scholarly journals Stability Analysis and Protection Measures of Large Section Tunnel in Coal Rich Weak Rock Stratum

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Guannan Zhou ◽  
Zijiang Zhao ◽  
Zhanping Song ◽  
Hongjian Wang
Keyword(s):  
Coal Seam ◽  
Large Scale ◽  
Economic Benefits ◽  
Surrounding Rock ◽  
Tunnel Construction ◽  
Weak Rock ◽  
Large Section ◽  
Tunnel Face ◽  
Finite Element Software ◽  
Geological Conditions

Due to poor engineering geological conditions of Liujiazhuang tunnel on Shanghai-Kunming Passenger Dedicated Line, the large deformation of weak rock occurs repeatedly during tunnel construction. In this paper, the large-scale finite element software ABAQUS is used to simulate the construction process of a large-section tunnel in weak surrounding rock. It is found that when tunnel face passes through the coal seam, the displacement and stress simulated by the bench method increase abruptly. The maximum stress reaches up to 18 MPa, and displacement reaches 45 mm, which is about twice when without crossing coal seam. It is technically feasible to use the bench method for tunnel construction, under the condition when large settlements is allowed; additionally, the bench method has better technical and economic benefits than that of the CD method. Through the comparative analysis of onsite monitoring data and numerical simulation results, it can be seen that the tunnel is in a dangerous state when passing through the coal seam and measures such as strengthening support or auxiliary advance support should be taken immediately to control the surrounding rock and to ensure tunnel construction safety.

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.

Reasonable Entry Layout of Lower Seam in Multi-Seam Mining Based on Numerical Simulation

2013 ◽  
Vol 295-298 ◽  
pp. 2980-2984
Author(s):  
Xiang Qian Wang ◽  
Da Fa Yin ◽  
Zhao Ning Gao ◽  
Qi Feng Zhao
Keyword(s):  
Numerical Simulation ◽  
Stress Distribution ◽  
Coal Seam ◽  
Coal Mine ◽  
Abutment Pressure ◽  
Surrounding Rock ◽  
Geological Conditions ◽  
Seam Mining

Based on the geological conditions of 6# coal seam and 8# coal seam in Xieqiao Coal Mine, to determine reasonable entry layout of lower seam in multi-seam mining, alternate internal entry layout, alternate exterior entry layout and overlapping entry layout were put forward and simulated by FLAC3D. Then stress distribution and displacement characteristics of surrounding rock were analyzed in the three ways of entry layout, leading to the conclusion that alternate internal entry layout is a better choice for multi-seam mining, for which makes the entry located in stress reduce zone and reduces the influence of abutment pressure of upper coal seam mining to a certain extent,. And the mining practice of Xieqiao Coal Mine tested the results, which will offer a beneficial reference for entry layout with similar geological conditions in multi-seam mining.

scholarly journals Key Parameters of Roof Cutting of Gob-Side Entry Retaining in a Deep Inclined Thick Coal Seam with Hard Roof

Energies ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 934 ◽  
Author(s):  
Jinzhu Hu ◽  
Manchao He ◽  
Jiong Wang ◽  
Zimin Ma ◽  
Yajun Wang ◽  
...  
Keyword(s):  
Numerical Model ◽  
Coal Seam ◽  
Economic Benefits ◽  
Surrounding Rock ◽  
Thick Coal Seam ◽  
Hard Roof ◽  
Coal Recovery ◽  
Rock Structure ◽  
Different Depths ◽  
Dip Angle

Gob-side entry retaining by roof cutting (GERRC) employed in a deep inclined thick coal seam (DITCS) can not only increase economic benefits and coal recovery, but also optimize surrounding rock structure. In accordance with the principles of GERRC, the technology of GERRC in DITCS is introduced and a roof-cutting mechanical model of GERRC is proposed to determine the key parameters of the depth and angle of RC. The results show that the greater the RC angle, the easier the caving of the goaf roof, but the length of cantilever beam increases. The depth of RC should account for the dip angle of the coal seam when the angle is above 20°. Increasing the coal seam dip angle could reduce the volume of rock falling of the goaf roof, but increase the filling height of the upper gangue to slide down. According to numerical model analysis of the stress and displacement of surrounding rock at different depths and angles of RC, when the depth of RC increased from 9 m to 13 m, the distance between the stress concentration zone and the coal side is increased. When the angle of RC increased from 0° to 20°, the value of roof separation is decreased. GERRC was applied in a DITCS with 11 m depth and 20° RC angle, and the field-measured data verified the conclusions of the numerical model.

