Research On Bearing Capacity Of Pile Foundation In Songhua River Floodplain In Harbin

In recent years,pile foundations in civil engineering construction have been increasingly used in the basic design of various types of buildings.The working performance of the pile foundation is mainly determined by the engineering geological conditions of the construction site.The construction site of the Songhua River floodplain in Harbin is generally composed of cohesive soil,sand with low density,sandy soil and clay,and has the characteristics of large water content and close to saturation.Due to the disturbance of the pile foundation construction,the pore water pressure in the foundation is often increased,which leads to the abnormality of the bearing capacity of the pile foundation and the slack.Therefore,it is of great practical significance to study the bearing capacity characteristics of pile foundation in the floodplain area of Harbin Songhua River.This paper mainly does the following work for the pile foundation of the Songhua River floodplain area in Harbin:(1)Study on physical and mechanical properties of foundation soil in Songhua River floodplain area of Harbin.Firstly,statistical analysis of various aspects of engineering geological survey data in this area,mainly based on the Harbin Songbei Wanda City Project,Shangri-La Hotel Project,Harbin Grand Theatre,R&F Jiangwan New City and other landmark buildings along the Songhua River,and then The site engineering geological characteristics of the site are studied.It is concluded that the main soil layer of the Songhua River floodplain area in Harbin is sandy soil and cohesive soil.Among them,the sandy soil layer has the characteristics of wide distribution,no cohesion,large internal friction angle and low natural strength;while the clay soil exists in the interlayer,which has low natural strength,small cohesive force and small internal friction angle.Features can not be regarded as the holding layer of engineering.The calculation method of soil shear strength at the interface between pile and soil is deduced.The strength index of soil in main soil layers of Harbin Wanda City,a typical project of Songhua River floodplain in Harbin,is given;(2)The influencing factors of pile-soil interaction are analyzed,including the influence of soil physical and mechanical properties,the section stiffness of the pile and the influence of pile-forming process,as well as the time effect of clay soil and the stress relaxation effect of sandy soil.The load transfer behavior and transfer model of the pile are studied,and the empirical model of load transfer is proposed to be compatible with the sandy soil of the Songhua River floodplain in Harbin;namely: the lateral soil load transfer model of the double-fold line pile and the soil load transfer model of the three-fold line pile end;(3)Research on vertical compression and static load test of prototype in-situ single pile.Taking Harbin Wanda City Pile Foundation Inspection Engineering as the research object,three different types of pile foundations were selected,and the load and settlement variation curves of the test piles were obtained by static load test.The data of steel stress gauge and earth pressure box were obtained.On the basis of the parameters,the parameters of the empirical model of pile-side and pile-end load transfer are determined;(4)Time-dependent analysis of bearing capacity of pipe piles.Based on the Qianshan static pressure pipe pile test project,the time-dependent bearing capacity of the pile foundation was studied.The pipe pile with a diameter of 400 mm showed a slight decrease with the ultimate bearing capacity.The ultimate bearing capacity of a pipe pile with a diameter of 500 mm is first reduced and then increased,but it has not recovered to the level at the time of pile formation;(5)Numerical simulation analysis research.Using FLAC3 D software for numerical simulation analysis,three different test piles of Harbin Wanda City project site were simulated and analyzed.Compared with the measured values,the calculated values of pile foundation bearing capacity are close to the measured values,and the pile side frictional resistance is compared.It has a similar trend with the measured values,and tests the load transfer model of the pile and the applicability of its parameters.The actual situation shows that these research results are more optimistic,which shows that the floodplain area of Harbin Songhua River can learn from the research ideas of this paper to promote various construction activities.