PRELIMINARY ANALYSIS ON ENGINEERING GEOLOGICAL CONDITIONS OF BOHAI STRAIT CROSS SEA PASSAGE

The preliminary study of the Bohai Strait Cross Sea Channel Project has always remained at the planning level. The systematic engineering geological survey is basically blank. By means of data collection, field investigation, offshore drilling, marine geophysical exploration and indoor test, this paper focuses on the engineering geological characteristics, special geotechnical properties, adverse geological processes and main engineering geological problems along the sea crossing channel. The results show the follows. (1)The thickness of the Quaternary overburden in the channel is different. The buried depth near the islands is shallow. The thickness in the hinterland of the channel and the middle of the channel is larger. The middle layer of Lao Tieshan waterway is the thickest. No bedrock is found in nearby ZK1 hole with depth of 186.3m. (2)The lithology along the channel mainly metamorphic rocks including quartz schist, metamorphic sandstone, arkose and gneiss. The lithology is relatively hard, and the basic classification of the rock mass is mainly grade Ⅲ~Ⅳ. (3)Special rocks and soils along the line include fill soil, recent loess, soft soil and argillaceous expansive rock. Adverse geological processes include dangerous rocks and rockfalls, man-made pits, harmful gases and seismic geological disasters. (4)Engineering geological problems mainly include crossing fault zone and water inrush of subsea tunnel. The risk of water inrush in tunnel is concentrated near fault fracture zone. The research results are of great significance to scientifically demonstrate the construction scheme of Bohai Strait Cross Sea Channel Project.