Roof pre-fracture poses a considerable risk during the re-mining of residual coal above abandoned roadways,threatening the safety of the mining faces.This study employs a Winkler foundation beam model for mechanical a...Roof pre-fracture poses a considerable risk during the re-mining of residual coal above abandoned roadways,threatening the safety of the mining faces.This study employs a Winkler foundation beam model for mechanical analysis of roof structures and adopts a multivariate nonlinear analysis approach to explore the synergistic load-bearing effects within the'coal pillar-support-backfill body'system during the fill and re-mining processes above these roadways.The findings demonstrate that backfill mining significantly reduces stress concentrations in coal pillars and reduces excessive bending moments in roofs near abandoned roadways.The roof deflection equation incorporates three critical factors affecting stability during backfill mining:the width of the coal pillar(L_(3)),the working resistance of the support(q_(z)),and the elastic foundation coefficient of the backfill material(kcÞ.Under single-factor conditions,the impact sequence on roof stability in the coal pillar zone is·k_(c)>L_(3)>q_(z).Further,multivariate nonlinear analysis reveals the interactions within the'coal-support-backfill'structure,indicating that in terms of roof control,the interaction terms are ordered as L_(3)·k_(c)>q_(z)·k_(c)>L_(3)q_(z).Therefore,priority should be given to adjusting the coal pillar width and backfill strength,followed by modifications to the support resistance and backfill strength during the recovery of abandoned roadways.An improved understanding of these interactions will help optimize strategies for the recovery of residual coal through abandoned roadways,thereby enhancing the stability and safety of mining operations under complex geological conditions.展开更多
Rockbursts, which mainly affect mining roadways, are dynamic disasters arising from the surrounding rock under high stress. Understanding the interaction between supports and the surrounding rock is necessary for effe...Rockbursts, which mainly affect mining roadways, are dynamic disasters arising from the surrounding rock under high stress. Understanding the interaction between supports and the surrounding rock is necessary for effective rockburst control. In this study, the squeezing behavior of the surrounding rock is analyzed in rockburst roadways, and a mechanical model of rockbursts is established considering the dynamic support stress, thus deriving formulas and providing characteristic curves for describing the interaction between the support and surrounding rock. Design principles and parameters of supports for rockburst control are proposed. The results show that only when the geostress magnitude exceeds a critical value can it drive the formation of rockburst conditions. The main factors influencing the convergence response and rockburst occurrence around roadways are geostress, rock brittleness, uniaxial compressive strength, and roadway excavation size. Roadway support devices can play a role in controlling rockburst by suppressing the squeezing evolution of the surrounding rock towards instability points of rockburst. Further, the higher the strength and the longer the impact stroke of support devices with constant resistance, the more easily multiple balance points can be formed with the surrounding rock to control rockburst occurrence. Supports with long impact stroke allow adaptation to varying geostress levels around the roadway, aiding in rockburst control. The results offer a quantitative method for designing support systems for rockburst-prone roadways. The design criterion of supports is determined by the intersection between the convergence curve of the surrounding rock and the squeezing deformation curve of the support devices.展开更多
As coal mining depth increases,the combined effects of high stress,mining stress,and fault structures make dynamic impact hazards more frequent.The reproduction of dynamic impact phenomena is basis for studying their ...As coal mining depth increases,the combined effects of high stress,mining stress,and fault structures make dynamic impact hazards more frequent.The reproduction of dynamic impact phenomena is basis for studying their occurrence patterns and control mechanisms.Physical simulation test represents an efficacious methodology.However,there is currently a lack of simulation devices that can effectively simulate two types of dynamic impact phenomena,including high stress and fault slip dynamic impact.To solve aforementioned issues,the physical simulation test system for dynamic impact in deep roadways developed by authors is employed to carry out comparative tests of high stress and fault slip dynamic impact.The phenomena of high stress and fault slip dynamic impact are reproduced successfully.A comparative analysis is conducted on dynamic phenomena,stress evolution,roadway deformation,and support force.The high stress dynamic impact roadway instability mode,which is characterized by the release of high energy accompanied by symmetric damage,and the fault slip dynamic impact roadway instability mode,which is characterized by the propagation of unilateral stress waves accompanied by asymmetric damage,are clarified.On the basis,the differentiated control concepts for different types of dynamic impact in deep roadways are proposed.展开更多
Filling the roadways of the abandoned mines can enhance the structural stability of surrounding ore bodies.However,existing studies on backfill reinforcement for different roadway shapes focus on mechanical properties...Filling the roadways of the abandoned mines can enhance the structural stability of surrounding ore bodies.However,existing studies on backfill reinforcement for different roadway shapes focus on mechanical properties and failure modes,with less emphasis on the specific mechanisms governed by crack-type evolution during the failure process.This study investigates the mechanical effects of three backfill conditions(unfilled,soft-filled,and hard-filled)on six common roadway geometries with scaled specimens subjected to uniaxial compression tests.Crack initiation and propagation were monitored with digital image correlation(DIC).Results show:(1)Roadway geometry strongly affects strength and fracture behavior.With identical effective apertures,the horseshoe-shaped specimen reaches a maximum strength of 23.5 MPa,compared to 16.7 MPa for the square specimen.Sharp-cornered geometries exhibit pronounced stress concentrations,leading to early cracking and faster failure.(2)Fillings improve strength and mitigate damage.Hard fillings(≈1/6 of the specimen strength)control cracks more effectively than soft ones(≈1/3 strength).For circular specimens,the crack initiation stress increases by 99.7%and 105.6%after filling with soft and hard filler,respectively,relative to the unfilled case(9.25 MPa),representing the greatest enhancement among all geometries.(3)DIC analysis identifies tensile,shear,and mixed-mode cracks.Unfilled specimens frequently shift between modes,whereas filled ones show more stable patterns with delayed crack initiation.(4)Energy analysis reveals higher peak dissipation in unfilled specimens.Filling improves energy dissipation performance across all roadway shapes,with both fillers showing the most significant suppression effect in triangular specimens—by 63.0%and 58.3%for soft and hard fillers,respectively—and the least effect in arched-wall specimens—12.9%and 17.6%,respectively.These results contribute to understanding the damaging effects caused by the dynamic evolution of crack types in backfilled roadways and surrounding mine bodies in underground rock engineering.展开更多
Cross roadway collapses are a common occurrence in underground mining operations.While the influence of mining blasts on the stability of surrounding rock is acknowledged,the underlying mechanisms remain inadequately ...Cross roadway collapses are a common occurrence in underground mining operations.While the influence of mining blasts on the stability of surrounding rock is acknowledged,the underlying mechanisms remain inadequately understood.This study investigates the characteristics and mechanisms of collapse in a shallow buried cross roadway subjected to mining blast disturbances,drawing insights from an engineering project in Anshan City,Northeast China.A strain-softening model based on unified strength theory was developed to effectively calculate and analyze the loosened zone thickness and surrounding rock displacement.The PFC3D-FLAC3D coupling method was employed to clarify the concentrated collapse area within the cross roadway,providing insight into the collapse mechanism through a cross-sectional model of the concentrated region.Results demonstrate that 50%of the cross roadway collapsed following the mining blast.Subsidence at the intersection was approximately one-fifth(0.66 m)of cross roadway’s net height,exceeding subsidence in other areas by 1.3.Under the action of repeated mining blasting,the cross section of the connection roadway forms a semi-elliptical high tensile stress zone.After the cumulative damage of the surrounding rock of the connection roadway exceeds the ultimate yield strength,the cumulative stress release causes the tensile failure of the surrounding rock.The plastic zone of the connecting roadway expands to three times of the initial,and continues to develop.The surrounding rock on both sides experienced tensile stress,cumulative stress release,and the vertical propagation of tensile cracks.展开更多
