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1.
A coupled two‐phase fluid flow and elastoplastic deformation model for unsaturated soils: theory,implementation, and application 
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下载免费PDF全文 Although numerous numerical models have been proposed for simulating the coupled hydromechanical behaviors in unsaturated soils, few studies satisfactorily reproduced the soil–water–air three‐phase coupling processes. Particularly, the impacts of deformation dependence of water retention curve, bonding stress, and gas flow on the coupled processes were less examined within a coupled soil–water–air model. Based on our newly developed constitutive models (Hu et al., 2013, 2014, 2015) in which the soil–water–air couplings have been appropriately captured, this study develops a computer code named F2Mus3D to investigate the coupled processes with a focus on the above impacts. In the numerical implementation, the generalized‐α time integration scheme was adopted to solve the equations, and a return‐mapping implicit stress integration scheme was used to update the state variables. The numerical model was verified by two well‐designed laboratory tests and was applied for modeling the coupled elastoplastic deformation and two‐phase fluid flow processes in a homogenous soil slope induced by rainfall infiltration. The simulation results demonstrated that the numerical model well reproduces the initiation of a sheared zone at the toe of the slope and its propagation toward the crest as the rain infiltration proceeds, which manifests a typical mechanism for rainfall‐induced shallow landslides. The simulated plastic strain and deformation would be remarkably underestimated when the bonding stress and/or the deformation‐dependent nature of hydraulic properties are ignored in the coupled model. But on the contrary, the negligence of gas flow in the slope soil results in an overestimation of the rainfall‐induced deformation. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
2.
A large-strain elastoplastic analysis is presented for a cylindrical cavity embedded in an infinite medium under uniform radial pressure. The investigation employs invariant, non-associated deformation-type theories for Mohr–Coulomb (M–C) and Drucker–Prager (D–P) solids, accounting for arbitrary hardening, with the equivalent stress as the independent variable. The M–C model results in a single first-order differential equation, whereas for the D–P solid an algebraic constraint supplements the governing differential equation. Material parameters and response characteristics were determined by calibrating the models with data from triaxial compression tests on Castlegate sandstone and on Jurassic shale. A comparison is presented between predictions obtained from the two models and experimental data from hollow cylinder tests under external loading. A sensitivity of the results to material parameters, like friction and dilation angles, is provided for the case of a cavity subjected to internal pressure in terms of limit pressure predictions. In all cases it has been found that the results of the D–P inner cone model are in close agreement with those obtained from the M–C model. © 1997 by John Wiley & Sons, Ltd. 相似文献
3.
In this paper, the novel concept of probabilistic yielding is used for 1‐D cyclic simulation of the constitutive behavior of geomaterials. Fokker–Planck–Kolmogorov equation‐based probabilistic elastic–plastic constitutive framework is applied for obtaining the complete probabilistic (probability density function) material response. Both perfectly plastic and hardening‐type material models are considered. It is shown that when uncertainties in material parameters are taken into consideration, even the simple, elastic‐perfectly plastic model captures some of the important features of geomaterial behavior, for example, modulus reduction with cyclic strain, which, deterministically, is only possible with more advanced constitutive models. Furthermore, it is also shown that the use of isotropic and kinematic hardening rules does not significantly improve the probabilistic material response. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
4.
Numerical models are commonly used to estimate excavation‐induced ground movements. Two‐dimensional (2D) plain strain assumption is typically used for the simulation of deep excavations which might not be suitable for excavations where three‐dimensional (3D) effects dominate the ground response. This paper adapts an inverse analysis algorithm to learn soil behavior from field measurements using a 3D model representation of an excavation. The paper describes numerical issues related to this development including the generation of the 3D model mesh from laser scan images of the excavation. The inverse analysis to extract the soil behavior in 3D is presented. The model captures the measured wall deflections. Although settlements were not sufficiently measured, the predicted settlements around the excavation site reflected strong 3D effects and were consistent with empirical correlations. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
5.
