Mechanical Behavior and Excavation Optimization of a Small Clear-Distance Tunnel in an Urban Super Large and Complex Underground Interchange Hub

Abstract

Close excavation section spacing, the mutual influence and interpenetration of various processes, and the multiple disturbances of the middle rock pillar in a small clear-distance tunnel pose great difficulty to construction. This study adopted the small clear-distance tunnel of Xiamen Haicang Evacuate Channel as the research object. The tunnel belonged to a small clear-distance tunnel in an urban super large and complex underground interchange hub where complex adjacent small clear-distance tunnels were adopted. ABAQUS was used to analyze the influence of different excavation schemes, lithological grades, and footage lengths for tunnel stability. The deformation and stress characteristics of the tunnel’s surrounding rock and lining structure in different excavation schemes (full section method, bench method, center diaphragm (CD) method, and double wall heading method), lithological grades (III, IV and V), and footage lengths (3 m, 4 m and 5 m) were introduced. The results showed that the double wall heading method could effectively control the horizontal displacement of the hance, and the overall stress state of the lining in the CD and double wall heading methods were reasonable. The vertical displacement of the surface and vault was positively correlated with the elastic modulus of the rock mass. When no temporary support was present in the grade V rock mass, the area from the hance to the arch foot was prone to large deformation. Reducing the footage was beneficial to controlling the deformation of the vault and hance. This study can provide a reference for the on-site construction of small clear-distance tunnels.

Mechanical Characteristics of Surrounding Rock for Neighborhood Tunnels Using the Schwarz Alternating Method Model: A Case Study

“…In favorable geological conditions, the full-face method [7] or the benching method [8] are commonly adapted. In challenging geological conditions, options include the center diaphragm method with multiple sections [9,10], the cross-diaphragm method [11,12], or the method of circular excavation with reserved core soil [13]. For the study cases where the thickness of the interlaid rock is small, it is necessary to optimize conventional excavation methods.…”

Research on Construction Sequences and Construction Methods of the Small Clear-Distance, Double-Arch Tunnel under an Asymmetrical Load

“…Numerical simulation was widely used because of its convenience and low cost in recent years. Wang et al [19] used numerical simulation to study the mechanical response of a small clear-distance tunnel in Xiamen and compared the mechanical response of the tunnel under different excavation methods, different feeds, and different surrounding rock grades. Ng et al [20] investigated the interaction of a large-section parallel tunnel in hard clay soils by building a three-dimensional finite element model.…”