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Abstract Based on large amounts of wave velocity-depth curves of surrounding rocks in underground powerhouses of Jingping I and Xiluodu hydropower stations，the acoustic velocity-depth curves are analyzed and classified into 5 types. With the least square method，acoustic velocity-depth curves are fitted with 3 different functions. By substituting the acoustic velocity in classical wave velocity-elastic modulus formula with the fitting functions，the relationship between elastic modulus and depth of surrounding rock in underground powerhouse is established. Thus the relaxation phenomenon of elastic modulus of rock mass near the cave wall and decreasing law of elastic modulus after excavation are evaluated；and the fitting formula in wall rock loosing zone is proposed. The newly proposed formula is applied to back analysis and deformation advanced forecasting in underground powerhouse. The analytical results fit practical deformation law of surrounding rock much better than classical elastoplastic analysis results. The study results provide a new theoretical foundation for stability calculation and feedback analysis of surrounding rocks.
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Received: 24 February 2011
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2011, Vol. 30 
