基于数值模拟与实测数据拟合的高地应力软岩隧道二次衬砌施作时机探讨

Discussion on the Timing for the Secondary Lining Construction in Soft Ground Tunnels with High Geostress Based on Numerical Simulation and Measured Data Fitting

铁路隧道高地应力软岩大变形控制一直是施工中的难题,由于其变形规律、变形时间的不确定性及变形机理的复杂性,在高地应力环境下何时施作二次衬砌一直困扰着施工人员。为此,结合现场的实测数据和数值模拟研究的大变形规律,对高地应力软岩隧道二次衬砌施作时机进行探讨,研究结果表明:(1)二次衬砌施作的最佳时机要尽可能采用变形量和变形速率双控的方式确定,尤其在严重、极严重变形段,要确保变形量达到了预估变形量的95%,且拱顶下沉速率不大于0.4 mm/d,边墙收敛速率不大于0.6 mm/d时才能施作二次衬砌;(2)指数函数拟合变形时程曲线相关性高,考虑到隧道围岩的复杂性、施工参数的不确定性及测量数据的误差性,采用某一个特定的参数对所有隧道进行变形曲线拟合是不可行的;(3)在分析大变形隧道二次衬砌施作时机时,蠕变参数的选择需要根据地层岩性、相近地层量测成果综合考虑。

The large deformation control for soft ground with high geostress in the railway tunnel is always a difficult problem in construction. Due to the uncertainty about deformation pattern and deformation time and the complexity of deformation mechanism, the timing for constructing the secondary lining in a high geostress environment has been a problem for construction personnel. For this reason, the large deformation pattern was studied combined with measured field data and numerical simulation and the timing of the secondary lining construction of the high geostress soft ground tunnel was discussed. The study results show that(1) the optimal timing for the construction of the secondary lining should be determined by using the dual control method of amount of deformation and rate of deformation, especially severe and extremely severe deformation sections. The secondary lining cannot be constructed until the amount of deformation reaches 95% of the estimated amount of deformation, the rate of crown settlement does not exceed 0.4 mm/d, and the rate of convergence of sidewall does not exceed 0.6 mm/d;(2) The relevance of exponential function fitting and time-history curve of deformation is high. In view of the complexity of tunnel surrounding rock, uncertainty of construction parameters and errors in measured data, it is not feasible to use a particular parameter for deformation curve fitting of all tunnels;and(3) in the analysis of construction timing for the secondary lining of tunnels prone to large deformation, the selection of creep parameters should be comprehensively considered according to stratum lithology and measurement results of adjacent strata.