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隧道水平冻结施工过程中,土体冻结引起体积膨胀,进而会在地表产生冻胀现象。实际工程一般采用多根冻结管形成冻结壁。冻结壁交圈前,地表冻胀由多个冻土柱的叠加膨胀变形引起;冻结壁交圈后,地表冻胀则由整个冻结壁的膨胀变形引起。鉴于此,考虑冻结壁的形成过程,基于随机介质理论,建立了隧道水平冻结施工引起地表冻胀位移的历时预测模型。同时对冻结外锋面半径和冻胀区域外半径这2个关键参数的取值方法进行了相关探讨。最后针对两个工程案例,采用该计算模型对地表冻胀位移进行分析,得到地表冻胀位移随时间的变化规律,并与现场实测结果相比较,验证了模型的可靠性。该模型应用于隧道水平冻结施工前、冻结期内任意时刻的地表冻胀位移预测,可为工程冻结实施方案的合理确定提供有效依据。
During the horizontal freezing of the tunnel construction, soil freezing causes volume expansion, which in turn causes frost heave on the surface. The actual project generally uses a number of frozen tubes to form a frozen wall. Before freezing circle, the frost heave of the surface is caused by the superposition and expansion deformation of a large number of frozen soil columns. After frozen circle intersects, the frost heave of the surface is caused by the expansion and deformation of the frozen wall. In view of this, considering the formation process of the frozen wall, based on the stochastic medium theory, a time-lapse prediction model of surface frost heave and displacement caused by horizontal freezing construction in the tunnel is established. At the same time, the methods to determine the value of the two key parameters such as the outer frontal radius and the outer radius of the frost heave zone are discussed. Finally, according to two engineering cases, this model is used to analyze the frost heave and displacement of the ground surface, and the variation of surface frost heave and displacement with time is obtained. The reliability of the model is verified by comparison with the field test results. The model can be used to predict the surface frost heave and displacement at any time during the freezing period before the horizontal freezing construction of the tunnel, which can provide an effective basis for the reasonable determination of the project freezing implementation.