地铁联络通道冻结法施工中涌水成因及防治

以某富水砂卵石地层联络通道人工冻结法施工为依托,就地层热力学参数、冻结参数和施工工艺等对冻结壁的厚度、交圈时间及平均温度等影响进行了研究,分析表明:AGF冻结效果关于热传导系数的敏感度最大,关于比热容和含水率的敏感度次之;冷冻管间距对冻结效果的影响非常显著,冻结法施工时,应加强冻结管开孔位置及倾斜度的控制;冷冻管直径变大,盐水与地层间对流系数减小,会抵消冻结管直径增大的影响;保温层设置不当以及冻结管远端定位缺陷直接影响联络通道与盾构隧道交叉区域的冻结效果,甚至出现冻结壁厚度不足和冻结壁交圈困难等问题,易导致管片开挖时涌水事故的发生。

The Causes and Prevention Measures of Water Inflow at Cross Passage Located in Sandy Gravel Layers and Constructed by Artificial Ground Freezing

Taking the construction of artificial ground freezing of cross passage located in sandy gravel layers as analysis case, the effect of thermal properties of soil, in addition to design parameters and construction measures, on the width, as well as the closure time and the average temperature, of frozen bodies were analyzed. It shows that the sensitivity of width of frozen bodies on heat conductivity is greater than on the heat capacity and water content. The space between freeze pipes play a significant role in the closure of frozen bodies. As a result, much attention should be paid to the precision control of the starting position and inclination angle of the freeze pipes in the AGF construction. The sensitivity of freeze pipe dimensions is also investigated, and there may be a small benefit to increasing the diameter of the freeze pipe. The construction defects of thermal insulation material and freeze pipes positioning could affect substantially the closure of the frozen bodies at the intersection of shield tunnel and cross passage, which results in the water inflow when the opening and excavating of shield segment start.