It is essential to better understand the large deformation behavior of deep tunnels in weak rock mass to improve the long-term stability of tunnel surrounding rock mass and design effective supports for squeezing tunnels. This paper introduces two representative large deformation engineering examples to study squeezing behavior. First, new algorithms of contact search, determination of actual contact, and calculation law of contact pairs are proposed for general-purpose computing on graphics processing units (GPGPUs), by improving the original serial algorithms and developing a compute unified device architecture (CUDA) parallel program, to satisfy the large-scale rock fracture process simulation. Then, tunnels excavation and rock reinforcement effect including the combination of U-shaped steel and steel fabric, spray concrete (SMC), and grouting were modeled. The verification, done by comparing the field observation data and the FDEM simulation results of progressive fracture and the tunnel wall convergence displacement, shows that stress remarkable rebalancing after excavation because of high in situ stress, low rock mass strength, and rock mass long-term strength reduction properties, thus, the rock mass fracture progressively and the rock blocks move continuously, leading to the rock mass volume increase significantly. The result demonstrates one of the root causes of squeezing. To effectively reduce the tunnel wall displacement and maintain tunnel stability, support with higher stiffness or multifactorial combined support methods and grouting with a better bonding effect should be used together. The findings provide insights into the progress of tunnel squeezing and the basis for support design in the squeezing tunnel.

中文翻译：

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基于GPGPU并行FDEM的岩体破裂诱发隧道超大变形

深入了解软弱岩体中深部隧道的大变形行为，提高隧道围岩的长期稳定性，设计有效的挤压隧道支护，对提高隧道围岩长期稳定性至关重要。本文介绍了两个具有代表性的大变形工程实例来研究挤压行为。首先，通过改进原始串行算法并开发计算统一设备架构（CUDA），提出了用于图形处理单元（GPGPU）上的通用计算的接触搜索、实际接触确定和接触对计算规律的新算法。并行程序，满足大规模岩石断裂过程模拟。然后，隧道开挖和岩石加固效果包括U型钢和钢织物的组合，喷射混凝土（SMC），和灌浆进行了建模。对比现场观测资料和渐进式裂缝及隧道壁收敛位移的FDEM模拟结果，验证表明，由于地应力高、岩体强度低、岩体长期处于开挖状态，开挖后应力再平衡显着。强度降低特性，因此，岩体逐渐断裂，岩块不断运动，导致岩体体积显着增加。结果证明了挤压的根本原因之一。为有效减少隧道墙体位移，保持隧道稳定性，应采用刚度较高的支护或多因素组合支护方式与粘结效果较好的注浆配合使用。