Abstract: Weak-cemented Xiyu conglomerate, characterized by its with complicated mineral composition and poor cementation, has unstable mechanical properties. In order to reflect the resistance characteristics of surrounding rocks of the diversion tunnel in weak-cemented Xiyu conglomerate, the radial hydraulic pressure pillow test was carried out in Kuitun Water diversion project in Xinjiang province. Meanwhile, based on the traditional bearing plate deformation test results, an elastic model and an elasto-plastic model considering the effect of excavation unloading were utilized to estimate the resistance coefficient of the weak-cemented Xiyu conglomerate. The results indicate that: 1) According to the result of the radial hydraulic pressure pillow test, the unit resistance coefficients of weak-cemented Xiyu conglomerate are in the range of 6.02 to 26.03 MPa/cm. And the unit resistance coefficient in vertical direction is greater than that in horizontal direction. 2) According to the traditional bearing plate deformation test results, the estimated values of the unit resistance coefficient of weak-cemented Xiyu conglomerate surrounding rocks are 7.46-13.54 MPa/cm and 5.00-13.54 MPa/cm using elastic model and elasto-plastic model, respectively. 3) Due to particle composition of Xiyu conglomerate and the ordinary area of bearing plate, the theoretical estimate results of the unit resistance coefficients adopted with the traditional bearing plate deformation test results are lower than that obtained by the radial hydraulic pressure pillow test. 4) The radial hydraulic pressure pillow test results could reflect the resistance characteristics of the surrounding rocks under the influence of multiple factors such as the ground stress environment, the material characteristics of the surrounding rocks, and the loosening effect of excavation and so on. The radial hydraulic pressure pillow test results can provide a direct and reliable comprehensive resistance coefficient of the surrounding rocks for the design of the diversion tunnel excavation or the lining support of surrounding rocks.

Key words: Xiyu conglomerate, weakly cemented, resistance coefficient, radial hydraulic pressure pillow testing, theoretical estimation