共查询到20条相似文献，搜索用时 578 毫秒
1.
Triaxial shear testing of polished slickensided surfaces 总被引：1，自引：1，他引：0
Christopher L. Meehan Binod Tiwari Thomas L. Brandon J. Michael Duncan 《Landslides》2011,8(4):449-458
A series of consolidated-drained triaxial tests were performed on precut and polished clay specimens to measure their drained
residual strength. Two soils were tested during this research program: Rancho Solano Clay and San Francisco Bay Mud. Specimens
were tested using a specially modified triaxial compression device which was developed to minimize the effects of end-platen
restraint on the measured strengths. Special attention was paid to the influence of changing specimen area and membrane effects
during the test. Triaxial test results were compared with baseline measurements of drained residual shear strength that were
made for each of the clay soils using Bromhead ring shear tests and polished-specimen direct shear tests. Residual strength
values measured in the triaxial device were higher than the drained residual strengths measured in the Bromhead ring shear
apparatus and the direct shear device, indicating that this test approach is more challenging than the use of direct shear
tests conducted on polished slickensided surfaces. Comparison of single stage and multistage triaxial test data indicates
that multistage triaxial testing may work well for specimens that fail along a well-defined plane, provided that careful attention
is given to the effects of end platen restraint, membrane restraint, and changes in specimen area during shear. 相似文献
2.
《Geomechanics and Geoengineering》2013,8(4):217-229
This paper describes the set-up, calibration and performance of the local instrumentation that measures the deformation response of the test-specimen in a new hollow cylinder apparatus (HCA). Customised, single- and double-axis inclinometers measure the axial and twist deformations of the outer specimen wall surface. Proximity transducers in the cell chamber and the specimen bore cavity measure the radial wall‐surface displacements and precision gearing allows the relocation of the transducers from outside the pressure-cell. The inclinometers were modified (reduced gauge of 45 mm) to suit the smaller-sized test specimen and the more compact pressure cell of the HCA. The instruments were calibrated using an optical table and laser distance-measurement system to achieve the necessary accuracy for strain measurements over the pseudo-elastic range. The calibration in water data for the proximity transducers was non-linear and strongly influenced by the specimen wall curvature. Equations are presented to compute the true torsional shear strain response from the measured inclinometer tilt angle, specimen dimensions and deformation response. External measurements include significant errors due to apparatus compliance, specimen end-restraint and bedding effects, inaccuracies in measuring volume changes and the fact that the deformations are calculated assuming that the entire specimen deforms as a right cylinder. 相似文献
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4.
堆石料三维边界面模型在FLAC3D中的开发与验证 总被引：1，自引：0，他引：1
堆石料三维边界面模型结合了统一非线性强度准则,可以反映三维应力空间堆石料的应变硬化、软化以及体积收缩和剪胀等传统本构模型难以反映的力学特性。基于三维边界面模型的基本理论,通过FLAC3D提供的二次开发平台,在VC++环境下实现了三维边界面本构模型的二次开发,并给出基于FLAC3D程序的边界面本构模型开发的关键步骤、编程要点和调试方法。利用开发的本构模型,开展了三轴压缩试验的数值模拟计算,并与理论值进行了对比分析。结果表明,嵌入在FLAC3D中的三维边界面本构模型能够较好地反映设定试验条件下的材料性能,而且三维边界面本构模型模型参数简单,都可从常规三轴试验获得,从而验证了三维边界面模型二次开发程序的优越性与合理性。 相似文献
5.
Wang Pengpeng Guo Xiaoxia Sang Yong Shao Longtan Yin Zenan Wang Yudi 《Acta Geotechnica》2020,15(10):2891-2904
Based on the three-dimensional digital image correlation (3D-DIC) technique, the stereovision system has been applied to the improved triaxial apparatus to obtain 3D full-field deformation of the specimen during triaxial testing. Through the calibration process, the 3D-DIC technique can obtain the accurate specimen’s spatial displacement deformation. Meanwhile, a subpixel edge detection algorithm has been combined with 3D-DIC technique to calculate the radial strain and the volume strain of the specimen directly. Furthermore, a series of consolidated drained and undrained triaxial tests were carried out on Hainan (China) sand specimens and measured by the conventional and the image measurement methods. Compared to the results measured by the conventional method, the image measurement technique can obtain the more experimental data, such as the 3D displacement field of the whole specimen, the local strain distribution, and so on. The measurement results also show the conventional method would be disturbed by the end constraints in triaxial tests so that the strength of the soil would be overestimated. Meanwhile, the middle of the specimen would be selected to calculate the stress–strain relationship without the influence of the end constraints in the proposed method. Based on the image measurement results, the proposed method has the potential to be used in geotechnical tests for exploring the soil’s progressive failure behaviors, inhomogeneous deformation and mechanical characteristics.
