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 Acta Geotechnica   [SJR: 1.818]   [H-I: 22]   [7 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1861-1133 - ISSN (Online) 1861-1125    Published by Springer-Verlag  [2350 journals]
• Consistent modeling of a catastrophic flowslide at the Shenzhen landfill
using a hydro-elasto-plastic model with solid–fluid transition
• Authors: Z. H. Li; Y. J. Jiang; Q. Lv; L. R. Sousa; M. C. He
Abstract: Flow-type landslides are an important hazard that can cause great destruction due to the rapid flow velocity and large disaster area. This paper presents a catastrophic flowslide that recently occurred at a landfill in Shenzhen, China. This disaster involved an area about 1100 m in length and 630 m in maximum width, and caused the death of 77 people and the destruction of 33 buildings. The precise reason for the landfill’s failure is still unknown, and therefore we try to contribute an increased understanding of the event for future prevention. In this study, the failure mechanism of the studied slope was analyzed and described under partially saturated condition. The solid–fluid transition during the flowslide occurrence was described using a unified constitutive model. The model was used to perform the hydro-elasto-plastic modeling in the pre-failure stage, the viscous modeling in the post-failure stage, and the second-order work criterion was introduced in between to model the solid–fluid transition. The consistent evolution of the flowslide, including initiation, propagation, and deposit stages, was simulated and analyzed using the finite element method with Lagrangian integration points after careful calibration of the viscous parameters. The numerical results were compared with the real case and used to explain the failure mechanism.
PubDate: 2018-04-25
DOI: 10.1007/s11440-018-0672-3

• Effectiveness of deep cement mixing walls with top-down construction for
deep excavations in soft clay: case study and 3D simulation
• Authors: Pitthaya Jamsawang; Panich Voottipruex; Pornpot Tanseng; Pornkasem Jongpradist; Dennes T. Bergado
Abstract: This paper presents the observed and simulated effectiveness of deep cement mixing walls created using top-down (DCM-TD) construction techniques for a deep excavation in soft Bangkok clay. The wall system consisted of four rows of 0.7-m-diameter DCM columns, and the bracing system consisted of two 0.25-m-thick basement slabs and seven temporary struts. The effectiveness of the wall system compared to that of other wall systems was evaluated using the measured results of previous case studies. A 3D numerical analysis was performed to calculate forces in the basement slabs and bending moments in the DCM wall. Finally, series of parametric analyses of both DCM-TD and deep cement mixing walls created using bottom-up (DCM-BU) construction techniques were carried out, and their results were compared to highlight the effectiveness of DCM-TD and its applicability to excavations at greater depths. The field and numerical results show that DCM-TD is more effective than DCM-BU in terms of the limitations of lateral wall movement, the bending moment in a DCM wall and the thickness of a DCM wall for various depths because of a larger system stiffness. Therefore, DCM-TD is very effective and suitable for use in potential future deep excavations in urban areas.
PubDate: 2018-04-25
DOI: 10.1007/s11440-018-0660-7

• Experiments on failure process of new rock-like specimens with two
internal cracks under biaxial loading and the 3-D simulation
• Authors: Jin-Wei Fu; Shu-Li Liu; Wei-Shen Zhu; Hao Zhou; Zhen-chuan Sun
Abstract: A new resin material has been developed by massive formula exploration. The resin is thoroughly transparent and rock-like at low temperatures. Its tension–compression strength ratio is up to 1/6.6 in the temperature range of − 10 to − 15 °C. It can simulate quite a few kinds of engineering rocks. Specimens have been made with two internal cracks. The progressive failures under uniaxial and biaxial compressions are systematically studied. The uniaxial failure process is divided into four stages as conventional rock mechanics test. Several forms of secondary cracks, like anti-wing cracks in the biaxial experiment with high lateral pressure, have seldom been described by former scholars. Three-dimensional numerical simulation has been conducted using FLAC3D. A novel elastic-brittle constitutive model is developed and programed. Superfine mesh generation is demanded as well. Both uniaxial and biaxial results of the new numerical approach show excellent consistency with experimental results in this paper.
PubDate: 2018-04-18
DOI: 10.1007/s11440-018-0651-8

