共查询到20条相似文献，搜索用时 31 毫秒
1.
基于循环交通荷载下软黏土累积塑性变形、累积孔压经验公式与分层总和法结合的方法,通过计算不排水循环累积塑性变形引起的沉降和不排水循环累积孔压消散引起的固结沉降叠加,建立了一个软土路基长期沉降拟静力计算模型。对交通荷载应力路径下的软黏土空心圆柱扭剪试验数据分析,获得了不排水累积塑性应变模型和不排水累积孔压公式的参数。基于弹性理论解积分计算交通荷载下路基中的动应力,再结合分层总和法计算了路基沉降与循环周次的关系。通过工程实例分析,对比了计算沉降结果与实测结果并与以往理论分析结果,验证了所建立模型的合理性。 相似文献
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考虑中主应力时土体劈裂灌浆力学机制的大变形分析 总被引：2，自引：0，他引：2
在塑性力学和大变形理论的基础上分析土体在劈裂灌浆初始阶段的力学机制,将劈裂灌浆的初始阶段视为无限土体中的圆孔扩张问题,并将圆孔周围土体中的应力分布分为两个区域。在弹性区中土体服从小变形假设,在塑性区中服从大变形假设。假设初始劈裂灌浆压力是圆孔扩张到极限时极限扩孔压力;当土体在灌浆压力作用下,大小主应力正好换位时,则出现劈裂时的灌浆压力就为二次劈裂灌浆压力值,推导出塑性区半径、劈裂灌浆的竖向劈裂灌浆和水平向劈裂灌浆压力的理论解答,同时也获得了弹塑性区中的应力场分布规律。该理论的计算结果与工程实测结果比较接近,初步证实了该理论的可靠性。 相似文献
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A solution is presented for the radial consolidation around stone columns under constant surcharge load. The solution considers the influence of vertical and radial deformation of the column, either in elastic and elastoplastic regimes. The solution is in terms of the average excess pore pressure in the soil. It is based on previous solutions, initially developed for rigid column, or including only vertical deformation. For elastic column, the solution gives the variation of strains and stresses between the undrained and final states, for which it coincides with the existing elastic solutions. All the results are given in closed form, and both the elastic and plastic deformations of the column lead to an equivalent coefficient of consolidation for the radial flow, which enables the application of the existing methods of integration of the consolidation equation. A parametric study is presented, showing the influence of the main problem features. A design example is used to illustrate the application to practical cases. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Panichev Aleksander Seryodkin Ivan Popov Vladimir Chekryzhov Igor Makarevich Raisa Lutsenko Tatiana Stolyarova Tatiana Sergievich Aleksander Khoroshikh Pavel Maksimova Darya Petrunenko Yury 《Arabian Journal of Geosciences》2020,13(4):1-11
This paper establishes a mechanical model of the stress distribution in front of the driving face during coal roadway excavation. Theoretical research shows that the stress state in the plastic zone of the driving face is consistent with the limit equilibrium equation, and the elastic zone is in accordance with the equilibrium equation based on elasticity mechanics. Based on this improved mechanical state solution model, different coal material constitutive hypotheses are used for the analysis. The width of the plastic zone calculated under the brittle-perfectly elastic model can reach 2–5 times the height of the roadway, and the stress concentration coefficient can reach two or more times. 3DEC numerical simulation software was used to simulate the stress distribution of the heading face. The results of the simulation are similar to those of the theoretical analysis. Compared with the elastic-perfectly plastic model, the calculated results of the brittle-perfectly elastic model are more consistent with the numerical simulation results. The heading face coal during roadway excavation shows obvious damage, and the strength characteristics of the coal decrease. 相似文献
