Study On Deformation Characteristics Of Inclined Underlayer Pile Composite Foundation

The section from Qisha to Maoling of the Binhai Highway in Guangxi is located in the east of Fangchenggang City.Some road sections in this area have uneven thickness of soft soil layer,and some soft soil layers have inclined underlying layers,which will cause uneven foundation settlement in road engineering.And other issues.Under such special circumstances,studying the development rules and characteristics of uneven foundation settlement is the key to adopting measures to control uneven settlement.In this thesis,the composite foundation of steel slag concrete piles in the road engineering from the Qisha to Maoling section of the Guangxi Coastal Highway is taken as the research object.Through the field load test and settlement deformation monitoring,the settlement characteristics of the composite foundation of the inclined pile under the embankment load are studied.And,with the help of the finite element method,the uneven settlement and deformation characteristics of the inclined sub-layer composite foundation were further studied.The main work and conclusions are as follows:1.Select a typical monitoring section in the test section,bury monitoring elements in the section,and monitor the settlement,stress and lateral displacement of the composite foundation in the monitoring section in real time.Through the field load test,the different positions in the test section were tested and studied,and the test results can meet the design requirements;the results show that the bearing capacity and deformation of the foundation at different positions in the test section are different,and show obvious changes law.2.Settlement deformation monitoring was carried out in the test section.The results show that the settlement distribution of the composite foundation in the monitoring section is not symmetrical,and the location of the maximum settlement point occurs to the left of the midpoint of the embankment bottom（the thin side of the soft soil layer）.Further research found that the maximum value of the pile-soil settlement difference in the monitoring section occurred on the right of the midpoint of the embankment bottom（the thicker side of the soft soil layer）,and the pile-soil settlement difference gradually increased with each increase in the fill height The phenomenon.3.The foundation settlement of the test section was analyzed by the finite element method.Through research,it was found that the settlement of the composite foundation in the test section mainly originated from the compression of the underlying layer;at the same time,the composite foundation settlement in the section was fitted and the composite was determined.The maximum settlement of the foundation and the location of the maximum settlement point.4.By changing the parameters of the inclination of the underlying layer,the pile modulus,the aspect ratio and the composite modulus ratio,53 composite foundation models for different working conditions were established.And introduced indicators such as the uneven settlement coefficient?,maximum settlement point deviation rateηand the maximum settlement ratio?,and analyzed the influence of various parameters on the uneven settlement and settlement characteristics of the composite foundation.The results show that the inclination of the underlying layer is one of the reasons for the maximum settlement point offset,and the offset is greatly affected by the pile modulus,and the presence of a pile modulus E_p0 can makeη=0,?=1;When the composite modulus ratio tends to 1,ηand?respectively tends to 0 and 1;ηand?decreases with increasing aspect ratio,and?increases with increasing aspect ratio.5.The optimal design of the composite foundation of the test section was carried out.By changing the three parameters of pile spacing,pile diameter and cushion thickness,the bearing capacity and settlement deformation of the composite foundation were analyzed.Finally,six feasible optimization schemes were determined.After comparative analysis,the original design scheme was concluded to be too conservative,and a more economical scheme was suggested.