云母片岩地层大变形隧道砂浆锚杆失效力学机制研究

Large-scale of metamorphic strata is very common in underground engineering construction of transportation、mining、water-hydroelectric projects and other engineering fields, especially in mica schist, which has the characteristic of well-developed foliation, low strength, wide distribution. When tunnel cross mica schist, inevitably lead to the failure of anchor support, large deformation and collapse of surrounding rocks and other bad geological phenomenon. The difficulty of excavation and supporting will be increased, and the construction safety and the long-term stability of the tunnel will be impacted seriously.. Laboratory and in-situ test with theorical analysis are utilized to obtain the failure pattern and shape of tunnel anchors The anchor-rock mechanical model is built up to reflect the stress-strain characteristics of anchored surrounding rocks on the basis of understanding the load-stress-strain features among surrounding rocks, grouting bodies and anchors in different locations. It is progressive failure procedure and physical phenomenon of surrounding rocks, grouting bodies and anchors that are studied to expose the mechanical evolutionary process of anchors in the whole-length scale. In addition, the influence factors of anchor failure with the mechanism are confirmed to put forward the improvement methods aiming at the tunnel anchors in schist layers. The research results can be of significance for enriching the anchor supporting theory and it is useful for the application of anchor-shotcrete supporting design and the geo-hazard prevention in tunnels of weak surrounding rocks.

在交通运输、矿山开采、水利水电等工程领域中的地下工程建设中，常遇到大规模的变质岩地层，其中云母片岩片理发育、强度低、分布广，在隧道施工过程中常出现锚杆失效、大变形和坍塌等隧道不良地质现象，开挖支护难度大，严重影响工程安全及隧道的长期稳定性。本项目采用室内外试验及理论分析的综合手段，研究锚杆失效宏观规律；获取锚杆与围岩在不同空间组合下，围岩体、灌浆体及锚杆的荷载-应力-应变特征，构建反映加锚岩体应力应变特征的锚-岩力学模型，提出数值实现方法；研究不同工况下围岩体、灌浆体及锚杆的渐进破坏过程及其物理特征，锚杆全长范围内力学演化过程，厘定锚杆失效影响因素及其作用的力学机制，提出改善云母片岩地层隧道锚杆失效的控制措施。项目研究成果对锚杆加固效应理论的丰富和完善具有重要意义，对软弱围岩隧道锚喷支护结构设计与防灾减灾具有良好的应用价值和广阔前景。

在交通运输、矿山开采、水利水电等工程领域中的地下工程建设中，常遇到大范围的变质岩地层，其中的云母片岩片理发育、强度低、分布广，在隧道施工过程中常出现锚杆失效、大变形和坍塌等隧道不良地质现象，开挖支护难度大，严重影响工程施工安全及隧道的长期稳定。本项目以鄂西北地区典型云母片岩隧道为例，调查分析发现该地层砂浆锚杆失效模式主要表现为锚杆杆体的滑脱，砂浆和杆体之间的粘结失效；采用监控量测手段从围岩压力、围岩变形及塑性区分布等方面分析了锚固失效区大小、空间形态特征及其与片理面空间方位之间的关系；采用RMT-150岩石力学实验系统展开了片岩不同围压、不同片理面角度加载方向的单轴及三轴力学实验，揭示了云母片岩的强度和变形各向异性特征，以此建立了片岩横观各向同性强度准则和本构模型，提出了其数值实现方法。构建了反映加锚岩体应力应变特征的锚-岩力学模型，结合正交实验获取了加锚岩体在不同空间组合及参数布置条件下，围岩体、粘结体及锚杆的荷载-应力-应变特征，揭示了各单元的受力、变形及破坏模式。建立了加锚隧道围岩地质力学模型，针对锚固失效力学行为，从单因素和多因素交互组合两方面获得了锚固失效的影响因素及锚杆支护参数的敏感性；通过计算分析，阐明了围岩体、灌浆体及锚杆的渐进破坏过程及其物理特征，锚杆不同布置范围内变形及力学演化过程，揭示了锚杆失效的力学行为。针对锚杆受力特点提出了控制改善云母片岩地层隧道围岩变形的锚杆优化布置方案。项目研究成果初步揭示了云母片岩地层锚固失效演化规律和细观力学机制，对认识和控制复杂软弱地层隧道锚喷支护结构设计与防灾减灾等问题具有良好的意义。