| Sichuan is one of the provinces which the red beds distribute extensively in the southwest region of China. The red beds, primarily distribute over Sichuan basin and its borders, are about 1.65 billion square kilometers in total. With high absorbance ,great settlement, and poor stability feature in this red beds soft soil foundation area, to build a airport runway or a express way, this kind of foundation must be strictly limited its uneven settlement besides be guaranteed its stability and forms, therefore, this article , with Luzhou airport for example, by researching on the very red soft soil foundation engineering geological properties and its engineering effect, has a very vital significance on how to select the foundation treatment programs economically and effectively and also on how to find a balance between the engineering security and economy on the premise of its quality and economic benefits in the future airport construction.This paper adopts a method of the systems engineering geology, using theoretical analysis and numerical simulation to study the engineering geology features and its engineering effect of Luzhou airport red beds soft soil foundation. However, before all those studies start, to know the regional geological tectonic environment, the ground of geological structure, and its circumstance, and also to know each physical, mechanical parameters of the soft foundation in detail, must be done. According to the research above, the main conclusions are as following:(1)The distribution and composition of red beds soft foundation in study area is very uneven,mainy ditributed in gully and the thickness is generally 3～5 meters.The plastic state is mainy plastic,on the surface or oveburden interface ,there is another layer of soft plastic soil whose thickness 1～2m. The mineral composition of the soli are mainy contain quartz, feldspar, illite, montmorillonite etc.(2)In the same thickness of foundation soil, the form of consolidation is not complete too much influence.on consolidation time.(3)The final settlement quantity of the five modles respectively is modle 1(17cm),modle 2&3(23cm),modle 4(28cm),modle 5(20cm).If there is soft plastic soil in the foundation, the sedimentation rate and the final settlement quantity will be much bigger.However, there is hardly obvious difference for the modle2&3 in their sedimentation rate and final settlement quantity.(4)The foundation which contains soft plastic soil must have its shear breakage happened in the soft plastic soil part, not in the plastic soil part.(5)The foundation which contains no soft plastc soil is much stable than that containing. For the foundation model containing soft plastc soil, it is the most dangerous state when thep soft plastic part is at the surface. And it is safer when it is in the middle than it in the bottom.(6)Comparing with the other models, to slowdown fill geogrid ratio and set back beams can be two most suitable ways for model 2 to improve its stability at maximum.(7)Through changing the position of shear damage, back beams can make the shear breakage happen in the filling body internal when the foundation soil property is good. But when the foundation has soft plastic soil, the existence of the back beams can help the shear breakage belt length outspread, thus improve to the stability of the slope.(8)Under the effect of fill load, the uneven settlement of the natural foundation soil is remarkable. Especially, the different settlement is most obvious at the border of the bedrock and soft foundation and the border between the digging fields.(9)Changing fill macadam can effectively control the total subsidence and thus reduce the differential settlement while laying geogrids could not reduce the total amount of settlement, but could reduce the different settlement and make the foundation more uniform. |
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