The deep buried large underground powerhouse cavern group of Shuangjiangkou Hydropower Station is arranged in the left bank mountain, and the geological lithology is brittle hard rock granite. The measured ground stress reaches 37.82 MPa, which is a high to extremely high stress zone. Research has found that the relaxation depth of underground power plants ranges from 2.2 m to 4.4 m, and the overall damage to surrounding rock shows an increasing trend with layered blasting excavation. However, the relaxation depth variation is small, and the average fragmentation variation of the relaxation layer is less than 10%. The lag effect of surrounding rock fracture is shortened. The GEDZ distribution in high stress brittle hard rock caverns can be evaluated using acoustic detection as the main method, supplemented by innovative semi quantitative indicators such as "rupture morphology"（new cracks, residual blasting hole half hole rate, rock burst failure depth）, and quantitative indicators such as permeability to reasonably evaluate the distribution of excavation damage areas in surrounding rock. This can better guide on-site design and construction, and provide reference for similar hydropower underground power plants and Sichuan Tibet Railway projects in the future.

In the technical construction stage, the classification of surrounding rock of underground caverns in high to super high ground stress areas is crucial to the qualitative and quantitative analysis and evaluation of the stability of surrounding rock, guidance for site design, construction and support. This paper takes the HC method as the basic criterion of rock mass quality, and takes the qualitative or quantitative data directly available on the site, such as the rate of residual holes in the excavation face, the depth of rock burst damage, and the characteristics of rock burst, as the correction criteria, Under the condition of ultra-high ground stress, the surrounding rock classification of brittle hard rock, crustal stress influence correction factor score table (Shuangjiangkou correction table), surrounding rock classification judgment table considering crustal stress correction (Shuangjiangkou method) and surrounding rock classification steps are proposed. Practice has proven that the Shuangjiangkou method can improve the accuracy of surrounding rock classification for brittle hard rocks in high or super high stress areas, and can provide a more accurate basis for support design, which has certain reference significance for other similar projects.

The measured maximum principal stress on the left bank of Shuangjiangkou Hydropower Station is 37.82 MPa, which is the highest measured in-situ stress of the underground powerhouse system of domestic hydropower stations under construction and already under construction, belonging to a high to extremely high stress area. Based on a large number of investigations, statistics, and summary of the macroscopic development characteristics of rockburst damage in underground caverns of large hydropower projects in the west, a new concept of "shallow cake layer type", "fan shaped plate crack uplift type", "large plate crack sliding type", and "new cracks" high stress brittle hard rock failure characteristics is proposed, and a geomechanical model of deformation and failure of surrounding rock of high stress brittle rock mass is proposed. Based on this, the prevention and control methods of ultra high stress rockburst disasters and support measures for brittle hard rock lag rockbursts during the technical construction stage are proposed. It has certain guiding significance for the prediction and prevention of rockburst, design and construction of similar hydropower projects, Sichuan-Tibet Railway, and other projects.