Water Inrush In Tunnels Research Articles

Correction to: A failure case study of tunnel water inrush source identified by statistical analysis model

Correction to: A failure case study of tunnel water inrush source identified by statistical analysis model

Evolution Mechanism, Monitoring, and Early Warning Method of Water Inrush in Deep-Buried Long Tunnel

Water inrush is a serious disaster in tunnel construction. Because the process of water inrush is complicated and there is no effective monitoring and early warning method, the control of water inrush disaster is passive. Firstly, the failure mode and determination method of safety thickness of the antioutburst structure are summarized. The key breakthrough directions and development trends of water inrush mechanism was analyzed. Secondly, the sensitivity ranking and the adjunct characteristics of different types of precursor information are determined by the model test. An improved scheme of microseismic monitoring technology is proposed to locate the spatial position of the water inrush channel, and a multi-information time-space integrated monitoring method for an antioutburst structure is established. By analyzing the evolution law of multi-information in the process of water inrush, the evolution model and its identification method are put forward. Finally, the level of water inrush was determined through the analysis of the dynamic and static reserves of disaster source, and a multilevel and comprehensive warning system of tunnel water inrush is established. Through the remote real-time monitoring and early warning platform and its engineering application, the early warning of water inrush time trend and the early warning of water inrush rupture space position are realized.

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.

A failure case study of tunnel water inrush source identified by statistical analysis model

A failure case study of tunnel water inrush source identified by statistical analysis model

Numerical characterization of groundwater flow and fracture-induced water inrush in tunnels

Recently, the rapid increase in tunnel construction in karst areas across China has attracted considerable attention. However, frequently occurring groundwater inrush hazards induced by fractures within rocks are one of the greatest challenges faced during tunnel excavations. In this paper, we present a numerical investigation on the effect of fractures on fluid flow, considering the different types of discontinuities. A conceptual model of fracture-induced water inrush, which emphasizes the evolution of fracture connectivity, was developed to investigate the fluid flow through fractured rocks and consequently study the water inrush mechanism. The numerical results indicate that the rock fracture serves as the preferential flow channel and the aquifuge acts as a barrier to the groundwater flow. Groundwater is transported mainly through fractures with higher permeability. A case study demonstrated the accuracy of the proposed conceptual model. Finally, the influences of the connected fractures on water inflow and the sensitivity of the different types of connected fractures to tunnel inflow were investigated using the orthogonal experiment method. The proposed approach and results may contribute to the investigation of groundwater movement in fracture system, thereby providing a basis for the water-inrush theory and prevention of damage in karst areas.

Theoretical Analysis on Safety Thickness of the Water-Resistant Rock Mass of Karst Tunnel Face Taking Into Account Seepage Effect

We took into account the adverse influence of the karst water seepage effect on the water-resistant rock mass of karst tunnel face. Based on the upper-bound theorem of limit analysis and the Hoek–Brown failure criterion, we obtained the calculation method of the critical safety thickness of the water-resistant rock mass. We carried out a feasibility analysis, an analysis of influencing factors and a comparative analysis with previous related research achievements of this method. The results showed that: (1) With the decrease of surrounding rock grade, the safety thickness of water-resistant rock mass gradually increased, and the safety thickness of surrounding rock at all grades remained within a reasonable range. (2) The safety thickness decreased as the compressive strength, the tensile strength and parameter A increased, and it increased as the karst water pressure, the tunnel excavation height, and parameter B increased. (3) The change trend of the safety thickness with the influencing factors was completely consistent under the two conditions of considering and without considering the seepage effect, and the safety thickness with considering the seepage force was greater than that without considering the seepage force. Taking the Yunwushan Tunnel of Yiwan railway as an example, the critical safety thickness of the water-resistant rock mass was calculated and the calculated value was in good coincidence with the safety thickness adopted in the actual project. The research results are of great significance to prevent the occurrence of high pressure filling karst geological disasters such as water inrush in tunnels.

