弱胶结西域砾岩引水隧洞围岩抗力特性试验研究

弱胶结西域砾岩物质成分复杂、胶结较差,其力学性质十分不稳定,为科学反映弱胶结西域砾岩地层高压引水隧洞围岩的抗力特性,采用径向液压枕现场试验方法与基于传统承压板变形试验结果的完全弹性模型以及考虑开挖卸荷影响的弹塑性模型的理论估算方法,对弱胶结西域砾岩引水隧洞围岩的抗力特性进行综合研究。分析结果表明:(1)径向液压枕现场试验方法获得弱胶结西域砾岩围岩抗力系数为6.02~26.03MPa/cm;(2)根据承压板法等常规变形试验结果,采用完全弹性模型估算弱胶结西域砾岩围岩单位抗力系数为7.46~13.54MPa/cm,采用考虑开挖卸荷影响的弹塑性模型其估算结果为5.00~13.54MPa/cm;(3)受西域砾岩的颗粒组成特征及现场变形试验承压面积限制,根据承压板法获得的岩体变形模量,采用理论估算方法获得的围岩抗力系数较径向液压枕法试验结果偏低;(4)径向液压枕法现场试验结果反映了地应力环境、围岩材料特性、开挖卸荷影响等多因素影响下的围岩抗力特性,可为西域砾岩引水隧洞开挖及围岩衬砌提供直接可靠的围岩综合抗力系数。

Experimental research on resistance characteristics of surrounding rock of diversion tunnel in weak-cemented Xiyu conglomerate

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.