Experimental Study On Mechanical Property Of Remolded Silty Clay In Yinchuan Area Under Drying-wetting Cycles

Silty clay is widely distributed in the north and south of China.The silty clay widely distributed in Ningxia has a typical dry and wet state due to its typical climatic characteristics.70%-80%of the annual rainfall is concentrated in the summer,and evaporates from July to September.Strongly,combined with the large number of lakes in Yinchuan,the fluctuation of water level also causes the nearby soil to be in the range of dry and wet circulation,causing instability,tilting and other engineering damage to the subgrade engineering,channel engineering and foundation foundation above the soil.Regional engineering construction has a certain impact.Therefore,it is important to study the mechanical properties of silty clay in this area and explore its degradation mechanism under the action of dry and wet cycles,which provides effective parameters for engineering practice in the region.In this paper,the typical silty clay in Yinchuan area was taken as the research object,and the relevant parameters were used to prepare the remolded soil samples.The multi-factor undrained triaxial test considering the number of dry and wet cycles,compaction degree,saturation and confining pressure was carried out.The compression test and the collapsibility test were carried out to study the strength characteristics,compressibility and collapsibility.The above test indicators were analyzed by DPS to consider the multi-factor interaction.The main research results are as follows:(1)Change the soil stress-strain curve form before and after the wet-dry cycle,the soil transitions from strain hardening to strain softening,and the softening degree increases gradually after three dry and wet cycles;the peak stress in the early and final dry and wet cycles is The attenuation is higher under high saturation,and the attenuation is higher at low saturation in the middle of dry and wet cycle.After the dry-wet cycle,the cohesive force and the internal friction angle are differently deteriorated,and the cohesive force is deteriorated more than the internal friction angle.The cohesive force in the early stage of the wet and dry cycle deteriorates greatly under high saturation.The deterioration of the dry and wet medium and the end stage is low under low saturation,and the cohesion of the cohesive force with the dry and wet cycles is linear at low saturation.Regression,in accordance with the quadratic curve regression under high saturation,the correlation is good.(2)Under the univariate condition,the change of the void ratio decreases continuously with the increase of the number of dry and wet cycles,decreases with the increase of saturation,and decreases with the increase of compaction.Through the analysis of the compression coefficient of each sample,it is considered that in the process of changing the number of dry and wet cycles,soil samples have higher degree of compressibility in soil samples during dry and wet,The degree of compressibility change is high;the compressibility of high saturated soil is higher than that of low saturated soil during the whole wet and dry cycle,and the compressive coefficient of low saturated soil tends to be stable in the middle and late wet and dry cycle;Under dry and wet conditions,increasing the degree of compaction is beneficial to resist the compression deformation of the soil.After the soil undergoes the dry and wet cycle,the compaction degree is weaker and weaker against the compressive deformation of the soil.(3)It is found that in the process of dry and wet circulation of soil under various compaction degrees,the collapsible deformation rate gradually increases with the increase of saturation.For the 40%,55%,and 70%soil samples,the degree of compaction in the early stage of dry and wet can reduce the collapse deformation to some extent,and the collapsible deformation rate increases with the degree of compaction in the middle and late stages of the wet and dry cycle.The reduction is reduced,and the improvement of compaction has less effect on slowing the collapse deformation.(4)A significant analysis of the interaction between the test indicators lwas carried out.The peak stress and main effect factors were in the order of confining pressure,dry and wet times,saturation,compaction;cohesion and main The order of significance of the effect factors was dryness and wetness,saturation and compactness.The internal friction angle was only significantly correlated with the number of wet and dry times.The order of porosity and main effect factors was:compactness,saturation,The number of dry and wet cycles,pressure level;the order of compressibility and main effect factors are compaction,saturation,dry and wet cycles.The order of the collapse rate and the main effect factors is the order of dryness and wetness,compaction degree,saturation.