminated soils. In this study, the one-dimensional volume change behaviour of two clays (Spergau kaolin and Calcigel bentonite) with dominant minerals as kaolinite and montmorillonite was studied by inundating several initially unsaturated and saturated clay specimens with water and a non-polar organic liquid (heptane). For both cases, applied vertical pressures of 25 and 100 kPa were considered under oedometric conditions. The magnitude of compression and swelling deformations of the clays were found to be strongly dependent upon the mineralogy of clays, dielectric properties of the pore-fluid, initial compaction conditions, and applied stress during the wetting process. The test results indicated distinct interactions between unsaturated clays and water. Specimens of Spergau kaolin exhibited compression with water, whereas specimens of Calcigel bentonite exhibited swelling. Compression and swelling deformations of the clays with heptane as the inundating liquid remained within about ±1.0% for both clays indicating a very minor interaction between unsaturated clays and molecules of this non-polar organic liquid. The test results emphasized the significance of attractive and repulsive forces and their impact on the volume change behaviour of clays of different mineralogy. [ABSTRACT FROM AUTHOR]

Stabilisation of expansive soil using lime or sand is an effective improvement technique as it reduces the swelling ability of the soil. The aim of this paper is to study the influence of different lime fractions and lime-sand mixtures on the behaviour of highly expansive clay by performing swelling and strength tests on each mixture. Calcium (Ca)-bentonite is utilised as highly expansive clay. All samples were remoulded according to the results of the modified compaction Aashto test. Non-treated bentonite possesses high values of swelling and strength. Mixing lime and sand with clay causes significant reductions in swelling characteristics. The reductions increase effectively with the increase in lime and sand content. The swell potential and the swelling pressure of the clay almost vanish when stabilised by 10% lime and 50% sand. Generally, adding only lime into clay leads to an increase of its California bearing ratio (CBR) and unconfined compressive strength (UCS), whereas mixing clay with both lime and sand leads to an increase in the CBR values. The CBR values increase significantly with the increment of their content. For a >30% sand content, the UCS of the lime-clay mixtures decreases on increasing the sand fractions, whereas the UCS values increase with a longer curing time. The CBR and UCS-56 d curing time of the stabilised clay with 10% lime and 50% sand increase to twice the values for the non-treated clay. [ABSTRACT FROM AUTHOR]

In this study, the volumetric behaviour, hydraulic permeability and micro-fabric of clay-polymer composites fabricated by the use of polyacrylamide polymers were experimentally investigated and discussed by use of theoretical multiscale approaches. Composites were varied systematically in composition taking into account constitutive properties controlling clay-polymer interaction, i.e., clay mineralogy (kaolinite and montmorillonite dominated clays with predominantly mono- and divalent counterions, respectively) and polymer charge (nonionic, cationic, anionic). Composites were produced according to their individual maximum adsorbing capacity and prepared to slurry conditions. 1D compression and rebound tests were performed (2–800–25 kPa) and the hydraulic permeability was calculated for each loading increment. Additionally, microscopic investigations in environmental scanning electron microscope were performed. It was found that cationic and anionic polymer adsorption promote aggregated and flocculated clay fabrics, respectively, whereas nonionic polymers promote dispersed clay fabrics. Macroscopically, this led to an increase in void ratio at the same stress level as well as to an increase (cationic polymers) or decrease (nonionic polymers) in hydraulic permeability. Micro- and macroscopic findings were theoretically analysed by use of diffuse double-layer (DDL) theory and cluster-model. A modified approach of DDL theory accounting for the effect of adsorbed nonionic polymers on the electric potential in the nearfield of clay mineral surfaces was derived. Theoretical results were found to be in good agreement with experimental results on volumetric behaviour. By use of cluster-model, hydraulic permeabilities were found to correlate to the microscopic findings on clay micro-fabric. [ABSTRACT FROM AUTHOR]

Calcigel bentonite-polyacrylamide (PAA) composites were investigated for their formation characteristics and their macroscopic hydro-mechanical and microscopic structural properties. The composites prepared were different in terms of the polymer charge, i.e. cationic (PAA+), anionic (PAA-), non-ionic (PAA°) and in terms of the polymer-to-clay ratio. The latter varied according to the individual maximum sorption capacity established from adsorption isotherms. Oedometer and waterretention testswere conducted on composites prepared under initial slurry conditions. The microstructure of the composites was investigated using environmental scanning electron microscopy (ESEM). At low stress, distinctly increased void ratios were found for all types of the composites, whereas under highstress conditions only the PAA+-composite prepared at 100% of the maximum sorption capacity showed an increase in void ratio. Analyses by ESEM on this composite indicated structural changes related to the preferential face-to-face aggregation, which help to explain the macroscopic behaviour and also account for the increased hydraulic permeabilities observed. [ABSTRACT FROM AUTHOR]

The excess pore water pressure produced during earthquake shaking causes liquefaction and influences significantly the shear strength, deformation and settlement characteristics of granular soil deposits. Therefore, the stability of the structures constructed from these deposits or founded on them is adversely affected. The mechanisms of pore pressure generation and, in turn, liquefaction resistance of granular soils are still not fully clear and require further research. For the purpose of clarifying and evaluating pore pressure buildup characteristics of sandy soils, a series of undrained monotonic triaxial tests were carried out on different reconstituted samples of sand-silt mixture at various intergranular void ratios. The soil samples were tested under a constant confining pressure ( $${\sigma_{3}'=100 {\rm kPa}}$$ ) and at three relative densities ( D = 20, 53 and 91 %). The results obtained from this study reveal that the fraction of low plastic fines plays an important role in the generation of excess pore water pressure in samples of the Chlef sand-silt mixtures. It was found that excess pore water pressure can be correlated with the undrained shear strength at the peak for the range of fines' content under consideration. The gross and intergranular void ratios appear as pertinent parameters to represent the pore water pressure response of the sand-silt mixtures for a given fines' content. [ABSTRACT FROM AUTHOR]

