Stability Analysis of Large Underground Station Based on Coupled Fluid-Solid Theorem

2013 ◽  
Vol 748 ◽  
pp. 1104-1108
Author(s):  
Rui Lang Cao ◽  
Shao Hui He ◽  
Fang Wang ◽  
Fa Lin Qi
Keyword(s):  
Pressure Distribution ◽  
Pore Pressure ◽  
Surrounding Rock ◽  
Three Dimensions ◽  
Lagrangian Analysis ◽  
Principal Stresses ◽  
Construction Methods ◽  
Study Results ◽  
Underground Station ◽  
The Stability

Tunnelling may disturb the intrinsic balance of a stratum, and result in accidents like caving or gushing. In order to assess the security of underground station project, numerical analysis for the stability of surrounding rock was done with fast Lagrangian analysis of continua in three dimensions (FLAC3D), Multiple factors were considered, including surrounding rock classes, tunnel depths, groundwater tables, construction methods and initial supporting systems. According to the results of principal stresses, displacements, plastic zones, pore pressure distribution and the mechanical characters of supporting system including anchors and shotcrete, the seepage mechanism of underground station has been discussed. The pore pressure distribution of deep-buried tunnel was studied as well. The study results can provide a theoretical basis for the design of tunnel and underground works in aquifer strata.

scholarly journals Study on Identification of Construction Method for Ultra-Large-Span Tunnel

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Xu Chongbang ◽  
Qin Youlin
Keyword(s):  
Rock Strength ◽  
Construction Method ◽  
Surrounding Rock ◽  
Orthogonal Test ◽  
Tunnel Construction ◽  
Test Model ◽  
Large Span ◽  
Construction Methods ◽  
The Stability

Although the determination of tunnel construction methods is extremely critical for the construction of ultra-large-span tunnels, the determination of construction methods is still at a qualitative level, which relies on the engineering experience of on-site technicians and lacks rigorous and systematic theoretical basis and technical standards. By means of orthogonal test method, the proper construction method was established for the deep-buried ultra-large-span tunnel where the tunnel excavation span, tunnel surrounding rock strength, and rock integrity coefficient were set as the main control factors. The stability of tunnel surrounding rock under various test conditions was quantified according to the plastic zone properties calculated by the three-factor and five-level orthogonal test model. Meanwhile, the macro form and quantitative method of test combinations under different levels of various factors were proposed to obtain the influence of each factor on the stability of tunnel surrounding rock, and thus the functional relations between various factors and tunnel stability were obtained. On this basis, the identification and the criterion of the ultra-large-span tunnel construction method were established, which can quantitatively reflect the contribution of excavation span of the tunnel, the number of lateral drifts in cross section, surrounding rock strength, and rock integrity coefficient to surrounding rock stability of the tunnel. The construction method calculation results of the Malin tunnel, a practical underground project, are obtained according to the orthogonal test model calculation. Based on the method, Malin tunnel can be constructed safely and efficiently. The research results could provide the theoretical basis for the identification and selection of construction method for ultra-large-span tunnel.

scholarly journals Influence of in-situ rock stress on the stability of roadway surrounding rock: a case study

2019 ◽  
Vol 17 (1) ◽  
pp. 138-147
Author(s):  
Ming Ji ◽  
Hongjun Guo
Keyword(s):  
Principal Stress ◽  
Pressure Coefficient ◽  
Surrounding Rock ◽  
Rock Stress ◽  
Principal Stresses ◽  
Design And Optimization ◽  
Coulomb Failure Criterion ◽  
The Stability ◽  
Differential Control

Abstract In-situ rock stress was measured in the development roadway of Gucheng coal mine at +420 m level by using the stress relief method of hollow inclusion. The results show that the first principal stress was the vertical stress, the maximum horizontal principal stresses were distributed in the range of N10°E and N20°E, and the average side pressure coefficient was 0.83. There was a large difference between the maximum horizontal principal stress and the minimum horizontal principal stress, and the calculated average ratio was 2.02. A spatial stress conversion model of the horizontal roadway based on the measured in-situ rock stresses was built, and the distribution laws of stress and displacement of the surrounding rock of the roadway were analyzed in depth along the changing radial direction. According to the Mohr–Coulomb failure criterion, an asymmetric surrounding rock plastic zone was obtained and the plastic failure radius was 5.0 m. Considering the roadway-surrounding rock differential control, the stronger support in the risk areas was practiced and validated. The work in this paper would provide some ideas for the design and optimization of the support parameters for roadway engineering.

