FLAC3D Numerical Simulation Research Articles

Mechanism and Control Technology of Lateral Load-Bearing Behavior of a Support System Adjacent to Empty Roadways

Currently, research on the stability of roadway-side supports in gob-side entry techniques primarily focuses on vertical stress, neglecting the lateral effects induced via roof collapse and waste rock compaction in the mined-out area. This paper systematically investigates the effect of roof rotation and the compression of waste gangue on the lateral load-bearing behavior of the roadway-side support system, combining theoretical analysis with FLAC3D numerical simulations. The results indicate that the lateral load-bearing capacity of the support system is positively correlated with both mining height and the width of the roadway-side support. When the mining height or the support width is small, the lateral load-bearing capacity of the support system is weaker, making it more prone to sliding failure. Furthermore, lateral load control technology for the roadway-side support system is proposed, which includes “roof cutting + increasing width”. When the stress transfer path of the roof is blocked, as the support system width increases from 1 m to 2 m, the lateral load-bearing capacity of the roadway-side support significantly increases and then stabilizes. This results in different extents of expansion in the elastic region within the support system, providing valuable insights for the design of roadway-side supports.

Stability analysis of the false roof made of cemented tailings backfill in deep mine: A case study

The overall stability of cemented tailings backfill (CTB) false roof, as an important support structure in the quarry, is of great significance for realizing the safe recovery of the ore body. This paper aims at the practical problem of ore body mining under the condition of deep broken rock mass. By analyzing the typical process characteristics of underhand cut-and-fill mining method, the dangerous mechanical state of CTB false roof is determined, and the CTB false roof strength model based on the maximum tensile stress failure criterion and deep mining coefficient is established. Based on the measured load value of CTB false roof, the minimum required strength of CTB false roof is obtained. Through the performance tests of CTB under different proportioning schemes, the mechanical strength of CTB false roof (UTS：0.43MPa, UCS：6.22MPa) is designed，the proportioning parameters of CTB with "high strength, high fluidity, quick setting and low cost" are put forward. Finally, based on FLAC3D numerical simulation and field monitoring, the stability of CTB false roof with recommended ratio parameters is analyzed. The results show that the CTB false roof has not been violently displaced and destabilized in the process of service ore body mining, has good strength reserve, and is able to provide a safe workspace for mining, verifies the reliability and reasonableness of the CTB false roof proportioning parameter, and provides a new way for the study of false roof stability.

Dynamic Instability Mechanism and Stress Staged Evolution of Gob‐Side Entry During Cross‐Fault Mining for Thick Coal Seam

ABSTRACTDuring cross‐fault mining, the stress concentration in the surrounding rock of thick coal seam gob‐side entry was prone to dynamic disasters. Based on the in‐site geological conditions of the No. 6305 coal face of the Xinjulong coal mine, a FLAC3D numerical simulation model was established to research the failure and stress staged evolution of coal pillar in the gob‐side entry during cross‐fault mining. By analyzing the relation of surrounding rock structure, the mechanical models of different stages during cross‐fault mining were established. Furthermore, the mechanical mechanism of coal pillars' dynamic instability under the influence of fault activation was revealed, and the mechanical criterion n was given. The control technology of ‘asymmetric strengthening support + roof cutting and pressure relief’ was proposed and designed. Field practice showed that the maximum roof‐to‐floor and two‐side displacements of the gob‐side entry are 249.3 mm and 150.4 mm, and the force of anchor cable is 184.2 kN. This research provided theoretical guidance and reference for the stability control of roadways within the influence range of fault under deep mining conditions.

Study on the mechanism and prevention system of creep induced instability of isolated coal pillars considering time effect

In response to the frequent occurrence of impact events in isolated coal pillars between the upper (lower) mountain areas of mining areas under conditions without obvious mining disturbance, this study takes multiple isolated coal pillar impact events that occurred in Zhaolou Coal Mine and Gengcun Coal Mine as examples. It conducts a mechanism study on the creep-induced impact ground pressure of isolated coal pillars considering the time effect. The occurrence of such impact ground pressure accidents often exhibits significant “lag” and “spontaneity”. Due to the unclear mechanism of occurrence and the difficulty in grasping the unloading timing, this type of impact ground pressure has become a typical hidden disaster, posing a serious threat to the deep mining of coal mines. Based on the analysis of the creep mechanical properties of coal and rock mass, the uniaxial compression acoustic emission creep test of coal body, and the FLAC3D numerical simulation, a creep instability impact mechanical model of coal and rock mass is established. This model reveals the mechanism of creep instability impact and the stress evolution law of coal and rock mass during creep. The mechanical and energy criteria for the occurrence of impact ground pressure in isolated coal pillars under the action of unstable creep are proposed. The study shows that the action of high ground stress is a necessary condition for the occurrence of "lag-type" impact ground pressure in isolated coal pillars. Long-term unstable creep will weaken the support strength of the entry. When the elastic energy accumulated in the isolated coal pillar exceeds its ultimate bearing capacity, impact instability will occur. Based on the mechanism of occurrence of such impact accidents, targeted deep hole blasting unloading measures are proposed, providing a good reference value for the prevention and control of "lag-type" impact ground pressure accidents in isolated coal pillars.