Dieser Beitrag befasst sich mit dem Einfluss einer mikrobiologischen Anreicherung auf das Quellverhalten von Bentoniten. Die Anreicherung erfolgte organismenunspezifisch über die Zugabe einer Energie- und Kohlenstoffquelle (C6H12O6) zu Materialmischungen, bestehend aus 30 % Bentonit und 70 % natürlichem Schluff (Biostimulation). Es wurden zwei Bentonite untersucht, die sich hinsichtlich ihrer Zwischenschichtkationen unterscheiden: Calcigel mit hauptsächlich Ca++-Kationen und MX 80 mit hauptsächlich Na+-Kationen. Beide Bentonite weisen ein unterschiedliches Quellverhalten auf, welches beim Calcigel maßgeblich durch innerkristallines und beim MX 80 maßgeblich durch osmotisches Quellen bestimmt ist. Es hat sich gezeigt, dass eine stoffwechselbedingte Gasbildung die Volumenänderung der Calcigelproben deutlich beeinflusst, während die Wasseradsorption weitgehend unbeeinflusst bleibt. Die MX-80-Proben hingegen zeigen ein deutlich verringertes osmotisches Quellvermögen infolge der mikrobiologischen Anreicherung. Als direkte Folge der Anreicherung wurde für beide Bentonite eine Reduktion des pH-Werts von 7,4 auf 4,8 im Porenfluid festgestellt, was die Reduktion des stark milieuabhängigen osmotischen Quellvorgangs erklärt. Investigations on the swelling potential of bentonites influenced by biostimulation. This contribution addresses the influence of microbiological accumulation on swelling behaviour of bentonites. Therefore, materials composed of 30 % bentonite and 70 % natural silt have been treated with C6H12O6 acting as an energy as well as carbon source in order to initiate microbiological growth of the present population (biostimulation). Two bentonites have been investigated differing in terms of their interlayer cations: Calcigel primarily exhibiting Ca++ cations and MX 80 primarily exhibiting Na+ cations within the interlayer space. Due to this compositional difference Calcigel swelling is significantly determined by processes of innercrystalline swelling, whereas MX 80 bentonite exhibits distinctive osmotic swelling. It was found that metabolic processes leading to gas generation within the samples have a great influence on volume change of Calcigel mixtures, whereas water adsorption of the same samples was rarely affected. On the other hand, samples of MX 80 mixtures exhibit a significant decrease in osmotic swelling. During the swelling tests the pH value in the pore fluids of both, accumulated Calcigel- and MX 80-samples decreased from 7,4 to 4,8. This change in environmental conditions accounts for the decrease in the sensitive process of osmotic swelling. [ABSTRACT FROM AUTHOR]

The study of heat transfer, water flow, and swelling pressure development in engineered clay barriers and the evaluation of the influence of these phenomena on the barrier properties are important issues for predicting the performance of nuclear waste repository facilities. In this work, an experimental setup is presented especially meant to assess the response of the sand-bentonite mixture under conditions close to that of the buffer in a radioactive waste repository. A newly developed column device for laboratory testing of coupled thermo-hydro-mechanical (THM) behaviour of clay-buffer materials is introduced and its calibration, verification and the first experimental data are presented and discussed. The main features of the column device are: hydraulic and thermal gradients are possible to be applied; water content, suction and temperature development can be measured continuously at three locations along the sample height; swelling stress can be measured at top and the bottom of the sample. Measuring transient temperature, water content and suction simultaneously at the same height levels and with special care to minimise the sample disturbance is one of the advantages of the column device proposed here when compared to that previously reported in the literature. The main objectives of this paper are: (1) to describe the experimental device, (2) to introduce the sensors implemented and their calibration, and (3) to present and discuss the first experimental results obtained with the new equipment. The first experimental results show promise in the ability of the newly developed column device to provide reliable data for assessing the THM behaviour of expansive materials that are foreseen as buffer material in high level waste repositories. [ABSTRACT FROM AUTHOR]

Abstract: An approach to estimate the swelling pressure of compacted bentonite (Bent) using Gouy–Chapman diffuse double layer theory is presented. Several laboratory swelling pressure tests on compacted Bent (MX80 and Calcigel) under constant volume conditions were performed and compared with the calculated swelling pressure using the original theory. The study revealed that at low dry density the as prepared total void ratios are less than theoretical void ratios using diffuse double layer theory, however, reverse behavior has been noticed for high compaction dry densities. Based on the experimental results of Bent with different valences, the relationship between the theoretical void ratio from diffuse double layer theory and as prepared total void ratio were determined. New equations were derived on the basis of diffuse double layer theory and experimental swelling pressure data. The method categorizes the different Bents into two groups depending upon the weighted average valency. A good agreement was observed in all the cases between experimental and estimated swelling pressure using derived equations. The applicability of the proposed method was investigated by comparing the estimated swelling pressure results with the additional reported in literature laboratory results on swelling pressure of compacted Bent. [Copyright &y& Elsevier]

To better understand the biology of extinct animals, experimentation with extant animals and innovative numerical approaches have grown in recent years. This research project uses principles of soil mechanics and a neoichnological field experiment with an African elephant to derive a novel concept for calculating the mass (i.e., the weight) of an animal from its footprints. We used the elephant's footprint geometry (i.e., vertical displacements, diameter) in combination with soil mechanical analyses (i.e., soil classification, soil parameter determination in the laboratory, Finite Element Analysis (FEA) and gait analysis) for the back analysis of the elephant's weight from a single footprint. In doing so we validated the first component of a methodology for calculating the weight of extinct dinosaurs. The field experiment was conducted under known boundary conditions at the Zoological Gardens Wuppertal with a female African elephant. The weight of the elephant was measured and the walking area was prepared with sediment in advance. Then the elephant was walked across the test area, leaving a trackway behind. Footprint geometry was obtained by laser scanning. To estimate the dynamic component involved in footprint formation, the velocity the foot reaches when touching the subsoil was determined by the Digital Image Correlation (DIC) technique. Soil parameters were identified by performing experiments on the soil in the laboratory. FEA was then used for the backcalculation of the elephant's weight. With this study, we demonstrate the adaptability of using footprint geometry in combination with theoretical considerations of loading of the subsoil during a walk and soil mechanical methods for prediction of trackmakers weight. [ABSTRACT FROM AUTHOR]

Compacted soils have been widely used as landfill barriers because of favorable characteristics such as low coefficient of permeability and high swelling. Compacted bentonite–sand mixtures are normally unsaturated and therefore suction can be used as a behavioral indicator in addition to generally used factors such as water content and dry density (or void ratio). This study focused on investigating suction characteristics of bentonite–sand mixtures. Suction was measured using various techniques for compacted bentonite–sand mixtures. The laboratory results were analyzed to provide an understanding of the suction concept in expansive soils. It was found that suction depends primarily on the water content and the bentonite content of the mixture, and suction in expansive soils changes with the time of hydration. Les sols compactés sont utilisés fréquemment comme barrière pour des dépotoirs en raison de leurs caractéristiques favorables, comme leur faible coefficient de perméabilité et de leur capacité de gonflement élevé. Les mélanges bentonite–sable sont normalement non saturés, et ainsi la succion peut servir d’indicateur du comportement, en plus des facteurs usuels comme la teneur en eau et la densité sèche (ou indice des vides). Cette étude vise à investiguer les caractéristiques de succion des mélanges bentonite–sable, à partir de mesures de succion faites avec différentes techniques. Les résultats de laboratoire ont été analysés dans le but de fournir une meilleure compréhension du concept de succion dans les sols expansifs. Il a été déterminé que la succion dépend principalement de la teneur en eau et du contenu en bentonite du mélange. L’étude a aussi permis de déterminer que la succion dans les sols expansifs varie selon le temps d’hydratation. [ABSTRACT FROM AUTHOR]