Analysis on the Mechanical Behavior of Pipe Roof and Rock Bolt of Shallow and Unsymmetrical Tunnel in Soft Rock

2012 ◽  
Vol 443-444 ◽  
pp. 267-271
Author(s):  
Xu Dong Cheng ◽  
Peng Ju Qin
Keyword(s):  
Soft Rock ◽  
Surrounding Rock ◽  
Mechanical Behaviors ◽  
Maximum Displacement ◽  
Tunnel Excavation ◽  
Finite Element Software ◽  
Highway Tunnel ◽  
Geological Conditions ◽  
The Impact ◽  
Rock Strata

In this paper, the mechanical behaviors of pipe roof and bolt of shallow and unsymmetrical tunnel in soft rock are analyzed. Through the finite element software Phase2.0, combined with the geological conditions that construction site often appear, the mechanical behaviors of pipe roof and bolt and surrounding rock in the process of horseshoe highway tunnel construction in the condition that surface is soft rock and underground for the bedrock are analyzed. Research results show that: after tunnel excavation in soft rock, surrounding rock near the tunnel is easy to suffer soft-rock large deformation even failure, which needs to timely support；Due to the impact of the unsymmetrical tunnel, the mechanical behaviors of surrounding rock are unsymmetrical, such as the maximum displacement of tunnel around 0.4 m distant from apex of arch ring, the stress is asymmetrical on both sides of the tunnel arch ring etc; In addition, pipe roof can effectively prevent from the displacement of soft rock strata, improve tunnel strength factor, reduce the plastic zone of surrounding rock. This paper provides theoretical basis for the design of pipe roof and bolt.

scholarly journals Key Factors Affecting the Deformation and Failure of Surrounding Rock Masses in Large-Scale Underground Powerhouses

2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Meng Wang ◽  
Jia-wen Zhou ◽  
An-chi Shi ◽  
Jin-qi Han ◽  
Hai-bo Li
Keyword(s):  
Rock Mass ◽  
Large Scale ◽  
Surrounding Rock ◽  
Rock Masses ◽  
Affecting Factors ◽  
Key Factors ◽  
Underground Powerhouse ◽  
Deformation And Failure ◽  
Factors Affecting ◽  
Geological Conditions

The stability of the surrounding rock masses of underground powerhouses is always emphasized during the construction period. With the general trends toward large-scale, complex geological conditions and the rapid construction progress of underground powerhouses, deformation and failure issues of the surrounding rock mass can emerge, putting the safety of construction and operation in jeopardy and causing enormous economic loss. To solve these problems, an understanding of the origins and key affecting factors is required. Based on domestic large-scale underground powerhouse cases in the past two decades, key factors affecting the deformation and failure of the surrounding rock mass are summarized in this paper. Among these factors, the two most fundamental factors are the rock mass properties and in situ stress, which impart tremendous impacts on surrounding rock mass stability in a number of cases. Excavation is a prerequisite of surrounding rock mass failure and support that is classified as part of the construction process and plays a pivotal role in preventing and arresting deformation and failure. Additionally, the layout and structure of the powerhouse are consequential. The interrelation and interaction of these factors are discussed at the end of this paper. The results can hopefully advance the understanding of the deformation and failure of surrounding rock masses and provide a reference for design and construction with respect to hydroelectric underground powerhouses.

