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

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.