Quasi-NPR(negative Poisson’s ratio)steel is a new type of super bolt material with high strength,high ductility,and a micro-negative Poisson’s effect.This material overcomes the contrasting characteristics of the hi...Quasi-NPR(negative Poisson’s ratio)steel is a new type of super bolt material with high strength,high ductility,and a micro-negative Poisson’s effect.This material overcomes the contrasting characteristics of the high strength and high ductility of steel and it has significant energy-absorbing characteristics,which is of high value in deep rock and soil support engineering.However,research on the shear resistance of quasi-NPR steel has not been carried out.To study the shear performance of quasi-NPR steel bolted rock joints,indoor shear tests of bolted rock joints under different normal stress conditions were carried out.Q235 steel and#45 steel,two representative ordinary bolt steels,were set up as a control group for comparative tests to compare and analyze the shear strength,deformation and instability mode,shear energy absorption characteristics,and bolting contribution of different types of bolts.The results show that the jointed rock masses without bolt reinforcement undergo brittle failure under shear load,while the bolted jointed rock masses show obvious ductile failure characteristics.The shear deformation ca-pacity of quasi-NPR steel is more than 3.5 times that of Q235 steel and#45 steel.No fracture occurs in the quasi-NPR steel during large shear deformation and it can provide stable shear resistance.However,the other two types of control bolts become fractured under the same conditions.Quasi-NPR steel has significant energy-absorbing characteristics under shear load and has obvious advantages in terms of absorbing the energy released by shear deformation of jointed rock masses as compared with ordinary steel.In particular,the shear force plays a major role in resisting the shear deformation of Q235 steel and#45 steel,therefore,fracture failure occurs under small bolt deformation.However,the axial force of quasi-NPR steel can be fully exerted when resisting joint shear deformation;the steel itself does not break when large shear deformation occurs,and the supporting effect of the jointed rock mass is effectively guaranteed.展开更多
2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock ...2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock mass and controlling the stability of surrounding rock. To achieve an accurate simulation of bolted joint shear tests, we have studied a numerical simulation method that takes into account the 2G-NPR bolt's tensile–shear fracture criterion. Firstly, the indoor experimental study on the tensile–shear mechanical properties of 2G-NPR bolt is carried out to explore its mechanical properties under diferent tensile–shear angles, and the fracture criterion of 2G-NPR bolt considering the tensile–shear angle is established. Then, a three-dimensional numerical simulation method considering the tensile–shear mechanical constitutive and fracture criterion of 2G-NPR bolt, the elastoplastic mechanical behavior of surrounding rock and the damage and deterioration of grouting body is proposed. The feasibility and accuracy of the method are verifed by comparing with the indoor shear test results of 2G-NPR bolt anchorage joints. Finally, based on the numerical simulation results, the deformation and stress of the bolt, the distribution of the plastic zone of the rock mass, the stress distribution and the damage of the grouting body are analyzed in detail. The research results can provide a good reference value for the practical engineering application and shear mechanical performance analysis of 2G-NPR bolt.展开更多
Shearing behavior and failure mechanism of bolt-grout interface are of great significance for load transfer capacity and design of rock bolting system.In this paper,direct shear tests on bolt-grout interfaces under co...Shearing behavior and failure mechanism of bolt-grout interface are of great significance for load transfer capacity and design of rock bolting system.In this paper,direct shear tests on bolt-grout interfaces under constant normal load(CNL) conditions were conducted to investigate the effects of bolt profile(i.e.rib spacing and rib height) and grout mixture on the bolt-grout interface in terms of mechanical behaviors and failure modes.Test results showed that the peak shear strength and the deformation capacity of the bolt-grout interface are highly dependent on the bolt profile and grout mixture,suggesting that bolt performances can be optimized,which were unfortunately ignored in the previous studies.A new interface failure mode,i.e.'sheared-crush' mode,was proposed,which was characterized by progressive crush failure of the grout asperities between steel ribs during shearing.It was shown that the interface failure mode mainly depends on the normal stress level and rib spacing,compared with the rib height and grout mixture for the range of tested parameters in this study.展开更多
