The Construction Techniques Of Skid Resistance Plers Of Longtang Shan No.3 Bridge In Neikun Railway

The Longtang Shan No.3 Bridge is situated at DK286+042 district of the newly built Neikun Railway. It was originally designed with 1270m length , which was located on a huge rock pile with a range of distribution of DK285+490-DK286+760. As a large-scale earth slide occurred during the embankment filling, the design was changed into transiting with a bridge after abundant demonstrations. The design adopted the scheme of skid resistance piers, which combined the functions of skid resistance piles and piers. Under the condition of tough geology, enriched groundwater and large lonestones in sliding mass, the largeness of the excavating area, the deepness of the excavation, the tightness of the term of works and the difficulties of the construction doubtlessly make the skid resistance piers the first pattern in the history of internal railway constructions. According to different geological conditions, we duly changed the methods of excavating and supporting, thus we successfully got through the deep and low sliding surfaces, and ensured the term of works, security and the quality of the project. The scheme is an audacious effort in the range of railroad engineering. As the project is successfully completed, the experiences of the designing and the construction techniques will provide precious paradigms for the prospective road and railroad constructions under poor geologies. The design and the execution are in possession of important theoretical and social significance. By the way of studying the changes of design, the key techniques, the testing of mixing ratio of large-sized concrete and the construction monitoring of the Longtang Shan No.3 Bridge, the thesis expounds following aspects:(1) Based on summarizing the construction methods and experiences of internal large scale skid resistance piles, the paper detailed states and analyzes the proposed execution methods and the execution techniques of the Longtang Shan No.3 Bridge of Neikun Railway.(2) The excavating technology and the supporting system are the governing factors since they are complicated during the construction of the skid resistance]piers. Based on drawing on the well shaft excavations and supporting systems of the internal skid resistance piles, the project adopted micro seismic activity blasting excavation technique and informatization supporting method, made investigation and monitoring to the micro seismic activity blasting, and inspected the supporting system with surface strain indicator and cymometer, in order to supervise the construction.(3) Considering that large size concrete will produce a mass of hydration heat, the thesis introduces how to select the mixture ratio of the concrete to reduce the hydration heat and its test-mixing procedures, points out the 'double intermixing' technique of reducing hydration heat as well as other temperature dropping methods.(4) In order to comprehend profoundly about whether the massif slides and the speed of the sliding during the construction at DK286 district, as well as the lateral stressing complexion of the massif under the situations of rainy season and trains' mobile loading after the project's completion, we laid stress meter and straining meter in the main reinforcements and pier shaft concrete of the No.2 skid resistance pier, made monitoring test and analyzed the monitoring data.