富水砂岩隧道垂直冻结法施工效果数值分析

Numerical analysis on construction effect of vertical freezing method for water-rich sandstone tunnel

依托一新建铁路工程隧道,采用数值模拟的方法,分析了富水砂质地层中大埋深铁路隧道垂直冻结法施工的效果。结果表明:在垂直冻结的前60 d,冻结管产生冻结交圈,但交圈程度存在间隙,土体温度处于-4~-8℃,交圈受施工影响容易受热融化;当垂直冻结117 d后,土体冻结效果明显,冻结壁长度为57.0 m,宽度达到了16.7 m,温度达到-16℃,呈大范围连续分布,此时进行隧道的开挖施工能够较好地保证围岩处于稳定状态;垂直冻结后,围岩的最大强度发挥系数由未冻结前的1.305(塑性区贯通)减小到冻结后的0.300(只在仰拱脚处局部存在塑性),说明在富水砂岩地层中,采用垂直冻结法施工的效果明显,能够有效保证围岩的稳定性。研究成果可为同类型地层中隧道的施工提供参考。

Relying on the newly built Chengershan tunnel on Yuanzhou-Wangwa railway,the construction effect of vertical freezing method applied in mountain railway tunnel with large embedded depth in water-rich sandstone stratum was analyzed by numerical simulation.The results showed that 60 days after conducting vertical freezing,the freezing overlap occurred in freezing pipes with some gaps,and soil temperature was -4~-8℃,so the overlap was easy to melt under influence of construction.After 117 days of vertical freezing,the frozen effect was obvious with frozen wall length of 57 m and width of 16.70 m,and soil temperature reached -16℃ with a continuously distribution in a large range.Under this condition,the construction can be better ensured.By applying vertical freezing,the maximum effective strength coefficient of surrounding rock decreased from 1.305(plastic zone breakthrough)to 0.300(local plasticity only at inverted arch foot).It shows that the retaining effect of vertical freezing method is obvious in water-rich sandstone stratum,which can effectively ensure the stability of surrounding rock.The study can provide reference for tunnel construction in the same type of stratum.