A Double Shear Model(DSM) was used in a numerical simulation on bolted rock joint shearing performance.An entire bolt deformed as the letter'U'under a shear load between two joints.Near the bolt-joint intersec...A Double Shear Model(DSM) was used in a numerical simulation on bolted rock joint shearing performance.An entire bolt deformed as the letter'U'under a shear load between two joints.Near the bolt-joint intersection,the bolt partly deformed as the letter'Z'.There were two critical points along the bolt:one was at the bolt-joint intersection with zero bending moment and the other at the maximum bending moment(plastic hinge) with zero shear stress.The blocks on two sides slid along the bolt as it deformed. A separation area was found between the two joint contact surfaces of the middle rock block and sided block.This area of separation was related to bolt diameter and external forces.We assume that this area is related to the work of external forces.Further research is needed.展开更多
Rock bolts have been widely used for stabilizing rock mass in geotechnical engineering.It is acknowledged that the bolt profiles have a sound influence on the support effect of the rock bolting system.Previous studies...Rock bolts have been widely used for stabilizing rock mass in geotechnical engineering.It is acknowledged that the bolt profiles have a sound influence on the support effect of the rock bolting system.Previous studies have proposed some optimal rib parameters(e.g.rib spacing);unfortunately,the interface shear behaviors are generally ignored.Therefore,determination of radial stress and radial displacement on the bolt-grout interface using traditional pull-out tests is not possible.The load-bearing capacity and deformation capacity vary as bolt profiles differ,suggesting that the support effect of the bolting system can be enhanced by optimizing bolt profiles.The aim of this study is to investigate the effects of bolt profiles(with/without ribs,rib spacing,and rib height)on the shear behaviors between the rock bolt and grout material using direct shear tests.Thereby,systematic interfacial shear tests with different bolt profiles were performed under both constant normal load(CNL)and constant normal stiffness(CNS)boundary conditions.The results suggested that rib spacing has a more marked influence on the interface shear behavior than rib height does,in particular at the post-yield stage.The results could facilitate our understanding of bolt-grout interface shear behavior under CNS conditions,and optimize selection of rock bolts under in situ rock conditions.展开更多
The bolt anchoring force is closely related to the shear properties of the anchor interface. The shear stress distribution of full-length grouted bolts is analyzed based on the stress-strain relationship among the bol...The bolt anchoring force is closely related to the shear properties of the anchor interface. The shear stress distribution of full-length grouted bolts is analyzed based on the stress-strain relationship among the bolt, grout, rock mass and bond interface,considering the shear properties of the grout and contact interface bonding behavior. In this case, the interfacial shear stress of the grout and rock mass and the bolt axial force are obtained under pull-out and normal working conditions. The results show that the peak shear stress of the interface with the shear deformation of the bond interface is significantly lower than that without it when the pull-out force is applied. When designing bolt parameters of grade IV and V rock mass, the relative deformation between the rock mass and anchor should be considered, with a “unimodal” to “bimodal” shear stress distribution.In the case of a low elastic modulus of rock masses,both the shear stress concentration and distribution range are obvious, and the neutral point is near the bolt head. As the elastic modulus increases, the shear stress concentration and distribution range are reduced, and the neutral point moves towards the distal end. As a result, the optimum length of fulllength grouted bolts can be determined by in-situ pull-out tests and decreases with the increased elastic modulus of the rock mass.展开更多
In presence of difficult conditions in coal mining roadways, an adequate stabilization of the excavation boundary is required to ensure a safe progress of the construction. The stabilization of the roadways can be imp...In presence of difficult conditions in coal mining roadways, an adequate stabilization of the excavation boundary is required to ensure a safe progress of the construction. The stabilization of the roadways can be improved by fully grouted rock bolt, offering properties optimal to the purpose and versatility in use. Investigations of load transfer between the bolt and grout indicate that the bolt profile shape and spacing play an important role in improving the shear strength between the bolt and the surrounding strata. This study proposes a new analytical solution for calculation displacement and shear stress in a fully encapsulated rock bolt in jointed rocks. The main characteristics of the analytical solution consider the bolt profile and jump plane under pull test conditions. The performance of the proposed analytical solution, for three types of different bolt profile configurations, is validated by ANSYS software. The results show there is a good agreement between analytical and numerical methods. Studies indicate that the rate of displacement and shear stress from the bolt to the rock exponentially decayed. This exponential reduction in displacement and shear stress are dependent on the bolt characteristics such as: rib height, rib spacing, rib width and grout thickness, material and joint properties.展开更多
