Research On Settlement Calculation Empirical Coefficient Of High-Speed Railway Embankment Of Thick Soft Soil CFG Pile Composite Foundation

In recent years, the CFG pile composite foundation has been widely used in high-speed railway foundation treatment. But the settlement calculation of theoretical research still lags behind in engineering practice, including the settlement calculation empirical coefficient due to a lack of measured data is still value in accordance with the empirical coefficient of composite foundation under the building foundation. The recent research shows that the characteristic of composite foundation under embankment differ from which under the building foundation. The former one is under flexible foundation, while the latter one is under rigid foundation. There is an urgent need to extensive accumulation of the field measurement data, suitable for high-speed railway embankment load CFG pile composite foundation settlement calculation empirical coefficient. To solve this problem, the following work is done:(1) Collection of the Beijing-Tianjin inter-city, the Beijing-Shanghai high-speed railway of7CFG pile cross-section of the site foundation settlement measured data, the geological survey data and design parameters, and data processing.(2) Based on the layerwise summation method, composite modulus is used to calculate the total settlement of the composite foundation. In the total settlement of composite foundation calculation, the compression layer thickness can be defined by the stress ratio method or deformation ratio control method.In the calculation of the composite modulus, corresponding to the two methods above-mentioned,the natural soil compression modulus has two definition,one is modulus under100kPa to200kPa pressure segment i.e. standard modulus, and the other one is that under actual pressure section.(3)The the total settlements calculated by the single modulus method and e-p curve method are amended by using the current specification empirical coefficient.Compare them with the forecast total settlement, it is found that the e-p curve method of calculation results are closer to the predicted final settlement. That means the e-p curve method is more suitable for deep soft soil settlement calculation.(4) the equivalent compression modulus of compression layer in the E-p curve method and the results of settlement empirical coefficient are analyzed. And the values of the empirical coefficient of CFG pile composite foundation settlement calculation in the condition of different equivalent compression modulus under the railway embankment loads are proposed. They are greater than the recommended values of the construction foundation. The paper shows that it is unsafe to use the empirical coefficient of settlement calculation that the building foundation recommended applied to the settlement calculation of CFG pile composite foundation of soft soil deep layer of high-speed railway.