浅覆土下矩形冻结加固的模型试验研究

为获得浅覆土下矩形冻结加固体的温度场分布及冻胀变形规律，以广州地铁6号线穿越3号线的冻结工程为原型，根据相似理论，设计进行了水平冻结的模型试验。结果表明，在地表散热的影响下浅埋冻结工程中紧邻地表的冻结区域降温速度较慢，形成的冻结壁是整个加固体的薄弱环节；冻结过程中冻结壁向内发展较快，其平均发展速度是向外发展速度的1.5倍左右；形成封闭的冻结壁前，采用较高的盐水温度进行冻结，可有效地控制土体的冻胀变形，冻结壁封闭后，降低盐水温度，冻胀变形会明显增加；冻胀过程中产生的冻胀力对上部土层有压密作用，使土层的冻胀变形随着埋深的变浅而减小；对于浅埋矩形地下冻结工程，上部覆土和冻结加固体之间相互影响作用明显，上部土层的散热会影响冻结加固体内温度场的分布规律，而下部冻土的冻胀作用也会压密上部土层。

Model test of artificial ground freezing in shallow-buried rectangular cemented soil

In order to obtain the temperature distribution and frost deformation law of frozen wall, the shallow-buried rectangular freezing engineering, which is a construction of the line 3 to cross line 6 in Guangzhou metro, was studied through the model test based on similarity theory. Conclusions are drawn as follows. Firstly, the temperature of the soil closed to the ground surface drops slowly under the influence of ground heat dissipation in shallow-buried freezing engineering .And the frozen wall closed to the ground surface is relatively weak. In the process of freezing, the average development speed of internal frozen wall is about 1.5 times that of the outward frozen wall. Secondly, small amount of frost heaving deformation is generated in the initial freezing stage. The freezing construction is proceeding with high-temperature brine; and the closed frozen wall is not formed at this stage. Thirdly, when the frozen wall is closed, the frost deformation of frozen wall increases obviously at the time of the freezing construction with low-temperature brine. In general, the soil frost heave deformation tends to decrease when the soil layer depth becomes smaller because the upper soil layer is compacted. There is significant interaction effect between the upper shallow covering and frozen wall in shallow-buried rectangular freezing engineering. This implies that the upper soil layer, which will produce deformation in the advance of the freezing process, will affect the temperature field distribution in frozen wall.