Application Techniques Of Prestressed Concrete Pipe Pile For Widened Expressway

Construction of widening expressway is different from that of new road projects, particularly in the deep soft soil. Incoordinate deformation between the existing subgrade and the widening one is difficult to control and the technology of improving subgrade ability is very important. Therefore, apart from design viewpoint, we should also focuse on the construction of widened road about special requirements of its construction technology and quality control.Prestressed concrete pipe pile which is used in the recent years is a type of precast concrete pile. This type of pile has many advantages, such as simple technique, better quality, low cost and convenient detection, so it has been widely used in geotechnical engineering. Though with the above merits, its squeezing effect and soil plugging effect of pile driving still need to be further researched, and its design theory and construction technique need to be further perfected. So the study on prestressed concrete pipe pile is of great theoretical and practical significance.On the basis of Lian-He widening expressway project, the load-carrying capacity mechanism of prestressed pile has been analyzed in this paper, and the causes and mechanics of pile soil plug has been discussed. Design percept, prestressed pile technical programs, construction preparation, static-stressed construction technology of prestressed piles have been discussed and analyzed. In order to guarantee its quality, discussions on key quality control points and assurance measures have been carried out and some common problems have been solved by combining entities pile construction works. It was shown by the late quality detection that soft subgrade dealt with piles can completely meet the design requirements; the sedimentations of culvert and subgrade are less than 3cm after construction. There is no longitudinal crack on the joints between the existing subgrade and the widening one. When prestressed piles are built in the road sideway where height of filled subgrade soil is more than 3.5m, they can prevent old subgrade sliding and there is no subgrade slide due to construction vibration.Therefore, through entity design and construction, the construction technology and control measures of prestressed concrete piles in widening expressway have been basically mastered.