地下开挖诱发顺层岩质边坡失稳机理及锚杆控制体系优化方法

The stability evolution and disaster control of consequent bedding rock slope under the action of underground excavation is one of a significant theoretical and technical problem in the slope protection engineering. This project is planning to systematically study the instability mechanism of consequent bedding rock slope induced by underground excavation and optimal design for the control system of anchor bolt. Firstly, based on the field research of typical cases, the interaction relationship between the occurrence characteristics of consequent bedding rock slope and its failure modes would be identified, and the instability mechanics model would be established through combining the layered rock mass mechanics and the nonlinear large deformation theory to study rules of deformation and failure of consequent bedding rock slope under different influence factors of underground excavation, explore the activation mechanism of its sliding failure and propose the corresponding critical instability criterion. Secondly, the load distribution and mechanical response of fully grouted anchor bolt would be researched considering the interaction between the bolt and consequent bedding rock-mass to reveal the synergistic mechanism of lateral and axial resistances of fully grouted anchor bolt, in addition, its long-term anchoring performance installed in the consequent bedding rock slope would be studied considering the rheological property of bedding rock-mass structural plane. At last, the influence rules of anchor bolts’ arranged area, spacing, length and anchorage angle on the effect of slope protection would be analyzed , that is aiming to develop an optimization method for the control system of anchor bolt set in consequent bedding rock slope under the condition of underground excavation. Relevant research results would have important reference value for guiding disaster prevention and control of consequent bedding rock slope.

顺层岩质边坡在地下开挖卸荷作用下的稳定性演化及灾变控制是边坡防护工程中一个重大理论和技术难题，因此，本项目围绕地下开挖诱发顺层岩质边坡失稳机理及锚杆控制体系优化设计方法开展研究。首先，基于现场典型案例的调研统计，辨识顺层岩质边坡赋存特征与失稳模式的相互关系，结合层状岩体力学和非线性大变形理论建立其失稳破坏力学模型，研究不同地下开挖影响因素下顺层岩质边坡的变形破坏规律，揭示其滑塌失稳的启动机制，并给出对应的失稳判据；其次，考虑全黏结型锚杆与顺层岩体的相互作用，研究锚杆荷载分布规律和受力响应特性，揭示锚杆轴向抗力与横向抗力的协同作用机制，并考虑顺层岩体结构面的流变特性，研究顺层岩质边坡全黏结型锚杆的长期锚固性能；最后，分析锚杆布设区域、间排距、长度及锚固角对边坡防护效果的影响规律，形成地下开挖条件下顺层岩质边坡锚杆控制体系的优化设计方法。研究成果对于指导顺层岩质边坡的灾害防治具有重要参考价值。

顺层岩质边坡是分布范围较为广泛的一种边坡形式，其在地下开挖卸荷作用下易发生顺层滑移，因此，顺层岩质边坡在地下开挖扰动影响下的安全性控制一直是边坡防护工程中一个重大理论和技术难题。本项目综合运用现场调研、理论分析、数值模拟和物理模型试验等手段，主要开展了以下两个方面的研究工作：. (1)以相似理论为依据，考虑岩层倾角和开挖区位置对顺层岩质边坡破坏模式的影响，完成了顺层岩质边坡地下开挖相似模型试验，并结合离散元模拟方法研究了顺层岩质边坡地下开挖失稳过程，确定顺层岩质边坡地下开挖条件下的破坏模式主要为坍塌破坏、坍塌—滑移破坏、滑塌破坏。结合顺层岩质边坡坍塌破坏模式渐进破坏的特点，以固端梁结构作为力学模型进行顺层岩质边坡的稳定性分析，即通过计算开挖区上方岩体坍塌高度，并与开挖区上覆岩体厚度比较，计算潜在滑体的下滑力与抗滑力并判断潜在滑体的稳定性，进而建立了不同破坏模式下对应的安全系数的计算方法。. (2)基于经典梁理论，考虑剪切方向与锚杆夹角β≤90º和β>90º种情形，假定剪切变形段受压侧岩体作用反力沿锚杆方向呈抛物线分布，建立了剪切方向与锚杆倾向共面条件下的力学分析模型。综合考虑结构面处锚杆的轴向变形、挠曲变形、位移变分、变形协调关系、临界锚固状态以及剪切变形段长度，得出了锚杆抗剪力计算公式，通过室内直剪试验锚杆抗剪力实测值与理论公式计算值进行对比分析，并结合锚杆的剪切变形情况，验证了加锚结构面力学分析模型的可行性。基于综合考虑锚杆轴向作用力和横向作用力的锚杆数值模型，采用FISH语言嵌入通用离散元软件UDEC中，针对某顺层岩质边坡，分析了锚杆长度、锚固角、锚杆间距和布设方式对边坡稳定性的影响，并基于正交试验提出了锚固优化方案。