低温岩体裂隙冻胀力与冻胀扩展试验初探

低温裂隙岩体冻融损伤与断裂破坏一直是寒区岩体工程建设中的关键科学问题。低温下含水裂隙的冻胀扩展演化过程受冻胀力量值的控制，然而裂隙中冻胀力的大小及其演化机制一直存在争议，尚缺乏有效的试验测试方法。通过在类岩石材料中预制不同长度和宽度的宏观裂隙，进行了低温下饱和裂隙的冻胀力测试试验；利用薄膜压力传感器和温度传感器分别对饱和裂隙在低温冻结过程中的冻胀力和冻结温度进行了实时连续的监测，获取了其时空演化曲线。试验结果表明：（1）在冻结过程中，岩体裂隙中冻胀力的萌生是一个突发的过程，其演化过程可分为孕育阶段、爆发阶段、跌落阶段以及平衡阶段；（2）冻结完成后，裂隙冰发生了明显的挤出且裂隙尖端产生了可见的冻胀裂纹；（3）融化过程中，冻胀力跌落较快，但存在滞后现象；（4）对于宽度在2～5 mm范围内的半开口裂隙，从裂隙开口端冻结时，最大冻胀力与裂隙宽度线性正相关；在宽度为5 mm的饱和裂隙中最大冻胀力达到了7.2 MPa。研究成果可为认识裂隙中冻胀力的萌生演化机制以及进行裂隙冻胀扩展计算与分析提供借鉴。

Preliminary experimental study of frost heaving pressure in crack and frost heaving propagation in rock mass under low temperature

Freeze-thaw damage and rupture failure of fractured rock mass under low temperature are the key scientific problems for the construction of rock engineering in cold regions. Frost heaving pressure produced in saturated crack is a controlling factor that induces crack frost propagation. However, the magnitude and evolution law of frost heaving pressure are controversial due to the difficulty in conducting tests. By prefabricating macroscopic crack with different geometries in rock-like material, a laboratory test of frost heaving pressure in saturated cracks is conducted. A thin film pressure sensor is used to test the evolution process of frost heaving pressure in cracks and the temperature on the surface of rock is continuously monitored by several temperature sensors. Based on the results, the space-time evolution curves of frost heaving pressure in cracks are derived. The experimental results show that: 1) In freezing process, the initiation of frost heaving pressure in crack suddenly occurs, and the entire evolution process of this pressure can be divided into embryonic stage, outburst stage, falling stage and balance stage. 2) In frozen process, the ice in crack has been extruded and new visible propagation cracks are produced in tips of the cracks. 3) In melting process, the frost heaving pressure falls quickly but lags behind the freezing point. 4) For a half open fracture with a width ranging between 2?5 mm, when water starts freezing at the open end, the maximum frost heaving pressure linearly increases with the increasing of crack width. The pressure is more than 7.2 MPa in saturated crack with a width of 5 mm. Research results presented in this paper can provide reference for understanding the evolution mechanism of frost heaving pressure and studying the crack propagation caused by frost heave.