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.

scholarly journals An Analysis of the Impact of Deviatoric Stress and Spherical Stress on the Stability of Surrounding Rocks in Roadway

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Liu Rui ◽  
Zhu Quanjie
Keyword(s):  
Plastic Zone ◽  
Principal Stress ◽  
Tensile Deformation ◽  
Stress Component ◽  
Maximum Principal Stress ◽  
Surrounding Rock ◽  
Deviatoric Stress ◽  
Stress Difference ◽  
Deviator Stress ◽  
The Stability

In this study, a detailed analysis was conducted to evaluate the impacts of the deviatoric stress component and spherical stress component on the stability of surrounding rocks in the roadway via the theoretical analysis and calculation and numerical simulation. Based on the analysis, the distribution laws guiding the main stress differences, plastic zone, convergence of surrounding rocks, and third invariant of stress under various conditions (such as equal spherical stress and unequal deviatoric stress and equal deviatoric stress and unequal spherical stress) were developed, providing an optimization scheme for roadway support misunderstanding under the conditions of high spherical stress field and high deviator stress field. The study further reveals that under the circumstance of the constant spherical stress, the greater the deviatoric stress, the plastic zone range of the surrounding rock of the roadway, the range of tensile deformation of the surrounding rock, the amount of convergence of the surrounding rock, the probability of separation of the roof and floor of the roadway, and the principal stress difference and the main stress, the greater the concentration range of the maximum stress difference is, and the maximum principal stress difference is mainly concentrated in the roof and floor rocks of the roadway, and the greater the deviatoric stress, the greater the probability that the roof and floor rocks of the roadway will be separated, and the maximum principal stress difference is mainly concentrated in the roof and floor rocks of the roadway, the greater the deviator stress, the greater the concentration range of the maximum value of the principal stress difference and the principal stress difference; when the deviator stress is constant, the range of the plastic zone and the maximum principal stress difference concentration range of the surrounding rock of the roadway decrease with the increase of the ball stress, and the principal stress difference, the amount of convergence of the surrounding rock, and the range of tensile deformation increase with the increase of the ball stress. The maximum principal stress difference is mainly concentrated in the roof and floor rocks of the roadway. The principal stress difference increases with the increase of the spherical stress, and the maximum concentration range of the principal stress difference decreases with the increase of the spherical stress. After the method proposed in this paper optimizes the actual roadway support on site, the surrounding rock deformation of the roadway is small and the control is relatively ideal, which basically meets the engineering needs.

scholarly journals Stability Analysis and Derived Control Measures for Rock Surrounding a Roadway in a Lower Coal Seam under Concentrated Stress of a Coal Pillar

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Zhuoyue Sun ◽  
Yongzheng Wu ◽  
Zhiguo Lu ◽  
Youliang Feng ◽  
Xiaowei Chu ◽  
...  
Keyword(s):  
Coal Seam ◽  
Numerical Simulations ◽  
Principal Stress ◽  
Coal Pillar ◽  
Control Measures ◽  
Stress Difference ◽  
Coal Seams ◽  
The Stability ◽  
Close Distance ◽  
Close Distance Coal Seams

Numerical simulations have often been used in close-distance coal seam studies. However, numerical simulations can contain certain subjective and objective limitations, such as high randomness and excessively simplified models. In this study, close-distance coal seams were mechanically modeled based on the half-plane theory. An analytical solution of the floor stress distribution was derived and visualized using Mathematica software. The principal stress difference was regarded as a stability criterion for the rock surrounding the roadway. Then, the evolution laws of the floor principal stress difference under different factors that influence stability were further examined. Finally, stability control measures for the rock surrounding the roadway in the lower coal seam were proposed. The results indicated the following: (1) The principal stress difference of the floor considers the centerline of the upper coal pillar as a symmetry axis and transmits radially downward. The principal stress difference in the rock surrounding the roadway gradually decreases as the distance from the upper coal pillar increases and can be ranked in the following order: left rib > roof > right rib. (2) The minimum principal stress difference zones are located at the center of the left and right “spirals,” which are obliquely below the edge of the upper coal pillar. This is an ideal position for the lower coal seam roadway. (3) The shallowness of the roadway, a small stress concentration coefficient, high level of coal cohesion, large coal internal friction angle, and appropriate lengthening of the working face of the upper coal seam are conducive to the stability of the lower coal seam roadway. (4) Through bolt (cable) support, borehole pressure relief, and pregrouting measures, the roof-to-floor and rib-to-rib convergence of the 13313 return airway is significantly reduced, and the stability of the rock surrounding the roadway is substantially improved. This research provides a theoretical basis and field experience for stabilizing the lower coal seam roadways in close-distance coal seams.

