Study On Strain Rate Effect Of Expansive Soil Mechanical Properties And Embankment Stability Annlysis In Nanyang

Expansive soil is widely distributed,and its special mechanical properties which is easy to threaten the geotechnical engineering,such as embankment,slope and foundation,but the rheological characteristics of soil have a great influence on the mechanical properties of soil.At present,the research on rheological properties of soil is mostly focused on soft soil,and the research on hard clay is relatively rare.As a typical hard clay,the rate effect of mechanical properties of expansive soil is very important.In this paper,the expansive soil of Nanyang Inner Deng Expressway Section is taken as the research object,taking the direct shear tests by controlling these factors:the days of soaking and consolidation,the water content of the sample,the shear rate.Besides,taking the triaxial consolidation and undrainage test by controlling the strain rate.According to the test results,analysis of the change law between shear strength curve,strength index and strain rate of expansive soil is analyzed.Finally,combining MIDAS GTS NS finite element software to analyze the stability of expansive soil embankment slope.As a result of the above study,the following main results have been obtained:(1)In the electrochemical impedance spectroscopy test,the solution resistance _sR and charge transfer resistance_tR of the equivalent circuit parameters decrease wit h the increase of dry density,and the double layer capacitance CPE-T increases g radually.Moreover,a good linear relationship was obtained between the dry densit y of expansive soil and the _sR,_tR.Therefore,it is feasible to characterize the m icrostructure of expansive soil by electrochemical method.(2)About direct shear tests at different strain rates,two experimental groups are formulated:undisturbed expansive soil consolidated in water for 1 and 10 days,remolded expansive soil with initial moisture content 12.6%and 22.8%for the same dry density.There are three conclusions:1)When the shear rate was 0.02mm/min,all stress-strain curves showed a weaker strain softening trend,while 0.8mm/min and 2.4mm/min showed a significant strain hardening trend.2)Under the same conditions,the shear strength of soaking consolidation for 1 day is always greater than that of soaking consolidation for 10 days,and the shear strength of water content 12.6%is always higher than that of water content 22.8%.3)The shear strength,cohesion and angle of internal friction increase with the increase of shear rate,and the effect of shear rate on cohesion is greater than that on the angle of internal friction.(3)Taking the remolded expansive soil with initial moisture content 12.6%and 22.8%for the same dry density as the research object,the triaxial consolidation undrained test was carried out with different strain rates.There are three conclusions:1)When the strain rate increased from 0.0015%/min to 15%/min,all stress-strain curves showed strain hardening trend.2)When confining pressure is 25kPa and 50kPa,the peak stress increases with the increase of strain rate.However,When confining pressure increases to100kPa and 200kPa,the correlation between peak stress and strain rate is poor.3)With the increase of strain rate,the cohesive force increases and the internal friction angle decreases;In addition,between 0.15%/min and 1.5%/min,there is a strain rate which causes the soil strength index to change suddenly.(4)The stability of embankment is greatly influenced by the soil cohesion force and is less affected by the angle of internal friction.The conclusions obtained in this paper can be used for provide some references about the expansive soil’s strain rate effect of shear strength and the stability analysis of embankment.