Mechanical Mechanism of Hydraulic Fracturing Effect Caused by Water Inrush in Tunnel Excavation by Blasting

When the deep tunnel is excavated, the pressure of the confined water is relatively high, causing the water inrush to have a hydraulic fracturing effect. The method of theoretical analysis was adopted to study this effect. A mechanical model for fracturing water inrush under blasting excavation conditions was established. The water inrush under this condition is the result of the combined action of static load (water pressure and in situ stress) and dynamic load (explosive stress wave). According to whether the normal stress on the hydraulic crack surface was tensile stress or compressive stress, two types of water inrush were proposed: water inrush caused by tensile-shear damage and water inrush caused by compression-shear damage. These two types of critical water pressures were calculated separately. The relationship between critical water pressure, in situ stress, and blasting disturbance load was given, and a pore water pressure splitting factor was introduced in the calculation process. The theoretically obtained critical water pressure had been verified in the case of water inrush in a deep-buried tunnel. The established theory can guide field practice well.

Noise reduction method of microseismic signal of water inrush in tunnel based on variational mode method

Noise reduction method of microseismic signal of water inrush in tunnel based on variational mode method

A new method for risk assessment of water inrush in a subsea tunnel crossing faults

The geological conditions of subsea tunnels are extremely complicated. When crossing faults, water inrush disasters are prone to occur under the combined action of seawater pressure, geological structure, and construction disturbance. An optimal combination weight-improved grey relational analysis (GRA) method is proposed here to evaluate the risk of water inrush in subsea tunnels through faults. Eight main factors are selected from fault zone properties, fault structure characteristics, engineering factors, and construction factors as risk assessment indexes, and the risk is divided into four levels. The subjective and objective weights are determined using the improved G1-method and entropy weight method, and the optimal combination weight is calculated based on the minimum discriminant information principle and the Lagrange multiplier method. The improved GRA considering the evaluation criteria interval is used to determine the correlation degree of the water inrush risk level, and the maximum correlation degree criterion is adopted to judge the risk level. The method is applied to the Qingdao Jiaozhou Bay subsea tunnel to assess the water inrush risk crossing faults, and the assessment results are basically consistent with the actual engineering situation. This study provides a practical reference for the risk assessment of water inrush in subsea tunnels.

Analysis of Tunnel Water Inrush Considering the Influence of Surrounding Rock Permeability Coefficient by Excavation Disturbance and Ground Stress

Affected by the coupling of excavation disturbance and ground stress, the heterogeneity of surrounding rock is very common. Presently, treating the permeability coefficient as a fixed value will reduce the prediction accuracy of the water inflow and the external water pressure of the structure, leading to distortion of the prediction results. Aiming at this problem, this paper calculates and analyzes tunnel water inflow when considering the heterogeneity of permeability coefficient of surrounding rock using a theoretical analysis method, and compares with field data, and verifies the rationality of the formula. The research shows that, when the influence of excavation disturbance and ground stress on the permeability coefficient of surrounding rock is ignored, the calculated value of the external water force of the tunnel structure is too small, and the durability and stability of the tunnel are reduced, which is detrimental to the safety of the structure. Considering the heterogeneity of surrounding rock, the calculation error of water inflow can be reduced from 27.3% to 13.2%, which improves the accuracy of water inflow prediction to a certain extent.

Treatment Design and Construction Strategy for Tunnel Mud and Water Inrush Disaster

With the rapid development of the transportation industry in China, the number and scale of tunnel construction are increasing. Tunneling through fault zones and other complex geological environments is becoming more and more common. In the construction of highway tunnels, due to the special geographical environment and complex geological conditions, mud and water inrush often occur in the tunnel. Water inrush disasters pose a major risk to the construction of highway tunnels and affect the normal construction of highway tunnels. This paper combines the engineering background of the tunnel mud and water inrush accidents, carries out evaluation on the accident treatment measures and the treatment efficiency, and summarizes the main concerns in the construction process and the technical guidelines for dealing with the tunnel mud and water inrush.

Applicability Analysis of Microseismic Technology in Tunnel Water Inrush Monitoring

Water inrush disaster is one of the most serious geological disasters in tunnel construction. There are still some problems in the existing researches, such as the activity information of surrounding rock is difficult to obtain, the mechanism of water inrush disaster is unclear, the correlation between water inrush disaster and microseismic (MS) information is missing, which have caused the water inrush disaster to be passively controlled. Combining with the practical experience of tunnel engineering, the application problems of MS technology in tunnel engineering is summarized, which provides ideas for monitoring of surrounding rock activity. The formation mechanism of water inrush disaster caused by rock mass fracturing and filling medium instability has been revealed. The MS characteristics of the water inrush channel in different water inrush disasters have also been revealed. The MS response characteristics of water inrush and rockburst disasters are compared, which provides guidance for the improvement of MS monitoring technology and the analysis of effective MS information. The compression failure test of limestone under saturated and natural conditions is carried out. The results show that the presence of water weakens the ability of rock to store energy. The acoustic emission (AE) phenomenon is weaker in the process of saturated limestone failure, which increases the difficulty of AE monitoring. The number of AE events of natural limestone and saturated limestone shows a slow increase to a sudden increase in the process stress loading, which can be regarded as an important precursor of rock failure.

