Multi-scale Evolutionary Mechanism Of Expansive Soil Under Wet And Dry Cycles Role

Expansive soil is a kind of hazardous soil that is obvious to all in engineering and has great engineering danger.With the rapid development of my country’s social economy,a series of projects that are conducive to production development,such as infrastructure for people’s livelihood and ecological environment,are also booming.In the construction and production of these projects,this kind of widely distributed "special" soil may be encountered at any time.Regarding this kind of "cancer" in engineering,domestic and foreign experts and scholars have related research on it.However,there are relatively few studies on the relationship between the macroscopic and microscopic expansive soils,and most of them are aimed at A sample study of expansion potential.Based on this,this paper collects and samples different expansive soils in the Pingdingshan area,and selects two soils with expansive potential to explore the evolution mechanism between the macromechanics and the microstructure.Specifically,it mainly involves the following aspects of work:(1)Through indoor tests,the free swelling rate,particle gradation,optimal moisture content and dry density of the retrieved different expansive soils were determined.Based on this,the subsequent shear strength,surface cracks,and internal pores were determined.(2)Use GTCS(STX-600)large-scale vibrating triaxial instrument to conduct shear strength compression test on expansive soil after dry-wet cycles,sort out the data obtained from the test,and obtain information about different expansive soils in different confining pressures and number of dry-wet cycles Under the peak stress,the corresponding shear strength index,cohesion and internal friction angle can be derived from this.(3)After the dry-wet cycle of the sample,the surface cracks were extracted and saturated with kerosene,and then the nuclear magnetic resonance test was started.Analyze the obtained relevant data to get the relationship between surface cracks and internal pores.(4)Use the knowledge of regression analysis to find the relationship between the macromechanics and the microstructure of expansive soil.Through the above work,the main results and conclusions obtained are shown as follows.The parameters and analysis obtained in the experiment can provide useful help for expansive soil engineering in the future.(1)Through indoor experiments,the gradation of the soil samples taken this time was good,and the adverse effects of uneven particle distribution on the subsequent research process were ruled out.(2)After the triaxial test,it is found that the shear strength evolution of different expansive soils is roughly the same.The difference is that the cohesive force of the medium expansive soil is lower than that of the weak expansive soil.The increase in the number of cycles decreases,but the fluctuation of the internal friction angle is not large.(3)The development process of expansive soil during the entire dry-wet cycle is summarized into three stages: the first two dry-wet cycles are called the cracking period,the second to fourth cycles are the crack-through period,and the fourth to sixth times are called the cracking period.For a plateau.A simple linear regression analysis was performed based on the obtained data,and it was found that the model xy-(28)274.034.1 was satisfied between the surface cracks and the internal pores.(4)A model between macro-mechanics and micro-structure is established.When the different expansive soil maps were analyzed separately,it was found that the obtained formulas were extremely low in interpretation and did not meet statistical significance.Therefore,the data obtained from soils with different swelling potentials are integrated and analyzed.Based on the basic theory of multiple linear regression models,SPSS uses the cohesive force obtained through the triaxial test as the dependent variable,and the relevant characterization parameters obtained from the microscopic test.As an independent variable,a model formula between the macroscopic and microscopic expansive soils was established,and it was found to be statistically significant after verification.