Ground support is widely implemented to mitigate dynamic rock failures in underground mines.This paper investigated the ground support requirements in burst-prone mines to mitigate the catastrophic dynamic rock failur...Ground support is widely implemented to mitigate dynamic rock failures in underground mines.This paper investigated the ground support requirements in burst-prone mines to mitigate the catastrophic dynamic rock failures of rock and/or coal bursts.First,the ground support principles and considerations in burst-prone conditions are identified.The objective of a ground support system is to increase the capacity to accommodate rock fracturing in a rockburst and,in turn,to minimize the kinetic energy of the ejected material.The support capacities of various yielding rockbolts and integrated support systems are then investigated using the test results in the laboratory.Apart from the energy absorption and yielding deformation capacity,the initial stiffness and energy absorption rate are also critical factors when applying yielding rockbolts in practice.Adding rope lacing and mesh strap to surface support elements can substantially enhance the support performance of the system.In practice,semi-analytical and empirical approaches are often used to determine the ground support elements in burst-prone areas.Semi-analytical methods first evaluate the support demand in burst risk zones and then select support elements according to their laboratory test results.Alternatively,empirical methods determine the ground support elements according to the locally established empirical rating scheme,which usually ranks the support capacities of various support systems based on ground support conditions and damage conditions.The outcomes of this study can provide insights into ground support strategies and assist the mining industry to develop effective coal burst control technologies.展开更多
Cryogenic ground support equipment (CGSE) is an important part of a famous particle physics experiment - AMS-02. In this paper a design method which optimizes PID parameters of CGSE control system via the particle swa...Cryogenic ground support equipment (CGSE) is an important part of a famous particle physics experiment - AMS-02. In this paper a design method which optimizes PID parameters of CGSE control system via the particle swarm optimization (PSO) algorithm is presented. Firstly, an improved version of the original PSO, cooperative random learning particle swarm optimization (CRPSO), is put forward to enhance the performance of the conventional PSO. Secondly, the way of finding PID coefficient will be studied by using this algorithm. Finally, the experimental results and practical works demonstrate that the CRPSO-PID controller achieves a good performance.展开更多
Despite recent advances in mine health and safety, roof collapse and instabilities are still the leading causes of injury and fatality in underground mining operations. Improving safety and optimum design of ground su...Despite recent advances in mine health and safety, roof collapse and instabilities are still the leading causes of injury and fatality in underground mining operations. Improving safety and optimum design of ground support requires good and reliable ground characterization. While many geophysical methods have been developed for ground characterizations, their accuracy is insufficient for customized ground support design of underground workings. The actual measurements on the samples of the roof and wall strata from the exploration boring are reliable but the related holes are far apart, thus unsuitable for design purposes. The best source of information could be the geological back mapping of the roof and walls, but this is disruptive to mining operations, and provided information is only from rock surface.Interpretation of the data obtained from roof bolt drilling can offer a good and reliable source of information that can be used for ground characterization and ground support design and evaluations. This paper offers a brief review of the mine roof characterization methods, followed by introduction and discussion of the roof characterization methods by instrumented roof bolters. A brief overview of the results of the preliminary study and initial testing on an instrumented drill and summary of the suggested improvements are also discussed.展开更多
