Experimental and Numerical Investigation on Bearing Capacity of Circumferential Joint of New Spatial Steel Tubular Grid Arch in Mined Tunnel

Yuan Song,Zhaoping Li,Xudong Zhang,Mingli Huang,Xingxin Peng

doi:10.3390/sym12122065

Yuan Song, Zhaoping Li + Show 3 more

Open Access

https://doi.org/10.3390/sym12122065

Copy DOI

Abstract

Under the circumstance of soft fractured surrounding rock with high geo-stress, the support technology of tunnel has become a major challenge. Traditional I-shaped steel and bar lattice girder, which cross-sections are often designed to be left-right symmetrical, may have insufficient strength and stiffness. Based on the concept of symmetry, a new support technology of spatial steel tubular grid (SSTG) arch is designed with high strength and large stiffness. In order to clarify the mechanical properties and failure mechanism of SSTG arch used as primary support, through laboratory and numerical experiments, this paper carries out the bending tests for the circumferential joint of SSTG arch components combined with the excavation tunnel project of Panyu Square Station in Guangzhou, and the analyses of the ultimate bearing capacity, deflection displacement, failure modes, and stress–strain evolution laws of joint components are conducted in detail. The results show that during the whole process of loading, the arch components have experienced elastic growth stage, plastic development stage, and final failure stage. The average ultimate bending capacity of SSTG arches is 340.5 kN·m, and the joint opening is 13.9 mm. The joint form of high-strength bolt + rigid flange plate proposed in the paper has reasonable stress state and high safety redundancy, which can bear the load of surrounding rock effectively, and ensure the safety in tunnel construction. The research results could provide a theoretical basis for the design and application of SSTG arch support in related projects.

Highlights

In recent years, with the rapid development of China’s transportation construction, the traffic tunnel construction is developing to the direction of large scale and deep buried
Domestic and foreign scholars have done a lot of research on the optimization design of primary support, the mechanical characteristics of composite support structure considering shotcrete, and the influence on support effect
The results indicate that the main limb steel tubes have large deformation and the maximum displacement occurs at the joint

Summary

Introduction

With the rapid development of China’s transportation construction, the traffic tunnel construction is developing to the direction of large scale and deep buried. A new type of three limb grid steel frame with 8-shaped reinforcement was first designed in Germany [3], and the rationality and applicability of the structure design were proved by practical engineering application On this basis, some researchers had carried out the structural parameter optimization, and obtained the deformation characteristics, ultimate bearing capacity, and failure mode of different forms of grid arch through the mechanical performance test of bending load [4,5,6]. Considering the obvious limitations of bolt-mesh-shotcrete support in high geo-stress soft rock tunnel [16,17], several new high-strength steel tube confined concrete arch support systems were proposed, such as UCC arch, CCFST arch, and SCFST arch, which were successfully applied to the field test, and forming a tunnel assembly confined concrete construction system [18,19,20,21,22,23,24,25]

Methods

Results

Conclusion