基于正交试验的公路隧道洞口浅埋段锁脚锚管优化分析

Optimization and Analysis on Anchor Pipe for Locking Foot of Highway Tunnel in Shallow-buried Section of Portal based on Orthogonal Test

为研究隧道洞口浅埋段锁脚锚管参数对施工变形的影响,以在建福州董奉山隧道为依托,基于正交试验原理,采用数值模拟和现场试验手段,考虑拱顶沉降和水平收敛两种情况下,对锁脚锚管各参数进行优化分析,并提出最优参数组合。结果表明:首根锁脚锚管的倾角对变形影响最大,其值与拱顶沉降大小呈正相关,与水平收敛呈负相关;锁脚锚管直径超过76 mm、长度超过4.5 m后,控制变形效果减弱,两锁脚锚管间的夹角对锁住钢拱架影响最弱;从对隧道施工变形控制上来看,各参数依次为倾角、直径、长度和夹角;两种工况下最优组合参数仅倾角有差异,即沉降控制为依据时,倾角为45°,水平收敛控制为依据时,倾角为0°,但考虑到施工经济性和快速性锁脚锚管最优参数取长度4.5 m,直径76 mm,首根锁脚锚管角度45°,锁脚间夹角15°。

In order to study the influence of anchor pipe parameters on construction deformation in shallow buried section of tunnel entrance, taking the Dongfengshan Tunnel in Fuzhou as project background, based on the principle of orthogonal test, numerical simulation and field verification are combined to optimize the influence of anchor pipe parameters under vault settlement and horizontal clearance convergence control, and the optimal parameter combination is proposed. The results show that: the inclination angle of the first anchor pipe has the greatest influence on the construction deformation, and its value is positively correlated with the roof settlement, and negatively correlated with the convergence of the horizontal convergence;when the diameter of the anchor pipe exceeds 76 mm and the length exceeds 4.5 m, the deformation control effect is weakened. The angle between the two locking foot anchor tubes has the weakest effect on locking the steel arch;from the perspective of the degree of influence on the tunnel construction deformation, the various factors are inclination angle, diameter, length and angle in sequence;the optimal combination parameters under the two working conditions differ only in the inclination angle, that is, when the settlement control is the basis, the inclination angle is 45°, and when the horizontal clearance convergence control is the basis, the inclination angle is 0°, but considering the construction economy and rapidity of the lock foot, the optimal parameter of the anchor pipe is 4.5m in length, 76mm in diameter, the angle of the first anchor pipe is 45°, and the angle between the lock legs is 15°.