| In the field of fill site engineering,the pile-raft foundation has good advantages in controlling the differential settlement of the foundation,improving the bearing capacity and building safety.At present,it can be seen from the construction land of the Kangjiagou filling site that the buildings are mainly built on the excavation site,and the land utilization rate is not high.This article uses the Kangjiagou filling site as the engineering background.On the basis of the experiment,the working characteristics of the pile-raft foundation in the fill site were studied.Using the ABAQUS finite element numerical simulation method,the influence of factors such as the slope of the fill site bonding surface,the pile spacing of the pile-raft foundation,and the length of the piles across the fill site on the working behavior of the pileraft foundation were studied separately.The comparative analysis between groups has obtained the force and deformation law of the pile-raft foundation and the foundation soil of the fill site,and provided the prevention and control measures for the differential settlement of the foundation,the basic differential settlement preventive measures are given to provide theoretical basis for the construction of practical projects,and the main research results are as follows:(1)In order to improve the construction land utilization rate of the filling site,without changing the pile-raft foundation structure,the pile-raft foundation can be crossed to the filling area,and the length of the raft in the filling area occupies the entire raft.1/8 of the length meets the building foundation design code.Due to the low degree of land consolidation in the fill area,under the action of the pile-raft foundation and external loads,the subsidence of the foundation soil has the regular characteristics of "large middle,small outside,large top and small bottom".(2)Research on the effect of the slope of the combined surface on the stability and deformation of the foundation.From the point of view of the allowable differential settlement difference of the building,it is not satisfied that the differential settlement logarithm of adjacent piles has a relationship of "30°>45°>60°".The settlement difference is mainly concentrated between the edge pile and the inner pile.For this reason,priority is given to the60° bonding surface slope in the construction,and it is more conducive to the stability of the foundation to use this slope in the 1/8 raft length.(3)Changing the pile-raft foundation structure under the condition of 1/4 raft length.In terms of the deformation law of the fill site,the differential settlement of adjacent piles with 4times the pile diameter pile spacing meets the allowable value of the building foundation design code.Combining the two working conditions of long and short piles,the number of pairs of piles whose lengths of two groups of piles do not satisfy the differential settlement of adjacent piles decreases with the increase of pile length.From the position point of view,they are concentrated between the outermost side piles and the adjacent internally measured piles(4)1/8 raft length 6 times the pile diameter and the pile spacing meets the building foundation design code.In order to improve the safety and stability of the building,a combination of long and short piles can be considered in this working condition.The 1/4 raft length is 4 times the pile diameter and the pile spacing meets the building foundation design code,which improves the construction land utilization rate in the fill area.After comparison with other working conditions,under the same conditions,the increase in the slope of the bonding surface can effectively improve the stability and safety of the building foundation.In addition,considering the design of the pile-raft foundation and the slope of the joint surface,control measures to reduce the differential settlement of the foundation across the fill site are proposed. |
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