In deep ground engineering,the use of high-strength and high-toughness steels for rock bolt can significantly improve its energy absorption capacity.However,the mechanisms and effects of rock loading conditions on thi...In deep ground engineering,the use of high-strength and high-toughness steels for rock bolt can significantly improve its energy absorption capacity.However,the mechanisms and effects of rock loading conditions on this kind of high energy-absorbing steel for rock bolt remain immature.In this study,taking Muzhailing highway tunnel as the background,physically based crystal plasticity simulations were performed to understand the effect of rock loading rate and pretension on the deformation behaviors of twinning induced plasticity(TWIP)steel used for rock bolt.The material physical connecting to the underlying microscopic mechanisms of dislocation glide and deformation twinning were incorporated in numerical modeling.The rock loading conditions were mimicked by the real-time field monitoring data of the NPR bolt/cable equipment installed on the tunnel surrounding rock surface.The results indicate that the bolt rod exhibits pronounced deformation-softening behavior with decrease of the loading rate.There is also a sound deformation-relaxation phenomenon induced by the dramatic decrease of loading rate after pre-tensioning.The high pretension(>600 MPa or 224 k N)can help bolt rod steel resist deformation-softening behavior,especially at low loading rate(<10~(-1)MPa/s or 10~(-2)kN/s).The loading rate was found to be a significant factor affecting deformation-softening behavior while the pretension was found to be the major parameter accounting for the deformation-relaxation scenario.The results provide the theoretical basis and technical support for practical applications.展开更多
Presented a new analytical model for studying the shear-tensile large deforma-tion behavior near the vicinity of joint interface for bolted rough discontinuous rock, and presented the formulation estimating global she...Presented a new analytical model for studying the shear-tensile large deforma-tion behavior near the vicinity of joint interface for bolted rough discontinuous rock, and presented the formulation estimating global shear strength for bolted joints under shear-ing-tensile loads. The analytical strength curves of bolts contribution on reinforced discon-tinuous rocks as the function of joint displacements or deformation angle of a bolt at rock joints was obtained. Based on Barton’s equation on JRC roughness profiles, the theoreti-cal shearing strength of bolted rough joints was also established. Test results on bolted granite and marble specimen confirm the validity of the analytical approach.展开更多
In this study,an experimental study and numerical calculations using fiber model were conducted for four high-strength concrete shear walls with boundary columns under low cyclic load.The boundary column and shear wal...In this study,an experimental study and numerical calculations using fiber model were conducted for four high-strength concrete shear walls with boundary columns under low cyclic load.The boundary column and shear wall were divided into fiber elements,and PERFORM-3D finite element analysis software was used to carry out push-over analysis on the test specimens.The results show that the finite element analysis results were in good agreement with the experimental results.The proposed analysis method could perform elasto-plastic analysis on the high-strength concrete shear wall with boundary columns without distinguishing the categories of frame column and shear wall.The seismic performance of high-strength concrete shear wall with boundary columns was analyzed using the following parameters:axis compression ratio,height to width ratio,ratio of vertical reinforcement,and ratio of longitudinal reinforcement in the boundary column.The results show that the increase in the axial compression ratio causes the bearing capacity of the shear wall to increase at first and then to decrease and causes the ductility to decrease.The increase in the height to width ratio causes the bearing capacity of the shear wall to decrease and its ductility to increase.The ratio of vertical reinforcement was found to have little effect on the bearing capacity and ductility.The increase in the ratio of longitudinal reinforcement in boundary column resulted in a significant increase in the bearing capacity and caused the ductility to decrease at first and then to slowly increase.展开更多
