Objective The distribution characteristics and formation mechanism of rearranged hopanes in hydrocarbon source rocks are affected by various geological conditions.Among these geological conditions,thermal action has a...Objective The distribution characteristics and formation mechanism of rearranged hopanes in hydrocarbon source rocks are affected by various geological conditions.Among these geological conditions,thermal action has an important influence on the formation of rearranged hopanes,which has been however little documented previously.展开更多
Composite rock layers are widely present in mining and tunnel construction projects,and are prone to dynamic tensile failure along bedding planes under dynamic disturbances.To ensure engineering safety,it is necessary...Composite rock layers are widely present in mining and tunnel construction projects,and are prone to dynamic tensile failure along bedding planes under dynamic disturbances.To ensure engineering safety,it is necessary to conduct research on the dynamic tensile characteristics under different working conditions.Considering the difficulty of on-site sampling,composite rock samples were prepared with cement mortar,and dynamic Brazilian splitting tests were carried out using split Hopkinson pressure bar(SHPB)equipment,a high-speed camera,and PFC^(2D)numerical software to explore their dynamic tensile properties under dynamic disturbance under different strength ratios and other factors.The results show that the dynamic tensile strength of samples exhibits a rising trend with the strength ratio and strain rate growth.As the incident angle increases from 0°to 90°,the stress contour deflects transform from center-splitting failure to tension-shear combined failure and back again.The influence of the incident order in different lithology rocks on the dynamic tensile strength of composite samples is controlled by strain rate,and when the strain rate increases to 400 s^(-1),the difference in strength due to the sequence of incident stress waves is within 5%.Based on PFC^(2D),the strength ratio of composite samples has a certain influence on the distribution of microfractures.With strength ratios equaling 1.5 or 2.0,the cracks are mainly concentrated on the softer material side,while a large number of cracks are distributed on both sides of the bedding plane with a strength ratio equal to 1.2.展开更多
In rock mass and mining engineering,shock waves induced by engineering disturbances significantly affect rock mass stability.To explore the dynamic mechanical behavior and energy dissipation mechanisms of single-fract...In rock mass and mining engineering,shock waves induced by engineering disturbances significantly affect rock mass stability.To explore the dynamic mechanical behavior and energy dissipation mechanisms of single-fractured composite rock masses under impact loading,a series of tests were conducted using a split Hopkinson pressure bar(SHPB)system with a 50 mm rod diameter.Specimens containing a single inclined fracture with seven different dip angles and located in different lithological layers were tested.The results show that both peak stress and peak strain exhibit a non-monotonic trend with increasing dip angleα-first decreasing,then increasing,reaching a minimum atα=45°.This behavior is attributed to enhanced energy concentration and dissipation in the fracture zone,where shear-dominated failure leads to more effective crack propagation and stress redistribution.Moreover,the proportion of crushing energy dissipation is significantly affected by the fracture dip angle,reaching a minimum atα=45°and a maximum atα=90°,indicating a transition from shear to tensile failure modes with increasing angle.Lithology also plays a crucial role:grey sandstone specimens absorbed more energy compared to yellow sandstone,implying higher impact resistance due to differences in microstructural cohesion.The evolution of fragment fractal dimension with increasing dip angle follows an"M-shaped"trend,reflecting changes in fragmentation intensity and failure mode.Notably,yellow sandstone tends to produce higher fractal dimensions,with larger mass but smaller volume of powdered debris,indicating more intense fragmentation.This study reveals the coupling effect of fracture dip angle and lithology on dynamic mechanical response and energy evolution,providing new insights into the failure mechanisms of layered composite rock masses under impact loading.展开更多