In this study, a method is proposed on the basis of the diffuse double layer theory to determine the compressibility of clays for one-dimensional conditions for vertical pressures far greater than the testing range of conventional oeodometer tests. Experimental e–p curves of several reported bentonitic clays were considered to verify the proposed method. It is shown that the parameters required to use the diffuse double layer theory can be obtained from the experimental e–p data for a low range of pressure and those can in turn be used to compute void ratios at higher vertical pressures. The stepwise procedure to calculate the e–p relationships at high pressure is given. The results showed that the agreement between the calculated and experimental compression characteristics at large vertical pressures is very good for the clays considered in this study. [ABSTRACT FROM AUTHOR]

The goal of this paper is to find the influence of fines content, f c , on the fitting parameters of Hardin's relationship to predict shear modulus and damping ratio at small and intermediate shear strain ( G(γ) and η(γ) ). Therefore, a series of resonant column tests were conducted on dry Hostun sand mixed with 0, 5, 10, 20, 30 and 40 % of fines content. Tests were carried out using the resonant column device at Ruhr- Universität Bochum. Experimental data on the adopted material revealed that maximum shear modulus decreases with an increase in f c . Analysis of data showed that fitting parameters of Hardin's relationship must be correlated to f c . In addition, experimental results for an intermediate strain region revealed the significant effect of f c on damping ratio and shear modulus. The results showed that damping ratio increased with fines content up to f c = 20 % and then decreases with further increase of f c . Reference shear strain is a key parameter to describe nonlinear behavior of soils and damping ratio. The analyses of results showed that the reference shear strain decreased with f c up to f c = 20 % and it then increases with further increase of f c for the adopted mixtures. [ABSTRACT FROM AUTHOR]

The article presents the authors' comments about the article "Parameters Affecting Soil-Water Characteristic Curves of Fine-Grained Soils," by Vikas K.S. Thakur, S. Sreedeep and Devendra N. Singh, published in the April 2005 issue of the journal. According to the authors, the findings presented in the article show that soil moisture suction in fine-grained soils such as clay soils is primarily governed by the physicochemical interactions between water and clay.

Comprehensive analytical solutions to 3-D axisymmetric problems for static response of multilayered thermoelastic media subjected to surface loads and containing sources are presented in this study. The solution strategy employs Laplace and Hankel transforms to the field variables. The problem is formulated in cylindrical coordinate system and in this coordinate system vector surface harmonics and generalized propagator matrix are introduced to find the solution for the problem for the behaviour of thermoelastic multilayered media subject to surface loads and containing heat sources. A high-order adaptive Gaussian quadrature method with continued fraction expansions is employed to approximate the integral solutions expressed in terms of semi-infinite Hankel-type integrals. It is the first time to apply the proposed solution method to investigate the behaviour of repository for heat-emitting high-level nuclear waste (HLW) in a geological formation where the HLW can be regarded as a decaying with time point heat source. [ABSTRACT FROM AUTHOR]

A response by Snehasis Tripathy and Tom Schanz to a letter to the editor about the article "Compressibility behaviour of clays at large pressures" that was published in the previous issue is presented.

Die Berechnung von Grenzzuständen in Böden und Fels im Hinblick auf die Tragfähigkeitsbestimmung und Standsicherheitsanalysen ist eine klassische Aufgabe des Grundbaus. Eine leistungs‐ und anpassungsfähige Methode zur Lösung solcher Probleme ist die Kinematische‐Element‐Methode (KEM), welche vom ersten Verfasser vor etwa 30 Jahren vorgestellt wurde. Diese wurde seitdem kontinuierlich weiterentwickelt und auf ein immer breiteres Aufgabenfeld angewendet. Nach einer kurzen Einführung in die Grundlagen der KEM wird in diesem Beitrag deren Anwendung auf komplexe Fragestellungen anhand von Beispielen vorgestellt und diskutiert. Behandelt werden die Bestimmung von Grundbruchlasten bei tief liegender Fundamentsohle und benachbarten Fundamenten, das Trapdoor‐Problem und die Berechnung der Tragfähigkeit von Plattenankern. Die Möglichkeit der Optimierung einer Böschungsgeometrie wird aufgezeigt sowie ein Konzept zur Berücksichtigung teilgesättigter Bodenverhältnisse und räumlicher Einflüsse beschrieben. The method of kinematical elements in geotechnics – new developments and applications. The prediction of limit states in soils and rocks is a classical task in foundation engineering. An efficient and adaptable tool to solve such problems is the kinematical element method (KEM), which has been presented by the first author nearly 30 years ago. This method has been improved continuously and has been applied to a more and more broad field of problems. Following a short introduction to the basic principles of the method a number of applications of KEM to complex topics is presented and discussed. Bearing capacity of deep footings and of two adjacent interfering footings, the trap door problem and the ultimate load of plate anchors are studied. The potential of optimizing the geometry of a slope is demonstrated and approaches to take into account unsaturated soil conditions as well as three dimensional effects are shown. [ABSTRACT FROM AUTHOR]