• A 2D coupled hydro-thermal model for the combined finite-discrete element
method
• Authors: Chengzeng Yan; Yu-Yong Jiao; Shengqi Yang
Abstract: Based on the combined finite-discrete element method (FDEM), a two-dimensional coupled hydro-thermal model is proposed. This model can simulate fluid flow and heat transfer in rock masses with arbitrary complex fracture networks. The model consists of three parts: a heat conduction model of the rock matrix, a heat-transfer model of the fluid in the fracture (including the heat conduction and convection of fluid), and a heat exchange model between the fluid and rock at the fracture surface. Three examples with analytical solutions are given to verify the correctness of the coupled model. Finally, the coupled model is applied to hydro-thermal coupling simulations of a rock mass with a fracture network. The temperature field evolution, the effect of thermal conductivity of the rock matrix thermal conductivity and the fracture aperture on the outlet temperature are studied. The coupled model presented in this paper will enable the application of FDEM to study rock rupture driven by the effect of hydro-thermo-mechanical coupling in geomaterials such as in geothermal systems, petroleum engineering, environmental engineering and nuclear waste geological storage.
PubDate: 2018-04-13
DOI: 10.1007/s11440-018-0653-6

• Discussion of “From saturated to unsaturated conditions and vice
versa” by Martí Lloret-Cabot, Simon J. Wheeler, Jubert A. Pineda,
Enrique Romero, and Daichao Sheng
(https://doi.org/10.1007/s11440-017-0577-6)
• Authors: Shunchao Qi; Paul Simms; Sai Vanapalli
Abstract: The authors (Lloret-Cabot et al. in Acta Geotech 1–23, 2017) applied the glasgow coupled model (GCM), originally proposed by Wheeler et al. (Géotechnique 53(1):41–54, 2003), to the simulation of several experimental tests that involve transition between saturated and unsaturated states. The authors show qualitatively, but not quantitatively, predictions of GCM for shrinkage during air drying of normally consolidated samples (Fig. 13) under low mechanical stress conditions, without presenting the material parameters. The discussers, who have worked with GCM to model multilayer deposition of tailings/soft soils (Qi in Numerical investigation for slope stability of expansive soils and large strain consolidation of soft soils. Doctoral dissertation, University of Ottawa, 2017; Qi et al. in J Geotech Geoenviron Eng 143(7):04017018, 2017, Qi et al. J Geotech Geoenviron Eng 143(7):04017019, 2017), have made quantitative predictions of similar cases. Satisfactory simulations of such cases using GCM are sensitive to the selection of the coupling parameters k1 and k2. By considering an alternative analytical form of GCM, an analytical procedure can be derived for calibrating the coupling parameters for problems involving virgin drying.
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0625-2

• Hydro-thermal coupled analysis for health monitoring of embankment dams
• Authors: Tewodros Y. Yosef; Chung R. Song; Ki-Tae Chang
Abstract: Measuring and analyzing internal dam temperature may provide insight into evaluating the integrity of earthen dams. Temperature in a dam, with the advent of modern distributed temperature sensing (DTS) technique, is conveniently measured. The analysis of the temperature is conducted based on a hydro-thermal coupled analysis technique. In this study, DTS-based temperature data and VS2DHI (a finite difference code for analyzing two-dimensional heat transport in porous media) were used to analyze the hydro-thermal coupled behavior in a dam. The results of this analysis show that the temperature variation in an earthen dam is closely related to seepage conditions. Additionally, a localized high-temperature (26 °C) zone found in the measured data of the dam, which raised concern to engineers on site, is explained through either hot water infiltration into the foundation layer or lower permeability of the foundation layer than the magnitude that appeared in the design document. These findings demonstrate that hydro-thermal coupled analysis has the potential for evaluating the integrity of earthen dams.
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0571-z