Joints are widely distributed structural defects in rock masses,and their geometric characteristics play a decisive role in the overall stability of rocks under complex stress conditions.To clarify the influence of jo...Joints are widely distributed structural defects in rock masses,and their geometric characteristics play a decisive role in the overall stability of rocks under complex stress conditions.To clarify the influence of joint geometry on the mechanical behavior of jointed rock under such conditions,this study investigated the mechanical properties and failure mechanisms of composite jointed rock specimens with varying joint roughness and joint dip angles.Three typical failure modes under triaxial loading were identified,and a mechanical analysis model incorporating joint roughness and dip angle was established.The failure mechanism was revealed,and a discrete element model was developed to analyze the micro-damage evolution process of the specimens.The results show that the mechanical parameters of the specimens exhibit pronounced anisotropy.Both the elastic modulus and peak strength reach their minimum values at a joint dip angle of 60°.Increasing joint roughness significantly reduces the degree of anisotropy and enhances the energy storage capacity of the specimens.A strong linear relationship is observed between the elastic strain energy and the peak deviatoric stress,confirming the applicability of the linear energy storage law in composite jointed rocks.Discrete element simulations revealed the evolution path and dominant types of microcracks between the joint and matrix.The joint dip angle governs the transition of dominant crack types from tensile to shear and then back to tensile.Increased joint roughness significantly suppresses damage localization along the joint and results in an approximately 20%increase in the proportion of shear microcracks within the matrix.These findings clarify the regulatory role of joint geometrical parameters in the damage evolution process.展开更多
To ensure safe and economical backfill mining,the mechanical response of the backfill–rock interaction system needs to be understood.The numerical investigation of the mechanical behavior of backfill–rock composite ...To ensure safe and economical backfill mining,the mechanical response of the backfill–rock interaction system needs to be understood.The numerical investigation of the mechanical behavior of backfill–rock composite structure(BRCS)under triaxial compression,which includes deformation,failure patterns,strength characteristics,and acoustic emission(AE)evolution,was proposed.The models used in the tests have one rough interface,two cement–iron tailings ratios(CTRs),four interface angles(IAs),and three confining pressures(CPs).Results showed that the deformation,strength characteristics,and failure patterns of BRCS under triaxial compression depend on IA,CP,and CTR.The stress–strain curves of BRCS under triaxial compression could be divided into five stages,namely,compaction,elasticity,yield,strain softening,and residual stress.The relevant AE counts have corresponding relationships with different stages.The triaxial compressive strengths of composites increase linearly with the increase of the CP.Furthermore,the CP stress strengthening effect occurs.When the IAs are45°and 60°,the failure areas of composites appear in the interface and backfill.When the IAs are 75°and 90°,the failure areas of composites appear in the backfill,interface,and rock.Moreover,the corresponding failure modes yield the combined shear failure.The research results provide the basis for further understanding of the stability of the BRCS.展开更多
In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic ...In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic emission technique was used to monitor the acoustic signal characteristics of composite rock specimens during the entire loading process. At the same time, an optical non-contact 3 D digital image correlation technique was used to study the evolution of axial strain field and the maximal strain field before and after the peak strength at different stress levels during the loading process. The effect of bedding plane inclination on the deformation and strength during uniaxial loading was analyzed. The methods of solving the elastic constants of hard and weak rock were described. The damage evolution process, deformation and failure mechanism, and failure mode during uniaxial loading were fully determined. The experimental results show that the θ = 0?–45?specimens had obvious plastic deformation during loading, and the brittleness of the θ = 60?–90?specimens gradually increased during the loading process. When the anisotropic angle θincreased from 0?to 90?, the peak strength, peak strain,and apparent elastic modulus all decreased initially and then increased. The failure mode of the composite rock specimen during uniaxial loading can be divided into three categories:tensile fracture across the discontinuities(θ = 0?–30?), slid-ing failure along the discontinuities(θ = 45?–75?), and tensile-split along the discontinuities(θ = 90?). The axial strain of the weak and hard rock layers in the composite rock specimen during the loading process was significantly different from that of the θ = 0?–45?specimens and was almost the same as that of the θ = 60?–90?specimens. As for the strain localization highlighted in the maximum principal strain field, the θ = 0?–30?specimens appeared in the rock matrix approximately parallel to the loading direction,while in the θ = 45?–90?specimens it appeared at the hard and weak rock layer interface.展开更多