scholarly journals The Researches on Construction Response and Excavation Method Optimization of Extra-large Cross-section Urban Subway Tunnel

2018 ◽  
Vol 38 ◽  
pp. 03041 ◽  
Author(s):  
Bo Wu ◽  
Wei Huang ◽  
Yong Bo Zhao
Keyword(s):  
Mechanical Behavior ◽  
Cross Section ◽  
Surrounding Rock ◽  
Large Cross Section ◽  
Subway Tunnel ◽  
Construction Methods ◽  
Method Optimization ◽  
Underground Station ◽  
The City ◽  
Selection Of

In the extra-large cross-section urban subway underground station projects, the key problem is to choose the appropriate excavation method and grasp the mechanical behavior of the surrounding rock after excavation. The double side drift method is widely used in the urban subway underground station construction with extra-large cross-section in China. This paper presents the deformation characteristics of the extra-large cross-section tunnel of urban subway and a comparison with the numerical simulation results. In the city subway underground excavation of large section station, the mechanical behavior of surrounding rock change and its influence on the surrounding area mainly depend on the selection of construction methods. The convergent deformation of tunnel cavern, the subsidence of the surface and the force failure of the surrounding rock associated the construction approaches are demonstrated. This study provides a more in-depth demonstration of the way to optimize the excavation method of the extra-large cross-section tunnel to achieve the purpose of controlling the deformation of the surface and surrounding rock.

scholarly journals Study on Sensitivity Parameters Analysis of Grouting Reinforcement Underpassing Existing Subway Tunnel by Numerical Modeling

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Zaiqiang Hu ◽  
Bin Ma ◽  
Xingzhou Chen ◽  
Lili Chen
Keyword(s):  
Pore Pressure ◽  
Principal Stress ◽  
Surrounding Rock ◽  
Surface Settlement ◽  
Stress Difference ◽  
Reinforcement Effect ◽  
Subway Tunnel ◽  
Grouting Pressure ◽  
Grouting Reinforcement ◽  
The Stability

When carrying out construction that underpasses existing subway tunnels, the surrounding rock is frequently disturbed. Therefore, it can loosen easily and become unstable, which makes its stability difficult to control. Here, we considered an existing subway tunnel in a certain subway section and used orthogonal experiments to design a simulation program as well as the UDEC (Universal Distinct Element Code) simulation software to determine the influences of four factors (i.e., grout density, grouting pressure, dynamic shear force, and viscosity) on the grouting reinforcement effect. The following results were obtained: (1) the combination of the construction method and the grouting parameters strongly influences the reinforcement effect on the surrounding rock of the tunnel. The grouting pressure is not directly proportional to the stability of the surrounding rock. The dynamic adjustment of the relationship between the grouting pressure and the grout density can effectively improve the stress state of the surrounding rock of the tunnel, control surface settlement and deformation, and reduce the section reduction rate of the tunnel. (2) The distribution of joints is closely related to the failure area and form of the surrounding rock of the tunnel. For surrounding rock with well-developed joint fissures, an excessively high grouting pressure should not be used as they are unstable. (3) The effective bearing range of grouting-reinforced surrounding rock is dependent on the pore pressure and principal stress difference. The area where the pore pressure is 70–80% of the initial grouting pressure is the effective bearing range of the grouting-reinforced surrounding rock. The stability of the surrounding rock increases with decreasing principal stress difference and increasing range. (4) The actual monitored data show that the surface settlement can be effectively reduced by handling of grouting reinforcement parameters flexibly, which can meet the control standards.

