Using Post-grouting Reinforcement Technique To Control The Settlement At The Back Of Bridge In Dian-lin Expressway

With the implementation of Development Strategy of West of China,the freeways in mountainous area get a deep development.At the same time the highway diseases are also come out because of the special geological conditions of there. By field survey, the"bumping at bridge-head"is one of the most usually freeway diseases, which makes the car bumping when getting across the bridge-head, and bring hidden danger. At the same time, its post treatment will cost a lot of as well as affect the traffic. This paper analyzed the cause from many aspect and also summarized the measures of haw to settle the problem at home and abroad. The application of using grouting reinforcement to control the settlement of bridge back in southwestern mountainous area was the key point of this paper.First of all, this paper rely on the project of settlement treatment reasearch of bridge back in dian-lin expressway. We choosed 3 model test point after field survey and take some rock and earth sample back, so as to get the identity parameter. The graded broken stone was the optimized backfill material.Secondly, many grouting material were studied in lab. Their identity properties such as fluidity,compressive strength,coaqulate time were analysed with the condition of different ratios. Through the test, the most suitable material and ratio was cement-fly ash, which obtained for the grouting reinforcement at the back of bridge of freeway in mountainous area. The best ratio of this material were water:cement:fly ash = 1.2:1:0.5,1.6:1:1 and 1.2:1:1.Then using numerical simulation technique, combined with the construction drawing, with the help of the parameters gotten from the test, the simulation models of the test points were builded. The numerical simulation calculated the settlemen with the condition of none special measure,setting up the approach slab, as well as grouting reinforcement. The settlemen in ranfang bridge without treatment,setting up the approach slab and grouting reinforcement were respectively 44.6cm,18.7cm and 2.5cm; The settlemen in pengjiahe major bridge without treatment,setting up the approach slab and grouting reinforcement were respectively 27.6cm,8.9cm and 3.9mm; The result for dazhuangzi left major bridge model were respectively 22.1cm,5.8cm and 2.6mm. Compared the calculation results, the grouting reinforcement could obtain the best effect.Finally, in the field test points, injecting grout through steel perforated pipe to reinforce the backfill area. The ranfang bridge test point adopted the plan of equal interval with variable depths grouting adding 8m approach slab; While, the pengjiahe major bridge test point adopted the plan of equal interval with variable depths grouting without adding approach slab. The dazhuangzi left major bridge test point adopted the plan of equal interval with variable depths grouting adding 5m approach slab. After grouting, we using surface wave velocity testing technique to inspect the grouting effect. At the same time another two usual methods were used. The wave velocity testing which were convenient economy and fast had obvious advantages.Until now, there were none"bumping at bridge-head"phenomenon in test points after about one year. Using post-grouting reinforcement technique to control the settlement of backfill had the merits of convenient,economy,effective, so it was worth popularizing.