The grouted bolt,combining rock bolting with grouting techniques,provides an effective solution for controlling the surrounding rock in deep soft rock and fractured roadways.It has been extensively applied in numerous...The grouted bolt,combining rock bolting with grouting techniques,provides an effective solution for controlling the surrounding rock in deep soft rock and fractured roadways.It has been extensively applied in numerous deep mining areas characterized by soft rock roadways,where it has demonstrated remarkable control results.This article systematically explores the evolution of grouted bolting,covering its theoretical foundations,design methods,materials,construction processes,monitoring measures,and methods for assessing its effectiveness.The overview encompassed several key elements,delving into anchoring theory and grouting reinforcement theory.The new principle of high pretensioned high-pressure splitting grouted bolting collaborative active control is introduced.A fresh method for dynamic information design is also highlighted.The discussion touches on both conventional grouting rock bolts and cable bolts,as well as innovative grouted rock bolts and cables characterized by their high pretension,strength,and sealing hole pressure.An examination of the merits and demerits of standard inorganic and organic grouting materials versus the new inorganic–organic composite materials,including their specific application conditions,was conducted.Additionally,the article presents various methods and instruments to assess the support effect of grouting rock bolts,cable bolts,and grouting reinforcement.Furthermore,it provides a foundation for understanding the factors influencing decisions on grouted bolting timing,the sequence of grouting,the pressure applied,the volume of grout used,and the strategic arrangement of grouted rock bolts and cable bolts.The application of the high pretensioned high-pressure splitting grouted bolting collaborative control technology in a typical kilometer-deep soft rock mine in China—the soft coal seam and soft rock roadway in the Kouzidong coal mine,Huainan coal mining area,was introduced.Finally,the existing problems in grouted bolting control technology for deep soft rock roadways are analyzed,and the future development trend of grouted bolting control technology is anticipated.展开更多
According to the research results in world, the paper comprehensively analyzed and gave a demonstration of mechanism of single-truss and its stressing advantage. Comparison and analysis effect were given to single-tru...According to the research results in world, the paper comprehensively analyzed and gave a demonstration of mechanism of single-truss and its stressing advantage. Comparison and analysis effect were given to single-truss and bolting supporting. By the way of element simulation. The paper shows that single truss supporting have better effect to bolting supporting to improving the stress condition of surrounding rocks, controlling the surrounding rocks plastic failure development zone and deformation effect of surrounding rocks, which provided the elementary theory basis to the research, experiment and expanding the single-truss bolting technology in colliery.展开更多
In deep underground mining, the surrounding rocks are very soft with high stress. Their deformation and destruction are serious, and frequent failures occur on the bolt support. The failure mechanism of bolt support i...In deep underground mining, the surrounding rocks are very soft with high stress. Their deformation and destruction are serious, and frequent failures occur on the bolt support. The failure mechanism of bolt support is proposed to solve these problems. A calculation theory is established on the bond strength of the interface between the anchoring agent and surrounding rocks. An analysis is made on the influence law of different mechanical parameters of surrounding rocks on the interfacial bond strength. Based on the research, a new high-strength bolt-grouting technology is developed and applied on site. Besides, some helpful engineering suggestions and measures are proposed. The research shows that the serious deformation and failure, and the lower bond strength are the major factors causing frequent failures of bolt support. So, the bolt could not give full play to its supporting potential. It is also shown that as the integrity, strength, interface dilatancy and stress of surrounding rocks are improved, the bond strength will increase. So, the anchoring force on surrounding rocks can be effectively improved by employing an anchoring agent with high sand content, mechanical anchoring means, or grouting reinforcement. The new technology has advantages in a high strength, imposing pre-tightening force, and giving full play to the bolt supporting potential. Hence, it can improve the control effect on surrounding rocks. All these could be helpful references for the design of bolt support in deep underground mines.展开更多
A genetic linkage map of Brassica rapa ssp. pekinensis was constructed with 186 AFLP （amplified fragment length polymorphism） markers by using a doubled-haploid （DH） population with 183 individuals. The individual...A genetic linkage map of Brassica rapa ssp. pekinensis was constructed with 186 AFLP （amplified fragment length polymorphism） markers by using a doubled-haploid （DH） population with 183 individuals. The individuals were derived from F1 which was developed by crossing a bolting resistant DH line Y-177-12 and an easy bolting DH line Y195-93a. AFLPs were generated by the use of restriction enzymes EcoR Ⅰ and Mse Ⅰ . The segregation of each marker and linkage was analyzed by using JoinMap version 3.0. Mapped markers were aligned in ten linkage groups which covered 887.8 cM with an average marker interval of 4.47 cM. Markers showing skewed segregation ratio were clustered in six LGs. Quantitative trait loci （QTL） were mapped for bolting resistance by using MAPQTL 4.0 package. Four QTLs explaining from 7.0 to 9.4% of the total variation were detected, all of them increase bolting resistance. These mapped QTLs could be used to develop a marker assisted selection programme for bolting resistance breeding.展开更多
