| With the implementation of the national “Belt and Road” strategy,the economic development of the loess region in the central and western China has entered a new stage.However,the land issue has become an important factor restricting the further development of the local economy.In recent years,to obtain more urban land,there have been more and more high-filling Projects in the loess area.Regarding the construction of high-filled sites,the core of the Problem is differential settlement or even deformation caused by uneven foundation stress after work.In this Paper,the author would implement the research to study the stress and deformation characteristics of Pile foundation in excavation and filling area in high fill site.This research result relied on the Shaanxi Provincial Science and Technology Coordination Project(2012kTZD03/07)and the Shaanxi Natural Science Basic Research Project(2017JM4015),with the kangjiagou high filling Project as the background,and the observing from the field Pile foundation test,indoor Physical model test and ABAQUS numerical simulation.The main research contents and research results are as follows:(1)According to the load test of the pile foundation in the high-filled site,combined with the engineering example,the indoor physical model test with the similarity ratio of 1:5was carried out,and the variation characteristics of the axial force and side friction of the pile foundation were analyzed..Through the analysis of the test results,it is found that:(1)In the high-filling site,the axial force and side friction resistance of each section of the pile body increase with the increase of the depth of the fill,and the bearing capacity of the bored pile is also worse;(2)The lateral frictional resistance zone appears in the vicinity of the excavation and filling junction in the excavation and filling combination zone.(3)The lateral frictional resistance of the pile foundation on the upper and lower sides of the transition zone is greatly changed.(2)On the basis of field test and laboratory test,the physical model was established by using ABAQUS finite element software,and the distribution characteristics of axial force and side friction resistance of pile foundation under different soil depth conditions were analyzed.The results show that:(1)the position of the“transition zone”of the side frictional resistance is exactly at the interface of the excavation and filling.On the upper and lower sides of the“transition zone”,the lateral frictional resistance of the pile foundation changes greatly;(2)When the thickness of the fill is greater than 1/2 of the length of the pile,the cast pile shows the nature of the end-bearing friction pile;(3)the axial force and side friction resistance of the cast-in-place pile increase with the increase of the fill thickness.(4)At the same position of the pile body,when the soil around the pile is undisturbed,the side friction resistance value is much smaller than the side friction resistance value when the soil around the pile is filled.(3)Based on the field test,indoor test and simulation test,the design process of the pile foundation in the loess high fill site is selected and integrated.In the survey stage,measures such as increasing the number of surveys and changing the shape of the drilled holes were proposed;new construction techniques were used in the construction phase of the fill;and measures such as length and pile diameter were changed reasonably and flexibly in the design stage to further meet the excavation.Fill in the requirements of the pile foundation design of the combined area. |
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