Anchoring mechanism and failure characteristics of composite soft rock with weak interface usually exhibit remarkable difference from those in single rock mass.In order to fully understand the reinforcement mechanism ...Anchoring mechanism and failure characteristics of composite soft rock with weak interface usually exhibit remarkable difference from those in single rock mass.In order to fully understand the reinforcement mechanism of composite soft roof in western mining area of China,a mechanical model of composite soft rock with weak interface and rock bolt which considering the transverse shear sliding between different rock layers was established firstly.The anchoring effect was quantified by a factor defined as anchoring effect coefficient and its evolution equation was further deduced based on the deformation relationship and homogenized distribution assumption of stress acting on composite structure.Meanwhile,the numerical simulation model of composite soft rock with shear joint was prompted by finite element method.Then detailed analysis were carried out for the deformation features,stress distribution and failure behavior of rock mass and rock bolt near the joint under transverse load.The theoretical result indicates that the anchoring effect of rock-bolt through weak joint changes with the working status of rock mass and closely relates with the physical and geometric parameters of rock mass and rock bolt.From the numerical results,the bending deformation of rock bolt accurately characterized by Doseresp model is mainly concentrated between two plastic hinges near the shear joint.The maximum tensile and compression stresses distribute in the plastic hinge.However,the maximum shear stress appears at the positions of joint surface.The failure zones of composite rock are produced firstly at the joint surface due to the reaction of rock bolt.The above results laid a theoretical and computational foundation for further study of anchorage failure in composite soft rock.展开更多
The study concentrates mainly on the development of failure process incomposite rock mass. By use of acoustic emission (AE), convergence inspection, pressure monitoring,level measurement techniques and the modem signa...The study concentrates mainly on the development of failure process incomposite rock mass. By use of acoustic emission (AE), convergence inspection, pressure monitoring,level measurement techniques and the modem signal analysis technology, as well as scan electronmicroscopy (SEM) experiment, various aspects of nonlinear dynamic damage of composite rock masssurrounding the transport roadway in Linglong gold mine are discussed. According to the monitoringresults, the stability of the rock mass can be synthetically evaluated, and the intrinsic relationbetween the damage and the characteristic parameters of acoustic emission can be determined. Thelocation of the damage of rock mass can also be detected based on the acoustic emission couplemonitoring signals. Finally, the key factors which influence the stability of the transport roadwaysupported by composite hard rock materials are found out.展开更多
As one of the most common occurring geological landforms in deep rock formations, the dynamic mechanical properties of layered composite rock bodies under impact loading have been widely studied by scholars. To study ...As one of the most common occurring geological landforms in deep rock formations, the dynamic mechanical properties of layered composite rock bodies under impact loading have been widely studied by scholars. To study the dynamic properties of soft and hard composite rocks with different thickness ratios, this paper utilizes cement, quartz sand and gypsum powder to construct soft and hard composite rock specimens and utilizes a combination of indoor tests, numerical calculations, and theoretical analyses to investigate the mechanical properties of soft and hard composite rock bodies. The test results reveal that:(1) When the proportion of hard rock increases from 20% to 50%, the strength of the combined rock body increases by 69.14 MPa and 87 MPa when the hard rock face and soft rock face are loaded, respectively;however, when the proportion of hard rock is the same, the compressive strength of the hard rock face impact is 9%-17% greater than that of the soft rock face impact;(2) When a specimen of soft and hard combined rock body is subjected to impact loading, the damage mode involves mixed tension and shear damage, and the cracks generally first appear at the ends of the specimen, then develop on the laminar surface from the impact surface, and finally end in the overall damage of the soft rock part. The development rate and the total number of cracks in the same specimen when the hard rock face is impacted are significantly greater than those when the soft rock face is impacted;(3) By introducing Weibull’s statistical strength theory to establish the damage variables of soft-hard combined rock bodies, combined with the DP strength criterion, the damage model and the Kelvin body are concatenated to obtain a statistical damage constitutive model, which can better fit the full stress-strain curve of soft-hard combined rock body specimens under a single impact load.展开更多