This article introduces the principles of underground rockbolting design.The items discussed include underground loading conditions,natural pressure zone around an underground opening,design methodologies,selection of...This article introduces the principles of underground rockbolting design.The items discussed include underground loading conditions,natural pressure zone around an underground opening,design methodologies,selection of rockbolt types,determination of bolt length and spacing,factor of safety,and compatibility between support elements.Different types of rockbolting used in engineering practise are also presented.The traditional principle of selecting strong rockbolts is valid only in conditions of low in situ stresses in the rock mass.Energy-absorbing rockbolts are preferred in the case of high in situ stresses.A natural pressure arch is formed in the rock at a certain distance behind the tunnel wall.Rockbolts should be long enough to reach the natural pressure arch when the failure zone is small.The bolt length should be at least 1 m beyond the failure zone.In the case of a vast failure zone,tightly spaced short rockbolts are installed to establish an artificial pressure arch within the failure zone and long cables are anchored on the natural pressure arch.In this case,the rockbolts are usually less than 3 m long in mine drifts,but can be up to 7 m in large-scale rock caverns.Bolt spacing is more important than bolt length in the case of establishing an artificial pressure arch.In addition to the factor of safety,the maximum allowable displacement in the tunnel and the ultimate displacement capacity of rockbolts must be also taken into account in the design.Finally,rockbolts should be compatible with other support elements in the same support system in terms of displacement and energy absorption capacities.展开更多
A fully grouted bolt provides greater shear load capacity for transmitting the load from the rock to the bolt, and vice versa. When grout fills irregularities between the bolt and the rock, a keying effect is created ...A fully grouted bolt provides greater shear load capacity for transmitting the load from the rock to the bolt, and vice versa. When grout fills irregularities between the bolt and the rock, a keying effect is created to transfer the load to the bolt via shear resistance at the interface and within the grout. Previous research has revealed that the mechanical properties of the grout had a great impact on the load transfer capacity of the rock bolting system. This paper presents a method to enhance the rock bolting strength by introducing metal granules into the grouting material. Experimental results suggest that both the average peak load of pullout tests and the total energy absorption of the system will increase if some metal granules are mixed into the resin.展开更多
The flower stalk is the product organ of flowering Chinese cabbage(Brassica campestris L.ssp.chinensis var.utilis Tsen et Lee),which is cultivated extensively in South China.Flower stalk formation and development,incl...The flower stalk is the product organ of flowering Chinese cabbage(Brassica campestris L.ssp.chinensis var.utilis Tsen et Lee),which is cultivated extensively in South China.Flower stalk formation and development,including bolting and flowering,determine the yield of flowering Chinese cabbage;however,the bolting and flowering mechanisms remain to be explored.To elucidate these processes,we studied the effects of low-temperature and gibberellin(GA)treatments,and their interaction,on stem elongation,bolting time,flowering time,hormone content,and cell morphology in stem of flowering Chinese cabbage.The results showed that both cold and GA treatments accelerated bolting time,stem elongation,and flowering time.Moreover,cold and GA cotreated plants displayed additive positive effects.In addition,cold treatments increased the GA,indole-3-acetic acid,and cytokinin contents and altered cell size in the shoot apices of flowering Chinese cabbage.Treatment with uniconazole,a GA synthesis inhibitor,strongly delayed bolting time,stem elongation,and flowering time,whereas GA,but not cold treatment,rescued this inhibition,indicating that low temperature accelerates bolting and flowering not only through inducing GA in the shoot apices,but also other ways.These results provide a theoretical basis for further dissecting the regulatory mechanism of bolting and flowering in flowering Chinese cabbage.展开更多
Dust generated from bolt hole drilling in roof bolting operation could have high quartz content. As a dust control measure, vacuum drilling is employed on most of the roof bolters in US underground mines. However, fin...Dust generated from bolt hole drilling in roof bolting operation could have high quartz content. As a dust control measure, vacuum drilling is employed on most of the roof bolters in US underground mines. However, fine rock partic- ulates from drilling could escape from the dust collection system and become airborne under some circumstances causing the roof bolter operators expose to quartz-rich respirable dust. A previous research shows that drilling can be controlled through properly selected penetration and rotational rates to reduce the specific energy of drilling. Less specific energy means less energy is wasted on generating noise, heat and over-breakage of rock. It implies that proper control of drilling has a great potential to generate significantly less fine rock dust during drilling. The drilling experiments have been conducted to study the effect of controlling drilling on reducing respirable dust. The preliminary results show that the size distributions of respirable dust were different when controlling drilling in different bite depths. This paper presents the findings from laboratory experimental studies.展开更多