In extremely close-distance coal seam(ECDCS)mining,section coal pillars remain after upper coal seam(UCS)extraction.Thus,for layout and support design of lower coal seam(LCS)mining roadways,it is critical to account f...In extremely close-distance coal seam(ECDCS)mining,section coal pillars remain after upper coal seam(UCS)extraction.Thus,for layout and support design of lower coal seam(LCS)mining roadways,it is critical to account for UCS goaf deterioration and residual coal pillar(RCP)-induced stress disturbance.Taking the 6.4 m layer spacing of ECDCS mining in Nanyangpo Coal Mine as a case study,this research aimed to determine the optimal layout and surrounding rock control method for the 24202-ventilation roadway in the RCP area.First,the challenges of roadway layout and support under RCP were clarified:three layout methods face distinct RCPinduced stress disturbances and goaf-related roof damage.A finite element model was established;the second invariant of deviatoric stress(J_(2))and horizontal stress index were introduced to analyze plastic zone and stress evolution after UCS mining.Results show that J_(2)distributes symmetrically,with its peak diffusing downward and attenuating in a“/”-shaped pattern.Six schemes were simulated to compare plastic zone distributions at different positions,revealing that the optimal layout consists of a roadway alignment with the RCP center.Based on roadway layout and roof conditions,a cooperative control scheme was proposed:deep,strong anchorage with long cables across the RCP,and shallow stable support with short bolts in the ECDCS.This scheme secures roof cables anchored to the UCS RCP roof to achieve cross-seam anchorage.On-site borehole peeping and loose circle tests confirm smooth surrounding rock hole walls and limited failure range.Specifically,surrounding rock deformation and roof separation were controlled within 200 mm and 80 mm,respectively,with stable bolt/cable support resistance.These results offer an innovative solution for roadway layout design and support strategies under RCP in ECDCS,with significant engineering application value.展开更多
It is of great significance to study the failure mode of mining roadways for safe coal mining.The unconventional asymmetric failure(UAF)phenomenon was discovered in the 9106 ventilation roadway of Wangzhuang coal mine...It is of great significance to study the failure mode of mining roadways for safe coal mining.The unconventional asymmetric failure(UAF)phenomenon was discovered in the 9106 ventilation roadway of Wangzhuang coal mine in Shanxi Province.The main manifestation is that the deformation of the roadway on the coal side is much greater than that on the coal pillar side.A comprehensive study was conducted on on-site detection,theoretical analysis,laboratory tests and numerical simulation of the UAF phenomenon.On-site detection shows that the deformation of the coal sidewall can reach 50–80 cm,and the failure zone depth can reach 3 m.The deformation and fracture depth on the coal pillar side are much smaller than those on the coal side.A calculation model for the principal stress of surrounding rock when the axial direction of the roadway is inconsistent with the in-situ stress field was established.The distribution of the failure zone on both sides of the roadway has been defined by the combined mining induced stress.The true triaxial test studied the mechanical mechanism of rock mass fracture and crack propagation on both sides of the roadway.The research results indicate that the axial direction,stress field distribution,and mining induced stress field distribution of the roadway jointly affect the asymmetric failure mode of the roadway.The angle between the axis direction of the roadway and the maximum horizontal stress field leads to uneven distribution of the principal stress field on both sides.The differential distribution of mining induced stress exacerbates the asymmetric distribution of principal stress in the surrounding rock.The uneven stress distribution on both sides of the roadway is the main cause of UAF formation.The research results can provide mechanical explanations and theoretical support for the control of surrounding rock in roadways with similar failure characteristics.展开更多
As coal mining progresses to greater depths,controlling the stability of surrounding rock in deep roadways has become an increasingly complex challenge.Although four-dimensional(4D)support theoretically offers unique ...As coal mining progresses to greater depths,controlling the stability of surrounding rock in deep roadways has become an increasingly complex challenge.Although four-dimensional(4D)support theoretically offers unique advantages in maintaining the stability of rock mass,the disaster evolution processes and multi-source information response characteristics in deep roadways with 4D support remain unclear.Consequently,a large-scale physical model testing system and self-designed 4D support components were employed to conduct similarity model tests on the surrounding rock failure process under unsupported(U-1),traditional bolt-mesh-cable support(T-2),and 4D support(4D-R-3)conditions.Combined with multi-source monitoring techniques,including stress–strain,digital image correlation(DIC),acoustic emission(AE),microseismic(MS),parallel electric(PE),and electromagnetic radiation(EMR),the mechanical behavior and multi-source information responses were comprehensively analyzed.The results show that the peak stress and displacement of the models are positively correlated with the support strength.The multi-source information exhibits distinct response characteristics under different supports.The response frequency,energy,and fluctuationsof AE,MS,and EMR signals,along with the apparent resistivity(AR)high-resistivity zone,follow the trend U-1>T-2>4D-R-3.Furthermore,multi-source information exhibits significantdifferences in sensitivity across different phases.The AE,MS,and EMR signals exhibit active responses to rock mass activity at each phase.However,AR signals are only sensitive to the fracture propagation during the plastic yield and failure phases.In summary,the 4D support significantlyenhances the bearing capacity and plastic deformation of the models,while substantially reducing the frequency,energy,and fluctuationsof multi-source signals.展开更多
Based on geological and mining characteristics,coal mine roadways under complex conditions were divided into five types,for each type the deformation and damage characteristics of rocks surrounding roadways were analy...Based on geological and mining characteristics,coal mine roadways under complex conditions were divided into five types,for each type the deformation and damage characteristics of rocks surrounding roadways were analyzed.The recent developments of roadway support technologies were introduced abroad,based on the experiences of supports for deep and complex roadways from Germany,the United States and Australia.The history and achievements of roadway support technologies in China were detailed,including rock bolting,steel supports,grouting reinforcement and combined supports.Four typical support and reinforcement case studies were analyzed,including a high stressed roadway 1,000 m below the surface,a roadway surrounded by severely weak and broken rocks,a chamber surrounded by weak and broken rocks,and a roadway with very soft and swelling rocks.Based on studies and practices in many years,rock bolting has become the mainstream roadway support form in China coal mines,and steel supports,grouting reinforcement and combined supports have also been applied at proper occasions,which have provided reliable technical measures for the safe and high effective construction and mining of underground coal mines.展开更多