The high-strength bolted end plate connection is widely used in the construction industry with its green environmental protection and excellent seismic performance. The joints of the joints are semi-rigid, the force p...The high-strength bolted end plate connection is widely used in the construction industry with its green environmental protection and excellent seismic performance. The joints of the joints are semi-rigid, the force performance is extremely complicated, and the experimental research cost is relatively high, and the cycle is very long. Therefore, the establishment of an efficient numerical model is of great significance for evaluating the force performance of high-strength bolt end plates. In this paper, the influence of different material models on the rotation performance of the joint is studied by numerical simulation, and the bending moment-rotation curve is obtained. The numerical simulation and the experimental results are in good agreement, so as to provide a reference for the design and application of this kind of joint.展开更多
In underground coal mines, fibre reinforced polymer(FRP) bolt is ideal for mined rib reinforcements as it can prevent gas explosions caused by shearer frictional spark. With increasing mining depth, small diameter FRP...In underground coal mines, fibre reinforced polymer(FRP) bolt is ideal for mined rib reinforcements as it can prevent gas explosions caused by shearer frictional spark. With increasing mining depth, small diameter FRP bolts used in shallow underground mining cannot fulfil the rib support requirements. Under the engineering background of deep underground shortwall mining in Wudong coal mine, this paper systematically studies Φ27 mm FRP bolt support for large deformation coal rib. Specimens with a fan-shaped cross-section were used to enable the tensile testing of the bolt rod, the measured average tensile strength of the studied FRP bolt was(486.1 ± 9.6) MPa with a maximum elongation of 5.7%±0.6%.The shear strength of the bolt was measured as approximately 258 MPa using a self-made double shear testing apparatus. Based on the equivalent radial stiffness principle, a laboratory short encapsulation pullout test(SEPT) method for rib bolting has been developed undertaken consideration of the mechanical properties of the coal seam. Results showed that the average peak anchorage forces of the Φ27 mm FRP bolt and Φ20 mm steel rebar bolt were 108.4 and 66.4 k N, respectively, which were agreed with the theoretical calculations and field measurements. Based on theoretical analysis of the loading states of the bolt under site conditions, bolting method of full-length resin grouting was adopted to offset the weaknesses of the FRP bolt. Numerical method was employed to compare the bolting effect using Φ27 mm FRP bolts and steel rebar bolts. Large diameter FRP bolting was determined as the optimum rib support scheme to increase the productivity of the coal mine and to enhance the ground control capability for+425 level mining roadways. This study provides the laboratory testing design and theoretical prediction of large diameter FRP bolts used for rib support in large deformation roadways.展开更多
基金This study has been funded by the National Natural Science Foundation of China(Grant No.41941018)and the Second Tibetan Plateau Scientific Expedition and Research Grant(Grant No.2019QZKK0708).
文摘Quasi-NPR(negative Poisson’s ratio)steel is a new type of super bolt material with high strength,high ductility,and a micro-negative Poisson’s effect.This material overcomes the contrasting characteristics of the high strength and high ductility of steel and it has significant energy-absorbing characteristics,which is of high value in deep rock and soil support engineering.However,research on the shear resistance of quasi-NPR steel has not been carried out.To study the shear performance of quasi-NPR steel bolted rock joints,indoor shear tests of bolted rock joints under different normal stress conditions were carried out.Q235 steel and#45 steel,two representative ordinary bolt steels,were set up as a control group for comparative tests to compare and analyze the shear strength,deformation and instability mode,shear energy absorption characteristics,and bolting contribution of different types of bolts.The results show that the jointed rock masses without bolt reinforcement undergo brittle failure under shear load,while the bolted jointed rock masses show obvious ductile failure characteristics.The shear deformation ca-pacity of quasi-NPR steel is more than 3.5 times that of Q235 steel and#45 steel.No fracture occurs in the quasi-NPR steel during large shear deformation and it can provide stable shear resistance.However,the other two types of control bolts become fractured under the same conditions.Quasi-NPR steel has significant energy-absorbing characteristics under shear load and has obvious advantages in terms of absorbing the energy released by shear deformation of jointed rock masses as compared with ordinary steel.In particular,the shear force plays a major role in resisting the shear deformation of Q235 steel and#45 steel,therefore,fracture failure occurs under small bolt deformation.However,the axial force of quasi-NPR steel can be fully exerted when resisting joint shear deformation;the steel itself does not break when large shear deformation occurs,and the supporting effect of the jointed rock mass is effectively guaranteed.
基金supported by the National Natural Science Foundation of China(NSFC)(41941018).
