Layout design method of underground cavern group

Abstract

The invention discloses a layout design method of an underground cavern group applied to a water conservancy and hydropower project and an underground storage. According to the layout method, main factors influencing the stability of surrounding rock of the underground caverns, especially, the rock strength stress ratio which is the essential factor can be fully taken into consideration. The method comprises the following steps of: firstly determining the positions of main caverns, determining the axial line directions of the main caverns, determining the thicknesses of rock pillars among the main caverns, and finally determining the shapes of the main caverns, wherein in the process of determining the thicknesses of the rock pillars among the main caverns, the thicknesses of the rock pillars are 1.0-2.5-time mean than excavation span between two adjacent main caverns and are 0.5-0.8 times that of the height of the big one in the adjacent two main caverns. Compared with the layout design with a design plan provided by a using traditional layout method, the layout design with the layout method disclosed by the invention is more scientific; and especially, in a highland stress environment and in a condition with relatively low surrounding rock strength, the phenomena of the deformation and destruction of the surrounding rock after the surrounding rock of the underground cavern group is excavation-unloaded can be greatly reduced or the deformation and destruction degrees of the surrounding rock can be reduced.

Description

technical field [0001] The invention relates to an underground cavern layout method, in particular to an 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 rocks, and ...

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, and the rock strength is obviously low

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.