Calculation For Displacement And Internal Force Of Pile Anchor Retaining Structure Based On Improved Increment Method

As an important support system gradually developed in the 1980 s and applied to engineering,the formation of pile anchor retaining structure for deep excavation combines the principle of anti-slide pile support with anchor support.With decades of application and development,the size and depth of foundation pit engineering have increased.At present,in the study of the internal force and deformation of the pile anchor retaining structure,the improved incremental method considering the influence of the construction process is widely used.In the incremental method theory,the precise calculation of load increment plays a key role in applying this method into practice.It is also a key point to consider whether the reaction force released by the soil resistance change caused by the change of the horizontal resistance coefficient of the soil below the excavated surface should be taken into account.At the same time,the analysis of the factors affecting the elastic resistance of the soil is also a priority.The importance of this paper is to introduce a combination of theoretical calculations and numerical simulations,and on the basis of previous theoretical researches,the main works is as follows:(1)On the basis of the existing theoretical research of incremental method,in order to study the internal force and deformation of the pile anchor structure,the Winkler foundation model is introduced to replace the interaction between the supporting pile and the soil and the anchor effect with spring equivalents.Firsty,it is important to ascertain the type of earth pressure acting on the supporting piles—displacement earth pressure.By analyzing the shortage of the existing incremental method in calculating the incremental load,it is shown that the incremental load should also include the reaction force released by the elastic resistance change of the soil below the excavated surface due to the change of resistance coefficient and the prestress and prestress loss.Finally,an improved incremental method model for calculating displacement and internal force of pile anchor retaining structure for deep excavation is established.(2)By constructing a balanced nonlinear equation and an iterative solution theory based on the incremental method,an incremental calculation method that is more in line with engineering practice is proposed.Combined with a deep excavation project,the MATLAB program is compiled according to the corresponding parameters in the engineering example,and the finite element soft PLAXIS is used to simulate and verify the engineering example.Finally,the two results are compared and the results show that the method for calculating the displacement and internal force of the pile anchor retaining structure is reasonable and feasible.(3)The elastic resistance of the soil directly affects the internal force and deformation state of the supporting structure.Most previous studies have focused on the resistance coefficient or proportionality coefficient of the soil coefficient.There are few analyses of the factors affecting the elastic resistance of the soil.By introducing the method of control variables and the numerical simulation,this paper simulates the main factors affecting the soil's elastic resistance—the cohesion and the friction angle of the soil,and uses the drawing software Origin to perform a nonlinear fit on the results.The results show that with the decrease of the cohesion of the soil or the friction angle of the soil,the displacements of the pile gradually increase,but the maximum displacement is always within the allowable range of deep excavation deformation.