To better understand the failure behaviours and strength of bolt-reinforced blocky rocks,large scale extensive laboratory experiments are carried out on blocky rock-like specimens with and without rockbolt reinforceme...To better understand the failure behaviours and strength of bolt-reinforced blocky rocks,large scale extensive laboratory experiments are carried out on blocky rock-like specimens with and without rockbolt reinforcement.The results show that both shear failure and tensile failure along joint surfaces are observed but the shear failure is a main controlling factor for the peak strength of the rock mass with and without rockbolts.The rockbolts are necked and shear deformation simultaneously happens in bolt reinforced rock specimens.As the joint dip angle increases,the joint shear failure becomes more dominant.The number of rockbolts has a significant impact on the peak strain and uniaxial compressive strength(UCS),but little influence on the deformation modulus of the rock mass.Using the Winkler beam model to represent the rockbolt behaviours,an analytical model for the prediction of the strength of boltreinforced blocky rocks is proposed.Good agreement between the UCS values predicted by proposed model and obtained from experiments suggest an encouraging performance of the proposed model.In addition,the performance of the proposed model is further assessed using published results in the literature,indicating the proposed model can be used effectively in the prediction of UCS of bolt-reinforced blocky rocks.展开更多
Ground control in underground mines employs rock reinforcement and surface support to maintain the integrity of excavations for their anticipated working life.The performance of a ground support system,however,is more...Ground control in underground mines employs rock reinforcement and surface support to maintain the integrity of excavations for their anticipated working life.The performance of a ground support system,however,is more complex and relies on effective load distribution between reinforcement and surface support elements.Typically,failure of the ground support system is along its weakest link,often the surface support.Consequently,the degradation of any ground support element over time will compromise the structural integrity of the ground support system.Degradation of ground support can be due to multiple factors.This paper focuses on the role of corrosion in the long-term performance of mesh.It presents a comprehensive methodology for quantifying the impact of degradation on bolted welded wire mesh over time.This is an important aspect,as the mesh is often the first element that fails in a ground support system.This paper combines information from extensive field and laboratory studies on mesh corrosion with calibrated numerical models to capture the long-term performance of different bolting patterns under a range of corrosion environments.A series of three-dimensional(3D)distinct element models(DEM)were constructed to quantify the impact of different corrosion rate scenarios on the loading capacity,displacement,and failure mechanisms of bolted welded wire mesh in diamond and square bolting patterns.This work can contribute to the management of long-term hazards associated with corrosion of mesh in corrosive environments under non-seismic mining conditions.展开更多
This paper presents details of the early to mid-stage deterioration in the form of notch growth of two 3 m diameter bored raises that were excavated and slashed to 7.8 m to serve as an internal shaft(winze).In additio...This paper presents details of the early to mid-stage deterioration in the form of notch growth of two 3 m diameter bored raises that were excavated and slashed to 7.8 m to serve as an internal shaft(winze).In addition,the long-term deterioration of a series of ore/waste passes that were excavated with the bottom-up Alimak methodology is investigated.These excavations were completed at depths between 1200 and 1915 m below the surface in a hard rock mine in Sudbury,Ontario,Canada.The ability to see a cross-section of fracturing around the bored raises while slashing into them and observing the progressive growth of fractures was critical for understanding the factors leading to deterioration.The Alimak-driven ore/waste passes were in an advanced state of deterioration,which provided a late-stage notch growth profile that could be compared with the notch growth observed in the bored raises.The methods used to support and stabilize these excavations are detailed;in addition,methodologies to prevent some of the deterioration from occurring are also presented.The findings of this work are useful for understanding the mechanisms driving brittle rock failure in deep mining and subsequently for minimizing or preventing the deterioration from occurring.展开更多
The Kabul-Mazar Highway connects Kabul,the capital of Afghanistan,to northern provinces of the country,and further extends into Central Asian countries through the Hindukush mountains.The Salang Tunnel,which is 2600 m...The Kabul-Mazar Highway connects Kabul,the capital of Afghanistan,to northern provinces of the country,and further extends into Central Asian countries through the Hindukush mountains.The Salang Tunnel,which is 2600 m long,was designed by Soviet engineers in 1958 and constructed using conventional techniques in 1964.During its construction,the tunnel ranked the distinction of being the highest-altitude tunnel at 3400 m.The socioeconomic importance of the tunnel is exceptionally high,as the Hindukush Mountain range to the east and south of the country is crossed by it.Since 1964,there has been a significant increase in traffic volume.Due to the narrowness of the existing tunnel,the Ministry of Public Works(MOPW)of Afghanistan has planned the con-struction of new twin-tube tunnels.Although there have been rehabilitation and enlargement