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 Model Test on Segmental Grouting Diffusion Process in Muddy Fault of Tunnel Engineering

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Jun Liu ◽  
Qingsong Zhang ◽  
Lianzhen Zhang ◽  
Fang Peng ◽  
Zhipeng Li ◽  
...  
Keyword(s):  
Effective Stress ◽  
Pressure Field ◽  
Three Dimensional ◽  
Injection Rate ◽  
Tunnel Engineering ◽  
Reinforcement Effect ◽  
Soil Pressure ◽  
Injection Hole ◽  
Grouting Pressure ◽  
Grouting Reinforcement

In order to realize the diffusion law of segmental grouting in muddy fault of tunnel engineering, a three-dimensional grouting diffusion simulation test has been done. Three times of grouting operation have been done for three adjacent sections in grouting pipe. Grouting pressure, injection rate, soil pressure field, and seepage pressure field have been real-time monitored in three grouting stages. The effect of segmental grouting operation on soil pressure field and effective stress field has been analyzed. Results show that previous grouting operation can affect later grouting operation. Due to previous grouting operation, the grouted stratum can be compacted and grouting diffusion will conquer greater resistance in later grouting stages. Correspondingly, grouting pressure increases and injection rate decreases in the later grouting stage. There exists a limited influence range for a single grouting operation. For every grouting stage, soil pressure and effective stress in the section which the injection hole locates in are affected effectively by grouting operation. By contrast, soil pressure and effective stress in section away from injection hole are affected relatively weakly by grouting operation. With distance to injection hole increasing, compaction degree and reinforcement effect of grouted muddy fault decay in space. Multisegmental grouting method has significant advantages over single grouting method. Ineffectively compacted area by previous grouting operation can be effectively compacted by later grouting operation from adjacent injection hole. As a result, uniformity of grouting reinforcement effect can be improved, and weakly reinforcement area can be reduced.

scholarly journals Development of Modified Grouting Material and Its Application in Roadway Repair Engineering

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Yang Yu ◽  
Zhengyuan Qin ◽  
Xiangyu Wang ◽  
Lianying Zhang ◽  
Dingchao Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Surrounding Rock ◽  
Engineering Practice ◽  
Mass Ratio ◽  
Control Effect ◽  
Grouting Pressure ◽  
Grouting Material ◽  
Wide Range ◽  
Grouting Reinforcement ◽  
Grouting Materials

It is very extraordinary for the success of coal mine roadway grouting with the following factors of high early strength, good fluidity, and convenient pumping, but the existing grouting materials make it difficult to achieve the above characteristics at the same time. Therefore, a modified grouting material is developed, which is composed of two kinds of dry materials A and B, which are mixed with water and in equal amounts. The physical and mechanical properties of modified grouting materials under different ratios were tested by laboratory orthogonal test, and the optimal ratio of grouting materials and additives was obtained: (1) the water-cement ratio is 0.8 : 1; (2) base material: the mass ratio of cement, fly ash, bentonite, and water is 1 : 0.3 : 0.1 : 1.44; (3) admixture: the mass ratio of water reducer C, accelerator D, and retarder E is 1.5% : 0.05% : 0.3%. The basic properties of the modified grouting materials were studied from the aspects of slurry flow state, diffusion range, and grouting parameters by using the numerical simulation method, and the reinforcement mechanism of slurry to the broken surrounding rock properties of the roadway was revealed: (1) the grouting pressure is the main factor affecting the slurry diffusion radius; (2) the mechanical properties of the roadway surrounding rock are improved, the plastic zone and deformation of surrounding rock are reduced, and the active support function of the anchor and cable is enhanced through grouting reinforcement; (3) the control effect of the roadway is improved, and the balanced bearing with anchorage structure of the roadway surrounding rock is realized through grouting reinforcement. On this basis, the modified grouting material is applied to roadway repair and reinforcement engineering practice. The field monitoring data show that the production practices were guided by roadway repair and reinforcement technology with the modified grouting material, as the core of the roadway surrounding rock control effect is good, and the modified grouting material has a wide range of application prospects.

