Study On Settlement Performance Of Pile Foundations With Different Piles Under Vertical Loads

In recent decades,Chinese economy,culture,science and technology,education and other fields have developed rapidly,and more and more high-rise buildings have emerged in China.The pile foundation has become the basic form of high-rise buildings in China due to its high bearing capacity and convenient construction.In the design of conventional pile foundation,the form of uniform piles is often used.However,due to the superstructure load or the uneven distribution of the stratum,the degree of stress superposition of pile end is different,which makes the differential settlement larger.In severe cases,the upper structure is damaged and affected.Normal use;secondly,the actual pile soil will bear part of the load,and the load will be fully borne by the pile during design,resulting in waste of pile bearing capacity.By adjusting the pile spacing,pile length and pile diameter to adjust the pile foundation stiffness to reduce uneven settlement,and considering the pile-soil load sharing,the pile foundation design method needs further research and improvement.Based on the engineering example,this paper analyzes the actual engineering by using the method of stress and settlement decomposition to calculate the settlement of the building,and introduces the concept of area ratio and pile-to-space ratio to analyze the settlement law of pile foundation,and proposes a new basis based on the concept of variable stiffness leveling.The basic pile scheme further studies the influence of pile spacing and pile number on settlement,and then proposes a variable pile spacing design method that effectively reduces uneven settlement.The main contents and research results have the following aspects:(1)Combined with the actual project single pile test results,the ABAQUS software was used to establish a single pile finite element analysis method.On this basis,the load sharing of piles and soils with different piles of different piles is analyzed,and the relationship between pile-soil load sharing ratio and bearing area and pile cross-sectional area ratio is proposed.(2)In this paper,considering the load sharing of piles and soils,the method of calculating the settlement of soil between piles and piles is proposed.The settlement of pile foundation is divided into two parts:settlement caused by pile-sharing loadS_p and settlement between piles and soilS_r.According to pile-soil load sharing the calculation formula of pile-soil area ratio is used to obtain the corresponding pile and soil load sharing conditions,and the total settlement of pile foundation is obtained by superposition.(3)Because the superposition of pile end stress in the central part is higher than that of the foundation,the settlement shows a small"disc"shape distribution inside the outer large part,which has a large differential settlement.According to the design principle of“strengthening the center and weakening the periphery”and changing the pile foundation,the central area occupying 23%~31%of the area of the slab is taken as the core area,or the area where the core tube is located is the core area,and the rest is non-core.Area.The calculation shows that the method of adjusting the pile spacing between the core area and the non-core area of the pile foundation can effectively reduce the differential settlement of the pile foundation.(4)Combining with the actual engineering for calculation and analysis,it is proposed to use large pile spacing in the core area while maintaining the total number of piles,and using small pile spacing in the non-core area to carry out piles,which has a significant effect on reducing uneven settlement.For the actual engineering calculation,the recommended pile spacing ratio should be 1.67~1.83.(5)The pile foundation considers the design method of soil-supporting load between piles,and makes full use of the soil-carrying capacity between piles.The method of reducing the number of piles can be adopted,which has achieved the purpose of reducing engineering cost.According to the actual engineering calculation,when the number of piles is properly reduced,the pile foundation satisfies both the bearing capacity and the deformation requirements,and has good economic benefits.