The finite element method (FEM) has become a standard tool for solving complex problems in geotechnical engineering. Many different advanced constitutive models for fine-grained soils have been developed in recent years, which can consider various phenomena of soil. Generally, the number of constitutive parameters increases with phenomena incorporated in the model, and their determination is one of the key issues in numerical modeling in geotechnics. Normally, experimental data, experience, and back analyses based on engineering judgment are used to arrive at appropriate input parameters for a particular model. However, this procedure is not always satisfactory, especially when the number of required input parameters is large. In this paper, a population-based algorithm has been used to determine the constitutive parameters for a geotechnical boundary value problem, namely a floating stone column foundation under an embankment. Measurements of surface settlements and excess pore-water pressures at different depths are available for calibration. A subsequent statistical assessment of the calibration results is followed to assess the quality of the identified parameters in dependency of the different set of measurements evaluated. As a major result of this research, measures of the utility and reliability of the constitutive models for further predictive computations can be estimated. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the swelling pressures and one-dimensional compressibility behaviour of several compacted saturated bentonite specimens were determined. Laboratory oedometer tests were carried out on a bentonite from Germany, using distilled water as the bulk fluid. A newly developed high pressure oedometer device was used that enabled measurement of swelling pressures of initially unsaturated compacted bentonite specimens (strain-controlled tests) and then facilitated subsequent loading the specimens up to 25MPa. Several initial compaction conditions (i.e., dry density and water content) of the bentonite were considered. The test results showed that both initial water content and compaction dry density influenced the swelling pressure of the bentonite. For the range of void ratio considered in this study, the swelling pressures of compacted saturated specimens were found to be significantly smaller than the applied vertical pressures during the consolidation tests. Also, the compression paths of compacted saturated specimens remained distinctly below that of the compression path for the initially saturated bentonite specimen even at very large pressures. The initial compaction conditions affected the compression index of the bentonite, whereas the effects were found to be less significant on the decompression index. The effect of initial compaction conditions on the coefficient of consolidation was found to be significant at void ratios greater than 0.5. The variation of the coefficient of permeability with the void ratio was found to be distinctly bilinear for an initially saturated bentonite specimen, whereas the permeability varied linearly with the void ratio for compacted saturated specimens. In general, the compacted saturated bentonite specimens were found to be more permeable than the initially saturated bentonite. [Copyright &y& Elsevier]

The swelling pressures of several compacted bentonites (MX80, Febex, and Montigel) proposed for use as barrier materials in storing high-level radioactive waste in many countries were determined from the Gouy–Chapman diffuse double layer theory. The swelling pressures thus determined were compared with the reported experimental swelling pressures. The study revealed that, in general, at low compaction dry densities of the bentonites, the experimental swelling pressures are less than their theoretical counterparts, with the reverse trend at high compaction dry densities. Based on the reported experimental results for the three bentonites, relationships between the nondimensional midplane potential function, u, and the nondimensional distance function, Kd, were established. New equations for the swelling pressure were proposed on the basis of the diffuse double layer theory and the reported experimental data to compute swelling pressures of compacted bentonites. The suitability of the new equations was also verified with additionally reported experimental swelling pressures from three other bentonites (Kunigel V1, Kunigel, and bentonite S-2) that have been also proposed for use as barrier materials. Very good agreement was found in all the cases between the experimental swelling pressures and the swelling pressures obtained using the proposed equations. The use of the proposed equations is based on the weighted average valency of the cations present in bentonites, since the valency of the cations present has a significant influence on the swelling pressure. [ABSTRACT FROM AUTHOR]

Abstract In deep geological repositories, compacted bentonites have been proposed for use as barrier materials for isolating nuclear waste. The prevailing hydro-mechanical-chemical boundary conditions in the repositories can affect the swelling capacity of compacted bentonites. The present study examines the linkage between the swelling pressure of saturated bentonites, the total suction of saturated bentonites and the suction of hydrating fluids. An equation describing the linkage between these parameters was derived based on the thermodynamics of soil moisture. To validate the derived relationship, laboratory tests involving constant volume swelling pressure tests and total suction measurements after the swelling pressure tests were carried out on a selected Ca-Mg-rich bentonite. Seven bentonite samples with compaction dry density ranging from 1.20 to 1.83 Mg/m3 were hydrated with deionized water, whereas four samples with a dry density of 1.59 Mg/m3 were hydrated with 0.0001 to 2.0 M CaCl 2 solutions. The total suctions of the saturated bentonite and the hydrating fluids were determined by using a chilled-mirror hygrometer. The total suction of the saturated bentonite was found to be affected by the compaction dry density and the suction of the hydrating fluids. The experimental results from the present study and from the literature demonstrated that the total suction of saturated bentonites minus the suction of the hydrating fluids used to saturate bentonites is approximately equal to the swelling pressure of saturated bentonites. Highlights • Time for swelling pressure to reach equilibrium increases with bentonite density. • Bentonite density and concentration of solutions affect the suction of bentonites. • Swelling pressure equals the difference in suction between bentonite and solutions. [ABSTRACT FROM AUTHOR]

Summary: This study investigates the ground movements due to mechanized tunnel excavation by applying two‐dimensional finite element analyses. To assess the contribution of the compressibility and plasticity of the soil on the ground movements, different constitutive models are employed to describe the soil behavior. The influence of volume loss around the tunnel on the surface volume loss is investigated, and a quadratic correlation between them is proposed. Consequently, the empirical Gaussian distribution curve, which is generally used to determine the tunneling induced settlement trough, is improved by applying the proposed quadratic correlation between surface volume loss and tunnel volume loss. Furthermore, the settlement trough width parameter has been derived by a linear function of tunnel volume loss as well. The proposed equations are validated via a case study of centrifuge tests from the literature. The results show that the proposed modification enhances the empirical solution by having better knowledge on the model parameters. Additionally, tunnel overburden and coefficient of lateral earth pressure at rest (K0) are taken into account to study their influence on the tunneling induced surface settlements. Finally, global sensitivity analysis is applied to evaluate the relative importance of corresponding model parameters in terms of their influence on the ground movements. [ABSTRACT FROM AUTHOR]

Abstract This paper introduces a new approach to investigate the tunnel face stability. In the proposed approach a 3D KEM (Kinematical Element Method) model is developed which consists of two rigid blocks, tetrahedron wedge block (lower part) and triangular prism block (upper part). In order to incorporate the influence of the 3D soil arching in silo for predicting the minimum support pressure, it is presumed a 3D active earth pressure acting on the vertical prism's slip surfaces from the adjoining soil. The results given by the KEM model are compared with the results of numerical simulations, analytical approaches, and physical model tests available in literature. Similar to Terzaghi's superposition method commonly used in bearing capacity analysis, the minimum support pressure is expressed by summation of cohesion (c), surcharge load (q) and unit weight of the soil (γ) multiplied by non-dimensional bearing capacity coefficients N c , N q and N γ . Simple formulas have been developed to compute the non-dimensional coefficients. The N γ , N c , and N q formulas are presented as function of internal friction angle (φ), and cover depth to tunnel diameter ratio (C/D). The proposed KEM model for the tunnel face stability gives good results in term of minimum support pressure compared to physical model test results, various analytical and numerical solutions for the tunnel face stability analysis of shallow tunnels. [ABSTRACT FROM AUTHOR]

