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盾构地中对接冻结加固过程中形成不规则形状的冻结体,产生的冻胀效应会引起上部地层产生不均匀冻胀变形。为了获得冻结过程中冻胀效应对上部地层变形的影响规律,以上海地区软土地层中盾构地中对接冻结工程为原型,按照相似理论,设计进行了盾构对接位置地层冻结加固的模型试验,获得了如下结论:冻结过程中,冻胀引起上部地层的变形量随着冻结壁厚度的增长而线性增大,当冻结壁发展超过测点位置后,相应位置的地层变形不再变化。冻结产生的冻胀力对上部地层有压缩作用,随着地层内测点埋深的增加,地层变形量和地层平均应变都逐渐增大。当冻胀力超过土层的黏聚力后,上部土层的滑动使地层平均应变不再增加,地层不再被压缩,下部地层的变形会直接传递到上部地层。研究结果表明,影响冻结加固体上部地层变形量的主要因素是冻结壁的厚度,次要因素是地层的埋深。
In the shield ground, the irregular shaped frozen body is formed during the process of butting and freezing, and the frost heaving effect generated in the frozen ground will cause uneven frost heave deformation in the upper strata. In order to obtain the influence law of frost heave on deformation of upper strata in freezing process, taking the docking freezing project in shield ground of soft ground in Shanghai as the prototype, according to the similarity theory, the model test of stratification freezing reinforcement at shield docking position was designed , We get the following conclusions: During the freezing process, the deformation of the upper formation caused by frost heave increases linearly with the increase of the freezing wall thickness. When the frozen wall develops beyond the measuring point, the deformation of the corresponding layer does not change any more. The frost heaving force produced by the freezing has a compressive effect on the upper strata. As the depth of the measuring point in the strata increases, the deformation of the strata and the average strata strain gradually increase. When the frost heaving force exceeds the cohesion of the soil layer, the sliding of the upper soil layer will not increase the average strain of the strata, the strata will no longer be compressed, and the deformation of the lower strata will be directly transmitted to the upper strata. The results show that the main factor affecting the deformation of the upper frozen layer is the thickness of the frozen wall, and the secondary factor is the depth of the formation.