Steel tube slab (STS) structure, a novel pipe-roof structure, of which steel tubes are connected with flange plates, bolts and concrete, is an increasingly popular supporting structure for underground space developmen...Steel tube slab (STS) structure, a novel pipe-roof structure, of which steel tubes are connected with flange plates, bolts and concrete, is an increasingly popular supporting structure for underground space development. Whilst the load-bearing of pipe-roof structures has been the subject of much research, uncertainties of deformation mechanism and the derivation of reliable calculation methods remain a challenge. For efficient design and wider deployment, this paper presents a bidirectional bending test to investigate the bending stiffnesses, load capacities and deformation mechanisms. The results show that the STS specimens exhibit good ductility and experience bending failure, and their deformation curves follow a half-sine wave upon loading. On this basis, the development of an STS composite slab deformation prediction model is proposed, along with the estimation for its bending stiffness. Theoretical predictions are shown to be in good agreement with the experimental measurements, with a maximum error of less than 15%. The outcomes of this investigation can provide references for the design and application of STS structures.展开更多
This work aims to reveal the mechanical responses and energy evolution characteristics of skarn rock under constant amplitude-varied frequency loading paths.Testing results show that the fatigue lifetime,stress−strain...This work aims to reveal the mechanical responses and energy evolution characteristics of skarn rock under constant amplitude-varied frequency loading paths.Testing results show that the fatigue lifetime,stress−strain responses,deformation,energy dissipation and fracture morphology are all impacted by the loading rate.A pronounced influence of the loading rate on rock deformation is found,with slower loading rate eliciting enhanced strain development,alongside augmented energy absorption and dissipation.In addition,it is revealed that the loading rate and cyclic loading amplitude jointly influence the phase shift distribution,with accelerated rates leading to a narrower phase shift duration.It is suggested that lower loading rate leads to more significant energy dissipation.Finally,the tensile or shear failure modes were intrinsically linked to loading strategy,with cyclic loading predominantly instigating shear damage,as manifest in the increased presence of pulverized grain particles.This work would give new insights into the fortification of mining structures and the optimization of mining methodologies.展开更多
Cemented backfill used in deep mines would inevitably be exposed to the ambient temperature of 20−60℃in the next few decades.In this paper,two types of cemented gravel sand backfills,cemented rod-mill sand backfill(C...Cemented backfill used in deep mines would inevitably be exposed to the ambient temperature of 20−60℃in the next few decades.In this paper,two types of cemented gravel sand backfills,cemented rod-mill sand backfill(CRB)and cemented gobi sand backfill(CGB),were prepared and cured at various temperatures(20,40,60℃)and ages(3,7,28 d),and the effects of temperature and age on the physico-mechanical properties of CRB and CGB were investigated based on laboratory tests.Results show that:1)the effects of temperature and age on the physico-mechanical properties of backfills mainly depend on the amount of hydration products and the refinement of cementation structures.The temperature has a more significant effect on thermal expansibility and ultrasonic performance at early ages.2)The facilitating effect of temperature and age on the compressive strength of CGB is higher than that on CRB.With the increase of temperature,the compressive failure modes changed from X-conjugate shear failure to tensile failure,and the integrity of specimens was significantly improved.3)Similarly,the shear performance of CGB is generally better than that of CRB.The temperature has a weaker effect on shear strength than age,but the shear deformation and shear plane morphology are closely related to temperature.展开更多
In order to study the strength failure and crack coalescence characteristics of cracked rocks, uniaxial compression experiments were conducted on cylindrical sandstone specimens, sampled from Longyou Grottoes of Zheji...In order to study the strength failure and crack coalescence characteristics of cracked rocks, uniaxial compression experiments were conducted on cylindrical sandstone specimens, sampled from Longyou Grottoes of Zhejiang Province, China, with a single pre-cut crack soaking in different chemical solutions. Based on the results of uniaxial compressive test under different chemical solutions and velocities of flow, the effect of strength and deformation characteristics and main modes of crack coalescence for cracked rocks under chemical corrosion were analyzed. The results show that the pH value and velocity of the chemical