文摘2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock mass and controlling the stability of surrounding rock. To achieve an accurate simulation of bolted joint shear tests, we have studied a numerical simulation method that takes into account the 2G-NPR bolt's tensile–shear fracture criterion. Firstly, the indoor experimental study on the tensile–shear mechanical properties of 2G-NPR bolt is carried out to explore its mechanical properties under diferent tensile–shear angles, and the fracture criterion of 2G-NPR bolt considering the tensile–shear angle is established. Then, a three-dimensional numerical simulation method considering the tensile–shear mechanical constitutive and fracture criterion of 2G-NPR bolt, the elastoplastic mechanical behavior of surrounding rock and the damage and deterioration of grouting body is proposed. The feasibility and accuracy of the method are verifed by comparing with the indoor shear test results of 2G-NPR bolt anchorage joints. Finally, based on the numerical simulation results, the deformation and stress of the bolt, the distribution of the plastic zone of the rock mass, the stress distribution and the damage of the grouting body are analyzed in detail. The research results can provide a good reference value for the practical engineering application and shear mechanical performance analysis of 2G-NPR bolt.
基金supported by the Key Projects of the Yalong River Joint Fund of the National Natural Science Foundation of China(Grant No.U1865203)the National Natural Science Foundation of China(Grant No.51279201)+1 种基金Special project of the National Natural Science Foundation of China(Grant No.41941018)The partial support from the Youth Innovation Promotion Association,Chinese Academy of Sciences。
文摘Shearing behavior and failure mechanism of bolt-grout interface are of great significance for load transfer capacity and design of rock bolting system.In this paper,direct shear tests on bolt-grout interfaces under constant normal load(CNL) conditions were conducted to investigate the effects of bolt profile(i.e.rib spacing and rib height) and grout mixture on the bolt-grout interface in terms of mechanical behaviors and failure modes.Test results showed that the peak shear strength and the deformation capacity of the bolt-grout interface are highly dependent on the bolt profile and grout mixture,suggesting that bolt performances can be optimized,which were unfortunately ignored in the previous studies.A new interface failure mode,i.e.'sheared-crush' mode,was proposed,which was characterized by progressive crush failure of the grout asperities between steel ribs during shearing.It was shown that the interface failure mode mainly depends on the normal stress level and rib spacing,compared with the rib height and grout mixture for the range of tested parameters in this study.
基金Financial support from the National Natural Science Foundation of China(No.50978251)the National Government Building High-Level University Graduate Programs of the China Scholarship Council
文摘A Double Shear Model(DSM) was used in a numerical simulation on bolted rock joint shearing performance.An entire bolt deformed as the letter'U'under a shear load between two joints.Near the bolt-joint intersection,the bolt partly deformed as the letter'Z'.There were two critical points along the bolt:one was at the bolt-joint intersection with zero bending moment and the other at the maximum bending moment(plastic hinge) with zero shear stress.The blocks on two sides slid along the bolt as it deformed. A separation area was found between the two joint contact surfaces of the middle rock block and sided block.This area of separation was related to bolt diameter and external forces.We assume that this area is related to the work of external forces.Further research is needed.
基金This study is supported by the key projects of the Yalong River Joint Fund of the National Natural Science Foundation of China(Grant No.U1865203)the National Key Research and Development Program of China(Grant Nos.2019YFC0605103,2019YFC0605100)the National Natural Science Foundation of China(Grant No.51279201).The partial support from the Youth Innovation Promotion Association CAS is gratefully acknowledged。
文摘Rock bolts have been widely used for stabilizing rock mass in geotechnical engineering.It is acknowledged that the bolt profiles have a sound influence on the support effect of the rock bolting system.Previous studies have proposed some optimal rib parameters(e.g.rib spacing);unfortunately,the interface shear behaviors are generally ignored.Therefore,determination of radial stress and radial displacement on the bolt-grout interface using traditional pull-out tests is not possible.The load-bearing capacity and deformation capacity vary as bolt profiles differ,suggesting that the support effect of the bolting system can be enhanced by optimizing bolt profiles.The aim of this study is to investigate the effects of bolt profiles(with/without ribs,rib spacing,and rib height)on the shear behaviors between the rock bolt and grout material using direct shear tests.Thereby,systematic interfacial shear tests with different bolt profiles were performed under both constant normal load(CNL)and constant normal stiffness(CNS)boundary conditions.The results suggested that rib spacing has a more marked influence on the interface shear behavior than rib height does,in particular at the post-yield stage.The results could facilitate our understanding of bolt-grout interface shear behavior under CNS conditions,and optimize selection of rock bolts under in situ rock conditions.
