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

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.

Key words:soft rock;support;yield-control support;probability;vulnerability evaluation