Floor Heave Mechanism and Control Technique of Water‐Rich Soft‐Rock Roadway in Thick Coal Seam

ABSTRACTThe severe deformation of the surrounding rock of the coal floor in Shanghaimiao mining area is affecting the safe, efficient production of mine wells in this region. In this study, the heave mechanism and control of the roadway floor were investigated through laboratory experiments, field research, theoretical analysis, numerical simulation, and on‐site testing. The results showed that the main reason for the serious damage to the roadway floor was the low strength of the surrounding rock of the roadway floor, and floor damage was exacerbated by the low support strength, hydraulic effects, and mining impact. A mechanical model of the asymmetric floor heave was established, and it was found that the stability of the roadway floor was positively correlated with the floor rock type, the stress concentration coefficients on the two sides of the roadway, and the burial depth, whereas it was negatively correlated with the cohesive force and internal friction angle of the floor rock mass. Expressions for the upward resultant force R of the roadway floor and the stress concentration coefficients K and K′ on both sides of the roadway were derived. The results of a FLAC3D numerical simulation analysis showed that the stress peak in front of the working face was 36 MPa, with a stress concentration factor of 3.7. After the floor support was reinforced, the floor heave was remarkably reduced, with a maximum value of approximately 600 mm, and the floor deformation became somewhat asymmetric. Finally, a double‐seal floor‐reinforcing “inverted arch” control technique was proposed and tested on‐site. The new system could efficiently and stably support the surrounding rock of the roadway.

Numerical simulation study on the force of overwintering foundation support structure of unsaturated seasonal permafrost under indoor experiments.

When analysing the effect of negative temperature on overwintering pit constructions of unsaturated soil, using the mechanical parameter of saturated soil at room temperature leads to an inaccuracy in the research findings. The strength parameters are obtained through indoor experiments. The foundation pit model is created using FLAC3D numerical simulation software based on the indoor experimental data. The influence of different parameters on the stress and deformation of the overwintering deep foundation pit supporting structure is analysed. The numerical simulation results obtained are compared with the actual monitoring data. According to research, the matric suction of the silty clay in its natural state in the Changchun area is 70 kPa. As the temperature decreases, the total cohesion of the unsaturated soil increases, and the internal friction angle tends to decrease. The numerical simulation results are consistent with the actual monitoring data changes. With the excavation, the horizontal displacement of the supporting structure increases first and then decreases, reaching the maximum displacement at two-thirds of the foundation pit. Compared with room temperature, the deformation of the supporting structure is larger under a negative temperature condition. The deformation of the supporting structure simulated by the actual temperature mechanical parameters is larger than that under the condition of normal temperature mechanical parameters. The frost-heaving force increases with the overall excavation, and a surge occurs at the bottom of the pit. The frost-heaving force changes most significantly under the condition of freezing at -20°C for 30 days.

Frequency distribution of different joint slopes containing ceramic soil under seismic wave action

The dynamic response characteristics of high and steep slopes under the action of earthquakes and blasting was focused on, especially the frequency distribution and propagation laws, which are crucial for slope stability assessment. Using stress wave theory as the theoretical basis and advanced FLAC3D numerical simulation technology, we systematically analyze the frequency response of slope under different joint conditions under seismic waves. The nonlinear characteristics of reflected P-wave coefficient and the significant sensitivity of joint to incident wave frequency are revealed when the Angle of incident P-wave changes. The results show that with the increase of the incidence Angle of the incident P-wave, the reflection coefficient of the reflected P-wave decreases slowly at first and then increases sharply to 1.0. The reflection coefficient of the wave at the joint is more sensitive to the frequency of the incident wave. In a biplanar rock mass, multiple reflections of waves between structural planes produce transmitted waves with different time differences.

