Influence Of Meso-microstructure On Mechanical Properties Of Guiyang Red Clay

The red clay formed by the weathering of carbonate rock is the main foundation soil in Guizhou Province.It has poor physical properties such as high water content,high void ratio and high liquid limit,but at the same time,it has high engineering mechanics such as low compressibility.Strength can be used as a good building material and plays an important role in regional economic development and engineering construction.Due to the special physical and mechanical properties of red clay,a large number of engineering disasters such as uneven settlement,immersion cementation and water loss and cracking have occurred,which makes the construction of the project difficult to carry out smoothly.Existing studies have shown that the special physical and mechanical properties of red clay are closely related to its internal structural characteristics and evolutionary laws.The complex structure of Guiyang Red Clay is formed by a combination of various geological forces,which is different from the general soil.Red clay structure is the focus and frontier of current research,and it is difficult to analyze and describe it with general research methods.Therefore,how to establish the relationship between the structural changes of Guiyang red clay and various nonlinear mechanical behaviors caused by it,considering the influence of structural properties on its macroscopic mechanical properties and engineering properties,has important theoretical and practical significance.In order to clarify the medium-microscopic mechanism of the macroscopic mechanical strength and deformation characteristics of Guiyang red clay,and to consider the difference between the macroscopic mechanical properties of Guiyang remolded red clay under different confining pressures and different dry densities,the non-consolidation of Guiyang red clay is not Macroscopic and microscopic tests such as drainage triaxial shearing,N₂ adsorption testing and electron microscopy scanning tests,analysis of the difference between the macroscopic mechanical strength and the remodeling of soil samples due to different particle morphology,pore structure and distribution.The specific research contents are as follows:?1?The special mesoscopic physical parameters and formation causes of Guiyang red clay were studied.It is believed that its special physico-mechanical properties are related to its joint-contact-combination relationship with internal particles and pores.The medium-microstructure model of Guiyang red clay was preliminarily established,and quantitative analysis was carried out using quantitative parameters such as water content ratio.Quantitatively,the particle size is less than 10?m,which is about 90%of the total mass.The pore volume and pore size are mostly distributed between 2-50 nm.?2?The macroscopic mechanical properties of the original and remodeled samples of Guiyang red clay under UU test conditions were studied.The differences between stress and strain curves,shear strength characteristics and macroscopic failure modes of undisturbed and reshaped samples at different dry densities and different stress levels were compared.The stress-strain curves of the undisturbed and remolded samples show obvious strain softening and hardening characteristics respectively;under the same dry density conditions,the cohesive force of the undisturbed soil is higher than that of the plastic,while the internal friction angle is slightly different.It is lower;the destruction of the undisturbed soil has obvious shear rupture surface,and the remolded soil has bulging deformation.?3?The characteristics of contact-connection-dispersion of Guiyang red clay granules and pores are given.It is found that the Guiyang red clay granules are composed of a loose-grained group,a curved sheet-like layer and a flower-like ellipsoid.The particles are formed by a combination of point contact,line contact,surface contact and inlaid contact to form a flocculated structure,a honeycomb structure and a pseudo-spherical structure.Interstitial pores and intragranular pores.The N₂ adsorption-desorption isotherm is of type IV,H₃ hysteresis loop.By preparing10¹5ml of sodium hexametaphosphate solution with a concentration of 2%,the particle size dispersion effect is best when the temperature is controlled at 40°C.It is found that when studying the microstructure of Guiyang red clay based on SEM image processing,the magnification should be controlled between 2000³000 and the threshold should be 140¹80.?4?Considering the particle characteristics,pore distribution characteristics and intergranular cementation model,the response of the interstitial-microstructural parameters of different strains under macroscopic mechanical loading conditions is analyzed.Based on the fractal model of porous media in rock and soil,the average structural factor f_s is introduced.The macroscopic physical and mechanical parameters such as the porosity of Guiyang red clay were predicted more accurately,and the evolution law of the medium-microstructure under macroscopic mechanical conditions was analyzed.The special physical and mechanical properties of Guiyang Red Clay are closely related to the interfacial-microstructure formed by the particle-pore structure,which is the fundamental factor determining its macroscopic mechanical properties.The research results of the paper illustrate the influence of the structural properties of the soil on its macroscopic mechanical properties.The macroscopic mechanical properties and the micro-mechanical deformation mechanism of the Guiyang red clay are discussed,which plays an important role in understanding the structural properties of the Guiyang red clay-The relationship between the microstructure parameters and the macroscopic physico-mechanical properties gives a reference to the method.