Study On Reinforcement Mechanism Of CFG Pile Compositefoundation In Non-self-weight Collapsible Loess Area

CFG pile composite foundation is one of the more popular research direction in geotechnical engineering,as the natural foundation bearing capacity and deformation have been unable to meet the building height increases greatly the basal pressure,at the same time the use of pile foundation in a certain,bearing capacity of soil while meet the requirements of the bearing and deformation,but the actual engineering,economic and environmental performance can not satisfied the condition of the background,have the characteristics of rigid pile,pile material at the same time with high caking property of CFG pile composite foundation is born.The core bearing technology is to make the soil between piles participate in the strengthening of the superstructure through the rational setting of the mattress.At the same time,with the development of construction technology,the use of long auger pipe pumping into pile has many advantages,such as low construction difficulty,small soil disturbance and good economic performance.Through the direct participation of soil between piles,the full length of the pile exerts lateral friction resistance,thus reducing the settlement deformation,and the soil shares part of the load so as to improve the bearing capacity.Therefore,CFG pile composite foundation has been widely used in foundation treatment in recent years.A form of composite foundation reinforcement effect in a soil layer with the regional representative has the significance of research,namely on the combination of collapsible loess foundation of CFG pile composite foundation reinforcement mechanism research,first of all,through in-depth theoretical study,on the basis of study on the properties in the understanding of its mechanism,bearing capacity and settlement control research,put forward the pile bearing capacity of soil between correction calculation,analysis and comparison of the calculation formula of vertical bearing capacity of the single pile bearing capacity of composite foundation and pile spacing calculation method.In the next step,combining with the practical project of the second phase commercial high-rise project of zuitou village,fuping county,shaanxi province,the theoretical basis detailed in the first three chapters is reasonably applied to the actual project,so as to make up for the current situation that the theoretical research lags behind the practical research.The foundation form is selected in the calculation and design study of CFG pile composite foundation,and the natural foundation,CFG pile composite foundation and bored pile foundation are compared.The conclusion that CFG pile is most suitable for the non-self-weight collapsible loess of this project site is drawn.Based on the above analysis results,the calculation results of bearing capacity of single pile,characteristic value of bearing capacity of composite foundation and base pressure are compared,the calculation value of settlement is compared with measured value,and the distance between piles is determined.After the calculation,the influences of pile materials on the composite foundation,the influences of different pile-forming technologies on its bearing capacity,the inspection technology of CFG pile composite foundation after construction,pile layout design and other relevant matters needing attention are analyzed and compared.In the end,it is found that CFG pile composite foundation can meet the requirements of settlement and bearing capacity in buildings with high basement reaction force.In addition,compared with pile foundation,CFG pile composite foundation has many advantages,such as cost saving and environmental protection.At the same time,the measured value of single pile static load experiment is compared with the ANSYS finite element model established by using DP criterion,and the similarities and differences between measured value and simulated value in the loading process are analyzed,and the rationality and related problems of the model are analyzed.After the conclusion is reached by means of calculation,this paper,combined with ANSYS finite element program,makes a detailed analysis of the important variables that affect the strengthening mechanism of CFG pile composite foundation,so as to improve the calculation content,and through the comparative analysis of the pile-soil stress ratio and the influence trend of pile and soil settlement.Finally,the simplified single pile model was established to analyze the variation rules and stress characteristics of the bed cushion thickness,pile length,pile body stiffness,soil modulus and pile-soil stress ratio,single pile bearing capacity and settlement in the range of about 2 times of base reaction force under the condition of term by term loading.Finally in this paper,the BP neural network model by changing various influence factors,composite foundation bearing capacity of soil between piles and collapsible loess of the relationship of initial collapse pressure,get the mattress under the change of various influence factors such as the thickness,the loess of initial collapse pressure is less than the value range of the bearing capacity of soil between piles composite foundation further and CFG pile composite foundation and collapsible loess combined the two important research object,to form the organic whole.The optimized data range can be used for reference by engineers and technicians in the future.Finally,this paper summarizes the conclusions and existing problems of the above research,so that the theoretical research can meet the needs of engineering practice as far as possible.Some parameter ranges and results are put forward for reference in engineering practice.Finally,it is hoped that the development of CFG pile composite foundation can be applied more widely in the future.The analysis of pile and soil action is more profound,and the development potential is prospected.