Study On Settlement Calculation Method Of Composite Foundation Of Expressway Concrete Pile

The application of concrete pile composite foundation in highway subgrade is more and more extensive.At present,the settlement calculation of composite foundation of concrete pile in traffic industry standard at present still use the settlement calculation method of concrete pile composite foundation in architectural Engineering,In this method,the calculation of settlement is less than the actual settlement,which Resulting in a large number of highway settlement is too large,the bridge section of the transition is not ideal,mushroom Road, roadbed collapse and other defects.Deformation of pile and soil is not harmonious of concrete pile composite foundation soil deformation in subgrade Engineering.The area of soil between piles in composite foundation is often accounted for more than 90% of the total area of composite foundation,and the settlement of soil between piles is larger than pile top settlement,when the amount of concrete pile compression can be ignored without time,by the compression deformation of soil between piles to represent the amount of reinforcement area settlement.The amount of compression of soil between piles of the above the equal settlement plane is equal to the Pile top to stab deformation of embankment,The amount of compression of soil between piles of the below the equal settlement plane is equal to The pile bottom layer downward stab deformation.According to the characteristics of the composite foundation of expressway subgrade,a simple method for settlement calculation of composite foundation of highway concrete piles is proposed.Because the maximum settlement is in the middle of the roadbed,it only need to calculate the settlement of the roadbed center line.The pile soil load can be calculated by the theory of soil arch effect.When laying earthwork synthetic material,according to principle that the deflection of geosynthetics is equal to the compression of the soil between the pile and the soil,That to determination of soil load between piles under geotechnical grid.When the bottom of the pile does puncture,according to the single pile vertical force balance condition to determine the location of the neutral plane;the pile bottom does not occur when piercing damage,The neutral plane approximation is assumed to be equal to zero in the additional stress of the pile.Highway subgrade width is usually larger than the depth of soft soil layer,approximate according the principle that the total load of the pile and soil in the reinforcement area is constant along the depth,to determin the additional stress of soil between pile,Then to calculate the compression of soil between piles by delamination summation method.Finally,this settlement calculation method's feasibility and practicability are verified by two engineering cases.