基于颗粒物质热动力学理论的非饱和土热水力耦合模型研究

基于颗粒物质热动力学理论和混合物理论,结合改进的土水特征曲线(SWCC)模型,考虑温度和饱和度变化引发的颗粒层次能量耗散,提出了一个非饱和土的热水力耦合模型。该模型引入颗粒熵和颗粒温度的概念,通过构建热力学恒等式得出非饱和土非弹性变形的本构关系,并通过迁移系数和能量函数模型将非饱和土体的耗散机制与宏观的物理力学行为建立联系。基于该理论模型,研究了非饱和土的热水力耦合问题,通过模拟结果与试验数据的对比,证实了模型的有效性。模拟结果表明,模型具有描述非饱和土在不同温度和吸力下的固结和剪切特性以及非等温条件下的热体应变特性的能力。     

基于能量耗散的煤岩三轴受压损伤演化特征研究

在煤矿资源的地下开采工程活动中,煤岩处于轴压、围压和瓦斯气体相互耦合的复杂应力环境。为探究煤岩受压过程中的损伤变形及能量演化特征,利用含瓦斯煤热–流–固耦合三轴伺服渗流试验装置,开展煤岩在不同围压及不同瓦斯压力条件下的三轴压缩试验研究。基于连续损伤力学理论,从能量角度理论推导由非均质威布尔函数、能量耗散函数及塑性应变函数构成的损伤应力–应变函数,并在此基础上建立基于能量耗散的煤岩损伤本构模型。研究结果表明:(1)不同围压、不同瓦斯压力下煤岩应力–应变变化趋势及塑性变形行为具有阶段性特征。(2)对应不同的变形破坏阶段煤岩的能量演化趋势呈阶段性变化,应力峰值点处煤岩吸收的总能量随围压的增大而增大,弹性能及耗散能也呈现增大的趋势;随着瓦斯压力的上升,煤岩吸收的总能量和弹性能在应力峰值点处呈下降趋势,耗散能呈上升趋势。(3)构建围压及瓦斯压力效应下基于能量耗散的煤岩损伤本构模型,并通过试验验证该模型具有较好的合理性。(4)不同围压及瓦斯压力下煤岩能量耗散与损伤演化均呈"S"型演化趋势。     

《岩石力学与工程学报》2004年第19期被EI收录论文（22篇）

No.论文题目作者名页码1考虑剪胀及软化的洞室围岩弹塑性分析的统一解范文俞茂宏陈立伟等3213–32202准脆性材料的弹塑性损伤耦合模型崔崧黄宝宗张凤鹏3221–32253基于Weibull分布的岩石损伤软化模型及其修正方法研究曹文贵赵明华刘成学3226–32314一种简化的混凝土损伤本构模型及其应用彭向和杨春和万玲3232–32395FSD耦合模型在多孔水压致裂试验中的应用李连崇唐春安杨天鸿等3240–32446材料应变局部化分析中不同内尺度律参数间相互作用问题的讨论张洪武张盛秦建敏3245–32517使用离散的气-水界面模拟裂隙网络非饱和渗流宋晓晨徐卫亚邵…     

非饱和土热–水–力全耦合本构模型及其验证

在地热资源开发与利用、核废料地质处理、垃圾填埋场等诸多岩土工程领域都需要考虑温度对非饱和土性质的影响。为了更为全面描述非饱和土在热–水–力耦合条件下的变形及持水特性,以平均土骨架应力、修正吸力和温度为应力变量,以比体积和饱和度为应变变量,建立了一个非饱和土热–水–力全耦合本构模型。模型通过屈服面方程及屈服面之间的耦合规律来反映热–水–力之间的相互影响,主要包含温度和饱和度对力学特性的影响,吸力和超固结比(应力历史)对热变形的影响,密度、温度和滞回效应对持水特性的影响,温度、应力和滞回效应对干化及湿化变形的影响。利用建立的模型,对不同应力路径下的试验进行预测。通过预测与试验结果的对比,验证了模型的适用性。     

