Analysis Of Engineering Characteristics Of Granite Residual Soil And Stability Of Roadbed Slope In Linshuang Expressway

With the rapid development of urban road construction,the construction of expressways and other projects has a strong impact on the topography of various regions,especially in the mountainous areas.Granite residual soils are widely distributed in Western Yunnan.Because of strong weathering,these soils have strong structure and disintegration.When the cementation between soils is weakened or destroyed,it is very easy to cause a series of disasters such as landslides.In this paper,18 granite residual soils located in Linshuang Expressway are taken as research objects.The structural characteristics of granite residual soils are analyzed by means of field survey and indoor and outdoor geotechnical tests.At the same time,the engineering related to granite residual soils in Lincang area is analyzed by statistics and comparison,so as to further analyze the engineering characteristics of granite residual soils for slope stability in qualitative impact.In this paper,the engineering characteristics of granite residual soil are analyzed from the point of view of geotechnical damage mechanics.Laboratory geotechnical tests were carried out on undisturbed and remolded granite residual soil samples of Linshuang Expressway slope,including basic physical and mechanical properties.The relationship between the physical and mechanical properties and their structural properties was analyzed.The results show that the indexes of undisturbed and remolded samples of granite residual soil are higher than those of remolded samples in various parameters,especially in strength index,cohesion and internal friction angle.This shows that when the soil structure is destroyed,the strength of the granite residual soil decreases.Because of the existence of structure,the soil itself can resist the damage caused by external forces.When the whole soil sample is weakened or destroyed,its strength tends to residual strength.Consolidation and compression tests show that the existence of structural properties decreases the compressibility of undisturbed soil samples and increases thecompression modulus,whereas that of remolded soil is the opposite;comprehensive structural potential index can better describe the structural strength of granite residual soil.The current situation of soil slope stability analysis methods is mainly based on limit equilibrium,limit analysis and numerical analysis.Among them,the strength reduction method based on finite element method and FLAC3 D method based on finite difference under the branch of numerical analysis have obvious advantages compared with limit equilibrium slice method,which are more accurate and convenient,and will be the development trend of future three-dimensional research.Based on the test data,a three-dimensional geological model of granite residual soil slope of Mengku interchange slope is established.The stability of granite residual soil slope of Linshuang Expressway is analyzed,and the effects of rainstorm conditions,excavation unloading and structure on slope stability are simulated.The results show that when the structure is damaged by excavation unloading or rainstorm infiltration,the stability of the slope decreases;on the structural side,the residual soils of two types of granite,silty clay and silty clay gravel,decrease both before and after the structure is damaged by choosing corresponding numerical values,and it is found that they are difficult to meet the actual safety and need to be treated safely and ensure safety.Further research shows that the engineering characteristics of Linshuang high-speed granite residual soil and the instability mechanism of soil slope will have important reference value for future engineering construction and slope treatment in Western Yunnan.