60 Meso-Experiment on the Softening and Cracking of Surrounding Rock from a Railway Tunnel under Water Damage Condition
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Using a meso-mechanical testing system, the characteristics and mechanism of softening and cracking of swelling rock from a railway tunnel studied under different conditions with initial water damages. From mineral component and microstructure of rock, a chain of hydration actions are described to explain that hydration plays an important role in the damage and softening of swelling rock. Comparison of the stress-strain curve is done under different water conditions. The changes of elastic modulus and uniaxial compressive strength under different initial water contents are fitted by exponential functions. From fitting curves, some softening characteristics under different water damage describe the relationship between mechanical characteristics and initial water contents. Clear digital images of initial water damage and its four cracking stages show that, the whole cracking evolution process. Based on meso-damage mechanism, we find out that water environment is one of the most important factors to generate the softening, damage and cracking of swelling rock and then provides some experimental foundations for rock engineering in practice.