Research on Mining Technological Parameters of 7# Thin Coal Seam in Liuquan Mine

2012 ◽  
Vol 629 ◽  
pp. 937-942
Author(s):  
Dong Sheng Zhang ◽  
Xu Feng Wang ◽  
Yang Zhang ◽  
Jin Liang Wang
Keyword(s):  
Coal Seam ◽  
Distinct Element ◽  
Horizontal Displacement ◽  
Simulation Software ◽  
Surrounding Rock ◽  
Technological Parameters ◽  
Thin Coal Seam ◽  
Geological Conditions ◽  
Universal Distinct Element Code ◽  
Distinct Element Code

Aimed at the specific geological conditions of 7# thin coal seam in Liuquan Mine, this paper used the methods of numerical calculation and theoretical analysis to determine the reasonable technological parameters of high-grade conventional mining face. The numerical simulation software of UDEC (Universal Distinct Element Code) was used to contrast and analyse the characteristics of surrounding rock stress distribution and overlying rock horizontal displacement under the condition of different length of coalface, then it was indicated that the surrounding rock deformation was less when length of coalface was 110 m which was advantageous for roof control; according to the conditions of roof and floor, the roof support strength was being calculated systematically to determine the row space of props being 700×1200 mm; the main equipments of coalface was assorted, and reasonable work manner in coalface and gob processing measure was put forward, which provided guidance for efficient mining in thin coal seam.

Imaging the Geology Ahead of a Tunnel Using Seismics and Adaptive Polarization Analysis

2020 ◽  
Vol 25 (2) ◽  
pp. 189-198
Author(s):  
Lei Chen ◽  
Chao Fu ◽  
Xinji Xu ◽  
Lichao Nie
Keyword(s):  
Time Window ◽  
Geophysical Methods ◽  
Weighting Coefficient ◽  
Tunnel Construction ◽  
Polarization Analysis ◽  
Polarization Direction ◽  
Tunnel Face ◽  
Seismic Method ◽  
Imaging Results ◽  
Geological Conditions

The seismic method is one of the main geophysical methods that are widely used to image the geology ahead of tunnels during tunnel construction. However, owing to the complex environment and limited observation aperture in a tunnel, symmetric false results (that appear in imaging results but not in the actual environment) frequently occur in imaging results. In a symmetric false reflection, false and true reflection points are axisymmetric around the tunnel axis. Such false results frequently cause errors in the interpretation of the geological conditions ahead of a tunnel face. To overcome this problem, a seismic method that uses adaptive polarization analysis was adopted to better image geological conditions. Based on an adaptive time window, the polarization characteristics of seismic signals were analyzed to calculate the main polarization direction. The symmetric false results in imaging results were suppressed by adopting a weighting coefficient based on the angle between the main polarization direction and ray direction. Numerical simulations revealed the superiority of the method when applied to synthetic data processing. Moreover, the method was applied to a diversion tunnel. The method successfully identified the fracture zones ahead of the tunnel face, thus significantly enhancing the safety of tunnel construction.

scholarly journals Stability Analysis of Shallow and Bias Loess Tunnel Based on Finite Difference Method

2019 ◽  
Vol 131 ◽  
pp. 01027
Author(s):  
Li Yongbing ◽  
Binglei Li ◽  
Guanyu Hua ◽  
Xinran Jia ◽  
Yanqiao Chen ◽  
...  
Keyword(s):  
Finite Difference ◽  
Shear Failure ◽  
Surrounding Rock ◽  
Tunnel Construction ◽  
Failure Zone ◽  
Tunnel Face ◽  
Whole Process ◽  
The Earth ◽  
Practical Engineering ◽  
The Stability

Based on the Mohr-Coulomb elastic-plastic model and the practical engineering background of Mopanshan tunnel, this paper applies the finite-difference software FLAC3D to simulate and analyse the whole process of loess tunnel construction. Then, it analyses the stability of the surrounding rock and sup-port structure after partial excavation of the loess tunnel under the shallow burying and unsymmetrical load-ing condition. The study showed that in the absence of support, the shear failure occurred to the top/upper pilot tunnel of the tunnel face, the failure zone under tensile stress happened to the shallow soil of the earth surface, and the soil of tunnel face appeared to be damaged. Finally, according to the analysis results, a rea-sonable construction method suitable for the shallow and bias loess tunnel is determined.

