隧道静力失稳的加卸载响应比判据及安全系数

Static instability criterion and safety factor of tunnels based on loading/unloading response ratio

为得到隧道的稳定性状态及静力失稳临界点的合理判定方法,将加卸载响应比(LURR)理论引入到隧道受力分析中,解析求解了对称荷载作用下圆形无衬砌隧道的非线性特性及其对应的LURR演化规律,证明了两者的关联性;基于施工及运营隧道不同的荷载特性,提出了基于LURR理论的隧道静力稳定性分析方法,分别分析了施工隧道和运营隧道的稳定性及其LURR变化规律,提出了基于LURR理论的隧道静力失稳判据及其判定机理。研究表明:理论推导得到的隧道变形非线性特性的LURR表达式解析解和有限元解吻合度高;隧道在不同的稳定性阶段,洞周关键点变形的LURR表现出不同的变化规律,根据此变化规律的变化,可划分隧道不同的稳定性阶段;在体系失稳前,隧道局部薄弱区域的LURR增长率会出现异常变化,为隧道失稳前兆判据;基于隧道的极限承载状态,通过各阶段与极限承载阶段的荷载比得到隧道不同阶段的安全系数。提出了隧道静力失稳的LURR判定方法。

To obtain the method for static instability criterion of tunnels, the loading/unloading response ratio(LURR) theory is introduced into the analysis method. The nonlinear characteristics and the LURR variation laws of unlined circular tunnels under symmetrical loads are analyzed through the analytical method, and the results have proved their relevance. The research approach of LURR method is put forward based on the different loading characteristics of construction and operation tunnels.The critical conditions and the LURR variation laws of tunnels with and without linings are analyzed respectively through the finite element method. The results show that the nonlinear characteristics based on the LURR theory of tunnel deformation calculated by the analytical solution and the finite element solution are similar. The LURR variation laws of tunnel deformation are different in each loading and stability stages of tunnel system, the LURR variation rate in the weak area of the tunnel will be abnormal before its instability, and the abnormal variation trend is the precursor criterion of the instability of the tunnel system.Based on the determination of the ultimate bearing state of the tunnel system by the LURR method, the safety factor of the tunnel system is obtained by using the loading ratio. The static instability method based on the LURR theory of tunnels is proposed.