efforts for the existing tunnel,none of these renovation works have been proven effective,and challenges persist.In 2008,the MOPW initiated a pre-feasibility study for new tunnels,which was finalized in 2012,presenting various options.Subsequently,in early 2018,the MOPW commenced feasibility and detailed studies,leading to the proposal of new twin-tube tunnels,which are designated as the planned tunnels in this paper.In this study,the available geotechnical and environmental data are used to evaluate the rock engineering aspects of the tunnels,including an assessment of the in-situ stress state.A particular emphasis is placed on the reassessment and design of the support system for both the existing and planned tunnels according to RMQR and another system,respectively.The evaluation of the response and stability of the tunnels is concluded,and the implications are subsequently discussed.展开更多
A12.24km long tunnel between Maroshi and Ruparel College is being excavated by tunnel boring machine(TBM)to improve the water supply system of Greater Mumbai,India.In this paper,attempt has been made to establish the ...A12.24km long tunnel between Maroshi and Ruparel College is being excavated by tunnel boring machine(TBM)to improve the water supply system of Greater Mumbai,India.In this paper,attempt has been made to establish the relationship between various litho-units of Deccan traps,stability of tunnel and TBM performances during the construction of5.83km long tunnel between Maroshi and Vakola.The Maroshi–Vakola tunnel passes under the Mumbai Airport and crosses both runways with an overburden cover of around70m.The tunneling work was carried out without disturbance to the ground.The rock types encountered during excavation arefine compacted basalt,porphyritic basalt,amygdaloidal basalt pyroclastic rocks with layers of red boles and intertrappean beds consisting of various types of shales Relations between rock mass properties,physico-mechanical properties,TBM specifications and the cor responding TBM performance were established.A number of support systems installed in the tunne during excavation were also discussed.The aim of this paper is to establish,with appropriate accuracy the nature of subsurface rock mass condition and to study how it will react to or behave during under ground excavation by TBM.The experiences gained from this project will increase the ability to cope with unexpected ground conditions during tunneling using TBM.展开更多
Roof and rib instability is an important issue in underground mining. To optimize ground support design,enhance ground stability, and reduce the possibility of roof or rib failure with minimal use of artificial ground...Roof and rib instability is an important issue in underground mining. To optimize ground support design,enhance ground stability, and reduce the possibility of roof or rib failure with minimal use of artificial ground support, it is essential to have an accurate understanding of ground conditions. This includes the location of voids, cracks, and discontinuities, as well as information about the different strata in the immediate roof. This paper briefly introduces ongoing research on void detection by using the roof bolter feed and rotation pressure. The goal of this project is to improve the sensitivity of detection programs to locate smaller joints and reduce the number of false alarms. This paper presents a brief review of the testing procedures, data analysis, logic, and algorithms used for void detection. In addition, this paper discusses the results of preliminary laboratory tests and statistical analysis of the data from these two drilling parameters used for void detection.展开更多
Impact drop tests are routinely used to examine the dynamic performance of rockbolts.Numerous impact tests have been carried out in the past decades on independently designed,constructed and operated testing rigs.Each...Impact drop tests are routinely used to examine the dynamic performance of rockbolts.Numerous impact tests have been carried out in the past decades on independently designed,constructed and operated testing rigs.Each laboratory has developed testing procedures;thus,the results are often reported in different ways by various laboratories.The inconsistency in testing procedures and reporting formats presents a challenge when comparing results from different laboratories.A series of impact tests of identical rockbolts was carried out using the direct impact method(i.e.the mass free-fall method)on the rigs in four laboratories in different countries.The purpose of these tests was to investigate the level of consistency in the results from the four rigs.Each rig demonstrated a high level of repeatability,but differences existed between the various rigs.The differences would suggest that there is noticeable equipment-dependent bias when test results obtained from different laboratories are compared.It was also observed that the energy dissipated for the plastic displacement of the bolt was smaller than the impact energy in the tests.The average impact load(AIL)and the ultimate plastic displacement(D)of the bolt describe the ultimate dynamic performance of the bolt.In the case where the bolt does not rupture,the specific plastic energy(SPE)is an appropriate parameter in describing the impact performance of the bolt.Two other relevant parameters are the first peak load(FPL)and the initial stiffness(K)of the bolt sample.The information from this test series will guide the formulation of standardised testing procedures for dynamic impact tests of rockbolts.展开更多
