The sideward permafrost along the Qinghai-Tibet Highway (QTH) contains massive ground-ice and is at a relatively high temperature.Under the influence of the steady increase of human activities,the permafrost environme...The sideward permafrost along the Qinghai-Tibet Highway (QTH) contains massive ground-ice and is at a relatively high temperature.Under the influence of the steady increase of human activities,the permafrost environment has been changed greatly for a long time.At present,the permafrost becomes warm and rapidly degenerates,including the decline of the permafrost table,rising of the ground temperature,shortening of the length of frozen section,and extension of range of melting region.Some thaw hazards (e.g.thaw slumping and thermokarst pond) have widely occurred along both sides of the roadbed.In addition,due to the incomplete construction management,the vegetation adjacent to the highway is seriously damaged or eradicated,resulting in the land desertification and ecosystem out of balance.The dust,waste and garbage brought by drivers,passengers,maintenance workers,and transportations may also pollute the permafrost environment.展开更多
The paper presents examples of technological designs for concrete placement in road bridges constructed during the S5/S 10 expressway extension in Poland. The project included eight concrete or composite bridge struct...The paper presents examples of technological designs for concrete placement in road bridges constructed during the S5/S 10 expressway extension in Poland. The project included eight concrete or composite bridge structures with different numbers of decks. The concrete placement technology is presented for the following bridge decks： slabs cast-in-situ, composite with precast or VFT （prefabricated composite beam） beams and mixed with cast in situ slabs and VFT-WIB （filler beam） beams. Continuous concrete placement was adopted for almost all the bridge superstructures except the mixed-type decks where construction joints were necessary. To control shrinkage, formwork deformations and existing restraints, the concrete was poured in layers and in stages. The design pace of concrete placement was moderate to be regulated at site without compromising safety and quality. The placement methods enabled both efficient and safe concrete pours.展开更多
Self-compacting concrete （SCC） is defined so that no vibration is necessary for the compaction. The main criteria of producing SCC have to satisfy the following characteristics [1, 2, 3]： （1） Ability to flow into...Self-compacting concrete （SCC） is defined so that no vibration is necessary for the compaction. The main criteria of producing SCC have to satisfy the following characteristics [1, 2, 3]： （1） Ability to flow into and completely fill complex forms under its own weight; （2） Ability to pass through and bond to congested reinforcements; （3） High resistance to aggregate segregation. Self-compacting concrete presents a significant sign in improving the product quality and efficiency of the building industry. It also enhances the working conditions and the quality and appearance of concrete. Japan has been used self-compacting concrete in bridge, building and tunnel construction since the early 1990s. In the last decade, SCC has been produced a high potential for greater acceptance and wider applications in highway bridge construction in the Europe and U.S.. However, till now, there is no application of SCC in the construction industry in Egypt. Therefore, the main objective of this research is to produce SCC by using the locally available materials in our region such as basalt, gravel, sand, limestone powder and silica fume. Experimental programme was designed to characterize the properties of fresh and hardened SCC. It comprises different concrete mixes thbricated with different types and percentages of constituent materials. Three full-scale reinforced concrete beams were fabricated from the SCC mixes and tested under flexure. For the purpose of comparison, an extra RC beam was made of conventional normal concrete to serve as a reference beam. This study, in general, demonstrated that the applications of SCC in construction industry oiler products with enhanced characteristics as well as could be economical.展开更多
基金Project(KZCX2-YW-Q03-04) supported by the Important Orientation Projects of the Chinese Academy of SciencesProject(41030741) supported by the National Natural Science of ChinaProject(2010CB434813) supported by the National Basic Research Program of China
文摘The sideward permafrost along the Qinghai-Tibet Highway (QTH) contains massive ground-ice and is at a relatively high temperature.Under the influence of the steady increase of human activities,the permafrost environment has been changed greatly for a long time.At present,the permafrost becomes warm and rapidly degenerates,including the decline of the permafrost table,rising of the ground temperature,shortening of the length of frozen section,and extension of range of melting region.Some thaw hazards (e.g.thaw slumping and thermokarst pond) have widely occurred along both sides of the roadbed.In addition,due to the incomplete construction management,the vegetation adjacent to the highway is seriously damaged or eradicated,resulting in the land desertification and ecosystem out of balance.The dust,waste and garbage brought by drivers,passengers,maintenance workers,and transportations may also pollute the permafrost environment.
文摘The paper presents examples of technological designs for concrete placement in road bridges constructed during the S5/S 10 expressway extension in Poland. The project included eight concrete or composite bridge structures with different numbers of decks. The concrete placement technology is presented for the following bridge decks： slabs cast-in-situ, composite with precast or VFT （prefabricated composite beam） beams and mixed with cast in situ slabs and VFT-WIB （filler beam） beams. Continuous concrete placement was adopted for almost all the bridge superstructures except the mixed-type decks where construction joints were necessary. To control shrinkage, formwork deformations and existing restraints, the concrete was poured in layers and in stages. The design pace of concrete placement was moderate to be regulated at site without compromising safety and quality. The placement methods enabled both efficient and safe concrete pours.
文摘Self-compacting concrete （SCC） is defined so that no vibration is necessary for the compaction. The main criteria of producing SCC have to satisfy the following characteristics [1, 2, 3]： （1） Ability to flow into and completely fill complex forms under its own weight; （2） Ability to pass through and bond to congested reinforcements; （3） High resistance to aggregate segregation. Self-compacting concrete presents a significant sign in improving the product quality and efficiency of the building industry. It also enhances the working conditions and the quality and appearance of concrete. Japan has been used self-compacting concrete in bridge, building and tunnel construction since the early 1990s. In the last decade, SCC has been produced a high potential for greater acceptance and wider applications in highway bridge construction in the Europe and U.S.. However, till now, there is no application of SCC in the construction industry in Egypt. Therefore, the main objective of this research is to produce SCC by using the locally available materials in our region such as basalt, gravel, sand, limestone powder and silica fume. Experimental programme was designed to characterize the properties of fresh and hardened SCC. It comprises different concrete mixes thbricated with different types and percentages of constituent materials. Three full-scale reinforced concrete beams were fabricated from the SCC mixes and tested under flexure. For the purpose of comparison, an extra RC beam was made of conventional normal concrete to serve as a reference beam. This study, in general, demonstrated that the applications of SCC in construction industry oiler products with enhanced characteristics as well as could be economical.
