scholarly journals Study on Supporting Protection of Tunnel Opening near a Rock Layer under Elastic Deformation of Surrounding Rock

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhigang Jia ◽  
Yongsong Li
Keyword(s):  
Side Wall ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Rock Layer ◽  
Rock Stratum ◽  
Pipe Length ◽  
Geological Conditions ◽  
Deformation Stress ◽  
Core Soil ◽  
Pass Through

Due to the limitation of geological conditions and route alignment, tunnel engineering will inevitably pass through special sections such as shallow buried section, broken rock layer, and loss and weak rock stratum. Tunnel construction in these special sections will easily lead to tunnel collapse, landslide of portal slope, excessive deformation of supporting structure, and even deformation and damage accidents, which are high-incidence areas of engineering safety accidents. In this paper, a 3D numerical model is established based on a practical engineering to analyze the deformation and stress variation of surrounding rock of the tunnel with the in-advance support technology. According to the monitoring results of the actual project, the deformation law of the soft rock section at the tunnel entrance is mastered. The deformation of surrounding rock of the tunnel under the support condition of changing the three main parameters, such as ring spacing, pipe diameter, and pipe length, is analyzed, and the effect of controlling the deformation of surrounding rock with different parameters is studied. The deformation, stress characteristics, and plastic zone distribution of surrounding rock by a single side wall guide method and ring excavation and retaining core soil method in advance support are numerically simulated and studied.

scholarly journals Analysis on Loose Circle of Surrounding Rock of Large Deformation Soft-Rock Tunnel

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Rui Wang ◽  
Yiyuan Liu ◽  
Xianghui Deng ◽  
Yu Zhang ◽  
Xiaodong Huang ◽  
...  
Keyword(s):  
Large Deformation ◽  
Theoretical Calculations ◽  
Rapid Development ◽  
Field Tests ◽  
Soft Rock ◽  
Strength Criterion ◽  
Surrounding Rock ◽  
Distribution Law ◽  
Geological Conditions ◽  
Rock Tunnel

With the rapid development of tunnel construction in China, deep buried and long tunnel projects are emerging in areas with complex engineering geological conditions and harsh environment, and thus large deformation of tunnels under conditions of high in situ stress and soft rock becomes increasingly prominent and endangers engineering safety. Therefore, it is of great significance to control the deformation and improve the stability of surrounding rock by analyzing the thickness and distribution law of loose circle according to the unique mechanical properties and failure mechanism of surrounding rock of large deformation soft-rock tunnel. Based on unified strength theory, this paper deduces the radius calculation formula of the loose circle by considering the influence of intermediate principal stress. Furthermore, the theoretical calculations and field tests of the loose circle in the typical sections of grade II and III deformation of Yuntunbao tunnel are carried out, and the thickness and distribution law of loose circle of surrounding rock of large deformation soft-rock tunnel is revealed. The results show that the formula based on the unified strength criterion is applicable for a large deformation tunnel in soft rock.

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 Research on Mechanism and Control of Floor Heave of Mining-Influenced Roadway in Top Coal Caving Working Face

Energies ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 381 ◽  
Author(s):  
Xingping Lai ◽  
Huicong Xu ◽  
Pengfei Shan ◽  
Yanlei Kang ◽  
Zeyang Wang ◽  
...  
Keyword(s):  
Coal Mine ◽  
High Efficiency ◽  
Soft Rock ◽  
Surrounding Rock ◽  
High Yield ◽  
Geological Investigation ◽  
Geological Conditions ◽  
Floor Heave ◽  
Damage Depth ◽  
Squeeze Effect