基于三维热力场耦合分析的换流变压器网侧干式套管拉杆连接结构力学计算及优化设计

换流变压器网侧套管在换流站系统运行中承担着关键作用，但在实际运行中其拉杆连接结构多次发生如拉杆断裂、拉杆与载流端子松脱等故障。本研究针对某出现故障的550 kV换流变网侧干式套管，采用三维电磁-热-流场耦合分析方法及热力场耦合分析方法，建立了套管及拉杆连接结构精细化模型，考虑了热传导、热对流、热辐射等条件，计算了网侧套管温度场及应力应变场分布。结果表明：换流变网侧干式套管的拉杆连接系统附近温度较高，拉杆表面大部分区域受到较大应力作用，拉杆与载流端子插接处应力极大，在工况反复热胀冷缩及换流变压器振动等因素的共同作用下可能导致拉杆与载流端子插接处脱开，电气连接失效。同时提出了采用导杆式插接结构替换拉杆连接系统的优化设计方案，通过仿真分析验证了导杆式套管温度分布及应力应变分布满足安全稳定运行的热裕度和机械裕度，为后续生产试验提供依据。     

冲击荷载下复合岩体动力响应力学特性及本构模型研究

为研究工程中冲击作用下不同复合岩体的动力响应差异，采用分离式霍普金森压杆(SHPB)试验系统和数字图像相关系统(DIC)，对煤–岩和岩–煤2种复合岩体进行不同应变率下的动态冲击试验，对比动力冲击后2种复合岩体的应力波传播特征、动态强度、能量耗散、破碎分形特征以及破坏模式。并建立考虑复合煤–岩特性的本构模型。试验和理论分析结果表明：在相同应变率条件下，2种复合岩体的入射能基本一致，由于应力波传播过程中冲击杆与岩–煤的波阻抗匹配优于煤–岩体，在应变率较小时岩–煤体的动态强度、耗散能明显大于煤–岩体，随着应变率的增加二者差别逐渐减小；复合岩体耗散能越大其破碎块度分形维数越大，表现出明显的线性相关；不同复合岩体在冲击作用下的破坏主要集中在煤体侧，且以劈裂破坏为主，受界面效应的影响，煤体侧裂纹会发育至岩体侧，从而发生贯通破坏。基于元件组合建立考虑应变率效应和损伤演化的本构模型，其结果与试验结果吻合较好，验证了构建模型的正确性。     

纯主应力旋转条件下饱和黏土累积变形的热力学模型分析

不同于岩土弹塑性模型和经验回归模型,提供了一个基于颗粒固体流体动力学的热力学本构模型。该模型通过对岩土颗粒固体的弹性弛豫和颗粒熵运动等耗散机制的定量描述,可以模拟土体的非线性硬化、软化等宏观力学行为,尤其适用于主应力旋转土体累积塑性应变的模拟。纯主应力旋转条件下杭州黏土的模拟结果表明:即使不改变土体的主应力大小,纯主应力方向的旋转依然会引起土体的非弹性变形的积累。在主应力旋转过程中,土体的应变方向与应力方向并不一致,存在明显的非共轴现象。并且应变峰值的出现明显落后于应力峰值,应力–应变关系曲线存在较大的滞回圈,表明纯主应力旋转过程中也存在能量耗散,并非完全弹性过程。模型分析结果符合现有的试验结论。     

饱和土体圆柱形热源热固结问题的一个近似解

在考虑土骨架和孔隙水热膨胀特性差异的基础上,根据力平衡条件、有效应力原理、能量守衡定理及线弹性应力–应变关系,建立了考虑耦合效应的饱和土体热固结问题控制方程。利用 Fourier 变换、Laplace 变换及其逆变换,给出了热固结问题的求解方法。对一无限长圆柱形热源向外传导和扩散问题进行研究,给出了非等温条件下周围饱和土体的温度、孔隙水压力和位移的解析解,并对其变化规律进行研究,分析了热固结系数等参数的影响。     

热-力作用下隧道岩爆温度效应的物理模型试验

随着西部大开发战略的深入实施,重大工程建设中遇到越来越多的高地温和高地应力隧道。为了研究这类隧道工程在高地温和高地应力耦合作用下发生岩爆的特性,通过一系列技术研发,在二维地质力学模拟试验加载系统上成功进行热–力作用下隧道岩爆温度效应的物理模型试验。在研制具有岩爆倾向的硬脆性岩爆相似材料基础上,自主开发大型物理模型温度场加载系统和隧道开挖装置,考虑20℃,40℃,60℃,80℃四种温度和侧压力系数为2的高地应力作用,共开展4个模型试验。试验研究结果表明,在20℃~80℃温度范围,温度增大提高了材料的硬脆性,围岩能积聚更高弹性应变能,温度应力引起的洞壁切向应力以及应力差增大,为岩爆创造了更有利的条件。模型温度越高,围岩破坏前变形越小,模型破裂过程中释放的能量越大,破裂源越多;随着温度增高,围岩脆性破坏更强烈且更突然,渐进过程越不明显,岩爆剥落弹射的块径更大。因此,在热力耦合作用下隧道岩爆表现出在一定温度范围内随着温度增大而更加强烈的规律。     