相似文献6.
In this paper an extension of existing multilaminate soil models is presented, which can account for inherent and stress‐induced cross‐anisotropic elasticity in the small strain range and its dependency on the load history. In the multilaminate framework, material behaviour is formulated on a number of local planes in each stress point, and the macroscopic response of the material is obtained by integration of the local contributions. Strain‐induced anisotropy, which adds to the stiffness anisotropy inherently present in the material, is therefore intrinsically taken into account. Micro–macro relations between local parameters on plane level and global parameters on macroscopic level are obtained by the spectral decomposition of the global elastic compliance matrix. The model is implemented into a finite‐element code, and model predictions are compared with experimental data of triaxial tests on different soils involving small and large load cycles. The importance of cross‐anisotropic elasticity within the small strain range for predicting ground deformations in geotechnical boundary value problems is discussed at the example of an excavation problem. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
7.
土石坝所处的应力状态较接近平面应变应力状态或三维应力状态,而常规三轴试验低估了粗粒料的力学性能。应用大型真三轴仪对常规三轴应力状态、平面应变应力状态和真三轴应力状态（ 0.25, 为中主应力系数, 、 、 分别为大、中、小主应力）下粗粒料的力学特性进行了压缩试验研究。试验结果表明：相同小主应力下,常规三轴试验、平面应变试验、真三轴试验的大、小主应力之差与大主应力方向应变的关系曲线依次变高变陡。某一试验加载条件下,体应变随球应力的增大而增大,初始剪切阶段增加较慢,随后呈线性增大,不同小主应力的体应变曲线较为接近。平面应变试验强度和真三轴试验强度比常规三轴试验强度有较大增长,真三轴试验强度增加百分比大于平面应变试验强度增加百分比。初始弹性模量随小主应力的增大呈线性增大。平面应变状态下中主应力系数随大主应力方向应变的增大而增大,初始剪切阶段增长较缓,之后近似呈线性增大。相同小主应力下,从常规三轴应力状态至平面应变应力状态再到真三轴应力状态,小主应力方向应变均为膨胀变形,且膨胀变形依次增大。同一试验加载条件下,小主应力较小时,应力比（偏应力与球应力之比）与偏应变的关系曲线位于上方。 相似文献
8.
采用大型高压多功能静动三轴试验机,对某面板堆石坝闪长岩类堆石料进行了动弹性模量与阻尼比试验和动残余变形试验,研究了主堆石料、过渡料和垫层料3种坝料在循环荷载下的动应力-应变特性和动残余变形特性及其主要影响因素。试验结果表明,材料的动应力-应变关系受剪应变水平的影响较大,各种材料的动弹性模量随剪应变的增加发生衰减,而阻尼比则相应增大;围压的增加引起材料的最大动弹性模量的增加,但围压力对材料动弹模增长的影响是有限的;固结主应力比的增大,会引起有效球应力的增加,从而使材料的最大动弹性模量增大。此外,从试验结果和模型参数来看,各种材料的动应力-动应变变化规律以及动变形随振次的发展规律均可以用修正等价黏弹性模型和沈珠江残余变形经验公式进行描述 相似文献
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10.
Implementation of a coupled plastic damage distinct lattice spring model for dynamic crack propagation in geomaterials 
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下载免费PDF全文 This paper studies dynamic crack propagation by employing the distinct lattice spring model (DLSM) and 3‐dimensional (3D) printing technique. A damage‐plasticity model was developed and implemented in a 2D DLSM. Applicability of the damage‐plasticity DLSM was verified against analytical elastic solutions and experimental results for crack propagation. As a physical analogy, dynamic fracturing tests were conducted on 3D printed specimens using the split Hopkinson pressure bar. The dynamic stress intensity factors were recorded, and crack paths were captured by a high‐speed camera. A parametric study was conducted to find the influences of the parameters on cracking behaviors, including initial and peak fracture toughness, crack speed, and crack patterns. Finally, selection of parameters for the damage‐plasticity model was determined through the comparison of numerical predictions and the experimentally observed cracking features. 相似文献
11.
This paper presents an elasto‐plastic model for unsaturated compacted soils and experimental results obtained from a series of suction‐controlled triaxial tests on unsaturated compacted clay with different initial densities. The initial density dependency of the compacted soil behaviour is modelled by establishing experimental relationships between the initial density and the corresponding yield stress and thereby between the initial density and the location and slope of normal compression line. The model is generalized to three‐dimensional stress states by assuming that the shapes of the failure surface and the yield surface in the deviatoric plane are given by the extended SMP criterion. A considerable number of the isotropic compression, triaxial compression and extension tests on unsaturated compacted clay with different initial densities were performed using a suction‐controllable triaxial apparatus, to measure the stress–strain–volume change in different stress paths and wetting paths. The model has well‐predicting capabilities to reproduce the mechanical behaviour of specimens compacted under different conditions not only in isotropic compression but also in triaxial compression and triaxial extension. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
12.