The stability of the surrounding rock is the key problem regarding the normal use of coal mine roadways, and the floor heave of roadways is one of the key factors that can restrict high-yield and high-efficiency mining. Based on the 1305 auxiliary transportation roadway geological conditions in the Dananhu No. 1 Coal Mine, Xinjiang, the mechanism of roadway floor heave was studied by field geological investigation, theoretical analysis, and numerical simulation. We think that the surrounding rock of the roadway presents asymmetrical shrinkage under the original support condition, and it is the extrusion flow type floor heave. The bottom without support and influence of mining are the important causes of floor heave. Therefore, the optimal support scheme is proposed and verified. The results show that the maximum damage depth of the roadway floor is 3.2 m, and the damage depth of the floor of roadway ribs is 3.05 m. The floor heave was decreased from 735 mm to 268 mm, and the force of the rib bolts was reduced from 309 kN to 90 kN after using the optimization supporting scheme. This scheme effectively alleviated the “squeeze” effect of the two ribs on the soft rock floor, and the surrounding rock system achieves long-term stability after optimized support. This provides scientific guidance for field safe mining.

Study on Surrounding Rock Deformation Characteristics and Control Technology in Deep Soft Rock Roadway

2012 ◽  
Vol 594-597 ◽  
pp. 631-635 ◽  
Author(s):  
Wen Hua Zha ◽  
Xin Zhu Hua
Keyword(s):  
Soft Rock ◽  
Surrounding Rock ◽  
Control Technology ◽  
Deformation Characteristics ◽  
Control Effect ◽  
Tunnel Support ◽  
Technical Problems ◽  
Geological Conditions ◽  
Soft Rock Roadway ◽  
Rock Roadway

To explore support technical problems in deep soft rock roadway, according to deep complicated geological conditions in 102 transport rise of Yuandian Mine, obtaining deformation characteristics of roadway in the initial support scheme under conditions, analysing the reasons of instability and failure of surrounding rock, proposing the surrounding rock control technology of step-by-step strengthen co-supporting, determining secondary anchor cable strengthen support time and grouting delay distance, optimizing the parameters of roadway support. Industrial practice show that the control effect of deformation was obvious,which provide the reference for deep soft rock tunnel support decision.

scholarly journals A Case Study of Optimization and Application of Soft-Rock Roadway Support in Xiaokang Coal Mine, China

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Shuai Guo ◽  
Xun-Guo Zhu ◽  
Xun Liu ◽  
Hong-Fei Duan
Keyword(s):  
Soft Rock ◽  
Surrounding Rock ◽  
Geological Conditions ◽  
Floor Heave ◽  
Roadway Support ◽  
Soft Rock Roadway ◽  
Surrounding Rock Stress ◽  
Rock Roadway

The roadway of S2S2 fully mechanized caving face (FMCF) in Xiaokang Coal Mine is one of the most typical deep-buried soft-rock roadways in China and had been repaired several times. In order to figure out the failure reasons of the original roadway support, the geological conditions were investigated, the surrounding rock stress was monitored, the rib displacement, roof separation, and floor heave were in situ measured, and the performance of the U-shaped steel support was simulated. The above analysis results indicated that the support failure was mainly caused by (1) the unreasonable arch roadway section, (2) the high and complex surrounding rock stress, (3) the failure control of the floor heave, and (4) the inadequate self-supporting capacity of the surrounding rock. For optimizing, the roadway section was changed to circle and a new full-section combined support system of “belt-cable-mesh-shotcrete and U-shaped steel-filling behind the support” was adopted, which could specifically control the floor heave, allow the roadway deformation in control, and improve the self-supporting ability and stress field of the surrounding rock. To determine the support parameters, the selected U-shaped steel support was verified by simulation, and various bolt-cable support schemes were simulated and compared. Finally, such an optimized support scheme was applied in the roadway of the next replacement FMCF. The in situ monitoring showed that the rib-to-rib convergence and roof-to-floor convergence were both controlled within 600 mm, which indicated that the roadway was effectively controlled. This case study has important reference value and guiding function for the optimal design of the soft-rock roadway support with similar geological conditions.

