An active application of a concrete track is expected for the future construction of railroads. For successful concrete track construction and operation in earthwork areas, the residual settlement should be reasonably...An active application of a concrete track is expected for the future construction of railroads. For successful concrete track construction and operation in earthwork areas, the residual settlement should be reasonably controlled by using an appro- priate method. The maintenance for excessive settlement is very difficult on the operating line because the maintenance method is very restrictive. The objective of this study is to introduce pressurized rapid-hardening cement grouting （PRCG） method to restore a subsided concrete track without any adverse effects on train operation. This method involves the use of special types of materials （very quick hardening and middle-hardening mortar）, compact grouting equipment, and a special construction process. In spite of the extremely restrictive environment, this method has been demonstrated to be very effective and reasonable through laboratory and field tests.展开更多
Invading track of chloride ions and chloride ion distribution rule in cement-based materials were investigated by partially soaking in 3.5% （mass fraction） NaCl solution and fully immerging in 3.5% and 5.0% （mass f...Invading track of chloride ions and chloride ion distribution rule in cement-based materials were investigated by partially soaking in 3.5% （mass fraction） NaCl solution and fully immerging in 3.5% and 5.0% （mass fraction） NaC1 solution, respectively, and relevant invading mechanisms were discussed. Results indicate that under full immerging condition, the invading track of chloride ions in cement mortar is similar to beeline that is vertical to chloride ion invading direction, and chloride ion content decreases rapidly with the increase of chloride ion invading depth. Under partial soaking condition, the invading track of chloride ion in cement mortar is similar to the shape of concave parabola, and chloride ion content decreases slowly along the lengthway direction of cement mortar samples in the distance of 20-80 mm from the bottom. Lots of chloride ions accumulate in cement mortar surface layer under the effect of capillary rise and evaporation and then invade cement mortar by diffusion effect. Under partial soaking condition, cement mortar is distinguished by four areas, i.e., immerging area, wet area, crystallization area and dry area.展开更多
In Greece extended cracking of twin-block concrete sleepers （ties） and fouling of the ballast-bed were observed with implied problems of gauge widening and deterioration of track＇s geometry. This led to a ten-year ...In Greece extended cracking of twin-block concrete sleepers （ties） and fouling of the ballast-bed were observed with implied problems of gauge widening and deterioration of track＇s geometry. This led to a ten-year investigation program, during which a new method was developed for the estimation of actions on track panel as well as of the pressures / stresses that develop under the seating surface of the sleeper on the ballast-bed. Results from the tests performed on the ballast used in the Greek network are also presented, conducted in laboratories in France, Austria, and Greece. The influence of the actions -static and mainly dynamic- on the track response and the stress and strain of the ballast-bed are also discussed as derived from the tests and theoretical analysis.展开更多
文摘An active application of a concrete track is expected for the future construction of railroads. For successful concrete track construction and operation in earthwork areas, the residual settlement should be reasonably controlled by using an appro- priate method. The maintenance for excessive settlement is very difficult on the operating line because the maintenance method is very restrictive. The objective of this study is to introduce pressurized rapid-hardening cement grouting （PRCG） method to restore a subsided concrete track without any adverse effects on train operation. This method involves the use of special types of materials （very quick hardening and middle-hardening mortar）, compact grouting equipment, and a special construction process. In spite of the extremely restrictive environment, this method has been demonstrated to be very effective and reasonable through laboratory and field tests.
基金Project(50678174) supported by the National Natural Science Foundation of China
文摘Invading track of chloride ions and chloride ion distribution rule in cement-based materials were investigated by partially soaking in 3.5% （mass fraction） NaCl solution and fully immerging in 3.5% and 5.0% （mass fraction） NaC1 solution, respectively, and relevant invading mechanisms were discussed. Results indicate that under full immerging condition, the invading track of chloride ions in cement mortar is similar to beeline that is vertical to chloride ion invading direction, and chloride ion content decreases rapidly with the increase of chloride ion invading depth. Under partial soaking condition, the invading track of chloride ion in cement mortar is similar to the shape of concave parabola, and chloride ion content decreases slowly along the lengthway direction of cement mortar samples in the distance of 20-80 mm from the bottom. Lots of chloride ions accumulate in cement mortar surface layer under the effect of capillary rise and evaporation and then invade cement mortar by diffusion effect. Under partial soaking condition, cement mortar is distinguished by four areas, i.e., immerging area, wet area, crystallization area and dry area.
文摘In Greece extended cracking of twin-block concrete sleepers （ties） and fouling of the ballast-bed were observed with implied problems of gauge widening and deterioration of track＇s geometry. This led to a ten-year investigation program, during which a new method was developed for the estimation of actions on track panel as well as of the pressures / stresses that develop under the seating surface of the sleeper on the ballast-bed. Results from the tests performed on the ballast used in the Greek network are also presented, conducted in laboratories in France, Austria, and Greece. The influence of the actions -static and mainly dynamic- on the track response and the stress and strain of the ballast-bed are also discussed as derived from the tests and theoretical analysis.