Rock bolting has advanced rapidly during the past 4 decades due to a better understanding of load transfer mechanisms and advances made in the bolt system technology. Bolts are used as permanent and temporary support ...Rock bolting has advanced rapidly during the past 4 decades due to a better understanding of load transfer mechanisms and advances made in the bolt system technology. Bolts are used as permanent and temporary support systems in tunnelling and mining operations. A review of has indicated that three systems of reinforcement devices have evolved as part of rock bolt and ground anchor while the rock is not generally thought of as being a component of the reinforcement system. A classification of rock bolting reinforcement systems is presented, followed by the fundamental theory of the load transfer mechanism. The failure mode of two phases of rock bolting system is formularised. The failure modes of cable bolting are discussed using a bond strength model as well as an iterative method. Finally, the interfacial shear stress model for ribbed bar is introduced and a closed form solution is obtained using a tri-line stress strain relationship.展开更多
The stress hardening characteristics of the reinforced rock mass in uniaxial compression tests were revealed by means of the experimental study on mechanical characteristics of cracked rock mass reinforced by bolting ...The stress hardening characteristics of the reinforced rock mass in uniaxial compression tests were revealed by means of the experimental study on mechanical characteristics of cracked rock mass reinforced by bolting and grouting. And the load-beating mechanism of the reinforced rock mass was perfectly reflected by the experiment. The results can offer some useful advice for support design and stability analysis of deep drifts in unstable strata.展开更多
Gateway floor heave control is the key to guarantee mine safe and efficient production. Through analysis of floor instability characteristics and bolting control, gateway floor strata show second level stress under ab...Gateway floor heave control is the key to guarantee mine safe and efficient production. Through analysis of floor instability characteristics and bolting control, gateway floor strata show second level stress under abutment pressure, which causes plastic flow failure in floor strata; gateway floor instability shows mainly shear-break slippage of ＂triangle sliding body＂. Mechanics of floor bolting is mainly a function of connection and combination. Main area of bolting control lies in two gateway floor angles. The paper analyzes mechanics principle of gateway floor instability, constructs stability mechanics model of gateway floor bolting, obtains gateway floor stability criterion of different bolting angles and optimum formula of bolting parameters, carries out the engineering example, and guides better field application. It provides theoretical base for bolting gateway floor instability control.展开更多
[ Objective ] This study aimed to analyze the inheritance of bolting associated traits in Brassica rapa, which will provide useful information in a breeding program for late-bolting or bolting-resistant cultivars of C...[ Objective ] This study aimed to analyze the inheritance of bolting associated traits in Brassica rapa, which will provide useful information in a breeding program for late-bolting or bolting-resistant cultivars of Chinese cabbage. [ Method] Three phenotypic measurements, bolting index, flowering time, days to 5 cm elongated stalk, respectively were used for inheritance analysis of six generations, P, （bolting resistant inbreed line ）, P2 （vernalization independent type） and their filial generations F1 , B1, B2 and F2, using the mixed major-gene plus polygene inheritance model. [ Result] The two traits, bolting index and days to 5 cm elongated stalk, both were controlled by two major genes with additive-dominant-epistatic effects （ B-1 model） in hybrid. The flowering time was controlled by one major gene with addltive-dominant effects plus additive-dominant-epistatic effects （D model）. The heritability of the major genes in B1, B2 and F2 were 96.22%, 93.33%, 93.55% for bolting index, 70.68%, 70.68%, 70.64% for flowering time, 79.44%, 79.55%, 79.38% for days to 5-cm elongated stalk, respectively, but no polygene heritability was detected in BI, B2 and F2 generation. It indicated that the bolting trait in Brassica rapa was controlled by one or tow major genes. [ Conclusion] This implied that in the genetic improvement for bolting resistant trait major gene was a main factor. It is fit for early selection and environment factor should be mentioned.展开更多
Roof bolting has long been used in underground mines across the world to provide ground support.Modern roof bolts are cheap and easy to install with the use of specialized machines as a part of the production cycle. L...Roof bolting has long been used in underground mines across the world to provide ground support.Modern roof bolts are cheap and easy to install with the use of specialized machines as a part of the production cycle. Lhoist North America’s Crab Orchard Mine is an underground room and pillar limestone mine that uses mechanically anchored roof bolts for ground support. The mine currently employs two different roof bolting patterns: a standard 1.5 × 1.5 m pattern, and another 0.8 × 0.8 m pattern for use in areas with particularly hazardous roof conditions. The purpose of this study is to evaluate the relative effectiveness of each bolting pattern. A series of numerical models were created using Roc Science’s RS2. The models were based on a symmetrical section of the mine at its deepest point, and were modeled using generalized Hoek-Brown failure criterion along with a discrete fracture network. A series of sensitivity analyses were performed on the models by varying parameters such as joint friction angle, crack persistence, joint randomization, and tensile strength of the limestone. Based on the results of the original models and sensitivity analyses, it appeared that the standard bolting pattern provided sufficient roof support capacity under almost all the expected conditions at the mine, since safety factors below the design value of 1.5 were only found for individual bolts in a few of the worst test cases considered.These results can help improve the mine’s productivity and reduce operating costs without compromising safety.展开更多
