Study On Meso-mechanism Of Industrial Alkali Residue To Improve Typical Expansive Soil In Yunnan

Expansive soil is a kind of highly plastic special soil with hydrophilic minerals as the basic mineral component.It has strong characteristics of water absorption expansion,water loss shrinkage and cracking.It is because of its special engineering nature that it often causes damage to buildings or structures built on expansive soil foundations.Therefore,in the construction of expansive soil areas,it is necessary to improve the expansive soil to meet the requirements of engineering construction.This paper mainly studies the basic properties,microstructure and improvement methods of typical expansive soils in Mengzi area of Yunnan Province.Through physical property tests,expansive tests,SEM scanning electron microscopy and XRD tests,industrial alkali slag and other modified admixtures(cement)are discussed.,lime,cement + industrial alkali slag,lime + industrial alkali slag)on the improvement of Mengzi typical expansive soil in Yunnan and the microstructural changes of the expansive soil before and after improvement.The paper relies on the geotechnical laboratory of the School of Architecture and Planning of Yunnan University and the Modern Analysis Center of Yunnan University to conduct relevant experiments to obtain the best improvement method for Mengzi expansive soil.The specific research contents are as follows:(1)Perform particle grading test,liquid plastic limit test,compaction test,free expansion rate test,expansion force test and shear strength test on Yunnan Mengzi expansive soil and modified soil to obtain different modified admixtures.The improvement effect of Mengzi expansive soil under different mixing ratios,and the best improvement scheme was compared and analyzed.(2)SEM electron microscopy and XRD tests were carried out on the Mengzi expansive soil in Yunnan before and after the improvement.The microstructure characteristics of the expansive soil and the microstructure changes after the improvement were also confirmed.The mineral composition changes before and after the improvement of the expansive soil were also clarified..The research results of the paper show that:(1)The effect of industrial alkali residue on the physical properties of Mengzi expansive soil in Yunnan is obvious.When the blending ratio is 30%,the mass fraction of the modified expansive soil after adding the modified material decreases continuously,the quality of the powder and the grain of the sand The score increased continuously;the plastic limit increased to 36.5%,the liquid limit decreased to 41.8%,the plasticity index decreased to 5.3,much less than 10;the maximum dry density was 1.42g/cm3,and the optimum moisture content was 19.43%,both smaller than the self-expansion The soil has an optimum moisture content of 23.82%and a maximum dry density of 1.55 g/cm3.(2)The industrial alkali residue has obvious inhibitory effect on the expansion and contraction of Yunnan Mengzi expansive soil.When the blending ratio is 30%,the free expansion rate of the modified soil is only 5%,far lower than 71%,which is also muclh lower than the table.2-4"Technical Specifications for Buildings in Expansive Soil Construction AreasM(GB50112-2013)gives a standard of 40%critical expansion rate of expansive soil;expansion force is only 16KPa,far less than 242KPa;shear strength index cohesion and internal The friction angles are 120.26KPa and 39.64°,which are much larger than the cohesive force of 6.98KPa and the internal friction angle of 13.31“.(3)The Mengzi expansive soil is mainly matrix-like microstructure.Under the electron microscope,it can be seen that the expansive soil has continuous and non-directional distribution of clay matrix characteristics,and the clay material is agglomerated aggregates with surface,surface and surface.Edges,edges and edges.The structure is coupled to agglomerated,transitional,and hybrid(cohesive and in-phase).The matrix-like microstructure is relatively loose.When industrial alkali slag is added,most of the aggregates are aggregated into one large particle,and the granular and more viscous matrix surface and surface,surface and edge,edge and edge structure A lot of compaction,the overall strength is relatively large.The addition of industrial alkali slag has obvious improvement effect on Mengzi expansive soil.When the blending ratio is 30%,the free expansion ratio is 5%,and the montmorillonite content is 6.12%,which is lower than the expansion joint construction area in Table 2-4.At this time,the modified soil of Mengzi expansive soil basically loses its expansion performance.