solutions both have great influence on the sandstone sample's uniaxial compressive strength and deformation characteristics. Cracked sandstone samples are tension-destructed under uniaxial compression, and the crack propagation directions are consistent with the loading direction. The phenomena of crack initiation, propagation and coalescence of sandstone are well observed. Four different crack types are identified based on the crack propagation mechanism by analyzing the ultimate failure modes of sandstone containing a single pre-cut fissure. The failure process of specimen in air is similar with the specimen under chemical solutions, however, the initial time of crack occuring in specimen under chemical solutions is generally earlier than that in the natural specimen, and the crack propagation and coalescence process of specimen under chemical solutions are longer than those of the natural specimen due to softening of structure of rock caused by hydro-chemical action. Immersion velocity of flow and chemical solutions does not have influence on the ultimate modes of crack coalescence.展开更多
A study on the low-cycle fatigue(LCF)behavior of K 416 B alloy was conducted at 650℃.According to the results,the LCF behavior of K 416 B alloy at 650℃ is mainly manifested as elastic deformation and the fatigue lif...A study on the low-cycle fatigue(LCF)behavior of K 416 B alloy was conducted at 650℃.According to the results,the LCF behavior of K 416 B alloy at 650℃ is mainly manifested as elastic deformation and the fatigue life of the alloy is determined by the level of material strength.When tension-compression fatigue occurs,the deformation mechanism of the alloy is reflected in the form of dislocation slip,and the deformation dislocations are bowed out in the matrix by Orowan mechanism,which leads to a dislocation configuration similar to the Frawk-Reed source.At the late stage of low-cycle fatigue,the fatigue-induced cracks develop from the alloy surface.As fatigue test proceeds,it is possible for the cracks to continue development along the regions of eutectic and the bulk M 6 C carbide due to stress concentration,thus causing the alloy to show cleavage fracture.展开更多
基金Project(BK20210721) supported by the Natural Science Foundation of Jiangsu Province,ChinaProjects(52108380,52078506) supported by the National Natural Science Foundation of ChinaProject(2023A1515012159) supported by the Guangdong Basic and Applied Basic Research Foundation,China。
文摘Steel tube slab (STS) structure, a novel pipe-roof structure, of which steel tubes are connected with flange plates, bolts and concrete, is an increasingly popular supporting structure for underground space development. Whilst the load-bearing of pipe-roof structures has been the subject of much research, uncertainties of deformation mechanism and the derivation of reliable calculation methods remain a challenge. For efficient design and wider deployment, this paper presents a bidirectional bending test to investigate the bending stiffnesses, load capacities and deformation mechanisms. The results show that the STS specimens exhibit good ductility and experience bending failure, and their deformation curves follow a half-sine wave upon loading. On this basis, the development of an STS composite slab deformation prediction model is proposed, along with the estimation for its bending stiffness. Theoretical predictions are shown to be in good agreement with the experimental measurements, with a maximum error of less than 15%. The outcomes of this investigation can provide references for the design and application of STS structures.
基金Project(52174069) supported by the National Natural Science Foundation of ChinaProject(8202033) supported by the Beijing Natural Science Foundation,ChinaProject(KCF2203) supported by the Henan Key Laboratory for Green and Efficient Mining&Comprehensive Utilization of Mineral Resources (Henan Polytechnic University),China。
文摘This work aims to reveal the mechanical responses and energy evolution characteristics of skarn rock under constant amplitude-varied frequency loading paths.Testing results show that the fatigue lifetime,stress−strain responses,deformation,energy dissipation and fracture morphology are all impacted by the loading rate.A pronounced influence of the loading rate on rock deformation is found,with slower loading rate eliciting enhanced strain development,alongside augmented energy absorption and dissipation.In addition,it is revealed that the loading rate and cyclic loading amplitude jointly influence the phase shift distribution,with accelerated rates leading to a narrower phase shift duration.It is suggested that lower loading rate leads to more significant energy dissipation.Finally,the tensile or shear failure modes were intrinsically linked to loading strategy,with cyclic loading predominantly instigating shear damage,as manifest in the increased presence of pulverized grain particles.This work would give new insights into the fortification of mining structures and the optimization of mining methodologies.
