Development characteristics of unloading zones of high and steep bank slope in the Yiong Tsangpo of Tibet and its engineering significance

Located at the top of the eastern Himalayan tectonic junction on the Qinghai-Tibet Plateau, the Yiong Tsangpo River basin is characterized by the alpine and gorge landform, complex structure, and frequent occurrence of geological disasters and instability of high and steep slopes. In order to determine the formation mechanism of geological disasters and the mode of slope instability in Yiong Tsangpo River basin, through the investigation of slope structural plane, directional inclined drilling, in-hole wave velocity test, adit exploration and seismic wave method, the development law of typical bank slope unloading zone in Yiong Tsangpo River basin was analyzed, and the bank slope unloading zones were divided by core integrity, fracture opening, rock mass wave velocity and other indexes. The results show that the unloading degree of rock mass weakens gradually from shallow to deep part of the slope, the higher the elevation is, the stronger the unloading development is, and the unloading degree of the west bank of the valley is obviously stronger than that of the east bank. It is concluded that the slope surface below 0 m to 20~30 m is a strong unloading zone, 20~30 m to 40~45 m is a weak unloading zone, and below 40~45 m is a non-unloading zone. Based on the stability analysis results of the bank slope, it is proposed that the slope is strengthened with anchor cables and bolts, and engineering prevention and control measures can be taken such as the clearing of dangerous rocks at the entrance, blocking and anchoring. The research results are of great significance for the guiding of planning and construction of highway, railways and hydropower, regional disaster prevention and mitigation.