深部挤压流变岩体预应力锚固力学机理及失效破坏机制研究

It is at a fledging period for the study on long-term stability and reliability of rock engineering，anchorage mechanism and its timeliness, which are as critical and fundamental problem in deep rock mass. After studying the creeping effect of nonlinear rock mass on timeliness of anchorage, the long-term stability and reliability of anchorage body, with regard to deep squeezing creeping rock mass, the large deformation mechanism and deformation forecast, prestressing anchorage mechanism and anchoring-failure mechanism, rational anchor supporting technology and long-term stability estimate of anchor supporting are being furthered researched as advanced problems: Firstly, large-deformation mechanism，strength criterion and method of deformation prediction are deeply revealed by laboratory creeping test and field test. Then by anchorage test and anchoring-failure test in-situ, prestressing anchorage mechanism, anchoring-failure modes and characteristics are studied so as to build constitutive model of anchorage and criterion of anchoring-failure. On the basis of above theory, anchoring parameters optimization and the best anchoring opportunity are studied and long-term stability of anchorage are evaluated in deep squeezing creeping rock mass according to demonstrate projects. The achievements can be provided as important theoretical basis to rational supporting and safety assessment in deep underground engineering.

目前国内外对深部流变岩体工程的长期稳定性和可靠性、岩体锚固机理及时效性等许多关键性基础问题的研究尚属起步阶段。继青年科学基金研究岩体非线性流变特性对锚固时效性的影响及对锚固体稳定性、可靠性的评价之后，本项目针对深部挤压流变岩体，深入开展高地应力岩体地下工程挤压大变形机理及变形预估、预应力锚固机理及失效破坏机制、合理锚固技术及支护结构长期稳定性评价等前沿课题的研究：首先通过室内蠕变试验和现场试验测试，深刻揭示高应力流变岩体的大变形机理、强度特征和变形预测方法；然后开展现场原位锚固流变试验和失效破坏试验，研究深部挤压流变岩体的预应力锚固机理、锚固失效模式和受力变形破坏特征，分别建立锚固支护力学模型和失效破坏判别准则；在此基础上，开展依托工程的锚固参数优化和最佳锚固时机的研究，对深部挤压流变岩体地下工程的锚固长期稳定性进行分析评价。研究成果将为深部地下工程的合理支护和安全评价提供重要理论依据。

深部地下工程挤压性流变岩体极易出现的大变形失稳、塌方等地质灾害问题。通过系统的实验室试验、现场试验与监测、数值仿真分析等方法，研究深埋岩体挤压大变形机理、预应力锚固力学机理及其失效破坏机制，实现挤压流变岩体工程锚固参数及支护结构的优化分析。取得的研究成果：.（1）三轴泥岩流变试验结果表明流变过程中呈现非线性的特点。岩石在低应力水平时只产生衰减蠕变，而不出现定常蠕变和加速蠕变。在处于较高应力水平时定常蠕变和加速蠕变特性会全部显现，加速蠕变出现后，曲线稍上翘后试件即发生破坏。.（2）现场锚杆（索）试验可以看出，锚杆（索）轴力随着时间基本呈现增大的趋势，这是由于围岩体变形，锚杆（索）体开始承载并对围岩体提供支护阻力所致，锚杆轴力从洞壁沿杆长方向逐渐减小，锚索的轴力基本上在3号测点轴力数值最大（距洞壁4.6m处），最大值为170kN，可基本判定该位置处于中性点附近，锚索内锚固段轴力数值整体上要大于非锚固段的轴力。.（3）由于急倾斜的现场地质条件，造成了支护结构应力和位移的非对称分布，偏压作用明显。当岩层界面分界线与支护结构所支撑的巷道轮廓线呈相切或者小角度相交的空间位置关系时，支护结构局部受力或变形加剧。.（4）底板仰拱施工方案能有效的减小巷道底板的位移。对比两种施工方案，底板最大位移减小近27cm，塑性区由35.4m2减小到9.3m2，效果非常显著。建议采用底板仰拱和全封闭的施工方式，减小巷道的维修工作量；由于岩层中锚杆和锚索受力均较大，其安全储备系数较低，建议今后改成Ⅲ级螺纹钢。由于地层错动导致的锚杆锚索应力较大，为增大锚杆和锚索的支护力，建议垂直地层施加锚杆和锚索。