基于单孔热响应测试的地下水渗流场评价——以扬中指南村崩岸场地为例

EVALUATION OF GROUNDWATER FLOW FIELD BASED ON SINGLE-BOREHOLE THERMAL RESPONSE TEST—A CASE STUDY OF ZHINAN VILLAGE BANK COLLAPSE SITE

我国具有十分发达的水系,防洪减灾形势依旧严峻,需要不断提高堤防安全监控水平。堤防渗流场是影响堤防安全的关键因素,因此开展渗流场特征识别是保障堤防安全的重要前提。为弥补常规渗流场监测技术的不足,本文基于主动加热光纤热响应测试(Actively Heated Fiber Optics Based Thermal Response Test,ATRT),以“长江第一崩”扬中指南村崩岸场地为例,开展了单孔热响应测试研究,初步探索了堤防渗流场精细化评价方法。结果表明:(1)ATRT得到的高时空分辨率(时间采样间隔30 s,空间采样间隔0.41 m)光缆温度响应数据,可以用于识别不同地层中的地下水流速差异;(2)研究场地内埋深较浅的粉细砂层和埋深较深的砾砂层中的地下水渗流具有不同的演变规律;(3)指南村崩岸场地内地下水渗流场与地表水具有一定的联系,地下水流速整体表现出“近岸大,离岸小”的特点,这是指南村崩岸灾害的潜在诱因之一。研究结果初步验证了ATRT在评价堤防渗流场特征的可行性。该方法基于单个钻孔即可获得高时空分辨率的地下水渗流场分布特征,在堤防渗流场评价中具有较强的应用潜力。

China has a complex water system with severe flood control and disaster reduction situations.There is an urgent need to continuously enhance the level of embankment safety monitoring.The seepage field in embankment is a crucial factor affecting the embankment safety,so the identification of the characteristics of the flow field is an essential prerequisite to ensure the embankment security.To make up for the insufficiency of conventional flow field monitoring technology,we carry out single-borehole thermal response tests based on the Actively Heated Fiber Optics Based Thermal Response Test(ATRT)and explores the advanced evaluation method of the seepage field in embankment by taking the collapse site in the Zhinan Village,Yangzhong city.The Zhinan Village collapse is known as the most significant collapse on the Yangtze River.The results show that:(1)ATRT can obtain temperature response data with a high temporal-spatial resolution(temporal sampling interval 30 s,spatial sampling interval 0.41 m),thereby identifying the differences in groundwater flow rate in different strata;(2)Groundwater flow rates in fine sand and gravel sand have different evolution law;(3)The groundwater flow field in the collapse site of Zhinan Village has a connection with the surface water,and groundwater rate is characterized by"The groundwater rate near the riverbank is high,while that far away from the riverbank is low",which may be an essential cause of the collapse.The research results verify the feasibility of ATRT in evaluating the seepage field in embankment characteristics.The method can obtain the vertical distribution characteristic of the flow field with a high spatial resolution based on a single borehole.The ATRT technology is simple and shows excellent application potential in evaluating the seepage field in embankment.