Scale parameters of soft structures for surrounding rock erosion prevention in rockburst-prone roadways

Practical experience in coal mines has suggested that establishing a loose and soft structure in the surrounding rock of roadways can play a role in wave attenuation, energy absorption and erosion prevention, which is conducive to the prevention of and reduction in the severity of rockburst disasters in coal mines. The scale parameters of soft structures includes two aspects: the size and the fracture degree of soft structures. The FLAC3D numerical simulation software was used to study the failure characteristics of roadways with different impact positions (roof impact, side impact) and different impact energies (104, 105, 106, and 107 J). The stress reduction rates of soft structures with different sizes and fracture degrees were calculated. Based on the stress reduction rate of the soft structure, the energy absorption effect of the soft structure around the roadway was obtained as a logarithmic function of the soft structure size, which is a power function related to its fracture degree, and the intersection range of the two curves was fitted. The stress reduction rate was 30% when the soft structure size of the surrounding rock of the roadway was 10–15 m and the fracture degree was represented by 30–40% of the coal strength, which was the most reasonable range of scale parameters. The research conclusions provide a parametric basis for improving the theory and practice of rockburst prevention and support in coal mine roadways.

Creep deformation characteristics and control technology in deep mine soft rock roadway

In order to control the strong ageing creep and large deformation of deep soft rock roadway effectively, with the 61–71 track on the uphill of the mining area in Suzhou, Anhui as the research background, the triaxial creep test of mudstone was conducted using the TYJ-1500 M rock mechanics testing system. The creep deformation and failure characteristics of mudstone were analyzed. Additionally, the creep deformation characteristics of deep soft rock roadways were obtained through FLAC3D numerical simulation experiment, and the control techniques for deep soft rock roadway was proposed. The results showed that the axial strain and lateral strain of the specimen were mainly instantaneous strain and creep strain under triaxial stress conditions, and the both confining pressure and the axial pressure have a significant impact on the deformation and creep failure strength of the specimen. Under the condition of high ground stress and complex geological structure, the high stress concentration of roadway roof and floor and two bottom angles is the main cause of creep failure of soft rock roadway, and the large degree of surrounding rock fragmentation and unreasonable support mode reduce the bearing capacity of surrounding rock and aggravate the creep failure of roadway. The 'anchor net cable shotcrete + floor and two corners in floor bolt-grouting + deep and shallow hole grouting + secondary reinforcement support' combined support method was proposed and industrially tested, with average deformation of the roof, floor, and two sidewalls being 111.9 and 62.5 mm, respectively, representing 13.2 and 10.3% of the deformation under the original support scheme.

Seismic Response Characteristics of Complex Slope Terrain Based on FLAC3D Numerical Simulation

Seismic Response Characteristics of Complex Slope Terrain Based on FLAC3D Numerical Simulation

Characteristics of deformation and damage of surrounding rock along the top roadway in the working face of an isolated island and its evolution law

This study investigates the deformation and damage characteristics of the surrounding rock along the top return mining roadway of an isolated island working face at different stages and reveals its damage mechanism and evolution law. Utilizing a mine in Yangquan City, Shanxi Province, China, as the engineering background, this research employs FLAC 3D numerical simulation and on-site measurements. The findings suggest that the evolution of the plastic zone along the top roadway of the 15,106 island face is largely similar during both the excavation and mining periods. The plastic zones on either side of the roadway are expanding asymmetrically and gradually merging into the plastic zone of the coal pillar. In the destructive stage, the sub-gangs of the roadway are penetrated, indicating the progression into the plastic zone. The investigation points to extensive damage on the larger side of the roadway, the development of fissures, and the significant depth of damage as primary causes of roadway deformation. Moreover, the extent of the plastic zones on both sides of the roadway correlates positively with their relative distance. Continuous monitoring reveals an ongoing increase in roadway displacement, consistent with general observations in coal mining. The results provide valuable insights for optimizing support structures in similar mining environments.

Numerical Simulation Study on the Deformation Patterns of Surrounding Rock in Deeply Buried Roadways under Seepage Action

To reveal the deformation patterns of the surrounding rock in deeply buried straight-wall arch-shaped roadways under seepage action, this study, based on an FLAC3D numerical simulation and classic elastoplastic theory, investigates the influences of surrounding rock classification, roadway burial depth, pore water pressure, and roadway cross-sectional dimensions on the deformation of surrounding rock. A multivariate regression prediction model for rock deformation was established based on the numerical simulation conclusions, and the correctness of the conclusions was verified through comparative analysis. Correlation analysis of various factors with rock deformation was conducted, ranking their impact as follows: pore water pressure > roadway burial depth > surrounding rock classification > roadway height > roadway width. The research results can provide guidance for the construction and support of deeply buried roadways under seepage action.

