Non‐isothermal plasticity model for cyclic behaviour of soils     

L. Laloui  C. Cekerevac 《国际地质力学数值与分析法杂志》2008,32(5):437-460

On the one hand, it has been observed that liquefaction‐induced shear deformation of soils accumulates in a cycle‐by‐cycle pattern. On the other hand, it is known that heating could induce plastic hardening. This study deals with the constitutive modelling of the effect that heat may have on the cyclic mechanical properties of cohesive soils, a relatively new area of interest in soil mechanics. In this paper, after a presentation of the thermo‐mechanical framework, a non‐isothermal plasticity cyclic model formulation is presented and discussed. The model calibration is described based on data from laboratory sample tests. It includes numerical simulations of triaxial shear tests at various constant temperatures. Then, the model predictions are compared with experimental results and discussed in the final section. Both drained and undrained loading conditions are considered. The proposed constitutive model shows good ability to capture the characteristic features of behaviour. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Viscous behaviour of dry sand     

D. Pham Van Bang  H. Di Benedetto  A. Duttine  A. Ezaoui 《国际地质力学数值与分析法杂志》2007,31(15):1631-1658

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Thermophysical properties of the α–β–γ polymorphs of Mg<Subscript>2</Subscript>SiO<Subscript>4</Subscript>: a computational study     

G. Ottonello  B. Civalleri  J. Ganguly  M. Vetuschi Zuccolini  Y. Noel 《Physics and Chemistry of Minerals》2009,36(2):87-106

Thermophysical properties of the various polymorphs (i.e. α-, β- and γ) of Mg₂SiO₄ were computed with the CRYSTAL06 code within the framework of CO-LCAO-GTF approach by using the hybrid B3LYP density functional method. Potential wells were calculated through a symmetry preserving, variable cell-shape structure relaxation procedure. Vibrational frequencies were computed at the long-wavelength limit corresponding to the center of the Brillouin zone (k → 0). Thermodynamic properties were estimated through a semiclassical approach that combines B3LYP vibrational frequencies for optic modes and the Kieffer’s model for the dispersion relation of acoustic modes. All computed values except volume (i.e. electronic energy, zero point energy, optical vibrational modes, thermal corrections to internal energy, standard state enthalpy and Gibbs free energy of reaction, bulk modulus and its P and T derivatives, entropy, C _V, C _P) are consistent with available experimental data and/or reasonable estimates. Volumes are slightly overestimated relative to those determined directly by X-ray diffraction. A set of optimized volumetric properties that are consistent with the other semiclassical properties of the phases α, β and γ have been derived by optimization procedure such that the calculated boundaries for the α/β and β/γ equilibria have the best overall agreement with the experimental data for these transitions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

G. OttonelloEmail:

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Visco-Plastic Behaviour around Advancing Tunnels in Squeezing Rock   总被引：3，自引：1，他引：2  

D. Sterpi  G. Gioda 《Rock Mechanics and Rock Engineering》2009,42(2):319-339

Summary  The visco-plastic behaviour of rocks plays a relevant role in the tunnelling works, especially for deep tunnels subjected to large initial stresses for which squeezing conditions may develop. A rheological model is discussed that accounts for visco-elastic (primary) and visco-plastic (secondary) contributions to rock creep. The effects of tertiary creep are included in the model by way of a gradual mechanical damage governed by the cumulated visco-plastic strains. The parameters of the intact rock are first identified based on laboratory test results presented in the literature. Then, after scaling them to those of the rock mass, the potential applicability of the model is tested through axisymmetric and plane strain finite element analyses of the full face excavation of a deep circular tunnel. The results are discussed with particular reference to the short term redistribution of stresses around the opening and to its convergence. The analyses show the relevant influence of tertiary creep on the tunnel closure. In addition, those based on an axisymmetric scheme turn out to be crucial for the correct long term prediction of the interaction between the rock mass and the supporting structure of the opening.  相似文献   

岩石破裂行为的实验研究   总被引：6，自引：0，他引：6  

葛和平  孙岩  朱文斌  郭继春  刘德良  陈祥云  王锋  温世红 《高校地质学报》2004,10(2):290-296

岩样的破裂行为、破坏过程和参数测试是裂隙断裂构造研究的基础和依据。实验岩石样品采自四川东部和新疆北部地区,为测试准确起见,对岩样进行了应力等值线的有限元法计算。通过单轴和三轴实验的岩样破坏观察和应力应变曲线对比,将岩石的破裂行为、应力应变划分为四个阶段,即裂隙压密阶段、弹性变形阶段、微观劈裂阶段和宏观破裂阶段。基于单轴抗压实验岩石劈裂—破裂—碎裂发展过程的微观分析,可以看出宏观破裂主要是沿岩样原有的隐裂隙、临界裂隙发育的,许多新裂隙则主要是在宏观破裂阶段产生的。  相似文献   

一个饱和超固结黏土的应力-应变-时间关系     

王琛  彭越 《岩土力学》2006,27(Z2):191-194

提出了一个考虑超固结黏土应变软化特性的应力-应变-时间关系,其应变-时间关系采用幂函数,应力-应变关系采用双曲线方程的改进模式。该方程的试验参数引入了脆性指数和超固结比,不仅能模拟应变硬化型应力-应变-时间关系,而且能模拟应变软化型应力-应变-时间关系,是应变硬化型应力-应变-时间方程的推广。并针对常应变率试验结果进行预测,证明了该方程的合理性。  相似文献   

