Application Research Of Gravel Pile Composite Foundation

With the rapid development of civil engineering in China, gavel pile is widely used in the soil improvement of soft soil foundation. Especially for high seismic intensity area, the gavel pile has the anti-liquefaction effect that is formed by its compaction, vibro-density, drainage and decompression, preparatory shock, reinforcement,and so on.. The method of gavel pile is better than other kind of foundation treatment method.In this paper,the design theory and and engineering application of the existing composite foundation are summarized and analyzed.Pile-soil stress ratio,the composite modulus, bearing capacity and deformation calculation methods of the vertical reinforcement of composite foundation of the existing are summarized and analyzed.Their respective advantages and disadvantages are analyzed and evaluated and some reasonable suggestions are proposed.Established thick-walled cylinder model in consideration of squeeze effect of gravel pile. Considering the different tension behavior of gravel pile and soil mass around it as well as the influence of increasing foundation bearing capacity which is caused by intermediate principal stress during the swelling process of pile, this paper will apply twin-shear unified strength theory of plane axisymmetry and give an expression for unified solution of ultimate bearing capacity of composite foundation of single gravel pile, and the calculation methods of gravel pile composite foundation's settlement was improved. The experiment has guiding meaning for the theoretical research and engineering practice of gravel pile composite foundation.The soft foundation of two oil tank is treated by vibration sinking gravel piles. The detection results show that: The compression of sandy viscous soil decreased much observably and the effect is indistinctive for silt clay; The pile-soil stress ratio of composite foundation is in the range of 2-3. The SPT blow count of soil between piles after processing can be raised to more than 1.5 times of natural clay and characteristic value of composite foundation bearing capacity is increased by more than 2.3 times.