On mechanical properties and failure characteristics of surrounding rock of tunnel with weak interlayer under freezing-thawing cycles

Abstract

There are a lot of weak intercalations in the surrounding rock of tunnels along Sichuan Tibet railway, and they are greatly affected by the cold climate. To understand the influence of dip angle of interlayer and freezing thawing cycles on the mechanical properties of tunnel surrounding rock, the interlayered rock mass with different dip angle of weak interlayer and different freezing thawing cycles was prepared in laboratory, and the uniaxial compression test of rock mass with weak interlayer was carried out. The results show that: (1) the deformation of hard rock part with weak interlayer is smaller, while the failure of soft rock interlayer is more severe. When the dip angle of the interlayer is small (β=0° and 30°), the fracture crack is nearly parallel to the dip angle of the interlayer after rock failure. When the dip angle of the interlayer is large, the fracture surface of the rock mass and the interlayer present an X-shaped intersection. The more freezing thawing cycles, the stronger the damage degree of rock mass (2) Uniaxial compressive strength and elastic modulus of rock mass decrease first and then increase with the increase of dip angle of interlayer, and the compressive strength and elastic modulus are the minimum when the dip angle of interlayer β=45°. Compared with the rock mass with horizontal weak interlayer, the compressive strength is reduced by 35.27%, and the elastic modulus is reduced by 34.84%. (3) Freezing thawingw cycles have a significant deterioration effect on the mechanical properties of rock mass. The bearing capacity of rock mass decreases with the increase of freezing thawing cycles, but the plastic deformation capacity increases. There is a negative exponential correlation between uniaxial compressive strength, elastic modulus and freezing thawing cycles, and a positive linear correlation between peak strain and freezing thawing cycles.

Keywords

• sichuan-tibet railway
• engineering geology
• freezing thawing cycle
• weak interlayer
• mechanical test