Mitigation of Karst Tunnel Water Inrush during Operation in Seasonal Variation Zone: Case Study in Nanshibi Tunnel

AbstractA discrimination method with drainage or plugging that mitigates the karst tunnel water inrush during operation in a seasonal variation zone is proposed to cope with repeated water inrush d...

Theoretical Research and Numerical Simulation on Water Resistance Mechanism of Textile Bag in Water Passage

It is an important problem in the mine water disaster prevention and control to control the large passage moving water. Traditional grouting technology is to put coarse aggregate and fine aggregate downward first and then grouting treatment. But the aggregate and cement flow distance is long, consumption is large, cost is high, and easy to appear secondary water inrush. Centering on the technical difficulties in the rapid construction of the blocking body of the moving water passage, a water-blocking textile bag was invented. The purpose of blocking the tunnel water inrush was achieved by grouting inside the bag body, which fundamentally realized the rapid blocking of the large passage through water under the condition of moving water. However, the mechanism, water plugging law, and design parameters of water blocking roadway with textile bag are still unclear. In this paper, the slip law and stability of the textile bag in the moving water and the deformation characteristics caused by the dynamic water pressure are theoretically analyzed and simulated. Through theoretical analysis, the ultimate antihydraulic stress value of a textile bag of a certain specification is calculated, and the parameters of the textile bag that affect the stability of the bag body are also determined. Xflow was used for numerical simulation analysis to study the deformation characteristics of the textile bag under water and the law of water barrier. The simulation analysis focuses on the water resistance effect and flow field distribution characteristics of the textile bag in the water passage under the condition of low flow rate and low pressure, as well as the stability and self-deformation characteristics of the textile bag under the condition of high flow rate and high pressure. The accuracy of the limit resistance to water pressure of the textile bag obtained from theoretical analysis is verified. The results show that the theoretical analysis is consistent with the simulation results. The textile bag can realize the fast controllable plugging of the large water passage of moving water within the limit of the antihydraulic stress.

Study on an improved real-time monitoring and fusion prewarning method for water inrush in tunnels

As a common geological hazard in tunnel construction, monitoring and early warning is an effective way to prevent and control the occurrence of water inrush. However, the current monitoring and early warning method has areas that require improvement, including a lack of theoretical basis in monitoring information, the inability of real-time monitoring technology during tunnel construction, and the difficulty of fusing massive monitoring data. Therefore, a new real-time monitoring and fusion prewarning method for tunnel water inrush was proposed. First, sensitive information on the evolution process of water inrush was analyzed. Second, an improved method for the accurate measurement of sensors and wireless transmission bands suitable for complex tunnel environments was studied, and a real-time monitoring system for water inrush in tunnels was established. Third, a new early warning method for multi-information interval fusion based on evidence and fuzzy set theory was presented to realize the fusion of massive monitoring data in time series. Furthermore, the proposed method was successfully applied to the crossing river section of the Yuelongmen tunnel. The results had good agreement with the actual excavation situation, which verified that the proposed method was effective and practical.

Model on Improved Variable Weight-Matter Element Theory for Risk Assessment of Water Inrush in Karst Tunnels

This paper presents an improved risk assessment model to evaluate the risk of water inrush in karst tunnels based on matter element theory and ideal point method. The 4 first-grade evaluation indexes and 13 s-grade factors are selected to establish the evaluation index system by considering the occurrence conditions of water inrush. All second-grade evaluation indexes are quantitatively divided into four risk grades. Based on improved Analytical Hierarchy Process and Triangular Fuzzy Number, the constant weights are obtained. The variable weights are determined according to the state variable weight theory and the values of evaluation indexes. The risk grade of water inrush is recognized by the closeness degree analysis. The proposed risk assessment model was applied to 3# inclined shaft of Yuelongmen tunnel, and the accuracy of the assessment result was verified by comparing with advance geological forecast and excavation. This proposed model provides a practical tool to evaluate the risk of water inrush in karst tunnels.

