Stability Analysis of Highway Tunnel through Mined-Out Area during Excavation Process

2013 ◽  
Vol 838-841 ◽  
pp. 1352-1358 ◽  
Author(s):  
Zhi Hao Yang ◽  
Ge Cui ◽  
Ya Peng Fu ◽  
Yong Fang ◽  
Bin Yang
Keyword(s):  
Rock Mass ◽  
Plastic Zone ◽  
Axial Force ◽  
Construction Safety ◽  
Surrounding Rock ◽  
Two Dimensional ◽  
Highway Tunnel ◽  
Excavation Process ◽  
Caving Zone ◽  
Pass Through

Tianpingzhai Tunnel on Dazhou-Wanzhou Expressway passes through the mined-out area, the spatial position of the goaf changes constantly comparing to the tunnel during excavation, and broken rock mass of the caving zone is most likely to collapse, which affects construction safety in return. Two dimensional computation models were built by using finite differential software FLAC to simulate excavation process when the coal-mined area is right above or below the tunnel. In 2D models, goaf strata were regarded as horizontal, and buried depth and coal thickness were limited to 300 meters and 0.5 meter respectively. The displacement around the tunnel, forces of primary lining, axial force of bolts and plastic zone of surrounding rock have been analyzed under these circumstances that the distances between tunnel and goaf are 1m, 6m and 12m. According to the results, when the distance between goaf and tunnel is less than 12 meters,underlying goaf has greater impact on the displacement around the tunnel and average axial force of bolts than overlying goaf, as well as the size of plastic zone of surrounding rock. Its strongly suggested to avoid underlying goaf if the tunnel have to pass through the mined-out area.

scholarly journals An Improved Stress and Strain Increment Approaches for Circular Tunnel in Strain-Softening Surrounding Rock Considering Seepage Force

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Ling Wang ◽  
Jin-feng Zou ◽  
Yu-ming Sheng
Keyword(s):  
Rock Mass ◽  
Plastic Zone ◽  
Radial Displacement ◽  
Axisymmetric Problem ◽  
Strain Softening ◽  
Strain Increment ◽  
Surrounding Rock ◽  
Stress And Strain ◽  
Seepage Force ◽  
Circular Tunnel

Considering the effect of seepage force, a dimensionless approach was introduced to improve the stress and strain increment approach on the stresses and radial displacement around a circular tunnel excavated in a strain-softening generalized Hoek–Brown or Mohr–Coulomb rock mass. The circular tunnel can be simplified as axisymmetric problem, and the plastic zone was divided into a finite number of concentric rings which satisfy the equilibrium and compatibility equations. Increments of stresses and strains for each ring were obtained by solving the equilibrium and compatibility equations. Then, the stresses and displacements in softening zone can be calculated. The correctness and reliability of the proposed approach were performed by the existing solutions.

scholarly journals Research on the Reasonable Strengthening Time and Stability of Excavation Unloading Surrounding Rock of High-Stress Rock Mass

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Wensong Xu ◽  
Wentao Xu ◽  
Yunhai Cheng
Keyword(s):  
Rock Mass ◽  
Plastic Zone ◽  
Failure Process ◽  
High Stress ◽  
Stable State ◽  
Surrounding Rock ◽  
Triaxial Tests ◽  
Uniaxial Compression Test ◽  
True Triaxial ◽  
True Triaxial Tests