Trusses used for roof support in coal mines are constructed of two grouted bolts installed at opposing forty-five degree angles into the roof and a cross member that ties the angled bolts together. The load on the cro...Trusses used for roof support in coal mines are constructed of two grouted bolts installed at opposing forty-five degree angles into the roof and a cross member that ties the angled bolts together. The load on the cross member is vertical, which is transverse to the longitudinal axis, and therefore the cross member is loaded in the weakest direction. Laboratory tests were conducted to determine the vertical load capacity and deflection of three different types of cross members. Single-point load tests, with the load applied in the center of the specimen and double-point load tests, with a span of 2.4 m, were conducted. For the single-point load configuration, the yield of the 25 mm solid bar cross member was nominally 98 kN of vertical load, achieved at 42 cm of deflection. For cable cross members, yield was not achieved even after 45 cm of deflection. Peak vertical loads were about 89 kN for 17 mm cables and67 kN for the 15 mm cables. For the double-point load configurations, the 25 mm solid bar cross members yielded at 150 kN of vertical load and 25 cm of deflection. At 25 cm of deflection individual cable strands started breaking at 133 and 111 kN of vertical load for the 17 and 15 mm cable cross members respectively.展开更多
Ground support systems are commonly used to mitigate the potential consequences of rockburst in burst prone mines.To assess the capacity of ground support systems when subjected to dynamic loading,simulated rockburst ...Ground support systems are commonly used to mitigate the potential consequences of rockburst in burst prone mines.To assess the capacity of ground support systems when subjected to dynamic loading,simulated rockburst tests using blasting were conducted at the Kiruna Mine.In this study,a numerical simulation for one of the field tests was conducted using the LS-DYNA code to investigate the dynamic response of the ground support systems including shotcrete and rockbolts.The numerical results showed a similar particle vibration pattern and a crack pattern to those of the field measurements.The effects of the detonator position and the charge configuration on the dynamic response of ground support systems are also discussed.Numerical results indicated that the peak particle vibrations on the tested panel increase along the direction of detonation propagation.It is difficult to use different charge concentrations in one borehole to investigate the effect of different dynamic loads on the dynamic response of support systems.Numerical results also indicated that 2D numerical modeling for simulated rockburst experiments could overestimate the dynamic response of ground support systems.展开更多
The tunnel industry has considered that tunnels,especially tunnels in rock,are naturally resistant to earthquake action,including faulting,shaking,deflection and ground failure.As the number of case histories of tunne...The tunnel industry has considered that tunnels,especially tunnels in rock,are naturally resistant to earthquake action,including faulting,shaking,deflection and ground failure.As the number of case histories of tunnels subject to earthquake action has increased,the industry has started to recognize that,although tunnels in rock have good resistance against earthquakes generating peak ground accelerations(PGA)lower than 0.5 g,it is important to include the dynamic forces and displacements generated by seismic ground motions in the design process to obtain a more reliable design.These additional earthquake forces impact the final design,potentially requiring changes to the ground support and additional reinforcement of the concrete lining,as illustrated by case histories presented in this paper.展开更多
Vehicle bumps at a bridge approach caused by the differential settlement between a bridge and an adjacent backfill embankment are one of the most difficult problems in geotechnical engineering. Large vehicle bumps mak...Vehicle bumps at a bridge approach caused by the differential settlement between a bridge and an adjacent backfill embankment are one of the most difficult problems in geotechnical engineering. Large vehicle bumps make drivers uncomfortable and cause large impact loads on vehicles and the bridge abutment. A new ground-improvement technique called fixed-geosynthetic-reinforced and pile-supported embankment(FGT embankment) was developed and used to alleviate vehicle bumps at a trial bridge-approach site located in central China. To distribute the