The bolt support quality of coal roadways is one of the important factors for the efficiency and security of coal production. By means of a self-developed technique and equipment of random non-destructive testing, non...The bolt support quality of coal roadways is one of the important factors for the efficiency and security of coal production. By means of a self-developed technique and equipment of random non-destructive testing, non-destructive detection and pre-warning analysis on the quality of bolt support in deep roadways of mining districts were performed in a number of mining areas. The measured data were obtained in the detection instances of abnormal in-situ stress and support invalidation etc. The corresponding relation between axial bolt load variation and roadway surrounding rock deformation and stability was summarized in different mining service stages. Pre-warning technology of roadway surrounding rock stability is proposed based on the detection of axial bolt load. Meanwhile, pre-warning indicators of axial bolt load in different mining service stages are offered and some successful pre-warning cases are also illustrated.The research results show that the change rules of axial bolt load in different mining service stages are quite similar in different mining areas. The change of axial bolt load is in accord with the adjustment of surrounding rock stress, which can consequently reflect the deformation and stability state of roadway surrounding rock. Through the detection of axial bolt load in different sections of roadways, the status of real-time bolt support quality can be reflected; meanwhile, the rationality of bolt support design can be evaluated which provides reference for bolting parameters optimization.展开更多
Abutment pressure distribution is different when a longwall panel is passing through the abandoned gate roads in a damaged coal seam. According to the geological condition of panel E13103 in Cuijiazhai Coal Mine in Ch...Abutment pressure distribution is different when a longwall panel is passing through the abandoned gate roads in a damaged coal seam. According to the geological condition of panel E13103 in Cuijiazhai Coal Mine in China, theoretical analysis and finite element numerical simulation were used to determine the front pressure distribution characteristics when the longwall face is 70, 50, 30, 20, 10, and 5 m from the abandoned roadways. The research results show that the influence range of abutment pressure is 40 to 45 m outby the face, and the peak value of front abutment pressure is related to the distance between the face and abandoned roadways. When the distance between the longwall face and abandoned roadways is reduced from 50 to 10 m, the front abutment pressure peak value kept increasing. When the distance is 10 m, it has reached the maximum. The peak value is located in 5 to 6 m outby the faceline. When the distance between the longwall face and abandoned roadways is reduced from 10 to 5 m, the front abutment pressure sharply decreases, the intact coal yields and is even in plastic state. The peak value transfers to the other side of the abandoned roadways. The research results provide a theoretical basis for determining the advance support distance of two roadways in the panel and the reinforcement for face stability when the longwall face is passing through the abandoned roadways.展开更多
Using digital laser dynamic caustics experimental system and conducting simulation experiment researched the influence rule of blasting excavation of a new roadway on neighboring existed different cross-section roadwa...Using digital laser dynamic caustics experimental system and conducting simulation experiment researched the influence rule of blasting excavation of a new roadway on neighboring existed different cross-section roadways. The experimental results show that the influence of blast load on adjacent roadway has a good relationship with the cross-section of roadway. The expansion distance of precrack existed in circular, arch-wall, rectangular roadway is respectively 1.76, 1.61 and 0 cm under blast load.At the same time, the direct-blast side of rectangular roadway has more obvious damage compared with circular and arch-wall roadway. It explains that plane reflects more stress wave than arc, so that it exerts more tensile failure in the direct-blast side, which leads to less stress wave diffracting to the precrack in the back-blast side. When the precrack extends, higher value dynamic stress intensity factor in circular roadway works longer than that of arch-wall roadway. Indirectly, it explains that plane's weakening function on stress wave is significantly stronger than arc. Stress wave brings about self-evident influence on the upper and bottom endpoints of the rectangular roadway, and it respectively extends 1.03, 2.06 cm along the line link direction of the center of the blasthole and the upper and bottom endpoints on the right wall.展开更多
Using the spatial structure of the external staggered split-level panel layout,a combined support technology for adjacent roadways was developed and analyzed for a rock bolt and anchor cable mechanism.The influence of...Using the spatial structure of the external staggered split-level panel layout,a combined support technology for adjacent roadways was developed and analyzed for a rock bolt and anchor cable mechanism.The influence of the side rock bolt and anchor cable parameters on the mechanical properties of the anchorage body and the support stress distribution of the lateral coal body were revealed using the FLAC3D software.The optimal support parameters of the side rock bolts and anchor cables were subsequently determined,and the support effect of gob-side entry in a mining scenario was verified.The results show that the support of the side rock bolts and anchor cables improves the mechanical properties and stress state of the anchorage body,producing a good protective effect on the coal body of the air-intake entry roof and side wall.This is beneficial to the stability of the side wall and the realization of the suspension effect for roof rock bolts and anchor cables,which in turn makes the surrounding rock maintenance of the gob-side entry to a thick coal seam more favorable.展开更多
This paper describes the procedures for design of supports and stabilization measures in the roadways.The procedures are based on the system developed in Ostrava-Karvina coal basin in Czech Republic.The calculation of...This paper describes the procedures for design of supports and stabilization measures in the roadways.The procedures are based on the system developed in Ostrava-Karvina coal basin in Czech Republic.The calculation of load bearing capacity of roadway supports contains the period of roadway construction and mining in the vicinities,based on the size of the natural rock arch.The loading of supports during mining comes from a stress wave in the rock mass in the forefront of coalface and the caving area of mined-out panel.The input data for the calculation method are deduced according to in-situ measurements of convergence and displacement in the roadways.展开更多
The axial direction of a roadway often forms a certain spatial angle with the in-situ stress field.Variations in the spatial angles can lead to differences in the stress environment in which the roadway is exposed.Dif...The axial direction of a roadway often forms a certain spatial angle with the in-situ stress field.Variations in the spatial angles can lead to differences in the stress environment in which the roadway is exposed.Different forms of failure characteristics occur in the roadway.In order to study the failure mechanism with different spatial characteristics,rock-like material specimens with holes in 9 different horizontal and vertical angles were designed.The true triaxial test system was used to carry out the test with the same loading path.The results show that the horizontal angle a and vertical angle β have a significant effect on the specimen strength,specimen rupture angle,and the form of spalling failure in the hole.The spatial angle leads to the formation of asymmetric heterotype V-notches in both sides within the hole.The asymmetry is evident in both the depth and extent of spalling.The strength of the specimen increases and then decreases with increasing vertical angle β.The rupture angle increases and then decreases with increasing horizontal angle a and increases with the increase of the vertical angle β.The stress analytical model of the specimen under three-dimensional compression was established.The distribution of principal stresses around the holes was theoretically analyzed.It is found that the presence of spatial angle changes the distribution of principal stresses around the hole from symmetric to asymmetric distribution.The shift of the principal stresses is responsible for the change from a V-notch to a heterotype V-notch.展开更多