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针对某原型工程采用的新型气泡轻质填土路基,通过室内相似模型试验和UDEC数值模拟相结合分析的手段,研究该气泡轻质土路基在受载-破坏过程中的变形特征和受力破坏机制,得到了该过程中路基内部的应变变化、应力分布以及沉降变形规律等数据。研究表明：该种气泡轻质土路基在受载-破坏过程中,内部老路基首先发生变形,当荷载达到175 kPa后,中层左侧轻质土路基内部最先发生塑性变形直至破坏;轻质土路基与老路基交接处易受老路基沉降变形与轻质土路基破坏变形的共同作用而产生弯剪破坏裂缝,最终导致路基失稳;该气泡轻质土路基受载-破坏模式是一个由内而外的从弹性变形到塑性屈服,最终发生弯剪破坏的过程,即先局部破坏再整体失稳;纵向上老路基的应力传递比轻质土路基小;一定荷载范围（小于100 kPa）内,路基变形程度与路基深度成反比。 相似文献
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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
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Eighty-four to ninety-eight percent of land subsidence in Shanghai City is caused by the visco-elastic–plastic deformation
of sediments. Numerical experiments are done on the sediments with visco-elastic–plastic deformation in Shanghai to verify
the modified Merchant model (MM model) and land subsidence model based on the modified Merchant (LS-MM) model. There are two
advantages of the MM model and the LS-MM model. One is that only a few parameters are involved. There are three parameters
in the MM model and four parameters in the LS-MM model. The other one is that both models can describe elastic, elastic–plastic
and visco-elastic deformation in addition to visco-elastic–plastic deformation. The corresponding models are developed by
setting proper values of the three parameters of μ, α
1 and α
2. The two advantages make the LS-MM model flexible and applicable to the simulation of the large regional land subsidence
with visco-elastic–plastic deformation and other different kinds of deformation. The results can be improved by variable parameters,
especially specific storage. 相似文献
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考虑基坑卸载影响的改进弹性抗力法及其应用 总被引：2，自引：1，他引：1
弹性抗力法是目前实际工程中基坑支护结构变形内力计算的一种主要方法,该方法借鉴的是计算水平荷载作用下竖直放置弹性桩的地基反力系数法,但没有考虑开挖卸载对土抗力系数和坑内土体的变形影响,因而导致变形计算值通常小于实测值。首先在开挖面施加反向自重应力模拟基坑的开挖卸荷,利用Mindlin解得到坑内土体的卸荷应力分布;在前人的实验研究基础上,推导了不同卸荷比下考虑卸荷影响的土体水平抗力系数;将支护结构的变形分解为开挖瞬时的卸载作用和基坑内外水土压力差作用2个阶段,考虑卸载应力路径对坑内土体水平抗力系数以及开挖瞬时变形的影响,对传统的弹性抗力法进行了改进,最后将该方法应用于典型三维基坑算例。研究发现,改进法得到的支护结构水平变形大于传统方法,而对内力结果影响不大;基坑平面尺寸越大,两者的变形结果差别越明显,改进法更能反映平面尺寸对基坑变形的影响 相似文献
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土体劈裂灌浆力学机理分析 总被引：8，自引：0，他引：8
为了在塑性力学和大变形理论的基础上分析土体在劈裂灌浆初始阶段的力学机理,将劈裂灌浆的初始阶段视为无限土体中的圆孔扩张问题,并将圆孔周围土体中的应力分布分为3个区域。在弹性区中土体服从小变形假设,在软化区和流动区中土体服从大变形假设。根据应力平衡方程以及应力和应变连续的边界条件,推导出劈裂灌浆初始阶段的最终扩孔压力和最终扩孔半径的理论解答。同时,还分析了灌浆压力、最终扩孔半径、土体的泊松比和大变形以及压缩模量之间的相互关系。该理论的计算结果与工程实测结果比较接近,初步证实了该理论的可靠性。 相似文献
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The mathematical structure and numerical analysis of classical small deformation elasto–plasticity is generally well established. However, development of large deformation elastic–plastic numerical formulation for dilatant, pressure sensitive material models is still a research area. In this paper we present development of the finite element formulation and implementation for large deformation, elastic–plastic analysis of geomaterials. Our developments are based on the multiplicative decomposition of the deformation gradient into elastic and plastic parts. A consistent linearization of the right deformation tensor together with the Newton method at the constitutive and global levels leads toward an efficient and robust numerical algorithm. The presented numerical formulation is capable of accurately modelling dilatant, pressure sensitive isotropic and anisotropic geomaterials subjected to large deformations. In particular, the formulation is capable of simulating the behaviour of geomaterials