Study On Calculation Of Settlement Of DDC Composite Foundation In Collapsible Loess Area

Composite foundation with piles thrusted-expanded in columnhammer (DDC) is a relatively new composite foundation, which is increasingly applied in a wide range just because their good effect on the compaction of soil among piles and their strong economic performance and applicability. However, the theoretical research on such foundation has lagged behind, and the settlement calculation lags far behind the engineering practice. The application of composite foundation DDC in collapsible loess areas, which is to eliminate the collapsibility of loess and control project settlement, is in a small number and the study on the settlement part is almost empty.Taking the DDC in the entity test in collapsible loess areas along Zhengzhou-Xi'an Passenger Line Mileage DK355+200 as the project background, the Midas/GTS software as the calculation software in this study, through complicated by the numerical calculation, a simple calculation method for the composite modulus calculation of the composite foundation with DDC in the collapsible loess areas, providing basic parameters for the settlement calculations, and accordingly making optimized design for the composite foundation with DDC in this area.Making analysis on the a lot of scene research data and a wealth of testing and monitoring information, referring to many reference literature at home and abroad, taking the numerical calculation as the main research methods, through the calculation of the separation formula of the piles and the soil among piles, the stratified settlement of composite foundation is achieved; according to the settlement of monolayer composite foundation, each layer composite modulus can be inversed; the pile modulus, the modulus of the soil among piles, the replacement rate and the relationship of its corresponding single-layer composite foundation are explored, which will provide the expression of the composite modulus of the composite foundation with DDC in the collapsible loess areas; the formula proposed in this paper will be proved reasonable by taking the composite modulus calculated through the composite modulus expression in this paper as the basic parameters and by using the settlement of the composite foundation along the testing segment.Based on the single-layer composite modulus achieved by the inversion, by using the settlement control design, the design of composite foundation with DDC along the Zhengzhou-Xi'an Passenger Line in the collapsible loess area has been optimized.