A rationally designed support for deep roadways excavated in broken soft rock under high stress was investigated. The deformation and failure characteristics and the mechanism of ''yielding support'' w...A rationally designed support for deep roadways excavated in broken soft rock under high stress was investigated. The deformation and failure characteristics and the mechanism of ''yielding support'' was studied for anchor bolts and cables. The rail roadway of the 2-501 working face in the Liyazhuang Mine of the Huozhou coal area located in Shanxi province was used for field trials. The geological conditions used there were used during the design phase. The new ''highly resistant, yielding'' support system has a core of high strength, yielding bolts and anchor cables. The field tests show that this support system adapts well to the deformation and pressure in the deep broken soft rock. The support system effectively controls damage to the roadway and ensures the long term stability of the wall rock and safe production in the coal mine. This provides a remarkable economic and social benefit and has broad prospects for fur- ther application.展开更多
Grouting is an effective method to improve the integrity and stability of fractured rocks that surround deep roadways.After years of research and practice,various theories and a complete set of grouting technologies f...Grouting is an effective method to improve the integrity and stability of fractured rocks that surround deep roadways.After years of research and practice,various theories and a complete set of grouting technologies for deep roadways with fractured rocks have been developed and are widely applied in Chinese coal mining production.This paper systematically summarizes and analyzes the research results concerning the theory,design,materials,processes,and equipment for the grouting and reinforcement of fractured rocks surrounding deep roadways.Specifically,in terms of grouting methods,pregrouting,groutingwhile-excavation,and postgrouting methods are explored;in terms of grouting theory,backfill grouting,compaction grouting,infiltration grouting,and fracture grouting theories are studied.In addition,this paper also studies grouting borehole arrangement,water-cement ratio,grouting pressure,grouting volume,grout diffusion radius,and other grouting parameters and their determination methods.On this basis,this paper explores the physical and mechanical properties of organic and organic-inorganic composite grouting materials,and assess grouting reinforcement quality testing methods and instruments.Taken as the field cases,the application of pregrouting in front of heading faces,groutingwhile-excavation,and postgrouting in the Kouzidong coal mine are then introduced,and the effects of the grouting reinforcements are evaluated.This paper proposes a development direction for grouting technology based on problems existing in the grouting reinforcement of fractured rocks surrounding deep roadways.展开更多
To ameliorate the defects of insufcient support resistance of traditional roadside flling bodies for gob-side entry retaining(GER),overcome the inability to adapt to the deformation of surrounding rock,and isolate the...To ameliorate the defects of insufcient support resistance of traditional roadside flling bodies for gob-side entry retaining(GER),overcome the inability to adapt to the deformation of surrounding rock,and isolate the goaf efectively,a new type of high-water material as a roadside flling body for GER technology with double roadways was proposed.The instability analysis and control technology of GER with double roadways by flling high-water material into a gently inclined coal seam were studied.The basic mechanical properties of the new high-water material were investigated through laboratory experiments,and their main advantages were identifed.The reasonable width of the roadside flling wall of a high-water material was obtained by combining ground pressure observation and theoretical calculations.The distribution characteristics of the stress and plastic zone of surrounding rock of GER after being stabilized by the disturbance of the working face were studied using numerical simulations,and the failure range of GER by flling with high-water material was revealed.Based on this,a coupling control technology of anchor cables and bolts+single props+metal mesh+anchor bolts is proposed.Through the coupling methods of arranging borehole peeping and observing the convergences of surrounding rock,the results demonstrate that GER with double roadways by flling with a 1.8-m-wide high-water material has a good control efect.The above research will play an active role in promoting the application of high-water materials in GER roadside flling.展开更多
In deep underground mining,achieving stable support for roadways along with long service life is critical and the complex geological environment at such depths frequently presents a major challenge.Owing to the coupli...In deep underground mining,achieving stable support for roadways along with long service life is critical and the complex geological environment at such depths frequently presents a major challenge.Owing to the coupling action of multiple factors such as deep high stress,adjacent faults,cross-layer design,weak lithology,broken surrounding rock,variable cross-sections,wide sections up to 9.9 m,and clusters of nearby chambers,there was severe deformation and breakdown in the No.10 intersection of the roadway of large-scale variable cross-section at the−760 m level in a coal mine.As there are insufcient examples in engineering methods pertaining to the geological environment described above,the numerical calculation model was oversimplifed and support theory underdeveloped;therefore,it is imperative to develop an efective support system for the stability and sustenance of deep roadways.In this study,a quantitative analysis of the geological environment of the roadway through feld observations,borehole-scoping,and ground stress testing is carried out to establish the FLAC 3D variable cross-section crossing roadway model.This model is combined with the strain softening constitutive(surrounding rock)and Mohr–Coulomb constitutive(other deep rock formations)models to construct a compression arch mechanical model for deep soft rock,based on the quadratic parabolic Mohr criterion.An integrated control technology of bolting and grouting that is mainly composed of a high-strength hollow grouting cable bolt equipped with modifed cement grouting materials and a high-elongation cable bolt is developed by analyzing the strengthening properties of the surrounding rock before and after bolting,based on the Heok-Brown criterion.As a result of on-site practice,the following conclusions are drawn:(1)The plastic zone of the roof of the cross roadway is approximately 6 m deep in this environment,the tectonic stress is nearly 30 MPa,and the surrounding rock is severely fractured.(2)The deformation of the roadway progressively increases from small to large cross-sections,almost doubling at the largest cross-section.The plastic zone is concentrated at the top plate and shoulder and decreases progressively from the two sides to the bottom corner.The range of stress concentration at the sides of the intersection roadway close to the passageway is wider and higher.(3)The 7 m-thick reinforced compression arch constructed under the strengthening support scheme has a bearing capacity enhanced by 1.8 to 2.3 times and increase in thickness of the bearing structure by 1.76 times as compared to the original scheme.(4)The increase in the mechanical parameters c andφof the surrounding rock after anchoring causes a signifcant increase inσt;the pulling force of the cable bolt beneath the new grouting material is more than twice that of ordinary cement grout,and according to the test,the supporting stress feld shows that the 7.24 m surrounding rock is compacted and strengthened in addition to providing a strong foundation for the bolt(cable).On-site monitoring shows that the 60-days convergence is less than 30 mm,indicating that the stability control of the roadway is successful.展开更多
We adopt the concept of generalized plane strain to model a roadway in a stress field.This can avoid limitations caused by simplifying the stress analysis as plane strain.FLAC^(3D)was used to investigate the maximum t...We adopt the concept of generalized plane strain to model a roadway in a stress field.This can avoid limitations caused by simplifying the stress analysis as plane strain.FLAC^(3D)was used to investigate the maximum tensile stress and displacement of a roadway in a known stress field for angles,α,between the roadway axial direction and the maximum principal stress of 0°,30°,45°,60°and 90°.This theory was applied to the analysis of an engineering case.The results indicate that stress and displacement of the surrounding rock increase as the angle,α,increases.This provides some significant guidance for a reasonable layout of roadways in a known stress field.展开更多
基金support from National Natural Science Foundation of China(Grant No.52474142)The National Science Fund for Distinguished Young Scholars(No.51925402),Chinathe China Postdoctoral Science Foundation(Grant No.2021M702049).