基金Project(P2018G045)supported by the Science&Technology Research and Development Program of China RailwayProject(2018CFA013)supported by the Hubei Provincial Natural Science Foundation Innovation Group,China+1 种基金Project(KFJ-STS-QYZD-174)supported by the Science and Technology Service Network Initiative of the Chinese Academy of SciencesProject(51709257)supported by the National Natural Science Foundation of China。
文摘Cemented backfill used in deep mines would inevitably be exposed to the ambient temperature of 20−60℃in the next few decades.In this paper,two types of cemented gravel sand backfills,cemented rod-mill sand backfill(CRB)and cemented gobi sand backfill(CGB),were prepared and cured at various temperatures(20,40,60℃)and ages(3,7,28 d),and the effects of temperature and age on the physico-mechanical properties of CRB and CGB were investigated based on laboratory tests.Results show that:1)the effects of temperature and age on the physico-mechanical properties of backfills mainly depend on the amount of hydration products and the refinement of cementation structures.The temperature has a more significant effect on thermal expansibility and ultrasonic performance at early ages.2)The facilitating effect of temperature and age on the compressive strength of CGB is higher than that on CRB.With the increase of temperature,the compressive failure modes changed from X-conjugate shear failure to tensile failure,and the integrity of specimens was significantly improved.3)Similarly,the shear performance of CGB is generally better than that of CRB.The temperature has a weaker effect on shear strength than age,but the shear deformation and shear plane morphology are closely related to temperature.
基金Projects(10472130,41202225) supported by the National Natural Science Foundation of China
文摘In order to study the strength failure and crack coalescence characteristics of cracked rocks, uniaxial compression experiments were conducted on cylindrical sandstone specimens, sampled from Longyou Grottoes of Zhejiang Province, China, with a single pre-cut crack soaking in different chemical solutions. Based on the results of uniaxial compressive test under different chemical solutions and velocities of flow, the effect of strength and deformation characteristics and main modes of crack coalescence for cracked rocks under chemical corrosion were analyzed. The results show that the pH value and velocity of the chemical solutions both have great influence on the sandstone sample's uniaxial compressive strength and deformation characteristics. Cracked sandstone samples are tension-destructed under uniaxial compression, and the crack propagation directions are consistent with the loading direction. The phenomena of crack initiation, propagation and coalescence of sandstone are well observed. Four different crack types are identified based on the crack propagation mechanism by analyzing the ultimate failure modes of sandstone containing a single pre-cut fissure. The failure process of specimen in air is similar with the specimen under chemical solutions, however, the initial time of crack occuring in specimen under chemical solutions is generally earlier than that in the natural specimen, and the crack propagation and coalescence process of specimen under chemical solutions are longer than those of the natural specimen due to softening of structure of rock caused by hydro-chemical action. Immersion velocity of flow and chemical solutions does not have influence on the ultimate modes of crack coalescence.
基金Projects(51701212,51771191,51971214)supported by the National Natural Science Foundation of ChinaProject(2019-MS-336)supported by the Liaoning Provincial Natural Science Foundation,China。
文摘A study on the low-cycle fatigue(LCF)behavior of K 416 B alloy was conducted at 650℃.According to the results,the LCF behavior of K 416 B alloy at 650℃ is mainly manifested as elastic deformation and the fatigue life of the alloy is determined by the level of material strength.When tension-compression fatigue occurs,the deformation mechanism of the alloy is reflected in the form of dislocation slip,and the deformation dislocations are bowed out in the matrix by Orowan mechanism,which leads to a dislocation configuration similar to the Frawk-Reed source.At the late stage of low-cycle fatigue,the fatigue-induced cracks develop from the alloy surface.As fatigue test proceeds,it is possible for the cracks to continue development along the regions of eutectic and the bulk M 6 C carbide due to stress concentration,thus causing the alloy to show cleavage fracture.