Qiyechangbai and Hadacongl were used to study the relationship of the leaf age of overwinter to bolting and, returning green by the difference of sowing time. The results showed that the earlier the seeds were sown, t...Qiyechangbai and Hadacongl were used to study the relationship of the leaf age of overwinter to bolting and, returning green by the difference of sowing time. The results showed that the earlier the seeds were sown, the older leaf age of overwinter was, the higher the rates of returning green and bolting rate were, the earlier the bolting time was. The leaf age of overwinter of Qiyechangbai sown August 31 to September 14 was 2.1-3.1 leaves and the rate of returning green was 86.5%-92.1%, while the leaf age of overwinter of Hadacongl sown September 7 to September 14 was 2.3-2.7 leaves and the rate of returning green was 88.5%-93.8%, both varieties didn＇t bolt. In addition, in the same sowing time, the bolting rate of Hadacong I was higher than that of Qiyechangbai slightly.展开更多
A typical gateway is analyzed using fully-deformable discrete element method. The fractured zone around the gateway is measured in field. Based on the measurement results and theoretical analysis, a comprehensive supp...A typical gateway is analyzed using fully-deformable discrete element method. The fractured zone around the gateway is measured in field. Based on the measurement results and theoretical analysis, a comprehensive support scheme adopting bolt and steel belt is proposed. Discrete element method is used to assess the bolting scheme, and displacement monitoring in field is also carried out. Having been put into practice, it is proved that the scheme is both successful and rational. According to theoretical analysis and monitoring in field, some important keynotes that should be noticed in gateway bolting practice are presented as well.展开更多
Angelica sinensis(Oliv.)Diels is a valuable herbal plant.In production,its premature bolting,caused by vernalization,seriously affects its root yield.In this stuty,thermal treatments of 5,0 and?5°C,as well as tre...Angelica sinensis(Oliv.)Diels is a valuable herbal plant.In production,its premature bolting,caused by vernalization,seriously affects its root yield.In this stuty,thermal treatments of 5,0 and?5°C,as well as treatments with shifts between these temperatures,were performed in its overwintering storage to investigate the chilling effect on the early bolting of Angelica sinensis and analyze the vernalization response to different temperatures.The results indicated that the 0°C treatment rendered the highest bolting rate,and the-5°C resulted in the lowest bolting rate.The initial short-term treatment at-5°C could promote the early bolting of A.sinensis,and the treatment at 5°C prior to planting could hasten its seedling bud growth.At the appropriate temperature,the early bolting rate of Angelica was positively related to the number of treatment days.So the frozen storage at-5°C could inhibit the vernalization of Angelica seedlings and the early bolting.The vernalization of Angelica could be a continuous process related to the number of treatment days.This study would serve as reference for the overwintering storage and cultivation of Angelica.展开更多
Described the outcomes of a comprehensive numerical modeling on the rock bolting performance for preventing the deformation of stratified, composite roof structure of drift in a coal mine. The investigation was undert...Described the outcomes of a comprehensive numerical modeling on the rock bolting performance for preventing the deformation of stratified, composite roof structure of drift in a coal mine. The investigation was undertaken in the adverse geological condi- tions, with variation of bolt parameters, including length, density, distribution, pretension, as well as the geometry of opening,so as to determine the effect of bolting parameter variation on roof deformation and stability. The outcomes clearly demonstrated that a sig- nificant improvement of roof stability can be achieved associating with bolting parameters optimization, and indicated the importance of flexible geotechnical designation of rock bolting reinforcement in mining practice.展开更多
The designing method and the supporting mechanism of both bolt and small cable anchor for full seam roadway in the weaker thick coal seam are systematically analyzed, and the construction technology and the supporting...The designing method and the supporting mechanism of both bolt and small cable anchor for full seam roadway in the weaker thick coal seam are systematically analyzed, and the construction technology and the supporting results are briefly summarized.展开更多
[Objectives]This study was conducted to screen out a vernalization method of radish that is more suitable for breeding and hybrid production.[Methods]Eight radish inbred lines with different bolting tolerance were use...[Objectives]This study was conducted to screen out a vernalization method of radish that is more suitable for breeding and hybrid production.[Methods]Eight radish inbred lines with different bolting tolerance were used as the research objects for the experiment.The following three treatments were done:(1)treating at 4℃in the dark with heat preservation for 1,2,3,4,and 5 weeks,respectively~([1]),(2)treating at 4℃in the dark with heat preservation for 3 weeks after 24 h incubation in light at 20℃,and(3)treating under light at a low temperature of 6.5℃for three weeks after cultivating under light at 20℃to 4 true leaves.The effects of low temperature treatment on the bolting and flowering time of different varieties of radish treated at different developmental stages were analyzed.[Results]When comparing these three methods,the low-temperature treatment of wet seeds had a better effect on early bolting of radish and is simpler and more feasible.The effect of treating four-leaf seedlings at 6.5℃was the worst;most radish inbred lines could shorten bolting time when treated at 4℃for one week;and within a certain range,the longer the 4℃treatment time,the better the vernalization effect.Different radish inbred lines had different performances to low temperature treatment.[Conclusions]This study provides a scientific basis for the theoretical research on vernalization of radish.展开更多