This paper presents an embedded beam formulation for discretization independent finite element (FE) analyses of interactions between pile foundations or rock anchors and the surrounding soil in geotechnical and tunneling engineering. Piles are represented by means of finite beam elements embedded within FEs for the soil represented by 3D solid elements. The proposed formulation allows consideration of piles and pile groups with arbitrary orientation independently from the FE discretization of the surrounding soil. The interface behavior between piles and the surrounding soil is represented numerically by means of a contact formulation considering skin friction as well as pile tip resistance. The pile–soil interaction along the pile skin is considered by means of a 3D frictional point‐to‐point contact formulation using the integration points of the beam elements and reference points arbitrarily located within the solid elements as control points. The ability of the proposed embedded pile model to represent groups of piles objected to combined axial and shear loading and their interactions with the surrounding soil is demonstrated by selected benchmark examples. The pile model is applied to the numerical simulation of shield driven tunnel construction in the vicinity of an existing building resting upon pile foundation to demonstrate the performance of the proposed model in complex simulation environments. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
6.
This paper proposes a numerical model for jointed rock masses within the 3‐D numerical manifold method (NMM) framework equipped with a customized contact algorithm. The strength of rock sample containing a few sets of discontinuities is first investigated. The results of models with simple geometries are compared with the available analytical solutions to verify the developed computer code, whereas models with complex geometries are simulated to better understand the fundamental behavior and failure mechanism of jointed rock mass. Furthermore, the stability of jointed rock mass in an underground excavation is studied, where rock failure process is determined by the 3‐D NMM simulation. The simulation results provide valuable guidance on excavation process design and stabilization design in rock engineering practice. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
7.
In this paper, the seismic response of ‘infinitely’ long slopes is numerically analysed via the formulation of a 1D analytical/numerical model, in which the soil mechanical behaviour is assumed to be elasto‐perfectly viscoplastic and simple shear (SS) kinematical constraints are imposed. In order to simplify the problem, a theoretically based procedure to set up a fully 1D shear constitutive model is defined, within which the mechanical response of a multiaxial relationship is condensed. The use of a 1D shear constitutive model is aimed at reducing the number of unknowns and, therefore, the computational costs. In particular, the case of the Mohr–Coulomb yield criterion is considered, while an enhanced Taylor–Galerkin finite element algorithm is employed to simulate the seismic wave propagation within the soil stratum. The proposed ‘condensation’/calibration procedure captures both the ‘pseudo’‐hardening pre‐failure behaviour and the influence of dilation on the occurrence of strain‐localization, which characterize, under SS conditions, the static response of virgin perfectly plastic soils. The effectiveness of the conceived method is shown with reference to freshly deposited deposits, while, in the case of highly overconsolidated strata, some difficulties arise because of the brittle behaviour induced both by unloading and non‐associativeness. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
8.
Time‐domain analysis of dynamic soil–structure interaction based on the substructure method plays an increasing role in practical applications as compared with the frequency‐domain analysis. Efficient and accurate modelling of the unbounded soil or rock medium has been a key issue in such an analysis. This paper presents a subregional stepwise damping‐solvent extraction formulation for solving large‐scale dynamic soil–structure problems in the time domain. Accuracy and efficiency of the formulation are evaluated in detail for a classical problem involving a rigid strip foundation embedded in a half‐space. A practical large‐scale soil–structure interaction problem, which represents a high concrete gravity dam subjected to seismic load, is then analysed using the proposed method. Various responses of the dam, including time histories of the crest displacement and acceleration and contours of the peak principal stresses within the dam body, are presented. Comparisons are also made between these results with those obtained using other models for the unbounded medium. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
9.
This paper studies the excavation of a spherical cavity subjected to hydrostatic initial stresses in the infinite homogeneous and isotropic rock mass with strain‐softening Mohr–Coulomb (M‐C) and Hoek–Brown (H‐B) behaviors. Numerical solutions of the spherical cavity are obtained and the application to determining stress–strain curve of strain‐softening M‐C and H‐B rock mass is studied. A closed‐form solution for the elastic–brittle–plastic medium is introduced first, and then a numerical procedure that simplifies the strain‐softening process into a series of brittle–plastic ones is presented. The approach is validated against the facts that the strain‐softening process evolves into a brittle–plastic one when the softening slope is very steep, whereas it evolves into an elasto‐plastic one when the softening slope approaches zero. Numerical solutions for the prediction of displacements and stresses around the spherical cavity in the strain‐softening M‐C and H‐B rock mass are presented. On the basis of the analysis of the spherical cavity in strain‐softening rock mass, the stress–strain relationship at an infinitesimal cube around the cavity is obtained and discussed with different evolution laws for the strength parameters considered. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
10.
