Comprehensive Influence Analysis of Multiple Parameters on the Safety Thickness against Water Inrush in Shield Tunnel

The present paper aims to study the mechanical mechanism and characteristics of water irruption from Karst cave. Combining the nonlinear seepage-pipe coupling model with the strength reduction method, the linkage analysis of fluid solid coupling and strength reduction method are constructed to study the whole process of confined Karst cave water inrush. Taking the water inrush accident of Shibaijing of the Qiyi mine in south China as an example, the instability mechanism of the water-proof rock pillar and evolution of water inrush are discussed. It is suggested that water discharge on the working face augments with the increase in the reduction factor of the water-proof rock pillar before the rock pillar loses its stability. Once the rock pillar becomes unstable, Karst water bursts from confined Karst cave in a pipe flow shape, and the water irruption quantity reaches the peak value in a short time by adopting the pipe flow to simulate and then decreases slowly. The hydraulic rough flow at the initial stage changes into pipe laminar flow finally in the process of Karst water inrush, due to the constraint of Karst cave water reserve. The conception for the safety factor of the water-proof rock pillar introduced, the relation of the safety factor, Karst cave water pressure, and thickness of the water-proof rock pillar are studied. It is proposed that thickness of the water-proof rock pillar whose safety factor equals 1.5 is regarded as the calculating safety thickness of the water-proof rock pillar, and the safety thickness of the water-proof rock pillar setting in mining engineering should be equal to the sum of the blasthole depth, blasting disturbance depth, and the calculating safety thickness. The reason leading to Karst water inrush of Qiyi Mine is that without advanced boreholes, the water-proof rock pillar is set so small that it could not possess safety margin, so the confined Karst cave water breaks the water-proof rock pillar and bursts out. Combining the solid fluid coupling theory, pipe flow theory, and strength reduction method, the nonlinear mechanical response of confined Karst cave water inrush is studied, which provides a new study method for the whole process of confined Karst cave water inrush.

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

10.21203/rs.3.rs-384740/v1 ◽

2021 ◽

Author(s):

Jiaqi GUO ◽

Wenlong Wu ◽

Xiliang Liu ◽

Xin Huang ◽

Zhengguo Zhu

Keyword(s):

Rock Mass ◽

Influencing Factors ◽

Water Pressure ◽

Water Inrush ◽

Surrounding Rock ◽

Karst Water ◽

Seepage Force ◽

Karst Tunnel ◽

Tunnel Face ◽

Safety Thickness

Abstract This paper took into account the adverse influence of the karst water seepage effect on the water-resistant rock mass. Based on the upper-bound theorem of limit analysis and the Hoek-Brown failure criterion, through a series of formula derivation, the expression of critical safety thickness of water-resistant rock mass of karst tunnel face was finally obtained. The paper 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 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.

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Influence Analysis of the Construction of Ground Building to the Underground Shield Tunnel Built Lately

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.243-249.3618 ◽

2011 ◽

Vol 243-249 ◽

pp. 3618-3622

Author(s):

Yan Ming Yao ◽

Shun Long Song

Keyword(s):

Fem Analysis ◽

Internal Force ◽

Shield Tunnel ◽

Time Interval ◽

Influence Analysis ◽

Consolidation Rate

The interval tunnel of Ningbo metro line 2 goes through the site of a car showroom project. By FEM analysis, the internal force of the tunnel is calculated under the ground upper load. From the engineering planning of the two projects, the time interval of the two projects is about six months to twelve months. When the interval tunnel begins to construct, the settlement of the foundation of the showroom is still not finished. By the analysis of consolidation rate of soil, the additional settlement of tunnel caused by the latter settlement of the showroom building is analyzed. And the safety of the tunnel is evaluated according to the analysis.

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Multiplexed FBG Monitoring System for Forecasting Coalmine Water Inrush Disaster

Advances in OptoElectronics ◽

10.1155/2012/895723 ◽

2012 ◽

Vol 2012 ◽

pp. 1-10 ◽

Cited By ~ 5

Author(s):

B. Liu ◽

S. C. Li ◽

J. Wang ◽

Q. M. Sui ◽

L. C. Nie ◽

...

