Experimental Study On Small Strain Dynamic Characteristics Of Bagged Silty After Freezing And Thawing

With the rapid development of subgrade reinforcement technology,soil bag embankment reinforcement technology has also gradually matured.As a new type of subgrade reinforcement technology,the geotextile bag technology has the advantages of strong restraint,reducing roadbed settlement,preventing frost heave and thaw settlement,and damping.Geotextile bags in the construction of foundation reinforcement,impervious barriers and embankment construction aspects of the application,both at home and abroad have made a great deal of success and breakthrough.In this paper,the author made a comparative analysis of the target soil bagging and bag-free by changing the number of freeze-thaw cycles,curing age and the size of the confining pressure of the resonant column.Simulate the freezing process of soils in the real environment,carry out the experiment of frost heaving and thawing,and choose a constant temperature refrigerator at-20 ℃ to make a one-way freezing box and a cylindrical stainless steel sleeve of 50mm in diameter and 100mm in height to ensure the test target Soil and soil under the same natural state,one-way freeze from top to bottom.During the freezing process,the bottom of the cylindrical geomembrane bag has very small and dense pores,which hinders the process of water absorption of the soil sample,so that the capillary water infiltrated into the bagged soil sample is less than the sample without bag soil In the melting process,bagged soil and bagless soil samples were both dehydrated normally.Stainless steel sleeve size design,easy to remove the sample after freezing and thawing,thereby reducing the sample disturbance and damage.The test uses the UK GDS resonance column RCA test system to measure the damping ratio and dynamic shear modulus of the target soil.Damping ratio and dynamic shear modulus are two important numerical values for analyzing the dynamic characteristics of subsoil under seismic wave,train load and vibration load.In this paper,the selected target soil is silt with a plasticity index Ip of 7.8.The confining pressures used in this experiment were 50kpa,100kpa and 150kpa respectively.The curing age was 1 day,7 days and 14 days respectively.The number of freeze-thaw cycles was 3 times,5 times,7 times and 10 times respectively.Through the existence of geomembrane bags,the number of freeze-thaw cycles of the target soil,the confining pressure and the different curing ages,the author studies the variation of the dynamic shear modulus and damping ratio of the target soil in the small strain range.From the analysis of test results,we can see that with the extension of curing age,the dynamic shear modulus increases;with the confining pressure increases,the dynamic shear modulus also increases;with the increasing number of freeze-thaw cycles,The shear modulus is decreasing.The soil samples with geomembrane bags have larger dynamic shear modulus than those without geomembrane bags.On the contrary,the damping ratio decreases with the increase of curing age,and the damping ratio decreases with the increase of confining pressure.As the number of freeze-thaw cycles increases,the damping ratio increases.Damping ratio is smaller than that of specimens without geomembrane bags.Test results can be drawn:During the freeze-thaw cycle,the geotextile bag hinder the capillary water rise into the sample,the water easy to out of hard,there are less bags geomembrane sample bag less water content,soil test Like to play a very good protective effect.