Analysis of immersed tunnel settlement under complex load and multiple kinds of compound foundations

Abstract

The silt typed soil thickness is up to 3~18m laying at bottom of foundation trench of ramp section at west island of SZ-Link and the surface silt is of extremely low strength subject to the influence of sand disturbance. The island cut and cover section tunnel foundation is improved with PHC and the settlement is relatively small. To accommodate the coordinated deformation of the immersed tunnel the soft foundation of the tunnel needs special treatment. Through options comparison and selection, the solution for foundation of tunnel element E1 is advance gravel cushion and compacted blocky stone layer and DCM outside the island and high pressurized jet grouting pile in the island. To accurately analyze the settlement characteristics of the element E1, determine its settlement amount and to achieve smooth rigidity transition of immersion tunnel and cut and cover section the settlement analysis of element E1 under complex loads and multiple kinds of foundations were carried out in combination with testing researches of all kinds of foundations. The primary research work comprises: (1) conduction of laboratory model experiment of gravel cushion, blocky stone compaction experiment, DCM laboratory triaxial test and provision of deformation computation parameters for given different foundation improvement solutions; (2) conduction of 3D finite element numerical analysis for element E1, analysis of immersed tunnel settlement deformation characteristics and provision of the law of E1 settlement distribution.