瑞典spAPSE岩柱热弹性耦合特性与数值模拟

瑞典s p硬岩地下实验室开展的APSE试验的主要目的在于分析岩柱在开挖及加热过程中的力学响应及渐进破坏过程,其岩柱热–力耦合特性的数值模拟研究是国际合作研究计划DECOVALEX-2011项目的3大研究课题之一。采用热弹性耦合模型研究了APSE岩柱在开挖及加热过程中的应力、变形及温度变化规律,表明热弹性耦合模型对完整致密岩体的热-力耦合特性具有较好的描述能力,计算结果总体上反映了岩柱在开挖及加热过程中的应力调整和温度变化特征,并可对岩柱壁面的破坏特征及扩展规律进行定性解释。但因缺乏对岩体中多相流运动过程和渐进破坏过程的描述能力,热弹性耦合模型也表现出较大的局限性。研究成果对中国北山预选区核废料硬岩储库围岩的稳定性评价具有一定的参考意义。     

Evaluation of strengthening through stress relaxation testing of organo-modified montmorillonite reinforced cement mortars

It is demonstrated that the addition of organo-modified montmorillonite (OMMT) particles to cement mortars can enhance their microstructure as well as mechanical properties. A series of static compression and stress relaxation tests on cement mortars reinforced with various dosages of OMMT particles under different temperatures and imposed strains were conducted. The consistency of the test results, including pore size distributions obtained from mercury intrusion porosimetry measurements and activation energies determined from stress relaxation tests, reinforces the positive effects observed on the initial elastic modulus, compressive strength and strain exponent of cement mortars. It appears that an important step has been achieved in assessing the benefits of using organo-clays in concrete. Accordingly, the adequate dosage of OMMT particles introduced in cement mortars to give a higher elastic modulus, compressive strength and activation energy of stress relaxation is proposed here.     

岩石热黏弹塑性模型研究

 温度作用下岩石的本构行为研究对于深部资源开采、核废料地下处置、地热资源开发以及地下军事防护设施建设等岩石工程问题具有重要意义。以西原体模型为基础,引入热膨胀系数、黏性衰减系数和损伤变量,综合考虑温度对岩石弹性变形、黏性流动以及结构损伤的共同影响,建立岩石热黏弹塑性本构模型,推导考虑温度效应的岩石蠕变方程和卸载方程。研究结果表明,在应力低于屈服极限的情况下,模型初始变形较快,然后趋于稳定蠕变,卸载曲线存在瞬时弹性变形、弹性后效和由温度引起的黏性流动;在应力高于屈服极限的情况下,变形逐渐转化为不稳定蠕变,卸载曲线存在瞬时弹性变形、弹性后效和由温度和应力共同引起的黏性流动。该模型较全面反映了岩石在温度作用下的黏弹塑性和损伤性质,适用于温度和载荷作用下岩石流变与稳定性分析。     

A 3-D study of the effects of thermomechanical loads on fracture slip in enhanced geothermal reservoirs

Heat extraction from enhanced geothermal systems (EGS) can greatly affect the behavior of joints and other discontinuities in the reservoir. Fracture permeability can change in response to fluid injection/extraction, rock cooling, variations of stress field, and mineral dissolution/precipitation. The reduction in effective stress caused by pore pressure increase can cause the slippage of discontinuities, thus inducing seismicity. Studies have shown that thermal stresses generated by cold water injection have a similar effect. In order to assess the influence of thermal stresses on fracture opening and slippage, a 3-D coupled heat extraction/thermal stress/elastic displacement discontinuity model is used in this study. The effects of each mechanism on fracture slip is estimated with particular reference to the Coso geothermal field. The results indicate that under typical field conditions, a substantial increase in fracture slip is observed when thermal stresses are taken into account. The temporal evolution of the thermal stresses suggests that the rock mass deformation will not cease upon stoppage of water injection, which can be a cause of delayed seismic activity.     