Numerical Simulation on Strengthening Supporting Mechanism and Effect of Anchor-Cables in Deep Coal Mine Roadway

2012 ◽  
Vol 170-173 ◽  
pp. 3512-3515
Author(s):  
Ju Cai Chang ◽  
Guang Xiang Xie
Keyword(s):  
Coal Mine ◽  
Surrounding Rock ◽  
Good Time ◽  
Lagrangian Analysis ◽  
Deformation And Failure ◽  
Deep Coal Mine ◽  
Geological Conditions ◽  
Stress States ◽  
The Stability ◽  
Roadway Deformation

Prestressed anchor-cables supporting technology has become the primary measure for reinforcing the roadway of deep coal mine and complex geological conditions. In this paper, fast Lagrangian analysis of continua (FLAC3D) code is used to analyze the laws of stress, deformation and failure of surrounding rock with and without roadway supporting by anchor-cables. The supporting action mechanism and effect of anchor-cables have been investigated into systematically. The results show that the anchor-cables supporting is adopted at reasonable positions of the roadway in good time which can improve the stress states of deep surrounding rock, decrease the range of failure zone around the roadway, control the roadway deformation effectively and maintain the stability of roadway.

scholarly journals Analysis of Construction Monitoring and Control of Tunnels Crossing Broken Faults and Water-rich Geology

2022 ◽  
Vol 2152 (1) ◽  
pp. 012019
Author(s):  
Jingang Fang
Keyword(s):  
Surrounding Rock ◽  
Monitoring Data ◽  
Monitoring And Control ◽  
Tunnel Engineering ◽  
Construction Monitoring ◽  
Construction Methods ◽  
The Poor ◽  
Secondary Lining ◽  
The Stability ◽  
And Control

Abstract In view of the poor geology such as tunnel engineering crossing faults or passing faults, the construction of surrounding rock and support is complicated. During construction, it is necessary to ensure the stability of the surrounding rock and supporting system, and ensure the timing of the secondary lining construction. For this reason, through the analysis and processing of monitoring data, the law of stratum change is mastered, and the supporting parameters and construction methods are adjusted and revised at the same time, so as to provide the best information for the tunnel surrounding rock and supporting lining construction.

Analysis of Monitoring and Measurement of Small Clear Spacing Tunnel in the Excavation by NATM

2012 ◽  
Vol 482-484 ◽  
pp. 581-584
Author(s):  
Dong Ming Zhang ◽  
Zi Xiong Chen ◽  
Xiao Han Qi
Keyword(s):  
Measured Data ◽  
Surrounding Rock ◽  
Tunnel Construction ◽  
Distribution Characteristics ◽  
Ground Settlement ◽  
Tunnel Excavation ◽  
Construction Scheme ◽  
Study Results ◽  
The Stability ◽  
Monitoring And Measurement

Due to its convenience, quickness, cheapness and so on, NATM is widely used in the tunnel excavation. In order to guarantee security when tunnel construction and study the stability of tunnel surrounding rock, Supervision and measurement is essential in the tunnel excavation, the result of which may influence tunnel excavation directly. Based on the analyses of measured data, the distribution characteristics and variation laws of the ground settlement, crown settlement and convergence around the tunnel, the displacement of the interior of surrounding rock are all studied. The study results are drawn to provide the basis for modifying and optimizing the design and construction scheme.

Influence exerted by underground excavation shape and by effective stresses on the formation of a tensile strain zone at a depth greater than 1 km

2020 ◽  
pp. 67-75
Author(s):  
Van Min Nguyen ◽  
V. A. Eremenko ◽  
M. A. Sukhorukova ◽  
S. S. Shermatova
Keyword(s):  
Rock Mass ◽  
Cross Sections ◽  
Tensile Strain ◽  
Rock Fracture ◽  
Strain Analysis ◽  
Surrounding Rock ◽  
Underground Excavation ◽  
Secondary Stress ◽  
Principal Stresses ◽  
Mining Depth

