原位扩建既有隧道主洞与竖井交叉段扩建型式

为了深入探究原位扩建既有隧道主洞与竖井交叉段的最优扩建型式，依托南岭隧道原位扩建工程，针对竖井与隧道主洞交叉段的扩建过程建立三维有限元模型，并研究单侧扩建、双侧扩建型式下围岩变形及应力随开挖过程的变化规律.考虑竖井与隧道的空间位置关系，基于太沙基理论提出不同扩建型式的隧道围岩压力计算公式.结果表明:两种扩建型式下围岩的变形速率均在掌子面距竖井与隧道交叉断面1倍洞径以内时较大；单侧扩建使围岩应力释放不均并形成偏压效应，产生较双侧扩建更大的围岩应力；扩建型式的选择对围岩压力的分布影响较大，围岩级别在Ⅲ～Ⅴ级时，围岩压力计算值由大到小排序为双侧扩建＞太沙基理论＞单侧扩建.

Expansion Type of In-situ Expansion of the Intersection Between Main Tunnel and Shaft in the Existing Tunnel

In order to explore the optimal in-situ expansion type of the intersection of the main tunnel and the shaft in the existing tunnel， a three-dimensional finite element model of the expansion process at the intersection of the main tunnel and the shaft was established based on the in-situ expansion project of the Nanling tunnel， and the changes of surrounding rock deformation and stress with the excavation process under the single-side expansion and double-side expansion were studied. Considering the spatial position relationship between the shaft and the tunnel， formulas for calculating the pressure of the surrounding rock of the tunnel with different expansion types were proposed based on Terzaghi′s theory. The results show that the deformation rate of surrounding rock within 1 time of the tunnel diameter between the tunnel face and the cross section of the shaft and the tunnel is larger. The single-side expansion makes the surrounding rock stress release unevenly and form a bias effect， causing a larger surrounding rock stress than that of the double-side expansion. The choice of expansion type has a great influence on the distribution of surrounding rock pressure， when the surrounding rock is in grade Ⅲ～Ⅴ， the calculated value of the surrounding rock pressure formula are the largest of the double-side expansion， followed by the Terzaghi′s theory， and the smallest for the single-sided expansion.