The present study is focused on the roadway support in high stress composite soft rock. This paper expounds the two main features of roadway in soft rock, i.e., great deformation of surrounding rock and remarkable rhe...The present study is focused on the roadway support in high stress composite soft rock. This paper expounds the two main features of roadway in soft rock, i.e., great deformation of surrounding rock and remarkable rheological deformation. Furthermore, on the basis of analyzing physico chemical component of surrounding rock and the situation of the damaged roadway, the method of adopting strong bolting and shotcreting mesh for the primary support, bolting and grouting for the secondary support is put forward in light of the on the spot investigation of stress tension, mechanical parameter and engineering geology. The application reveals the method facilitates the continuation of west main roadway and the restoration of shaft station and chambers. Consequently, better techno economic results have been achieved.展开更多
This paper presents results of an experimental study to characterize the law of mineral change of fallen rock in coal mine groundwater reservoir ant its influence on water quality.The minerals of the underground reser...This paper presents results of an experimental study to characterize the law of mineral change of fallen rock in coal mine groundwater reservoir ant its influence on water quality.The minerals of the underground reservoir of Daliuta Coal Mine is taken as the research object.Simulation experiments were designed and conducted to simulate water–rock action in the laboratory.The mineral composition was analyzed by X-ray diffractometer(XRD),the surface morphology of the mineral was analyzed by scanning electron microscope(SEM),and the specific surface area,total pore volume and average pore diameter of the mineral were measured by fast specific surface/pore analyzer(BET).The experimental results show that the sandstone and mudstone in the groundwater reservoir of Daliuta Coal Mine account for 70%and 30%,respectively.The pore diameter is 15.62–17.55 nm,and pore volume is 0.035 cc/g.Its pore structure is a key factor in the occurrence of water–rock interaction.According to the water–rock simulation experiment,the quartz content before the water–rock action is about 34.28%,the albite is about 21.84%,the feldspar is about 17.48%,and the kaolinite is about 8.00%.After the water–rock action,they are 36.14%,17.78%,11.62%,and 16.75%,respectively.The content of albite and orthoclase is reduced while the content of kaolinite is increased,that is,the Na+content becomes higher,and the Ca2+and Mg2+contents become lower.This research builds a good theoretical foundation for revealing the role of water and rock in underground coal reservoirs.展开更多
Acoustic emission and digital image correlation were used to study the spatiotemporal evolution characteristics of crack extension of soft and hard composite laminated rock masses(SHCLRM)containing double fissures und...Acoustic emission and digital image correlation were used to study the spatiotemporal evolution characteristics of crack extension of soft and hard composite laminated rock masses(SHCLRM)containing double fissures under uniaxial compression.The effects of different rock combination methods and prefabricated fissures with different orientations on mechanical properties and crack coalescence patterns were analyzed.The characteristics of the acoustic emission source location distribution,and frequency changes of the crack evolution process were also investigated.The test results show that the damage mode of SHCLRM is related to the combination mode of rock layers and the orientation of fractures.Hard layers predominantly produce tensile cracks;soft layers produce shear cracks.The first crack always sprouts at the tip or middle of prefabricated fractures in hard layers.The acoustic emission signal of SHCLRM with double fractures has clear stage characteristics,and the state of crack development can be inferred from this signal to provide early warning for rock fracture instability.This study can provide a reference for the assessment of the fracture development status between adjacent roadways in SHCLRM in underground mines,as well as in roadway layout and support.展开更多
基金supported by the National Natural Science Foundation of China (grant No.41272170)the National Oil and Gas Major Project (grant No.2016ZX05007-001)
文摘Objective The distribution characteristics and formation mechanism of rearranged hopanes in hydrocarbon source rocks are affected by various geological conditions.Among these geological conditions,thermal action has an important influence on the formation of rearranged hopanes,which has been however little documented previously.