Tunnel excavation based on FLAC3d numerical simulation

A semi-circular arch straight wall tunnel with a span of 10m, a side wall height of 5m and a buried depth of 500m is excavated in a class IV surrounding rock. Assuming that the surrounding rock is an ideal elastoplastic material, the following problems are analyzed by using finite element or finite difference method: the arch roof subsidence and the horizontal convergence of the side wall after tunnel excavation under the action of gravity stress field and the size of the plastic zone in the surrounding rock. If the lateral pressure coefficient is 0.5-3, the effects of structural stress on the subsidence of the tunnel arch, the horizontal convergence of the side wall and the plastic zone are analyzed. If the bolt support is adopted after excavation, the system bolt shall be laid on the tunnel arch and side wall. The bolt shall be a full-length metal bolt, perpendicular to the tunnel wall, with a spacing of 1.5m, a length of 3.0m, and a diameter of 25mm. The thickness of shotcrete is 100mm, the number is C20, and the supporting effect is analyzed.

Numerical Simulation Study on The Effect of Isolated Coal Pillar Width on The Subsidence Law of Deep Mining

A large number of research results show that the reasonable determination of the width of the coal pillar is an important factor affecting the stability of the surrounding rock along the roadway along the fully mechanized discharge. In this paper, the mechanism of the specific condition of isolation of coal pillars in the deep roadway of Menkeqing coal mine area on the law of surface subsidence is analyzed. The FLAC3D numerical simulation technology was used to simulate the multi-level experimental scheme to analyze the influence of different remaining coal pillar widths on the stress and strain of overburden rock and surface subsidence, and to reveal the relationship between the width of isolated coal pillars and the surface subsidence law of deep mining.

Numerical Simulation Study on The Effect of Isolated Coal Pillar Width on The Subsidence Law of Deep Mining

A large number of research results show that the reasonable determination of the width of the coal pillar is an important factor affecting the stability of the surrounding rock along the roadway along the fully mechanized discharge. In this paper, the mechanism of the specific condition of isolation of coal pillars in the deep roadway of Menkeqing coal mine area on the law of surface subsidence is analyzed. The FLAC3D numerical simulation technology was used to simulate the multi-level experimental scheme to analyze the influence of different remaining coal pillar widths on the stress and strain of overburden rock and surface subsidence, and to reveal the relationship between the width of isolated coal pillars and the surface subsidence law of deep mining.

Complex Deposit Slope Excavation Deformation Mechanism and Seismic Reinforcement Effect Evaluation

Background To further investigate the excavation deformation mechanism and remedial strategies for slope reinforcement in the southwest mountain area, the Baihetan-Jiangsu (Zhejiang) UHV transmission project deposit slope deformation reinforcement was used as a case study. Methods Deep displacement monitoring, on-site testing, and FLAC3D numerical simulation techniques were employed. The assessment of the deposit slope excavation deformation mechanism and the effectiveness of seismic reinforcement for different design options and pile parameters are conducted while analyzing the seismic reinforcement mechanism. Results and Discussions The results showed that (1) The deposit slope composed of “multi-genetic type soil” in the converter station is prone to deformation, where the dominant instability mode is “traction creep and tension failure mode.” (2) Both circular and rectangular anti-slide piles significantly reduce the amount of slope body deformation; employing circular anti-slide piles for addressing this type of deposit slope provides enhanced anti-slide retention and economic benefits. (3) Under the influence of an earthquake, the shear force and bending moment of the anti-slide pile first increase and then decrease with the increase of seismic intensity. Conclusion The distribution law of shear force and bending moment in a pile should be considered comprehensively in slope support design.

