Deterioration Mechanism and Evaluation of Rock Mass in the Hydro-Fluctuation Belt of Qutang Gorge in the Three Gorges Reservoir Area

Chongqing Port is located in the upper reaches of the Yangtze River Economic Corridor and is deeply integrated with the Belt and Road Initiative. After the impoundment of the Three Gorges Reservoir Area, a hydro-fluctuation belt about 30 meters high has been formed. The rock masses on both sides of the reservoir area are eroded by long-term cyclic immersion, resulting in the deterioration and damage of the rock masses, and triggering disasters such as landslides, collapses, and chain-generated surges. The geological environment of the hydro-fluctuation belt has become increasingly severe, and the geological disaster risks on both sides of the reservoir area have increased significantly, seriously threatening the safety of the Yangtze River waterway and the Qutang Gorge Scenic Area. In this paper, various means such as field investigation, field tests, engineering geophysical prospecting, geological mapping, and engineering surveying are used to study the deterioration degree of the rock masses in the hydro-fluctuation belt on both sides of Qutang Gorge. It is considered that there are four types of rock mass deterioration in the Qutang Gorge hydro-fluctuation area, namely, crack expansion and new formation, corrosion/suffusion, loosening and erosion, and erosion of soft-hard interbedded layers. The failure modes of the rock mass deterioration zone in the hydro-fluctuation area include rock falling-collapse, fault-collapse, corrosion-toppling, and buckling-sliding failure. An evaluation system for the degree of rock mass deterioration is constructed from aspects such as rock mass structure, structural planes, soft layer zones, rock mass defects, slope deformation characteristics, the sensitivity characteristics of rock strength under the action of stress-water, and the integrity degree grade of the rock mass. Qualitative and semi-quantitative evaluations of the degree of rock mass deterioration are carried out. It is considered that the degree of rock mass deterioration in the hydro-fluctuation belt of Qutang Gorge is relatively intense, and locally intense.