In deep geological repositories, compacted bentonites have been proposed for use as barrier materials for isolating nuclear waste. The prevailing thermo-hydro-mechanical boundary conditions in the repositories may affect the swelling capacity and permeability of the compacted bentonites. In this study, the effect of preliminary desiccation on the subsequent hydro-mechanical behaviour (swelling pressure and hydraulic conductivity) of compacted Calcigel bentonite was investigated experimentally at 22°C and 80°C. In the first stage of the test, the compacted specimens were subjected to suction-controlled desiccation at 22°C and 80°C using the vapour-equilibrium technique. After the water content reached equilibrium at a given suction, the axial, radial and volumetric shrinkage strains were measured. Afterwards, constant-volume swelling-pressure tests were performed on the desiccated specimens (second test stage) by saturating the dried specimens with deionized water at 22°C and 80°C. At the end of the swelling-pressure test, the hydraulic conductivities of four saturated specimens were measured at each temperature. The volumetric shrinkage strain of the compacted bentonite during desiccation is controlled by suction instead of temperature. In addition, the preliminary desiccation increases both the swelling pressure and hydraulic conductivity of compacted bentonite, particularly if compacted bentonite undergoes extreme desiccation at an applied suction of >700 MPa. [ABSTRACT FROM AUTHOR]

This paper numerically investigates the slurry shield tunneling in fully saturated soils with different hydraulic conductivities in short- and long-term scales. A fully coupled hydromechanical three-dimensional model that accounts for the main aspects of tunnel construction and the hydromechanical interactions due to tunneling process is developed. An elasto-plastic constitutive model obeying a double hardening rule, namely hardening soil model, is employed in the numerical simulations. The research mainly focuses on assessing the influence of soil hydraulic conductivity and the method to simulate backfill grouting in the tail void on the evolution of ground subsidence, excess pore water pressure and lining forces. Two different consolidation schemes have been taken into account to computationally address the tunnel construction in soil with low and high hydraulic conductivities. In addition, different methods are employed to simulate the tail void grouting as a hydromechanical boundary condition and to study its effects on the model responses. Finally, the influences of infiltration of the fluidized particles of grouting suspension into the surrounding soil and its corresponding time-space hydraulic conductivity evolution on the displacements and lining forces are studied. [ABSTRACT FROM AUTHOR]

This study adopts the local and global sensitivity analyses to study the influence of the soil-tunnel-building system characters (e.g. soil properties, building’s stiffness and position, tunnel volume-loss and embedment depth, soil-building interface properties) on the settlement and tilt of building. To properly update the design parameters during tunnel construction, a field sensitivity analysis is proposed to find the optimal position of the sensors in a priori to increase the quality of measurements (less uncertainty) which leads to efficient identification of the soil parameters from the measurements. The validity of this methodology is justified by applying it to a case study. [ABSTRACT FROM AUTHOR]

A model prediction using FE modeling is performed for a trial embankment on soft clay in Ballina, Australia. The comparison between the prediction and the in situ measurement exhibits significant differences. A detailed analysis is performed to validate the model and determine necessary improvements. Sensitivity analyses elaborate upon the most dominant constitutive parameters. Based on site measurements, inverse analyses are performed to identify the optimum parameters. The inverse analysis approach is validated regarding its dependency on the objective function and data incorporated. A comparison between the prediction and the back-calculated parameters confirms the importance of engineering judgment as well as the sensitivity of the modeling strategies to the input information. [ABSTRACT FROM AUTHOR]

Studies on the dehydration of montmorillonites imply that the standard oven-drying method (drying at 110 ± 5°C) may underestimate the water content of bentonites. This study quantifies, identifies, explains, and removes the residual water in a calcium-rich bentonite dried using the standard oven-drying method. A thermogravimetric-differential scanning calorimetry (TG-DSC) test was performed to determine the true water content. According to this test, the effect of the drying time and temperature on the amount of residual water in the bentonite was examined, including the oven-drying and vacuum-drying methods. To identify and explain the residual water, specific surface area (SSA) derived from the nitrogen adsorption isotherm and dehydration reaction characterised by TG-DSC curves of samples with a residual water content of 0–13.38% were obtained. The experimental results demonstrate that the standard oven-drying method underestimates the water content of calcium-rich bentonites by 2.1–3.1%. The 2.1–3.1% of residual water includes both interlayer water and adsorbed water on the external surface. The 2.1–3.1% of residual water is the water forming the inner shell around Ca 2+ cations in the interlayer and on the external surface of montmorillonite particles. It is impractical to distinguish between the adsorbed water and interlayer water only based on the dehydration reaction characterised by TG-DSC curves. Drying profiles of 12 h of drying at 200°C in an oven and 1 h of drying at 150–200°C under vacuum are sufficient for removing the adsorbed and interlayer waters from the bentonite. [ABSTRACT FROM AUTHOR]

Comparative investigations on spatial passive earth pressure by the kinematic element method The determination of earth pressures belongs to the fundamental tasks in geotechnical engineering and is generally treated as a load capacity problem. Using the Kinematic Element Method (KEM), which is an appropriate method for the prediction of limit states, the spatial passive earth pressure is examined. From the results the earth pressure coefficients are determined for variable friction angles, wall friction angles as well as wall geometries. These coefficients are presented in tables and diagrams. Comparing the KEM results to other kinematic approaches as well as the German standard, it turns out that good estimation of the spatial passive earth pressure is possible already with simple mechanisms. Further refinement may additionally improve the quality of the results. [ABSTRACT FROM AUTHOR]

The swelling prediction of bentonite–sand mixtures due to wetting is very important in evaluating the long term performance of the engineered barrier in the high level radioactive waste disposal system and the hydraulic barriers in geoenvironmental constructions. Sun et al. (2015) proposed the swelling prediction model of bentonite-sand mixtures due to full hydration, and predicted the swelling of different types of bentonite-sand mixtures, which was verified, to be consistent with the swelling test results. However, the predicted swelling results of bentonite-sand mixtures with extremely high sand content obtained by the original swelling prediction model have a large deviation from the test results. The reason is that the original model is based on an assumption that all the pores and available water are only associated with bentonite/montmorillonite fraction. However, for mixtures with extremely high sand content, the sand skeleton exists and resists the external stress from the very beginning. At the same time, the bentonite, dispersing in the sand skeleton, in contact with the pore fluid, swells freely to fully saturated state, however, still fails to fill the sand skeleton voids completely. In this research, the original swelling prediction model is extended by introducing the concept of critical filling sand content and critical contact stress. When sand content is more than the critical filling sand content, the deformation of the mixture is mainly due to the sand skeleton deformation. After the stress increases greater than the critical contact stress, the saturated bentonite fills the sand skeleton voids completely, and the swelling can still be predicted by the original swelling prediction model. In the extended model, the swelling prediction can be divided into three zones according to the two limit values of critical sand content and critical filling sand content. In different zones, the distribution ratio of the vertical stress that is borne by montmorillonite and sand skeleton is different. The extended swelling prediction model is applicable to predict the swelling due to full hydration for mixtures within the full range of sand content, and is verified by the swelling tests on bentonite–sand mixtures with various sand contents. [ABSTRACT FROM AUTHOR]