differential settlement between the bridge and adjacent backfill embankment over a long transition zone, the following three techniques were used at the trial bridge-approach site:(a) the FGT embankment,(b) conventional geosynthetic-reinforced and pile-supported embankment(CT embankment), and(c) geosynthetic-reinforced embankment without piles(GR embankment). The performance of all three techniques in the field trial was investigated by field measurements involving earth pressure cells, geosynthetic deformation sensors, and settlement gauges. The FGT and CT embankments exhibited better performance than the GR embankment. Compared with the CT embankment, the FGT embankment was more effective at ground improvement. At an elevation of 4.0 m from the base of the embankment, the pressures below the geosynthetic were smaller than those above the geosynthetic at the closest measurement point. The difference between the pressures between above and below the geosynthetic tended to increase with the embankment height.展开更多
文摘Ground support is widely implemented to mitigate dynamic rock failures in underground mines.This paper investigated the ground support requirements in burst-prone mines to mitigate the catastrophic dynamic rock failures of rock and/or coal bursts.First,the ground support principles and considerations in burst-prone conditions are identified.The objective of a ground support system is to increase the capacity to accommodate rock fracturing in a rockburst and,in turn,to minimize the kinetic energy of the ejected material.The support capacities of various yielding rockbolts and integrated support systems are then investigated using the test results in the laboratory.Apart from the energy absorption and yielding deformation capacity,the initial stiffness and energy absorption rate are also critical factors when applying yielding rockbolts in practice.Adding rope lacing and mesh strap to surface support elements can substantially enhance the support performance of the system.In practice,semi-analytical and empirical approaches are often used to determine the ground support elements in burst-prone areas.Semi-analytical methods first evaluate the support demand in burst risk zones and then select support elements according to their laboratory test results.Alternatively,empirical methods determine the ground support elements according to the locally established empirical rating scheme,which usually ranks the support capacities of various support systems based on ground support conditions and damage conditions.The outcomes of this study can provide insights into ground support strategies and assist the mining industry to develop effective coal burst control technologies.
基金the National Basic Research Program (973) of China (No. 2004CB720703)
文摘Cryogenic ground support equipment (CGSE) is an important part of a famous particle physics experiment - AMS-02. In this paper a design method which optimizes PID parameters of CGSE control system via the particle swarm optimization (PSO) algorithm is presented. Firstly, an improved version of the original PSO, cooperative random learning particle swarm optimization (CRPSO), is put forward to enhance the performance of the conventional PSO. Secondly, the way of finding PID coefficient will be studied by using this algorithm. Finally, the experimental results and practical works demonstrate that the CRPSO-PID controller achieves a good performance.
基金supported by the funding of the National Institute for Occupational Safety and Health under a contract with the Pennsylvania State University as part of the capacity building in ground supportthe funding from TüBITAK of Turkey has been used to support the sabbatical leave of Dr.Kahraman who made some contributions to this study
文摘Despite recent advances in mine health and safety, roof collapse and instabilities are still the leading causes of injury and fatality in underground mining operations. Improving safety and optimum design of ground support requires good and reliable ground characterization. While many geophysical methods have been developed for ground characterizations, their accuracy is insufficient for customized ground support design of underground workings. The actual measurements on the samples of the roof and wall strata from the exploration boring are reliable but the related holes are far apart, thus unsuitable for design purposes. The best source of information could be the geological back mapping of the roof and walls, but this is disruptive to mining operations, and provided information is only from rock surface.Interpretation of the data obtained from roof bolt drilling can offer a good and reliable source of information that can be used for ground characterization and ground support design and evaluations. This paper offers a brief review of the mine roof characterization methods, followed by introduction and discussion of the roof characterization methods by instrumented roof bolters. A brief overview of the results of the preliminary study and initial testing on an instrumented drill and summary of the suggested improvements are also discussed.
