钻孔弹模测试技术的应用研究

Application of Elastic Modulus Measurement Using Borehole Jack

利用改进的钻孔弹模计,结合云南某水电站工程,对测试点和工程工况条件进行了分析,对测试点位置、深度、方向的选择进行了探讨。对坝肩与坝基部位的岩体进行钻孔弹模测试,分析了变形曲线特征,讨论了如何选取合理的曲线段进行弹性模量计算,并与室内试验成果及承压板试验结果进行了对比分析。同时结合工程实际情况,通过对测试结果的综合讨论,为弹性模量和变形模量的取值提供了参考,为大坝建基面的选择提供依据。

Based on a project of hydro-power plant in Yunnan Province,we analyzed the selection of location,depth and direction of the test points via a modified borehole-jack elastic-modulus gauge.The test points should be in critical locations of the project,and the test direction should conform with the actual stress direction after the project is in operation.We then obtained the elastic modulus of rock mass at the abutment and the foundation of the dam,through which we analyzed the characteristics of pressure-deformation curves,and discussed how to select parts of the curves to estimate elastic modulus.There are two kinds of pressure-deformation curves displaying different deformation characteristics in borehole-jack test.In the case of curve A,in the presence of low pressure,the pressure and deformation displayed elastic-plastic relation,while in the presence of high pressure,it showed linear relation and non-linear relation in the rebound section.In the case of curve B,the pressure and deformation was in a linear-elastic relation when the pressure increased,and in a non-linear relation in the rebound section.Besides,we compared the results of borehole-jack test with those of lab test and bearing plate test.The borehole-jack test result is slightly larger than that of bearing plate test,whereas lab test results are much bigger than the other two.The test results are referential to the determination of elastic modulus and deformation modulus,and this modified testing technique provides scientific basis for selecting the foundation base of the dam.