岩石化学腐蚀-围压细观损伤本构模型与离散元模拟研究

基于Lemaitre应变等价性假设理论,假定受水化学-力耦合损伤的岩石微元强度服从Weibull分布,考虑化学腐蚀与围压耦合作用对岩石力学参数的影响,通过核磁共振技术与损伤力学理论,引入细观化学损伤变量与力损伤变量,并认为微元破坏符合SMP准则,建立岩石化学腐蚀-力耦合损伤本构模型,并采用理论推导的方法得出所需的模型参数。同时基于颗粒离散元方法,引入参数半径乘子来改变颗粒间的黏结接触尺寸,从而模拟水化学损伤,采用平直节理模型对水化学作用后的岩石进行三轴压缩模拟,得到了水化学作用和不同围压下的岩石三轴应力-应变模拟曲线。通过对比所构建的岩石化学腐蚀-力耦合损伤本构模型理论曲线、离散元模拟曲线和试验曲线,结果表明三者吻合度较好,能够很好地反映岩石在化学腐蚀和围压耦合作用下的力学特性与破坏特征,并通过离散元方法得到了岩石在三轴压缩过程中裂纹的产生与分布情况。     

含能材料三轴动态压缩实验的一个计算机模拟方法

在含能材料单轴、受限三轴动态压缩实验的基础上，提出一种将计算机数值模拟和实验数据相结合，估算实验系统中钢筒与试件间的库伦摩擦力，从而正确确定含能材料的动态三轴力学性能（弹性模量Ｅ，泊桑比ν，屈服限Ｙ等）的方法。本方法用于ＴＮＴ炸药受限三轴动态压缩实验，通过建立钢筒－试件的库伦摩擦有限元模型，采用ＡＤＩＮＡ通用程序进行动力分析，估算了摩擦力对实验数据的影响，获得了考虑摩擦力修正后的ＴＮＴ三轴动态压缩响应，为含能材料三轴动态力学性能的确定提供了一种有效的方法。     

含初始损伤岩石的冻融损伤试验研究

在实际工程中,岩石大多是含初始损伤的,分析含初始损伤岩石的力学性能有重要的工程意义.预先统计岩石试块的初始抗压强度,然后根据其抗压强度给岩石试块施加压力.分别施加了极限抗压强度的10％、30％、50％、70％、80％、90％,以形成不同的初始损伤.然后通过低温冻融实验和单轴压缩实验,将岩石在传统循环荷载作用后的损伤与低温冻融损伤进行比较,得出这两种损伤的异同点,建立了岩石材料在不同环境条件下的损伤表达式,研究了初始损伤对岩石冻融的影响,对今后估测含初始损伤岩石的冻融寿命有一定参考价值.     

基于塑性体积应变的岩石损伤变形特性实验研究

为分析岩石塑性变形与损伤的关系,在定义岩石的初始损伤和临界损伤,提出塑性体积应变分析方法,从而以塑性体积应变为损伤变量,采用归一化方法建立岩石的损伤本构模型。采用递增循环加载实验确定岩石损伤本构模型中的弹性卸载模量和弹性应变比例系数两个参数。通过实验和理论分析得出:当荷载较小时,普通单轴压缩状态下岩石损伤随荷载的增加具有减小趋势,荷载超过一定数值后,岩石损伤才开始增加;单轴递增循环压缩状态下当循环荷载大于约35%峰值强度后,卸载后岩石的损伤具有增加的趋势,小于该荷载之前具有减小的趋势。整个加载过程的理论应力-应变曲线能很好地与实验结果相吻合,在循环加载区间理论结果还能体现出岩石实验结果中的回滞环。     

考虑水化学损伤的岩石真三轴蠕变本构模型

为了准确描述岩石在酸性环境下真三轴蠕变行为的各阶段特征,基于水岩作用的化学动力学理论,定义了考虑PH值与时间的化学损伤因子,将弹性体,非线性Kelvin体,线性Kelvin体和黏弹塑性体进行串联,并考虑岩石在真三轴应力作用下的实际情况,建立岩石酸腐与真三轴应力耦合作用下的损伤蠕变本构模型,通过已有的蠕变试验数据对该模型进行参数辨识与验证,并通过数据拟合得到岩石在真三轴应力下的屈服面方程,探讨中间主应力对蠕变模型的影响.结果表明,推导的本构模型能很好地描述岩石在酸腐作用下真三轴蠕变行为的各阶段特性,验证了其合理性与准确性.     

