Study On Application And Construction Organization Optimization Of Pile Foundation Chemical Polymer Mud In Lhasa-Nyingchi Railway

The geological climate conditions of Lhasa to Nyingchi railway is complex,which located in the southeast of Qinghai Tibet Plateau,Southern Tibet Valley among the Gangdise Mountains and Nyenchen Tanglha Mountains and Himalayas Mountains.The middle reaches of the Brahmaputra river,the altitude is around 2800~3700m.Firstly,the length of bridges and tunnels are about 303.57 km between Lhasa to Nyingchi railway,which accounted for 75.17% of the total length.This brings difficulties to the construction of bridge pile foundations.Secondly,due to the impact of plateau climate and environmental conditions,the construction organization is also influenced.Therefore,research on the issues which encountered in pile foundation construction of Lhasa to Nyingchi railway bridges and optimized the construction organization,are extremely important and urgent for providing technical guidance of the construction and management in Qinghai-Tibet Plateau.According to the geological and hydrological conditions along Lhasa to Nyingchi railway,the effects of different additives on the chemical polymer mud were studied.The results showed that the specific density of the slurry increased firstly with the increase of the polymer additive content.After that,it decreased.The viscosity and the sand content increased linearly with the additive content.Finally the optimum content of the polymer additive is 0.05%.According to the engineering experience,the concrete construction process of chemical polymer slurry is described,and a good mud construction process is established.In the construction of Lhasa-Nyingchi railway,due to the influence of climate and environment along the line,the construction process of bridge pile foundation and the construction organization have negative effect.The construction process of bored pile is studied.The indicators of the inspection and testing methods are illustrated.Finally,combined with the engineering practice,this paper studies the optimization management of construction organization,improves the construction efficiency,and ensures the construction quality.According to the characteristics of climate and environment,the construction characteristics of different seasons are analyzed,which can ensure the smooth development of the project.