Detection of Deep Water Courses in Layered Media Using Underground Geophysical Methods
Yi Yongsen, 1989. "Detection of Deep Water Courses in Layered Media Using Underground Geophysical Methods", An Overview of Exploration Geophysics in China — 1988, Zhao Jingxiang, Wang Yanjun, Fu Xuexin, Stanley H. Ward
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Many coal mines in north China have been threatened historically by Ordovician limestone water under the coal measures. The key point to solving this problem is to locate the watercourses. The two examples given describe the application of underground geophysical methods to detecting deep water courses buried in layered media. The methods used include (1) the cross-borehole electromagnetic wave method (apparent attentuation coefficient measurement), (2) electromagnetic wave logging, and (3) high-precision borehole temperature measurement. The JWQ-3 and JWQ-3A electromagnetic wave meters for logging and cross-borehole measurement designed and manufactured by the Institute of Geophysical and Geochemical Exploration were used to transmit and receive the electromagnetic waves. The operation frequencies are 0.5, 1.0, 2.0, 4.0, 8.0, 16.0, and 32.0 MHz. For temperature measurements, two kinds of digital borehole thermometers are used in the study, with precisions of 0.05°C and 0.2°C and resolutions of 0.0001°C and 0.01°C, respectively.
In Fengfeng 4 Mine, Hebei province, the location of a vertical watercourse was detected accurately by means of the cross-borehole electromagnetic wave method and high-precision borehole temperature measurements. The watercourse was then blocked with cement injection and the water table in the whole mine was decreased by more than 90 m and the recoverable coal reserve of 9.16 million tons was saved. A watercourse in a flooded mine was located in Longquan Mine, Shandong Province using underground geophysical methods. Waterflow of 14.27 t/ min was reduced to 0.15 t/min. and enabled the flooded mine to resume production.