ANALYSIS OF THE PROTECTIVE EFFECTS OF ISOLATED PILES WHEN SUBWAY TUNNEL CONSTRUCTION CROSSING THE EXISTING HIGH-SPEED RAILWAY BRIDGE FOUNDATIONS

Due to the impact of the adjacent construction, the high speed railway is facing the increasingly serious security, environmental and sustainable development issues. The deformation of bridge pile foundations and abutments under without or with isolated piles conditions was studied by using numerical simulation and field monitoring, when a new metro tunnel passing across the existing high-speed railway. Then, the protective effects of the isolated piles was assessed and the suitable depth and length of isolation piles were presented. The results show that isolation piles can effectively control the deformation of bridge piles and abutments. When using isolated piles, vertical and lateral displacement of bridge piles can decrease more than 20%,respectively. The depth of the isolated piles should be taken as 1.2-1.4 times of the length of bridge piles. The longitudinal length of the isolated pile wall should take 2.0 times of the length of bridge abutment.