沥青混凝土温度应力试验及其数值模拟

沥青混凝土路面的低温开裂问题一直是道路工程界人士研究的一个热点问题 ,美国SHRP在综合分析了以前各种用于分析、研究沥青混凝土低温开裂问题的试验方法后 ,认为只有约束试件温度应力试验 (TSRST)能正确的模拟路面的现场情况 ,提出采用约束试件温度应力试验 (TSRST)来研究沥青路面的低温开裂问题 ,并对相应的试验标准 ,试验数据的分析、处理等都提出一整套方法。笔者在采用TSRST进行大量试验的基础上 ,指出SHRP提出的温度应力典型曲线的不足 ,提出了完整的温度应力曲线规律。然后探讨了初始温度度和降温速率等对温度应力的影响以及不同材料的低温抗裂性能。最后在分析已有的温度应力计算方法的基础上 ,提出考虑沥青混合料在连续降温过程中的应力松弛效应的温度应力计算方法 ,运用该方法对TSRST试验过程进行了数值模似 ,模拟结果表明所提出的计算沥青混合料在连续变温过程中的温度应力的计算方法是正确的。     

Strain Energy-Based Elasto-Viscoplastic Constitutive Modelling of Sand for Numerical Simulation

It is shown that the use of visco-plastic shear or volumetric strain as the stress history-independent hardening parameter in an elasto-viscoplastic model for sand may result in inaccurate numerical simulations of geotechnical boundary value problems. A new elasto-viscoplastic constitutive model for sand is proposed, formulated based on a stress path-independent irreversible (or visco-plastic) strain energy-based hardening function. The function was derived based on results from drained plane strain compression (PSC) tests on saturated dense Toyoura sand along a wide variety of stress path. The model is coupled with an existing isotropically work-hardening and -softening, non-associated, elasto-plastic model for sand. The constitutive model takes into account the effects of loading rate due to viscous properties on the stress-strain behaviour as well as those of pressure level, inherent anisotropy and void ratio and work softening associated with strain localization into a shear band. It is shown that the proposed model can much better simulate the effects of stress history on the deformation characteristics of sand than many previous models. The FEM code incorporating the model is validated by simulating physical PSC tests and bearing capacity model tests of a strip footing on sand performed by previous studies.     

Modelling fracture propagation and failure in a rock pillar under mechanical and thermal loadings

The spPillar Stability Experiment (APSE) was conducted to study the rock mass response in a heated rock pillar between two large boreholes. This paper summarizes the back calculations of the APSE using a two-dimensional (2D) fracture propagation code FRACOD. To be able to model all the loading phases of the APSE, including the thermal loading, the code was improved in several ways. A sequential excavation function was developed to model promptly the stepwise changing loading geometry. Prior to the mod-elling, short-term compressive strength test models were set up aiming to reproduce the stress-strain behaviour observed for the sp diorite in laboratory. These models simulate both the axial and lateral strains of radial-controlled laboratory tests. The volumetric strain was calculated from the simulations and compared with the laboratory results. The pillar models include vertical and horizontal 2D models from where the stress in the pillar wall was investigated. The vertical model assesses the stability of the experimental rock volume and suggests the resultant stress below the tunnel floor in the pillar area. The horizontal model considers cross-sections of the pillar between the two large boreholes. The horizontal model is used to simulate the evolution of the stress in the rock mass during the excavation of the boreholes and during and the heating phase to give an estimation of the spalling strength. The modelling results suggest that the excavation-induced stresses will cause slight fracturing in the pillar walls, if the strength of the APSE pillar is set to about 123 MPa. Fracture propagation driven by thermal loading leads to minor spalling. The thermal evolution, elastic behaviour and brittle failure observed in the experiment are well reflected by the models.     

