不同加卸荷应力路径下大理岩破坏过程的能量演化机制与本构模型研究

发布时间：2018-04-03 04:19

本文选题：加卸荷　切入点：屈服函数　出处：《青岛理工大学》2013年硕士论文

【摘要】：地下工程开挖是一个极其复杂的加卸荷受力过程，而岩体在加卸荷不同应力路径条件下的变形特征、强度特性及破坏机制存在明显差异。对不同应力路径下岩石变形破坏性质的研究，对补充完善岩石力学理论和指导工程设计、施工有着重要的理论和工程意义。本文开展了不同应力路径条件下的大理岩加卸荷破坏试验研究，从能量变化角度分析了不同应力路径下大理岩的破坏机制，给出了大理岩变性破坏过程的能量非线性演化模型。论文主要取得了下列研究成果： (1)通过完整大理岩岩样加卸荷试验，揭示了加卸荷条件下岩石变形、破坏特征与强度参数变化规律。岩样加荷破坏弹性阶段轴向变形起主导作用，屈服开始后环向变形快速增加；加荷破坏大理岩起裂应力随围压升高向峰值强度逐渐靠近，围压延迟了岩石的破坏；卸荷破坏岩样的峰值强度随着卸荷速率的增加逐渐减小，随着卸荷初始围压的升高逐渐增大，环向变形和体积变形对慢速卸荷比快速卸荷更敏感。 (2)根据广义塑性力学理论，利用试验数据构建了大理岩加卸荷变形过程的屈服面，，保证了屈服函数的唯一性和准确性。大理岩加荷破坏过程的剪切屈服面为直线形式，卸荷破坏剪切屈服面分为卸荷前的直线形式和卸围压过程的二次抛物线形式，加荷破坏体积屈服面分为压缩和剪胀两段直线形式，卸荷破坏体积屈服面分为卸荷前的直线形式和卸荷后的二次抛物线形式。 (3)根据大理岩变形破坏过程的能量演化曲线，可以将大理岩卸荷破坏分为四个阶段：压密阶段、弹性阶段、裂纹扩展阶段和峰后破坏阶段。到达屈服点前，岩样吸收的能量大部分以弹性能形式存储于岩样内部；屈服点后到峰前的非线性变形阶段，弹性能增速缓慢，而耗散能的增速变大；到达峰值强度时，岩样内部存储的弹性能达到储能极限，弹性能瞬间释放，耗散能快速升高。常规三轴的储能极限高于单轴压缩，而峰前卸围压的储能极限低于常规三轴压缩；随着卸荷速率增快，大理岩吸收总能量变化率、弹性能变化率和耗散能变化率都呈减小趋势；卸荷速率越快，卸荷破坏需要的能量增量越小，在较小的能量增加下就会发生破坏；岩石破坏的驱动能量（存储的可释放弹性能）主要是在卸荷之前的加荷过程积聚的，加荷过程存储的能量对岩石卸荷破坏起到决定作用。 (4)根据大理岩变形破坏过程的能量演化特征，结合生态学的竞争机制，构建了大理岩破坏过程的能量积聚演化模型。根据能量模型中的能量迭代增长因子与轴向应变的变化关系，提出了不同应力路径下岩石破坏的起裂预警应变值，单轴压缩为峰值应变的77%左右，常规三轴为峰值应变的72%~76%之间，卸荷试验为峰值应变的72%~81%之间。
[Abstract]:The excavation of underground engineering is an extremely complicated process of loading and unloading, but the deformation characteristics, strength characteristics and failure mechanism of rock mass under different stress paths are obviously different.The study of rock deformation and failure properties under different stress paths is of great theoretical and engineering significance for supplementing and perfecting rock mechanics theory and guiding engineering design and construction.In this paper, the experimental study of marble unloading failure under different stress paths is carried out, the failure mechanism of marble under different stress paths is analyzed from the angle of energy variation, and the energy nonlinear evolution model of marble denaturing failure process is given.The main achievements of this thesis are as follows:1) through the loading and unloading test of complete marble samples, the variation law of rock deformation, failure characteristics and strength parameters under loading and unloading conditions is revealed.The axial deformation plays a leading role in the elastic stage of specimen loading failure, and the circumferential deformation increases rapidly after the beginning of yield, and the initial crack stress of loaded failure marble approaches to the peak strength with the increase of confining pressure, and the confining pressure delays the failure of rock.The peak strength of unloading failure rock samples decreases gradually with the increase of unloading rate and increases with the increase of initial confining pressure of unloading. The toroidal deformation and volume deformation are more sensitive to slow unloading than fast unloading.2) according to the generalized plastic mechanics theory, the yield surface of marble loading and unloading deformation process is constructed by using the test data, which ensures the uniqueness and accuracy of the yield function.The shear yield surface of marble loading failure process is linear. The unloading failure shear yield surface can be divided into straight line form before unloading and quadratic parabola form of confining pressure process.The yield surface of loading failure volume can be divided into two straight forms: compression and shear expansion. The yield surface of unloading failure volume can be divided into linear form before unloading and quadratic parabola form after unloading.According to the energy evolution curve of marble deformation and failure process, the unloading failure of marble can be divided into four stages: compaction stage, elastic stage, crack propagation stage and post-peak failure stage.Before reaching the yield point, most of the energy absorbed by the rock sample is stored in the form of elastic energy inside the rock sample. At the stage of nonlinear deformation from the yield point to the peak, the growth rate of elastic energy is slow, but the growth rate of dissipative energy becomes larger.The elastic energy stored in rock samples reaches the limit of energy storage, the elastic energy is released instantly, and the dissipation energy increases rapidly.The energy storage limit of conventional triaxial is higher than that of uniaxial compression, while the energy storage limit of unloading confining pressure before peak is lower than that of conventional triaxial compression, and with the increase of unloading rate, the change rate of total energy, elastic energy and dissipation energy of marble decrease.The faster the unloading rate, the smaller the energy increment required for unloading failure, and the smaller the increase in energy, the smaller the damage will occur. The driving energy of rock failure (the released elastic energy stored) is mainly accumulated during the loading process before unloading.The energy stored in the loading process plays a decisive role in the unloading failure of rock.4) according to the energy evolution characteristics of marble deformation and failure process and the competition mechanism of ecology, the energy accumulation evolution model of marble failure process is constructed.According to the relationship between the energy iterative growth factor and the axial strain in the energy model, the pre-warning strain values of rock failure under different stress paths are proposed. The uniaxial compression is about 77% of the peak strain.The conventional triaxial is between 72% of the peak strain and the unloading test is between 72% and 81% of the peak strain.
【学位授予单位】：青岛理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU45

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