Study On Mechanical Behavior Of Expansive Soil In Southern Shaanxi Under Dry-Wet Cycle

Slump of expansive soil slopes has been plagued by engineering construction in related areas.Under the action of atmospheric wet and dry cycles,geological disasters such as landslides often occur in expansive soil areas.There have been many advances and breakthroughs in the research on the shear strength characteristics of expansive soils in expansive soil regions,and many engineering problems have been solved.At present,the research on the strength of expansive soils is concentrated in the southwestern region of China.There is less relevant experimental research on expansive soils in southern Shaanxi.The shear strength tests of expansive soils also use direct shear tests.Compared with triaxial tests,the wet-dry cycle cannot be well revealed The stress-strain relationship under the action,and the strength research is mostly analyzed from the qualitative perspective,and the quantitative research is less.Based on the conventional triaxial tests,this paper designs a new indoor dry-wet cycle simulation preparation method to carry out experimental research on the physical and mechanical characteristics of expansive soils in southern Shaanxi,and obtains the relevant basic indicators and expansibility.The macro change of specimens and the relationship between stress and strain under the influence of cycling;the effects of dry-wet cycles and moisture content on peak stress were fitted by a function,in which the number of wet-wet cycles and moisture content were negatively correlated with the peak stress;The degree of peak stress reduction in one dry-wet cycle,although the subsequent cycle stress also decreased,but the amplitude decreased.Finally,the experimental data were used to study the effects of dry-wet cycle and moisture content on shear strength parameters.The dry-wet cycle effect greatly reduced the shear strength of expansive soil,which was mainly reflected in the reduction of cohesiveness of expansive soil,a decrease of 59.93%,and The internal friction angle only decreased by 3.3 °;the degradation effect of moisture content on cohesive force was analyzed.The cohesive force decreased linearly with the increase of moisture content,and the moisture content of non-dry and wet cycle samples increased by 3%.The cohesion is reduced by 7%,and the subsequent cycles have a similar linear relationship.However,as the water content increases,the cohesive force decreases and the magnitude of the cohesion decreases,which will evolve from a linear relationship to an exponential relationship.The thesis is of great significance to clarify the stress-strain and strength attenuation of expansive soils in the southern Shaanxi under the action of atmospheric dry-wet cycles.It lays a foundation for further research on the degradation of expansive soils under dry-wet cycles and provides a theoretical basis for local engineering construction.