North China University of Water Resources and Electric Power
Key Scientific Research Projects of Henan Province Colleges and Universities(20A410001)
The Laoshanzhai granite body is located in the North Huaiyang tectonic belt, north part of the Dabie orogenic belt. This granite is generated from the first magma event of the late Yanshan movement. The Laoshanzhai granite is mainly composed of medium-grained monzonitic granite. The study area is designed to be the upper reservoir of Wuyue Pumped Storage Power Station. It is important to clarify the characteristics of joints and tectonic stress field of granite for the impermeability treatment and construction of the reservoir. In this study, 351 joints were investigated within the reservoir area. The dominant orientation of the joints was identified as NNW-SSE, and the dip angles were steep.The joint surface was more strongly weathered in the shallow part, and the weathering degree decreased with increasing depth. The aperture of joints was mainly micro-tensioned-closed. The fillings of joints were quartz veins, rock particles and mud, which have poor permeability. Using the matching and staging of conjugate shear joints, the evolution of tectonic stresses was indicated in the study area. The main stress direction in the late Yanshan period is NEE-SWW, while that was transferred to near E-W during the Xishan period. The tectonic stresses in these two periods are consistent with the stress direction of tectonic movements in the Dabie Mountain area. After the Xishan period, the main stress direction in the study area was NNE-SSW, which is the characteristic of the tectonic stress field in the local area. The hydraulic fracturing test show that the tectonic stress in the study area is slightly higher than the self-gravity stress, which means that the study area is a low stress field area. The hydraulic test results show that the permeability of the rock decreases with increasing depth, but the permeability increases with the development of joints in the dense section of joints. It indicates that the near-surface medium-strongly weathered granite in the study area were characterized as severe unloading, developed joints and high permeability. with the increase of depth, the degree of weathering decreases and the unloading is weakened. Meanwhile, the increase of self-weight stress and surrounding pressure compressed the joints, reducing the aperture. The NNW and near-NWW-oriented joints without fillings were defined as the main permeable conducts at the deep area. Therefore, impermeability treatment should be carried out for this type of joints during the design and construction of the reservoir.
王伯林,黄潇潇,孟令超,等. 信阳牢山寨花岗岩岩体节理发育特征及构造应力分析[J]. 科学技术与工程, , ():复制