There are many varieties of vegetables in Cruciferae,which have a wide distribution and occupy an important position in the global vegetable industry.The bolting period is a crucial stage in the growth cycle of crucif...There are many varieties of vegetables in Cruciferae,which have a wide distribution and occupy an important position in the global vegetable industry.The bolting period is a crucial stage in the growth cycle of cruciferous plants,which directly affects the yield and quality of vegetable crops.This paper summarized the research progress on the physiological and biochemical characteristics,molecular genetic mechanisms and molecular markers of the flowering and bolting traits in cruciferous vegetables,in order to provide new ideas for revealing the regulatory mechanisms of flowering and bolting in cruciferous vegetables and to provide reference for the breeding of new varieties of cruciferous vegetables that are resistant to flowering.展开更多
基金the National Natural Science Foundation of China(Nos.52304141 and 52074154)。
文摘The grouted bolt,combining rock bolting with grouting techniques,provides an effective solution for controlling the surrounding rock in deep soft rock and fractured roadways.It has been extensively applied in numerous deep mining areas characterized by soft rock roadways,where it has demonstrated remarkable control results.This article systematically explores the evolution of grouted bolting,covering its theoretical foundations,design methods,materials,construction processes,monitoring measures,and methods for assessing its effectiveness.The overview encompassed several key elements,delving into anchoring theory and grouting reinforcement theory.The new principle of high pretensioned high-pressure splitting grouted bolting collaborative active control is introduced.A fresh method for dynamic information design is also highlighted.The discussion touches on both conventional grouting rock bolts and cable bolts,as well as innovative grouted rock bolts and cables characterized by their high pretension,strength,and sealing hole pressure.An examination of the merits and demerits of standard inorganic and organic grouting materials versus the new inorganic–organic composite materials,including their specific application conditions,was conducted.Additionally,the article presents various methods and instruments to assess the support effect of grouting rock bolts,cable bolts,and grouting reinforcement.Furthermore,it provides a foundation for understanding the factors influencing decisions on grouted bolting timing,the sequence of grouting,the pressure applied,the volume of grout used,and the strategic arrangement of grouted rock bolts and cable bolts.The application of the high pretensioned high-pressure splitting grouted bolting collaborative control technology in a typical kilometer-deep soft rock mine in China—the soft coal seam and soft rock roadway in the Kouzidong coal mine,Huainan coal mining area,was introduced.Finally,the existing problems in grouted bolting control technology for deep soft rock roadways are analyzed,and the future development trend of grouted bolting control technology is anticipated.
文摘According to the research results in world, the paper comprehensively analyzed and gave a demonstration of mechanism of single-truss and its stressing advantage. Comparison and analysis effect were given to single-truss and bolting supporting. By the way of element simulation. The paper shows that single truss supporting have better effect to bolting supporting to improving the stress condition of surrounding rocks, controlling the surrounding rocks plastic failure development zone and deformation effect of surrounding rocks, which provided the elementary theory basis to the research, experiment and expanding the single-truss bolting technology in colliery.
基金Projects(51304125,51379114)supported by the National Natural Science Foundation of ChinaProject(BS2013NJ004)supported by Award Fund for Outstanding Young and Middle-Aged Scientist of Shangdong Province,ChinaProject(201301004)supported by the Innovation Fund for Postdoctor of Shandong Province,China
文摘In deep underground mining, the surrounding rocks are very soft with high stress. Their deformation and destruction are serious, and frequent failures occur on the bolt support. The failure mechanism of bolt support is proposed to solve these problems. A calculation theory is established on the bond strength of the interface between the anchoring agent and surrounding rocks. An analysis is made on the influence law of different mechanical parameters of surrounding rocks on the interfacial bond strength. Based on the research, a new high-strength bolt-grouting technology is developed and applied on site. Besides, some helpful engineering suggestions and measures are proposed. The research shows that the serious deformation and failure, and the lower bond strength are the major factors causing frequent failures of bolt support. So, the bolt could not give full play to its supporting potential. It is also shown that as the integrity, strength, interface dilatancy and stress of surrounding rocks are improved, the bond strength will increase. So, the anchoring force on surrounding rocks can be effectively improved by employing an anchoring agent with high sand content, mechanical anchoring means, or grouting reinforcement. The new technology has advantages in a high strength, imposing pre-tightening force, and giving full play to the bolt supporting potential. Hence, it can improve the control effect on surrounding rocks. All these could be helpful references for the design of bolt support in deep underground mines.