冻融环境下红砂岩力学特性试验及损伤分析

将实验研究与损伤力学理论分析相结合,对红砂岩进行饱水状态下的冻融循环试验及不同冻融次数下的力学特性试验,分析了岩石的冻融损伤劣化过程,系统研究了岩石的变形破坏规律及损伤扩展力学特性.研究表明:红砂岩呈现出剥落和断裂的冻融损伤劣化模式;随着冻融次数的增加,岩石的强度及弹性模量急剧降低,并表现出压密性增大、弹性减弱、塑性增强的特征;岩石初始细观结构的缺陷经过损伤的非线性演化,表现出宏观力学性能的劣化.     

真三轴应力状态下岩石损伤本构模型

从岩石微元破坏服从Weibull 随机分布的特点出发,建立了真三轴应力状态下岩石损伤软化统计本构关系;根据应力应变关系的几何条件,建立了本构模型参数与岩石变形过程中应力应变曲线特征参量的理论关系,从而增强了模型的适应性;最后通过试验实测数据验证了模型的合理性.     

岩石含水蠕变损伤模型的开发与应用

摘要：为研究岩石含水率对蠕变的影响,将含水开关与蠕变损伤阀值引入蠕变模型,实现了含水劣化与蠕变损伤在本构关系上的耦合,建立了岩石含水蠕变损伤模型。模型与某软岩的三轴压缩蠕变试验结果取得了较好的拟合效果,并由麦夸特法+通用全局优化（LM-UGO）算法反演出了模型参数随岩石含水率的变化规律。在C++语言和FLAC3D中Fish语言的环境下,通过推导模型本构方程的三维差分形式,并利用FLAC3D所提供的接口实现了模型的二次开发。通过对开发的岩石含水蠕变损伤模型进行算例验证和分析,验证了模型的可靠性,也得出了软岩巷道蠕变变形随围岩含水率增大而增加的结论,进一步反映出蠕变模拟计算中考虑岩石含水率的必要性。     

考虑孔洞影响的铸造镁合金ZM6疲劳寿命预估方法

铸造镁合金ZM6是一种应用于直升机减速器机匣制造的典型材料。然而,在铸造过程中产生的内部缺陷对材料的疲劳性能有显著影响。本文研究了含内部孔洞缺陷ZM6材料的疲劳损伤模型和寿命预估方法。首先,采用X射线断层扫描技术,对三个批次毛坯料制成的试验件进行扫描观察,获得了试验件内部孔洞的分布特征。进而,对48件试验件进行了两种应力比下多级应力水平的疲劳试验,获得了各批次试验件寿命结果,并通过观察与分析,得出了孔隙率和近表面较大孔洞为影响试验件疲劳寿命的两个关键因素。然后,基于损伤力学理论提出了通过材料初始弹性模量和等效孔洞局部应力应变场来分别反映孔隙率和近表面较大孔洞影响的疲劳损伤模型和寿命计算方法,并结合ABAQUS软件平台实现了含孔洞试验件的疲劳损伤计算和寿命计算。最后,采用所提理论模型和计算方法给出了试验件的疲劳寿命预测结果,并与试验结果进行了不同维度的对比,验证了所提模型与方法的有效性和适用性。     

单轴压缩下透明类岩石损伤演化特征研究

为研究岩石变形破坏模式及内部裂纹扩展过程,采用环氧树脂、固化剂、熔融石英砂与玻璃砂制备非均质、各向异性的新型透明类岩石,通过室内单轴压缩试验及颗粒流(PFC2D)数值模拟,分析了其破坏模式及裂纹演化过程。室内试验中,透明类岩石峰值强度在砂岩强度范围内的破坏模式与砂岩相似,呈现劈裂剪切混合破坏,裂纹发育大多以层理面为起始点;对比PFC2D数值模拟与室内试验,两者应力-应变曲线相似,最终破坏模式及过程基本一致;将透明类岩石的PFC2D裂纹累积演化曲线划分为无损伤、初始损伤、损伤发展、损伤加速发展、损伤破坏阶段,并确定了其损伤门槛值。本文试验结果,可为直接观察岩石内部裂纹扩展提供参考。     

A micromechanical damage model for rocks and concretes under triaxial compression

Based on analysis of deformation in an infinite isotropic elastic matrix containing an embedded elliptic crack, subject to far field triaxial compressive stress, the energy release rate and a mixed fracture criterion are obtained by using an energy balance approach. The additional compliance tensor induced by a single closed elliptic microcrack in a representative volume element and its in-plane growth is derived. The additional compliance tensor induced by the kinked growth of the elliptic microcrack is also obtained. The effect of the microcracks, randomly distributed both in geometric characteristics and orientations, is analyzed with the Taylor＇s scheme by introducing an appropriate probability density function. A micromechanical damage model for rocks and concretes under triaxial compression is obtained and experimentally verified.     

