白鹤滩坝址区岩体弹性参数测试方法对比研究北大核心CSCD

弹性参数是工程岩体的重要力学指标,可以用于计算岩体质量分级、围岩弹性抗力系数、岩体强度参数等。实际工程中,主要采用刚性承压板试验、声波试验等测试岩体的弹性模量(弹模)、变形模量(变模)、波速等参数。由于测试的原理不同,且在不同岩性、不同方向上测试所得的结果可能离散型较大。本文整理了世界在建规模最大水电工程白鹤滩坝址区玄武岩的部分岩体弹性参数测试成果,包括156点刚性承压板试验;665点钻孔变形测试(200点刚性钻孔和465点柔性钻孔);58个平硐岩体地震波试验;143个岩体声波测试(58个平硐、85个钻孔)。通过分析所测弹模、变模、波速的相关性,给出了建议测试方案及岩体模量-波速的推荐经验换算公式。其中刚性承压板试验和地震波测试相关性较差,不推荐地震波波速换算岩体弹性参数;刚性承压板试验、钻孔模量均与声波波速指数相关,推荐刚性承压板试验作为岩体静模量测试依据,声波测试为动模量测试依据。相关研究可丰富我国大型水电工程建设的基础资料,为后续类似工程勘测设计提供参考。

Comparison of test methods for elastic parameters of rock mass in Baihetan dam site

Elastic parameters of engineering rock masses are key indexes for calculation of rock mass quality classification, elastic resistance coefficient of surrounding rock, rock mass strength parameters, etc. In practice, pressure-bearing rigid plate test (PRPT) and acoustic wave test (AWT) are two major methods for testing elastic modulus, deformation modulus, and wave celerity of a rock mass. Due to the differences in test principles, test results obtained by applying various methods to different lithology or different directions may be quite scattered. This paper sorts out some of the test results of basalt rock mass elastic parameters obtained in the pre-feasibility and feasibility study stages of the Baihetan dam, the largest hydropower project under construction in the world － including a 156-point PRPT, a 665-borehole deformation test (200 rigid and 465 flexible), a 58-adit test of rock mass seismic wave, a 143-adit-borehole AWT (58 adits and 85 boreholes). By examining the correlation between measured elastic modulus, deformation modulus and wave celerity, we determine and suggest better test schemes and work out an empirical formula for the conversion of wave celerity into rock mass modulus. The PRPT results are poorly correlated to seismic wave tests, so the conversion of seismic wave celerity to rock mass elastic parameters is not recommended. The PRPT and borehole modulus are exponentially related to acoustic wave speed. We recommend the PRPT method as a basis for the static modulus tests of rock masses and AWT as a basis for the dynamic modulus tests. The results would enrich the basic data for hydropower construction and help its survey and design.