基金funded by the Natural Science Foundation of China(Grants Nos.52179113,42207199,41831278)。
文摘The bolt anchoring force is closely related to the shear properties of the anchor interface. The shear stress distribution of full-length grouted bolts is analyzed based on the stress-strain relationship among the bolt, grout, rock mass and bond interface,considering the shear properties of the grout and contact interface bonding behavior. In this case, the interfacial shear stress of the grout and rock mass and the bolt axial force are obtained under pull-out and normal working conditions. The results show that the peak shear stress of the interface with the shear deformation of the bond interface is significantly lower than that without it when the pull-out force is applied. When designing bolt parameters of grade IV and V rock mass, the relative deformation between the rock mass and anchor should be considered, with a “unimodal” to “bimodal” shear stress distribution.In the case of a low elastic modulus of rock masses,both the shear stress concentration and distribution range are obvious, and the neutral point is near the bolt head. As the elastic modulus increases, the shear stress concentration and distribution range are reduced, and the neutral point moves towards the distal end. As a result, the optimum length of fulllength grouted bolts can be determined by in-situ pull-out tests and decreases with the increased elastic modulus of the rock mass.
文摘In presence of difficult conditions in coal mining roadways, an adequate stabilization of the excavation boundary is required to ensure a safe progress of the construction. The stabilization of the roadways can be improved by fully grouted rock bolt, offering properties optimal to the purpose and versatility in use. Investigations of load transfer between the bolt and grout indicate that the bolt profile shape and spacing play an important role in improving the shear strength between the bolt and the surrounding strata. This study proposes a new analytical solution for calculation displacement and shear stress in a fully encapsulated rock bolt in jointed rocks. The main characteristics of the analytical solution consider the bolt profile and jump plane under pull test conditions. The performance of the proposed analytical solution, for three types of different bolt profile configurations, is validated by ANSYS software. The results show there is a good agreement between analytical and numerical methods. Studies indicate that the rate of displacement and shear stress from the bolt to the rock exponentially decayed. This exponential reduction in displacement and shear stress are dependent on the bolt characteristics such as: rib height, rib spacing, rib width and grout thickness, material and joint properties.
基金the National Natural Science Foundation of China(Grant No.41941018)the Science and Technology Major Project of Gansu Province(Grant No.19ZD2GA005)the Research Institute for Deep Underground Science and Engineering Foundation(Grant No.XD2021023)。
文摘In deep ground engineering,the use of high-strength and high-toughness steels for rock bolt can significantly improve its energy absorption capacity.However,the mechanisms and effects of rock loading conditions on this kind of high energy-absorbing steel for rock bolt remain immature.In this study,taking Muzhailing highway tunnel as the background,physically based crystal plasticity simulations were performed to understand the effect of rock loading rate and pretension on the deformation behaviors of twinning induced plasticity(TWIP)steel used for rock bolt.The material physical connecting to the underlying microscopic mechanisms of dislocation glide and deformation twinning were incorporated in numerical modeling.The rock loading conditions were mimicked by the real-time field monitoring data of the NPR bolt/cable equipment installed on the tunnel surrounding rock surface.The results indicate that the bolt rod exhibits pronounced deformation-softening behavior with decrease of the loading rate.There is also a sound deformation-relaxation phenomenon induced by the dramatic decrease of loading rate after pre-tensioning.The high pretension(>600 MPa or 224 k N)can help bolt rod steel resist deformation-softening behavior,especially at low loading rate(<10~(-1)MPa/s or 10~(-2)kN/s).The loading rate was found to be a significant factor affecting deformation-softening behavior while the pretension was found to be the major parameter accounting for the deformation-relaxation scenario.The results provide the theoretical basis and technical support for practical applications.
