| Pile foundation has gradually become a commonly used foundation form for high-rise,super high-rise buildings,high-speed railways,and highway bridges due to its advantages such as high bearing capacity,small settlement,slow settlement rate,and ease of mechanized construction.For a long time,many researchers have focused their studies on the performance of pile foundations under vertical loads and have achieved a series of fruitful research results.However,compared with the vertical bearing characteristics of pile foundations,the horizontal bearing characteristics of pile foundations are relatively complex.There is relatively little research on the performance of pile foundations under lateral loads both domestically and internationally.Currently,most research on pile foundations focuses on those with circular cross-sections.For friction piles with the same pile material,cross-sectional area,and length,the specific surface area,maximum moment of inertia,and flexural stiffness of circular piles are the smallest compared to other constructable cross-sectional shapes,resulting in the worst vertical and horizontal bearing performance.Compared with other deep foundation forms,rectangular piles have advantages such as large lateral friction resistance,high stiffness,and diverse combinations of cross-sectional shapes.They are particularly resistant to large horizontal loads and bending deformations.Additionally,they can be freely configured with long-side directions to address directional loads,making them a promising application prospect.As a non-circular pile with a relatively regular shape,the rectangular pile can withstand large vertical loads and resist significant horizontal loads and bending deformations.In recent years,there has been significant development in the construction techniques and equipment for rectangular piles,leading to their increased application in recent engineering practices.However,internationally,especially domestically,there is limited research on the stress mechanisms,bearing characteristics,failure processes,and design calculation models of rectangular pile foundations under lateral loads.Existing research has focused primarily on vertical bearing characteristics and theoretical analysis and numerical simulations.There are still research gaps and unresolved issues regarding the horizontal bearing characteristics and model testing of rectangular piles.Therefore,it is necessary to conduct research on the horizontal bearing characteristics of rectangular pile foundations under horizontal loads.The main research content of this thesis includes the following four aspects:(1)Experimental study on the horizontal bearing characteristics of rectangular piles: Design a specialized model test device to study the pile-soil interaction of rectangular piles under horizontal loading conditions.Prepare sandy soil foundations to investigate the influencing factors of the horizontal bearing capacity of rectangular piles,such as cross-section width,pile length,cross-section aspect ratio,mud cake properties,and the impact of post-grouting.Parallel tests using model boxes are conducted to compare the horizontal bearing characteristics of rectangular pile foundations and traditional circular piles in terms of internal force distribution,frictional resistance distribution around the pile,soil pressure distribution around the pile,and deformation of the soil around the pile.(2)Numerical analysis and study of influencing factors on the horizontal bearing capacity of rectangular piles: Investigate the differences in horizontal bearing characteristics,such as internal force distribution,frictional resistance distribution,and soil pressure distribution around the pile,considering rectangular piles with different pile lengths and aspect ratios.Focus on studying the horizontal bearing characteristics of rectangular piles with different aspect ratios(1:2~1:5).Propose reasonable geometric dimensions for the design of rectangular piles and,for more sensitive influencing factors,propose key technical measures in design and construction to ensure the service performance of rectangular piles.(3)Theoretical analysis and research on the horizontal bearing capacity of rectangular piles: Through experimental studies on the horizontal bearing characteristics of rectangular piles,combined with numerical analysis results,systematically study the differences in horizontal bearing characteristics of rectangular piles with different pile lengths and aspect ratios in terms of the mechanical properties of the pile-soil interface.Establish a theoretical model for analyzing the horizontal bearing capacity of rectangular piles,reveal the mechanism of differences in horizontal bearing characteristics between rectangular piles and circular piles,and propose design and calculation theories for the horizontal bearing capacity and deformation of rectangular piles.Provide a calculation method for the equivalent width in determining the horizontal bearing capacity of rectangular pile foundations.For rectangular piles without fixed bottoms,propose a theoretical solution for the effective pile length through fitting methods and put forward a calculation method for the effective pile length of rectangular pile foundations.Based on the calculation formula for the p-y curve of circular piles,introduce correction coefficients B and C,propose a calculation method for the p-y curve of rectangular piles,and verify the reliability of the formula through numerical simulations and theoretical calculations.(4)Conduct full-scale tests on the horizontal bearing characteristics of combined rectangular piles with a "mouth" shape in combination with actual engineering projects.Obtain actual bearing capacity data of horizontally loaded rectangular piles,analyze the characteristics of their horizontal bearing behavior,and study the general horizontal bearing characteristics of combined cross-section rectangular pile foundations.Finally,the content of the entire study is summarized,and a brief discussion is conducted on the direction of further research work. |
