Risk Analysis of Tunnel Water and Mud Inrush Using Interpretive Structural Modeling and Fault Tree

Water and mud inrush is a common geological hazard in tunnel construction. Risk analysis of tunnel water and mud inrush has always been an important subject. In order to avoid the geological hazard, this paper presents a risk analysis model of tunnel water and mud inrush. The model combines the interpretive structural modeling method (ISM) and fault tree analysis (FTA). Relying on the Qinyu tunnel in the Weiwu expressway project, water and mud inrush risk factors are obtained by using ISM. Fundamental risk factors include formation lithology, attitude of stratum, strata combination, topography and geomorphology, geological structure and weather. ISM core risk factors are used as FTA basic events. Fuzzy importance of FTA basic events is obtained by using fuzzy interval calculation. The results show that geological structure is the primary risk factor causing Qinyu tunnel water and mud inrush. The model achieves qualitative and quantitative analysis of tunnel water and mud inrush. It accurately determines the main factors affecting the tunnel water and mud inrush, which is conducive to accident prevention.

Smart Risk Assessment Model of Water Inrush in Submarine Tunnel through AHP-TOPSIS and Intelligent Computing

In tunnel construction, water and mud inrush disasters are prone to occur when the tunnel traverses water-rich faults, which leads to structural damage and tunnel instability, which is one of the most severe hazards in tunnel excavation and construction. This paper proposes a method of combining AHP and TOPSIS. The weights are determined through the analytic hierarchy process utilizing expert scoring. The determined weights are evaluated and predicted by TOPSIS for water inrush risk. The Jiaozhou Bay Subsea Tunnel is used as a case to carry out the tunnel crossing the fault zone. Water inrush risk prediction provides a new idea for water inrush risk prediction.

Development and Application of the 3D Model Test System for Water and Mud Inrush of Water-Rich Fault Fracture Zone in Deep Tunnels

In order to study the evolution process, damage characteristics, and occurrence mechanism of water and mud inrush disaster in deep tunnel fault zone with infiltration instability under complex conditions, a set of the three-dimensional physical model test systems of water and mud inrush flow-solid coupling in tunnel fault zones is developed. The system mainly comprises a rigid test frame, ground stress loading system, hydraulic loading system, multiple information monitoring and acquisition system, and mud and water protrusion recovery system. The system’s main features are that it can meet the model’s simulation of the ground stress field, water pressure, and other complex environments subjected to ground stress, and water pressure gradients can be controlled. The system is characterized by high rigidity, high-pressure strength, visualization, good sealing, and expandability. Taking the water fault zone of a well in the Dazhu Mountain Tunnel of the Darui Railway as the research object, the new fault zone and surrounding rock similar materials applicable to the flow-solid coupling model test are designed using the self-developed flow-solid coupling similar materials. The system is used for model tests to reveal the spatial and temporal changes of the surrounding rock stress field and seepage field during the tunnel excavation process. The test results show that the system is stable and reliable, and the research method and results are of guiding significance to the research of the same type of underground engineering.

Analysis of Water and Mud Inrush in Tunnel Fault Fracture Zone—A Case Study of Yonglian Tunnel

Water and mud inrush disaster is easily induced during tunnel construction through water-rich fault fracture zones. In this paper, based on the field data, the process of water and mud inrush in tunnels is introduced in detail, and generation conditions and evolution mechanisms have been analyzed. Results show that the key factors of water and mud inrush include poor strata lithology, abundant groundwater and tunnel excavation disturbance. These key factors provide material conditions, source power and start-up conditions for water inrush, respectively. The evolution process of water and mud inrush can be divided into three stages: generation, development and occurrence. During generation stage, a seepage channel expands continuously, with water flow increasing gradually until a large range of loose zone is formed. During the development stage, a large amount of groundwater and a large range of softened muddy rock mass accumulates around the tunnel. During the occurrence stage, the “protective layer” and initial supports suddenly lose stability and are destroyed. These research results could provide some references for the effective prediction and forewarning of similar engineering disasters.

Groundwater Inrush Control and Parameters Optimization of Curtain Grouting Reinforcement for the Jingzhai Tunnel

Based on the systematic study on the characteristics of water and mud inrush during the excavation of Jingzhai tunnel, the mechanism of water inrush seepage transformation caused by excavation disturbance is analyzed. By means of electromagnetic geophysical prospecting, the potential water bearing area of the tunnel was analyzed. The constitutive model of rock mass and grouting parameters are considered in the numerical simulation. The law of tunnel crack initiation and expansion under different curtain grouting parameters is proposed. The characteristics of seepage water inrush caused by excavation are described. It is considered that there are three stages in the seepage characteristics of tunnel: incubation, sudden, and stable. Numerical simulation was used to analyze the crack propagation track and water inflow characteristics under the grouting thickness of 3 m, 5 m, and 7 m. When the curtain grouting thickness was 3 m, the fracture field penetrated the curtain grouting area. The dominant seepage channel is formed, which greatly increases the probability of water inrush. When the curtain thickness is 5~7 m, the expansion of the crack zone can be controlled basically, so that the fracture and water bearing rock layer cannot form a seepage channel. At last, the grouting scheme of 6 m thick grouting and 20 m advanced grouting was selected, and the water seepage was reduced by 83%.

Risk assessment of water and mud inrush in a tunnel in Chongqing based on analytic hierarchy process

Water and mud inrush is one of the typical geological hazards during tunnel construction in karst area. In weight of water or mud inrush risks of karst tunnels are studied and the index system for water and mud inrush risk evaluation is established based on analytic hierarchy process. The analysis shows that geological structure, formation lithology and groundwater level are the main control ingredients of water or mud inrush risk；geographic and geomorphic conditions, attitude of rock formation are the minor significant factors；surrounding rock mass classification , rainfall are the least important elements. Aiming at a tunnel in Chongqing, combining with the actual geological situation of the tunnel site, the evaluation model is used to evaluate the risk of water and mud inrush in each section, which provides a certain theoretical basis for the prevention and control of water and mud inrush disaster during the tunnel construction.