高地温水工隧洞围岩喷层结构承载特性研究

Study on bearing characteristics of shotcrete layer structure of hydraulic tunnel under high ground temperature

为研究水工隧洞在高地温复杂环境下喷层结构的受力特性,以新疆某高地温引水隧洞为依托,采用理论分析和数值模拟的方法,对高地温引水隧洞喷层结构的受力特性进行了研究,并分析了线膨胀系数、围岩不同深度温差以及地应力水平侧压力系数对隧洞喷层结构受力特性的影响。由计算结果可知:在高地温情况下,理论计算的径向压应力最大值为2.07 MPa,环向压应力最大值为35.37 MPa;数值模拟的径向压应力最大值为4.36 MPa,环向压应力最大值为34.37 MPa。通过对比发现:理论计算的径向位移最大值为1.2 mm,环向位移最大值为0.75 mm;数值模拟的径向位移最大值为2.1 mm,环向位移最大值为0.95 mm。数值模拟的结果表明:隧洞围岩喷层结构承受的应力随着线膨胀系数增加会增大;喷层的拱顶与拱底处承受的环向应力随着温差的增加会增大,喷层的拱腰处承受的环向应力随着温差的增加会减小;喷层结构承受的应力随着地应力水平侧压力系数的增加会增大。

In order to study the bearing characteristics of the shotcrete layer structure of hydraulic tunnel under complicated high ground temperature environment, the stress characteristics of the shotcrete layer structure of water diversion tunnel under high ground temperature is studied herein with the methods of theoretical analysis and numerical simulation by taking a water diversion tunnel under high ground temperature in Xinjiang as the study case, and then the influences from linear expansion coefficient, temperature differences in different depths of surrounding rock and the horizontal lateral pressure coefficient of ground stress on the stress characteristics of the shotcrete layer of the tunnel are analyzed as well. It is known from the calculation result that under the condition of high ground temperature, the maximum value of the theoretically calculated radial compressive stress is 2.07 MPa with the maximum value of the circumferential compressive stress of 35.37 MPa, while the maximum value of the numerically simulated radial compressive stress is 4.36 MPa with the maximum value of the circumferential compressive stress of 34.37 MPa. It is found out from the relevant comparison that the maximum value of the theoretically calculated radial displacement is 1.2 mm with the maximum value of the circumferential displacement of 0.75 mm, while the numerically simulated maximum value of the radial displacement is 2.1 mm with the maximum value of the circumferential displacement of 0.95 mm. The numerically simulated result shows that the stress borne by the shotcrete structure of tunnel surrounding rock is to be increased with the increase of the linear expansion coefficient. The circumferential stresses at both the tunnel vault and arch bottom of the shotcrete layer are to be increased with the increase of the temperature difference, while the circumferential stresses at the arch waist of the shotcrete layer is to be decreased with the increase of the temperature difference and the stress borne by the shotcrete layer is to be increased with the increase of the horizontal lateral pressure coefficient of ground stress of the in-situ stress as well.