综合超前地质预报技术在断层发育区隧道下穿水库工程建设中的应用

Application of comprehensive advanced geological prediction technology in tunnel penetrating reservoir construction in fault development area

首先研究了断层发育区某隧道下穿水库段的工程、水文地质特征和地球物理特征.根据富水断层破碎带一般表现为低波速和低电阻率的物性特征,有针对性的选择了以波速差异为物性基础的地震波法和以电阻率差异为物性基础的瞬变电磁法进行综合超前地质预报.其中地震波法采用地层速度和地质构造界面进行综合分析解释,对断层破碎带的位置、规模及产状进行了探测;瞬变电磁法采用多测线、多方位的探测方式,并采用了二维反演、三维成像等数据处理技术,对断层破碎带的富水情况和地下水的空间分布进行了探测.根据地震波法和瞬变电磁法综合预报结果,对推断的断层破碎带位置及富水情况进行超前钻探验证,验证结果与预报结果相吻合.最后根据物探综合预报结果、超前钻探结果及钻孔地下水监测结果,推断隧道前方断层破碎带地下水极发育、水压水量极大,与上方水库联通.预报结论为提前采取施工措施提供了依据.

This paper first studies the engineering, hydrogeological and geophysical characteristics of a tunnel under a reservoir section in the fault development area. According to the physical characteristics of the water-rich fault fracture zones, which are generally characterized by low wave velocity and low resistivity, the seismic wave method based on the difference of wave velocity and the Transient Electromagnetic Methods(TEM)based on the difference of resistivity are selected for comprehensive advanced geological prediction. The seismic wave method uses the formation velocity and the geological structure interface to comprehensively analyze and interpret the location, scale and occurrence of the fault fracture zone. TEM adopts multi-line and multi-azimuth detection method, and adopts data processing technologies such as 2 d inversion and 3 D imaging to detect the water-rich situation and spatial distribution of groundwater in the fault fracture zone. Based on the comprehensive prediction results of seismic wave method and TEM, the location of the inferred fault fracture zone and its water abundance were verified by advanced drilling, and the verified results were consistent with the predicted results. Finally, according to the comprehensive geophysical forecast results, advance drilling results and borehole groundwater monitoring results, it can be concluded that the front of the tunnel fault fracture zone has extremely developed groundwater, great water pressure and water volume, and is connected with the reservoir above. The forecast conclusion provides a basis for taking construction measures in advance.