MEASUREMENTS AND APPLICATION OF IN-SITU STRESS AND RELATED ROCK MECHANICAL PARAMETERS OF SURROUNDING ROCK OF AIR-CUSHION SURGE TANK AT A HYDROELECTRIC PROJECT IN WEST SICHUAN
Abstract:In order to demonstrate the design scheme of the air-cushion surge tank for a hydroelectric project,the hydraulic fracturing technology is adopted to define the in-situ stress and related rock mechanical parameters of rock mass surrounding the high pressure cavern. The measurement results show that the minor principal stress in the rock mass around the high-pressure cavern is 5.6–7.9 MPa and nearly horizontal,the jacking strength is about 6.0–8.0 MPa,and the permeability under pressure of 7.0 MPa is less than 1.0 Lu. Therefore,the rock mass for the cavern is of good rock mechanical performance and a good pressure-cavern place. But there exist some tensile fissures in the rock mass of high-pressure cavern,which have poor bearing capacity,good connectivity and severe water permeability,and are a huge hidden trouble for the non-supported high-pressure cavern construction. The effective high-pressure grouting measures can improve the integrity of rock mass structures and enhance the high-pressure sealing function,which is the key for the construction of the project.