Research On The Settlement Of The Whole Construction Process Of The Suspension Bridge Anchorage Caisson Foundation In Deep Silt Soft Soil

Large-scale anchorage caisson foundations have become the main type of anchorage foundations for long-span suspension bridges at present due to their large embedded depth,large rigidity,and strong bearing capacity.Relying on the practice of caisson engineering of Oujiang Beikou Bridge in Wenzhou,this paper focuses on the whole process of foundation construction of anchorage caisson in deep soft soil area.The deformation study of the construction process of the large-scale anchorage caisson foundation in the soft soil area is carried out.The main work and research results are as follows:1.Based on the monitoring data of land caisson and deepwater caisson of the same suspension bridge,the characteristics of sinking resistance distribution and sudden sinking behavior of caisson are compared and analyzed.The results show that the base resistance of deep water caisson increases with the immersion depth,and the base resistance of land caisson oscillates repeatedly with the change of mud suction in the sand pile composite foundation reinforcement area,and is not significantly affected by the depth of soil immersion;The maximum sidewall soil pressure of the caisson is generally located between the active soil pressure and the passive soil pressure,and both increase approximately linearly with the increase of the depth of soil immersion.The active soil pressure of 0.5～0.6 times can be used to estimate the maximum sidewall soil pressure of the caisson in the deep soft soil area.2.After the caisson is in place,the sensitivity of soil parameter in the calculation of the displacement of the anchor caisson is determined by sensitivity analysis,and the most sensitive parameter is the compressive modulus E_s1-2 of the bearing layer of the pebble layer.The soil parameters are inversely analyzed according to the sensitivity,and the soil parameters for the final calculation and analysis are obtained through the analysis of the calculation error.The calculation analysis considering the consolidation effect shows that the subsequent deformation after the anchor foundation sinks in place needs to consider the consolidation effect of the soil,especially the bearing layer.3.Under the influence of cable force,the horizontal displacement of the anchorage caisson foundation is significantly larger than the vertical displacement,and the soil stress level on the sidewall of the foundation is higher than its ultimate bearing capacity,which is the main cause of the foundation rotation.The horizontal displacement and inclination development pattern of the upper approach pier of the anchor caisson during the construction process is consistent with the development pattern of the inclination of the anchor foundation.Reasonable arrangement of construction procedures and advance the construction of the approach pier before the anchor construction can effectively reduce the horizontal displacement and inclination during the construction of the approach pier.