Research On Load-bearing And Deformation Characters Of Composite Foundation With Rammed Soil-cement Pile In Collapsible Loess Regions

The composite foundation of Rammed Soil-cement Pile is a new type of compositefoundation in recent years. Because of its convenient construction, controlling qualityeasily, good effect of reinforcement, low cost, the composite foundation of tampedconcrete piles is widely used by engineering field. At present, this method of foundationtreatment is studied less than others. This paper mainly studies the bearing capacity andsettlement, and provides certain reference value to following buildings.In this paper, it summarizes the reinforcing mechanism of Rammed Soil-cementPile, several important calculating methods in settlement calculation about compositefoundation of Rammed Soil-cement Pile. When comes across settlement calculation, itshould be considered in the effect of underlying layer in the process of the piles.By observing the settlement of a high building in the course of construction, thispaper studies the settlement about the composite foundation of Rammed Soil-cementPile in construction. By analyzing the subsidence curves, it finds that settlement value isgreater than the other parts in settlement joint, and comes up with the solution in thedesign and construction. When the subsidence curves are stepped, it results from theeffect of cushion and the asynchronous piles group. Adopting hyperbolic model,exponential model and gray system model, the paper has made a predicted researchabout the settlement of single pile static load test.It fits the subsidence curves of test points and makes a conclusion that it can predict the settlement correctly by using the method of hyperbolic model to test thesingle pile static load. When the external factors of effecting settlement are more, thegray system can get more accurate forecasts by introducing new information.By comparing the settlement of single pile static load test and the actualconstruction, this paper analyzes in detail the reason of the difference. It concludes thatthe load at1.5m depth attenuates to11.9%in single pile static load test, while thisbuilding attenuates to11.9%in the depth of30m.This paper studies the evaluation method in the compacted effect of the pile soiland concludes that it can reflect the compacted effect of the pile soil by adapting thetechnical specifications of building ground treatment (JGJ79-2002). It analyzestheoretically the feasibility of detecting the cement pile using low strain.Using the method of numerical simulation, the paper studies the compositefoundation of four piles and the effect of cushion thickness. It concludes that thecement-soil cushion should neither too thick nor too thin, and the appropriate thicknessis between300mm and500mm.