基于精细化数值模拟的地铁盾构隧道椭圆度安全研究

Research on Ellipticity Safety of Metro Shield Tunnel Based on Refined Numerical Simulation

随着城市地铁运营里程不断增长,盾构隧道过量变形导致的结构安全问题持续出现。对出现过大变形的盾构隧道进行结构分析时,准确的岩土参数难以获取且外部因素十分复杂,在数值模拟中难以全面考虑。以可靠的实测数据作为精细化数值模拟分析的基础,更有利于还原当前的结构状态。因此,为更真实地通过数值模拟方法分析盾构隧道的结构安全状况,继而得出基于椭圆度的结构安全控制标准,提出以隧道椭圆度为基准,在保证隧道结构合理的受荷条件下使隧道变形结果与实际相近,结合某上软下硬地层中隧道变形过大的典型案例相互论证,从而进行盾构隧道的结构力学响应分析。研究结果表明:当隧道结构主要承受竖向对称荷载时,拱顶接头位置变形与螺栓应力最大;拱顶内侧易出现裂缝,拱腰接缝区域容易出现渗漏;管片椭圆度为0~10‰时,结构较安全;椭圆度在10%~20‰时,结构拱顶内侧开始出现塑性区;椭圆度在20%~30‰时,塑性区不断发展,拱顶螺栓接近进入屈服阶段;通过对比管片损伤、螺栓应力、接缝张开量等随椭圆度增加的变化,结合工程案例中的实际状况,并考虑为隧道结构变形保留适当冗余,可将该区间隧道基于椭圆度判断的变形标准的控制值设为25‰,预警值设为20‰。

With the continuous expansion of urban metro operating mileage,structural safety issues caused by excessive deformation of shield tunnels are increasingly emerging.When conducting structural analysis on shield tunnels that have experienced significant deformation,it is challenging to obtain accurate geotechnical parameters and fully account for complex external factors in numerical simulations.Using reliable measured data as the basis for refined numerical simulation analysis is better suited to accurately reflecting the current structural state.Therefore,to analyze the structural safety of shield tunnels more realistically through numerical simulation and subsequently establish a structural safety control standard based on ellipticity,this study proposed using tunnel ellipticity as a benchmark.Under the premise of ensuring reasonable loading conditions on tunnel structure,the deformation results of the tunnel should closely match the actual situation.The study tested this approach with a typical case of excessive tunnel deformation in a soft upper and hard lower stratum and then analyzed the structural mechanical response of shield tunnels.The results showed that when the tunnel structure was mainly subjected to symmetrical vertical loads,the deformation and bolt stress were the greatest at the vault joint.Cracks were likely to appear on the inner side of the vault,and leaks were prone to occur in the arch waist joint.The structure was relatively safe when the segment ellipticity was between 0~10‰.When ellipticity was between 10‰~20‰,a plastic zone started to appear inside the vault.When ellipticity was between 20‰~30‰,the plastic zone continued to extend,and the bolts at the vault approached the yielding stage.By comparing the changes of segment damage,bolt stresses and joint opening with the increase of ellipticity,and considering the actual situation in engineering cases while allowing for appropriate redundancy in tunnel deformation,the deformation control value based on ellipticity for tunnels in this range could be set at 25‰,with the warning value of 20‰.