Experimental study on physical modeling of deformation control effects of NPR anchor cable primary support structures in tunnels through faults

TaBaiyi tunnel is located in the Yunnan plateau mountainous area. The tunnel in the process of crossing the shattered fault zone paragraph, loose, fractured rock in the multi-field stress coupling, the surrounding rock large deformation, and other damage phenomena frequently occur, causing the near ordinary section of the initial support structure of the phenomenon of secondary subsidence damage to the safety and cost of the tunnel brought great difficulties. This study conducts physical modeling tests to investigate the effectiveness of the NPR anchor cable support system for tunnels penetrating shattered fault zone at various depths. It employs strain gauges, anchor cable axial force gauges, infrared cameras, and a non-contact strain measurement system (DIC) to record the displacement field, mechanical response, and the transformation pattern between energy fields of the surrounding rock and the support structure during the tunnel excavation. A 100 m experimental section of research is performed at the project site to verify the effectiveness of the support. The results indicated that excavation in the shattered fault zone can destroy the stress equilibrium between the surrounding rock and the support structure in the tunnel's ordinary section, accelerating the settlement and deformation rate of the surrounding rock. In addition, the NPR anchor cable support system can control the deformation of the surrounding rock, providing a theoretical foundation and practical guidance for the design of support for tunnels through shattered fault zone in similar engineering contexts.