基金supported by the National Key Research and Development Projects of China(No.2021YFB2600402)National Natural Science Foundation of China(Nos.52209148 and 52374119)+1 种基金the opening fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(No.SKLGME023023)the opening fund of Key Laboratory of Water Management and Water Security for Yellow River Basin,Ministry of Water Resources(No.2023-SYSJJ-02)。
文摘To better understand the failure behaviours and strength of bolt-reinforced blocky rocks,large scale extensive laboratory experiments are carried out on blocky rock-like specimens with and without rockbolt reinforcement.The results show that both shear failure and tensile failure along joint surfaces are observed but the shear failure is a main controlling factor for the peak strength of the rock mass with and without rockbolts.The rockbolts are necked and shear deformation simultaneously happens in bolt reinforced rock specimens.As the joint dip angle increases,the joint shear failure becomes more dominant.The number of rockbolts has a significant impact on the peak strain and uniaxial compressive strength(UCS),but little influence on the deformation modulus of the rock mass.Using the Winkler beam model to represent the rockbolt behaviours,an analytical model for the prediction of the strength of boltreinforced blocky rocks is proposed.Good agreement between the UCS values predicted by proposed model and obtained from experiments suggest an encouraging performance of the proposed model.In addition,the performance of the proposed model is further assessed using published results in the literature,indicating the proposed model can be used effectively in the prediction of UCS of bolt-reinforced blocky rocks.
基金supported by the Natural Sciences and Engineering Research Council of Canada(Grant No.RGPIN-2019-06707).
文摘Ground control in underground mines employs rock reinforcement and surface support to maintain the integrity of excavations for their anticipated working life.The performance of a ground support system,however,is more complex and relies on effective load distribution between reinforcement and surface support elements.Typically,failure of the ground support system is along its weakest link,often the surface support.Consequently,the degradation of any ground support element over time will compromise the structural integrity of the ground support system.Degradation of ground support can be due to multiple factors.This paper focuses on the role of corrosion in the long-term performance of mesh.It presents a comprehensive methodology for quantifying the impact of degradation on bolted welded wire mesh over time.This is an important aspect,as the mesh is often the first element that fails in a ground support system.This paper combines information from extensive field and laboratory studies on mesh corrosion with calibrated numerical models to capture the long-term performance of different bolting patterns under a range of corrosion environments.A series of three-dimensional(3D)distinct element models(DEM)were constructed to quantify the impact of different corrosion rate scenarios on the loading capacity,displacement,and failure mechanisms of bolted welded wire mesh in diamond and square bolting patterns.This work can contribute to the management of long-term hazards associated with corrosion of mesh in corrosive environments under non-seismic mining conditions.
文摘This paper presents details of the early to mid-stage deterioration in the form of notch growth of two 3 m diameter bored raises that were excavated and slashed to 7.8 m to serve as an internal shaft(winze).In addition,the long-term deterioration of a series of ore/waste passes that were excavated with the bottom-up Alimak methodology is investigated.These excavations were completed at depths between 1200 and 1915 m below the surface in a hard rock mine in Sudbury,Ontario,Canada.The ability to see a cross-section of fracturing around the bored raises while slashing into them and observing the progressive growth of fractures was critical for understanding the factors leading to deterioration.The Alimak-driven ore/waste passes were in an advanced state of deterioration,which provided a late-stage notch growth profile that could be compared with the notch growth observed in the bored raises.The methods used to support and stabilize these excavations are detailed;in addition,methodologies to prevent some of the deterioration from occurring are also presented.The findings of this work are useful for understanding the mechanisms driving brittle rock failure in deep mining and subsequently for minimizing or preventing the deterioration from occurring.
文摘The Kabul-Mazar Highway connects Kabul,the capital of Afghanistan,to northern provinces of the country,and further extends into Central Asian countries through the Hindukush mountains.The Salang Tunnel,which is 2600 m long,was designed by Soviet engineers in 1958 and constructed using conventional techniques in 1964.During its construction,the tunnel ranked the distinction of being the highest-altitude tunnel at 3400 m.The socioeconomic importance of the tunnel is exceptionally high,as the Hindukush Mountain range to the east and south of the country is crossed by it.Since 1964,there has been a significant increase in traffic volume.Due to the narrowness of the existing tunnel,the Ministry of Public Works(MOPW)of Afghanistan has planned the con-struction of new twin-tube tunnels.Although there have been rehabilitation and enlargement efforts for the existing tunnel,none of these renovation works have been proven effective,and challenges persist.In 2008,the MOPW initiated a pre-feasibility study for new tunnels,which was finalized in 2012,presenting various options.Subsequently,in early 2018,the MOPW commenced feasibility and detailed studies,leading to the proposal of new twin-tube tunnels,which are designated as the planned tunnels in this paper.In this study,the available geotechnical and environmental data are used to evaluate the rock engineering aspects of the tunnels,including an assessment of the in-situ stress state.A particular emphasis is placed on the reassessment and design of the support system for both the existing and planned tunnels according to RMQR and another system,respectively.The evaluation of the response and stability of the tunnels is concluded,and the implications are subsequently discussed.