为研究温度和湿度对生土力学特性的影响,自主研发了温、湿控制生土三轴试验装置。基于常规三轴压力室,借助电涡流非接触位移传感器搭建高精度变形测试系统,实现环境变化下生土应变的连续性捕捉。针对法国里昂地区生土材料,开展不同湿度、围压和温度作用下生土三轴循环加载-卸载试验,实测生土在不同工况下的三轴剪切破坏强度、应力-应变曲线及体积变化,通过分析滞回曲线,研究弹性模量和残余应变随应力水平的演化特征;同时进行了变湿度条件下生土气态水迁移效应试验。结果表明：该装置能够稳定控制生土环境变化条件,模拟再现生土单元体实际服役工况,精确测量试验过程中生土力学指标及湿度、温度与压力等环境指标,初步检验了装置性能的可靠性和准确性。相关成果可为荷载-湿-热耦合作用下非饱和生土变形机制的研究与本构模型的建立提供技术支撑。 相似文献
13.
Numerous constitutive models built on coaxial theory and validated under axi‐symmetric condition often describe the stress–stain relationships and predict the inceptions of shear banding in sands inaccurately under true triaxial condition. By adopting an elaborated Mohr–Coulomb yield function and using non‐coaxial non‐associated flow rule, a 3D non‐coaxial elasto‐plasticity model is proposed and validated by a series of true triaxial tests on loose sands. The bifurcation analysis of true triaxial tests on dense sands predicts the influence of the intermediate principal stress ratio on the onset of shear band accurately. The failure of soils is shown to be related to the formation of shear band under most intermediate principal stress ratio conditions except for those which are close to the axi‐symmetric compression condition. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
14.
Model identification and parameter estimation of elastoplastic constitutive model by data assimilation using the particle filter 下载免费PDF全文
下载免费PDF全文 Data assimilation, using the particle filter and incorporating the soil‐water coupled finite element method, is applied to identify the yield function of the elastoplastic constitutive model and corresponding parameters based on the sequential measurements of hypothetical soil tests and an actual construction sequence. In the proposed framework of the inverse analysis, the unknowns are both the particular parameter within the exponential contractancy model, nE, which parameterizes various shapes for the yield function of the competing constitutive models, including the original/the modified Cam‐Clay models and in‐between models and the parameters of the corresponding constitutive model. An appropriate set, consisting of the yield function of the constitutive model and the parameters of the constitutive model, can be simultaneously identified by the particle filter to describe the most suitable soil behavior. To examine the validity of the proposed procedure, hypothetical and actual measurements for the displacements of a soil specimen were obtained for consolidated and undrained tests through a synthetic FEM computation and for consolidated and drained tests, respectively. After examining the applicability of the proposed procedure to these test results, the present paper then focuses on the actual measured data, ie, the settlement behavior including the lateral deformation of the Kobe Airport Island constructed on reclaimed land. 相似文献
15.
真三轴试验中的端部摩擦效应分析 总被引：3，自引：0，他引：3
端部摩擦效应是三轴试验的常见问题之一。相对于常规三轴试验,由于在茂木式真三轴试验中方形试样4个端部需设置两对端部垫块,从而导致端部摩擦问题更加突出。运用FLAC3D,针对Mohr-Coulomb材料,即无中间主应力影响材料,模拟真三轴加载过程中端部摩擦对试样强度和变形行为的影响。计算结果表明,端部摩擦也可以产生虚假中间主应力效应,即使对于无中间主应力效应材料,中间主应力也会导致最大破坏主应力的增加,且摩擦系数越大,这种趋势则越明显。分析了端部摩擦产生这种趋势的原因,指出了真三轴试验中减小端部摩擦的重要性。 相似文献
16.