• Reply to “Discussion of “From saturated to unsaturated conditions and
vice versa” by M. Lloret-Cabot et al. (DOI 10.1007/s11440-017-0577-6)”
by S. Qi et al. (DOI 10.1007/s11440-017-0625-2)
• Authors: Martí Lloret-Cabot; Simon J. Wheeler; Jubert A. Pineda; Enrique Romero; Daichao Sheng
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0626-1

• Explicit meshfree solution for large deformation dynamic problems in
saturated porous media
• Authors: Pedro Navas; Lorenzo Sanavia; Susana López-Querol; Rena C. Yu
Abstract: In this paper a new methodology to simulate saturated soils subjected to dynamic loadings under large deformation regime (locally up to 40% in equivalent plastic strain) is presented. The coupling between solid and fluid phases is solved through the complete formulation of the Biot’s equations. The additional novelty lies in the employment of an explicit time integration scheme of the $$u-w$$ (solid displacement–relative fluid displacement) formulation which enables us to take advantage of such explicit schemes. Shape functions based on the principle of maximum entropy implemented in the framework of Optimal Transportation Meshfree schemes are utilized to solve both elastic and plastic problems.
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0612-7

• On the stability of geotechnical systems and its fractal progressive loss
• Authors: Gerd Gudehus; Asterios Touplikiotis
Abstract: Geotechnical systems, consisting of soil and embedded solid structures, are practically stable if inevitable actions cause at most harmless redistributions. This kind of robustness can often be achieved with limit state design, i.e. by assuming representative snapshots of worst cases. Changes in configuration and state due to changing boundary conditions can be better judged with quasi-static numerical simulations using validated constitutive relations. The ever-present fractality of the ground may be neglected as long as the system is stable, whereas it gets dominant during a progressive loss of stability with jerky critical phenomena which elude mathematical treatment until present. In this sense geotechnical systems can be or get sensitive, i.e. further actions can trigger detrimental chain reactions with seismogeneous collapse of the soil fabric, pore pressure increase up to liquefaction, erosion, cracking of ground and structural parts and/or tilting. The geotechnical risk can be better mitigated by taking into account chain reactions with wild randomness. It can be further reduced by monitoring the seismic emission in addition to mass flows, structural deformations and pore pressures. The paper is to clarify notions and concepts.
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0549-x

• Modeling competing hydraulic fracture propagation with the extended finite
element method
• Authors: Fushen Liu; Peter A. Gordon; Dakshina M. Valiveti
Abstract: We present an extended finite element framework to numerically study competing hydraulic fracture propagation. The framework is capable of modeling fully coupled hydraulic fracturing processes including fracture propagation, elastoplastic bulk deformation and fluid flow inside both fractures and the wellbore. In particular, the framework incorporates the classical orifice equation to capture fluid pressure loss across perforation clusters linking the wellbore with fractures. Dynamic fluid partitioning among fractures during propagation is solved together with other coupled factors, such as wellbore pressure loss ( $$\Delta p_w$$ ), perforation pressure loss ( $$\Delta p$$ ), interaction stress ( $$\sigma _\mathrm{int}$$ ) and fracture propagation. By numerical examples, we study the effects of perforation pressure loss and wellbore pressure loss on competing fracture propagation under plane-strain conditions. Two dimensionless parameters $$\Gamma = \sigma _\mathrm{int}/\Delta p$$ and $$\Lambda = \Delta p_w/\Delta p$$ are used to describe the transition from uniform fracture propagation to preferential fracture propagation. The numerical examples demonstrate the dimensionless parameter $$\Gamma$$ also works in the elastoplastic media.
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0569-6

