基于破碎冻融圈的寒区隧道冻胀模型及影响因素分析

On Frost-Heave Calculation Model Based on a Broken Freeze-Thaw Circle and Its Influential Factors

冻胀力是寒区隧道病害的主要影响因素之一,研究冻胀力量值和分布对寒区隧道保温设计具有重要意义。文章分析总结了目前几种冻胀模型和冻胀机理,在风化层冻胀模型的基础上建立了破碎圈冻胀模型,根据位移连续条件推导了冻胀力计算公式,采用控制变量法分析了冻胀力与影响因素关系,并用偏相关分析方法分析了各因素对冻胀力影响大小。研究结果表明:冻胀力量值与冻结深度、冻融圈冻胀率、衬砌及原始围岩的抗力系数有关;冻融圈冻胀率与破碎程度、含水率及水源补给条件密切相关;各因素对冻胀力影响关系为:冻结深度>冻融圈冻胀率>衬砌弹性当量抗力系数。根据工程实例计算,当冻结深度为2~3 m时冻胀力量值为7.43~11.05 MPa之间,计算值偏大于实测值。最后依据冻胀力影响因素讨论了防治冻胀力的工程措施,可为寒区隧道保温设计与施工提供借鉴。

The force created by frost heaves is one of the major influential factors for tunnels in cold regions, and it is very important to study this frost-heave force. Several kinds of calculation models and mechanisms for this frost-heave force are analyzed and summarized, and a model of frost heaving in a broken freeze-thaw circle is established based on a frost-heaving model for a weathered layer. A frost-heave force calculation formula is deduced according to displacement continuity conditions, the relation of frost-heave force and influential factors are analyzed by the control variable method, and the influence of different factors on the frost-heave force are analyzed by the partial correlation method. The results show that： 1） the frost-heave force value is related to the frozen depth, the frost- heave ratio of the freeze-thaw circle, the lining and the resistance coefficient of the original rock mass; 2） the frost- heave ratio of the freeze-thaw circle has a close relationship to the degree of breakage, moisture content and water supply conditions; 3） the orders of effects of various factors on the frost-heave force are： the frozen depth 〉 the frost- heave ratio of the freeze-thaw circle 〉 the elastic equivalent resistance coefficient of lining. A case calculation shows that the frost-heave force scope is 7.43-11.05 MPa when the frozen depth is 2～3 m, and the calculated frost- heave force is larger than that of the measured values. Countermeasures to mitigate the frost-heave force are discussed based on influential factors.