| The expressway splicing and widening project is an effective resolution to backward traffic environment restricting rapidly developing economics, regardless the correlative theory and practice are quite few in collapsible loess area in West China. In this paper, according to the Xian—Baoji expressway splicing and widening project that had been built for decade years, the author put forward alternatives during each working procedure of expressway splicing and widening project, offered corresponding methods of controlling, thus providing guiding experience of design and construction for these projects.(1) The expressway splicing and widening project should be started with eliminating collapsibility loess, and each working procedure be carried out all the time to eliminate or lessen the differential settlement. Differential settlement had been eliminating constantly to minimum. The main measures are:dynamic compaction, composite foundation, cushion, excavation step in the roadbed splicing parts, and value for engineering of reinforced embankment with geotextile.(2) In the structures splicing construction, it must be fully considered that the differential settlement between the old and the new structures had been generated because of the difference of working time and the difference of applied load. In order to solve the differential settlement, some measures must be taken such as foundation treatment, reinforcing the splice joint, and allow enough time as free settlement period for the new structures. The project of joining structure abutment backfill should be reinforced by geocell Wedged-shaped Flexible Slab, which is a new technology to treat bridge bump and eliminate the differential settlement in embankment.(3)The pavement structure layer should survey the disease of old pavement before execution of works, and take different steps aimed at different disease, cutting the some of the layer when necessary and to construction with the new one together. In the construction, should reinforce the splicing construction of pavement structure layer by PYK,and slight-cutting the old pavement structure layer, rebuild the layer when surfacing the new, not keep the joint, make the waterproof and usability of layer be efficacious.(4)The expressway reconstructed and windened is not only building a new highway and to split joint with the old, but also to maintenance the imperfection in the foundation, structure and pavement layer of old expressway. As this,during the construction period must to conduct an investigation in the foundation, structure and pavement layer, take the steps to maintenance the different imperfection aimed at different disease,and to optimize the design of construct and interchange based on the service condition.(1) Based on the characteristic of expressway reconstructed and windened construction—"operation and meanwhile construction ", the construction machinery and technology should be choosey choosy, and enhance the safety and environment measure. For the reason on account of the traffic facility operation should been effected by the construction, so at the begining, must work out the traffic control project in order to lower the effected to less and ensure the construction success. The traffic control adopt three kinds of measures,as layer control, line control and point control, formulate the force control and limiting-velocity project based on the traffic condition of ambitus province and region, and the measures lessen the construction influence by the traffic facility operation. During the construction, adopt the lower noise,umweltfreundlich and slight vibration construction technology and machine,to minimize the influence to the traffic facility operation.In this paper, the author not only summarized experiences of practical project, but also put forward guiding methods in expressway splicing and widening project in collapsible loess area of West China.. |
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