• A discrete numerical method for brittle rocks using mathematical
programming
• Authors: J. Meng; J. Huang; C. Yao; D. Sheng
Abstract: A computational formulation of discrete simulations of damage and failure in brittle rocks using mathematical programming methods is proposed. The variational formulations are developed in two and three dimensions. These formulations naturally lead to second-order cone programs and can conveniently be solved using off-the-shelf mathematical programming solvers. Pure static formulations are derived so that no artificial damping parameters are required. The rock is represented by rigid blocks, with interfaces between blocks modelled by zero-thickness springs based on the rigid-body–spring network method. A modified Mohr–Coulomb failure criterion is proposed to model the failure of the interfaces. When the interface’ strength limits are reached, a microscopic crack forms and its strength is irreversibly lost. The microscopic elastic properties of the springs are related to the observed elastic behaviour of rocks with the developed empirical equations. The program is first validated with three simple tests. Then, numerical uniaxial and biaxial compression tests and the Brazilian tests are conducted. Furthermore, the proposed approach is employed to study the rock crack propagation and coalescence using cracked Brazilian disc test. The results are in good agreements with reported experimental data, which shows its potential in modelling mechanical behaviour of brittle rocks.
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0583-8

• SPH approach for simulating hydro-mechanical processes with large
deformations and variable permeabilities
• Authors: M. Gholami Korzani; S. A. Galindo-Torres; A. Scheuermann; D. J. Williams
Abstract: A simulation framework based on Smoothed Particle Hydrodynamics (SPH) is introduced to model problems involving the interaction between flowing water and soil deformation. Changes in soil porosity and associated permeability are automatically adjusted within this framework. The framework’s capabilities are presented and discussed for three geotechnical problems caused by flowing water. The comparison between simulation results and experiments shows that SPH with the proposed concept is capable of quantitatively simulating the hydro-mechanical processes beyond limit state with satisfactory agreement. To improve the computational stability, a correction procedure and a new algorithm for the selection of the optimal time step are introduced.
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0610-9

• Creep behaviour of intact and remoulded fibrous peat
• Authors: Mohan P. Acharya; Michael T. Hendry; C. Derek Martin
Abstract: This paper presents the creep behaviour of intact and remoulded specimens of fibrous peat obtained from a field site near Anzac, Alberta, Canada. The creep behaviour was investigated by means of long-term drained and undrained triaxial tests. The development of volumetric, axial, and undrained axial strain and strain rate during drained and undrained creep tests under variable stress conditions is presented. The stress – strain – strain rate (p′–ε v– $$\dot{\varepsilon }_{\text{v}}$$ ) relationship is found to be unique for different stress and loading durations. The p′–ε v– $$\dot{\varepsilon }_{\text{v}}$$ relationship is analysed and represented by creep isotaches. The applicability of different creep models developed for normally consolidated clay is discussed and applied to define the development of creep strain in fibrous peat under varying isotropic and deviator stresses. The secondary consolidation coefficient for evaluating the volumetric strain rate of peat is found to be applicable with some limits. The drained creep behaviour of remoulded peat specimens differs from the behaviour shown by Shelby tube specimens, whereas the undrained creep behaviour in remoulded and Shelby tube specimens is similar.
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0545-1

• Reaction-driven casing expansion: potential for wellbore leakage
mitigation
• Authors: Timotheus K. T. Wolterbeek; Reinier van Noort; Christopher J. Spiers
Abstract: It is generally challenging to predict the post-abandonment behaviour and integrity of wellbores. Leakage is, moreover, difficult to mitigate, particularly between the steel casing and outer cement sheath. Radially expanding the casing with some form of internal plug, thereby closing annular voids and fractures around it, offers a possible solution to both issues. However, such expansion requires development of substantial internal stresses. Chemical reactions that involve a solid volume increase and produce a force of crystallisation (FoC), such as CaO hydration, offer obvious potential. However, while thermodynamically capable of producing stresses in the GPa range, the maximum stress obtainable by CaO hydration has not been validated or determined experimentally. Here, we report uniaxial compaction/expansion experiments performed in an oedometer-type apparatus on precompacted CaO powder, at 65 °C and at atmospheric pore fluid pressure. Using this set-up, the FoC generated during CaO hydration could be measured directly. Our results show FoC-induced stresses reaching up to 153 MPa, with reaction stopping or slowing down before completion. Failure to achieve the GPa stresses predicted by theory is attributed to competition between FoC development and its inhibiting effect on reaction progress. Microstructural observations indicate that reaction-induced stresses shut down pathways for water into the sample, hampering ongoing reaction and limiting the magnitude of stress build-up to the values observed. The results nonetheless point the way to understanding the behaviour of such systems and to finding engineering solutions that may allow large controlled stresses and strains to be achieved in wellbore sealing operations in future.
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0533-5

