Rigid barrier is a straightforward and effective countermeasure widely used for mitigating debris flow.However,in current designs,it remains unclear how to optimize the rigid barrier to enhance its mechanical properti...Rigid barrier is a straightforward and effective countermeasure widely used for mitigating debris flow.However,in current designs,it remains unclear how to optimize the rigid barrier to enhance its mechanical properties.Therefore,this study investigates the influence of the shape of the upstream face of the rigid barrier,referred to as the'barrier shape',on the impact dynamics of debris flow entraining a boulder onto rigid barrier.This study employs a coupled numerical approach involving smoothed particle hydrodynamics(SPH),the discrete element method(DEM),and the finite element method(FEM).The simulation results demonstrate that the barrier shape can affect the mechanical properties of the rigid barrier by altering the interaction mode between the debris flow and the barrier.Compared to vertical and slanted barriers,a curved barrier exhibits superior mechanical properties when subjected to debris flow impact.Furthermore,reducing the slope of the upstream face appropriately proves to be an effective method for enhancing the impact resistance of slanted barriers.The relevant findings from this study can serve as valuable references for the structural optimization of rigid barriers.展开更多
Shrinkage-induced cracking is a common issue in concrete structures,where the formation of cracks not only affects the aesthetic appearance of concrete but also potentially reduces its durability and strength.In this ...Shrinkage-induced cracking is a common issue in concrete structures,where the formation of cracks not only affects the aesthetic appearance of concrete but also potentially reduces its durability and strength.In this study,the effect of ceramsite sand addition on the properties of a ternary system of cement-ground granulated blast furnace slag(GGBFS)-phosphogypsum(PG)is investigated.In particular,the fluidity,rheology,hydration heat,compressive strength,autogenous shrinkage,and drying shrinkage of the considered mortar specimens are analyzed.The results indicate that an increase in PG content leads to a decrease in fluidity,higher viscosity,lower exothermic peak,and lower compressive strength.However,the shrinkage of the mortar specimens is effectively compensated.The incorporation of internal curing water from ceramsite sand improves fluidity,decreases both yield stress and viscosity,enhances the degree of hydration,and induces mortar expansion.However,the inferior mechanical properties of the ceramsite sand generally produce a decrease in the compressive strength.展开更多
The chloride permeability and microstructure of persulphated phosphogypsum-slag cement concrete（PPSCC）, the Portland slag cement concrete（PSCC） and ordinary Portland cement concrete（OPCC） were investigated compa...The chloride permeability and microstructure of persulphated phosphogypsum-slag cement concrete（PPSCC）, the Portland slag cement concrete（PSCC） and ordinary Portland cement concrete（OPCC） were investigated comparatively. Some test methods were used to evaluate the chloride permeability and explain the relationship between the permeability and microstructure of concrete. The results show that the resistance to chloride penetration in PPSCC is significantly better than that in OPCC, the reasons are as follows： 1） the slag in PPSCC is activated by clinker（alkali activation） and phosphogypsum（sulfate activation）, forming more low Ca/Si C-S-H gel and gel pores below 10 nm than OPCC, improving the resistance to chloride penetration; 2） the hydration products of PPSCC have a much stronger binding capacity for chloride ions; and 3） in the same mix proportion, PPSCC has a better workability without large crystals calcium hydroxide in the hydration products, the interfacial transition zone（ITZ） is smoother and denser, which can cut off the communicating pores between the pastes and aggregates.展开更多
The limit span of self-anchored cable-stayed suspension bridge is deduced.The relations among the geometrical parameters,loads and material characteristics are also analyzed.Based on the material strength and commonly...The limit span of self-anchored cable-stayed suspension bridge is deduced.The relations among the geometrical parameters,loads and material characteristics are also analyzed.Based on the material strength and commonly used materials,the limit spans of self-anchored cable-stayed suspension bridges with concrete girder or steel girder under vertical static load are discussed in detail.The corresponding upper limit spans and the effect of the factors on the span are given.The results indicate that increasing rise-span ratio,height-span ratio and cable-stayed segment length or reducing the second dead load could increase the cooperation system span.展开更多
This paper presents an analytical model to solve the linear wave diffraction problem by arrays of bottom-mounted cylinders with arbitrary smooth cross-section.Based on the assumption of ideal fluid and potential theor...This paper presents an analytical model to solve the linear wave diffraction problem by arrays of bottom-mounted cylinders with arbitrary smooth cross-section.Based on the assumption of ideal fluid and potential theory,the unknown coefficients of total velocity potential can be solved by system of linear equations,which are obtained from the boundary conditions.The accuracy of the present method is verified by comparing it with the numerical tool in terms of the wave force and wave mn-up.Multiple cylinders with different configurations are tested,the cross-section of which is circular with cosine perturbation.The results show that the proposed method could obtain an accurate prediction of the wave action with multiple cylinder problems.Finally,the diffraction wave is investigated on arrays of bottom-mounted cylinders with different cross-section and layout.The near-trapping problem with effects of the multi-body interaction are also investigated.展开更多
Based on 1D infinite element theory,the coordinate transformation and shape function of 3D point-radiation 4-node infinite elements were derived.They were coupled with 8-node finite elements to compute the compressive...Based on 1D infinite element theory,the coordinate transformation and shape function of 3D point-radiation 4-node infinite elements were derived.They were coupled with 8-node finite elements to compute the compressive deformation of the prestressed anchor segment.The results indicate that when the prestressed force acts on the anchor segment,the stresses and displacements in the rock around the anchor segment are concentrated in the zone center with the anchor axis and are subjected to exponential decay.Therefore,the stresses and the displacement spindles are formed.The calculation results of the infinite element are close to the theoretical results.展开更多
基金supported by the National Key Research and Development Program of China(No.2022YFC3005704)the National Natural Science Foundation of China(No.42277143)+3 种基金the Natural Science Foundation of Sichuan Province(2024NSFSC0100)the Fundamental Research Funds for the Central Universities(No.2682023ZTPY022)Projects of Science and Technology Research and Development Program of China Railway Group Limited(2021-Special Class-03)the Natural Science Foundation of Sichuan Province(2024NSFSC0834).