基金Supported by National Nature Science Foundation of China(50304012)the "973" Program of China(2002CB412701)
文摘Presented a new analytical model for studying the shear-tensile large deforma-tion behavior near the vicinity of joint interface for bolted rough discontinuous rock, and presented the formulation estimating global shear strength for bolted joints under shear-ing-tensile loads. The analytical strength curves of bolts contribution on reinforced discon-tinuous rocks as the function of joint displacements or deformation angle of a bolt at rock joints was obtained. Based on Barton’s equation on JRC roughness profiles, the theoreti-cal shearing strength of bolted rough joints was also established. Test results on bolted granite and marble specimen confirm the validity of the analytical approach.
基金supported by the National Natural Science Foundation of China(No.51708209)Hunan Provincial Natural Science Foundation of China(No.2019JJ50209)National Student‘s Program for Innovation and Entrepreneurship(No.201912658001)。
文摘In this study,an experimental study and numerical calculations using fiber model were conducted for four high-strength concrete shear walls with boundary columns under low cyclic load.The boundary column and shear wall were divided into fiber elements,and PERFORM-3D finite element analysis software was used to carry out push-over analysis on the test specimens.The results show that the finite element analysis results were in good agreement with the experimental results.The proposed analysis method could perform elasto-plastic analysis on the high-strength concrete shear wall with boundary columns without distinguishing the categories of frame column and shear wall.The seismic performance of high-strength concrete shear wall with boundary columns was analyzed using the following parameters:axis compression ratio,height to width ratio,ratio of vertical reinforcement,and ratio of longitudinal reinforcement in the boundary column.The results show that the increase in the axial compression ratio causes the bearing capacity of the shear wall to increase at first and then to decrease and causes the ductility to decrease.The increase in the height to width ratio causes the bearing capacity of the shear wall to decrease and its ductility to increase.The ratio of vertical reinforcement was found to have little effect on the bearing capacity and ductility.The increase in the ratio of longitudinal reinforcement in boundary column resulted in a significant increase in the bearing capacity and caused the ductility to decrease at first and then to slowly increase.
文摘The high-strength bolted end plate connection is widely used in the construction industry with its green environmental protection and excellent seismic performance. The joints of the joints are semi-rigid, the force performance is extremely complicated, and the experimental research cost is relatively high, and the cycle is very long. Therefore, the establishment of an efficient numerical model is of great significance for evaluating the force performance of high-strength bolt end plates. In this paper, the influence of different material models on the rotation performance of the joint is studied by numerical simulation, and the bending moment-rotation curve is obtained. The numerical simulation and the experimental results are in good agreement, so as to provide a reference for the design and application of this kind of joint.
基金The work presented in this paper was financially jointly supported by General Project of the National Natural Science Foundation of China(No.52074145)Liaoning Revitalization Talents Program(No.XLYC2002110).
文摘In underground coal mines, fibre reinforced polymer(FRP) bolt is ideal for mined rib reinforcements as it can prevent gas explosions caused by shearer frictional spark. With increasing mining depth, small diameter FRP bolts used in shallow underground mining cannot fulfil the rib support requirements. Under the engineering background of deep underground shortwall mining in Wudong coal mine, this paper systematically studies Φ27 mm FRP bolt support for large deformation coal rib. Specimens with a fan-shaped cross-section were used to enable the tensile testing of the bolt rod, the measured average tensile strength of the studied FRP bolt was(486.1 ± 9.6) MPa with a maximum elongation of 5.7%±0.6%.The shear strength of the bolt was measured as approximately 258 MPa using a self-made double shear testing apparatus. Based on the equivalent radial stiffness principle, a laboratory short encapsulation pullout test(SEPT) method for rib bolting has been developed undertaken consideration of the mechanical properties of the coal seam. Results showed that the average peak anchorage forces of the Φ27 mm FRP bolt and Φ20 mm steel rebar bolt were 108.4 and 66.4 k N, respectively, which were agreed with the theoretical calculations and field measurements. Based on theoretical analysis of the loading states of the bolt under site conditions, bolting method of full-length resin grouting was adopted to offset the weaknesses of the FRP bolt. Numerical method was employed to compare the bolting effect using Φ27 mm FRP bolts and steel rebar bolts. Large diameter FRP bolting was determined as the optimum rib support scheme to increase the productivity of the coal mine and to enhance the ground control capability for+425 level mining roadways. This study provides the laboratory testing design and theoretical prediction of large diameter FRP bolts used for rib support in large deformation roadways.