This study is aimed at better understanding the deformation and failure mechanism of surrounding rock during excavation unloading of a high-stress rock mass and determining the reasonable reinforcement time for the surrounding rock. To fulfill this aim, true triaxial tests were carried out on different loading and unloading paths during the unilateral unloading of a high-stress rock mass. The variational condition for minimization of plastic complementary energy is obtained, the optimal reinforcement time is determined, and the range of the plastic zone in the surrounding rock reinforced by anchor mesh-cable-grouting is compared and analyzed. The results are as follows: (1) Based on the Mohr-Coulomb yield criterion and the deformation reinforcement theory of surrounding rock, the stable state with the minimum reinforcement force is obtained. (2) After the true triaxial tests on the unilateral unloading of the third principal stress were carried out under different confining pressures, loading continued to be performed. Compared with rock failure without confining pressure, in the conventional uniaxial compression test, the failure of samples is dominated by composite splitting-shear failure; the unilateral unloading stress-concentration failure is a progressive failure process of splitting into plates followed by cutting into blocks and then the ejection of blocks and pieces. (3) The relationship between the time steps of the surrounding rock stability and the excavation distance is obtained. The supporting time can be divided into four stages: presupport stage, bolt reinforcement stage, anchor cable reinforcement stage, and grouting reinforcement stage. (4) In the range of within 5 m behind the tunneling face, the plastic zone of the surrounding rock with support is reduced by 7 m as compared with that with no support. In the range of over 5 m behind the tunneling face, the plastic zone of the roadway floor with support is reduced by 2.6 m as compared with that without support, and the deformation is reduced by 90%. These results can serve as a reference for controlling the behavior of surrounding rock during excavation unloading of high-stress rock masses.

A Study on Stability of Expressway Tunnel Surrounding Rock Containing Weak Intercalated Rock

2010 ◽  
Vol 168-170 ◽  
pp. 2543-2547
Author(s):  
Da Kun Shi ◽  
Yang Song Zhang
Keyword(s):  
Rock Mass ◽  
Plastic Zone ◽  
Surrounding Rock ◽  
Constitutive Law ◽  
Numerical Tests ◽  
Stability Of Surrounding Rock ◽  
Strain Type ◽  
Deformation Stress ◽  
Plain Strain ◽  
The Stability

Weak intercalated rock plays an important role in the stability of engineering rock mass. It controls the mechanism of deformation and breakage of rocks. Systematic numerical tests have been carried out to study the stability of surrounding rock mass with different distributions of weak intercalated rock has been analyzed by the FEM software ABAQUS. All of the numerical modelings are plain-strain type with elasto-plastic constitutive law and Drucker-Prager failure criterion. Some quantificational results about the influence of weak intercalated rock are summarized, especially the influence on the deformation, stress of surrounding rocks and plastic zone. Because of weak intercalated rock, the stress of surrounding rock appears the character of discontinuity. In addition, the distribution of plastic zone is also affected. When weak intercalated rocks exist in vault, spandrel and bottom, the situation of surrounding rock is comparatively unfavorable. These results have a certain role in guiding significance to the site selection and layout, the majorization of supporting system and the construction of tunnel of the same kind.

Numerical Analysis of Damage for Y-Shape Tunnel

2011 ◽  
Vol 368-373 ◽  
pp. 2517-2520
Author(s):  
Da Ming Lin ◽  
Yan Jun Shang ◽  
Guo He Li ◽  
Yuan Chun Sun
Keyword(s):  
Numerical Simulation ◽  
Rock Mass ◽  
Numerical Analysis ◽  
Plastic Zone ◽  
Comprehensive Analysis ◽  
Surrounding Rock ◽  
Tunnel Construction ◽  
Deformation And Failure ◽  
Single Beam ◽  
Flac 3D

There are many effective researches about tunnel at home and abroad, because the complexity of design and construction for Y-shape tunnel, in public there is no research about it yet, with the background of nanliang-tunnel which merge two single-beam into a two-lane tunnel as Y-shape. This paper obtains the rock mass mechanics parameters on the basis of nonlinear Hoek-Brown criterion first, and has a numerical simulation according the tunnel construction with FLAC-3D. we arrange many monitor sections in this model and discuss the law of deformation and failure in different section, at last have a comprehensive analysis of displacement, stress, plastic zone of different sites which caused by tunnel construction and discover that: with the distance of two single tunnels decreased, the interaction caused by the merging increase together with the compressive stress, tensile stress. The displacements of surrounding rock increase corresponding, the amplitude of variation is up to 44.8%, After the two-lane tunnel is 15m long, the stress and displacements redistribution of surrounding rock become stable.