高温对砂岩宏细观损伤及BP神经网络单轴强度预测研究

为了研究高温后砂岩的力学特性和宏细观损伤变化,对高温作用后的砂岩进行单轴压缩试验、声波损伤检测、X射线衍射试验、扫描电镜试验,分析应力-应变曲线、峰值应力、峰值应变、弹性模量、质量损失率、X射线衍射成像和电镜扫描图像,得到砂岩的细观损伤变化对其单轴抗压强度的影响.利用BP神经网络模型对不同物理量进行训练,预测不同高温作...     

闭孔泡沫铝材料十四面体模型的改进

基于对闭孔泡沫铝发泡过程更为合理的假设,提出了描述胞体结构的改进的十四面体模型,使之可以反映密度增大时质量集中于支柱和顶点的情况。采用有限元方法及耦合边界条件,研究了闭孔泡沫铝的相对弹性模量、泊松比等弹性特征与胞体参数的关系,给出了拟合的弹性模量的计算公式,并对模型在弹性压缩变形下应力分布进行了分析。通过与已有模型的比较表明,改进模型可以较好地模拟闭孔泡沫铝材料的弹性性能。     

Experimental Investigation on Mechanical Behavior of Coarse Marble Under Six Different Loading Paths

A series of triaxial compression experiments were preformed for the coarse marble samples under different loading paths by the rock mechanics servo-controlled testing system. Based on the experimental results of complete stress-strain curves, the influence of loading path on the strength and deformation failure behavior of coarse marble is made a detailed analysis. Three loading paths (Paths I–III) are put forward to confirm the strength parameters (cohesion and internal friction angle) of coarse marble in accordance with linear Mohr-Coulomb criterion. Compared among the strength parameters, two loading paths (i.e. Path II by stepping up the confining pressure and Path III by reducing the confining pressure after peak strength) are suggested to confirm the triaxial strengths of rock under different confining pressures by only one sample, which is very applicable for a kind of rock that has obvious plastic and ductile deformation behavior (e.g. marble, chalk, mudstone, etc.). In order to investigate re-fracture mechanical behavior of rock material, three loading paths (Paths IV–VI) are also put forward for flawed coarse marble. The peak strength and deformation failure mode of flawed coarse marble are found depending on the loading paths (Paths IV–VI). Under lower confining pressures, the peak strength and Young’s modulus of damage sample (compressed until post-peak stress under higher confining pressure) are all lower compared with that of flawed sample; moreover mechanical parameter of damage sample is lower for the larger compressed post-peak plastic deformation of coarse marble. However under higher confining pressures (e.g. σ ₃?=?30 MPa), the axial supporting capacity and elastic modulus of damage coarse marble (compressed until post-peak stress under lower confining pressure) is not related to the loading path, while the deformation modulus and peak strain of damage sample depend on the difference of initial confining pressure and post-peak plastic deformation. The friction among crystal grains determines the strength behavior of flawed coarse marble under various loading paths. In the end, the effect of loading path on failure mode of intact and flawed coarse marble is also investigated. The present research provides increased understanding of the fundamental nature of rock failure under different loading paths.     

正常固结饱和黏性土三剪有限变形弹塑性本构模型研究

基于三剪统一强度准则,利用等量代换法和坐标平移法分别推导出正常固结饱和黏性土的三剪破坏应力比,并将其与修正剑桥模型相结合,得到三剪统一屈服面方程。为反映饱和黏性土的变形非线性及大变形特性,基于有限变形理论,建立了正常固结饱和黏性土的三剪统一有限变形等量代换法和坐标平移法2种弹塑性本构模型。为验证模型的适用性,取江西红黏土制备三种不同压实度的试样,在不同围压下进行常规三轴固结不排水和固结排水压缩试验。将试验数据与本文所提2种有限变形模型及相应的2种小变形模型计算结果进行了对比分析,结果表明,随着变形的发展,有限变形模型相对于小变形模型更接近试验结果,能较好地反映黏性土因高孔隙率（低初始压实度、小围压及压缩变形前期）而产生的大变形特性,虽然小变形模型的计算偏差会随着土样初始压实度和所施加围压的增大而减小,但有限变形模型对不同压实度和围压的计算偏差均相对较小,其中,等量代换法有限变形模型在初始压实度较大或者围压较高时所得计算偏差相对最小。对所提本构模型所做真三轴分析表明,中间主应力影响系数b和初始压实度对土体的强度和变形特性具有一定的影响。主应力差、孔隙水压力和体应变与b值呈正相关性,主应力差与初始压实度呈正相关性,孔隙水压力和体应变与初始压实度呈负相关性。     

