A Research Of Engineering Geological Characteristics Of Calcium Carbonate Modified Red Clay

The Guilin red clay is similar to the general red clay,and has poor engineering geological characteristics such as higher boundary water content and stronger shrinkage.Since calcium carbonate is one of the hundreds of billions of billions of industries that Guangxi will focus on,the use of superfine calcium carbonate to modify red clay is considered based on the regional characteristics and development trends.The subject mainly takes Guilin red clay as the research object,discusses the influence of light and heavy calcium carbonate on the engineering properties and mechanism of red clay,analyzes its influence on the microstructure and mechanical properties of red clay,and determines the effect of red clay modification.Good calcium carbonate and optimal incorporation rate.Analyzing the pore damage law and constitutive relationship of the calcium carbonate modified red clay with the optimal blending ratio during the triaxial shear process,the main work is as follows:(1)X-ray diffraction(XRD),p H value,specific surface area,critical moisture content and particle size distribution test of ultrafine calcium carbonate modified red clay at different incorporation rates show that the incorporation of calcium carbonate has an effect on the red clay The critical moisture content has a significant impact,resulting in significant changes in the p H value,mineral composition and specific surface area of the sample;it is found through the shrinkage test that the addition of calcium carbonate can effectively reduce the shrinkage coefficient of the red clay;the bulk density test and The compaction test shows that the red clay mixed with 5% calcium carbonate has a better particle size gradation and effectively increases the maximum dry density of the red clay.(2)Using nuclear magnetic resonance technology(NMR)to analyze the microstructure characteristics of calcium carbonate modified red clay,it is found that the pore size of the sample is mainly distributed between 5-50 nm.The incorporation of calcium carbonate mainly affects the intergranular pores and inter-particle contact surfaces of red clay.Light calcium carbonate has a greater effect on the pores of red clay than heavy calcium carbonate;the increase in dry density causes the porosity of the soil to decrease linearly.The main reason is that the number of pores(intragranular macropores and intergranular pores)larger than 50 nm in the sample is significantly reduced;when the soil sample is 95% compacted,the pores larger than10?m in the soil are greatly compressed.(3)The unconfined compressive strength(UCS)test of the calcium carbonate-modified red clay under the same compaction degree found that the blending of 5% heavy calcium carbonate and 2.5% light calcium can increase the non-confined strength of the red clay.Confined compressive strength;Consolidation undrained(CU)triaxial shear test of calcium carbonate modified red clay found that the addition of calcium carbonate will destroy the cementation between the red clay particles,resulting in weakening of the cohesive force and the strength of the red clay Reduced,but the influence of the incorporation rate is small;light calcium carbonate has a greater influence on the strength of red clay than heavy calcium carbonate.Through multiple regression analysis of the influence of microscopic pores on macroscopic mechanics,it is concluded that the change of pore size has a strong correlation with the cohesive force of red clay.The pore content of micropores and macropores is positively correlated with cohesive force,and the content of mesopores It is negatively correlated with cohesion.(4)Using NMR to analyze the changes in the pore distribution of the soil samples at different CU triaxial shear levels,it is found that the increase of the consolidation confining pressure causes the large pores of the soil to be significantly compressed;during the shearing process,the large pores in the soil sample After the content is compressed to a minimum,the small pores begin to be compressed;when the axial strain reaches 16%,the internal particle arrangement of the soil is basically re-adjusted.When the axial strain is greater than 16%,the soil structure is basically in a stable state.(5)Establish the Duncan-Chang model of the red clay modified by heavy calcium carbonate,analyze the fit of the model calculation results to the actual measured data,and introduce the density coefficient k to modify the parameters of the model to obtain a better fitting effect The modified Duncan-Chang model.