Influence of anisotropic stress states on the thermal volume change of unsaturated silt

This study is focused on understanding the influence of anisotropic stress states on the thermal volume change of unsaturated, compacted silt specimens. A thermo-hydro-mechanical true-triaxial cell was used that permits control of the temperature on all six boundaries of a cubical soil specimen as well as control of the suction within the specimen to provide drained conditions during mechanical loading and temperature changes. Six non-isothermal tests were performed as part of this study, each involving suction application, consolidation to a given isotropic or anisotropic stress state, heating and cooling in stages under drained conditions, and unloading. Specifically, tests having minor to major principal stress ratios of 1.0, 0.7, and 0.5 were performed on specimens having initial degrees of saturation of 0.7 and 0.8, complementing tests on the same soil under similar stress states but saturated conditions published in a previous study. Although compressive thermal axial strains were measured in both the major and minor stress directions, a greater thermal axial strain was observed in the direction of the major principal stress for stress ratios less than 1.0. However, similar thermal volumetric strains were observed in all of the tests regardless of the stress state. A small effect of inherent anisotropy was observed due to the formation of the specimens using compaction. Specimens with a lower initial degree of saturation experienced greater thermal volume changes than specimens closer to saturation, possibly due to thermal collapse of the air-filled voids during heating or thermally accelerated creep after application of a given plastic strain during mechanical loading. An empirical relationship to consider the effects of anisotropic stress states and variable saturation was incorporated into an established elasto-plastic model developed for saturated soils under isotropic conditions, and a good fit was obtained between the measurements and predictions.     

基于下加载面概念的饱和黏土温度–应力耦合弹塑性模型

温度对黏土力学特性具有重要影响,温度变化将引起黏土的体积变形发生变化,并对其前期固结应力、剪切强度、弹性模量等具有重要影响。基于黏土"热陷"特性,引入热屈服面以描述不同超固结比的黏土在温度升高时所产生的塑性变形,并进一步开展以下工作:(1)建立考虑温度影响的下加载面模型,由于保留了下加载面模型对超固结黏土应力–应变特性优异的描述能力,并考虑了温度对黏土的2种作用(即温度使超固结黏土的超固结比降低和温度塑性应变对屈服面的硬化效应),该模型可以描述温度变化对不同黏土力学特性的复杂影响;(2)证明了所提出的模型严格满足热力学第一、第二定律;(3)采用该模型模拟Pontida clay和MC clay在不同压力下的排水加热试验和在不同温度下的三轴排水/不排水试验,模拟结果与试验结果对比分析表明,模型能合理地描述不同超固结比的黏土在温度变化时产生的体积变形以及温度对黏土强度的影响等。     

A hybridized displacement discontinuity method for mixed mode I–II–III loading

A new hybridized displacement discontinuity numerical method is presented. The existing code FROCK is modified to incorporate loading mode III, and thus have a fully coupled solution for mixed mode I–II–III loading. The new code can be applied to homogeneous elastic bodies with small scale yielding and to cracks where one of the dimensions is much larger than the other two. The code combines both displacement discontinuity (DD) and stress discontinuity (SD) elements. DD elements are characterized by a jump of the displacement field across the element, while SD elements show a stress jump. DDEs are very well suited to model cracks inside of a body, and SDEs for the boundaries of the body. A new set of DDEs and SDEs is developed which incorporate mode III loading. For open elements, loading modes I and II are coupled, but they are independent of mode III. For closed elements, friction may develop along the surface of the elements. Friction depends on the normal stress and on the shearing (mode II) and tearing (mode III) stresses, and thus the solution is fully coupled. Hence the problem is non-linear and iterations are needed to achieve convergence. The new code FROCK is verified by a number of comparisons with analytical solutions and with other numerical methods. A new analytical solution to obtain stress intensity factors for closed cracks in mode II–III is also presented and validated.     

基于扰动状态概念硬化参量的结构性黏土边界面模型

在临界状态理论和边界面模型的框架内,引入结构性扰动对弹性变形、结构性屈服面大小、胶结吸力和屈服面各向异性的影响,建立一个基于扰动状态概念硬化参量的结构性黏土边界面模型。首先,通过定义3个结构扰动度R_c,R_b和R_a来定量反映塑性变形对结构性黏土的结构性屈服面、胶结吸力和屈服面各向异性的扰动程度,并对弹性特性进行各向异性和结构性影响的修正。然后,通过对天然沉积上海黏土和Vallericca硬黏土的三轴不排水剪切试验和一维固结压缩试验的模拟验证模型的预测能力。最后,通过模型与有限差分法相结合,以简单的平面应变试验模拟为例,展示模型能够描述结构扰动度的变化及其在土体中分布的模拟能力。