Petrological investigations supported by multi‐scale structural analysis of eclogitized serpentinite in the Zermatt–Saas Zone of the Western Alps allows for the determination of mineral assemblages related to successive fabrics, upon which the P–T–d–t path of these hydrated mantle rocks can be inferred. Serpentinites of the upper Valtournanche, with lenses and dykes of metagabbro and meta‐rodingite, display an Alpine polyphase metamorphic evolution from eclogite to epidote‐amphibolite facies conditions associated with three successive foliations having different parageneses in these rocks. Serpentinite mainly consists of serpentine with minor magnetite; however, where S1 and S2 foliations are pervasive, metamorphic olivine, together with Ti‐clinohumite and clinopyroxene, are also found. The mineral assemblage associated with D1 includes serpentine1, clinopyroxene1, opaque minerals, titanite ± olivine1, Ti‐clinohumite1 and ilmenite; the D2 assemblage is the same (±chlorite) but minerals have different compositions. The assemblage associated with D3 comprises serpentine3, opaque minerals, ±chlorite3, ilmenite and amphibole3. Ti‐clinohumite is associated with veins that are older than D2 and pre‐date D3. Veins that post‐date D3 are characterized by amphibole + chlorite or by serpentine. P–T conditions for S2 parageneses evaluated using two pseudosections for different bulk compositions suggest that these rocks experienced pressures >2.5 ± 0.3 GPa at temperatures slightly higher than 600 °C. The late epidote–amphibolite facies re‐equilibration associated with D3 and D4 developed during late syn‐exhumation deformation related to folding and testifies to a small temperature decrease. These results, which were integrated in the regional framework, suggest that different portions of the Zermatt–Saas Zone registered different P–T peak conditions and underwent different exhumation paths. In addition, the inferred P–T–d–t path suggests that the Valtournanche serpentinites re‐equilibrated close to the UHP conditions registered by the Cignana meta‐cherts. These results imply that tectonic slices exhumed after UHP metamorphism might be wider than previously reported or that small‐size UHP units, tectonically sampled during the Alpine convergence, are more abundant than those that have been detected to date. 相似文献
11.
A boundary element model for stress/stability analysis of underground excavations in the vicinity of faults is presented. The boundary element formulation adopts the fictitious stress method for the simulation of excavation boundaries and the displacement discontinuity method for the representation of faults. The numerical model employs the Barton–Bandis non-linear joint model for the modelling of the fault behaviour and linear elastic behaviour for the rock. An incremental-iterative in situ stress relaxation algorithm is implemented for the non-linear analysis of the faults. Both deformation and peak strength models of Barton–Bandis are incorporated for modelling the mechanical behaviour of the fault. The non-linear deformation of fault considers the effects of coupling between shear and normal stresses and displacement, joint closure, joint separation, hardening followed by post-peak or residual behaviour. The peak strength model employs a mobilized non-linear shear strength envelope. The differences between linear and non-linear simulation of the fault models are discussed. A comparison of model predictions with the classical Mohr–Coulomb peak strength model with constant joint stiffness is presented. The numerical model is used for a case study of Canadian hard rock underground mine. The shear and normal displacements along the fault during four mining sequences with backfill simulation are presented and discussed. 相似文献
12.
