1.No.3 Exploring Institute of Geo‐mineral Resources, Shandong Province, Yantai Shandong 264004, China;2.Drilling Engineering Technology Research Center of Shandong Provincial Bureau of Geology & Mineral Resources, Yantai Shandong 264004, China;3.Sichuan Highway Planning, Survey, Design and Research Institute Ltd, Chengdu Sichuan 610059, China
P642;TU473