The Research On Characteristics Of Red-mudstone Packing Strength Of Le Shan Airport

In recent years, the countries has planned lots new construction, renovation and expansion of the airport project in southwest China. As the planning and constructing airport are mainly distributed in Chuanyu red bed region, they inevitably involved in the condition of red soft rock engineering. Relying on Leshan airport and on the basis of geotechnical engineering work, this paper analyzes the mudstone under different grain size of broken fractal characteristics of the filler and its impact on the compaction characteristic of packing through the compaction test. Then, combining with the relevant specification requirements, this paper designed medium shear test under the condition of different water content, different degree of compaction and particle-size distribution for studying on the strength characteristic of red-mudstone filling in Leshan Airport. and proposed the related parameters and the suggestion for airport designing and constructing reference. Through analyzing the test data we mainly obtain these following conclusions:(1) The compaction progress making the mudstone coarse aggregate(?>5mm) over broken, reducing its content and the content of fine aggregate increasing, then the overall grade is improved general. When the water content is constant, the coarse aggregate content(P5L) and the broken rate(Bg) after compaction increased linearly with the increase of the coarse aggregate content(P5L) before compaction. When P5 Fis a constant value, the P5 L and Bg increased with the elevated of water content, and, when the water content is over 10%, The Bg will flatten out.(2) The Heavy Compaction Curve of mudstone filling coarse showed not a single peak curve, but more a bimodal type, and the peak is slightly higher in high water content than low water content. Combining with the characteristics of mudstone particle breakage, the root causes of the bimodal peek is the change of broken, and with the increase of water content(ω<10%), the mudstone particle soften followed, particle breakage is more obvious, the gap is more likely to be filled by fine-grained soil,making the dry density increase. In addition, with the increase of content coarse aggregate content, the maximum dry density increases, when the content of coarse grain P5F=90%, the maximum dry density is 2.18g/cm3,and the optimum water content of 10.61%.(3) Mudstone gravel filled is a good material of fractal, after compaction the fracture fractal dimension is 2.4285 to 2.4285. Basing on the fractal dimension of fractured respectively with the grading(Cu), coarse variation(△P) before and after compaction, the broken rate(Bg) and the peek dry density, we learned that when 2.48<D<2.53, the P5 variation is largest, and broken rate is highest. After compaction the grading is good, and the dry density is largest.(4) The Curve of Shear stress-Shear displacement shows that the peek shear stress distribution commonly between the shear displacement Hτp=2-5mm commonly, and with the increase of normal stress, the peak shear stress increases. Generally before the shear displacement meet the peak shear stress, the shear stress and the shear displacement relationship linear increase. Later, in low normal stress, the shear stress does not reduce greatly with the increase of the displacement, but tends to stable in residual strength under the normal stress; When the normal stress is high, the shear stress reduces greatly with the shear displacement increasing, then it tends to stable in the value around the residual strength shear under unique normal stress.(5) Under the effect of full water, the mudstone filled soften, making shear strength significantly reduce, but along the shear plane, due to the mudstone coarse particle shared most of the shear stress and being cut up, to a certain extent, this phenomenon improves the shear strength of mudstone filler, making that even in saturated state, mudstone filler remained high internal friction Angle(33.58 °). The shear stress increases with the compaction degree increases, and increases faster when the compaction degree is higher. from 85% to 98% under the compaction degree of amplitude is more remarkable with the increase of the Angle of internal friction. The shear strength of the mudstone filler changes with the content of coarse grain and coarse grain content, the cohesive force reduces and internal friction Angle increase, then the corresponding change rate.(6) The shear strength and the bearing capacity of foundation can meet the demand of airport construction on the condition of reasonable designed. But due to mudstone filler soften, and internal friction Angle is sensitive to the filled slope, when constructing in complex valleys we should control the water content of mudstone filler around 10%, and making the waterproof treatment good, at the same time raising the internal friction Angle by improving the degree of compaction of the filling body, to ensure the slope stability.