Abstract: In order to measure the hidden danger of groundwater leakage under natural and artificial flow fields accurately, a new method of hydrogeological logging—sonar seepage vector method is proposed from the point of view of energy measurement. The basic principle, prototype instrument and measurement procedure are introduced systematically. Based on the principle of time difference measurement, the sonar seepage measurement instrument and display and control software have been developed independently, which combine many new technologies such as vector sonar technology, aeronautical orientation technology, pressure conduction technology and GPS locating technology. The sonar seepage measuring instrument can accurately determine the leakage location, leakage passage, flow velocity, flow direction, flow rate and other quantitative indicators. The foundation pit of diaphragm wall in water-rich stratum is studied as an engineering case. The three-dimensional visualized imaging system of seepage field is established to reveal the distribution of three-dimensional seepage field so as to dynamically guide seepage control design of foundation pit, leakage treatment. The effect of leakage treatment is verified by repetition test. The results show that sonar seepage vector method can locate leakage defects in underground engineering accurately, and the test results meet the needs of seepage control in engineering fully in the absence of strong noise interference. The early warning and grading criteria of leakage risk for foundation pit are put forward, which are mainly based on seepage velocity and supplemented by single hole seepage flow rate and permeability coefficient. At the same time, treatment measures must be taken in advance for avoiding leakage risk effectively by combining geological survey, monitoring, in-site inspection, emergency disposal with other means and mutually validation.

Key words: energy measurement, vector sonar, time difference method, hydrogeological logging, leakage, seepage field