Research on Support Control of New Materials and Structures for Deep Buried Complex Soft Rock Tunnel with Large Deformation

Currently applied underground space technology support of steel materials and concrete materials which generally have low strength, poor ductility and other characteristics, cannot meet the complex geological environment of soft rock large deformation area control requirements; so the research of high strength and high toughness of steel materials and concrete coupling, new steel arch support system is the top priority to deal with the soft surrounding rock settlement. Taking high strength and high preload negative Poisson's ratio effect material (NPR steel bar) coupled with high ductility concrete (HDC) and NPR steel coupled with double-layer truss as the background of the study, the supporting effect of new material NPR steel bonded with HDC concrete and new material NPR steel coupled with new structural truss was investigated by means of indoor experiments (dimensions, fiber admixture, fiber type, anchoring length, and rebar material), numerical simulation, and on-site monitoring. The research showed that: (1) The strength of NPR steel combined with HDC concrete is 45–75% higher than that of conventional steel combined with ordinary concrete. (2) Under the coupling effect of NPR steel and double-layer truss, the collapse of surrounding rock in large deformation tunnels with soft rock across fault fracture zones can be controlled within 250 mm, giving full play to its compensating mechanical effect. Two new materials (NPR steel and HDC concrete) and a new structure (double truss) provide scientific basis for the support of large deformation tunnel in soft rock under complex geological conditions.