Study On Disintegration Mechanism Of Dongchang Highway Red Sandstone And Improvement Of Roadbed

The red sandstone has the characteristics of water disintegration,easy weathering and crushing,and it is very difficult to resist erosion,weathering resistance and engineering stability.This paper takes Jiangxi Dongchang expressway along the full weathered red sandstone as the main object of study on disintegration characteristics of red sandstone,and the cement and lime as the main additive test of improving roadbed filling.The main conclusions of this paper are as follows:?The chemical composition of red sandstone are mainly SiO2,Fe2O3,Al2O3,CaO,K2O,SiO2,Fe2O3 and Al2O3 which have high content;montmorillonite,illite,kaolinite and other major clay minerals in red sandstone.These different chemical composition and mineral composition of the physical and chemical properties the red sandstone has an important influence,which is also an important reason for the disintegration.?The strongly weathered red sandstone is easy to disintegrate in water,and has different disintegration characteristics in different water environment.The disturbance of red sandstone under the condition of water flow in the violent disintegration.The degree of compaction,particle size and water content have important influence on the red sandstone specimens.? The chemical composition of the red sandstone before and after the disintegration did not change much,mainly in the water involved in the red sandstone minerals and cements dissolved caused by microstructure changes.In the macroscopic manifestation of red sandstone rock particles between the loss of adhesion and disintegration of the overall crushing to the massive,granular,mud-like changes in the phenomenon.?Strong weathering red sandstone with different mix of lime,cement improved physical,mechanical and other properties have been greatly changed.Lime and cement have different effects on red sandstone,and there is an optimum amount of lime-improved red sandstone,rather than the better.The experimental results show that the content of 7%lime is the best,and the engineering properties of the red sandstone after the cement increase gradually with the increase of the content.Taking into account the engineering economy should choose a reasonable amount of this test shows that the 5%cement content is the most reasonable..?Through the analysis of the mechanism of red sandstone,it can be seen that the improved red sandstone after physical and chemical action has higher strength and better water stability.Through the microstructure and chemical reaction process analysis,it can be seen that the incorporation of lime and cement in the red sandstone internal chemical reaction to produce gel material.Filling between the red sandstone particles increases the degree of adhesion between the soil particles and reduces the porosity between the particles.?It is necessary to reduce the disintegration activity of red sandstone and reduce the disintegration activity of red sandstone after filling to ensure the stability of red sandstone subgrade after construction.To use the red sandstone disintegration has irreversible characteristics,in the filling before the pre-disintegration and raking measures to eliminate or reduce the red sandstone disintegration activity.After the pre-disintegration and can not completely eliminate its disintegration characteristics,it is necessary to improve the red sandstone filler after the pre-disintegration,select the leaching amount of 7%lime or 5%cement to improve the red sandstone Disintegration characteristics.Or the use of appropriate roadbed structure and form to reduce the participation of water,will be filled after the red sandstone water activity to a minimum,so that the basic water activity is eliminated.?Based on the existing engineering data,the red sandstone disintegration test and indoor improvement test,the technical parameters and quality inspection contents of the red sandstone subgrade construction are summarized.Quality inspection shall be carried out from the aspects of appearance inspection,compactness test,compaction settlement difference and subgrade strength.