应变软化是指应力-应变曲线中轴向应力随应变的增加而减小的现象,许多种类的岩土介质在工程扰动的作用下呈现应变软化的行为。在分析应变软化问题时,其应力-应变关系式中的切线刚度矩阵是非正定的,由此导致计算求解的困难。将岩体应变软化过程简化为一系列脆塑性过程,于是应变软化问题的求解归结为一系列脆塑性过程的分析。基于经典弹塑性力学理论,提出了应变软化过程模拟方法及其相应的有限元求解过程,编制了计算程序,研究了应变软化本构模型中不同强度弱化速率对圆形洞室围岩塑形区分布的影响,进一步分析了应变软化模型对应的隧道径向变形沿洞轴方向的分布特征,并与已有监测数据得到的分布规律进行了对比。初步的研究结果表明,应变软化模型得到的计算结果是比较合理的。

In stress-strain curve, the process of decline of uniaxial stress at increasing strain is defined as strain-softening. Many types of geomaterials behave in strain-softening way in the case of disturbance of engineering activities. When the stress-strain relationship is described in mathematical formulation, the matrix of tangential elastic moduli is no longer positive-definite. Thereby difficulties arise in finding the solution to strain-softening problem. Strain-softening process is simplified into a series of brittle-plastic behavior;and solving brittle-plastic problem comes down to obtaining a series of brittle-plastic solutions. On the basis of classic plasticity theory, the method for analyzing strain-softening behaviour is proposed;and the corresponding solution process is implemented in finite element code. Furthermore, the influences of different strength-weakening modes on the distribution of plastic zone in the surrounding rock mass of a circular tunnel are studied. The longi

岩土工程中的许多土体有应变软化行为，这种软化行为能导致应变局部化，进而对土体的稳定性有重要影响。首先研究饱和砂土的排水平面应变压缩试验的剪切带的形成，进行数值分析，预测了实验现象。然后，考虑土体应变软化盾构掘进面失稳的影响，对深埋隧道的盾构掘进进行三维数值分析，对比分析渗流条件下应变硬化模型和应变软化模型以及应变软化条件下考虑渗流与未考虑渗流模型之间的区别。分析表明，土体应变软化更容易导致盾构掘进界面失稳，使得开挖面的极限支护压力和地表沉降增大、塑性区扩展比没有应变软化的土体更大。探讨了诸如内摩擦角、黏聚力等土质应变软化参数的变化对盾构掘进界面稳定性的影响，发现内摩擦角软化的影响较大，黏聚力次之。最后，对天津地铁9号线的一段盾构掘进进行了模拟，其结果与工程实测数据相吻合。

Many kinds of soil in geotechnical engineering display strain-softening behavior ,which can result in strain localization and, furthermore, the instability of soil. On the basis of the local strain fields in the specimen obtained from the drained plane strain compression test on saturated sand, the paper first makes a numerical analysis to predict the experimental phenomenon. Then, the strain-softening influence of shield excavation surface instability is consid-ered, three-dimensional numerical simulation for deep shield tunneling is performed, and the strain hardening and sof-tening models in the condition of seepage are compared, so are the seepage and non-seepage models in the condition of strain softening. The analysis shows that, compared with soil without strain-softening behavior, the strain-softening of soil more easily causes the instability of shield tunneling face, increases the limits of face pressure and the settle-ment of the ground, and leads to more expansion of plasti

借助于ANSYA/LS-DYNA数值分析软件对SHPB试验进行数值模拟,就不同应变率对砂岩力学性能的影响进行了研究,探讨了不同应变率对砂岩峰值应力、弹性模量、软化模量的影响规律,系统地分析了砂岩在不同应变率作用下的破坏规律。结果表明：随着应变率的增加,峰值应力显著增加,表现出较强的应变率相关性;应变率增大,弹性模量随之增大,但增长速率逐渐减小;应变率越大,软化模量反而降低。应变率ε从632.4 s^-1变化到752.5 s^-1时,软化模量由-2.98降到-4.18,降低了28.71%;当应变率ε大于752.5 s^-1为1757.9时,软化模量仅降低了5%,说明应变率较大时变化趋势较为缓慢。高应变率下砂岩试件的动态压缩破坏主要呈现为轴向劈裂破坏。

Conducting a numerical simulation of the SHPB experimental data through ANSYA/LS-DYNA,the present paper studies the impact of different strain rates on the mechanical property of sandstone and investigates the effect law of different strain rates on the peak stress,elastic modulus and softening modulus of sandstone,offering a systematic analysis of the damage law of sandstone under different strain rates. The findings reveal that the peak stress shows a notable increase as the strain rate increases and that the two exhibit a strong correlation. Experimental data shows that the elastic modulus will increase as the strain rate increases,but the rate of increase will decrease gradually. When the strain rate increases,the softening modulus will actually decrease. Experimental data also shows that when the strain rate ·ε varies from 632. 4 s-1 to 752. 5 s-1 ,the softening modulus will decrease from -2. 98 to-4. 18,showing a 28. 71% decrease while the softening modulus only shows

应用Muskhelishvil应力函数全场解,根据幂指数函数描述的混凝土拉应变软化模型导出断裂过程区(FPZ)过程值及临界值的解析表达式,分析了在最大拉应变强度理论下软化指数对FPZ过程值及临界值的影响。结果表明:混凝土FPZ过程值及临界值都随着软化指数的增加而增加,不同泊松比下变化规律相近。

The developing size and critical size of concrete fracture process zone ( FPZ) is obtained by use of a power exponent function considering the effect of the tensile strain softening based on the stress function of Muskhelishvil .The influences of tensile strain softening index on the developing size and critical size of FPZ are studied .The results show that the developing size and critical size of FPZ increase with the increasing tensile strain softening index and the law is very identical with different Poisson''s ratios.

考虑了渗流体积力、岩体应变软化、破裂膨胀性重要因素,应用弹塑性力学理论,推导了渗流场作用下巷道围岩的应力和位移分布规律,给出了巷道围岩不同分区范围与孔隙水压力、岩体应变软化程度、破裂膨胀性之间的关系;研究表明,孔隙水压力和岩体破裂膨胀特性对巷道围岩破裂区范围的影响程度比对塑性区范围的影响程度明显;考虑渗流场比不考虑渗流场的影响时,塑性区范围和破裂区范围都要大;岩体应变软化程度对巷道围岩塑性区和破裂区的范围影响同样显著;渗流、应变软化、破裂膨胀性对巷道围岩变形的影响都比较明显。研究成果为渗流场作用下的巷道支护工程有一定的参考价值。

According to seepage body force,strain softening and rupture expansion of rock mass,elastic-plastic mechanics theory,distribution laws of stress and displacement of surrounding rock in seepage field are derived,and relationships between different zonation range of the surrounding rocks,pore water pressure,strain softening and rupture expansion are established.The results show that the pore water pressure and rupture expansion rock mass have a more obvious impact on the surrounding rock rupture area than the plastic zone.Both the plastic zone and the rupture area are larger when the seepage field is considered.The impact of strain softening on both the plastic zone and the rupture zone of surrounding rock is very significant,and both seepage and strain softening rupture expansion affect deformation of surrounding rock of roadways obviously.It provides certain reference values for the roadway support engineering in seepage field.