基金Project(242102320036)supported by the Science and the Technology Development Plant of Henan Province,ChinaProject(52278367)supported by the National Natural Science Foundation of China。
文摘Composite rock layers are widely present in mining and tunnel construction projects,and are prone to dynamic tensile failure along bedding planes under dynamic disturbances.To ensure engineering safety,it is necessary to conduct research on the dynamic tensile characteristics under different working conditions.Considering the difficulty of on-site sampling,composite rock samples were prepared with cement mortar,and dynamic Brazilian splitting tests were carried out using split Hopkinson pressure bar(SHPB)equipment,a high-speed camera,and PFC^(2D)numerical software to explore their dynamic tensile properties under dynamic disturbance under different strength ratios and other factors.The results show that the dynamic tensile strength of samples exhibits a rising trend with the strength ratio and strain rate growth.As the incident angle increases from 0°to 90°,the stress contour deflects transform from center-splitting failure to tension-shear combined failure and back again.The influence of the incident order in different lithology rocks on the dynamic tensile strength of composite samples is controlled by strain rate,and when the strain rate increases to 400 s^(-1),the difference in strength due to the sequence of incident stress waves is within 5%.Based on PFC^(2D),the strength ratio of composite samples has a certain influence on the distribution of microfractures.With strength ratios equaling 1.5 or 2.0,the cracks are mainly concentrated on the softer material side,while a large number of cracks are distributed on both sides of the bedding plane with a strength ratio equal to 1.2.
基金financially supported by the National Natural Science Foundation of China(No.52204137)the Outstanding Young Scientific and Technological Talents Project of Liaoning University of Science and Technology(NO.2023YQ10)+3 种基金the Education Department Foundation of Liaoning Province(NO.LJKQZ20222317)the Natural Science Foundation of Shandong Province(Grant No.ZR2020QE121,ZR202211080074)the upport Program for Youth Innovation and Entrepreneurship in Higher Education Institutions of Shandong Province(Grant No.2022KJ101)the Support Program for Youth Innovation and Entrepreneurship in Higher Education Institutions of Shandong Province(Grant No.2022KJ101)。
文摘In rock mass and mining engineering,shock waves induced by engineering disturbances significantly affect rock mass stability.To explore the dynamic mechanical behavior and energy dissipation mechanisms of single-fractured composite rock masses under impact loading,a series of tests were conducted using a split Hopkinson pressure bar(SHPB)system with a 50 mm rod diameter.Specimens containing a single inclined fracture with seven different dip angles and located in different lithological layers were tested.The results show that both peak stress and peak strain exhibit a non-monotonic trend with increasing dip angleα-first decreasing,then increasing,reaching a minimum atα=45°.This behavior is attributed to enhanced energy concentration and dissipation in the fracture zone,where shear-dominated failure leads to more effective crack propagation and stress redistribution.Moreover,the proportion of crushing energy dissipation is significantly affected by the fracture dip angle,reaching a minimum atα=45°and a maximum atα=90°,indicating a transition from shear to tensile failure modes with increasing angle.Lithology also plays a crucial role:grey sandstone specimens absorbed more energy compared to yellow sandstone,implying higher impact resistance due to differences in microstructural cohesion.The evolution of fragment fractal dimension with increasing dip angle follows an"M-shaped"trend,reflecting changes in fragmentation intensity and failure mode.Notably,yellow sandstone tends to produce higher fractal dimensions,with larger mass but smaller volume of powdered debris,indicating more intense fragmentation.This study reveals the coupling effect of fracture dip angle and lithology on dynamic mechanical response and energy evolution,providing new insights into the failure mechanisms of layered composite rock masses under impact loading.
基金supported by the National Natural Science Foundation of China(Nos.52304108,52274148)China University of Mining and Technology-Beijing Undergraduate Innovation Training Program(No.202515011).
