Regularities Of Distribution And Study On Engineering Properties Of Redbed Mudstone In Longquan Mountain Area

With the development of infrastructure construction in southwest China in recent years,the natural disasters caused by mudstone in the red area have aroused widespread concern among the builders in practical engineering construction.The red mudstone has the characteristics of weak water permeability,strong hydrophilicity,weak weathering resistance,easy collapse and disintegration,easy expansion of rock mass after water and significant decrease in shear strength of structural plane,engineering characteristics such as water loss and shrinkage.The mudstone distribution in the red layer is widespread,so it is of great practical significance to study the engineering characteristics and microcosmic mechanism of the mudstone with the distribution rule of the red mudstone as the breakthrough point.In this paper,the correlation between engineering parameters and microstructure of red mudstone in the area is analyzed by field survey in Longquan Mountain area,and the following results are obtained:1.By analyzing a large number of literatures and related geological data,the lithologic assemblage and the percentage of lithofacies in the main strata distribution,lithology,hydrology and mudstone strata in Longquan Mountain area were analyzed statistically.The main strata distribution For the Jurassic and Cretaceous,lithology is mostly mudstone,sandstone,siltstone and so on,and the Jurassic mudstone group is more than the Cretaceous.2.The results show that there are some expansions for the red mudstone in the two sets of strata,and the expansion of the purple mudstone in the mudstone and Shangshaximiao Formation of the GuanKou group is higher than that of the two groups.And the shear strength parameters c?? value,with the water content of the changes,are showing regular changes.With the increase of water content,the cohesive force c increases first and then decreases,that is,there is an optimal moisture content value,which is measured near the plastic limit value of the sample.The internal friction angle ? value decreases with the increase of water content.3.Mineral composition and the amount of Fe₂O₃ and the shear strength of the sample there is a certain correlation.When the contents of montmorillonite in the mudstone samples rich in clay minerals reach a certain value,the specimen mainly reflects the engineering properties of montmorillonite,The change of the content of Fe₂O₃ and the increase of the cohesion value of the montmorillonite containing mineral specimen is significant,and the decrease of the internal friction angle is also significant,but in the end,Fe₂O₃ content increases,the shear strength parameter values tend to be gentle.4.The structure type,the number of pores,the density and orientation of the microstructures,the strength of the structural coupling force have an influence on the shear strength and the expansion potential.Among them,the sheet-like structure of the lamellar structure,surface-surface stacking of the dense orientation of the arrangement,the weak structure of the connection is led to a higher expansion of a key factor.And the number of pores more,in the low water content,the shear performance is slump.