scholarly journals A New Unified Solution for Circular Opening considering Different Strength Criteria and the Postpeak Elastic Strain Form

2020 ◽  
Vol 2020 ◽  
pp. 1-21
Author(s):  
Xuyang Shi ◽  
Wei Zhou ◽  
Liang Chen ◽  
Qingxiang Cai ◽  
Ming Li ◽  
...  
Keyword(s):  
Rock Mass ◽  
Plastic Zone ◽  
Elastic Strain ◽  
Surrounding Rock ◽  
The Self ◽  
External Boundary ◽  
Circular Opening ◽  
Strength Criteria ◽  
Criterion Equation ◽  
Zone Radius

The strength criterion is an extremely important basis for evaluating the stability of surrounding rock and optimizing the support pressure design. In this paper, nine different strength criteria are summarized and simplified based on the reasonable assumption. Then, a new unified criterion equation is established, which includes all strength theories proposed by this paper. Meanwhile, a new unified closed-form solution for circular opening based on the newly proposed unified criterion equation is deduced with the infinite and finite external boundary combining with the nonassociative flow rule under plane strain conditions. In the plastic zone, four different elastic strain assumptions are applied to solving the plastic zone deformation considering the effect of rock mass damage. The solution’s validity is also verified by comparison with the traditional solution. Finally, the influences of strength criteria, dilation coefficient, elastic strain form of plastic zone, and rock mass damage on the mechanical response of surrounding rock are discussed in detail. The research result shows that TR and VM criteria give the largest plastic zone radius, followed by IDP, MC, and MDP criteria, and seem to underestimate the self-strength of rock mass; The CDP criterion gives the smallest plastic zone radius and may overestimate the self-strength of rock mass; UST0.5, GSMP, GMC, and GLD criteria that reasonably consider the effect of internal principal stresses give an intermediate range and can be strongly recommended for evaluating the mechanics and deformation behavior of surrounding rock; as the dilation coefficient gradually increases, the dimensionless surface displacement presents the nonlinear increase characteristics; the deformation of plastic zone and the ground response curve, which are closely related to the strength criteria, are also greatly influenced by the elastic strain assumption in the plastic zone and rock mass damage degree. The assumption that the elastic strain satisfies Hook’s law (Case 3) may be more reasonable compared with the continuous elastic strain (Case 1) and thick-walled cylinders (Case 2) assumptions; in addition, the Young’s modulus power function damage model seems to give more reasonable solution for the deformation of plastic zone and is suggested to be a preferred method for solving plastic displacement. The research results can provide very important theoretical bases for evaluating the tunnel stability and support design reliability of different lithology rock masses in underground engineering.

Research on Support Technique for Excavation Process of Deep Rock Mass

2013 ◽  
Vol 438-439 ◽  
pp. 1249-1252
Author(s):  
Hong Xiao Wu ◽  
Song Lin Yue ◽  
Cun Cheng Shi ◽  
Xiao Hu ◽  
Cheng Chu ◽  
...  
Keyword(s):  
Rock Mass ◽  
High Strength ◽  
Surrounding Rock ◽  
Support Program ◽  
Tunnel Excavation ◽  
Deep Rock Mass ◽  
Rock Stability ◽  
Excavation Process ◽  
Deep Rock ◽  
Fracturing Mechanism

In the deep rock mass surrounding, rock burst, large deformation, zonal fracturing and phenomena like these may occur in the tunnel excavation process. When zonal fracturing happens, it is essential to reconsider the types of support, the boundary of support and the approach of tunnel excavation. In this paper, the control theory about the surrounding rock stability under high pre-existing stresses was researched, and the efficient support form which was the combination of high strength anchor bar and anchor cable was ascertained to be adaptive to deep tunnel excavation. According to the deformation and zonal fracturing mechanism of the surrounding rock, a comprehensive support program that combined intensive short anchor bars and long anchor cables was established, and the numerical simulation was carried out to verify the feasibility of the support form.