文摘Joints are widely distributed structural defects in rock masses,and their geometric characteristics play a decisive role in the overall stability of rocks under complex stress conditions.To clarify the influence of joint geometry on the mechanical behavior of jointed rock under such conditions,this study investigated the mechanical properties and failure mechanisms of composite jointed rock specimens with varying joint roughness and joint dip angles.Three typical failure modes under triaxial loading were identified,and a mechanical analysis model incorporating joint roughness and dip angle was established.The failure mechanism was revealed,and a discrete element model was developed to analyze the micro-damage evolution process of the specimens.The results show that the mechanical parameters of the specimens exhibit pronounced anisotropy.Both the elastic modulus and peak strength reach their minimum values at a joint dip angle of 60°.Increasing joint roughness significantly reduces the degree of anisotropy and enhances the energy storage capacity of the specimens.A strong linear relationship is observed between the elastic strain energy and the peak deviatoric stress,confirming the applicability of the linear energy storage law in composite jointed rocks.Discrete element simulations revealed the evolution path and dominant types of microcracks between the joint and matrix.The joint dip angle governs the transition of dominant crack types from tensile to shear and then back to tensile.Increased joint roughness significantly suppresses damage localization along the joint and results in an approximately 20%increase in the proportion of shear microcracks within the matrix.These findings clarify the regulatory role of joint geometrical parameters in the damage evolution process.
基金financially supported by the National Natural Science Foundation of China(No.51774137)the Natural Science Foundation of Hebei Province,China(No.E2021209006)。
文摘To ensure safe and economical backfill mining,the mechanical response of the backfill–rock interaction system needs to be understood.The numerical investigation of the mechanical behavior of backfill–rock composite structure(BRCS)under triaxial compression,which includes deformation,failure patterns,strength characteristics,and acoustic emission(AE)evolution,was proposed.The models used in the tests have one rough interface,two cement–iron tailings ratios(CTRs),four interface angles(IAs),and three confining pressures(CPs).Results showed that the deformation,strength characteristics,and failure patterns of BRCS under triaxial compression depend on IA,CP,and CTR.The stress–strain curves of BRCS under triaxial compression could be divided into five stages,namely,compaction,elasticity,yield,strain softening,and residual stress.The relevant AE counts have corresponding relationships with different stages.The triaxial compressive strengths of composites increase linearly with the increase of the CP.Furthermore,the CP stress strengthening effect occurs.When the IAs are45°and 60°,the failure areas of composites appear in the interface and backfill.When the IAs are 75°and 90°,the failure areas of composites appear in the backfill,interface,and rock.Moreover,the corresponding failure modes yield the combined shear failure.The research results provide the basis for further understanding of the stability of the BRCS.
基金supported by the National Basic Research 973 Program of China (Grant 2014CB046905)the Natural Science Foundation of Jiangsu Province for Distinguished Young Scholars (Grant BK20150005)+1 种基金the Fundamental Research Funds for the Central Universities (China University of Mining and Technology) (Grant 2014XT03)the innovation research project for academic graduate of Jiangsu Province (Grant KYLX16_0536)
文摘In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic emission technique was used to monitor the acoustic signal characteristics of composite rock specimens during the entire loading process. At the same time, an optical non-contact 3 D digital image correlation technique was used to study the evolution of axial strain field and the maximal strain field before and after the peak strength at different stress levels during the loading process. The effect of bedding plane inclination on the deformation and strength during uniaxial loading was analyzed. The methods of solving the elastic constants of hard and weak rock were described. The damage evolution process, deformation and failure mechanism, and failure mode during uniaxial loading were fully determined. The experimental results show that the θ = 0?–45?specimens had obvious plastic deformation during loading, and the brittleness of the θ = 60?–90?specimens gradually increased during the loading process. When the anisotropic angle θincreased from 0?to 90?, the peak strength, peak strain,and apparent elastic modulus all decreased initially and then increased. The failure mode of the composite rock specimen during uniaxial loading can be divided into three categories:tensile fracture across the discontinuities(θ = 0?–30?), slid-ing failure along the discontinuities(θ = 45?–75?), and tensile-split along the discontinuities(θ = 90?). The axial strain of the weak and hard rock layers in the composite rock specimen during the loading process was significantly different from that of the θ = 0?–45?specimens and was almost the same as that of the θ = 60?–90?specimens. As for the strain localization highlighted in the maximum principal strain field, the θ = 0?–30?specimens appeared in the rock matrix approximately parallel to the loading direction,while in the θ = 45?–90?specimens it appeared at the hard and weak rock layer interface.