Application of Grouting Reinforcement Technology in Pingshan Shaft Station

2014 ◽  
Vol 580-583 ◽  
pp. 1347-1351
Author(s):  
Liang Tian ◽  
Jing Yi Xi ◽  
Jian Liu ◽  
Xiao Dong Liu ◽  
Feng Shang ◽  
...  
Keyword(s):  
Roof Rock ◽  
Soft Rock ◽  
Difficult Problem ◽  
Surrounding Rock ◽  
Ground Pressure ◽  
Geological Conditions ◽  
Floor Heave ◽  
Cable Force ◽  
Grouting Reinforcement ◽  
Roadway Support

Support of soft rock is a big challenge in all mines at home and abroad. Soft rock is of different kinds of rheological property for geological conditions, mine ground pressure and so on. It brings about really difficult problem to roadway support. In order to ensure safety application and prolong usage, shaft station need to be reinforced. Sight instrument was used to analyze broken conditions. The results show that the broken depth in roof rock is 5~6 m, and greater than 4 m in sidewalls. According to failure characters and sight results, we determine that rock of shaft station belongs to high geo-stress and jointed soft rock. On this basis, technology of grouting reinforcement combined with cable anchor support is carried out. Monitoring results of surface convergence and cable force show that bearing capacity of surrounding rock increases obviously, roadway contraction and floor heave are well controlled.

The Integrated Control Countermeasures on Floor Heave of Broken Soft Rock with High Ground Stress

2014 ◽  
Vol 875-877 ◽  
pp. 2259-2263 ◽  
Author(s):  
Yao Bin Li
Keyword(s):  
Integrated Control ◽  
Soft Rock ◽  
Mining Area ◽  
Stability Control ◽  
Surrounding Rock ◽  
Deep Well ◽  
Rock Stability ◽  
Geological Conditions ◽  
Floor Heave ◽  
Key Issues

The floor heave is one of the key issues of surrounding rock stability control during the deep well mining process. To solve the problem about floor heave occupying the most of roof and floor convergence deformation, the author analyzed the engineering geological conditions of broken surrounding rock and the floor heave features in PanEr Coal Mine East 2 mining area when it through the fault zone with high pressure. It pointed out that we should make full use of the reinforcement of the roof and laneway's side to limit the deformation of the floor, and make use of overbreak, prestressed anchor cable, bottom corner bolt, deep hole grouting and backfill as direct bottom control countermeasures.

scholarly journals Application of Modified Hoek–Brown Strength Criterion in Water-Rich Soft Rock Tunnel

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xianghui Deng ◽  
Yuncai Wang ◽  
Rui Wang ◽  
Daohong Xia ◽  
Zhiqing Zhao
Keyword(s):  
Soft Rock ◽  
Strength Criterion ◽  
Surrounding Rock ◽  
Calculation Formula ◽  
Rock Stratum ◽  
Rock Stability ◽  
Deformation Limit ◽  
Disturbance Factor ◽  
The Stability ◽  
Rock Tunnel

When a tunnel is excavated in the water-rich soft rock stratum, the strength of the soft rock is greatly reduced due to the seepage of groundwater. The condition may result in engineering accidents, such as large deformation, limit invasion, and even local collapse of the tunnel. Therefore, it is very important to research the stability of the surrounding rock in the water-rich soft rock tunnel. The water-rich disturbance factor considering the seepage influence of groundwater and blasting disturbance is proposed, and the generalized Hoek–Brown strength criterion is modified on the basis of the immersion softening test of soft rock. In accordance with the classical elastic–plastic mechanics theory, the stress, strain, and displacement calculation formulas of the tunnel surrounding rock are derived. The displacement of tunnel surrounding rock is analyzed using the derived formula and the modified Hoek–Brown strength criterion and then compared with the measured value. Results show that the displacement of surrounding rock, which is calculated by modified Hoek–Brown strength criterion considering water-rich disturbance factor and the displacement calculation formula, is close to the measured deformation of surrounding rock in water-rich soft rock tunnel, and the error is small. Therefore, the modified Hoek–Brown strength criterion can be applied to the water-rich soft rock tunnel, and the derived displacement calculation formula can accurately calculate the deformation of tunnel surrounding rock. It is of great significance to the study of surrounding rock stability of water-rich soft rock tunnel.