Keyword(s):

Wavelength Division Multiplexing ◽

Axial Strain ◽

Water Inrush ◽

Pressure Sensors ◽

Mining Area ◽

Seepage Pressure ◽

Wavelength Division ◽

Multiple Parameters ◽

Set Up ◽

Temperature Strain

This paper presents a novel fiber-Bragg-grating- (FBG-) based system which can monitor and analyze multiple parameters such as temperature, strain, displacement, and seepage pressure simultaneously for forecasting coalmine water inrush disaster. The sensors have minimum perturbation on the strain field. And the seepage pressure sensors adopt a drawbar structure and employ a corrugated diaphragm to transmit seepage pressure to the axial strain of FBG. The pressure sensitivity is 20.20 pm/KPa, which is 6E3 times higher than that of ordinary bare FBG. The FBG sensors are all preembedded on the roof of mining area in coalmine water inrush model test. Then FBG sensing network is set up applying wavelength-division multiplexing (WDM) technology. The experiment is carried out by twelve steps, while the system acquires temperature, strain, displacement, and seepage pressure signals in real time. The results show that strain, displacement, and seepage pressure monitored by the system change significantly before water inrush occurs, and the strain changes firstly. Through signal fusion analyzed it can be concluded that the system provides a novel way to forecast water inrush disaster successfully.

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Calculation of the safety thickness of water inrush with tunnel axis orthogonal to fault

Arabian Journal of Geosciences ◽

10.1007/s12517-021-07297-8 ◽

2021 ◽

Vol 14 (11) ◽

Author(s):

Helin Fu ◽

Pengtao An ◽

Guowen Cheng ◽

Jie Li ◽

Zhen Huang ◽

...

Keyword(s):

Water Inrush ◽

Safety Thickness

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Freezing Occlusion for Inrush Damage of a Water Conveyance Tunnel under the Yangtze River: A Case Study in China

Quarterly Journal of Engineering Geology and Hydrogeology ◽

10.1144/qjegh2020-116 ◽

2021 ◽

pp. qjegh2020-116

Author(s):

Shulan Guo ◽

Changhong Yan ◽

Liangchen Yu ◽

Junqiang Sha ◽

Yang Zheng ◽

...

Keyword(s):

Yangtze River ◽

Water Inrush ◽

Damage Mechanism ◽

Shield Tunnel ◽

The Yangtze River ◽

Piezometric Head ◽

Permanent Occlusion ◽

Water Conveyance ◽

Recovery Program

Water inrush damage was observed in a shield tunnel under the Yangtze River. This is a rare occurrence in shield tunnels and thus requires the determination its causes and the establishment of the corresponding targeted recovery measures. In the current study we investigated the hydrogeological and geotechnical conditions of the area and evaluated the possible contributors to the damage mechanism, determining a biogas leakage as the cause. Based on the theoretical analysis, we proposed a freezing recovery program with the following measures: (i) dewater the piezometric head and release the biogas in the soils; (ii) create a freezing curtain; and (iii) drain the accumulated water and build a permanent occlusion at the 950th ring. Numerical simulations prior to the actual construction were performed to analyze the frozen range and frozen effect. Results revealed the temperature in the frozen area to be below -1°C, meeting the construction requirements. The proposed freezing technology was verified using the monitoring data of the thermometer hole. This work provides a way to the recovery of shield tunnels in deep-water areas.

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Model test to investigate waterproof-resistant slab minimum safety thickness for water inrush geohazards

Tunnelling and Underground Space Technology ◽

10.1016/j.tust.2016.11.004 ◽

2017 ◽

Vol 62 ◽

pp. 35-42 ◽

Cited By ~ 26

Author(s):

Hai-ming Jiang ◽

Lang Li ◽

Xiao-li Rong ◽

Ming-yang Wang ◽

Yuan-pu Xia ◽

...