文摘Roof pre-fracture poses a considerable risk during the re-mining of residual coal above abandoned roadways,threatening the safety of the mining faces.This study employs a Winkler foundation beam model for mechanical analysis of roof structures and adopts a multivariate nonlinear analysis approach to explore the synergistic load-bearing effects within the'coal pillar-support-backfill body'system during the fill and re-mining processes above these roadways.The findings demonstrate that backfill mining significantly reduces stress concentrations in coal pillars and reduces excessive bending moments in roofs near abandoned roadways.The roof deflection equation incorporates three critical factors affecting stability during backfill mining:the width of the coal pillar(L_(3)),the working resistance of the support(q_(z)),and the elastic foundation coefficient of the backfill material(kcÞ.Under single-factor conditions,the impact sequence on roof stability in the coal pillar zone is·k_(c)>L_(3)>q_(z).Further,multivariate nonlinear analysis reveals the interactions within the'coal-support-backfill'structure,indicating that in terms of roof control,the interaction terms are ordered as L_(3)·k_(c)>q_(z)·k_(c)>L_(3)q_(z).Therefore,priority should be given to adjusting the coal pillar width and backfill strength,followed by modifications to the support resistance and backfill strength during the recovery of abandoned roadways.An improved understanding of these interactions will help optimize strategies for the recovery of residual coal through abandoned roadways,thereby enhancing the stability and safety of mining operations under complex geological conditions.
基金funded by the National Natural Science Foundation of China (No. 52304133)the National Key R&D Program of China (No. 2022YFC3004605)the Department of Science and Technology of Liaoning Province (No. 2023-BS-083)。
文摘Rockbursts, which mainly affect mining roadways, are dynamic disasters arising from the surrounding rock under high stress. Understanding the interaction between supports and the surrounding rock is necessary for effective rockburst control. In this study, the squeezing behavior of the surrounding rock is analyzed in rockburst roadways, and a mechanical model of rockbursts is established considering the dynamic support stress, thus deriving formulas and providing characteristic curves for describing the interaction between the support and surrounding rock. Design principles and parameters of supports for rockburst control are proposed. The results show that only when the geostress magnitude exceeds a critical value can it drive the formation of rockburst conditions. The main factors influencing the convergence response and rockburst occurrence around roadways are geostress, rock brittleness, uniaxial compressive strength, and roadway excavation size. Roadway support devices can play a role in controlling rockburst by suppressing the squeezing evolution of the surrounding rock towards instability points of rockburst. Further, the higher the strength and the longer the impact stroke of support devices with constant resistance, the more easily multiple balance points can be formed with the surrounding rock to control rockburst occurrence. Supports with long impact stroke allow adaptation to varying geostress levels around the roadway, aiding in rockburst control. The results offer a quantitative method for designing support systems for rockburst-prone roadways. The design criterion of supports is determined by the intersection between the convergence curve of the surrounding rock and the squeezing deformation curve of the support devices.
基金supported by the National Natural Science Foundation of China(Nos.U24A2088,42177130,42277174,and 42477166).
文摘As coal mining depth increases,the combined effects of high stress,mining stress,and fault structures make dynamic impact hazards more frequent.The reproduction of dynamic impact phenomena is basis for studying their occurrence patterns and control mechanisms.Physical simulation test represents an efficacious methodology.However,there is currently a lack of simulation devices that can effectively simulate two types of dynamic impact phenomena,including high stress and fault slip dynamic impact.To solve aforementioned issues,the physical simulation test system for dynamic impact in deep roadways developed by authors is employed to carry out comparative tests of high stress and fault slip dynamic impact.The phenomena of high stress and fault slip dynamic impact are reproduced successfully.A comparative analysis is conducted on dynamic phenomena,stress evolution,roadway deformation,and support force.The high stress dynamic impact roadway instability mode,which is characterized by the release of high energy accompanied by symmetric damage,and the fault slip dynamic impact roadway instability mode,which is characterized by the propagation of unilateral stress waves accompanied by asymmetric damage,are clarified.On the basis,the differentiated control concepts for different types of dynamic impact in deep roadways are proposed.
基金funded by the Science and Technology Innovation Talent Project of Bingtuan(2023CB008-28)the Startup Project of Scienific Research for High-level Talents in Shihezi University(RCZK202023)+1 种基金the Young Innovative Talents Program of Shihezi University(CXPY202116)the Xinjiang Production and Construction Corps(XPCC)Science and Technology Innovation Youth Top Talent Program(2024DB050)。
文摘Filling the roadways of the abandoned mines can enhance the structural stability of surrounding ore bodies.However,existing studies on backfill reinforcement for different roadway shapes focus on mechanical properties and failure modes,with less emphasis on the specific mechanisms governed by crack-type evolution during the failure process.This study investigates the mechanical effects of three backfill conditions(unfilled,soft-filled,and hard-filled)on six common roadway geometries with scaled specimens subjected to uniaxial compression tests.Crack initiation and propagation were monitored with digital image correlation(DIC).Results show:(1)Roadway geometry strongly affects strength and fracture behavior.With identical effective apertures,the horseshoe-shaped specimen reaches a maximum strength of 23.5 MPa,compared to 16.7 MPa for the square specimen.Sharp-cornered geometries exhibit pronounced stress concentrations,leading to early cracking and faster failure.(2)Fillings improve strength and mitigate damage.Hard fillings(≈1/6 of the specimen strength)control cracks more effectively than soft ones(≈1/3 strength).For circular specimens,the crack initiation stress increases by 99.7%and 105.6%after filling with soft and hard filler,respectively,relative to the unfilled case(9.25 MPa),representing the greatest enhancement among all geometries.(3)DIC analysis identifies tensile,shear,and mixed-mode cracks.Unfilled specimens frequently shift between modes,whereas filled ones show more stable patterns with delayed crack initiation.(4)Energy analysis reveals higher peak dissipation in unfilled specimens.Filling improves energy dissipation performance across all roadway shapes,with both fillers showing the most significant suppression effect in triangular specimens—by 63.0%and 58.3%for soft and hard fillers,respectively—and the least effect in arched-wall specimens—12.9%and 17.6%,respectively.These results contribute to understanding the damaging effects caused by the dynamic evolution of crack types in backfilled roadways and surrounding mine bodies in underground rock engineering.
基金This research was supported by the National Natural Science Foundation of China(Grant Nos.51974187)Intelligent Mine Blasting and Innovative Technology Platform Construction(LJ232410146045)Liaoning Revitalization Talents Program(XLYC2203173).
文摘Cross roadway collapses are a common occurrence in underground mining operations.While the influence of mining blasts on the stability of surrounding rock is acknowledged,the underlying mechanisms remain inadequately understood.This study investigates the characteristics and mechanisms of collapse in a shallow buried cross roadway subjected to mining blast disturbances,drawing insights from an engineering project in Anshan City,Northeast China.A strain-softening model based on unified strength theory was developed to effectively calculate and analyze the loosened zone thickness and surrounding rock displacement.The PFC3D-FLAC3D coupling method was employed to clarify the concentrated collapse area within the cross roadway,providing insight into the collapse mechanism through a cross-sectional model of the concentrated region.Results demonstrate that 50%of the cross roadway collapsed following the mining blast.Subsidence at the intersection was approximately one-fifth(0.66 m)of cross roadway’s net height,exceeding subsidence in other areas by 1.3.Under the action of repeated mining blasting,the cross section of the connection roadway forms a semi-elliptical high tensile stress zone.After the cumulative damage of the surrounding rock of the connection roadway exceeds the ultimate yield strength,the cumulative stress release causes the tensile failure of the surrounding rock.The plastic zone of the connecting roadway expands to three times of the initial,and continues to develop.The surrounding rock on both sides experienced tensile stress,cumulative stress release,and the vertical propagation of tensile cracks.