This paper focuses on the sensitivity analysis for coupled thermo-hydro-mechanical problems employing both local and global sensitivity methods. A derivative-based method is used in the local sensitivity approach, whereas the random balance designs method is used for the global sensitivity analysis. The main goal is to investigate the effect of uncertainties in the constitutive parameters on the results from nonlinear coupled thermo-hydro-mechanical analyses of unsaturated soil behavior whose modeling generally involves large sets of constitutive relations. Knowing the parameter sensitivity allows to qualitatively assess the validity of the results obtained by computational simulations of high-risk situations, for example, emerging nuclear waste repositories. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Structural design of linings requires a reliable prognosis of lining forces and deformations. In engineering practice, both analytical and numerical solutions are popular to be employed to predict the system behavior. This paper employs the commonly accepted analytical solutions to calculate the lining forces and deformations for both shallow and deep tunnels, the results are compared to the numerical results for corresponding equivalent boundary conditions, initial conditions and identical material properties. Afterward, more sophisticated constitutive models for soil/structure elements in conjunction with more realistic construction aspects are taken into account. The comparison of the results of analytical and numerical solutions highlights the differences between these two well accepted methods as well as the effect of considering realistic features in numerical simulations. Moreover, the lining forces and deformations obtained from plain strain condition are compared to the 3D numerical results. The results show that the analytical bedding model is able to reasonably predict the lining behavior for both shallow and deep tunnels even if the soil is assumed to be an elastic material. In numerical solutions, lining forces and deformations depend to a large extent on the applied soil constitutive model and construction method. The face support pressure, backfill grouting and arching effect cannot be captured appropriately in plain strain condition, which leads to the discrepancy between the model responses obtained from 2D numerical/analytical solutions and realistic 3D simulations. [ABSTRACT FROM AUTHOR]

This study focuses on the failure probability of storing renewable energy in the form of hydrogen or compressed air in rock salt caverns. The validation of the short- and long-term integrity and stability of rock salt cavern is a prerequisite in their design process. The present paper provides a reliability-based analysis of a typical renewable energy storage cavern in rock salt. An elasto-viscoplastic creep constitutive model is implemented into a numerical model of rock salt cavern to assess its behavior under different operation conditions. Sensitivity measures of different variables involved in the mechanical response of cavern are computed by elementary effect global sensitivity method. Subset simulation methodology is conducted to measure the failure probability of the system with a low computational cost. This methodology is further validated by a comparison with a Monte Carlo-based probabilistic analysis. The propagation of parameter uncertainties and the failure probability against different failure criteria are evaluated by utilizing a Monte Carlo-based analysis. In this stage, the original finite element model is substituted by a surrogate model to further reduce the computational effort. Finally, a reliability analysis approach is employed to obtain the minimum admissible internal pressure in a cavern. [ABSTRACT FROM AUTHOR]

Presented in this paper is a rigorous solution of the conventional Terzaghi one-dimensional consolidation under haversine cyclic loading with any rest period. The clay deposit is either permeable at both top and bottom or permeable at the top and impermeable at the bottom. This exact analytical solution was achieved using Fourier harmonic analysis for the periodic function representing the rate of imposition of excess pore water pressure. The double Fourier series in the rigorous solution was found to be rapidly convergent. The analysis of excess pore water pressure and effective stress is done in the Matlab 2010 environment. Both the effects of rest period and frequency of cyclic loading are investigated. The analysis reveals that the excess pore water pressure arrives the steady-state at a time factor T of about 2. Furthermore, finite element method (FEM) is applied to solve numerically the corresponding consolidation problem and the FEM solution is compared to the analytical solution showing a good match. [ABSTRACT FROM AUTHOR]

On the load bearing behavior of the self-regulating interactive membrane foundation system The paper reports on a new foundation system, the self-regulating membrane foundation, for embankments on deep soft soil deposits, such as stockpiles or infrastructure embankments. The load bearing behavior of the system was analyzed by means of centrifuge model tests and comprehensive numerical simulations, such as global sensitivity analyses and parametric studies. The results of those analyses and the derived design approach are presented in the paper. The paper concludes with a validation of the design approach, by comparison with results of the numerical simulation. [ABSTRACT FROM AUTHOR]

Zur Schnittgrößenermittlung, Verformungsberechnung, Spannungsanalyse und zur Bemessung von maschinell aufgefahrenen Tunneln mit Tübbingauskleidung werden heutzutage verschiedene Modellierungsmethoden herangezogen. Zum Entwurf und zur Bemessung des Tunnelausbaus dienen üblicherweise Bettungsmodelle, die den umliegenden Boden mit nur Druckkraft übertragenden Federn idealisieren und den Ausbau als kreisförmige Balkenabschnitte abbilden. Um eine dreidimensionale Wirkung des Tunnels im Baugrund aufzuzeigen, werden numerische Kontinuumsmodelle genutzt. Die Baugrundeigenschaften werden dabei zumeist unter Verwendung eines nichtlinearen Materialgesetzes abgebildet, wobei der Tunnelausbau vorwiegend als kreisförmige Schalenabschnitte mit Druck‐ und Reibkontakt zum Baugrund erfasst ist. Dabei können einerseits relevante Bauzustände wie der sequenzielle Tunnelvortrieb, die schrittweise Installation des Tunnelausbaus im umliegenden Boden sowie ausgewählte Belastungsszenarien aus dem Verpressdruck und dem Stützdruck abgebildet werden. Andererseits lassen sich durch Simulationsmodelle mit sofortiger Aktivierung des Tunnelausbaus Endzustände realisieren. Neben diesen nichtlinearen numerischen Berechnungsmethoden liefern klassische analytische Lösungen z. B. im elastischen Halbraum wichtige Grundlagen (Last‐ und Modellierungsansätze) und Kontrollmöglichkeiten (Größe von Schnittgrößen und Verformungen). Der Beitrag stellt demnach Unterschiede zwischen den einzelnen Modellierungsvarianten gegenüber, bewertet sie im Hinblick auf die Abbildungseigenschaften und vergleicht sie hinsichtlich der Schnittgrößenkombinationen und radialen Verschiebungen unter Variation ausgewählter Parameter des Baugrunds. Comparative Analyses of Modeling Alternatives of Tunnels with Concrete Lining Segments Task‐oriented alternative modelling techniques are popular in mechanised tunnelling to calculate internal forces and deformations, to analyse stresses or to design. For detailing and designing lining segments beams on elastic foundation are often favoured. Those models idealise the soil‐structure interaction employing compression‐only springs and approximate the circular tunnel shell by polygonal beam members. By contrast and to account for a holistic three‐dimensional impact of the tunnel on the soil more sophisticated continuum models, utilising nonlinear constitutive laws, are preferred. Here, the circular tunnel shell interacts in compression with the surrounding soil by contact and friction. Apart from the final state scenario associated with an immediately activated tunnel lining, intermediate construction stages due to sequential driving along with a stepwise consecutive installation of lining segments and specific loading scenarios from grouting or back pressure can explicitly be accounted for. Complementary to nonlinear numerical simulation well‐known analytical results provide a sound fundamental basis for control. The contribution contrasts and assesses alternative modelling approaches regarding features, demands and adequacy. For the last one, numerical results are analysed in variation of decisive soil properties with respect to radial deformations in relevant load combinations. [ABSTRACT FROM AUTHOR]