Petrogenesis and deformation history of the lawsonite‐bearing blueschist facies metabasalts of the Diamante‐Terranova oceanic unit (southern Italy) 下载免费PDF全文
下载免费PDF全文 L. Fedele F. D'A. Tramparulo S. Vitale P. Cappelletti E. P. Prinzi S. Mazzoli 《Journal of Metamorphic Geology》2018,36(6):691-714
The Neotethyan oceanic Diamante‐Terranova unit (DIATU; southern Apennines–Calabria–Peloritani Terrane system) includes basic rocks that during the Cenozoic were subducted and metamorphosed to lawsonite‐blueschist facies conditions. Petrological and structural observations (both at the meso‐ and micro‐scale) show that lawsonite growth was continuous during three distinctive ductile deformation stages (D1–D3). These likely occurred close to the metamorphic peak, estimated at 350–390°C and 0.9–1.1 GPa, producing an equilibrium assemblage made of blue Na‐amphibole, lawsonite, chlorite and pumpellyite. Locally, pods dominated by quartz and epidote (plus chlorite, calcite and green Ca‐amphibole) developed at similar conditions (350–370°C, 0.8–0.9 GPa). Post‐peak evolution during the final exhumation of the DIATU along the subduction channel, also consisted of three deformation stages, defined by folding (D4) and normal faulting (D5) and finally by strike‐slip faulting (D6), affecting both the blueschist unit and the unconformably overlying Tortonian conglomerates. Vorticity analysis on syn‐tectonic lawsonite crystals indicates that severe flattening occurred during the D2 stage, with a significant secondary non‐coaxial strain component along the W–E plane. This is associated with an eastward tectonic vergence, consistent with the subsequent D3 and D4 folding stages characterized by a dominant ENE tectonic transport. It is suggested that exhumation started from the D2 stage and continued during D3 at similar HP/LT metamorphic conditions. The widespread occurrence of unreacted lawsonite crystals suggests that exhumation was very fast and supports the idea that concurrent ductile deformation might play a role in its preservation. 相似文献
13.
The effect of tunneling on surrounding environments, especially on existing buried pipelines is a problem that engineers designing and practicing in urban geotechnical environments encounter more frequently than in the past. However, previous studies are usually based on the assumption that the soil is homogeneous. How to reflect soil stratification is the main focus for the problem of tunneling in multi‐layered soils. A displacement controlled coupling numerical method is presented for the displacement analysis of tunnel excavation below existing pipelines in multi‐layered soils. On the basis of the layered soil model, to consider the soil nonhomogeneous characteristic, the finite element method and boundary element method are coupled to simulate the deformation of existing pipelines induced by tunneling. The solutions indicate that good agreements are obtained between the proposed coupling numerical method and the commercial software. The accuracy of the proposed numerical method is better than the two stages method based on the existing closed‐form solutions. Moreover, the results discussed in this paper show that the error obtained by the previous method of weighted average on the basis of homogeneous half space converted from layered soils is not negligible for the obvious difference of elastic parameters among successive layers. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
14.
This paper presents a non‐linear coupled finite element–boundary element approach for the prediction of free field vibrations due to vibratory and impact pile driving. Both the non‐linear constitutive behavior of the soil in the vicinity of the pile and the dynamic interaction between the pile and the soil are accounted for. A subdomain approach is used, defining a generalized structure consisting of the pile and a bounded region of soil around the pile, and an unbounded exterior linear soil domain. The soil around the pile may exhibit non‐linear constitutive behavior and is modelled with a time‐domain finite element method. The dynamic stiffness matrix of the exterior unbounded soil domain is calculated using a boundary element formulation in the frequency domain based on a limited number of modes defined on the interface between the generalized structure and the unbounded soil. The soil–structure interaction forces are evaluated as a convolution of the displacement history and the soil flexibility matrices, which are obtained by an inverse Fourier transformation from the frequency to the time domain. This results in a hybrid frequency–time domain formulation of the non‐linear dynamic soil–structure interaction problem, which is solved in the time domain using Newmark's time integration method; the interaction force time history is evaluated using the θ‐scheme in order to obtain stable solutions. The proposed hybrid formulation is validated for linear problems of vibratory and impact pile driving, showing very good agreement with the results obtained with a frequency‐domain solution. Linear predictions, however, overestimate the free field peak particle velocities as observed in reported field experiments during vibratory and impact pile driving at comparable levels of the transferred energy. This is mainly due to energy dissipation related to plastic deformations in the soil around the pile. Ground vibrations due to vibratory and impact pile driving are, therefore, also computed with a non‐linear model where the soil is modelled as an isotropic elastic, perfectly plastic solid, which yields according to the Drucker–Prager failure criterion. This results in lower predicted free field vibrations with respect to linear predictions, which are also in much better agreement with experimental results recorded during vibratory and impact pile driving. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
15.
