单向冻结条件下裂隙岩体冻胀特性试验

Experimental Study on Frost Heaving Characteristics of Fractured Rock Mass under Unidirectional Freezing Condition

摘要:

单向冻结条件下寒区隧道围岩不均匀冻胀性是产生隧道冻胀力的主要原因之一.为研究寒区隧道含裂隙围岩不均匀冻胀特性，进行了单向冻结条件下裂隙岩体的冻胀试验，分析了裂隙岩体在单向冻结时的冻结过程及变形规律.试验表明，裂隙处冻胀与岩石自身冻胀存在明显差异，裂隙岩体在冻胀过程中表现出明显的不均匀冻胀特性.在裂隙较深的工况下，随裂隙宽度的增加，裂隙法向的线冻胀率增加.对于含裂隙饱和砂岩，岩石自身线冻胀率随冻结温度的降低明显增大，而裂隙法向的线冻胀率明显减小.凝灰岩孔隙率较小，岩体的冻胀变形以裂隙处的冻胀变形为主，岩石自身在低温条件下表现为冷缩.根据试验结果，在岩体不均匀冻胀系数中考虑了裂隙的影响，计算了含裂隙饱和砂岩的不均匀冻胀系数.裂隙平行于温度梯度方向时，随裂隙宽度的增加，含裂隙饱和砂岩的不均匀冻胀系数有所减小.随温度梯度的增加，含裂隙饱和砂岩的不均匀冻胀系数增加，且增幅相比岩石不均匀冻胀系数明显增大.试验初步反映了裂隙岩体的不均匀冻胀特性，为寒区隧道裂隙岩体冻胀变形计算提供了试验依据.

关键词:裂隙岩体; 单向冻结; 不均匀冻胀系数; 冻胀特性

Abstract:

Non-uniform frost heave of rock in cold zone tunnel under unidirectional freezing condition is one of the main reasons for tunnel frost heave force. To study the frost heave characteristics of fractured rock mass in cold regions, laboratory tests of frost deformation in fractured saturated sandstone and tuff under unidirectional freezing condition have been conducted. The freezing process and frost deformation of the fractured rock mass under the unidirectional freezing condition have been analyzed. A significant difference exists between the frost heave at the fracture and the rock itself. The fractured rock mass shows evident non-uniform frost heaving characteristics during the frost heaving process. For saturated sandstone with deep fracture, the normal linear frost heave rate increases with the increase of fracture width. For fractured saturated sandstone, the linear frost heave rate of rock increases and the normal linear frost heave rate of fracture decreases obviously with the decrease of the freezing temperature. The frost deformation of the fractured tuff is mainly contributed by the frost deformation of the fracture, and the rock itself contracts during the freezing process. According to the experiments, the non-uniform frost heaving coefficient of saturated sandstone with fissures is calculated considering the influence of fracture. When the fracture is parallel to the direction of temperature gradient, the non-uniform frost heaving coefficient of saturated sandstone with fracture decreases with the increase of fracture width. The non-uniform frost heaving coefficient of saturated sandstone increases with the increase of temperature gradient. The increment of non-uniform frost heaving coefficient of saturated sandstone with fractures is larger than that of saturated sandstone. The test preliminarily reflects the non-uniform frost heaving characteristics of fractured rock mass, and provides experimental basis for the calculation of frost heave deformation of fractured rock mass in cold region tunnels.

Key words:fractured rock; unidirectional freezing; non-uniform frost heaving coefficient; frost heaving characteristics