Analysis on Ground Settlement Induced by Shallow Buried Cross Channel of CRD Method under Artificial Filling

2013 ◽  
Vol 353-356 ◽  
pp. 1519-1524
Author(s):  
Jin Kui Li ◽  
Jing Jing Li ◽  
Liu Jie Du
Keyword(s):  
Surface Deformation ◽  
Settling Tank ◽  
Ground Surface ◽  
Surrounding Rock ◽  
Surface Settlement ◽  
Ground Settlement ◽  
Tunnel Face ◽  
Underground Tunnel ◽  
The Cross ◽  
The Stability

The shallow underground tunnel is near to the ground; its many construction procedures are complicated, supporting and excavation are intertwined. The ground surface deformation is complex during construction. Through the analysis of the cross passage surface settlement data of Dalian metro Line 1High-tech zone Street station, we found that the ground surface caused by artificial filling integrally sinks during excavation, the shape of its sinking is like a flat funnel, the characteristics of settling tank are obvious. The influence of faces constructing is obvious on surface settlement, and the transverse influence range is about 30m; the longitudinal influence range is about 15m. The results of the paper show that the place of monitoring points should be held at 15m ahead from the tunnel face, effectivemonitoring period is 70d. The monitoring results are enough and safe for the stability requirement of the surrounding rock.

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 Analysis of Influence of Stress Lode Angle on Stability of Roadway Surrounding Rock

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Yihong Liu ◽  
Hongbao Zhao ◽  
Lei Wang ◽  
Tao Wang ◽  
Dongliang Ji ◽  
...  
Keyword(s):  
Stress Field ◽  
Plastic Zone ◽  
Principal Stress ◽  
Stress Gradient ◽  
Surrounding Rock ◽  
Stress Fields ◽  
Stress Difference ◽  
Distribution Law ◽  
Lode Angle ◽  
Formula Type

Based on the variation range of the stress lode angle, the in situ rock stress is divided into σ v -type stress field, σ H -type stress field, and σ h -type stress field. Through theoretical analysis, the principal stress difference distribution law and plastic zone distribution pattern around the roadway in different types of stress fields are obtained. Theoretical and numerical simulation calculation results show that under different stress lode angle conditions, the principal stress difference distribution of the surrounding rock of the roadway is greatly different, which has a direct effect on the shape and range of the plastic zone of the surrounding rock of the roadway. In the σ v -type stress field and the σ H -type stress field, the shape of the plastic zone of the roadway surrounding rock is mainly oval and “butterfly,” while in the σ h -type stress field, the shape of the plastic zone of the roadway surrounding rock is mainly oval. The laboratory test proves that the stress gradient has an important effect on the damage degree of the surrounding rock of the roadway. The larger the stress gradient, the higher the strength of the rock mass and the more severe the damage. The change of the stress lode angle will affect the distribution law of the stress gradient of the surrounding rock of the roadway, thus affecting the degree of fragmentation of the surrounding rock. In type σ v and type σ H stress fields, the surrounding rock of the shoulder can be regarded as a key part of the roadway. In the σ h -type stress field, the plastic zones of the surrounding rocks of the roadway are more evenly distributed, and the damage range is less affected by θ. The influence law of the stress lode angle on the stability of the roadway has been well verified by field observation, and effective support measures have been proposed.

scholarly journals Comprehensive Study on Surrounding Rock Failure Characteristics of Longwall Roadway and Control Techniques

2021 ◽  
Vol 11 (21) ◽  
pp. 9795
Author(s):  
Xiaojie Yang ◽  
Gang Yang ◽  
Ruifeng Huang ◽  
Yajun Wang ◽  
Jianning Liu ◽  
...  
Keyword(s):  
Principal Stress ◽  
Theoretical Calculations ◽  
Maximum Principal Stress ◽  
Surrounding Rock ◽  
Support Design ◽  
Geological Conditions ◽  
Concentration Degree ◽  
The Stability ◽  
Roadway Deformation ◽  
And Control

Research on underground coal mines has primarily focused on the stability of roadways. Mining activities lead to significant damage to the surrounding rocks and also degrade the support to the roadways. Considering the 21309 roadway of the Huojitu coal mine as a case study, this work comprehensively analyzed the characteristics of the surrounding rock using three methods: theoretical calculations, FLAC3D numerical modeling, and field observations. The results indicate that, under the influence of secondary mining, the failure range and stress concentration degree of the surrounding rock are considerably higher than those under the influence of primary mining. In this case, the maximum damage range in the surrounding rock can reach 1.8 m, the maximum principal stress can reach 19.82 MPa, and the ratio of the maximum principal stress to the minimum principal stress can reach 1.95. According to the results, the previous support design for roadways was optimized and applied in the field. Field monitoring revealed that the roadway deformation was effectively controlled, and the optimized support design was safe and reliable. This study is expected to serve as a reference for support designs or optimization under similar geological conditions.

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