Study Of The Bearing Capacity And The Settlement Of Deep Mixing Composite Foundation

Deep mixing technology used in reinforcing and handling of soft soil foundation for only twenties years, and was attention by many engineers studied in geotechnical engineering for high speed of development and wide application. We must analyze it deeply for the application level of deep mixing engineering exceeding present situation of the studying level of theory.This paper consultes and commentes scientific and technical literatures, which are relative to deep mixing composite foundation, and graspes studying developmental direction of it both here and abroad, based on experimental researches, numerical calculation, analysis and summary of theory, by combination of engineering example of deep mixing piles, and analyses the bearing capacity and the settlement of deep mixing composite foundation all sidedly.The primary studying works and characteristics:1) To summarize reinforcing theory of cement mixing pile composite foundation2) To analyze the primary mechanics characters and changing rules of cement mixing pile, based on analysis of test data both indoor and outdoor.3) To discuss siding frictional resistance, ending resistance, ultimate bearing capacity of simple mixing pile and effectiveness factor of grouped piles, loading ratio of soil between piles under cushion cap of grouped piles and stress ratio of pile and soil and so on, and use many computation method and experimentation method to ensure bearing capacity of mixing piles composite foundation.4) To point out and analyze eight sides flaws and problems of the bearing capacity calculation method of mixing pile compositefoundation which ensured by national and normative method/ formula.5) To apply test results of loading tests and a few settlement observation data, use gray theory to predicate ultimate bearing capacity of deep mixing piles, actual example demonstrate engaging between theoretical predicted value and actual value.6) To apply groovy layerwise summation method to discuss entity piles method, double foundation method, equivalent layerwise summation method and consolidation theoretical method and so on, especially by combination of engineering example, use FEM to calculate or discuss the settlement and changing rules of composite foundation.7) To discuss problems of critical length of composite foundation by combination of engineering example and numerical analysis method, and analyze the contrast of critical length between simple pile load and most area load of composite foundation, not only critical length of composite foundation is relative to modulus ratio between piles and soil, but also upside load distribution area of composite foundation. Optimizing select of the length of mixing piles and design method of the settlement control are new methods of deep mixing composite foundation design calculation at present.