水封洞库地下水位监测资料分析与利用

Analysis and utilization of groundwater level monitoring data of underground water-sealed caverns

基于国内某大型水封洞库工程2015—2020年35个监测孔的地下水位监测资料,综合考虑库区施工进度及前期勘测获取的地质构造信息,系统分析库区地下水位的变化特征及变化原因,揭示地下洞室开挖与人工水幕系统对洞库区地下水位的影响以及库区可能存在的水封性不足的风险区域。根据地下水位时序变化与施工进度的对应关系,洞库区地下水位动态变化主要分为3类:水位基本稳定型、水位下降与邻近洞段开挖时间对应型、水位下降晚于邻近洞段开挖时间型。结合监测孔的空间分布及地下洞室施工进度发现:地下洞室开挖后库区整体地下水位均有所降低,但大部分区域在安全水位(-25 m)以上,人工水幕系统作用显著;西南侧局部区域地下水位受断层F2和F3以及节理裂隙密集带L4和L8的影响,在监测末期仍远低于安全水位(-25 m),存在水封性不足的风险。库区地下水位的动态变化特征与地下洞室的施工进度和质量联系紧密,地下水位的系统监测与及时分析反馈十分必要,亟需编制水封洞库地下水监测专项规范,推动水封洞库工程的全过程、全覆盖地下水位监测,提高水封洞库工程的施工效率。

Based on groundwater level data of 35 monitoring boreholes from 2015 to 2020 obtained from a large-scale underground water-sealed cavern project,the characteristics and causes of the changes in the groundwater level were systematically analyzed.Taking the construction progress of each cavern unit and geological structure information obtained from previous survey into account,those monitoring data revealed the influence of underground cavern excavation and artificial water curtain system on groundwater level,and the possible risk areas of low water pressure.According to the corresponding relationship between the temporal changes of groundwater level and construction progress,the monitoring boreholes could be divided into three types:water level maintains relatively stable,water level declines when adjacent tunnels were excavated;water level declines far after the adjacent tunnels were excavated.Combined with the spatial distribution of boreholes and the construction progress of underground caverns,it could be found that the groundwater level in the overall study area declined after the excavation of the underground caverns.However,benefited by the artificial water curtain,groundwater level in most area maintained higher than the safe water level(-25 m).Affected by faults F2,F3 and joint fracture zones L4,L8,local groundwater level in the southwest was still far below the safe water level(-25 m)at the end of monitoring,and it indicated a risk of insufficient water sealing.It indicated that the dynamics of the groundwater level in the study area was closely related to the construction progress and quality of the underground caverns,and the systematic monitoring of the groundwater level and timely analysis and feedback were essential.It is urgent to compile a specification for the underground water monitoring of the water-sealed cavern to promote more systematic monitoring of groundwater and improve the construction efficiency of the project.