局部差异冻结作用于既有井壁的冻胀力研究

Study on frost heaving force of local differential freezing technology acting on existing shaft wall

针对板集矿副井井筒局部差异冻结修复的工程问题,使用ABAQUS/Standard数值分析软件,结合冻土试验得到热、力学参数,建立局部差异冻结条件下土体热—力耦合模型并进行有限元分析,分析了冻结172 d内土体冻结温度场的分布状况,研究了外层井壁位置处冻胀力的发展变化规律,并对井筒进行安全性评价。结果表明:-300 m层位交圈时间较-450 m层位晚22 d,冻结壁平均温度较-450 m层位高5.2℃;两层位冻胀力自冻结30 d起呈现出线性增长趋势,在交圈后的14 d内有阶跃性增长,其后冻胀力增长速度放缓,各方位上冻胀力总体呈现类同心圆的发展形式。172 d时,-300 m层位冻胀力占初始地应力的17.94%;同期-450 m层位冻胀力占初始地应力的41.54%。井壁混凝土的最大环向应变值与等效应力值均在准许范围内,表明既有井壁仍处于弹性受力阶段,井筒安全可靠。由此可见,局部差异冻结技术可以有效控制冻结壁向内发展速度,限制土体冻胀,避免对井壁造成二次破坏,该项施工技术可为今后类似工程的开展提供重要参考。

To solve the engineering problem of the repairing of local different freezing in the auxiliary shaft in Banji Mine,the ABAQUS/Standard Numerical Analysis Software was used.Combined with the thermal and mechanical parameters obtained in the test of frozen soil,the coupled thermo-mechanical model of the soil body under the condition of local different freezing was built and the finite element analysis was made.The distribution of the freezing temperature field of the soil body in 172 days of freezing was analyzed.The development and change rules of the frost heaving force in the position of the outer wall of the well were studied.The safety evaluation was made on the shaft.The results showed that the closing time of the horizon of-300 m was 22 days later than that of the horizon of-450 m.The average temperature of frozen wall at the horizon of-300 m was 5.2℃higher than that of the horizon of-450 m.The frost heaving force of the 2 horizons had a linear growth trend since 30 days after the freezing.Within 14 days after closing,it grew greatly.After that,the growth rate of the frost heaving force decreased.The frost heaving forces in each direction had the development form of quasi-concentric circles.After 172 days,the frost heaving force at the horizon of-300 m accounted for 17.94%of the initial crustal stress.In the same period,the frost heaving force at the horizon of-450 m accounted for 41.54%of the initial crustal stress.The maximum circumferential strain value and equivalent stress value of concrete on the shaft wall were within the permitted scope,indicating that the existing shaft well was still in the stage of elastic stress and the shaft was safe and reliable.Thus,it can be seen that the local different freezing technology can effectively control the inward development speed of the freezing wall,restrict the frost heaving of the soil body,and avoid the second damage to the wall of the well.This construction technology can provide an important reference for similar projects in the future.