Study On The Working Behavior Of Rammed Expanding Pile In Tunnel Slag Site

With the accelerated pace of China's economic construction,local infrastructure construction is also increasing,large engineering projects such as railway,highway,tunnel is carried out like a raging fire,these construction projects often caused some damage to the original landform,and spoil produced a lot of waste slag,slag field is formed.The waste dump is a special artificial geological body formed by artificial accumulation.It is mainly composed of engineering waste,such as loose soil and gravel.It has the characteristics of large porosity,obvious change of particle gradation and poor consolidation.So far,there is little research on the construction of the construction in the waste residue field.Therefore,on the basis of Foping County of Hanzhong City,Shanxi province tunnel slag site engineering example of trammedexpanding pile in slag field under compressive static load experimental results were analyzed and discussed,and the three-dimensional modeling by FLAC3 D software,analyzed the parameters of soil under vertical load tunnel slag sitel pile,enlarged the size effect of abandoned muck thickness on the properties of the single pile.At the same time,combined with the layout plan of pile foundation of waste dump,a 3D model of pile group is established on thebasis of single pile,and some factors that affect the working behavior of group piles are further discussed.(1)the three-dimensional model of internal friction angle of different abandoned soil is established by FLAC3 D.When the internal friction angle of the tunnel slag site from 10 degrees to 40 degrees,the change of pile settlement and ultimate load in the waste residue field is very small,so it can be considered that the influence of the friction angle on the pile body can be ignored.(2)using FLAC3 D to establish a single pile and group pile model with different thickness of tunnel slag sitel,when the thickness of the abandoned soil is changed from 5m to 11 m,the settlement of the pile in the residue field increases significantly,and the negative friction area of the pile side increases and the neutral point moves down,the larger the thickness of the abandoned soil is,the larger the thickness of the abandoned soil is.The greater the influence of the pile,the greater the thickness of the waste residue should be chosen as 5m or so.(3)the model of single pile and group pile with different enlarging head size is established by FLAC3 D.When the size of the enlarged head is less than 0.55 m,the pile top subsidence of the pile is gradually reduced and the bearing capacity of the pile body is greatly improved.However,when the size of the enlarged head is more than 0.75 m,the axial force of the pile top of the pile tip increases abruptly,but the pile body can be damaged easily,so the size of the enlarged head should have a reasonable range,that is,between the 0.55m-0.75 m.(4)In the three-dimensional model of pile group pile,when the pile spacing is less than 6d,group piles have strong restraining effect on the tunnel slag site,which makes the ultimate bearing capacity of pile group increase,and the settlement of pile top is smaller than that of single pile.When the pile spacing is greater than 6d,the binding effect of group piles on the tunnel slag site will gradually disappear,so the tunnel slag site.6d is suitable for pile spacing in engineering construction.