文摘Rigid barrier is a straightforward and effective countermeasure widely used for mitigating debris flow.However,in current designs,it remains unclear how to optimize the rigid barrier to enhance its mechanical properties.Therefore,this study investigates the influence of the shape of the upstream face of the rigid barrier,referred to as the'barrier shape',on the impact dynamics of debris flow entraining a boulder onto rigid barrier.This study employs a coupled numerical approach involving smoothed particle hydrodynamics(SPH),the discrete element method(DEM),and the finite element method(FEM).The simulation results demonstrate that the barrier shape can affect the mechanical properties of the rigid barrier by altering the interaction mode between the debris flow and the barrier.Compared to vertical and slanted barriers,a curved barrier exhibits superior mechanical properties when subjected to debris flow impact.Furthermore,reducing the slope of the upstream face appropriately proves to be an effective method for enhancing the impact resistance of slanted barriers.The relevant findings from this study can serve as valuable references for the structural optimization of rigid barriers.
基金funded by the China Railway Major Bridge Engineering Group Co.,Ltd.,Project(2023-48-Key Project).
文摘Shrinkage-induced cracking is a common issue in concrete structures,where the formation of cracks not only affects the aesthetic appearance of concrete but also potentially reduces its durability and strength.In this study,the effect of ceramsite sand addition on the properties of a ternary system of cement-ground granulated blast furnace slag(GGBFS)-phosphogypsum(PG)is investigated.In particular,the fluidity,rheology,hydration heat,compressive strength,autogenous shrinkage,and drying shrinkage of the considered mortar specimens are analyzed.The results indicate that an increase in PG content leads to a decrease in fluidity,higher viscosity,lower exothermic peak,and lower compressive strength.However,the shrinkage of the mortar specimens is effectively compensated.The incorporation of internal curing water from ceramsite sand improves fluidity,decreases both yield stress and viscosity,enhances the degree of hydration,and induces mortar expansion.However,the inferior mechanical properties of the ceramsite sand generally produce a decrease in the compressive strength.
基金Funded by the National High Technology Research and Development Program of China(863 Program)(No.2012AA06A112)
文摘The chloride permeability and microstructure of persulphated phosphogypsum-slag cement concrete（PPSCC）, the Portland slag cement concrete（PSCC） and ordinary Portland cement concrete（OPCC） were investigated comparatively. Some test methods were used to evaluate the chloride permeability and explain the relationship between the permeability and microstructure of concrete. The results show that the resistance to chloride penetration in PPSCC is significantly better than that in OPCC, the reasons are as follows： 1） the slag in PPSCC is activated by clinker（alkali activation） and phosphogypsum（sulfate activation）, forming more low Ca/Si C-S-H gel and gel pores below 10 nm than OPCC, improving the resistance to chloride penetration; 2） the hydration products of PPSCC have a much stronger binding capacity for chloride ions; and 3） in the same mix proportion, PPSCC has a better workability without large crystals calcium hydroxide in the hydration products, the interfacial transition zone（ITZ） is smoother and denser, which can cut off the communicating pores between the pastes and aggregates.
基金This work was supported by the West Transportation Construction Projects Foundation of the Ministry of Communications(No.200631882350).
文摘The limit span of self-anchored cable-stayed suspension bridge is deduced.The relations among the geometrical parameters,loads and material characteristics are also analyzed.Based on the material strength and commonly used materials,the limit spans of self-anchored cable-stayed suspension bridges with concrete girder or steel girder under vertical static load are discussed in detail.The corresponding upper limit spans and the effect of the factors on the span are given.The results indicate that increasing rise-span ratio,height-span ratio and cable-stayed segment length or reducing the second dead load could increase the cooperation system span.
基金Project supported by the National Nature Science Foundation of China(Grant Nos.51725801,U 1834207).
文摘This paper presents an analytical model to solve the linear wave diffraction problem by arrays of bottom-mounted cylinders with arbitrary smooth cross-section.Based on the assumption of ideal fluid and potential theory,the unknown coefficients of total velocity potential can be solved by system of linear equations,which are obtained from the boundary conditions.The accuracy of the present method is verified by comparing it with the numerical tool in terms of the wave force and wave mn-up.Multiple cylinders with different configurations are tested,the cross-section of which is circular with cosine perturbation.The results show that the proposed method could obtain an accurate prediction of the wave action with multiple cylinder problems.Finally,the diffraction wave is investigated on arrays of bottom-mounted cylinders with different cross-section and layout.The near-trapping problem with effects of the multi-body interaction are also investigated.
文摘Based on 1D infinite element theory,the coordinate transformation and shape function of 3D point-radiation 4-node infinite elements were derived.They were coupled with 8-node finite elements to compute the compressive deformation of the prestressed anchor segment.The results indicate that when the prestressed force acts on the anchor segment,the stresses and displacements in the rock around the anchor segment are concentrated in the zone center with the anchor axis and are subjected to exponential decay.Therefore,the stresses and the displacement spindles are formed.The calculation results of the infinite element are close to the theoretical results.
