基于多重响应面法和蒙特卡罗法的隧道系统可靠度分析

Analysis on the Reliability of Tunnel System Based on Multiple Response Surface Methodology and Monte Carlo Method

软岩隧道施工风险大,且支护结构及施工过程复杂,导致难以直接求得隧道结构的极限状态函数。基于此,文章讨论了一种利用有限元数值模拟结合多重响应面法和蒙特卡罗法分析隧道结构系统可靠度的方法。以青岛某地铁区间软岩隧道为例,验证了其适用性。结果表明:对于围岩“上软下硬”且上下岩性相差很大的隧道工程,其系统失效概率主要受上部软弱围岩影响,下部较硬岩土体几乎不影响隧道结构的系统失效概率;改变卵石层弹性模量E1和内摩擦角φ1的变异系数对系统失效概率的影响最为明显,隧道系统失效概率随围岩参数变异性的增大而增大;由于失效模式之间存在相关性,单一考虑隧道变形超限失效或者支护承载力不足失效是不充分的,以变形和承载能力为控制条件的多种失效模式相结合的系统可靠度研究更适合软岩隧道结构。

As soft rock tunnels have the disadvantages of high construction risk and high complexity of support structure and construction process,it is difficult to directly calculate the limit state function of tunnel structure.So,this paper discusses an analysis method for the reliability of the tunnel system using finite element numerical simulation in combination with multiple response surface methodology and Monte Carlo method.Its suitability was verified in the case of one soft rock subway tunnel in Qingdao.The results showed that the surrounding rock characterized by"soft upper ground and hard lower ground"had a very large difference in lithology between the upper and lower parts,and the system failure probability of tunnel structure was mainly affected by the upper soft rock and rarely affected by the lower hard one;a change in the elastic modulus(E1)and internal friction angle(φ1)of pebble bed had the most significant impact on the system failure probability,and the tunnel system failure probability increased with the increasing of parameter variability of surrounding rock;due to the relevance between failure modes,it is not adequate only to take into consideration the failure of out-of-limit tunnel deformation or insufficient support bearing capacity,while the system reliability study based on multiple failure modes using deformation and bearing capacity as the controlling conditions was more suitable for the soft rock tunnel structure.