Risk assessment of water inrush in karst shallow tunnel with stable surface water supply: Case study

Water inrush generally has a serious impact on karst shallow tunnel construction. Because of in situ fault fracture zone, high degree of weathering and poor quality of rock mass,. karst shallow tunnel would therefore face high risk of water inrush from surface during the disturbance of construction. In addition, the greater the surface water flow would contribute higher probability of water inrush under the same disaster-causing environment. However, existing research has paid less attention to the influence of surface water flow on faults or fissures water inrush. In this study, a risk assessment system of water inrush in karst shallow tunnel with stable surface water supply was firstly proposed on basis of Qinling Water Conveyance Tunnel and the Yuelongmen Tunnel in China. Each indicator was quantified and classified into four risk levels by the attribute mathematics theory and analytic hierarchy process, the degree of confidence criterion was then applied to identify the risk level of the water inrush. The evaluation results were finally verified by actual scenario on site to confirm the validity of this risk assessment system in karst shallow tunnel with stable surface water supply. Accordingly, the proposed method could be popularized and applied in future tunnel projects, because it could provide safe construction reference for karst shallow overburden tunnel with stable surface water supply.

The non-Darcy characteristics of fault water inrush in karst tunnel based on flow state conversion theory

The fault water inrush is a key factor which leads to tunnel construction in karst regions. Based on the fluid mechanics principles, the paper addresses a numer?ical coupled model for karst fault tunnel with COMSOL Multiphysics software. Besides, the Darcy law equation, Brinkman equation, and Navier-Stokes equation are inserted to stimulate the steady flow of aquifer, the non-linear seepage of fault and the free flow in tunnel excavating area in software, respectively. Then, the pres?sure and flow velocity in three flow fields are analyzed under different permeability ratios in numerical model. It is shown that the fault permeability is the key factor affecting water inrush, and that the pressure and flow velocity change visibly in adjacent domains between two flow fields.

Water Inrush Risk Assessment Based on AHP and Advance Forecast Approach: A Case Study in the Micangshan Tunnel

Water inrush is a serious geological disaster in tunnel. For the effective prevention and control of the occurrence of water inrush, a static‐dynamic water inrush risk assessment method is proposed by considering the Micangshan tunnel as an example. First, four possible types of water inrush phenomenon are identified based on the geological and hydrogeological conditions of the tunnel: water inrush in water‐bearing cracks, fault fracture zones, karst pipelines, and karst caves. Next, evaluation indexes that affect water inrush are determined. By combining the index weight value calculated by analytic hierarchy process (AHP) with the index quantitative value, the static water inrush disaster evaluation model is established, which provides a basis for tunnel design. Finally, with the combination of the static evaluation model and advanced forecast method, a dynamic risk prediction method of water inrush is established, which provides guidance for safe construction. The results confirm that the proposed method is a reliable theoretical basis for early assessment and prediction of tunnel water inrush disasters.

Prediction of Water Inrush in Long-Lasting Shutdown Karst Tunnels Based on the HGWO-SVR Model

It is very important to predict the long-term shutdown karst tunnel water inrush for preventing tunnel construction accidents. However, it is urgent to study a new prediction model to solve the problems of insufficient sample size and low prediction accuracy for long-term shutdown karst tunnel water inrush prediction. In this study, the water inrush and atmospheric rainfall in a tunnel project in China were monitored for over five months. By adopting hybrid grey wolf optimization (HGWO) algorithm and support vector regression (SVR) method, the HGWO-SVR tunnel water inrush prediction model was proposed. The atmospheric rainfall of the day and yesterday and yesterday’s water inrush were considered in the HGWO-SVR model, and the model was used to predict the tunnel water inrush. The results show that the predicted water inrush value is basically consistent with the measured value. After the parameters of SVR model are optimized by HGWO algorithm, the HGWO-SVR prediction model has the advantages of high precision and less sample demand. The model is more suitable for the prediction of long-term shutdown tunnel water inrush with less measured sample. Thus, the proposed prediction model can effectively be used as a new approach for tunnel water inrush in some similar projects.