E. Skrzypek J. Lehmann J. Szczepański R. Anczkiewicz P. Štípská K. Schulmann A. Kröner D. Białek 《Journal of Metamorphic Geology》2014,32(9):981-1003
A section of the orogenic middle crust (Orlica‐?nie?nik Dome, Polish/Czech Central Sudetes) was examined to constrain the duration and significance of deformation (D) and intertectonic (I) phases. In the studied metasedimentary synform, three deformation events produced an initial subhorizontal foliation S1 (D1), a subsequent subvertical foliation S2 (D2) and a late subhorizontal axial planar cleavage S3 (D3). The synform was intruded by pre‐, syn‐ and post‐D2 granitoid sheets. Crystallization–deformation relationships in mica schist samples document I1–2 garnet–staurolite growth, syn‐D2 staurolite breakdown to garnet–biotite–sillimanite/andalusite, I2–3 cordierite blastesis and late‐D3 chlorite growth. Garnet porphyroblasts show a linear Mn–Ca decrease from the core to the inner rim, a zone of alternating Ca–Y‐ and P‐rich annuli in the inner rim, and a Ca‐poor outer rim. The Ca–Y‐rich annuli probably reflect the occurrence of the allanite‐to‐monazite transition at conditions of the staurolite isograd, whereas the Ca‐poor outer rim is ascribed to staurolite demise. The reconstructed P–T path, obtained by modelling the stability of parageneses and garnet zoning, documents near‐isobaric heating from ~4 kbar/485 °C to ~4.75 kbar/575 °C during I1–2. This was followed by a progression to 4–5 kbar/580–625 °C and a subsequent pressure decrease to 3–4 kbar during D2. Pressure decrease below 3 kbar is ascribed to I2–3, whereas cooling below ~500 °C occurred during D3. In the dated mica schist sample, garnet rims show strong Lu enrichment, oscillatory Lu zoning and a slight Ca increase. These features are also related to allanite breakdown coeval with staurolite appearance. As Lu‐rich garnet rims dominate the Lu–Hf budget, the 344 ± 3 Ma isochron age is ascribed to garnet crystallization at staurolite grade, near the end of I1–2. For the dated sample of amphibole–biotite granitoid sheet, a Pb–Pb single zircon evaporation age of 353 ± 1 Ma is related to the onset of plutonic activity. The results suggest a possible Devonian age for D1, and a Carboniferous burial‐exhumation cycle in mid‐crustal rocks that is broadly coeval with the exhumation of neighbouring HP rocks during D2. In the light of published ages, a succession of telescoping stages with time spans decreasing from c. 10 to 2–3 Ma is proposed. The initially long period of tectonic quiescence (I1–2 phase, c. 10 Ma) inferred in the middle crust contrasts with contemporaneous deformation at deeper levels and points to decoupled P–T–D histories within the orogenic wedge. An elevated gradient of ~30 °C km?1 and assumed high heating rates of c. 20 °C Ma?1 are explained by the protracted intrusion of granitoid sheets, with or without deformation, whereas fast vertical movements (2–3 Ma, D2 phase) in the crust require the activity of deformation phases. 相似文献
16.
Discrete element modelling of deep penetration in granular soils 总被引：1，自引：0，他引：1
This paper presents a numerical study on deep penetration mechanisms in granular materials with the focus on the effect of soil–penetrometer interface friction. A two‐dimensional discrete element method has been used to carry out simulation of deep penetration tests on a granular ground that is under an amplified gravity with a K0 lateral stress boundary. The numerical results show that the deep penetration makes the soil near the penetrometer move in a complex displacement path, undergo an evident loading and unloading process, and a rotation of principal stresses as large as 180°. In addition, the penetration leads to significant changes in displacement and velocity fields as well as the magnitude and direction of stresses. In general, during the whole penetration process, the granular ground undergoes several kinds of failure mechanisms in sequence, and the soil of large deformation may reach a stress state slightly over the strength envelope obtained from conventional compression tests. Soil–penetrometer interface friction has clear effects on the actual penetration mechanisms. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
17.