文摘A genetic linkage map of Brassica rapa ssp. pekinensis was constructed with 186 AFLP （amplified fragment length polymorphism） markers by using a doubled-haploid （DH） population with 183 individuals. The individuals were derived from F1 which was developed by crossing a bolting resistant DH line Y-177-12 and an easy bolting DH line Y195-93a. AFLPs were generated by the use of restriction enzymes EcoR Ⅰ and Mse Ⅰ . The segregation of each marker and linkage was analyzed by using JoinMap version 3.0. Mapped markers were aligned in ten linkage groups which covered 887.8 cM with an average marker interval of 4.47 cM. Markers showing skewed segregation ratio were clustered in six LGs. Quantitative trait loci （QTL） were mapped for bolting resistance by using MAPQTL 4.0 package. Four QTLs explaining from 7.0 to 9.4% of the total variation were detected, all of them increase bolting resistance. These mapped QTLs could be used to develop a marker assisted selection programme for bolting resistance breeding.
文摘This article introduces the principles of underground rockbolting design.The items discussed include underground loading conditions,natural pressure zone around an underground opening,design methodologies,selection of rockbolt types,determination of bolt length and spacing,factor of safety,and compatibility between support elements.Different types of rockbolting used in engineering practise are also presented.The traditional principle of selecting strong rockbolts is valid only in conditions of low in situ stresses in the rock mass.Energy-absorbing rockbolts are preferred in the case of high in situ stresses.A natural pressure arch is formed in the rock at a certain distance behind the tunnel wall.Rockbolts should be long enough to reach the natural pressure arch when the failure zone is small.The bolt length should be at least 1 m beyond the failure zone.In the case of a vast failure zone,tightly spaced short rockbolts are installed to establish an artificial pressure arch within the failure zone and long cables are anchored on the natural pressure arch.In this case,the rockbolts are usually less than 3 m long in mine drifts,but can be up to 7 m in large-scale rock caverns.Bolt spacing is more important than bolt length in the case of establishing an artificial pressure arch.In addition to the factor of safety,the maximum allowable displacement in the tunnel and the ultimate displacement capacity of rockbolts must be also taken into account in the design.Finally,rockbolts should be compatible with other support elements in the same support system in terms of displacement and energy absorption capacities.
文摘A fully grouted bolt provides greater shear load capacity for transmitting the load from the rock to the bolt, and vice versa. When grout fills irregularities between the bolt and the rock, a keying effect is created to transfer the load to the bolt via shear resistance at the interface and within the grout. Previous research has revealed that the mechanical properties of the grout had a great impact on the load transfer capacity of the rock bolting system. This paper presents a method to enhance the rock bolting strength by introducing metal granules into the grouting material. Experimental results suggest that both the average peak load of pullout tests and the total energy absorption of the system will increase if some metal granules are mixed into the resin.
基金supported by the earmarked fund for China Agriculture Research System(CARS-25-C-04)the Natural Science Foundation of Guangdong,China(2016A030313399)
文摘The flower stalk is the product organ of flowering Chinese cabbage(Brassica campestris L.ssp.chinensis var.utilis Tsen et Lee),which is cultivated extensively in South China.Flower stalk formation and development,including bolting and flowering,determine the yield of flowering Chinese cabbage;however,the bolting and flowering mechanisms remain to be explored.To elucidate these processes,we studied the effects of low-temperature and gibberellin(GA)treatments,and their interaction,on stem elongation,bolting time,flowering time,hormone content,and cell morphology in stem of flowering Chinese cabbage.The results showed that both cold and GA treatments accelerated bolting time,stem elongation,and flowering time.Moreover,cold and GA cotreated plants displayed additive positive effects.In addition,cold treatments increased the GA,indole-3-acetic acid,and cytokinin contents and altered cell size in the shoot apices of flowering Chinese cabbage.Treatment with uniconazole,a GA synthesis inhibitor,strongly delayed bolting time,stem elongation,and flowering time,whereas GA,but not cold treatment,rescued this inhibition,indicating that low temperature accelerates bolting and flowering not only through inducing GA in the shoot apices,but also other ways.These results provide a theoretical basis for further dissecting the regulatory mechanism of bolting and flowering in flowering Chinese cabbage.
文摘Dust generated from bolt hole drilling in roof bolting operation could have high quartz content. As a dust control measure, vacuum drilling is employed on most of the roof bolters in US underground mines. However, fine rock partic- ulates from drilling could escape from the dust collection system and become airborne under some circumstances causing the roof bolter operators expose to quartz-rich respirable dust. A previous research shows that drilling can be controlled through properly selected penetration and rotational rates to reduce the specific energy of drilling. Less specific energy means less energy is wasted on generating noise, heat and over-breakage of rock. It implies that proper control of drilling has a great potential to generate significantly less fine rock dust during drilling. The drilling experiments have been conducted to study the effect of controlling drilling on reducing respirable dust. The preliminary results show that the size distributions of respirable dust were different when controlling drilling in different bite depths. This paper presents the findings from laboratory experimental studies.
