裂隙岩体峰值后软化模型及时效性分析

The uneven and discontinuous cracks are often formed in the rock mass. The preferred orientation, spacing, density, and mechanical characteristics of cracks are the main factors influencing mechanical properties of rock mass, causing deformation and giving rise to instability of the rock mass, which makes the rock mass show a remarkable softening and strong anisotropy. Deformation and instability of the rock mass are linked with propagation and coalescence of microscopic and macroscopic cracks. Based on the physical and mechanical experiments, and the coupling between elastoplastic and micro-crack damage, the rock softening after the peak load is examined, and more accurate elastoplastic damage model is explored. The physical simulation of macro-crack rock model is carried out. Based on fracture mechanics and damage mechanics, the failure mechanism and aging deformation of fissured rock mass are researched. Combined with the elastoplastic damage model and fracture softening of the macro-crack, the effect of elastic-plasticity, micro-crack damage, and macro-crack fracture softening on mechanics properties of fissured rocks are analyzed, and the elastic-plastic fracture damage model of the coupling of plastic and fracture softening of rock mass are then established. The aging fracture softening of the fissured rocks under compressions is further investigated after the peak load. These research results are applied into engineering rock mass, which can help evaluate deformation, failure, and long-term stability of the fractured rocks in the environment of complex stress.

工程岩体内部分布着不均匀的贯通和非贯通裂隙面，这些裂隙面存在的优势方位、间距、密度、力学特征等对岩体的力学性质和变形失稳破坏产生了显著影响，致使岩体表现出显著的软化和强烈的各向异性。这些微观和宏观裂隙的扩展贯通是诱发岩体变形失稳的重要因素。基于物理力学实验，研究岩石峰值荷载后的软化特征，考虑弹塑性与微裂隙损伤的耦合效应，探索更准确的岩石的弹塑性损伤模型。利用宏观裂隙岩体模型的物理模拟，采用断裂力学和损伤力学等对裂隙岩体破坏机制及时效变形进行研究，结合弹塑性损伤模型，并考虑宏观裂隙的断裂软化，探讨岩石弹塑性、微裂隙损伤演化及宏观裂隙断裂软化对裂隙岩体力学性质的影响，进而建立岩体塑性与断裂软化耦合的损伤断裂模型。进一步研究压缩荷载下裂隙岩体峰值后断裂软化的时效性。将研究成果应用于具体工程岩体，该研究有助于在复杂应力环境下工程裂隙岩体的变形失稳及长期稳定性进行评价。

工程岩体内部分布着不均匀的贯通和非贯通裂隙面，这些裂隙面的存在对岩体的力学性质和变形破坏产生了显著影响，致使岩体表现出显著的软化和强烈的各项异性。这些微观和宏观裂隙的扩展贯通是诱发岩体变形失稳的重要因素。研究岩石峰值荷载后的软化特征，考虑弹塑性与微裂隙损伤的耦合效应，探索更准确的岩石的弹塑性损伤模型，具有重要的理论意义与工程价值。.该项目主要的研究内容：准确描述反映岩体峰值后软化特征的损伤演化变量，分析围压和微裂隙特征对损伤变量的影响；考虑宏观裂隙断裂软化及裂隙演化的断裂软化因子，进而建立能准确反映宏观裂隙断裂扩展软化的弹塑性损伤断裂模型；利用该模型对具体工程岩体进行稳定性和长期稳定性评价，并结合工程岩体变形的监测，反馈与分析模型的适用性；以砂岩和泥岩为对象，通过室内试验、理论分析和数值模拟相结合的方法对其的蠕变特性进行研究，并讨论岩性、围压、轴压、含水率、裂隙长度等对砂岩蠕变特性的影响；开展了裂隙岩体的断裂机理研究，并对其进行了工程应用。.基于线弹性断裂理论提出了适用于II型断裂的径向剪应力准则、双剪应力准则和基于Mohr-Coulumb准则的压剪断裂判据，以及利用Ⅰ、Ⅱ型等效应力强度因子比值和对应断裂韧度比值的大小关系来判定复合型断裂类型的方法。相比极限平衡方法而言，用断裂力学方法分析评估岩质边坡稳定性更具优越性，实例及数值模拟分析表明，其可有效地评价危岩体稳定性、预测裂纹起裂角，这对预测岩体的失稳体积，以及确定合适的锚固技术和锚固深度具有重要意义。此外，通过对标准西原模型进行改进，获得了能够描述非线性蠕变特征的改进西原模型，并通过试验数据验证了其合理性。改进的西原模型克服了传统西原模型不能准确的描述出加速蠕变阶段的缺点，并且模型参数较少，推导过程简单，适用性好，所以该模型具有较好的工程应用价值，在对滑坡预报方面具有重大的指导意义。