scholarly journals Occurrence Mechanism of Roof-Fall Accidents in Large-Section Coal Seam Roadways and Related Support Design for Bayangaole Coal Mine, China

2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Shitan Gu ◽  
Bangyou Jiang ◽  
Gensheng Wang ◽  
Huabin Dai ◽  
Mingpeng Zhang
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Large Scale ◽  
Control Method ◽  
Tensile Failure ◽  
Large Section ◽  
Support Design ◽  
Roof Fall ◽  
Occurrence Mechanism ◽  
Fall Accidents

This study focused on large-scale roof-fall accidents occurred in large-section coal seam roadways of Bayangaole Coal Mine, Inner Mongolia, China, and investigated the occurrence mechanism of roof-fall and the related supporting control method in detail. Firstly, the fracture characteristics of the surrounding rocks on the roadway roof were measured using a stratum detector. The results showed that the roadway roof underwent the most severe failure with a maximum deformation of 3.53 m; the bedding separation and fracture zones were distributed at irregular intervals. Accordingly, the entire stratum was separated into several thin sublayers, significantly reducing the stability of roof. In addition, the roof medium grained sandstone of roadway is water-rich strata, and water aggravates the damage of roof. Next, the mechanism of the occurrence of roof-fall accidents in the roadway was elucidated in detail. The following three reasons are mainly attributed to the occurrence of roof-fall accidents: (i) effects of mining-induced stress and tectonic stress, (ii) existence of equipment cavern on the side of roadway, and (iii) unreasonable support parameters. On that basis, a new supporting design is proposed, including a more reasonable arrangement of anchor cables and bolts, bolts with full-length anchorage which are applicable in cracked and water-rich roadway, high-strength anchor cables, and crisscrossed steel bands. Moreover, high pretightening force was applied. Finally, a field test was performed, and the mining-induced roof displacement and stress on anchor cable (bolt) were monitored in the test section. The maximum roof displacements at the two monitoring sections were 143 mm and 204 mm, respectively, far smaller than the roadway’s allowable deformation. Moreover, the stress on roof anchor cables (bolts) was normal, and no anchorage-dragging and tensile failure phenomena were observed. The monitoring data indicated that the new supporting design was remarkable on the control of large-section coal seam roadway roof deformation.

scholarly journals Instability Control of Roadway Surrounding Rock in Close-Distance Coal Seam Groups under Repeated Mining

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5193
Author(s):  
Yu Xiong ◽  
Dezhong Kong ◽  
Zhanbo Cheng ◽  
Zhijie Wen ◽  
Zhenqian Ma ◽  
...  
Keyword(s):  
Coal Seam ◽  
Principal Stress ◽  
Large Scale ◽  
Field Testing ◽  
Horizontal Stress ◽  
Maximum Principal Stress ◽  
Stability Control ◽  
Surrounding Rock ◽  
Roadway Stability ◽  
Close Distance

In order to solve the problems of roadway stability and easy instability under repeated mining of close-distance coal seam groups, the mechanism and control technology of surrounding rock instability under repeated mining were studied via indoor testing, field testing, physical similarity simulation experiment, and numerical simulation. The results show that the surrounding rock of roadway has low strength, low bearing capacity, and poor self-stabilization ability, and it is vulnerable to engineering disturbances and fragmentation. Affected by the disturbance under repeated mining, the roadway surrounding rock cracks are developed and the sensitivity is strong, and it is prone to large-scale loose and destroyed. The location of the roadway is unreasonable, and the maximum principal stress of the roadway is 3.1 times of the minimum principal stress, which is quite different. Thus, under a large horizontal stress, the surrounding rock undergoes long-range expansion deformation. On the basis of this research, the direction and emphasis of stability control of roadway surrounding rock under repeated mining of coal seam groups in close-distance are shown. A repair scheme (i.e., long bolt + high-strength anchor cable + U-shaped steel + grouting) is proposed, and reduces the risk of roadway instability.

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