Elastic wave prospecting of water-conducting fractured zones in coal mining

In order to understand the development law of water-conducting fractures in overlying strata during the mining process of coal seam, an elastic wave exploration method based on key stratum theory is proposed to predict the height of water-conducting fracture zone. Taking Yushen mining area as the background, the development and evolution of fractures and the three-dimensional distribution characteristics of water-conducting fracture zone are studied by combining well-ground microseismic monitoring, high-density three-dimensional seismic exploration, borehole investigation, FLAC3D numerical simulation and similar physical simulation tests. The results indicate that the trial mining face's fracture-to-coal ratio ranges from 25.86 to 30.76, with the maximum fracture-to-coal ratio near the cutting eye at 30.76 and the minimum in the central portion of the trial mining face at 25.86. The primary characteristics of rock mass fracture distribution in the mined area are the development of fractures predominantly along high-angle and even vertical bedding planes. Within the fracture zone, fractures increase from top to bottom, with high-angle fractures developing in the lower section and high-angle and horizontal fractures developing simultaneously in the upper section. The water-conducting fracture zone undergoes a developmental process from inception to development, reaching its maximum height, and eventually stabilizing as coal seam mining progresses, overlying rock subsides, strata separation, and damage formation. The three-dimensional shape of the water-conducting fracture zone in the roof of the Yushen mining area exhibits a morphological pattern where the height of the fracture zone gradually decreases from the cutting eye towards the goaf. It also transitions from high to low along both sides and from the periphery towards the interior of the working face. In the trend and strike directions, it exhibits saddle-like characteristics. By comparing the monitoring results, the rationality of the elastic wave prospecting method for predicting the height of water-conducting fracture zones based on critical layer theory was verified. This research holds significant reference value for coal mining under similar geological conditions, especially in terms of water preservation during mining operations.

Optimization of inclined coal seam tunnel section angle and anchor angle based on response surface method

The mining of inclined coal seams is often accompanied by problems such as difficult to control deformation of the tunnel roof and failure of anchor bolts. Taking the transportation channel of Jinping Coal Industry 1071-1 in Shanxi Xiangkuang Mine as the background, FLAC3D numerical simulation software was used, and the method of response surface experimental design and data analysis was used to systematically study the effects of the anchor installation angle and the roof inclination angle of the tunnel section on different inclination angles. Influence of the surrounding rock stability of coal seam roadways. On this basis, a multi-index tunnel support design evaluation method based on the response surface method was proposed, and the actual support plan was optimized and industrial tests were carried out based on the actual on-site support plan. The research results show that: in terms of inclined coal seam support, the degree of influence on the tunnel stability is in the following order: anchor installation angle > tunnel section roof inclination angle > coal seam inclination angle; the optimized support design obtained through the proposed technology The method has good application effect and can improve the stability of the roadway during the mining of the working face. It also proves the effectiveness of this technology and provides new ideas for the design of anchor support of inclined coal seam roadways and the optimization of roadway sections.

Characteristics of surrounding rock damage and control technology of a facing-mining excavating roadway in north Shaanxi mining area

In a coal mine in the northern region of Shaanxi Province, China, a facing-mining excavating roadway exists, which is intended to be retained for subsequent working face safety services. This paper investigates the deformation and damage characteristics of the surrounding rock in different stages using FLAC 3D numerical simulation, taking the facing-mining excavating roadway of this coal mine as the research context. At 20 m ahead of the working face, a discontinuous plastic zone appears in the surrounding rock of the roadway, a phenomenon attributed to the varying hardness of the lithologyand termed 'plastic zone jumping.' The numerical simulation results have been were verified using drill hole peeping. Real-time monitoring of the roadway's stability is conducted on-site, showing that the roadway is significantly affected by mining at the 50 m point ahead of the working face. Based on the numerical simulation and on-site monitoring results, the support strength was increased at 50 m from the working face along the roadway, and a new support scheme was adopted. In the lagging section of the roadway, where mining pressure is strongly evident, differentiated reinforcement using anchor rods, anchor ropes, and W steel belts has been employed, resulting in a satisfactory on-site effect.

Analysis of Surrounding Rock Stability and Supporting Structure Effect Based on a Hydropower Station Underground Cavern

The surrounding rock stability is a main difficult problem in the hydropower station construction and operation. Taking one hydropower station as object, FLAC 3D numerical simulation software was used to calculate the changes in surrounding rock failure zone distribution, surrounding rock strain, and block safety factor before and after supporting. The stability of the surrounding rock after excavation was analyzed and effect of the supporting structure was also evaluated. Finding that: the supporting structure can effectively improve the stability of surrounding rock. After supporting, the failure zone range, the deformation of surrounding rock, and the internal force of the supporting structure all reduced, while the safety factor of the block improved. Due to the effect of bolt, the deformation of the surrounding rock transformed from plastic to elastic, and the rebound zone of the surrounding rock increased, while the plastic and failure zone reduced. The depth of the failure zone on the downstream side is greater than that on the upstream side, and a large number of cracking zones are distributed on the downstream side. At the same time, due to the influence of cracks and geological fracture, the failure of surrounding rock around the main powerhouse is higher than that around the tailgate chamber higher than that in the main transformer chamber. The safety factor of the key blocks distributed around the main transformer chamber and the main power house improved, the sliding form of some blocks transformed from collapse to single-surface sliding.