基金Projects(51774196,41472280,51578327)supported by the National Natural Science Foundation of ChinaProject(2016M592221)supported by the China Postdoctoral Science FoundationProject(BJRC20160501)supported by the SDUST Young Teachers Teaching Talent Training Plan,China
文摘Anchoring mechanism and failure characteristics of composite soft rock with weak interface usually exhibit remarkable difference from those in single rock mass.In order to fully understand the reinforcement mechanism of composite soft roof in western mining area of China,a mechanical model of composite soft rock with weak interface and rock bolt which considering the transverse shear sliding between different rock layers was established firstly.The anchoring effect was quantified by a factor defined as anchoring effect coefficient and its evolution equation was further deduced based on the deformation relationship and homogenized distribution assumption of stress acting on composite structure.Meanwhile,the numerical simulation model of composite soft rock with shear joint was prompted by finite element method.Then detailed analysis were carried out for the deformation features,stress distribution and failure behavior of rock mass and rock bolt near the joint under transverse load.The theoretical result indicates that the anchoring effect of rock-bolt through weak joint changes with the working status of rock mass and closely relates with the physical and geometric parameters of rock mass and rock bolt.From the numerical results,the bending deformation of rock bolt accurately characterized by Doseresp model is mainly concentrated between two plastic hinges near the shear joint.The maximum tensile and compression stresses distribute in the plastic hinge.However,the maximum shear stress appears at the positions of joint surface.The failure zones of composite rock are produced firstly at the joint surface due to the reaction of rock bolt.The above results laid a theoretical and computational foundation for further study of anchorage failure in composite soft rock.
基金This work was financially supported by the National Natural Science Foundation of China, No.50074002.
文摘The study concentrates mainly on the development of failure process incomposite rock mass. By use of acoustic emission (AE), convergence inspection, pressure monitoring,level measurement techniques and the modem signal analysis technology, as well as scan electronmicroscopy (SEM) experiment, various aspects of nonlinear dynamic damage of composite rock masssurrounding the transport roadway in Linglong gold mine are discussed. According to the monitoringresults, the stability of the rock mass can be synthetically evaluated, and the intrinsic relationbetween the damage and the characteristic parameters of acoustic emission can be determined. Thelocation of the damage of rock mass can also be detected based on the acoustic emission couplemonitoring signals. Finally, the key factors which influence the stability of the transport roadwaysupported by composite hard rock materials are found out.
基金supported by the Xi’an Key Laboratory of Geotechnical and Underground Engineering Open Fund Project (XKLGUEKF20-03)the Natural Science Basic Research Program of Shaanxi Province General Project-Youth Project(2024JC-YBQN-0258)。
文摘As one of the most common occurring geological landforms in deep rock formations, the dynamic mechanical properties of layered composite rock bodies under impact loading have been widely studied by scholars. To study the dynamic properties of soft and hard composite rocks with different thickness ratios, this paper utilizes cement, quartz sand and gypsum powder to construct soft and hard composite rock specimens and utilizes a combination of indoor tests, numerical calculations, and theoretical analyses to investigate the mechanical properties of soft and hard composite rock bodies. The test results reveal that:(1) When the proportion of hard rock increases from 20% to 50%, the strength of the combined rock body increases by 69.14 MPa and 87 MPa when the hard rock face and soft rock face are loaded, respectively;however, when the proportion of hard rock is the same, the compressive strength of the hard rock face impact is 9%-17% greater than that of the soft rock face impact;(2) When a specimen of soft and hard combined rock body is subjected to impact loading, the damage mode involves mixed tension and shear damage, and the cracks generally first appear at the ends of the specimen, then develop on the laminar surface from the impact surface, and finally end in the overall damage of the soft rock part. The development rate and the total number of cracks in the same specimen when the hard rock face is impacted are significantly greater than those when the soft rock face is impacted;(3) By introducing Weibull’s statistical strength theory to establish the damage variables of soft-hard combined rock bodies, combined with the DP strength criterion, the damage model and the Kelvin body are concatenated to obtain a statistical damage constitutive model, which can better fit the full stress-strain curve of soft-hard combined rock body specimens under a single impact load.