Characterisation of confinement effect on jointed rock pillars using a Synthetic Rock Mass approach 下载免费PDF全文
下载免费PDF全文 Confinement effect on jointed rock pillars is numerically characterised in this research using a Synthetic Rock Mass (SRM) approach. The SRM is an integrated model incorporating a discrete fracture network within a Particle Flow Code 3D particle assembly. In this paper, the confinement effect on a 3D jointed pillar SRM model is investigated in a series of simulations, including biaxial compression tests and true and conventional triaxial compression tests. The numerical results suggest that the applied confining stresses generally result in higher pillar strengths and ductile post‐peak responses. More brittle post‐peak behaviour is simulated in the biaxial and true triaxial tests when the pillar is confined by a high stress in one lateral direction and by a zero/low stress in the other lateral direction. This phenomenon is attributed to significant lateral pillar dilation in the less confined direction. Detailed pillar failure modes are monitored in the uniaxial and triaxial tests. Axial splitting fractures and long shear zones cutting through the pillar are simulated when the pillar is able to dilate in the direction of least confinement. Localised shearing along joints and failed rock blocks is the dominant failure mode when the pillar dilation is resisted by the applied confining stresses. The pillar remains relatively intact with limited cracking in the pillar core in the highly confined triaxial tests. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
17.
Yu Haizhen Zhao Wenguang Wang Ren Li Jianguo He Yang 《中国地质大学学报(英文版)》2005,16(4):340-344
INTRODUCTION Theexploitationofoffshorenaturalresourcesin thetropichaspresentedgeotechnicalengineerswith theproblemofdealingwithinsitucarbonatesedi mentsinharshconditionsforwhichfewengineering dataareavailable.Thecarbonatesedimentsaresub jectedtolargestaticstressesduetotheweightof foundationstructuresaswellascyclicstressesdueto waveaction,andinsomecases,earthquakeloading.Ithasbeenprovedthatthenatureofcyclicstresschangesoccurringintheseabeddepositduetowave loadinginvolvesacontinuousrotationo… 相似文献
18.
This paper presents a three‐dimensional elastoplastic constitutive model for predicting the hydraulic and mechanical behaviour of unsaturated soils. It is based on experimental results obtained from a series of controlled‐suction triaxial tests on unsaturated compacted clay with different initial densities. Hydraulic hysteresis in the water‐retention behaviour is modelled as an elastoplastic process, with the elastic part modelled by a series of scanning curves and the elastoplastic part modelled by the main drying and wetting curves. The effect of void ratio on the water‐retention behaviour is studied using data obtained from controlled‐suction wetting–drying cyclic tests on unsaturated compacted clay with different initial densities. The effect of the degree of saturation on the stress–strain‐strength behaviour and the effect of void ratio on the water‐retention behaviour are considered in the model, as is the effect of suction on the hydraulic and mechanical behaviour. The initial density dependency of the compacted soil behaviour is modelled by experimental relationships between the initial density and the corresponding yield stress and, thereby, between the initial density and the normal compression line. The model is generalized to three‐dimensional stress states by assuming that the shapes of the failure and yield surfaces in the deviatoric stress plane are given by the Matsuoka–Nakai criterion. Model predictions of the stress–strain and water‐retention behaviour are compared with those obtained from triaxial tests with different initial densities under isotropic compression, triaxial compression and triaxial extension, with or without variation in suction. The comparisons indicate that the model accurately predicts the hydraulic and mechanical behaviour of unsaturated compacted soils with different initial densities using the same material constant. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
19.
利用FLAC3D程序提供的二次开发平台UDM在VC++编译环境下实现了一基于修正剑桥模型的简化边界面模型的开发。介绍了边界面模型的基本原理,并给出了开发关键技术和具体实施方法。通过三轴加卸载试验、不排水静三轴试验、不排水动三轴试验等几种数值试验与修正剑桥模型进行了对比研究。计算结果验证了所开发的边界面模型的正确性及相对修正剑桥模型的优越性。 相似文献
20.
断层相关褶皱的三维构造几何学分析:以川西三维地震工区为例 总被引：1，自引：0，他引：1
现有的断层相关褶皱理论均基于平衡剖面原理而建立的二维几何学模型。所谓的假三维模型则是通过一系列的二维剖面复合而成的,真正意义上的三维断层相关褶皱理论尚未确立,仍然处于探索阶段。本文采用Trishear 4.0和GoCad软件,分别构建一系列不同位移量的断层转折褶皱和三剪断层传播褶皱的二维正演剖面,将这些正演剖面按照一定的线性位移梯度平行排列,从而建立起断层转折褶皱和三剪断层传播褶皱的假三维理论模型并加以分析和讨论。进而选取川西南盆地中三维地震勘探所覆盖的邛西断层转折褶皱和盐井沟断层传播褶皱,作为真三维实际解释模型的两个实例。研究表明,邛西背斜是一个典型的剪切断层转折褶皱,盐井沟背斜是一个典型的三剪断层传播褶皱;断层相关褶皱的假三维理论模型与实际解释模型的对比分析,可以看出沿背斜走向的位移梯度是控制三维构造几何学特征的基本因素,然而自然界断层面几何学的复杂多变以及岩层力学性质的各向异性,是造成断层相关褶皱真三维理论模型难以建立的主要原因。 相似文献