• A micro-mechanics-based elastic–plastic model for porous rocks:
applications to sandstone and chalk
• Authors: W. Q. Shen; J. F. Shao
Abstract: A micro-mechanics-based elastic–plastic model is proposed to describe mechanical behaviors of porous rock-like materials. The porous rock is considered as a composite material composed of a solid matrix and spherical pores. The effective elastic properties are determined from the classical Mori–Tanaka linear homogenization scheme. The solid matrix verifies a pressure-dependent Mises–Schleicher-type yield criterion. Based on the analytical macroscopic yield criterion previously determined with a nonlinear homogenization procedure (Shen et al. in Eur J Mech A/Solids 49:531–538, 2015), a complete elastic–plastic model is formulated with the determination of a specific plastic hardening law and plastic potential. The micro-mechanics-based elastic–plastic model is then implemented for a material point in view of simulations of homogeneous laboratory tests. The proposed model is applied to describe mechanical behaviors of two representative porous rocks, sandstone and chalk. Comparisons between numerical results and experimental data are presented for triaxial compression tests with different confining pressures, and they show that the micro-mechanical model is able to capture main features of mechanical behaviors of porous rock-like rocks.
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0536-2

• An ISA-plasticity-based model for viscous and non-viscous clays
• Authors: W. Fuentes; M. Tafili; Th. Triantafyllidis
Abstract: The ISA-plasticity is a mathematical platform which allows to propose constitutive models for soils under a wide range of strain amplitudes. This formulation is based on a state variable, called the intergranular strain, which is related to the strain recent history. The location of the intergranular strain can be related to the strain amplitude, information which is used to improve the model for the simulation of cyclic loading. The present work proposes an ISA-plasticity-based model for the simulation of saturated clays and features the incorporation of a viscous strain rate to enable the simulation of the strain rate dependency. The work explains some aspects of the ISA-plasticity and adapts its formulation for clays. At the beginning, the formulation of the model is explained. Subsequently, some comments about its numerical implementation and parameters determination are given. Finally, some simulations are performed to evaluate the model performance with two different clays, namely a Kaolin clay and the Lower Rhine clay. The simulations include monotonic and cyclic tests under oedometric and triaxial conditions. Some of these experiments include the variation of the strain rate to evaluate the viscous component of the proposed model.
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0548-y

• Effects of sample disturbance and heterogeneity on the triaxial behaviour
of a Canadian oil sand at ambient and high temperatures
• Authors: Ewa Piotrowska; Morteza Mohamadi; Richard Wan
Abstract: The present paper investigates the mechanical behaviour of oil sand specimens in triaxial compression tests at both ambient and elevated temperatures. The emphasis is particularly on core sample disturbance and on the multiphase/strongly heterogeneous nature of the material that introduces difficulties in achieving an objective characterization of its shear behaviour. First, the effect of sample disturbance on the behaviour of the oil sand is studied. Tests are performed on both disturbed and recompressed specimens. Recompression to large stress prior to shearing improves evaluation of the initial stiffness and associated volumetric changes of the oil sand, strongly affected by sample disturbance. A method for the correction of test results obtained from disturbed specimens is also proposed. The corrected results are in good agreement with those pertaining to recompressed specimens. Furthermore, a general classification of the tested oil sands into lean and rich in bitumen, where the former shows much softer and weaker behaviour, is considered to help in addressing the variability in sample composition. As for thermal aspects, the experimental results indicate that both strength and stiffness exhibit a limited temperature dependency. The temperature does not affect lean oil sand specimens, whereas heating considerably increases deformability of rich specimens.
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0575-8

