Research On Bearing Behaviour Of Composite Foundation With Rammed Tapered Cement-soil Column

This paper relies on the National Natural Science Fund " Research onthe behaviour of Geocell-flexible tapered pile composite foundation underthe flexible load (No.51108176)", experiments and numerical simulationhave been used combinately in this paper, study on the behaviour ofcomposite foundation with rammed tapered cement-soil column, analyzethe feature of geotextile reinforced cushion, the interface contact frictioncharacteristics between cement-soil and soil, finally the compositefoundation rammed tapered cement-soil column bearing behavior and so on,this paper carried out the following work.1. To reveal the actual engineering work traits of the cushion, the puregravel cushion test, the geogrid reinforced cushion test and the geocellreinforced cushion test have been operated in the large indoor model box(soft soil filled), analyzed the factors that affect the coefficient of subgrade,such as, the thickness of cushion, reinforcement materials, the quantity andthe position of reinforcement.2. In order to investigate the interface friction characteristics betweenrammed cement-soil and soil, the direct shear tests have been used in thispaper, though change the cement content, the water content of soil, thenormal stress, the curing period of cement-soil, Simultaneously,determination of the shear displacement between rammed cement-soil andsoil in the tests.3. To find the advantages of rammed tapered cement-soil column, thestatic load tests have been used in this paper, though change the wedgeangle of pile, comparative analyzed the bearing behavior among differentwedge angle of pile and cylindrical pile.The results of this study show that:1) the subgrade coefficient of view,the role of pure gravel cushion to improve the strength and stiffness of thefoundation is not obvious, and the effect of the geogrid reinforced cushionto improve the strength and stiffness of ground is not very significant, butthe geocell geocell limit lateral deformation of the soil, has a significanteffect in improving the foundation of strength and stiffness.2)When thenormal stress is small, the interface friction between rammed cement-soil and soil is small, the cement content and moisture content of soil in a smalleffect on the friction; With the normal stress increases, the interface frictionbetween rammed cement-soil and soil increases, the cement content andmoisture content of soil in a important effect on the friction, the rise withrise; with the increase of curing period, the interface friction betweenrammed cement-soil and soil increases linearly. Thus increasing the cementcontent, reducing the water content of soil, increasing the normal stress canimprove between rammed cement-soil and soil.3)the composite foundationwith rammed tapered cement-soil column work was superior traits to thecomposite foundation with cylindrical compacted soil cement column(theyhave same volume), with the wedge angle increases, the foundation bearingcapacity is increased, and increases the wedge angle can effectively deploythe soil sharing the load and the scope of the soil deployed will beincreased.