| With the continuous development of China’s economy and society,the scale of urban infrastructure construction is gradually expanding,and the demand for manhole covers is increasing.The manhole cover is equivalent to the "gatekeeper" of urban underground space and plays an important role in the normal operation of urban underground pipelines.At present,cast iron manhole covers and concrete manhole covers are widely used in municipal engineering construction.Both of them have high bearing capacity,but the corrosion resistance and toughness of cast iron manhole covers are poor,which affects the service life of manhole covers;The traditional concrete manhole cover is easy to crack and collapse during use,and its impact resistance is poor.Therefore,designing a composite manhole cover with good comprehensive use performance and mechanical properties has become a hot research direction in the field of manhole cover research.This paper is committed to studying the mechanical characteristics and deformation law of composite manhole cover with basalt fiber as reinforcing fiber and unsaturated polyester resin as matrix under load.The main research work and results are as follows:(1)Through the two diameter of 700 mm resin reinforced manhole covers,two diameters of 700 mm basalt fiber modular plastic reinforced manhole covers,two diameters of 800 mm basalt fiber modular plastic reinforced manhole covers,two diameters of 700 mm basalt fiber lamellar molded plastic unreinforced manhole covers and two diameters of 700 mm The static loading test of mm basalt fiber sheet molded plastic reinforced manhole cover was carried out,and the load-deflection curve,load-strain curve and failure state of various manhole covers were compared and analyzed.The test results show that the average ultimate load of resin reinforced manhole cover is 118.5k N;The average ultimate load of the aggregate reinforced manhole cover with a diameter of 700 mm is 171 k N;The average ultimate load of the aggregate reinforced manhole cover with a diameter of 800 mm is 188.5 k N;The average ultimate load of sheet unreinforced manhole cover is 123 k N;The average ultimate load of sheet reinforced manhole cover is 202.5k N,and the bearing capacity is the best.According to the load-deflection curve,the rigidity of basalt fiber sheet reinforced manhole cover is the largest,and its deformation value is the smallest under the same load.According to the damage state of the manhole cover,the reinforced rib at the bottom of the manhole cover with fiber has small cracks,which are mainly distributed within the load area.The ductility of the resin manhole cover is the worst,the crack development speed is the fastest,and the crack distribution is the widest and the crack width is the largest.The bonding strength between basalt fiber and matrix,the content,strength and distribution of basalt fiber are the key factors to determine the cracking resistance of basalt fiber composites.(2)The tensile property test and bending property test of basalt fiber sheet molding compound are carried out.The research shows that the average elongation at break of the tensile specimen is 1.16%,the average tensile strength is 38.3 MPa,and the average tensile elastic modulus is 3.043 GPa.The load displacement curve of the tensile test is approximately linear.The specimen is directly pulled off at last,and the basalt fiber is pulled out of the matrix and pulled off;The average bending strength is 117.44 MPa and the average flexural elastic modulus is 8.993 GPa.At the last failure,there are small cracks on the tensile surface of the bending specimen,but the basalt fiber at the crack is not broken,showing good flexural performance.(3)The numerical simulation calculation of the well cover is carried out by using the finite element software ANSYS,which shows the feasibility of the finite element software,and further analyzes the stress influencing factors of the well cover.It is found that increasing the thickness of the face plate,the height and width of the reinforcing rib will improve the ultimate load value and the ability to resist deformation of the well cover,and the lifting effect of increasing the face plate of the well cover is the most obvious.The effect of increasing the height of the rib is not different from that of increasing the thickness of the face plate,and the lifting effect of increasing the width of the rib is the least significant;Under the same level load,with the increase of the panel thickness,rib height and rib width of the well cover,the reduction of the maximum deflection value of the well cover center will be smaller and smaller.(4)In this paper,the technology and economy of the reclaimed resin composite material manhole cover,cast iron manhole cover,steel fiber concrete manhole cover and basalt fiber composite material manhole cover,which are commonly used in municipal road construction,are compared and analyzed,and the social benefit and application prospect of basalt fiber are expounded.It shows that basalt fiber composite material inspection manhole cover has good mechanical properties and comprehensive performance,from the long-term planning,the manhole cover has a higher cost performance.Basalt fiber and its composites is the representative of green building materials industry to a certain extent,promote the transport and construction industries such as energy conservation and emissions reduction and low carbon green sustainable development,promote the transformation and upgrading of China building materials industry,research and development of basalt fiber resource reasonably to promote basaltic mass production in our country has the vital significance. |
PDF Full Text Request