Study On Reasonable Dip Angle Of Inclined Support Piles In Silt Of Eastern Zhengzhou

Zhengzhou,provincial capital of Henan,is the core status of the Central Plains Economic Zone which it makes the development of Zhengzhou to a higher level by the national strategy of the rising of Central Plains and the application of the national central city brings great vitality for the development of Zhengzhou.The implementation of a series of policies make the urbanization process of Zhengzhou to step in the road of rapid development.The urban population density are increased in Zhengzhou and the construction industry develop rapidly with it.These factors bring great challenges to the foundation pit engineering,eg:intensive building,deep and big foundation pit and complex construction environment.The rowed piles is the one of the supporting and protection construction that is widely used in the foundation pit engineering,but a large number of engineering cases indicate that the traditional vertical supporting and protection pile has large bending deformation to the strain and bending moment of the supporting and protection piles becoming too large and the active earth pressure of upper pile body has the tendency of obvious increase with the deep increasing of foundation pit.Therefore,it has two situations in the application of traditional vertical piles.One is that pile design is more conservative to the internal force of pile larger than its design value and not to fully play to the supporting performance of retaining piles to cause waste.Other is that the engineering accidents are caused by the excessive earth pressure in engineering.The occur of these problems doesn't accord with the development of social economy and the direction of the development of soil mechanics.Focusing on these issues,some researcher and scholar propose that the foundation pit supporting piles incline to the angle of outside of the foundation pit to improve the force performance of piles.The researcher finds the less relevant research on the supporting and protection piles inclining and not get any reference about technical specifications during the collecting and reading the literature.The previous research has different practices on the conditions used in the research of the inclined supporting piles,one is artificial coarse sand in the laboratory and other is clay and silty clay,but the research on silt layer has not been carried out.Therefore,the paper studies the theoretical calculation,practices the indoor model and analyses the numerical simulation combined with the extensive soil in the eastern district of Zhengzhou to explore the range of the reasonable dip angle of the inclined supporting piles in the eastern district of Zhengzhou based on the summary of the previous research.My working in these two years:(1)By participating to the professional practice,going deep into the frontline of supporting and protection engineering of foundation pit,observing closely the design,make and construction of supporting and protection piles in the actually engineering and understanding the action mechanism of retaining piles;By collecting and reading the engineering geological exploration literature,geological exploration standard and the standard of supporting and protection engineering of foundation pit to understand the affect the silt on the supporting performance of retaining piles and to understand the characteristics and relevant parameters of silt in the eastern district of Zhengzhou.(2)By collecting and reading the relevant literature about inclined pile to improve the calculation formula of inclined pile and to theoretically calculate of bending moment of inclined supporting piles in silt.(3)After the master of engineering construction emphasis and the hypothesis of relevant parameter of theoretically calculate in the professional practice,based on multi factors consideration,to formulate the indoor model test program.In the process of the test,the strain of the pile is obtained by strain measuring instrument and calculated bending moment distribution of pile and the distribution of bending moment is studied carefully.(4)On the basis of the indoor model test,building the three-dimensional calculation model of inclined support pile test by finite element analysis software ABAQUS to verify the reliability of theoretical calculation and model test.The conclusion by the my above working:(1)After theoretical calculation,assuming using foundation pit support with inclined retaining piles and taking pile moment as the main consideration,the researcher thinks the reasonable inclination angle of the inclined supporting pile is 10°-15° in the silt in the eastern district of Zhengzhou.(2)By the analysis of test data collection indicates:in a certain range,foundation pit inclined retaining pile with the increase of the inclination angle,the bending moment of the pile foundation decreases gradually;the positive bending moment of the upper part of the pile body tends to be close to that of the lower half part.The bending moment distribution of inclined pile is more favorable to the performance of concrete pile and the advantages of retaining piles are becoming more and more obvious,the safety is higher in engineering construction.By the test analysis calculation shows:taking pile moment as the main consideration to study the reasonable inclination angle of the inclined supporting pile in the silt and its range is 10°-15°(to calculate the length of the interval by 5°).(3)With the increase of the supporting pile inclination angle,the peak value of the bending moment in the lower part of the pile are moving down.By the data analysis finds the speed of moving down is the most fast in the dip of 10°-15°.(4)The conclusion of reasonable inclination angle of the inclined supporting pile in the silt in the eastern district of Zhengzhou is verified its range is 10°-15° after simulation calculation.