in which eigentriads of stress and strain do not coincide during the loading process. The algorithm is tested in conjunction with the novel hyperelasto–plastic model termed the B material model, which is a single surface (single yield surface, affine single ultimate surface and affine single potential surface) model for dilatant, pressure sensitive, hardening and softening geomaterials. It is specifically developed to model large deformation hyperelasto–plastic problems in geomechanics. We present an application of this formulation to numerical analysis of low confinement tests on cohesionless granular soil specimens recently performed in a SPACEHAB module aboard the Space Shuttle during the STS‐89 mission. We compare numerical modelling with test results and show the significance of added confinement by the thin hyperelastic latex membrane undergoing large stretching. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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A new constitutive model for fibre-reinforced cohesive soil is proposed. The model combines a Cam-Clay like bounding surface model with an elastic–plastic one-dimensional fibrous element model. A “smearing procedure”, which can consider any spatial distribution of fibre orientation, is employed to transform discrete tensile forces developed in the fibres into stresses for the composite material. The fibre stress contribution is bounded by both degradation of soil–fibre bonding due to pull-out mechanism and tensile strength of the fibres. Eventual occurrence of fibre breakage is also considered. The model performances are analysed for both consolidation and shearing loading modes, and qualitative comparison is performed with experimental data available in the literature. For consolidation loading, tensile stresses are not developed in the fibres and thus the fibre effect is rather limited. For drained shear loading, addition of fibres can result in a consistent shear strength increase. The beneficial effect of fibres seems to be controlled by two parameters: the fibre tensile stiffness and the fibre/soil strain ratio that accounts for any possible slippage or shear deformation at the fibre/soil matrix interface. For undrained shear loading, the strengthening effect of the fibres appears to be counteracted by the increase in pore water pressure, induced by the additional confining contribution of the fibres. In agreement with published experimental data, the model suggests also that the moisture content is a key factor governing fibre effectiveness for undrained shearing. Finally, analysis of the model predicted critical states for fibre-reinforced cohesive soil is provided. 相似文献
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控制隧道开挖引起的土体沉降变形是劈裂注浆的主要目的之一,隧道在劈裂注浆后复合土体的等效弹性参数取值直接关系着隧道在劈裂注浆后沉降变形的预测精度。首先在对已有劈裂扩散模型研究的基础上,按面积等效原则提出了隧道劈裂注浆后复合土体的二维简化等效单元体模型,并基于均质化理论按变形协调原则推导了二维简化单元体模型的等效弹性参数解析解。然后采用有限元方法分别计算并分析了模型在简化前后的等效弹性参数;同时把二维简化等效单元体模型的有限元计算结果和解析计算结果也做了对比分析。最后基于解析结果分析了土体和浆液结石体各自的弹性参数以及浆液注入率对等效弹性参数的影响。结果表明：（1）按面积等效原则对模型进行简化处理的方法是可行的,可以按照简化模型进行弹性阶段的理论分析;（2）解析结果与有限元结果具有良好的一致性,说明了解析结果的合理性;（3）复合土体的等效弹性模量和等效泊松比主要受浆液注入率和浆液固结体本身模量的影响;浆液固结体的泊松比对等效弹性模量的影响几乎可以忽略。 相似文献
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结构性粘土的堆砌体模型 总被引：68，自引：18，他引：50