基金supported by the National Natural Science Foundation of China(No.52074296)。
文摘In extremely close-distance coal seam(ECDCS)mining,section coal pillars remain after upper coal seam(UCS)extraction.Thus,for layout and support design of lower coal seam(LCS)mining roadways,it is critical to account for UCS goaf deterioration and residual coal pillar(RCP)-induced stress disturbance.Taking the 6.4 m layer spacing of ECDCS mining in Nanyangpo Coal Mine as a case study,this research aimed to determine the optimal layout and surrounding rock control method for the 24202-ventilation roadway in the RCP area.First,the challenges of roadway layout and support under RCP were clarified:three layout methods face distinct RCPinduced stress disturbances and goaf-related roof damage.A finite element model was established;the second invariant of deviatoric stress(J_(2))and horizontal stress index were introduced to analyze plastic zone and stress evolution after UCS mining.Results show that J_(2)distributes symmetrically,with its peak diffusing downward and attenuating in a“/”-shaped pattern.Six schemes were simulated to compare plastic zone distributions at different positions,revealing that the optimal layout consists of a roadway alignment with the RCP center.Based on roadway layout and roof conditions,a cooperative control scheme was proposed:deep,strong anchorage with long cables across the RCP,and shallow stable support with short bolts in the ECDCS.This scheme secures roof cables anchored to the UCS RCP roof to achieve cross-seam anchorage.On-site borehole peeping and loose circle tests confirm smooth surrounding rock hole walls and limited failure range.Specifically,surrounding rock deformation and roof separation were controlled within 200 mm and 80 mm,respectively,with stable bolt/cable support resistance.These results offer an innovative solution for roadway layout design and support strategies under RCP in ECDCS,with significant engineering application value.
基金financially supported by the National Natural Science Foundation of China(Nos.52225404,12532020,52394192 and 42321002)Key Research and Development Program Projects of Xinjiang Uygur Autonomous Region(No.2024B03017)Doctoral Startup Foundation of Fuyang Normal University,China(No.2025KYQD0124)。
文摘It is of great significance to study the failure mode of mining roadways for safe coal mining.The unconventional asymmetric failure(UAF)phenomenon was discovered in the 9106 ventilation roadway of Wangzhuang coal mine in Shanxi Province.The main manifestation is that the deformation of the roadway on the coal side is much greater than that on the coal pillar side.A comprehensive study was conducted on on-site detection,theoretical analysis,laboratory tests and numerical simulation of the UAF phenomenon.On-site detection shows that the deformation of the coal sidewall can reach 50–80 cm,and the failure zone depth can reach 3 m.The deformation and fracture depth on the coal pillar side are much smaller than those on the coal side.A calculation model for the principal stress of surrounding rock when the axial direction of the roadway is inconsistent with the in-situ stress field was established.The distribution of the failure zone on both sides of the roadway has been defined by the combined mining induced stress.The true triaxial test studied the mechanical mechanism of rock mass fracture and crack propagation on both sides of the roadway.The research results indicate that the axial direction,stress field distribution,and mining induced stress field distribution of the roadway jointly affect the asymmetric failure mode of the roadway.The angle between the axis direction of the roadway and the maximum horizontal stress field leads to uneven distribution of the principal stress field on both sides.The differential distribution of mining induced stress exacerbates the asymmetric distribution of principal stress in the surrounding rock.The uneven stress distribution on both sides of the roadway is the main cause of UAF formation.The research results can provide mechanical explanations and theoretical support for the control of surrounding rock in roadways with similar failure characteristics.
基金supported by the National Natural Science Foundation of China(Grant Nos.U22A20598 and 52104107)the"Qinglan Project"of Jiangsu Colleges and Universities,Young Elite Scientists Sponsorship Program of Jiangsu Province(Grant No.TJ-2023-086).
文摘As coal mining progresses to greater depths,controlling the stability of surrounding rock in deep roadways has become an increasingly complex challenge.Although four-dimensional(4D)support theoretically offers unique advantages in maintaining the stability of rock mass,the disaster evolution processes and multi-source information response characteristics in deep roadways with 4D support remain unclear.Consequently,a large-scale physical model testing system and self-designed 4D support components were employed to conduct similarity model tests on the surrounding rock failure process under unsupported(U-1),traditional bolt-mesh-cable support(T-2),and 4D support(4D-R-3)conditions.Combined with multi-source monitoring techniques,including stress–strain,digital image correlation(DIC),acoustic emission(AE),microseismic(MS),parallel electric(PE),and electromagnetic radiation(EMR),the mechanical behavior and multi-source information responses were comprehensively analyzed.The results show that the peak stress and displacement of the models are positively correlated with the support strength.The multi-source information exhibits distinct response characteristics under different supports.The response frequency,energy,and fluctuationsof AE,MS,and EMR signals,along with the apparent resistivity(AR)high-resistivity zone,follow the trend U-1>T-2>4D-R-3.Furthermore,multi-source information exhibits significantdifferences in sensitivity across different phases.The AE,MS,and EMR signals exhibit active responses to rock mass activity at each phase.However,AR signals are only sensitive to the fracture propagation during the plastic yield and failure phases.In summary,the 4D support significantlyenhances the bearing capacity and plastic deformation of the models,while substantially reducing the frequency,energy,and fluctuationsof multi-source signals.
文摘Based on geological and mining characteristics,coal mine roadways under complex conditions were divided into five types,for each type the deformation and damage characteristics of rocks surrounding roadways were analyzed.The recent developments of roadway support technologies were introduced abroad,based on the experiences of supports for deep and complex roadways from Germany,the United States and Australia.The history and achievements of roadway support technologies in China were detailed,including rock bolting,steel supports,grouting reinforcement and combined supports.Four typical support and reinforcement case studies were analyzed,including a high stressed roadway 1,000 m below the surface,a roadway surrounded by severely weak and broken rocks,a chamber surrounded by weak and broken rocks,and a roadway with very soft and swelling rocks.Based on studies and practices in many years,rock bolting has become the mainstream roadway support form in China coal mines,and steel supports,grouting reinforcement and combined supports have also been applied at proper occasions,which have provided reliable technical measures for the safe and high effective construction and mining of underground coal mines.
