Analysis Of Bearing Capacity Of Steel Trestle Based On Shallow Overburden Of Inclined Section

With the rapid development of bridge technology and infrastructure construction,the number of large-scale water bridge projects is increasing.In the construction of deep-water foundation,steel trestle is generally built as the transportation channel,and the operation platform is built on the steel trestle to realize the conversion from underwater operation to onshore operation.Steel trestle is generally constructed with steel pipe pile foundation and Bailey beam as the main bearing beam.Because of its advantages of fast construction speed,convenient installation and removal,and reusable,it is widely used in infrastructure projects such as bridges,ports and dams.When the bridge foundation is affected by the adverse geological environment conditions such as water flow,wave and shallow overburden,the stability and bearing capacity of the bridge foundation are faced with certain challenges.Based on the research background of the temporary steel trestle project of Qingxi bridge in Guangdong Province,this paper reinforced the condition that the steel pipe pile with inclined section and shallow overburden layer can not meet the rock socketed depth.Through the indoor model test and numerical simulation analysis,the mechanical properties and bearing capacity of the steel-concrete composite pile were studied.The quasi-static load test of the steel trestle with inclined section and shallow overburden layer was carried out,and the steel-concrete composite was carried out The bearing capacity of single pile and main components of steel trestle are studied,and the bearing capacity calculation formula of steel-concrete composite pile is established according to the above research.The specific work is as follows:(1)The scale model orthogonal test of steel-concrete composite pile is designed.The vertical bearing mechanism,failure process and failure mode characteristics of steel-concrete composite pile under vertical load are studied.The influence degree of I-steel type,internal concrete pouring height and embedded I-steel embedded depth on the bearing capacity of steelconcrete composite pile is studied.The ultimate load is determined by analysis The regression equation of peak load of steel-concrete composite pile is established,and the relationship between peak load of steel-concrete composite pile and each factor is obtained,which provides reference for practical engineering.(2)The single pile of steel-concrete composite pile and steel trestle with inclined section and shallow overburden are simulated to realize the analysis from component to structure.The changes of displacement,stress and bending moment of single steel-concrete composite pile in the process of loading are obtained.The accuracy of bearing mechanism of indoor model test is verified.The stress concentration phenomenon of embedded I-steel appears at the junction of steel-concrete section and embedded section.The vertical displacement of the steel trestle with inclined section and shallow overburden is about 2 times of the horizontal displacement,and the main components are in the elastic range.(3)The steel trestle is tested by quasi-static load test method.The main components are in the elastic range.The steel-concrete composite pile plays the expected embedded strengthening role in the design,which verifies the reliability of the reinforcement method of the steel trestle.(4)According to the bearing mechanism of steel-concrete composite pile under axial compression,two calculating formulas of the bearing capacity of steel-concrete composite pile under axial compression are established by using the unified theory of double shear and the superposition principle,and the results of the two formulas are compared with the test results.The results show that the formula based on the superposition principle is too conservative,while the formula based on the unified theory of double shear is more accurate and reliable,the error is smaller,and the calculation formula is more simple and practical.