Research On Deformation Control Of Soft Soil Foundation Reinforced By Prestressed Pipe Pile In Highway

With the promotion of China’s “the Belt and Road” and “transportation power”strategies,the significance of transportation infrastructure construction for achieving the country’s goal of becoming a modern power and promoting social and economic development is becoming increasingly prominent.However,constructing highways and railways in soft soil areas requires appropriate foundation treatment measures to prevent instability and damage during construction and operation.Although there are mature foundation treatment methods available,such as the drainage consolidation method and rigid pile composite foundation,most of the existing research focuses on evaluating embankment performance under a certain type of foundation treatment,and there are few comparative studies of engineering examples with similar geological conditions and embankment characteristics.Additionally,existing design methods of embankment piles need review to avoid gradual destabilization and failure of highway embankment slopes on soft soil foundations.This paper provides a comprehensive review of domestic and foreign research,and examines a highway project in Guangdong Province.It considers soft soil creep,graded embankment filling,and pile-soil interaction,and conducts on-site long-term monitoring and two-dimensional finite element numerical simulation of the reinforcement effect and mechanism of bagged sand wells and PHC pipe piles for treating marine soft soil foundation.The main work involves:(1)Introducing the engineering application requirements of rigid pile reinforcement for soft soil foundation and reviewing the research status of the most typical drainage consolidation method and composite foundation method in the field of soft soil foundation treatment in geotechnical engineering at home and abroad.The advantages,disadvantages,and applicable conditions of relevant technologies are summarized,and the key scientific and technical issues of rigid pile reinforcement for soft soil foundation highway embankment are pointed out.(2)Introducing the engineering overview,hydrogeology,and engineering geological background of a highway in Guangdong Province.The working principle and construction process of using bagged sand wells and prestressed pipe piles to strengthen soft soil foundation are briefly described.Typical test sections are selected where the engineering geological conditions,soft soil thickness,and embankment fill height are similar.Geotechnical monitoring sensors,including settlement meters,pore water stress meters,inclinometers,displacement meters,and earth pressure boxes,are deployed at points of interest within the subgrade cross-section for long-term observation.(3)Analysing the time history curves of soil pressure,settlement,deep lateral displacement,base lateral displacement,and pore water pressure monitored on site for a long time.A comparative study is conducted on the stability of embankment performance of two soft foundation treatments.The results showed that PHC pipe piles significantly improved embankment stability compared to bagged sand well treatment.PHC pipe piles reduced limited settlement by about 50% and limited lateral displacement by about 65%.The pile cap enhances the downward transfer of embankment load and promotes the pile soil system to jointly bear the overlying load.(4)Establishing a two-dimensional model of a highway embankment on a soft soil foundation based on finite element calculation.The distribution laws of foundation settlement,lateral deformation,and effective principal stress under three working conditions,including no treatment measures,treatment with bagged sand wells,and reinforcement with PHC pipe piles,are further discussed.The mechanical mechanism of filling embankment on soft soil foundation with bagged sand wells and reinforcement with PHC pipe piles is revealed.Finally,the proposed methods and means for the treatment of soft soil subgrade in engineering practice are presented.