基金the State Key Research Development Program of China(No.2016YFC0600705)the Fundamental Research Funds for the Central Universities(No.2015XKZD06)+1 种基金the National Natural Science Foundation of China(Nos.51227003,51404250,51504243,51474215,51404262 and 51323004)the Natural Science Foundation of Jiangsu Province,China(Nos.BK20150191 and BK20140213)
文摘The bolt support quality of coal roadways is one of the important factors for the efficiency and security of coal production. By means of a self-developed technique and equipment of random non-destructive testing, non-destructive detection and pre-warning analysis on the quality of bolt support in deep roadways of mining districts were performed in a number of mining areas. The measured data were obtained in the detection instances of abnormal in-situ stress and support invalidation etc. The corresponding relation between axial bolt load variation and roadway surrounding rock deformation and stability was summarized in different mining service stages. Pre-warning technology of roadway surrounding rock stability is proposed based on the detection of axial bolt load. Meanwhile, pre-warning indicators of axial bolt load in different mining service stages are offered and some successful pre-warning cases are also illustrated.The research results show that the change rules of axial bolt load in different mining service stages are quite similar in different mining areas. The change of axial bolt load is in accord with the adjustment of surrounding rock stress, which can consequently reflect the deformation and stability state of roadway surrounding rock. Through the detection of axial bolt load in different sections of roadways, the status of real-time bolt support quality can be reflected; meanwhile, the rationality of bolt support design can be evaluated which provides reference for bolting parameters optimization.
基金supported by National Key R&D Program of China (No. 2017YFC060300204)Yue Qi Young Scholar Project,CUMTB and Yue Qi Distinguished Scholar Project (No. 800015Z1138)China University of Mining & Technology, Beijing
文摘Abutment pressure distribution is different when a longwall panel is passing through the abandoned gate roads in a damaged coal seam. According to the geological condition of panel E13103 in Cuijiazhai Coal Mine in China, theoretical analysis and finite element numerical simulation were used to determine the front pressure distribution characteristics when the longwall face is 70, 50, 30, 20, 10, and 5 m from the abandoned roadways. The research results show that the influence range of abutment pressure is 40 to 45 m outby the face, and the peak value of front abutment pressure is related to the distance between the face and abandoned roadways. When the distance between the longwall face and abandoned roadways is reduced from 50 to 10 m, the front abutment pressure peak value kept increasing. When the distance is 10 m, it has reached the maximum. The peak value is located in 5 to 6 m outby the faceline. When the distance between the longwall face and abandoned roadways is reduced from 10 to 5 m, the front abutment pressure sharply decreases, the intact coal yields and is even in plastic state. The peak value transfers to the other side of the abandoned roadways. The research results provide a theoretical basis for determining the advance support distance of two roadways in the panel and the reinforcement for face stability when the longwall face is passing through the abandoned roadways.
基金provided by the National Natural Science Foundation of China (Nos. 51274204 and 51134025)National Key Basic Research Program (No. 2010CB732002)The Ministry of Education Program for New Century Excellent Talents to Support Project of China (No. NCET-12-0965)
文摘Using digital laser dynamic caustics experimental system and conducting simulation experiment researched the influence rule of blasting excavation of a new roadway on neighboring existed different cross-section roadways. The experimental results show that the influence of blast load on adjacent roadway has a good relationship with the cross-section of roadway. The expansion distance of precrack existed in circular, arch-wall, rectangular roadway is respectively 1.76, 1.61 and 0 cm under blast load.At the same time, the direct-blast side of rectangular roadway has more obvious damage compared with circular and arch-wall roadway. It explains that plane reflects more stress wave than arc, so that it exerts more tensile failure in the direct-blast side, which leads to less stress wave diffracting to the precrack in the back-blast side. When the precrack extends, higher value dynamic stress intensity factor in circular roadway works longer than that of arch-wall roadway. Indirectly, it explains that plane's weakening function on stress wave is significantly stronger than arc. Stress wave brings about self-evident influence on the upper and bottom endpoints of the rectangular roadway, and it respectively extends 1.03, 2.06 cm along the line link direction of the center of the blasthole and the upper and bottom endpoints on the right wall.
基金National Natural Science Foundation of Surface Project of China(Grant Nos.5177428952074291)+2 种基金The National Natural Science Foundation of the Youth Science Foundation of China(Grant No.51404270)The Fundamental Research Funds for the Central Universities(Grant No.2011QZ06)The Open Fund of State Key Laboratory of Coal Resources in Western China(Grant No.SKLCRKF1903).
文摘Using the spatial structure of the external staggered split-level panel layout,a combined support technology for adjacent roadways was developed and analyzed for a rock bolt and anchor cable mechanism.The influence of the side rock bolt and anchor cable parameters on the mechanical properties of the anchorage body and the support stress distribution of the lateral coal body were revealed using the FLAC3D software.The optimal support parameters of the side rock bolts and anchor cables were subsequently determined,and the support effect of gob-side entry in a mining scenario was verified.The results show that the support of the side rock bolts and anchor cables improves the mechanical properties and stress state of the anchorage body,producing a good protective effect on the coal body of the air-intake entry roof and side wall.This is beneficial to the stability of the side wall and the realization of the suspension effect for roof rock bolts and anchor cables,which in turn makes the surrounding rock maintenance of the gob-side entry to a thick coal seam more favorable.
基金the framework of the research plan:physical and environmental processes in lithosphere induced by anthropogenic activities (AV0Z30860518)
文摘This paper describes the procedures for design of supports and stabilization measures in the roadways.The procedures are based on the system developed in Ostrava-Karvina coal basin in Czech Republic.The calculation of load bearing capacity of roadway supports contains the period of roadway construction and mining in the vicinities,based on the size of the natural rock arch.The loading of supports during mining comes from a stress wave in the rock mass in the forefront of coalface and the caving area of mined-out panel.The input data for the calculation method are deduced according to in-situ measurements of convergence and displacement in the roadways.
基金supported by the NSFC projects(Nos.52225404,42321002,4204100030)Beijing Outstanding Young Scientist Program(No.BJJWZYJH01201911413037)the Excellent Youth Team of the Central Universities of China(No.2023YQTD01).
文摘The axial direction of a roadway often forms a certain spatial angle with the in-situ stress field.Variations in the spatial angles can lead to differences in the stress environment in which the roadway is exposed.Different forms of failure characteristics occur in the roadway.In order to study the failure mechanism with different spatial characteristics,rock-like material specimens with holes in 9 different horizontal and vertical angles were designed.The true triaxial test system was used to carry out the test with the same loading path.The results show that the horizontal angle a and vertical angle β have a significant effect on the specimen strength,specimen rupture angle,and the form of spalling failure in the hole.The spatial angle leads to the formation of asymmetric heterotype V-notches in both sides within the hole.The asymmetry is evident in both the depth and extent of spalling.The strength of the specimen increases and then decreases with increasing vertical angle β.The rupture angle increases and then decreases with increasing horizontal angle a and increases with the increase of the vertical angle β.The stress analytical model of the specimen under three-dimensional compression was established.The distribution of principal stresses around the holes was theoretically analyzed.It is found that the presence of spatial angle changes the distribution of principal stresses around the hole from symmetric to asymmetric distribution.The shift of the principal stresses is responsible for the change from a V-notch to a heterotype V-notch.
