Study on construction mechanical characteristics and pinch rocks reinforcement schemes of honeycomb tunnel clusters in Mountainous City

Abstract

Due to the growing need for underground space and the acceleration of urbanization, narrow clearance tunnel clusters are being created, making construction more challenging. This paper investigated tunnel clusters consisting of five parallel tunnels at Hongyan Village in Chongqing as a background project. The mechanical behaviour of the clusters has been studied by using three main methods as the following: model test, theoretical analysis, and numerical simulation. The induced forces characteristics in the pinch rock based on the stress correlation theory have been accomplished, with establishing a pinch-rock yielding reserve (YR) model for different pinch-rock reinforcement schemes to be compared with the other ones. The results can be introduced as the following: (1) During the stage of temporary support removal, the incremental displacement of the crown of each tunnel accounted for 6.25 %∼60.53 % of the total displacement. Moreover, it seems that the temporary support has a significant influence on the stability of the surrounding rock. (2) The value of YR depends on the position of the shear and tensile damage line, the “centre” and the “radius” of the Mohr’s circle. A smaller value indicates a higher tendency towards instability. (3) For the left pinch rock that has been disturbed many times during the construction of the tunnel clusters, the combination of prestressed tie-back anchors- grouting is preferred, which raises the maximum value of the YR to 1,324.62 kN/m.