文摘Rock bolting has advanced rapidly during the past 4 decades due to a better understanding of load transfer mechanisms and advances made in the bolt system technology. Bolts are used as permanent and temporary support systems in tunnelling and mining operations. A review of has indicated that three systems of reinforcement devices have evolved as part of rock bolt and ground anchor while the rock is not generally thought of as being a component of the reinforcement system. A classification of rock bolting reinforcement systems is presented, followed by the fundamental theory of the load transfer mechanism. The failure mode of two phases of rock bolting system is formularised. The failure modes of cable bolting are discussed using a bond strength model as well as an iterative method. Finally, the interfacial shear stress model for ribbed bar is introduced and a closed form solution is obtained using a tri-line stress strain relationship.
基金Projects50490273 and 50474063 supported by National Natural Science Foundation of China
文摘The stress hardening characteristics of the reinforced rock mass in uniaxial compression tests were revealed by means of the experimental study on mechanical characteristics of cracked rock mass reinforced by bolting and grouting. And the load-beating mechanism of the reinforced rock mass was perfectly reflected by the experiment. The results can offer some useful advice for support design and stability analysis of deep drifts in unstable strata.
基金Supported by the National Natural Science Foundation of China （50874037）
文摘Gateway floor heave control is the key to guarantee mine safe and efficient production. Through analysis of floor instability characteristics and bolting control, gateway floor strata show second level stress under abutment pressure, which causes plastic flow failure in floor strata; gateway floor instability shows mainly shear-break slippage of ＂triangle sliding body＂. Mechanics of floor bolting is mainly a function of connection and combination. Main area of bolting control lies in two gateway floor angles. The paper analyzes mechanics principle of gateway floor instability, constructs stability mechanics model of gateway floor bolting, obtains gateway floor stability criterion of different bolting angles and optimum formula of bolting parameters, carries out the engineering example, and guides better field application. It provides theoretical base for bolting gateway floor instability control.
基金Supported by the National Natural Science Foundation of China(30900981)the Scientific Research Fund for the Returned Overseas Chinese Scholars,Ministry Education of China(2010-1561)
文摘[ Objective ] This study aimed to analyze the inheritance of bolting associated traits in Brassica rapa, which will provide useful information in a breeding program for late-bolting or bolting-resistant cultivars of Chinese cabbage. [ Method] Three phenotypic measurements, bolting index, flowering time, days to 5 cm elongated stalk, respectively were used for inheritance analysis of six generations, P, （bolting resistant inbreed line ）, P2 （vernalization independent type） and their filial generations F1 , B1, B2 and F2, using the mixed major-gene plus polygene inheritance model. [ Result] The two traits, bolting index and days to 5 cm elongated stalk, both were controlled by two major genes with additive-dominant-epistatic effects （ B-1 model） in hybrid. The flowering time was controlled by one major gene with addltive-dominant effects plus additive-dominant-epistatic effects （D model）. The heritability of the major genes in B1, B2 and F2 were 96.22%, 93.33%, 93.55% for bolting index, 70.68%, 70.68%, 70.64% for flowering time, 79.44%, 79.55%, 79.38% for days to 5-cm elongated stalk, respectively, but no polygene heritability was detected in BI, B2 and F2 generation. It indicated that the bolting trait in Brassica rapa was controlled by one or tow major genes. [ Conclusion] This implied that in the genetic improvement for bolting resistant trait major gene was a main factor. It is fit for early selection and environment factor should be mentioned.
基金The research conducted for this study was funded by the National Institute for Occupational Safety and Health(NIOSH)under Grant Number 200-2016-90154.
文摘Roof bolting has long been used in underground mines across the world to provide ground support.Modern roof bolts are cheap and easy to install with the use of specialized machines as a part of the production cycle. Lhoist North America’s Crab Orchard Mine is an underground room and pillar limestone mine that uses mechanically anchored roof bolts for ground support. The mine currently employs two different roof bolting patterns: a standard 1.5 × 1.5 m pattern, and another 0.8 × 0.8 m pattern for use in areas with particularly hazardous roof conditions. The purpose of this study is to evaluate the relative effectiveness of each bolting pattern. A series of numerical models were created using Roc Science’s RS2. The models were based on a symmetrical section of the mine at its deepest point, and were modeled using generalized Hoek-Brown failure criterion along with a discrete fracture network. A series of sensitivity analyses were performed on the models by varying parameters such as joint friction angle, crack persistence, joint randomization, and tensile strength of the limestone. Based on the results of the original models and sensitivity analyses, it appeared that the standard bolting pattern provided sufficient roof support capacity under almost all the expected conditions at the mine, since safety factors below the design value of 1.5 were only found for individual bolts in a few of the worst test cases considered.These results can help improve the mine’s productivity and reduce operating costs without compromising safety.
