Abstract
The bearing capacity of the tunnel structure is the essential basis for the structural safety of tunnel engineering. Due to the unpredictability and uncertainty in the tunnel’s surrounding environment, a systematic and unambiguous study on the bearing capacity of the tunnel structure is still lacking. The analysis framework of the bearing capacity of the tunnel structure is discussed and a method describing the bearing capacity loss of the tunnel structure is proposed in this paper. Furthermore, the loss laws of the tunnel structure bearing capacity under various characteristic factors are preliminarily investigated, and suggestions on the research of bearing capacity are put forward. First, the current research contents and methods of the tunnel structure technical status, mechanical characteristics, and bearing performance (directly mentioned) are summarized, the relevant concepts related to tunnel structure bearing capacity are analyzed, and it is clarified that the bearing capacity loss of the tunnel structure can be considered according to the technical status of lining damage preliminary. Then, based on analysis of main causes and influence path of the bearing capacity loss, the influencing factors of the bearing capacity of the tunnel structure are attributed to external load action (i.e., all external causes acting on the tunnel structure in the form of external loads) and material deterioration (i.e., all internal causes leading to the decrease in mechanical properties such as structure strength/stiffness). Several typical factors are listed with specific examples, respectively. Considering the uncertainty of the absolute value of the bearing capacity caused by the surrounding environment of the tunnel, a method describing the bearing capacity of the tunnel structure using relative loss rate and relative value of index is proposed based on the current relevant analysis data of mechanical characteristics of the tunnel structure. Based on the given definitions and rules, the related data on the quantitative analysis of mechanical characteristics of lining structure reported in the literature are statistically analyzed again from the view of loss laws of the bearing capacity. Taking three factors including crack, insufficient lining thickness, and cavity as examples, the corresponding model of the bearing capacity loss is preliminarily analyzed and interpreted. The simplest linear model can be employed to preliminarily describe the relationship between defect indexes and relative loss rate of the bearing capacity, especially pertinent mechanical data collected from numerical analysis. Moreover, the loss laws of the bearing capacity in practical analysis and model tests (especially when the variation range of factors is wide) can be simulated by a logistic growth model. Through the analysis of the typical factor model, the key points of the research on the bearing capacity of the tunnel structure are discussed, and some suggestions are put forward for the follow-up related research.
Highlights
Tunnel engineering, a branch of underground engineering, generally has randomness and uncertainty in its surroundings
The analysis framework of the bearing capacity of the tunnel structure is discussed and a method describing the bearing capacity loss of the tunnel structure is proposed in this study
Loss laws of the bearing capacity of the tunnel structure under different characteristic factors are preliminarily researched based on relevant mechanical data of the tunnel structure
Summary
A branch of underground engineering, generally has randomness and uncertainty in its surroundings. There are still significant challenges in accurately assessing the bearing state and safety characteristics of tunnel lining structure, such as accurately determining the actual stress state and the characteristics and process of structural failure. For the mechanical properties of in-service tunnels, most existing studies have concentrated on analyzing the development process and change features of stress, deformation, and failure of the tunnel structure under defect conditions. The existing studies mainly have focused on the evolution process, displacement properties, failure mode, internal force analysis, and variation laws of the tunnel-lining safety factor under defect conditions. Some studies have only focused on the mechanical characteristics and damage evolution law of surrounding rock and lining, lacking the corresponding analysis of the bearing capacity
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