深埋脆性岩石的本构模型及开挖破坏区深度预测

发布时间：2018-07-18 12:16

【摘要】：随着基础工程建设、资源开发的逐步深部化和核废料处理的迫切性,深埋地下洞室的开挖破坏区成为国内外学者关注的热点问题。本文采用理论分析、数值模拟与现场监测对比验证的方法,围绕深埋硬脆性岩石隧道开挖过程中岩石呈现的破坏特征、开挖破坏区的形成机理、开挖破坏区数值模拟和深度预测方法等一系列问题展开研究。本文首先总结了脆性岩石在破坏过程中力学特性的演化规律,然后在理论和已有研究成果的基础上分析适合描述脆性岩体力学行为的本构模型,即弹-脆-塑性(EBP)模型,粘聚力-脆性-摩擦强度(CBF)模型和裂隙初始-劈裂界限(DISL)模型,为数值模拟提供了模型。借助于有限元软件Phase2对加拿大地下实验室Mine-by隧道进行开挖模拟。通过与Mine-by试验隧道开挖破坏区的监测资料进行比对,选择最有效的脆性模型。对比发现,选用EBP模型得到的破坏区范围角大于观测值,选用CBF模型计算得到的破坏区深度和范围角均小于监测数据,而通过DISL模型计算得到的深度和范围角均与观测值相当。该结果初步验证了DISL模型的优越性。在此基础上,考虑实际开挖面轮廓具有高度不规则性,因此以光滑圆形和连续小半圆形分别模拟设计和实际开挖面轮廓,获得不同的开挖破坏区范围和应力状态,可见简化开挖面几何形状具有不合理性。由于隧道左右边墙也产生破坏区,所以采用渐进开挖法模拟隧道的开挖过程,对比分析开挖模拟方法对破坏区形状的影响。结果表明,以实际断面轮廓为隧道的开挖边界,通过DISL模型和渐进开挖法能够很好地捕获开挖破坏区的几何形状和范围。采用经上述验证后的数值模拟方法对光滑圆形隧洞进行模拟计算,分析开挖面附近围岩的力学响应。研究发现:岩石从高度破坏区进入破坏区的标志是:最小主应力值开始增长,拉应变值达到最大,剪应变值急剧减小;破坏区内、外边界的分区指标是体积应变曲线发生反转;屈服单元的产生标志着从破坏区过渡到影响区;DISL模型能够很好地刻画围岩应力路径,准确描述脆性岩体的力学行为。对于一个给定的工程,上述分区方法为准确确定破坏区各区的尺寸提供了新思路。如果将这一成果进一步拓展研究,并应用于工程实践,将会对工程的长期稳定性预测产生重要的指导意义。
[Abstract]:With the construction of basic engineering, the gradual deepening of resource development and the urgency of nuclear waste disposal, the excavation and destruction area of deep buried underground cavern has become a hot issue that scholars at home and abroad pay attention to. In this paper, the method of theoretical analysis, numerical simulation and field monitoring is used to verify the failure characteristics of the rock and the formation mechanism of the damage zone during the excavation of the hard-brittle rock tunnel. A series of problems such as numerical simulation and depth prediction of excavation failure zone are studied. In this paper, the evolution law of mechanical properties of brittle rock in the process of failure is summarized, and then the constitutive model which is suitable for describing the mechanical behavior of brittle rock mass is analyzed on the basis of theory and existing research results, that is, the elastic-brittle plastic (EBP) model. The cohesion brittleness friction strength (CBF) model and the fracture initial-splitting limit (DISL) model provide a model for numerical simulation. The excavation of Mine-by tunnel in Canadian underground laboratory was simulated by the finite element software Phase2. The most effective brittle model is selected by comparing with the monitoring data of the excavation failure zone of the Mine-by test tunnel. It is found that the range angle of damage zone obtained by using EBP model is larger than the observed value, the depth and range angle of damage zone calculated by CBF model is smaller than that of monitoring data, and the depth and range angle calculated by DISL model are equal to the observed values. The results preliminarily verify the superiority of the DISL model. On this basis, considering the highly irregular profile of the actual excavated surface, the smooth circular and continuous small semicircle are used to simulate the design and actual excavated surface contour, respectively, and to obtain different excavation failure areas and stress states. It can be seen that the simplified geometric shape of the excavated surface is unreasonable. The excavation process of the tunnel is simulated by the progressive excavation method, and the influence of the excavation simulation method on the shape of the damage zone is analyzed comparatively because the damage zone is also caused by the left and right side walls of the tunnel. The results show that the geometric shape and range of the excavation failure zone can be captured well by using the DISL model and the progressive excavation method taking the actual section profile as the excavation boundary. The numerical simulation method verified above is used to simulate and calculate the smooth circular tunnel, and the mechanical response of surrounding rock near the excavating surface is analyzed. It is found that the sign of rock entering the failure zone from high failure zone is that the minimum principal stress value begins to increase, the tensile strain value reaches the maximum, and the shear strain value decreases sharply, and the zoning index of the outer boundary is the inversion of the volume strain curve in the failure zone. The generation of yield element indicates that the DISL model can well describe the stress path of surrounding rock and accurately describe the mechanical behavior of brittle rock mass. For a given project, the above zoning method provides a new idea for the accurate determination of the size of the damage zone. If this achievement is further developed and applied to engineering practice, it will be of great significance to predict the long-term stability of engineering.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD315

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