高地应力软弱围岩大变形及锚注加固机理的FDEM模拟研究

The soft and weak ground under high overburden and geostress is prone to be with large deformation during tunneling process, which usually leads to severe fractuation and continual deformation of the rock mass. Based on the combined finite-discrete element method (FDEM), laboratory tests and field observation, this project will do thorough research works on the large deformation mechanism of soft and weak ground, as well as the reinforcement mechanism of anchoring and grouting to fractured rock mass. Firstly, through the triaxial test of soft and weak rock and direct shear test of anchored and grouted jointed rock mass, the post-peak damage softening constitutive model of soft and weak rock, the bolt-rock interactive model and the cohesive model of grouted rock mass will be proposed, and then numerical algorithms will be generated for the investigation of crack initiation and propagation in soft and weak rock and the anchoring and grouting reinforcement simulation of jointed rock. Then, an efficient contact search algorithm suitable for the highly uneven sized elements will be proposed, and the CUDA (Compute Unified Device Architecture) based high performance parallel computing platform for FDEM will be established. Finally, by considering the softening effect of the rock strength over time, the revolution law of stress field, displacement field and fracture network in the deep-buried ground during the large deformation process will be revealed. Meanwhile, based on the modeling of the crack initiation, propagation, fracturing and expanding process of rock mass, the large deformation mechanism will be revealed, and the large deformation assessment approach and surrounding rock mass deformation prediction approach will be proposed. Additionally, the effect of different anchoring and grouting modes on the fracturing process of soft and weak rock mass will be investigated, and the large deformation control technology of deep-buried soft ground will be proposed.

高地应力软弱围岩极易产生大变形灾害，表现为岩体严重破碎及持续变形，最终导致洞壁位移极大和支护措施失效。本项目拟基于有限元—离散元耦合方法，结合室内试验和现场观测，深入研究软弱围岩大变形发生机理及锚固、注浆对破碎围岩体系的加固机制。首先，通过软弱岩石三轴压缩及加锚、注浆节理剪切实验，提出软弱岩石峰后损伤软化本构模型，构建锚杆—岩石相互作用和注浆粘结作用数值模型，进而生成软弱岩石裂纹孕育发展过程及岩石节理锚注加固模拟算法；然后，提出适于高度非均匀尺寸单元的高效接触搜索算法，并研发有限元—离散元耦合方法高性能并行计算平台；最后，考虑岩石强度随时间劣化，模拟研究深埋软岩大变形过程中应力场、位移场和裂隙网络演化规律，基于岩石破裂碎胀过程揭示大变形发生机理，提出大变形评价和围岩位移定量预测方法，模拟研究不同锚注方式对软弱围岩破裂演化过程的影响机制，优化软岩大变形锚注支护设计。

随着我国经济、社会快速发展，当前很多矿山、水利和交通岩土工程的埋深都超过了千米。深部围岩常面临地应力高和围岩自身强度低的突出矛盾，工程开挖卸载扰动后，洞室表面附近围岩迅速破裂，裂隙由表及里的扩展和贯通将围岩切割成高度破碎体系，围岩自身承载能力极大下降并产生显著的收敛位移甚至失稳灾变。上述软弱围岩破裂碎胀大变形灾害造成了大量工程建设的工期延误和经济损失，严重制约了深部地下工程的发展。大变形过程中，被既有不连续面和破裂面分割的围岩块体可能相互挤压、分离、转动和滑移，甚至进一步破裂运动，使得破碎围岩体系力学响应非常复杂。这一渐进破坏、变形过程难以通过理论解析和室内试验定量描述。由于在模拟研究岩石渐进破坏过程方面具有独特优势，有限元-离散元耦合方法（FDEM）可作为模拟研究软弱围岩大变形问题的有力工具。本研究基于FDEM方法对围岩破裂演化过程以及破碎围岩体系大变形进行了模拟研究，揭示了高地应力软弱围岩大变形的发生机理及常规支护的破坏机制，提出了大软岩变形支护的优化思路，并创新性探索了一种新的无网格法，具体研究内容如下：.（1） 开展了多种岩石的力学实验，基于测试结果分析了岩石细观参数与宏观参数之间的相互关系以及细观参数对宏观响应的影响。在此基础上发展了FDEM输入参数标定流程，相比现有标定流程提高了标定精度和效率。.（2）建立了基于实体单元建模方案的光滑锚杆模型，可以很好地表征粘结荷载-滑移曲线和加载速率的作用规律。.（3）开发了FDEM方法基于CUDA平台的GPU并行计算程序，在此基础上进一步提出了适于高度非均匀尺寸单元的高效接触搜索算法、新接触判断算法和接触力算法，并在并行程序中实现，使模拟平台的计算速度得到极大提升。.（4）考虑岩石强度随时间劣化，模拟研究了深部软岩大变形过程中应力场、位移场和裂隙网络演化规律。基于岩石破裂碎胀过程研究揭示了软岩大变形发生机理和支护条件对软岩破裂演化过程的影响机制，提出了优化应对软岩大变形支护设计的建议。.（5）提出了通过位移的方向导数积分表征应变并计算应力的方法，提出了通过局部节点位移和径向基函数插值建立局部位移场方法，给出了平衡条件的等效提法，提出了一种新的无网格方法并开发了这种方法的GPU并行程序。.上述研究可显著提高大规模工程灾害数值模拟的精度和效率，对深部软岩大变形机理认识和支护设计具有重要现实意义。