现场抽水试验在工程中确定含水层渗透系数的应用  

Practical Application of In-Situ Pumping Test to Determine Coefficient of Permeability of an Aquifer

作　　者：马赛 王康 傅志斌[1] MA Sai;WANG Kang;FU Zhibin(China Institute of Geotechnical Investigation and Surveying Co.Ltd.,Beijing 100007;China Aerospace Academy of Architectural Design&Research Co.Ltd.,Beijing 100162)

机构地区：[1]建设综合勘察研究设计院有限公司,北京100007 [2]航天建筑设计研究院有限公司,北京100162

出　　处：《土工基础》2022年第3期486-490,共5页Soil Engineering and Foundation

摘　　要：确定场地渗透系数主要由抽水试验来完成,针对渗透系数现已有多种基于抽水试验的计算方法,但由于室内试验不能准确描述实际工程中的土层模型,现场试验的方法比实验室模拟测试更贴合实际工程中的应用,在具体工程中由现场试验来确定场地渗透系数更能得到准确的数据。针对北京某地下车库潜水含水层,通过场地周边现有降水井采用无压完整井进行抽水试验,测定场地在基坑开挖和基础施工阶段地下水影响深度范围内土层的综合渗透系数。试验结果表明:(1)经过长时间的地下水降排作业,地下水位发生较大变化;(2)测得场地降水深度范围内第一层潜水含水层实际渗透系数k值范围在40~50m·d^(-1)之间,低于勘察报告所提经验值;(3)分析发现由中粗砂充填的卵石地层对渗透系数影响较大,长时间的抽排水也是导致渗透系数下降的主要原因;(4)对比计算基坑涌水量,不同渗透系数下得涌水量差距较大,直接影响工程造价。The coefficient of permeability is predominantly determined by the pumping test.There are many analytical methods to interpret the test results for the coefficient of permeability.In general,the test conditions of the in-situ measurement method are more consistent with the actual subsurface condition than that of the laboratory test condition,because laboratory test method cannot simulate the on-site soil layers accurately.It is necessary to determine the site coefficient of permeability by in-situ measurement for a specific soil layer in an actual project in Beijing.Throughout the dewatering wells around the site,a non-pressure complete well point was used for the pumping test,an average coefficient of permeability of the soil layer in the zone by the groundwater variation in the stage of the deep excavation and foundation construction was measured by the in-situ pumping test.The results show that:(1) after a long period of discharge of groundwater,the groundwater level changes significantly;(2) the actual coefficient of permeability k value of the first aquifer layer measured within the dewatering depth ranges from 40 to 50 m/d,which is lower than the empirical value recommended in the survey report.(3) The analysis shows that the cobble stratum filled with medium to coarse sand has a significant influence on the coefficient of permeability,and the long-term drainage is the main reason for the decrease of coefficient of permeability.(4) Comparing with the groundwater inflow to the excavated area,the difference of groundwater inflow of different coefficient of permeability is large,which directly affects the construction cost.

关 键 词：现场抽水试验 渗透系数 降水 

分 类 号：TU413[建筑科学—岩土工程]