The Research On The Bearing Mechanism Of Cement And Fly Ash Gravel Pile Composite Foundation And Its Application In Zhu Madian Developing Area

Cement and Fly Ash Gravel (CFG) Pile is composed of gravel, stone chips, sand, fly ashand water, which are compounded to make, by certain pile-forming machine, piles withdifferent strength grades. These piles cooperate with soil among piles and cushion to form theCFG pile composite foundation. It has high bearing capability, because the landscapeorientation of CFG piles is not significant in the vertical loads so that the whole pile can exertthe friction of the pile side to make the loads on it spread to the deep foundation through theshin friction around the pile and the resistance of the pile tip.Zhu Madian Developing Area is located in the south-central Henan, and belongs to thelandscape of Piedmont alluvial phase. It mainly is the deposit of Pleistocene and theQuaternary under the ground50m in the range. Because the eigenvalue of the compositefoundation bearing capability and the modulus of compressibility are comparatively small,they can not meet the demands of high-rise building for high bearing capability and smalldeformation of the foundation. CFG pile composite foundation is commonly used in high-risebuilding in this area.Based on the study of the relevant theories, this article analyzes the bearing mechanismof the interaction among piles, the soil between piles and cushion,and expounds how to setcushion, how to calculate the pile-soil stress ratio, how to make the value of β, coefficient ofthe soil between piles bearing capability.It especially considers the effect of side loading onthe equation for calculation of the CFG composite foundation bearing capability. Aiming atthe engineering projects in Zhu Madian developing area, the equation for the bearing capacityof composite foundation is corrected on the base of the equation in Technical Code forGround Treatment of Building and proven through the engineering projects. Then, this article,through the engineering project in Zhu Madian developing area, also analyzes theapplicability, design and construction methods, construction process control, qualityinspection and its processing effects. The results has a certain reference value for the similarprojects in Zhu Madian developing area.Its main conclusions are as follow:(1)The reason thickness of cushion is got through analyzing its mechanism, and thereasonable thickness of cushion is suggested based on soil conditions in Zhu MadianDeveloping Area.(2) The stress ratio theoretical solution is gained through the deformation calculationmodel of the composite foundation with a pile; the initial value of the sunk plane is proposedto be65%of the pile length and this value is used to calculated the stress ratio.(3) It is found that, compared with non-side loads, the bearing capability of the composite foundation is improved under the side loads, so it is suggested that a side effectcoefficient Κ should be applied to the equation for estimating the bearing capability of CFGpile composite foundation in Zhu Madian developing area, and it has been proven throughengineering projects that the revised equation can be applied in Zhu Madian developing area.