Study On The Pile-soil Stree Ratio Of Pile-net Composite Foundation Under The Embankments

Pile-soil stress ratio is an important parameters of the embankment load transfer mechanism and the working state of the pile-net composite foundation, it is also an important indicator of the interaction between pile and soil to support embankment load, and it is an important content in the modern optimization design of the composite foundation. At present, the domestic and foreign scholars’researches of the pile-soil stress ratio are mainly from three aspects:theoretical calculation, tests at the site and numerical simulation. There are many theoretical calculation methods, but large difference exists because of the different assumptions. A unified theory has not been formed until now. So theoretical calculation lags behind the tests at the site and numerical simulation. In order to research the settlement, lateral deformation and other properties of the composite foundation, pile-soil stress ratio should be studied first. The importance of the pile-soil stress ratio in the design is more and more prominent, and the accuracy requirements of the pile-soil stress ratio is becoming more and more rigorous. So in order to study pile-soil stress ratio, tests at the Liu-nan passenger dedicated line to do the following tasks:1. Introduce the topic background of this article, the concept, theoretical calculation, tests at the site and numerical calculation of pile-net composite structure from the domestic and foreign in recent years.2. Expound the structure of pile-net composite foundation, and discuss the reinforcement mechanism of CFG pile, geogrid-reinforced, geogrid and the interaction amony the pile, net and soil of the pile-net composite foundation.3. Because of the pile arrangement at the site of Liu-nan passenger dedicated line, the author use the Two-dimensional model to research the soil arch. A theory analysis method of the pile-soil stress ratio was developed by taking the consideration of soil reaction among the piles. And the coefficient of ground reaction was discussed, which effects on sedimentation differences and the pile-soil stress ratio.4. Detailed analysis was done on the tests at the site and tests in the laboratory to select the parameters. And experiments were done to study the height of embankment effect on the settlement of the pile-net composite foundation, sedimentation differences and pile-soil stress. According to the results of the tests at the site, discuss the effect of pile spacing, pile length, pile caps and other factors on the pile-soil stress ratio.5. Plaxis numerical simulation was analyzed for the settlement and pile-soil stress ratio according to the site conditions. And different soil compression modulus, pile diameter, pile spacing, pile length, roadbed filler stiffness, geogrid tensile stiffness, cushion thickness and other factors on the pile-soil stress ratio were analyzed and the results obtained:the greater the compression modulus of soil, the larger the pile-soil stress ratio; the smaller the ratio of spacing between piles and pile spacing, the larger the pile-soil stress ratio; The longer pile length, the larger the pile-soil stress ratio; greater the roadbed filler stiffness, the larger pile-soil stress ratio; greater the geogrid tensile stiffness, the larger pile-soil stress ratio; the greater the cushion thickness, the larger the pile-soil stress ratio.