软岩隧道支护让压体系优化及安全状态易损性评价

Optimization of Yield-Control Support System and Vulnerability Evaluation of Soft Rock Tunnel

摘要:

软岩隧道围岩参数变异性大，支护体系与围岩相互作用不确定性强，易发生大变形等安全问题，为此国内外开展了隧道让压支护优化等工作以应对上述风险，但对其安全状态评价仍面临诸多难题。设计了一种新型柔-刚型让压接头，并基于可靠度分析方法，从易损性出发，综合拱顶沉降及初衬强度破坏准则，提出了基于概率的隧道开挖安全状态易损性评价方法。其通过利用概率有限元分析围岩?支护相互作用，拟合形成极限状态功能函数响应面，经由随机抽样获得隧道开挖失效概率与可靠度指标；以此为基础，建立拱顶沉降与结构应力响应之间的拟合关系，提出了基于拱顶沉降的结构极限状态条件概率计算方法，并根据概率分布区间划定易损区进行支护安全性评价。基于上述理论方法，结合工程实际，开展了新型让压支护与传统刚性支护的易损性对比分析，验证了让压支护体系在大变形承载可靠性方面的优势。

Abstract:

During the soft rock tunnel excavation， large deformation is easy to occur because the parameters of surrounding soft rock are highly variable， the stress of support system and its interaction with surrounding rock are highly uncertain. Therefore， the yield-control support system is studied both domestically and internationally to address these risks. However， there are still many difficulties in evaluating its safety status. In this paper， a new type of flexible rigid yielding joint is designed， and a vulnerability evaluation method of tunnel excavation safety status based on probability is proposed， which combines of the reliability and vulnerability analysis method and vault settlement failure criteria. In detail， by analyzing the interaction between surrounding rock and support with probabilistic finite element method， the support response of limit state function is fitted， and the failure probability and reliability index of tunnel excavation are obtained by random sampling， based on which， the fitting relationship between vault settlement and structural stress response is established， the calculation method of exceedance probability of structural limit state conditions based on vault settlement is proposed， and the vulnerable area is delimited according to the probability distribution for support safety evaluation. The reliability of the new support system is verified based on the comparison between the traditional support system and the rigid support system.