基金a part of the project "Universities Natural Science Research Project in Anhui Province" (KJ2011Z375)supported by Department of Education of Anhui Province
文摘A12.24km long tunnel between Maroshi and Ruparel College is being excavated by tunnel boring machine(TBM)to improve the water supply system of Greater Mumbai,India.In this paper,attempt has been made to establish the relationship between various litho-units of Deccan traps,stability of tunnel and TBM performances during the construction of5.83km long tunnel between Maroshi and Vakola.The Maroshi–Vakola tunnel passes under the Mumbai Airport and crosses both runways with an overburden cover of around70m.The tunneling work was carried out without disturbance to the ground.The rock types encountered during excavation arefine compacted basalt,porphyritic basalt,amygdaloidal basalt pyroclastic rocks with layers of red boles and intertrappean beds consisting of various types of shales Relations between rock mass properties,physico-mechanical properties,TBM specifications and the cor responding TBM performance were established.A number of support systems installed in the tunne during excavation were also discussed.The aim of this paper is to establish,with appropriate accuracy the nature of subsurface rock mass condition and to study how it will react to or behave during under ground excavation by TBM.The experiences gained from this project will increase the ability to cope with unexpected ground conditions during tunneling using TBM.
文摘Roof and rib instability is an important issue in underground mining. To optimize ground support design,enhance ground stability, and reduce the possibility of roof or rib failure with minimal use of artificial ground support, it is essential to have an accurate understanding of ground conditions. This includes the location of voids, cracks, and discontinuities, as well as information about the different strata in the immediate roof. This paper briefly introduces ongoing research on void detection by using the roof bolter feed and rotation pressure. The goal of this project is to improve the sensitivity of detection programs to locate smaller joints and reduce the number of false alarms. This paper presents a brief review of the testing procedures, data analysis, logic, and algorithms used for void detection. In addition, this paper discusses the results of preliminary laboratory tests and statistical analysis of the data from these two drilling parameters used for void detection.
文摘Impact drop tests are routinely used to examine the dynamic performance of rockbolts.Numerous impact tests have been carried out in the past decades on independently designed,constructed and operated testing rigs.Each laboratory has developed testing procedures;thus,the results are often reported in different ways by various laboratories.The inconsistency in testing procedures and reporting formats presents a challenge when comparing results from different laboratories.A series of impact tests of identical rockbolts was carried out using the direct impact method(i.e.the mass free-fall method)on the rigs in four laboratories in different countries.The purpose of these tests was to investigate the level of consistency in the results from the four rigs.Each rig demonstrated a high level of repeatability,but differences existed between the various rigs.The differences would suggest that there is noticeable equipment-dependent bias when test results obtained from different laboratories are compared.It was also observed that the energy dissipated for the plastic displacement of the bolt was smaller than the impact energy in the tests.The average impact load(AIL)and the ultimate plastic displacement(D)of the bolt describe the ultimate dynamic performance of the bolt.In the case where the bolt does not rupture,the specific plastic energy(SPE)is an appropriate parameter in describing the impact performance of the bolt.Two other relevant parameters are the first peak load(FPL)and the initial stiffness(K)of the bolt sample.The information from this test series will guide the formulation of standardised testing procedures for dynamic impact tests of rockbolts.
