| With the rapid development of the economy in the eastern coastal areas,the development and utilization of offshore tidal flats is increasing.Cofferdam and land reclamation is to build a dam on the thick layer of marine soft soil in the tidal flat to form an available land.However,the construction of the cofferdam and the presence of the post-construction dam will have long-term effects on the structure which is in the in the soft-soil area of the tidal flat,especially the existing near-bank bridge piles.This can be attributed to the rheological properties of marine sedimentary soft soil and the long-term effects of dam load.With the passage of time,the creep deformation of soft soil will cause additional stress and deformation to the near-deck pile foundation.This additional effect will lead to the safety accident of the dam close to the bridge structure.This article is based on the actual situation of the cofferdam in Taizhou area,and rely on the scientific research project of Zhejiang Provincial Communications Department,"Study on the Temporal and Spatial Characteristics and Countermeasures of the Influence of Cofferdams along the Beach on the Adjacent Bridge Piles"(2014H39).Through the investigation and analysis of the soft soil quality conditions in the relevant areas,using indoor experiments,finite element numerical simulation and real-time monitoring of the solid bridge pile foundation and adjacent soils,the dam construction work along the beach is studied systematically.The influence of the pile foundation and the treatment methods were discussed.The main contents include the following aspects.(1)Through literature search and investigation,the soft soils of Shanghai,Jiaxing,Hangzhou,Ningbo,Taizhou and Wenzhou in the southeast coastal areas were analyzed and summarized from five aspects:water content,compressibility,permeability,shear strength and sensitivity,then obtained the physical and mechanical indicators of the overall characteristics of the marine soil in the study area(Taizhou area).(2)Through the compression creep test of soft soil and improved soil in the mud-soil area,the corresponding creep characteristic curves are obtained,and the corresponding creep constitutive parameters are obtained by data fitting,which is the subsequent slow-sloping sea-coat cofferdam operation and subsequent the analysis of pile foundation deformation under long-term effects provides reliable parameters.(3)By establishing the dam-group pile-foundation analysis model and considering the creep characteristics of soft soil,the creep analysis under the construction of the dike and the post-loading load on the gently inclined sea-coating is carried out.The spatio-temporal law of pile foundation deformation at different locations(upstream and downstream and distance between piles and dykes)of the embankment with creep for a total of 10 years are obtained.(4)Based on the physical engineering,the geological survey report and the actual structure of the bridge,the monitoring plan for soil settlement,lateral displacement,pressure and horizontal level of the bridge foundation near the pile foundation of the bridge is established,and real-time monitoring is implemented.The monitoring results show that the soft soil of the seabed has a rheological movement with increasing time,and the lateral pressure of the bridge pile tends to increase due to the movement of the soil.(5)According to the space-time law of the cofferdam construction and the post-construction embankment on the pile foundation and the monitoring results of the actual project,the maximum displacement of the pile top near the embankment of the embankment is taken as the research object,and the comparison of various methods of pile foundation reinforcement is carried out.The feasibility analysis,the method of improving the near-pile soil in the form of mixing piles is proposed,and the numerical simulation method is used to compare and optimize the treatment schemes,and the corresponding optimization engineering measures are proposed. |
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