The article presents the studies into the secondary stress field formed in surrounding rock mass around underground excavations of different cross-sections and the variants of principal stresses at a mining depth greater than 1 km. The stress-strain analysis of surrounding rock mass around development headings was performed in Map3D environment. The obtained results of the quantitative analysis are currently used in adjustment of the model over the whole period of heading and support of operating mine openings. The estimates of the assumed parameters of excavations, as well as the calculations of micro-strains in surrounding rock mass by three scenarios are given. During heading in the test area in granite, dense fracturing and formation of tensile strain zone proceeds from the boundary of e ≥ 350me and is used to determine rough distances from the roof ( H roof) and sidewalls ( H side) of an underground excavation to the 3 boundary e = 350me (probable rock fracture zone). The modeling has determined the structure of secondary stress and strain fields in the conditions of heading operations at great depths.

scholarly journals Nonattendance at Scheduled Appointments in Outpatient Clinics Due to COVID-19 and Related Factors in Taiwan: A Health Belief Model Approach

2021 ◽  
Vol 18 (9) ◽  
pp. 4445
Author(s):  
Yi-Ping Hsieh ◽  
Cheng-Fang Yen ◽  
Chia-Fen Wu ◽  
Peng-Wei Wang
Keyword(s):  
Health Behaviors ◽  
Health Belief Model ◽  
Health Beliefs ◽  
Online Survey ◽  
Health Belief ◽  
Three Dimensions ◽  
Outpatient Clinics ◽  
Related Factors ◽  
Study Results ◽  
Belief Model

During the COVID-19 pandemic, the number of hospital visits and attendance at scheduled appointments have dropped significantly. We used the health belief model (in three dimensions) to examine the determinants of non-attendance of scheduled appointments in outpatient clinics due to the COVID-19 pandemic. Participants in Taiwan (n = 1954) completed an online survey from 10 April 10 to 23 April 2020, which assessed how people perceived and responded to the outbreak of a fast-spreading infectious disease. We performed both univariate and multivariate logistic regression to examine the roles of cognitive, affective, and behavioral health belief constructs in nonattendance at scheduled appointments. The results indicated that individuals who perceived high confidence in coping with COVID-19 were less likely to miss or cancel their doctor’s appointments, whereas individuals who reported high anxiety and practiced more preventive health behaviors, including avoiding crowded places, washing hands more often, and wearing a mask more often, were more likely to miss or cancel their appointments due to the COVID-19 pandemic. Non-heterosexual participants had a lower rate of nonattendance at scheduled appointments compared with heterosexual ones. The study results increase our understanding of the patients’ cognitive health beliefs, psychological distress, and health behaviors when assessing adherence to medical appointments during a pandemic.

scholarly journals Study on instability failure mode and monitoring early warning standard of surrounding rock in fully weathered argillaceous sandstone section of large section tunnel

2019 ◽  
Vol 136 ◽  
pp. 04023
Author(s):  
Ming Zhao ◽  
Ke Li ◽  
Hong Yan Guo ◽  
KaiCheng Hua
Keyword(s):  
Limit State ◽  
Stable State ◽  
Simulation Software ◽  
Surrounding Rock ◽  
Large Section ◽  
Rock Stability ◽  
Geological Conditions ◽  
Construction Step ◽  
The Face ◽  
The Stability

Based on the special geological conditions of a tunnel in Qingyuan section of Huizhou-Zhanzhou Expressway, FLAC3d numerical simulation software is used to simulate the rheological properties and instability of surrounding rock in large-section fully weathered sandstone section, and the stability and loss of surrounding rock are analyzed. The deformation of the dome and the face at steady state is analyzed. It is found that: 1) when the surrounding rock is in a stable state, the deformation curve of the dome is smooth. When the surrounding rock of the face is unstable, the front of the face appears ahead. Deformation should be first strengthened on the surrounding rock in front of the face. 2) The arched foot is an important part of the instability of the surrounding rock. In order to prevent the expansion of the collapsed part, the arched part should be reinforced. 3) In order to obtain the limit state of surrounding rock stability, the strength of surrounding rock is reduced, and the strength reduction coefficient corresponding to the displacement sudden point is taken as the safety factor of rock stability around the hole, and the stability safety coefficients of surrounding rock of each construction step are greater than 1.2. 4) The dynamic standard values of deformation control in the whole construction stage are obtained by analyzing the deformation curves of each data monitoring point with time in the corresponding time period of each construction step.

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