基金supported by the National Natural Science Foundation of China (No. 50874103)the National Basic Research Program of China (No. 2010CB226805)+1 种基金the Natural Science Foundation of Jiangsu Province (No. BK2008135)as well as by the Open Foundation of State Key Laboratory of Geomechanics and Deep Underground Engineering (No. SKLGDUEK0905)
文摘A rationally designed support for deep roadways excavated in broken soft rock under high stress was investigated. The deformation and failure characteristics and the mechanism of ''yielding support'' was studied for anchor bolts and cables. The rail roadway of the 2-501 working face in the Liyazhuang Mine of the Huozhou coal area located in Shanxi province was used for field trials. The geological conditions used there were used during the design phase. The new ''highly resistant, yielding'' support system has a core of high strength, yielding bolts and anchor cables. The field tests show that this support system adapts well to the deformation and pressure in the deep broken soft rock. The support system effectively controls damage to the roadway and ensures the long term stability of the wall rock and safe production in the coal mine. This provides a remarkable economic and social benefit and has broad prospects for fur- ther application.
基金Innovation and Entrepreneurship Funds of Tiandi Science&Technology Co.Ltd.,Grant/Award Number:2022-2-TD-MS013。
文摘Grouting is an effective method to improve the integrity and stability of fractured rocks that surround deep roadways.After years of research and practice,various theories and a complete set of grouting technologies for deep roadways with fractured rocks have been developed and are widely applied in Chinese coal mining production.This paper systematically summarizes and analyzes the research results concerning the theory,design,materials,processes,and equipment for the grouting and reinforcement of fractured rocks surrounding deep roadways.Specifically,in terms of grouting methods,pregrouting,groutingwhile-excavation,and postgrouting methods are explored;in terms of grouting theory,backfill grouting,compaction grouting,infiltration grouting,and fracture grouting theories are studied.In addition,this paper also studies grouting borehole arrangement,water-cement ratio,grouting pressure,grouting volume,grout diffusion radius,and other grouting parameters and their determination methods.On this basis,this paper explores the physical and mechanical properties of organic and organic-inorganic composite grouting materials,and assess grouting reinforcement quality testing methods and instruments.Taken as the field cases,the application of pregrouting in front of heading faces,groutingwhile-excavation,and postgrouting in the Kouzidong coal mine are then introduced,and the effects of the grouting reinforcements are evaluated.This paper proposes a development direction for grouting technology based on problems existing in the grouting reinforcement of fractured rocks surrounding deep roadways.
基金supported by the National Natural Science Foundation of China(Nos.52074296,52004286)the China Postdoctoral Science Foundation(Nos.2020T130701,2019M650895)the Fundamental Research Funds for the Central Universities(Nos.2022YJSNY18,2022XJNY02)。
文摘To ameliorate the defects of insufcient support resistance of traditional roadside flling bodies for gob-side entry retaining(GER),overcome the inability to adapt to the deformation of surrounding rock,and isolate the goaf efectively,a new type of high-water material as a roadside flling body for GER technology with double roadways was proposed.The instability analysis and control technology of GER with double roadways by flling high-water material into a gently inclined coal seam were studied.The basic mechanical properties of the new high-water material were investigated through laboratory experiments,and their main advantages were identifed.The reasonable width of the roadside flling wall of a high-water material was obtained by combining ground pressure observation and theoretical calculations.The distribution characteristics of the stress and plastic zone of surrounding rock of GER after being stabilized by the disturbance of the working face were studied using numerical simulations,and the failure range of GER by flling with high-water material was revealed.Based on this,a coupling control technology of anchor cables and bolts+single props+metal mesh+anchor bolts is proposed.Through the coupling methods of arranging borehole peeping and observing the convergences of surrounding rock,the results demonstrate that GER with double roadways by flling with a 1.8-m-wide high-water material has a good control efect.The above research will play an active role in promoting the application of high-water materials in GER roadside flling.
基金supported by the National Natural Science Foundation of China(Grant Nos.52074296,52004286)the China Postdoctoral Science Foundation(Grant Nos.2020T130701,2019M650895).
文摘In deep underground mining,achieving stable support for roadways along with long service life is critical and the complex geological environment at such depths frequently presents a major challenge.Owing to the coupling action of multiple factors such as deep high stress,adjacent faults,cross-layer design,weak lithology,broken surrounding rock,variable cross-sections,wide sections up to 9.9 m,and clusters of nearby chambers,there was severe deformation and breakdown in the No.10 intersection of the roadway of large-scale variable cross-section at the−760 m level in a coal mine.As there are insufcient examples in engineering methods pertaining to the geological environment described above,the numerical calculation model was oversimplifed and support theory underdeveloped;therefore,it is imperative to develop an efective support system for the stability and sustenance of deep roadways.In this study,a quantitative analysis of the geological environment of the roadway through feld observations,borehole-scoping,and ground stress testing is carried out to establish the FLAC 3D variable cross-section crossing roadway model.This model is combined with the strain softening constitutive(surrounding rock)and Mohr–Coulomb constitutive(other deep rock formations)models to construct a compression arch mechanical model for deep soft rock,based on the quadratic parabolic Mohr criterion.An integrated control technology of bolting and grouting that is mainly composed of a high-strength hollow grouting cable bolt equipped with modifed cement grouting materials and a high-elongation cable bolt is developed by analyzing the strengthening properties of the surrounding rock before and after bolting,based on the Heok-Brown criterion.As a result of on-site practice,the following conclusions are drawn:(1)The plastic zone of the roof of the cross roadway is approximately 6 m deep in this environment,the tectonic stress is nearly 30 MPa,and the surrounding rock is severely fractured.(2)The deformation of the roadway progressively increases from small to large cross-sections,almost doubling at the largest cross-section.The plastic zone is concentrated at the top plate and shoulder and decreases progressively from the two sides to the bottom corner.The range of stress concentration at the sides of the intersection roadway close to the passageway is wider and higher.(3)The 7 m-thick reinforced compression arch constructed under the strengthening support scheme has a bearing capacity enhanced by 1.8 to 2.3 times and increase in thickness of the bearing structure by 1.76 times as compared to the original scheme.(4)The increase in the mechanical parameters c andφof the surrounding rock after anchoring causes a signifcant increase inσt;the pulling force of the cable bolt beneath the new grouting material is more than twice that of ordinary cement grout,and according to the test,the supporting stress feld shows that the 7.24 m surrounding rock is compacted and strengthened in addition to providing a strong foundation for the bolt(cable).On-site monitoring shows that the 60-days convergence is less than 30 mm,indicating that the stability control of the roadway is successful.
基金supported by the National Basic Research Program of China(No.2010CB226805)the National Natural Science Foundation of China(Nos.50874103 and 50974115)+1 种基金the Natural Science Foundation of Jiangsu Province(No.KB2008135)the State Key Laboratory Fund(No.SKLGDUEK 0905)
文摘We adopt the concept of generalized plane strain to model a roadway in a stress field.This can avoid limitations caused by simplifying the stress analysis as plane strain.FLAC^(3D)was used to investigate the maximum tensile stress and displacement of a roadway in a known stress field for angles,α,between the roadway axial direction and the maximum principal stress of 0°,30°,45°,60°and 90°.This theory was applied to the analysis of an engineering case.The results indicate that stress and displacement of the surrounding rock increase as the angle,α,increases.This provides some significant guidance for a reasonable layout of roadways in a known stress field.
