岩土工程勘察中地下水问题的探讨

Discussion of groundwater about geotechnical investigation in Yinchuan

为解决近年来银川市地下水对建筑物设计施工的影响,从岩土工程勘察角度,对地下水位的测定、变化范围、岩土渗透系数、地下水腐蚀性四个方面进行了分析讨论,提出目前存在着勘察时水位量测不准确,地下水水位的变化幅度不可靠,降水井的深度不合适,隔水层以下地下水呈现出更高矿化度等问题.相应的解决方法为:一般工程,整个场地钻探结束24h后测定静水水位;对大型重点工程,地下水位初勘时,设置地下水长期观测孔;因银川市地下水位连年下降,抗浮设计水位应以近3～5a最高水位计算,而不应取历年最高水位;由专业部门编制银川市地下水位变化幅度图,成果共享;通过对各主要土层渗透系数指标值分析,第⑤层粉土为良好的隔水层,施工降水设计时降水井不宜穿过该层土;深层降水井中的地下水不可作为工地施工用水,浅层降水井中水质一定要化验才可决定能否作为施工用水.

In order to solve some problems about the groundwater with their influence on the architectural design construction in Yinchuan in recent years, this dissertation studied some problems about the investigation of groundwater, the range of groundwater＇ s depth, the permeability coefficient of soil and the corrosivety of groundwater from geotechnical investigations. Some problems were also pointed out such as the untrue investigation of groundwater, the unreliable range of groudwater＇s depth, the unsuitable depths of lower-water-well, and highest total mineralization under the impervious layer. Some better measures were also obtained. The depth of groundwater should be investigated when it was 24 hours that the drilling was finished for general project. The long-term observation borehole of groundwater should be established for larger-scale project in preliminary geotechnical investigation. The depth of groundwater in designing against buoyancy was not the deepest groundwater in so long years but in recent 3-5 years because the depth of groundwater became lower and lower in Yinchuan. The professional departments should draw the chart of groundwater＇s depth in Yinchuan, it is convenient to share for the investigators and designers. The 5th layer of silt was the better impermeable layer by the analysis of the index value of permeability coefficient each layer so that the depth of lower-water- well should not cross the layer. The groundwater in deeper lower-water-well was not used for construction. The quality of groundwater in shallow lower-water-well must be analyzed for the use of construction.