Study On The Effect Of Piles And Soil In Composite Foundation

Multi-type-pile composite foundation is the synthesis of different types of piles, and the harmonic design in terms of technology and economy. Many problems and topics remain open and need further research on its theory and application in China.To address questions on the designing of multi-type-pile composite foundation, a series of spot-tests were carried in the geo-technique laboratory of CABR and a building site in Beijing. Based on the analysis of stress-ratio, bearing ratio and bearing capacity factors about piles and interpile soil in multi-type-pile composite foundation, the author makes some suggestions which can serve reference for further project engineering.â‘ Bearing behavior of piles and interpile soil in multi-type-pile composite foundation.The results of the spot-tests showed that, the bearing capacity factor of the major piles, γ₁, and the same factor of the minor piles, γ₂, are less than 1.0(γ₁≈0.62-0.82,γ₂ ≈ 0.64 -0.87); the same factor of the interpile soil, β, is more than 1.0 (β≈ 1.13-1.34), while the load on the multi-type-pile composite foundation is equal to its characteristic value of bearing capacity, no matter whether one-type-pile or multi-type-pile composite foundation is used.â‘¡Calculation method of multi-type-pile composite foundation bearing capacityAccording to the test, the bearing capacity of multi-type-pile composite foundation should be:in which the factor γ₁,γ₂,β should be in the range described in â‘ . When making γ₁ =γ₂= 1.0 and β=0.95, which is a common practice in project engineering, the estimated value and the test result are not far apart from each other.â‘¢Composite modulus of multi-type-pile composite foundationComposite modulus is the capacity of composite foundation to resist deformation. It is certain times of the modulus of compressibility of soil, and it can be used in the calculational method of composite foundation deformation. Its function is similar to that of modulus of soil compressibility. If using the modulus of compressibility of pile, E_p, into the calculational method of composite foundation deformation, the result will be too far away from test result.â‘£Calculation methods for deformation of multi-type-pile composite foundationThe calculation method of deformation recommended in this paper is reliable, easy to learn and operate, and of wider range of application in project engineering.Besides the above main topics, some preliminary study and discussion on the test and inspections of composite foundation in engineering are also included in this article.