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

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.