On mechanical properties and failure characteristics of surrounding rock of tunnel with weak interlayer under freezing-thawing cycles
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摘要:
川藏铁路沿线隧道围岩中常存在大量软弱夹层，且岩体受严寒气候影响较大。为研究夹层倾角和冻融循环对隧道围岩力学性质的影响，室内制备了不同软弱夹层倾角、不同冻融循环次数条件下的互层岩体，并对含软弱夹层岩体展开了单轴压缩试验。研究发现：（1）含软弱夹层岩体的硬岩部分变形较小，而软岩夹层部分的破坏更加剧烈。夹层倾角较小时（β=0°、30°）岩体破坏后裂纹与夹层倾角接近平行，当夹层倾角较大时岩体破裂面与夹层呈X型交叉状；冻融循环次数越多，岩体的破坏程度越强烈。（2）随着夹层倾角的增大，岩体的单轴抗压强度和弹性模量先减小后增大；当夹层倾角β=45°时，抗压强度和弹性模量最小，抗压强度较含水平软弱夹层岩体降低35.27%，弹性模量降低34.84%。（3）冻融循环劣化了夹层岩体的力学性质，岩体承载能力随着冻融循环次数的增加而减弱，但塑性变形能力有所增强。在冻融循环作用的影响下，岩体抗压强度、弹性模量呈负指数型递减，峰值点应变则呈线性增大。
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.
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Key words:
- Sichuan-Tibet Railway /
- engineering geology /
- freezing thawing cycle /
- weak interlayer /
- mechanical test
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表 1 含软弱夹层岩体物理参数
Table 1. Physical parameters of rock mass containing weak interlayer
分组 直径/mm 高度/mm 平均密度/（g·cm−3） 夹层厚度/mm 夹层倾角/（°） A 50.12 99.75 2.37 19.95 0 B 50.08 100.54 2.36 20.70 30 C 49.86 100.13 2.34 19.80 45 D 50.32 100.33 2.32 20.03 60 
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表 2 不同试验条件下岩体破坏形态特征
Table 2. Faliure characteristics of rock mass specimen under different testing conditions
试验条件 n=0 n=10 n=20 n=30 β=0° 
β=30° 
β=45° 
β=60° 
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表 3 不同条件下含软弱夹层岩体力学参数
Table 3. Mechanical parameters of rock mass with weak interlayer under different conditions
分组 倾角/（°） 循环次数 抗压强度/MPa 峰值点应变/% 弹性模量/GPa A 0 0 16.91 0.76 3.86 10 13.70 1.21 2.70 20 11.73 1.23 2.03 30 10.51 1.50 1.55 B 30 0 14.82 0.63 3.53 10 11.06 0.71 2.34 20 8.71 0.76 1.71 30 7.79 1.01 1.16 C 45 0 11.07 0.55 3.03 10 8.85 0.75 1.78 20 7.53 0.80 1.11 30 6.80 1.19 0.86 D 60 0 15.55 0.64 3.63 10 12.82 0.79 2.44 20 10.60 0.88 1.81 30 9.58 1.14 1.27
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