Study On Mechanical Properties And Vibration Reduction Performance Of Rubber Mixed Clay

With the rapid development of the economy,the national car ownership is growing year by year,which has a certain impact on the safety of buried pipes under the city carriageway,and the long-term effect of vehicle load is easy to make the pipeline deformation,rupture,leakage and other phenomena,thus causing safety accidents and economic losses.With the continuous development of the transportation industry,the amount of waste tires produced is also growing year by year,but its effective utilization rate is less than 50%,and the rubber crushed from it has the characteristics of light weight,high damping,good permeability etc,which can be mixed with common clay and backfilled around the buried pipeline to play a protective role for the pipeline.In this paper,the compaction,California bearing ratio,compression,and dynamic properties of rubber-clay soil mixture are investigated,and then it is used as backfill material around buried pipelines,and the vibration damping performance of rubber soil mixture under vehicle load is explored by means of numerical simulation,and the specific work and results are as follows:In the first part,the effects of rubber volume dosing and particle size on clay compacting characteristics and bearing ratio characteristics were studied by compaction test and California bearing ratio test,and the rubber dosing was divided into four groups of 0%,5%,10%and 15%,and the rubber particle size was divided into three groups of1-5mm,0.25-0.5mm and 0.1-0.25mm.It is found that the maximum dry density of mixed soil decreases with the increase of rubber admixture,and the smaller the rubber particle size,the better its light weight effect.Meanwhile,the optimal moisture content of soil slightly increases after rubber admixture,and the larger the rubber particle size,the lower its optimal moisture content.The California bearing ratio of mixed soil increases and decreases with the increase of rubber admixture,and the California bearing ratio of the specimen at 5%rubber admixture is the largest;the smaller the rubber particle size,the smaller the California bearing ratio,and the California bearing ratio is greater than 4 when the soil rubber admixture is 5%,10%and 15%under 1-5mm rubber particle size,which meets the technical specification of highway road base construction and can be used in the actual road.In the second part,the lateral limit compression test was used to study the compression characteristics of mixed soil with different rubber admixtures（0%,5%,10%,15%）and particle sizes（1-5mm,0.25-0.5mm,0.1-0.25mm）.It was found that the compression deformation of mixed soil under each working condition increased with the increase of vertical pressure;the settlement value and rebound value of specimen increased significantly with the increase of rubber admixture,and the plastic strain of soil always dominated in the process of compression-rebound;the compression coefficient of mixed soil was positively correlated with the rubber admixture,and the compression modulus was negatively correlated with it,and 1-5mm rubber mixed clay had stronger compression deformation ability.In the third part,the effects of surrounding pressure,rubber admixture and particle size on the properties of dynamic shear modulus and damping ratio of mixed soil under dynamic load were discussed by resonant column test.The surrounding pressure was50 k Pa,150 k Pa and 300 k Pa,the rubber volume admixture was 0%,5%,10%and 15%,and the rubber particle size was 5-10mm,1-5mm,0.25-0.5mm and 0.1-0.25mm,respectively.By normalizing the dynamic shear modulus G and damping ratioλof rubber blended soil,the development models of G/G_max and λ/λ_min with strainγwere obtained,and the results showed that the dynamic shear modulus ratio of the blended soil was positively correlated with the surrounding pressure and rubber particle size,and negatively correlated with the rubber admixture,and its damping ratio was negatively correlated with the surrounding pressure and rubber particle size,and positively correlated with the rubber admixture,which showed that the dynamic shear modulus of the soil decreased and the damping ratio increased after the rubber was admixed into the clay.It can be seen that the dynamic shear modulus of the soil decreases and the damping ratio increases after the rubber is added to the clay.Based on the particle contact state theory and considering the difference of specific gravity between clay particles and rubber particles,the fine contact state mode of mixed soil is divided into two categories of I and II,and the characterization model of maximum dynamic shear modulus of rubber mixed clay is constructed based on the skeleton pore ratio.In the fourth part,the dynamic characteristics of buried pipes in rubber-clay soil mixture under vehicle load were studied by Midas GTS NX software.It is found that the dynamic response at both ends of the carriageway is the strongest under the vehicle load,and the protection of the buried pipe ends below it needs to be strengthened;after1-5mm rubber particles are mixed into the fill,the road settlement value is within the allowable range;the pressure of the soil layer above and below the pipe is significantly reduced,and the stress and strain at the top of the pipe are reduced,which shows that the rubber soil mixture has vibration and load reduction performance,and the effect is the best under 15%rubber mixing condition.