文摘Trusses used for roof support in coal mines are constructed of two grouted bolts installed at opposing forty-five degree angles into the roof and a cross member that ties the angled bolts together. The load on the cross member is vertical, which is transverse to the longitudinal axis, and therefore the cross member is loaded in the weakest direction. Laboratory tests were conducted to determine the vertical load capacity and deflection of three different types of cross members. Single-point load tests, with the load applied in the center of the specimen and double-point load tests, with a span of 2.4 m, were conducted. For the single-point load configuration, the yield of the 25 mm solid bar cross member was nominally 98 kN of vertical load, achieved at 42 cm of deflection. For cable cross members, yield was not achieved even after 45 cm of deflection. Peak vertical loads were about 89 kN for 17 mm cables and67 kN for the 15 mm cables. For the double-point load configurations, the 25 mm solid bar cross members yielded at 150 kN of vertical load and 25 cm of deflection. At 25 cm of deflection individual cable strands started breaking at 133 and 111 kN of vertical load for the 17 and 15 mm cable cross members respectively.
基金supported by the Centre of Advanced Mining&Metallurgy(CAMM2)at Lulea University of Technologythe support from the project of SLIM funded by the European Union’s Horizon 2020 research and innovation program under grant agreement N°730294.
文摘Ground support systems are commonly used to mitigate the potential consequences of rockburst in burst prone mines.To assess the capacity of ground support systems when subjected to dynamic loading,simulated rockburst tests using blasting were conducted at the Kiruna Mine.In this study,a numerical simulation for one of the field tests was conducted using the LS-DYNA code to investigate the dynamic response of the ground support systems including shotcrete and rockbolts.The numerical results showed a similar particle vibration pattern and a crack pattern to those of the field measurements.The effects of the detonator position and the charge configuration on the dynamic response of ground support systems are also discussed.Numerical results indicated that the peak particle vibrations on the tested panel increase along the direction of detonation propagation.It is difficult to use different charge concentrations in one borehole to investigate the effect of different dynamic loads on the dynamic response of support systems.Numerical results also indicated that 2D numerical modeling for simulated rockburst experiments could overestimate the dynamic response of ground support systems.
文摘The tunnel industry has considered that tunnels,especially tunnels in rock,are naturally resistant to earthquake action,including faulting,shaking,deflection and ground failure.As the number of case histories of tunnels subject to earthquake action has increased,the industry has started to recognize that,although tunnels in rock have good resistance against earthquakes generating peak ground accelerations(PGA)lower than 0.5 g,it is important to include the dynamic forces and displacements generated by seismic ground motions in the design process to obtain a more reliable design.These additional earthquake forces impact the final design,potentially requiring changes to the ground support and additional reinforcement of the concrete lining,as illustrated by case histories presented in this paper.
基金supported by the National Natural Science Foundation of China(Grant No.51278216)the Research Fund of the Key Laboratory of Transportation Tunnel Engineering+1 种基金Ministry of Education(Grant No.TTE2014-05)the Basic Research Program in Shanxi Province(Grant No.2014021033-1)
文摘Vehicle bumps at a bridge approach caused by the differential settlement between a bridge and an adjacent backfill embankment are one of the most difficult problems in geotechnical engineering. Large vehicle bumps make drivers uncomfortable and cause large impact loads on vehicles and the bridge abutment. A new ground-improvement technique called fixed-geosynthetic-reinforced and pile-supported embankment(FGT embankment) was developed and used to alleviate vehicle bumps at a trial bridge-approach site located in central China. To distribute the differential settlement between the bridge and adjacent backfill embankment over a long transition zone, the following three techniques were used at the trial bridge-approach site:(a) the FGT embankment,(b) conventional geosynthetic-reinforced and pile-supported embankment(CT embankment), and(c) geosynthetic-reinforced embankment without piles(GR embankment). The performance of all three techniques in the field trial was investigated by field measurements involving earth pressure cells, geosynthetic deformation sensors, and settlement gauges. The FGT and CT embankments exhibited better performance than the GR embankment. Compared with the CT embankment, the FGT embankment was more effective at ground improvement. At an elevation of 4.0 m from the base of the embankment, the pressures below the geosynthetic were smaller than those above the geosynthetic at the closest measurement point. The difference between the pressures between above and below the geosynthetic tended to increase with the embankment height.
