Research On Bearing Capacity Of Super-long Piles Considering Interaction Between Resistance And Lateral Resistance

In recent years, the super-long pile of large diameter are widely used in the construction of high-rise buildings, large bridges, ports and so on,which is a new challenge to pile foundation theory of the traditional subject. A study found that when the pile top load level and closer to the ultimate bearing capacity,closing to the super-long pile side friction resistance will have the phenomenon of suddenly increasing,and under the influence of different soil strength of pile and soil contact surface properties,this expression of the increasing effect is also different. Studying the causes of this kind of enhancement effect and its mechanism in depth, there is a vital significance on the super-long pile of theoretical research and practical application.Designing implementation of the super-long piles indoor model test, this paper analyzes the model pile under different pile top load, the relationship between load and settlement, the relationship between axial stress of pile and depth, pile side friction and the relation between the depth and load to the pile endpoint soil pressure.Using the software of ADINA establishes the finite element model of corresponding to the model test, which analyzes the finite element simulation results and the test results, on the basis of the research of the pile tip resistance and the interaction mechanism of pile side resistance. Considering the interaction of pile side resistance and end resistance, Mindlin solution is put forward to enhance the value of resistance on pile side calculation, and the calculation of combining with elastic theory method with the model pile bearing capacity is conducted, and compared the model pile side friction calculation results before and after correction.Through the above research, the conclusion is the following:(1) The settlement of pile top of super-long pile is larger, when designing the ultimate bearing capacity of super-long pile, the settlement control is more reasonable; In the process of vertical load passing down the super-long pile body, most of the load transfer to the pile side soil and pile end under load is relatively small;Parts of super-long pile side friction mainly play a role in pile body and pile bottom more than 10d range, and central pile side friction is relatively small.When the pile top load increases to a certain value,the phenomenon of the bottom closing to the pile side friction will enhance;When the pile top load arrives to 1093, pile tip resistance end and pile side resistance will be enhanced.(2) Finite element simulation can reflect the actual situation of the role of piles and soil in model test of large;Horizontal stress of pile tip resistance to pile side soil has an enhancing effect, which at the range of pile end about 5d;Within the scope of 5d the pile side resistance to stress of the pile endpoint soil has an enhancing effect,which improve the limit bearing capacity of pile endpoint soil;The reinforcement of pile side resistance to pile side resistance is not obvious.Considering the interaction of pile end and pile side resistance of super-long pile bearing capacity calculation, the key lies in the accurate calculation of pile side resistance enhancement value.(3) Making use of Mindlin solution to calculate horizontal stress of the pile-lateral which is made by the pile-end resistance, and according to the sliding friction and the normal stress has the relationship of linear, the enhancement value of pile side friction resistance under the action of pile-end is gotten.(4) When the pile top load is larger, the method of elastic theory to calculate the pile side friction and the test value near the pile end have deviated.Combining wit additional side friction modification after the calculation with the pile side friction and the test value is close, and this kind of calculation method for correct calculation of super-long pile side friction has a certain theoretical meaning and engineering value.