Solution-mined caverns excavated in rock salt formations are recognized as the appropriate places for underground storage of energy in the form of compressed air and hydrogen. These caverns are subjected to different loading conditions during the construction and operation time. Therefore, it is essential to investigate the mechanical response of rock salt for all life stages of the cavern such as leaching phase, debrining process, first filling as well as cyclic loading operation. To achieve this goal, proper constitutive laws are required to describe the material behavior of rock salt at different time scales. In this paper, an elasto-viscoplastic-creep model is employed to predict the stress-strain relation around the cavern during the construction and cyclic operation phases. The proposed creep law is a modified version of Norton creep law which accounts for the time-dependent volumetric deformation. Additionally, a damage parameter which is dependent on the released inelastic work is included in the model to predict the material failure. To accomplish this, first, the material parameters of the employed model are determined using the relevant experimental data available in the literature. Then, the excavation process and cyclic loading operation of a typical salt cavern are numerically simulated. The stress paths around the cavern as well as the volume convergence, damage propagation and permeability changes are evaluated considering two loading scenarios, and finally, the allowable operating conditions for the simulated cavern are identified. [ABSTRACT FROM AUTHOR]

Coupled thermo-hydro-mechanical (THM) analyses contain a large set of constitutive parameters and this requires numerous experiments to determine these parameters. This study contributes to the identification of parameters of a coupled THM constitutive model via back analysis of information-rich experiments. An iterative sampling based back analysis approach is proposed comprising both the model parameter identification and the assessment of the reliability of identified model parameters. The results obtained in the context of buffer elements indicate that sensitive parameter estimates generally follow the normal distribution. According to the sensitivity of the parameters and the probability distribution of the samples we can provide confidence intervals for the estimated parameters and thus allow a qualitative estimation on the identified parameters which are in future work used as inputs for computational predictions in high-risk situations. [ABSTRACT FROM AUTHOR]

In this research, Finite Element (FE) method is applied to simulate the shield supported mechanized excavation of Western Scheldt tunnel in the Netherlands. Both 2D and 3D numerical models are created to predict the system behavior. Sensitivity analysis and parameter identification techniques are utilized to calibrate and validate the model based on field measurement. The mechanical behavior of the soil is modeled by an advanced elasto-plastic model, namely Hardening Soil model correlating small strain stiffness (HSS). Global sensitivity analysis is carried out in this paper to evaluate the relative sensitivity of model response to each input parameter. Thereafter, a parameter identification technique (back analysis) is employed to find the optimized values of the selected parameters. To accomplish this, the computationally expensive FE-model is replaced by a meta-model in order to reduce the calculation time and effort. Moreover, a soft soil constitutive model based on the modified Cam-clay model deals with primary compression of fine grained soils, is assigned to the clay layer to further improve the numerical prediction of system behavior. Due to the importance of model subsystems, such as face pressure and volume loss, the sensitivity of model response to subsystems has been evaluated. The results show that optimized parameters obtained via back analysis make the numerical simulation capable to well predict the ground settlement. [ABSTRACT FROM AUTHOR]

This paper is an extension of previous work which characterises soil behaviours using the grading entropy diagram. The present work looks at the piping process in granular soils, by considering some new data from flood-protection dikes. The piping process is divided into three parts here: particle movement at the micro scale to segregate free water; sand boil development (which is the initiation of the pipe), and pipe growth. In the first part of the process, which occurs during the rising flood, the increase in shear stress along the dike base may cause segregation of water into micro pipes if the subsoil in the dike base is relatively loose. This occurs at the maximum dike base shear stress level (ratio of shear stress and strength) zone which is close to the toe. In the second part of the process, the shear strain increment causes a sudden, asymmetric slide and cracking of the dike leading to the localized excess pore pressure, liquefaction and the formation of a sand boil. In the third part of the process, the soil erosion initiated through the sand boil continues, and the pipe grows. The piping in the Hungarian dikes often occurs in a twolayer system; where the base layer is coarser with higher permeability and the cover layer is finer with lower permeability. The new data presented here show that the soils ejected from the sand boils are generally silty sands and sands, which are prone to both erosion (on the basis of the entropy criterion) and liquefaction. They originate from the cover layer which is basically identical to the soil used in the Dutch backward erosion experiments [ABSTRACT FROM AUTHOR]