Simulation of large deformation and post‐failure of geomaterial in the framework of smoothed particle hydrodynamics (SPH) are presented in this study. The Drucker–Prager model with associated and non‐associated plastic flow rules is implemented into the SPH code to describe elastic–plastic soil behavior. In contrast to previous work on SPH for solids, where the hydrostatic pressure is often estimated from density by an equation of state, this study proposes to calculate the hydrostatic pressure of soil directly from constitutive models. Results obtained in this paper show that the original SPH method, which has been successfully applied to a vast range of problems, is unable to directly solve elastic–plastic flows of soil because of the so‐called SPH tensile instability. This numerical instability may result in unrealistic fracture and particles clustering in SPH simulation. For non‐cohesive soil, the instability is not serious and can be completely removed by using a tension cracking treatment from soil constitutive model and thereby give realistic soil behavior. However, the serious tensile instability that is found in SPH application for cohesive soil requires a special treatment to overcome this problem. In this paper, an artificial stress method is applied to remove the SPH numerical instability in cohesive soil. A number of numerical tests are carried out to check the capability of SPH in the current application. Numerical results are then compared with experimental and finite element method solutions. The good agreement obtained from these comparisons suggests that SPH can be extended to general geotechnical problems. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
18.
In this work, we present a numerical procedure for determining the nature stress state in the rock mass around a tunnel. A finite element method is applied for analyzing the direct problems of tunneling during the back analysis of parameter estimation, in which a no‐tension elastic–plastic model is used to simulate the elastic–tensile and elastic–plastic‐tensile failure states which often occur in the cases of underground excavation in heavily jointed rock masses. By considering the natural stress state as random parameters of the tunneling system, the Kalman filter method is employed for feedback analysis to modify the parameter values in a statistical context, which uses the prior information in the process of estimation and employs a set of displacements obtained from field measurements. To verify the effectiveness of the proposed method of inverse analysis, the developed numerical procedure is applied to a synthetic example of deep tunnels in yielding rock masses. The relative importance of the a priori and updating information is investigated, as is the importance of their uncertainty. The results show great potential of the proposed approach. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
19.
A non-linear seismic response analysis method for 2-D saturated soil–structure system with an absorbing boundary is presented. According to the 3-D strain space multimechanism model for the cyclic mobility of sandy soil, a constitutive expression for the plane strain condition is first given. Next, based on Biot's two-phase mixture theory, the finite element equations of motion for a saturated soil–structure system with an absorbing boundary during earthquake loadings are derived. A simulation of the shaking table test is performed by applying the proposed constitutive model. The effectiveness of the absorbing boundary is examined for the 2-D non-linear finite element models subjected to random inputs. Finally, a numerical seismic response analysis for a typical saturated soil–structure system is performed as an application of the proposed method. 相似文献
20.
According to Litwiniszyn's theory, subsidence over a yielding underground geo‐structure is seen as a stochastic (Markov) process. This theory leads to a single, linear parabolic differential equation of diffusion–convection type (D–C equation) in the plane‐field of displacements. If the boundary conditions for the governing D–C equation are prescribed along the shear bands, i.e. at ‘moving’ boundaries—it has been observed from small‐scale model experiments that the subsiding process is always confined between a set of inclined shear bands—then the resulting equation is nonlinear. The inverse problem for this nonlinear equation, i.e. the problem of determining the base displacement using the surface subsidence as ‘initial’ condition, is ill‐posed and estimation of the base displacement from a given surface subsidence profile is not possible. In the present paper the domain of integration of the governing D–C equation is fixed (and bounded)—the boundaries are not evolving. Hence, the governing equation remains linear parabolic. The advantage is that this linear differential equation admits an analytical solution, under the trap‐door mechanism assumption, that enables a direct solution to the inverse problem. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献