Strength and deformation behaviors of veined marble specimens after vacuum heat treatment under conventional triaxial compression

The mechanical behaviors of rocks affected by high temperature and stress are generally believed to be significant for the stability of certain projects involving rocks, such as nuclear waste storage and geothermal resource exploitation. In this paper, veined marble specimens were treated to high temperature treatment and then used in conventional triaxial compression tests to investigate the effect of temperature, confining pressure, and vein angle on strength and deformation behaviors. The results show that the strength and deformation parameters of the veined marble specimens changed with the temperature, presenting a critical temperature of 600℃. The triaxial compression strength of a horizontal vein(β = 90°) is obviously larger than that of a vertical vein(β = 0°). The triaxial compression strength,elasticity modulus, and secant modulus have an approximately linear relation to the confining pressure. Finally,Mohr–Coulomb and Hoek–Brown criteria were respectively used to analyze the effect of confining pressure on triaxial compression strength.     

复杂加载下混凝土的弹塑性本构模型

混凝土材料在不同应力路径下或复杂加载条件下会表现出差异性显著的应力应变关系,在小幅循环加载条件下,其应力应变关系会表现出类似于弹性变形的滞回曲线.在不同应力水平下,混凝土的应力应变关系以及破坏特性都具有静水压力相关特点,即随着静水压力增大,各向异性强度特性弱化.此外,混凝土受压及受拉破坏机理不同,因而对应于混凝土硬化损伤亦有不同,即可分为受压硬化损伤,受拉硬化损伤及两者的混合硬化损伤类型.基于Hsieh模型,对该模型进行了三点改进.（1）针对小幅循环加载下混凝土无塑性变形的试验规律,而模型中在应力水平较低的循环加载条件下始终存在塑性变形的预测问题,采用在边界面模型框架下,设置了应力空间的弹性域,初始屈服面与后续临界状态屈服面几何相似的假定.（2）基于广义非线性强度准则将原模型采用变换应力方法将其推广为三维弹塑性本构模型,采用变换后模型可合理的考虑不同应力路径对于子午面以及偏平面上静水压力效应形成的影响,并避免了边界面应力点奇异问题.（3）分别对拉压两种加载损伤模式建议了相应的硬化参数表达式,可分别用于描述上述加载中产生的应变软化及强度退化行为.基于多种加载路径模拟表明:所建立的三维弹塑性本构模型可合理地用于描述混凝土的一般应力应变关系特性.      

Erratum to: Experimental Investigation on Mechanical Behavior of Coarse Marble Under Six Different Loading Paths

A series of triaxial compression experiments were preformed for the coarse marble samples under different loading paths by the rock mechanics servo-controlled testing system. Based on the experimental results of complete stress-strain curves, the influence of loading path on the strength and deformation failure behavior of coarse marble is made a detailed analysis. Three loading paths (Paths I–III) are put forward to confirm the strength parameters (cohesion and internal friction angle) of coarse marble in accordance with linear Mohr-Coulomb criterion. Compared among the strength parameters, two loading paths (i.e. Path II by stepping up the confining pressure and Path III by reducing the confining pressure after peak strength) are suggested to confirm the triaxial strengths of rock under different confining pressures by only one sample, which is very applicable for a kind of rock that has obvious plastic and ductile deformation behavior (e.g. marble, chalk, mudstone, etc.). In order to investigate re-fracture mechanical behavior of rock material, three loading paths (Paths IV–VI) are also put forward for flawed coarse marble. The peak strength and deformation failure mode of flawed coarse marble are found depending on the loading paths (Paths IV–VI). Under lower confining pressures, the peak strength and Young’s modulus of damage sample (compressed until post-peak stress under higher confining pressure) are all lower compared with that of flawed sample; moreover mechanical parameter of damage sample is lower for the larger compressed post-peak plastic deformation of coarse marble. However under higher confining pressures (e.g. σ ₃ = 30 MPa), the axial supporting capacity and elastic modulus of damage coarse marble (compressed until post-peak stress under lower confining pressure) is not related to the loading path, while the deformation modulus and peak strain of damage sample depend on the difference of initial confining pressure and post-peak plastic deformation. The friction among crystal grains determines the strength behavior of flawed coarse marble under various loading paths. In the end, the effect of loading path on failure mode of intact and flawed coarse marble is also investigated. The present research provides increased understanding of the fundamental nature of rock failure under different loading paths.