钙质砂中的桩基工程研究进展述评   总被引：1，自引：0，他引：1  

单华刚  汪稔 《岩土力学》2000,21(3):299-304

系统综述了钙质砂中桩基工程研究的历史和现状, 分析了钙质砂的低桩基承载力的原因, 提出今后重点研究方向  相似文献   

Simulation studies on the pyrope-grossular garnet solid solution     

A. Bosenick  M. T. Dove  C. A. Geiger 《Physics and Chemistry of Minerals》2000,27(6):398-418

The local structural response of Ca/Mg substitution and the energetic effects associated with dodecahedral ordering in the pyrope-grossular garnet solid solution are derived from a combination of static lattice energy calculations and Monte Carlo simulations. We start with a thorough analysis of the goodness of the empirical potential models used for the modelling of aluminosilicate garnets. The degree of polyhedral distortion was found to be a sensitive indicator for the quality of the model and, by comparison with experimental data, was used to select the best of several available empirical potentials. The Ca/Mg substitution on the dodecahedral site in garnet was found to produce strong local distortions in the surrounding tetrahedral and octahedral polyhedra. This arises from the absence of rigid unit modes (RUMS) in the garnet structure, because local rotations of otherwise rigid SiO₄ tetrahedra and AlO₆ octahedra cannot occur in order to accommodate different-sized divalent cations in the dodecahedral sites. Strain effects, therefore, mainly govern the dodecahedral substitution, and the corresponding strain field around a dodecahedral site has a minimum radius of 5?Å. Pyrope-grossular solid solution compositions were modelled using a supercell approach. For several garnet compositions many different configurations representing individual disordered arrangements were relaxed. The resulting energies were analyzed in terms of different-neighbour interactions to determine the parameters of a model Hamiltonian. The corresponding interaction energies were found to be virtually independent of composition. Surprisingly, the nearest-neighbour interaction between edge-sharing dodecahedra is of no particular significance in the garnets. Instead, the strongest interaction is only via the third-nearest neighbours, i.e. dodecahedra that are edge-shared to a common SiO₄ tetrahedron. This cannot lead to dodecahedral long-range order in garnets, but can produce significant amounts of short-range order. Monte Carlo simulations were performed on several compositions to determine the macroscopic effects such as NMR-based cluster occupancy, ordering energy and configurational entropy of the short-range ordering process. As expected, the samples tend to random disorder at high temperatures, and at low temperatures it is compositions nearer Py50Gr50 that depart most strongly from random mixing. For example, a maximum reduction of 3.5?J?mol^?1?K^?1 is predicted for Py75Gr25 and ～10?J?mol^?1?K^?1 for Py50Gr50. A comparison of NMR cluster occupancy with experimental ²⁹Si MAS NMR resonance intensity is partly successful. However, the changes in NMR cluster occupancy are relatively low (～5%) compared to changes in configurational entropy (～30%), implying that it might be difficult to estimate exact entropy data from ²⁹Si MAS NMR line intensities.  相似文献   

考虑围岩软化特性和应力释放的圆形隧道黏弹塑性解   总被引：1，自引：0，他引：1  

卞跃威  夏才初  肖维民  张国柱 《岩土力学》2013,34(1):211-220

将围岩的塑性应变软化特性引入到考虑应力释放的圆形隧道黏弹塑性解中,并且在围岩的软化和残余强度阶段考虑围岩的塑性体积膨胀特性,提出了考虑塑性软化以及塑性体积膨胀和围岩应力释放的圆形隧道弹塑性解。当软化系数k = ∞、膨胀系数h = s时,该解转化为黏弹-脆塑性解;当k = 0、h = s时,则转化为黏弹-理想塑性解,进一步令h = s = 1,则转化为不考虑塑性体积膨胀的黏弹-理想塑性解。通过具体实例计算,分析了掌子面与研究断面间距x、围岩的软化系数k、膨胀系数h和s、支护结构等对围岩塑性区、破碎区半径和变形的影响。当开挖面与研究断面间距x在(0~4)D（D为隧道直径）范围内,随着时间增加塑性圈和破碎区迅速增大;超过4D,塑性区和破碎区半径增量逐渐变小,趋于稳定值;围岩中包含塑性区和破碎区时,二者半径的比值只取决于围岩的性质,与支护结构无关,但支护结构可以限制塑性区及破碎区的范围;考虑应变软化和塑性体积膨胀时,围岩径向位移和塑性区及破碎区半径均大于不考虑应变软化和塑性体积膨胀时的结果;软化系数k增大,围岩位移、塑性区和破碎区半径增加、塑性区半径和破碎区半径之间的比值变小。得到的结果对于隧道工程设计和施工具有一定的指导性和参考价值。  相似文献   

Out‐of‐plane seismic behaviour of rocking masonry walls     

Omar Al Shawa  Gianmarco de Felice  Alberto Mauro  Luigi Sorrentino 《地震工程与结构动力学》2012,41(5):949-968

The evaluation of the out‐of‐plane behaviour of unreinforced walls is one of the most debated topics in the seismic assessment of existing masonry buildings. The discontinuous nature of masonry and its interaction with the remainder of the building make the dynamic modelling of out‐of‐plane response troublesome. In this paper, the results of a shaking table laboratory campaign on a tuff masonry, natural scale, U‐shaped assemblage (façade adjacent to transverse walls) are presented. The tests, excited by scaled natural accelerograms, replicate the behaviour of external walls in existing masonry buildings, from the beginning of rocking motion to overturning. Two approaches have been developed for modelling the out‐of‐plane seismic behaviour: the discrete element method and an SDOF analytic model. Both approaches are shown to be capable of reproducing the experimental behaviour in terms of maximum rotation and time history dynamic response. Finally, test results and numerical time history simulations have been compared with the Italian seismic code assessment procedures. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献