Analysis on Surrounding Rock Deformation of Shallowly-Buried Portal Part of Double-Line Tunnel

2011 ◽  
Vol 250-253 ◽  
pp. 1418-1421
Author(s):  
Le Min Ma ◽  
Lei Wang ◽  
Long Xian Xu
Keyword(s):  
Ground Surface ◽  
Construction Safety ◽  
Surrounding Rock ◽  
Double Line ◽  
Whole Process ◽  
Highway Tunnel ◽  
Stability Of Surrounding Rock ◽  
Ground Surface Settlement ◽  
Settlement Monitoring ◽  
Surrounding Rock Deformation

Through studying the ground surface settlement monitoring for Fang Dou Shan highway tunnel Shallowly-buried Portal Part, this paper mainly discusses the deformation of surrounding rock range from ground surface to the arch crown of double-line tunnel, and analyses the effect on stability of surrounding rock during construction, with the whole process of excavation of highway tunnel being simulated by FLAC_3D. It can make great significance for construction safety and some other related parts.

scholarly journals Evaluation of a tunnel in Yunnan using CRD construction method

2019 ◽  
Vol 136 ◽  
pp. 04020
Author(s):  
Jun Duan ◽  
Canrong Huang ◽  
Xiangyang Cui ◽  
Ke Li ◽  
Hongyan Guo
Keyword(s):  
Plastic Zone ◽  
Side Wall ◽  
Construction Safety ◽  
Construction Method ◽  
Surrounding Rock ◽  
Tunnel Construction ◽  
Monitoring Point ◽  
The Right ◽  
Tunnel Monitoring

According to the surrounding rock conditions of Re Shuitang Tunnel NO.2, it is analyzed whether the CRD method is suitable for such surrounding rock conditions. By comparing and analyzing the distribution of plastic zone of surrounding rock during construction and the displacement deformation of tunnel monitoring point, the tunnel is constructed. The plastic zone of the middle arch and the arch is obviously changed, and should be reinforced. The settlement of the right vault and the side wall is larger than the left side, which is about 19.8% and 21.9%. According to the analysis results, the vault should be reinforced in advance during tunnel construction to prevent collapse and ensure construction safety, and provide reference for future construction.

scholarly journals Displacement analysis of surrounding rock deformation of Baochang tunnel in Yunnan

2019 ◽  
Vol 136 ◽  
pp. 04018
Author(s):  
Lianghan Zhang ◽  
Xiaolong Li ◽  
Xinyun Ma ◽  
Hongyan Guo ◽  
Ke Li
Keyword(s):  
Horizontal Displacement ◽  
Construction Safety ◽  
Surrounding Rock ◽  
Tunnel Excavation ◽  
Partition Wall ◽  
Excavation Process ◽  
Tunnel Monitoring ◽  
Double Wall ◽  
Wall Method ◽  
Surrounding Rock Deformation

According to the problem of deformation of surrounding rock when the double-wall method is adopted in the tunnel, the five tunnel monitoring points are set in the tunnel vault, arch waist and arch foot to simulate the tunnel excavation process. The surrounding rock is deformed, and the excavation of the middle guide hole makes the deformation of the surrounding rock reach 7.2mm. After the removal of the middle partition wall, the deformation reaches the maximum, which is 8.4mm. The horizontal displacement starts to increase rapidly, and the maximum is 5.3mm. According to the analysis results, the surrounding rock above the tunnel should be reinforced in time, and the deformation of the surrounding rock after the removal of the middle partition wall should be paid attention to ensure the construction safety and provide reference for future construction.

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