To overcome large deformation of deep phosphate rock roadways and pillar damage,a new type of constant-resistance large-deformation negative Poisson’s ratio(NPR)bolt that can withstand a high prestress of at least 13...To overcome large deformation of deep phosphate rock roadways and pillar damage,a new type of constant-resistance large-deformation negative Poisson’s ratio(NPR)bolt that can withstand a high prestress of at least 130 KN was developed.In the conducted tests,the amount of deformation was 200-2000 mm,the breaking force reached 350 KN,and a high constant-resistance pre-stress was maintained during the deformation process.A stress compensation theory of phosphate rock excavation based on NPR bolts is proposed together with a balance system for bolt compensation of the time-space effect and high NPR pre-stress.Traditional split-set rock bolts are unable to maintain the stability of roadway roofs and pillars.To verify the support effect of the proposed bolt,field tests were conducted using both the proposed NPR bolts and split-set rock bolts as support systems on the same mining face.In addition,the stress compensation mechanism of roadway mining was simulated using the particle flow code in three dimensions(PFC^(3D))-fast Lagrangian analysis of continua(FLAC^(3D))particle-flow coupling numerical model.On-site monitoring and numerical simulations showed that the NPR excavation compensation support scheme effectively improves the stress state of the bolts and reduces the deformation of the surrounding rock.Compared to the original support scheme,the final deformation of the surrounding rock was reduced by approximately 70%.These results significantly contribute to domestic and foreign research on phosphate-rock NPR compensation support technology,theoretical systems,and engineering practices,and further promote technological innovation in the phosphate rock mining industry.展开更多
Florence (Italy) is a worldwide well-known cultural historical city, with many outstanding monumental buildings visited every year by about 20M people, since 1982 the historical city center is under the UNESCO Patrona...Florence (Italy) is a worldwide well-known cultural historical city, with many outstanding monumental buildings visited every year by about 20M people, since 1982 the historical city center is under the UNESCO Patronage. Conservation of monumental buildings is subject to the principles of integrity and authenticity, in Italy recalled by the Ministry for Cultural Heritage 2011 rule, which defines the procedure for their seismic vulnerability evaluation. For that, the knowledge of the masonry structure is in need, and in lack of historical documentation on the design, only non destructive tests (NDT), or very low destructive tests, can be run on the masonry for acquiring this knowledge on its structure and consistence. For this purpose, we are largely using specific ground penetrating radar (GPR) technology, which is resulting highly performing in defining masonry structure and consistence. This paper summarizes selected case histories regarding the main Florentine historical monumental buildings: Palazzo Vecchio, Brunelleschi’s Cupola, Giotto’s Bell-Tower, and San Giovanni Baptistery. The correct interpretation of the GPR data requires knowledge about the masonry techniques of the age of construction, and local verification with micro drill-holes with video inspections, sonic and ultrasonic tests, in defining historical monumental buildings masonry structure and competence, static and dynamic behavior parameters and seismic vulnerability.展开更多
基金funding support from the National Natural Science Foundation of China(NSFC)(Grant Nos.41941018 and 52304111)the Program of China Scholarship Council(Grant No.202206430007).
文摘To overcome large deformation of deep phosphate rock roadways and pillar damage,a new type of constant-resistance large-deformation negative Poisson’s ratio(NPR)bolt that can withstand a high prestress of at least 130 KN was developed.In the conducted tests,the amount of deformation was 200-2000 mm,the breaking force reached 350 KN,and a high constant-resistance pre-stress was maintained during the deformation process.A stress compensation theory of phosphate rock excavation based on NPR bolts is proposed together with a balance system for bolt compensation of the time-space effect and high NPR pre-stress.Traditional split-set rock bolts are unable to maintain the stability of roadway roofs and pillars.To verify the support effect of the proposed bolt,field tests were conducted using both the proposed NPR bolts and split-set rock bolts as support systems on the same mining face.In addition,the stress compensation mechanism of roadway mining was simulated using the particle flow code in three dimensions(PFC^(3D))-fast Lagrangian analysis of continua(FLAC^(3D))particle-flow coupling numerical model.On-site monitoring and numerical simulations showed that the NPR excavation compensation support scheme effectively improves the stress state of the bolts and reduces the deformation of the surrounding rock.Compared to the original support scheme,the final deformation of the surrounding rock was reduced by approximately 70%.These results significantly contribute to domestic and foreign research on phosphate-rock NPR compensation support technology,theoretical systems,and engineering practices,and further promote technological innovation in the phosphate rock mining industry.
文摘Florence (Italy) is a worldwide well-known cultural historical city, with many outstanding monumental buildings visited every year by about 20M people, since 1982 the historical city center is under the UNESCO Patronage. Conservation of monumental buildings is subject to the principles of integrity and authenticity, in Italy recalled by the Ministry for Cultural Heritage 2011 rule, which defines the procedure for their seismic vulnerability evaluation. For that, the knowledge of the masonry structure is in need, and in lack of historical documentation on the design, only non destructive tests (NDT), or very low destructive tests, can be run on the masonry for acquiring this knowledge on its structure and consistence. For this purpose, we are largely using specific ground penetrating radar (GPR) technology, which is resulting highly performing in defining masonry structure and consistence. This paper summarizes selected case histories regarding the main Florentine historical monumental buildings: Palazzo Vecchio, Brunelleschi’s Cupola, Giotto’s Bell-Tower, and San Giovanni Baptistery. The correct interpretation of the GPR data requires knowledge about the masonry techniques of the age of construction, and local verification with micro drill-holes with video inspections, sonic and ultrasonic tests, in defining historical monumental buildings masonry structure and competence, static and dynamic behavior parameters and seismic vulnerability.