• Effects of initial static shear on cyclic resistance and pore pressure
generation of saturated sand
• Authors: K. Pan; Z. X. Yang
Abstract: In practical engineering, cyclic shear stresses induced by earthquakes, traffic, and waves are superimposed on the initial static shear stress in sand fills or deposits, leading to complex responses of soils such as their deformation characteristics, pore pressure generation, and susceptibility (or cyclic resistance) to liquefaction. To experimentally investigate the undrained cyclic response of saturated sand, a series of triaxial tests were performed, covering a broad range of initial static and cyclic deviatoric stress levels. The results indicate that different stress conditions lead to two types of cyclic behavior: cyclic mobility and residual deformation accumulation. The compressional static stress is beneficial to the cyclic resistance of the dense sand, whereas the extensional static stress is regarded as detrimental as it tended to reduce the cyclic strength. Moreover, by comparing the available test data obtained from the same sand with varying initial densities and confining pressures, the static shear effect on cyclic resistance was found to be dependent on the state of the sand. Compared to the interpretation made using the limiting pore pressure-based criterion, the conventional failure criterion using a cyclic axial strain of 5% may lead to a substantial overestimation of the cyclic resistance, thus resulting in unsafe assessment and design. Hence, by employing the pore pressure criterion, the pore pressure generated in the cyclic tests was investigated and was found to be significantly influenced by the static shear stress. A pore pressure generation model is proposed to obtain the pore pressure characteristics of sand under various static shear stress conditions.
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0614-5

• Permissible range of model parameters for natural fine-grained materials
• Authors: J.-P. Gras; N. Sivasithamparam; M. Karstunen; J. Dijkstra
Abstract: This paper presents a three-dimensional constitutive model for natural clay that includes creep, anisotropy and structure, as well as a theoretical means to estimate the range for anisotropy- and structure-related parameters, as needed for parameter optimisation. Creep-SCLAY1S is an extension of the Creep-SCLAY1 model proposed by Sivasithamparam et al. (Comput Geotech 69:46–57, 2015) which includes the effects of bonding and destructuration. The model needs 14 model parameters, of which five are similar to those used in the modified Cam–Clay model. A method is developed to quantify the range for the three parameters related to structure and anisotropy that cannot be derived directly from experimental data. The theoretically derived range compares favourably with the values found in the literature. As a result, the model now can be used with more confidence, enabling sensitivity analysis and systematic parameter derivation with optimisation techniques.
PubDate: 2018-04-01
DOI: 10.1007/s11440-017-0553-1

• A new incompatible mode element with selective mass scaling for saturated
soil dynamics
• Authors: P. Mira; A. S. Benítez; M. Pastor; J. A. Fernández Merodo
Abstract: It is a well-known fact that addressing hydromechanical problems in saturated soils with the finite element method and equal-order interpolation formulations in displacements and pore pressures produces unstable results. Classically, stabilization has been achieved by increasing the interpolation degree of displacement with respect to pore pressure, hence fulfilling the Babuska–Brezzi condition. However, the use of quadratic elements involves high computational costs. From that point of view, the use of stabilized low-order elements is a more desirable option. Much research has been carried out in different directions in the stabilization of low-order formulations for saturated soils in quasistatic conditions, among others with the technique based on strain field enhancement through internal degrees of freedom. This article presents an alternative displacement–pore pressure formulation for saturated soil dynamics based on the enhancement of the displacement field through incompatible modes.
PubDate: 2018-02-17
DOI: 10.1007/s11440-017-0623-4

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