scholarly journals The effect of contact grouting on support load

2021 ◽  
Vol 6 ◽  
pp. 5-12
Author(s):  
Liskovets Aleksandr ◽  
Tatsienko Viktor ◽  
Gogolin Viacheslav
Keyword(s):  
Rock Mass ◽  
Layer Thickness ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Cement Grout ◽  
Hardened Cement ◽  
Support Design ◽  
Tight Contact ◽  
Geological Conditions ◽  
Arch Support

Introduction. The paper analyzes contemporary methods of frame support design in permanent workings and reveals that contact grouting has received little attention. Contact grouting makes the tight contact between the hardened cement grout and the surrounding rock possible, whereas it is impossible when applying concrete lagging. The paper employs analytical method of arch support, grouting layer, and the surrounding rock calculation considering their softening. Analytical formulae determining support load has been obtained. The formulae take into account strain and strength characteristics of the surrounding rock, hardened cement grout, and support. Support load was calculated under various values of the grouting layer thickness and linear strain modulus and the depth of mining. The dependencies between the support load and the indicated parameters have been obtained, which makes it possible to select the cement grout composition for various mining and geological conditions. Research objective is to determine the effect produced by grouting layer thickness and strain characteristics on arch support load value in order to check its strength in various mining and geological conditions. Methods of research are built upon the physically based analytical methods of geomechanics to solve the problem of interaction between the support, grouting layer, and surrounding rock mass. Results. The results of arched support load calculation are presented for various values of grouting layer thickness, its strain characteristics, and depth of mining. Conclusions. The presence of the grouting layer in the void behind the support has a significant effect on the methods of arch support design. The developed methods take account of the fact that a layer of soft rock develops in the rock mass between the grouting layer and undisturbed rock. When the rock is being broken, its volume in this layer increases, which, in its turn, results in support load transfer growth through the grouting layer. It has been determined that the increase in the hardened cement grout strain and grouting layer thickness reduces support load.

scholarly journals Fracturing of the Soft Rock Surrounding a Roadway Subjected to Mining at Kouzidong Coal Mine

2020 ◽  
Vol 2020 ◽  
pp. 1-17 ◽  
Author(s):  
Zhili Su ◽  
Wenbing Xie ◽  
Shengguo Jing ◽  
Xingkai Wang ◽  
Qingteng Tang
Keyword(s):  
Failure Mechanism ◽  
Coal Mine ◽  
Shear Failure ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Asymmetric Distribution ◽  
Rock Layer ◽  
Imaging Results ◽  
Fracture Development ◽  
Borehole Imaging

The fracture development and distribution around the deep soft rock roadway are pivotal to any underground design. In this paper, both field investigation and numerical simulation were taken to study the fracture evolution and rock deformation of a coal mine roadway at Kouzidong mine, Fuyang, Anhui Province, China. Based on the borehole imaging technique, we found an asymmetric distribution of the fracture zone in the surrounding rock of the roadway. By analyzing the C value of the fractures in the borehole images,we found that the fracture interval distribution of the surrounding rock of the tunnel, the number of fractures will fluctuate decrease with the increase of the depth. To effectively study the fracture propagation and distribution of the roadway under longwall retreatment and roadway excavation, the global-local numerical technique was applied via FLAC3D and PFC2D. In the roadway excavation process, fractures were first formed in the shallow section of the roadway and progressively propagated toward the deeper soft rock layer; the main failure mechanism was a tensile failure. During longwall retreatment, fractures continuously developed toward the deeper soft rock layer. However, the failure mechanism transformed to shear failure. From numerical results, it can be seen that the stress concentration at the ribs was released, which led to shear failure at the roof and floor. Due to the extensive tensile cracks in the shallow section, the surrounding rock experienced expansion and fracture. The deep shear failure also induced the formation of the nonadjacent crushing zone and elastic zone, which is in line with the borehole imaging results.

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