文摘The present study is focused on the roadway support in high stress composite soft rock. This paper expounds the two main features of roadway in soft rock, i.e., great deformation of surrounding rock and remarkable rheological deformation. Furthermore, on the basis of analyzing physico chemical component of surrounding rock and the situation of the damaged roadway, the method of adopting strong bolting and shotcreting mesh for the primary support, bolting and grouting for the secondary support is put forward in light of the on the spot investigation of stress tension, mechanical parameter and engineering geology. The application reveals the method facilitates the continuation of west main roadway and the restoration of shaft station and chambers. Consequently, better techno economic results have been achieved.
基金This work was co-supported by the Yue Qi Young Scholar Project,China University of Mining&Technology,Beijing(2019QN08)National Key Research and Development Program of China(2018YFC0406404)+2 种基金Research on Ecological Restoration and Protection of Coal Base in Arid Eco-fragile Region(GJNY2030XDXM-19-03.2)the Fundamental Research Funds for the Central Universities(2020YJSHH12)the scientific and technological innovation project of Shenhua Group(SHJT-16-28).
文摘This paper presents results of an experimental study to characterize the law of mineral change of fallen rock in coal mine groundwater reservoir ant its influence on water quality.The minerals of the underground reservoir of Daliuta Coal Mine is taken as the research object.Simulation experiments were designed and conducted to simulate water–rock action in the laboratory.The mineral composition was analyzed by X-ray diffractometer(XRD),the surface morphology of the mineral was analyzed by scanning electron microscope(SEM),and the specific surface area,total pore volume and average pore diameter of the mineral were measured by fast specific surface/pore analyzer(BET).The experimental results show that the sandstone and mudstone in the groundwater reservoir of Daliuta Coal Mine account for 70%and 30%,respectively.The pore diameter is 15.62–17.55 nm,and pore volume is 0.035 cc/g.Its pore structure is a key factor in the occurrence of water–rock interaction.According to the water–rock simulation experiment,the quartz content before the water–rock action is about 34.28%,the albite is about 21.84%,the feldspar is about 17.48%,and the kaolinite is about 8.00%.After the water–rock action,they are 36.14%,17.78%,11.62%,and 16.75%,respectively.The content of albite and orthoclase is reduced while the content of kaolinite is increased,that is,the Na+content becomes higher,and the Ca2+and Mg2+contents become lower.This research builds a good theoretical foundation for revealing the role of water and rock in underground coal reservoirs.
基金This study was supported by the Natural Science Foundation of Hubei Province(No.2020CFB123)the Scientific Research Program of Hubei Education Department(No.Q20201109).
文摘Acoustic emission and digital image correlation were used to study the spatiotemporal evolution characteristics of crack extension of soft and hard composite laminated rock masses(SHCLRM)containing double fissures under uniaxial compression.The effects of different rock combination methods and prefabricated fissures with different orientations on mechanical properties and crack coalescence patterns were analyzed.The characteristics of the acoustic emission source location distribution,and frequency changes of the crack evolution process were also investigated.The test results show that the damage mode of SHCLRM is related to the combination mode of rock layers and the orientation of fractures.Hard layers predominantly produce tensile cracks;soft layers produce shear cracks.The first crack always sprouts at the tip or middle of prefabricated fractures in hard layers.The acoustic emission signal of SHCLRM with double fractures has clear stage characteristics,and the state of crack development can be inferred from this signal to provide early warning for rock fracture instability.This study can provide a reference for the assessment of the fracture development status between adjacent roadways in SHCLRM in underground mines,as well as in roadway layout and support.
