【作者】 朱泽奇；

【导师】 盛谦；

【作者基本信息】 中国科学院研究生院（武汉岩土力学研究所） ， 岩土工程， 2008， 博士

【摘要】 为探索边坡开挖扰动区EDZ的研究方法和相关的若干理论问题,本文以三峡船闸高边坡为工程背景,对高边坡开挖扰动区EDZ和工程岩体的力学特性进行了系统研究与分析,主要研究工作与特点表现在以下几个方面:(1)基于三峡船闸边坡开挖扰动区的大规模综合测试和监测成果,对开挖边坡的扰动影响范围和影响程度建立了初步的认识。在此基础上进行边坡开挖扰动区地质成因分析,并基于3DEC直接法建立了中隔墩岩体的三维节理网络模型,采用三维离散单元法3DEC进行了多组卸荷应力路径模拟,研究表明:卸荷条件下岩体变形主要表现为岩体内节理与裂隙特别是陡倾角节理与裂隙的张开变形,在此基础上进行了陡倾角节理裂隙的开裂特征和破坏机理研究。(2)在总结前人进行的三峡花岗岩室内岩石力学试验的基础上、分别利用MTS刚性试验机和RT3岩石高压真三轴压缩仪进行了多种应力路径测试,研究了三峡花岗岩在加荷条件和卸荷条件下的变形特性、破坏形式及破坏后区的应力-应变关系,研究发现:基于实验观察与断裂力学分析,可以认为花岗岩裂纹扩展模式主要表现为拉伸破坏,从起裂至裂纹稳定扩展阶段,其内部裂纹属I型裂纹。起裂应力σci随围压变化幅度不大,与峰值强度相比,起裂应力一般保持在峰值应力的25~50%范围内;三峡花岗岩在峰后应变软化过程中,其强度参数c值随广义塑性应变的增大而快速减小,而?值几乎保持不变。(3)针对三峡花岗岩的全过程应力-应变曲线的损伤力学分析,发现脆性岩石在不同应力路径和不同加载控制方式下均以侧向损伤为主,达到临界破坏时,损伤值稳定在0.7~0.8左右,说明了裂纹应变在侧向的发展是导致脆性岩石破坏的主要原因。相对来说轴向损伤较小,但轴向损伤演化规律的不同却是造成不同变形破坏形式的主要原因;三峡花岗岩的临界破坏行为可以用侧向变形来表征,且临界侧向应变和侧向损伤规律不受围压和加载路径的影响,由此可以建立基于应变空间的,考虑卸荷应力路径的损伤模型和应变型破坏准则。(4)基于三峡花岗岩的损伤力学模型,采用显示有限差分法,以正交设计、最小二乘支持向量机与粒子群算法相结合建立高效的反演分析方法,对三峡永久船闸高边坡岩体进行三维位移反分析,以损伤模型的力学参数作为基本变量,实现了边坡非线性系统的多参数反演。(5)结合三峡船闸高边坡开挖扰动区的实测成果,在对开挖扰动区形成机理的认识基础上,针对边坡岩体剪切变形和单元安全系数的概念分析建立了开挖扰动区临界准则。进一步基于损伤模型计算得到的不同损伤程度的损伤区综合评价开挖扰动区分布范围及其岩体力学性质。对应实测开挖扰动区的分布范围和形状,可以近似确定开挖损伤区岩体的损伤值约在0.6~0.8以内,卸荷影响区岩体的损伤值约在0.4~0.6以内,轻微扰动区岩体的损伤值约在0.2~0.4以内;由此基于Hoek-Brown经验强度准则,引入开挖弱化因子,结合地质强度指标GSI,进行开挖扰动区岩体力学参数研究。更多还原

【Abstract】 To explore the means for the determination of excavation disturbed zone (EDZ) of rock slope and its related theoretical problems, multiple methods are used to investigate the EDZ and its rock mechanical behaviors for the high slopes in Three Gorges Project (TGP). Major work and its characteristics are summarized as follows:(1) Based on multiple in-situ tests and field monitoring for EDZ in TGP, in which its zoning models and criteria are established, and weakening extent for its mechanical behaviors evaluated. Based on the engineering geological survey, a probability model of joint network is established in 3 dimensions by using the direct method to generate random number, and the deformation analysis of rock mass under unloading condition is carried out using 3 Dimensional Distinct Element Code (3DEC) to simulate joint opening phenomenon in the middle isolated pier of the permanent shiplock slope in TGP, and it is found that rock mass deformation mainly exhibits joint opening, especially steep dip joint opening. Then, studies on opening characteristics and failure mechanism of steep dip joint are carried out.(2) For the Three Gorges granite specimens, the conventional triaxial compression and the confining pressure reduction test under constant axial strain and stress are carried out. The deformational characteristics and failure model of brittle rock under different stress paths or different loading control modes are studied; and it is found that the crack initiation stress changes at the same extent with confining pressure, and comparing with the peak strength,the crack initiation stress is generally located between 25% and 50% of the peak strength. Through experimental and theoretical analyses, the result shows that the microcosmic failure of Three Gorges granites is mainly induced by tensile cracks under uniaxial and triaxial compressive conditions; and the cracks inside the granite belong to I-mode fracture in stable crack growth stage; In the post-peak strain softening process, the value of c decreases with the increasing of generalized plastic strain, while the value of ? keeps constant.(3) Based on the analysis of the complete stress-strain curves and the damage mechanism of the Three Gorges granite, it is put forward that the brittle rock mainly occurs lateral damage and exhibits the similar damage evolutionary rule under different stress paths and loading control modes; and the critical failure generally occurs at a damage variable level of 0.7 to 0.8. Finally, a damage model considering the unloading effect and a failure criterion in strain space are established, in which the lateral damage variable is seen as a critical variable.(4) One back analysis model of mechanical parameters is established by using orthogonal design theory, least squares support vector machines and particle swarm optimization, and the relative mechanical parameters of damage model are back analyzed. Then, the construction and excavation process of the permanent shiplock slope in TGP is simulated by three-dimensional fast Lagrangian method (FLAC3D).(5) Based on the tests and monitoring of EDZ, critical criteria of shear strain and element safety factor for the permanent shiplock slope in TGP are established. Distribution region of EDZ and mechanical behaviors of rock mass are further evaluated by using damage model, and the result shows that damage variable is 0.6-0.8 for damaged zone (DZ), 0.4-0.6 for affected zone (AZ) and 0.2-0.4 for slight affected zone (SAZ). Finally, the slope excavation softening factor is introduced to Hoek-Brown empirical strength criterion, based on the deficiencies of using Geological Strength Index (GSI) to estimate the rock mass mechanical parameter of EDZ.更多还原