Die Beurteilung der Grundbruchsicherheit flach gegründeter Fundamente ist ein zentrales Thema auf dem Gebiet der Bodenmechanik und des Grundbaus. In Deutschland ist die Nachweisführung in [1] für ausgewählte Randbedingungen geregelt. Die Grundbruchgleichung basiert auf dem Superpositionsansatz nach Terzaghi. In diesem Beitrag wird der signifikante Einfluss der Sohlreibung auf den Bruchmechanismus und die Tragfähigkeit eines einzelnen Streifenfundaments diskutiert. Für eine raue Sohlausbildung wird der bekannte Berechnungsansatz für den Grundbruchwiderstand für den Fall zweier benachbarter und wechselwirkender Streifenfundamente erweitert. Mit Hilfe der Kinematischen Elemente Methode (KEM) nach [2] und [3] werden zunächst ein geeigneter Bruchmechanismus entwickelt und anschließend für unterschiedliche Abstände S zwischen den beiden Fundamenten und verschiedene Reibungswinkel ϕ die Traglasten der Fundamente berechnet. Durch Einführung eines Wechselwirkungsfaktors η, der die Traglast benachbarter Fundamente mit der eines frei stehenden Fundaments in Relation setzt, wird die Steigerung der Traglast beschrieben. Ein Vergleich mit anderen theoretischen sowie experimentellen Untersuchungen zeigt eine gute Übereinstimmung mit den mit der KEM berechneten Ergebnissen bei vergleichbaren Annahmen der Bruchmechanismen sowie der Sohlreibungsverhältnisse. On the bearing capacity of single and interfering strip footings - Analysis of the influence of footing-base-friction and interference factors by the KEM. The assessment of bearing capacity of shallow footings is one of the main topics in soil mechanics as well as in foundation engineering. In Germany the safety analysis is regulated in [1]. Chosen boundary conditions are considered. The so called ground failure equation is based on the superposition principle after Terzaghi. In the present article the significant influence of base-friction on the bearing capacity of shallow strip footings will be discussed. The general approach of the bearing capacity analysis will be extended to the boundary condition of two adjacent interfering rough footings. By using the Kinematical Element Method (KEM), originally developed in [2] and [3], an appropriate failure mechanism will be developed and bearing capacity calculations are carried out for varying distances S between the footings. Also different friction angles ϕ of the soil will be considered in this parameter study. By defining an efficiency factor η, as the ratio of an interfering footing and one that is isolated, the change in bearing capacity can be evaluated. A comparison with available theoretical and experimental data confirms the present KEM-results. [ABSTRACT FROM AUTHOR]

The hydraulic conductivity plays a major role on the excess pore pressure generation during monotonic and cyclic loading of granular soils with fines. This paper aims to determine how much the hydraulic conductivity and pore pressure response of the sand-silt mixtures are affected by the percentage of fines and void ratio of the soil. The results of flexible wall permeameter and undrained monotonic triaxial tests performed on samples reconstituted from Chlef River sand with 0, 10, 20, 30, 40, and 50% nonplastic silt at an effective confining stress of 100 kPa and two relative densities (Dr = 20, and 91%) are presented and discussed. It was found that the pore pressure increases linearly with the increase of the fines content and logarithmically with the increase of the intergranular void ratio. The results obtained from this study reveal that the saturated hydraulic conductivity (k) of the sand mixed with 50% low plastic fines can be, on average, four orders of magnitude smaller than that of the clean sand. The results show also that the hydraulic conductivity decreases hyperbolically with the increase of the fines content and the intergranular void ratio. [ABSTRACT FROM AUTHOR]

Der derzeitige Kenntnisstand zum Systemverhalten von mit Lockermassen versetzten Füllsäulen alter Tiefbauschächte ist durch die Untersuchungen der WBK aus den 1970er-Jahren geprägt. Die damals erzielten Ergebnisse fanden Eingang in die fachspezifischen Richtlinien der Bergbehörde und manifestierten die mit Lockermassenfüllsäulen verbundene, besondere Gefahrensituation, z.B. über die Vorgabe eines Sogansatzes bei der Bemessung von Schachtabdeckungen. Im Zuge der Aufstellung eines Risiko-Managementsystems zum Umgang mit bergbaulichen Tagesöffnungen der RAG ergab sich die Notwendigkeit einer differenzierten Neubewertung der Lagestabilität von Lockermassenfüllsäulen. Hierzu wurde u.a. die Durchführung von Zentrifugen-Modellversuchen mit Variation verschiedener Modellparameter konzipiert. In diesen Versuchen sollen insbesondere die Voraussetzungen bzw. die Auslöser für das plötzliche Auslaufen von Lockermassenfüllsäulen ermittelt werden. Im vorliegenden Beitrag werden die erzielten Ergebnisse und daraus getroffenen Ableitungen vorgestellt, aus denen eine differenzierte Sichtweise auf die Gefährlichkeit von Lockermassenfüllsäulen erkennbar ist. Investigations on stability behaviour of non-cohesive filled shafts. State-of-the-art knowledge on stability of abandoned mining shafts filled with mostly granular, low cohesive materials is based on model testing by WBK in the 1970ies. Results from this research are incorporated in specific recommendations of the mining authorities, e.g. assuming suction load on shaft covering slabs. While introducing an active risk managing procedure on abandoned shafts, RAG decided to relaunch research activities on this topic. Using a geotechnical centrifuge facility, a comprehensive test series was performed with major results presented in this paper that lead to an updated view on fill stability in abandoned mining shafts. [ABSTRACT FROM AUTHOR]

SUMMARY Presented and discussed in this paper is an exact analytical solution of the nonhomogeneous partial differential equation governing the conventional one-dimensional consolidation under haversine repeated loading. The derived analytical solution to the 1D consolidation equation is compared with the numerical solution of the same consolidation problem via FEM. The series solution takes into account the frequency of repeated loading through a dimensionless time factor T0. The paper reveals that an increase in the frequency of imposed repeated haversine loading (a decrease in period of repeated loading) causes an increase in the number of cycles required to achieve the steady state, whereas the effect of frequency on the maximum excess pore water pressure at the bottom of a clay layer with permeable top and impermeable bottom for the range of frequencies studied is generally insignificant. The effective stress at the bottom of the clay deposit with permeable top and impermeable bottom increases with time but with some fluctuations without changing the sign. These fluctuations become more pronounced for increasing values of T0. An increase in T0 also causes an increase in maximum effective stress. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper deals with the inverse problem of using time-displacement monitoring data to determine the material parameters of a numerical model of a large-scale mass movement. A finite element model for simulating the mechanical behavior is presented for the Gradenbach landslide in Carinthia, Austria. Particular attention is paid to the calibration of the constitutive relationships, which represent a prerequisite for a realistic quantitative analysis. After a short introduction to the concept of model-parameter identification, this paper demonstrates how to apply the proposed model identification strategy to determine model parameters for the Gradenbach example. The impact of the amount of reference data available for the inverse model-parameter analysis is evaluated by means of artificial reference data. Subsequently, the numerical model is calibrated using field measurement data. The results obtained are presented, and the benefits and drawbacks of the proposed concept are evaluated. [ABSTRACT FROM AUTHOR]