Method for judging anisotropic relative relaxation thicknesses of surrounding rock of chamber of columnar jointing basalt

Abstract

The invention relates to a method for judging the anisotropic relative relaxation thickness of surrounding rock of a chamber of a columnar jointing basalt so as to quickly and accurately judge the anisotropic relative relaxation thickness of the surrounding rock. According to the technical scheme, the method comprises the steps that 1, a top plate, a bottom plate and two side walls of a certain section of the chamber are respectively provided with a group of testing drill holes; 2, wave velocity testing is conducted through a cross hole method, and a wave velocity value tested within the range 2m away from the bottom of each drill hole serves as an original undisturbed wave velocity Vpo of the columnar jointing basalt, and wave velocities actually measured within the other ranges of the drill holes are subjected to statistics according to different depths; 3, according to the formula Kvb=(Vpm/Vpo)<2>=0.75-0.45, the relaxation disturbance wave velocity Vpm of the top plate, the relaxation disturbance wave velocity Vpm of the bottom plate and the relaxation disturbance wave velocity Vpm of the two side walls are solved respectively, the Vpms are matched with the wave velocities actually measured in the second step in the corresponding directions, and then the anisotropic relative relaxation thickness is obtained. The method is applied to the field of hydraulic anisotropic surrounding rock chamber engineering.

Description

technical field [0001] The invention relates to a wave velocity quantitative evaluation method for the relative relaxation degree of the anisotropic surrounding rock of a columnar joint basalt chamber, which is mainly applicable to the field of hydraulic anisotropic surrounding rock chamber engineering. Background technique [0002] Columnar jointed basalt bodies are widely distributed in the hydropower development areas of Southwest my country, such as the giant hydropower stations Baihetan, Xiluodu and Ertan Hydropower Stations in my country, etc., especially the Jinsha River Baihetan Hydropower Station under construction, columnar jointed basalt has become the main hydropower project It is one of the surrounding rocks of hydraulic tunnels and the foundation rock mass of dams. In engineering, if the rock mass with significant anisotropy is assumed to be isotropic for research, it will inevitably cause large errors. Therefore, the analysis of the surrounding rock of the cham...

AI Technical Summary

Problems solved by technology

[0005] First of all, the undisturbed columnar jointed basalt itself is a broken rock mass. After excavation and unloading, the joint surface opens and slides, which intensifies the degree of fragmentation. As the standard (such as the wave velocity of basalt blocks), this ignores the influence of the original degree of fragmentation, and fails to consider the influence of the anisotropy of the original surrounding rock. The degree of relaxation, that is, the relaxation area of ​​the excavated surrounding rock compared with the original surrounding rock cannot be obtained, only the relaxation area of ​​the excavated surrounding rock compared with the intact basalt block can be obtained

[0006] Secondly, it cannot be judged by the absolute value of the wave velocity. Assuming that within the depth range of 5m of the wave velocity test borehole, the rock mass on the roof and floor of the chamber is highly broken before being disturbed, and the average wave velocity is low (assuming the initial value is 5000m / s). After excavation, if the roof and floor protection measures are good, the disturbance to it is relatively low, and the degree of relaxation is not large, but if judged by the absolute value, the wave velocity is still very small (assuming that it is 4500m / s after excavation), and it will be concluded that the chamber The conclusion that the roof and floor are greatly affected by excavation and the thickness of the relaxation zone is large (the actual wave velocity is only 10% lower than that of the original surrounding rock)

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