天然粘土一般都具有结构性, 其变形过程必然伴随着结构的破坏。 提出了一种新型的堆砌体模型, 用以描述这种结构破坏现象。 这一模型把变形过程中的结构性土看作不同大小土块的集合体, 总的变形将由土块的弹性变形、土块之间滑动引起的塑性变形和土块破碎引起的损伤变形三部分组成。 塑性变形常用屈服函数描述, 损伤变形则可以引入一种类似的损伤函数加以描述。推导了相应的应力应变关系式并提出了模型参数的测定方法。 相似文献
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An analytical solution of cavity expansion in two different concentric regions of soil is developed and investigated in this paper. The cavity is embedded within a soil with finite radial dimension and surrounded by a second soil, which extends to infinity. Large‐strain quasi‐static expansion of both spherical and cylindrical cavities in elastic‐plastic soils is considered. A non‐associated Mohr–Coulomb yield criterion is used for both soils. Closed‐form solutions are derived, which provide the stress and strain fields during the expansion of the cavity from an initial to a final radius. The analytical solution is validated against finite element simulations, and the effect of varying geometric and material parameters is studied. The influence of the two different soils during cavity expansion is discussed by using pressure–expansion curves and by studying the development of plastic regions within the soils. The analytical method may be applied to various geotechnical problems, which involve aspects of soil layering, such as cone penetration test interpretation, ground‐freezing around shafts, tunnelling, and mining. © 2014 The Authors. International Journal for Numerical and Analytical Methods in Geomechanics published by John Wiley & Sons Ltd. 相似文献
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由于加荷方式不同,土体在复杂应力状态下在各主应力方向上应力-应变关系表现出显著应力各向异性,在常规三轴试验基础上,采用经典弹塑性理论各向同性土体模型对此不能合理描述。通过真三轴试验,总结应力各向异性柔度矩阵规律,结合试验规律进行相应理论研究,用非线性各向异性弹性矩阵代替弹塑性模型的弹性矩阵,用具有各向异性屈服准则的弹塑性模型描述塑性部分,建立非线性各向异性弹性-塑性模型,可以改善柔度矩阵矩阵形态,反映复杂应力状态下土体应力各向异性特征。 相似文献
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Sylvain Plumey Aurelio Muttoni Laurent Vulliet Vincent Labiouse 《国际地质力学数值与分析法杂志》2011,35(9):1019-1033
This paper investigates the load‐bearing capacity of a perfectly smooth retaining wall laterally supported at both ends assuming that the wall fails by the development of three plastic hinges. The study considers the case of a cohesionless elastic–perfectly plastic backfill with a Mohr–Coulomb yield criterion and an associative flow rule in drained conditions. A kinematically admissible soil–structure failure mechanism is proposed and compared with the conventional solutions and with results from a numerical finite element modelling. The study shows that the proposed solution and the numerical solution are in good agreement. These solutions are found to be much more favourable for the wall than the conventional solutions. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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基于将塑性上限分析等效为弹性迭代计算的总量虚拟加载上限分析理论,在商业化有限元软件ABAQUS中实现了弹性有限元虚拟加载上限方法（弹性有限元T-EMSD）。应用弹性有限元T-EMSD法分析了不排水黏土中的二维水平受荷桩,其获得的荷载-位移曲线与弹塑性有限元分析结果一致,其极限承载力与塑性解相近。在极限位移加载量下弹性有限元T-EMSD法对应的上限机构从弹性始速度场开始随迭代逐渐演化,迭代收敛后的速度场和解析塑性破坏机构相似。与其他基于可变强度概念（MSD）的方法相比,弹性有限元T-EMSD法对水平受荷桩桩身的分析具有更高的精度。弹性有限元T-EMSD法最大的优势在于可在计算中自然地获得塑性机构,因而可被用于研究一些塑性机构难以构造的复杂问题,并对弹塑性数值方法进行验证。 相似文献
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大理岩弹塑性耦合特性试验研究 总被引：6，自引：0，他引：6
大量研究表明,岩石经历塑性变形时其弹性参数会发生变化,即存在弹塑性耦合现象。为了研究岩石的弹塑性耦合特性,进行了两种大理岩的循环加、卸载试验。试验结果表明:与常规试验对比,循环加、卸载试验对岩石的变形、强度及破坏形态影响较小;弹性参数随塑性变形的变化显著,考虑弹塑性耦合时,弹性参数取体积模量和剪切模量更为合适;基于Mohr-Coulomb屈服准则,计算得到了强度参数,即黏聚力和内摩擦角随塑性内变量的演化规律。所得结论将为岩石弹塑性耦合本构模型的建立提供基本的试验支持。 相似文献