TiC-TiB2-NiAl composites were fabricated by self-propagating high temperature reaction synthesis（SHS） with Ti, B4C, Ni and Al powders as raw materials. The effects of NiAl content on phase constituents and microstru...TiC-TiB2-NiAl composites were fabricated by self-propagating high temperature reaction synthesis（SHS） with Ti, B4C, Ni and Al powders as raw materials. The effects of NiAl content on phase constituents and microstructures were investigated. The results show that the reaction products are composed of TiB2, TiC and NiAl. The content of NiAl increases with the adding of Ni＋Al in green compacts. TiB2, TiC and NiAl grains present in different shapes in the matrix, TiB2 being in hexagonal or rectangular shapes, TiC in spherical shapes, and NiAl squeezed into the gaps of TiC and TiB2 grains. With the increase of NiAl content, the grains of TiC-TiB2-NiAl composites are refined, their density and compressive strength are improved, and the shapes of TiC grains become spherical instead of irregular ones. Finally, the fracture mechanism of the composites transforms from intergranular fracture mode to the compounded fracture mode of intergranular fracture and transgranular fracture.展开更多
The reinforcement effects of geosynthetics in thick soft subsoil case and thin soft subsoil case are studied in this paper,and a Duncan Chang nonlinear numerical model based on the finite element method (FEM) is deve...The reinforcement effects of geosynthetics in thick soft subsoil case and thin soft subsoil case are studied in this paper,and a Duncan Chang nonlinear numerical model based on the finite element method (FEM) is developed.Moreover,an important conclusion that the thickness of soft subsoil affects greatly the geotechnical behavior of geosynthetic reinforced embankments is drawn.A series of embankment built on soft subsoil is calculated using the FEM program.The results of the computer program,such as the lateral displacements,settlements,and stress level and shear stresses in the subsoil,are presented in great detail and the comparison of those results disposes clearly the huge discrepancy of reinforce benefit between the thick subsoil embankment and thin subsoil embankment.Reinforcement mechanism of geosynthetics is also discussed in this paper and several conclusions are reached.This paper also gives recommendations for design.展开更多
The objective of this work is to compare the responses of geosynthetically-reinforced embankment and unreinforced embankment due to road widening by using the centrifuge model tests and a two-dimensional(2D) finite el...The objective of this work is to compare the responses of geosynthetically-reinforced embankment and unreinforced embankment due to road widening by using the centrifuge model tests and a two-dimensional(2D) finite element(FE) model. The measured and calculated responses of the embankment and foundation exposed to road widening include the settlement,horizontal displacement,pore water pressure,and shear stresses. It is found that the road widening changed the transverse slope of the original pavement surface resulting from the nonuniform settlements. The maximum horizontal movement is found to be located at the shoulder of the original embankment. Although the difference is small,it is clearly seen that the geosynthetic reinforcement reduces the nonuniform settlements and horizontal movements due to road widening. Thus the reinforcement reduces the potential of pavement cracking and increases the stability of the embankment on soft ground in road widening.展开更多
基金Projects(51072104,51272141)supported by the National Natural Science Foundation of ChinaProject(ts20110828)supported by Taishan Scholars Project of Shandong,China
文摘TiC-TiB2-NiAl composites were fabricated by self-propagating high temperature reaction synthesis（SHS） with Ti, B4C, Ni and Al powders as raw materials. The effects of NiAl content on phase constituents and microstructures were investigated. The results show that the reaction products are composed of TiB2, TiC and NiAl. The content of NiAl increases with the adding of Ni＋Al in green compacts. TiB2, TiC and NiAl grains present in different shapes in the matrix, TiB2 being in hexagonal or rectangular shapes, TiC in spherical shapes, and NiAl squeezed into the gaps of TiC and TiB2 grains. With the increase of NiAl content, the grains of TiC-TiB2-NiAl composites are refined, their density and compressive strength are improved, and the shapes of TiC grains become spherical instead of irregular ones. Finally, the fracture mechanism of the composites transforms from intergranular fracture mode to the compounded fracture mode of intergranular fracture and transgranular fracture.
文摘The reinforcement effects of geosynthetics in thick soft subsoil case and thin soft subsoil case are studied in this paper,and a Duncan Chang nonlinear numerical model based on the finite element method (FEM) is developed.Moreover,an important conclusion that the thickness of soft subsoil affects greatly the geotechnical behavior of geosynthetic reinforced embankments is drawn.A series of embankment built on soft subsoil is calculated using the FEM program.The results of the computer program,such as the lateral displacements,settlements,and stress level and shear stresses in the subsoil,are presented in great detail and the comparison of those results disposes clearly the huge discrepancy of reinforce benefit between the thick subsoil embankment and thin subsoil embankment.Reinforcement mechanism of geosynthetics is also discussed in this paper and several conclusions are reached.This paper also gives recommendations for design.
基金Project(200231800032) supported by Research on Transportation Construction in Western, China
文摘The objective of this work is to compare the responses of geosynthetically-reinforced embankment and unreinforced embankment due to road widening by using the centrifuge model tests and a two-dimensional(2D) finite element(FE) model. The measured and calculated responses of the embankment and foundation exposed to road widening include the settlement,horizontal displacement,pore water pressure,and shear stresses. It is found that the road widening changed the transverse slope of the original pavement surface resulting from the nonuniform settlements. The maximum horizontal movement is found to be located at the shoulder of the original embankment. Although the difference is small,it is clearly seen that the geosynthetic reinforcement reduces the nonuniform settlements and horizontal movements due to road widening. Thus the reinforcement reduces the potential of pavement cracking and increases the stability of the embankment on soft ground in road widening.