Keyword(s):

Model Test ◽

Water Inrush ◽

Safety Thickness

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Influence of Water Inrush from Excavation Surface on the Stress and Deformation of Tunnel-Forming Structure at the Launching-Arrival Stage of Subway Shield

Advances in Civil Engineering ◽

10.1155/2019/6989730 ◽

2019 ◽

Vol 2019 ◽

pp. 1-20

Author(s):

Shusheng Lv ◽

Wen Liu ◽

Shihong Zhai ◽

Peishuai Chen

Keyword(s):

Simulation Analysis ◽

Coupling Effect ◽

Water Inrush ◽

Ground Surface ◽

Reinforced Soil ◽

Soil Reinforcement ◽

Shield Tunnel ◽

Deformation Properties ◽

Stress And Deformation ◽

Shield Machine

The launching-arrival stage of the shield is the most dangerous construction stage in subway construction. During the conversion process of the soil and air medium in the shield machine, water inrush at the excavation surface often occurs because of the effect of groundwater. Previous research has focused on the overall stress and deformation of existing tunnels caused by water inrush from the excavation face of the shield machine excavation stage. However, the stress and deformation states of the segments and anchors at different assembly locations of the tunnel, as well as the interaction between the soil reinforcement region and the segments and anchors in the launching-arrival stage have not been considered in previous studies. In this study, the inrush model of the launching-arrival stage of the subway shield was established by utilizing the equivalent refinement modeling technology and ABAQUS simulation analysis with consideration of the fluid-solid coupling effect of water and soil to study the influences of different water head differences on the mechanical and deformation properties of segments and anchors in shield construction under the conditions of water inrush on the excavation surface. The results showed that the water inflow from the tunnel excavation surface caused significant surface subsidence at the tunnel portal, vertical convergence at the cross section of the shield tunnel, and significant increases in the axial and shear forces on the bolt. In addition, based on the existing subway regulation, combined with the simulation results of soil reinforcement measures at different depths, the emergency control criterion for controlling water inrush on the excavation surface was established by using the depth of soil reinforcement. The minimum depth of the reinforced soil from the ground surface at 15 m is recommended to ensure construction safety of the subway shield at the launching-arrival stage.

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Effects of Water Inrush from Tunnel Excavation Face on the Deformation and Mechanical Performance of Shield Tunnel Segment Joints

Advances in Civil Engineering ◽

10.1155/2017/5913640 ◽

2017 ◽

Vol 2017 ◽

pp. 1-18 ◽

Cited By ~ 8

Author(s):

Tingsheng Zhao ◽

Wen Liu ◽

Zhi Ye

Keyword(s):

Mechanical Performance ◽

Coupling Effect ◽

Water Inrush ◽

Bending Moment ◽

Sharp Decrease ◽

Shield Tunnel ◽

Cross Sectional ◽

Tunnel Excavation ◽

Water Head ◽

Control Criterion

Water inrush from the excavation face often occurs in the current shield construction of metro tunnels. In this study, the discontinuity of shield tunnel lining and the interaction between the tunnel segments, the grouting layer, and the surrounding rock are considered. Based on the 3D nonlinear contact theory, a hybrid model of the shield tunnel is constructed. Considering the fluid-solid coupling effect of water and soil, the influences of different water head differences on the mechanical performance and deformation of segments and joints in the shield tunnel are studied. The water gushing from the excavation face leads to vertical convergence of the cross-sectional area of the shield tunnel, and joint opening and dislocation result in sharp decrease of the waterproof capacity of joints. Meanwhile, the stress in the vicinity of segment joints increases sharply, and local cracks occur in the segment lining. The axial force, shear force, and bending moment in the joint bolt are also significantly increased. Based on the current metro standard and the computational results in this study, an emergency control criterion is put forward by means of controlling the discharge of water: the water head difference over the excavation face is required less than 4.6 M.

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