Large-scale underground cavern group arrangement design method

Abstract

The invention discloses a large-scale underground cavern group arrangement design method applied to hydraulic and hydroelectric engineering and underground storage cavern engineering. According to the arrangement design method, principal factors, especially the essential factor of the rock strength-stress ratio, influencing underground cavern surrounding rock stability can be comprehensively taken into account, the designing scheme for large-scale underground cavern group arrangement can be more scientific, and considered factors are more comprehensive. The position of a main cave is determined at first, the orientation of an axis of the main cave is determined, then the thickness of a rock pillar in the main cave is determined, and at last the shape of the main cave is determined. When the orientation of the axis of the main cave is determined, the trend of a rock mass main structural surface on a construction site and the orientation of the maximum principal stress are measured at first, the orientation of the axis of the main cave is determined according to an included angle between the axis of the main cave and the trend of the rock mass main structural surface and an included angle between the axis of the main cave and the orientation of the maximum principal stress, the included angle between the axis of the main cave and the trend of the rock mass main structural surface is not less than 40 degrees, and the included angle between the axis of the main cave and the orientation of the maximum principal stress is 0-40 degrees.

Description

technical field [0001] The invention relates to an underground cavern layout method, in particular to a large-scale underground cavern group layout design method used in water conservancy and hydropower projects and underground storage projects. Background technique [0002] In the fields of water conservancy and hydropower projects, underground storage projects, etc., it involves the rational layout and design of underground caverns, especially in the underground powerhouses of hydropower stations in western my country. Due to the characteristics of large buried depth, high ground stress, and complex geological conditions, the stability and safety of the surrounding rock of large underground caverns have become very prominent. In recent years, relevant experts in the field of rock mechanics and underground engineering builders have realized more and more clearly that the basic strength of rocks, in-situ stress, development characteristics of structural planes of surrounding ...

AI Technical Summary

Problems solved by technology

[0004] Because the critical factor of rock strength-stress ratio is not considered, the layout of the main caverns of large underground caverns determined by existing methods is not reasonable, which may lead to underground After the excavation and unloading of the caverns, the surrounding rocks of the cavern group have relatively serious deformation and damage phenomena, such as rockburst, large aging deformation, large relaxation depth of the surrounding rock, and fracturing of the surrounding rock, which threaten the safety of the project and cause Delays in construction and increased investment

[0005] For example, the geological conditions of the underground powerhouse of a certain hydropower station are extremely complex, the scale of the caverns is large, and the maximum principal stress of the measured factory area is 20.0-35.7MPa. The compressive strength is only 60-75MPa, which is obviously lower than the rock strength

During the construction and excavation process, large time-dependent deformation of the surrounding rock of the cavern, obvious dislocation of cracks in the high side wall, splitting damage of the surrounding rock at the arch waist downstream of the main powerhouse, flaking of the rock mass, and fracturing of the surface rock mass occurred during the unloading of the surrounding rock. At the same time, the maximum depth of the relaxation zone around the cave has reached 2 to 5 times that of the general project and continues to develop. In the numerical calculation model, the plastic zone between the main caverns is connected, and the tension value of the anchor bolt and cable exceeds the limit. The deformation and failure of the surrounding rock and the exceeding of the support force are far more severe than those of the Ertan Hydropower Station, Pubugou Hydropower Station, and Guandi Hydropower Station, and the deformation and damage of the surrounding rock (rock pillar) on the side of the valley slope is significantly higher than that of the Far away from the side of the valley slope, the degree of deformation and damage of the surrounding rock near the large-scale structural surface is also significantly higher than that of ordinary parts, which poses a threat to the stability of the surrounding rock of the cavern and the safety of personnel and equipment during the construction period, making the cavern group difficult to maintain during excavation and support. Severe challenges were encountered during the process. For this reason, the project stopped excavation and strengthened support, resulting in an increase in investment and a delay in the construction period of about one year.