直流电法识别东南沿海咸淡水界面的技术研究

Study on Direct Current Method to Identify Salt-fresh Water Interface in Southeast Coastal Area

东南沿海地区海岸带沿线近年来受海水入侵导致地下咸水的形成已逐渐危害到人民生活和经济建设。如何划分泉州湾地区咸淡水界面分布情况,圈定咸水区影响范围,成为区域经济发展的一个主要研究课题。本文结合研究区周边环境条件,从地球物理勘查角度分析了泉州湾地区地下咸淡水之间的地球物理特性差异和地下含水结构特点。利用地下含水结构的电阻率、极化率数据与地下水体矿化度指标建立联系,并以此为物探工作前提,选择了激电测深法和超高密度电法等对人文活动产生的游离电场有着很强的抗干扰能力的直流电法,在原有水文地质调查地下水检测矿化度的基础上增加物探辅助工作,弥补了该地区可取样井位较少的缺点,使得测网密度更大,连贯性更好,工作效率、勘查结果有效提升了钻探取样准确率,降低了调查成本。通过电阻率等电性参数间接地划分了咸淡水区域,精准地选取了1号和2号监测孔位置,完成了对该研究区域的咸淡水演化监测体系建立工作,避免了监测孔选取不当带来的损失。

In recent years,the formation of salt water in the coastal zone of southeast China has gradually endangered people’s life and economic development.How to divide the interface distribution of salt and fresh water in Quanzhou Bay area and define the influence area of salt water area has become a main research topic of regional economic development.Based on the environmental conditions of the study area,this paper analyzes the differences in geophysical characteristics and the characteristics of groundwater geophysics structure between the underground salt and fresh in the Quanzhou Bay area from the perspective of the geophysical survey.Using the resistivity and polarizability data of the underground water-bearing structure to establish a relationship with the groundwater salinity index,and taking this as the premise of geophysical prospecting work,the direct current(DC)method with strong anti-interference ability to the free electric field generated by human activities such as the induced polarization(IP)sounding method and the ultra-high density electrical method were selected.On the basis of the original hydrogeological survey of groundwater salinity detection,geophysical prospecting assistant work was added to make up for the shortcomings of less sampling wells in the area,making the measuring network more dense and more coherent,the work efficiency better and the exploration result more effective,thus improving the drilling sampling accuracy and reducing the survey cost.Through the electrical parameters such as resistivity,the saltwater and freshwater areas are indirectly divided,and the locations of No.1 and No.2 monitoring holes are precisely selected,and the monitoring system of the evolution of saltwater and freshwater in the study area is established,which avoids the loss caused by the improper selection of monitoring holes.