基金Supported by Science and Technology Innovation Fund of Undergraduation of Northeast Agricultural University(20060201)
文摘Qiyechangbai and Hadacongl were used to study the relationship of the leaf age of overwinter to bolting and, returning green by the difference of sowing time. The results showed that the earlier the seeds were sown, the older leaf age of overwinter was, the higher the rates of returning green and bolting rate were, the earlier the bolting time was. The leaf age of overwinter of Qiyechangbai sown August 31 to September 14 was 2.1-3.1 leaves and the rate of returning green was 86.5%-92.1%, while the leaf age of overwinter of Hadacongl sown September 7 to September 14 was 2.3-2.7 leaves and the rate of returning green was 88.5%-93.8%, both varieties didn＇t bolt. In addition, in the same sowing time, the bolting rate of Hadacong I was higher than that of Qiyechangbai slightly.
文摘A typical gateway is analyzed using fully-deformable discrete element method. The fractured zone around the gateway is measured in field. Based on the measurement results and theoretical analysis, a comprehensive support scheme adopting bolt and steel belt is proposed. Discrete element method is used to assess the bolting scheme, and displacement monitoring in field is also carried out. Having been put into practice, it is proved that the scheme is both successful and rational. According to theoretical analysis and monitoring in field, some important keynotes that should be noticed in gateway bolting practice are presented as well.
基金Supported by National Natural Science Foundation of China(31260298,31660565)Science and Technology Planning Project of Gansu Province(18JR3RE243,1308RJZE288)~~
文摘Angelica sinensis(Oliv.)Diels is a valuable herbal plant.In production,its premature bolting,caused by vernalization,seriously affects its root yield.In this stuty,thermal treatments of 5,0 and?5°C,as well as treatments with shifts between these temperatures,were performed in its overwintering storage to investigate the chilling effect on the early bolting of Angelica sinensis and analyze the vernalization response to different temperatures.The results indicated that the 0°C treatment rendered the highest bolting rate,and the-5°C resulted in the lowest bolting rate.The initial short-term treatment at-5°C could promote the early bolting of A.sinensis,and the treatment at 5°C prior to planting could hasten its seedling bud growth.At the appropriate temperature,the early bolting rate of Angelica was positively related to the number of treatment days.So the frozen storage at-5°C could inhibit the vernalization of Angelica seedlings and the early bolting.The vernalization of Angelica could be a continuous process related to the number of treatment days.This study would serve as reference for the overwintering storage and cultivation of Angelica.
文摘Described the outcomes of a comprehensive numerical modeling on the rock bolting performance for preventing the deformation of stratified, composite roof structure of drift in a coal mine. The investigation was undertaken in the adverse geological condi- tions, with variation of bolt parameters, including length, density, distribution, pretension, as well as the geometry of opening,so as to determine the effect of bolting parameter variation on roof deformation and stability. The outcomes clearly demonstrated that a sig- nificant improvement of roof stability can be achieved associating with bolting parameters optimization, and indicated the importance of flexible geotechnical designation of rock bolting reinforcement in mining practice.
文摘The designing method and the supporting mechanism of both bolt and small cable anchor for full seam roadway in the weaker thick coal seam are systematically analyzed, and the construction technology and the supporting results are briefly summarized.
基金Supported by Agricultural Improved Variety Project of Shandong Province(2017LZN045)。
文摘[Objectives]This study was conducted to screen out a vernalization method of radish that is more suitable for breeding and hybrid production.[Methods]Eight radish inbred lines with different bolting tolerance were used as the research objects for the experiment.The following three treatments were done:(1)treating at 4℃in the dark with heat preservation for 1,2,3,4,and 5 weeks,respectively~([1]),(2)treating at 4℃in the dark with heat preservation for 3 weeks after 24 h incubation in light at 20℃,and(3)treating under light at a low temperature of 6.5℃for three weeks after cultivating under light at 20℃to 4 true leaves.The effects of low temperature treatment on the bolting and flowering time of different varieties of radish treated at different developmental stages were analyzed.[Results]When comparing these three methods,the low-temperature treatment of wet seeds had a better effect on early bolting of radish and is simpler and more feasible.The effect of treating four-leaf seedlings at 6.5℃was the worst;most radish inbred lines could shorten bolting time when treated at 4℃for one week;and within a certain range,the longer the 4℃treatment time,the better the vernalization effect.Different radish inbred lines had different performances to low temperature treatment.[Conclusions]This study provides a scientific basis for the theoretical research on vernalization of radish.
基金Supported by Taishan Industrial Leader talent Project in Shandong Province(TSCX2023006156)Modern Agricultural Industry System in Beijing(BAIC01-2023).
文摘There are many varieties of vegetables in Cruciferae,which have a wide distribution and occupy an important position in the global vegetable industry.The bolting period is a crucial stage in the growth cycle of cruciferous plants,which directly affects the yield and quality of vegetable crops.This paper summarized the research progress on the physiological and biochemical characteristics,molecular genetic mechanisms and molecular markers of the flowering and bolting traits in cruciferous vegetables,in order to provide new ideas for revealing the regulatory mechanisms of flowering and bolting in cruciferous vegetables and to provide reference for the breeding of new varieties of cruciferous vegetables that are resistant to flowering.
