Experimental Study On Small Strain Dynamic Characteristics And Analysis Of Isolation Performance Of Rubber-sand Mixtures

In recent years,the inland earthquakes in China are mainly concentrated in the underdeveloped areas in the central and western regions.What’s more,the investigation found that due to the limited economic conditions and weak awareness of earthquake prevention and disaster reduction,the disaster situation in the villages and towns was more serious than that in the urban areas.It is very important to study the low-cost isolation method for low-rise masonry buildings in villages and towns.On the other hand,with the development of Chinese economy and automobile industry,cars have gradually entered thousands of households,which has greatly improved people’s lives,but also brought many problems,for example,a large number of waste tires was produced.Thus,it has great economic and environmental benefits to study how to reasonably and efficiently use waste tires.Based on these two points,this paper considers that the rubber-sand mixtures,which is composed of crushed waste tires and sand,is used for the base isolation of village buildings.Firstly,using the existing data of the research group,the numerical analysis of the isolation effect of rubber-sand mixtures was carried out to verify its isolation performance.Then,on the basis of the existing research,the dynamic characteristics of rubber-sand mixtures in the small strain section were studied by GDS resonant column device.In addition,the dynamic characteristics of rubber-sand mixtures in the small strain section were studied.Based on the optimization of diameter characteristics and rubber content and combined with cyclic single shear test,the dynamic parameters of rubber-sand mixtures in a large strain range were obtained,which was expected to lay a foundation for the subsequent analysis of rubber-sand mixtures isolation effect.The specific research contents are as follows:(1)Referring to the dynamic characteristic curve of rubber-sand mixtures obtained by the research group,on the one hand,based on the soil structure interaction theory,the isolation effect of rubber-sand mixtures cushion on different types of sites is studied,and finally the influence of cushion thickness,basic seismic acceleration,base stress and site type on the isolation effect of rubber sand cushion is analyzed;on the other hand,based on the insufficient vertical modulus of rubber sand cushion This paper studies the dynamic characteristics of mushroom shaped short pile rubber sand composite cushion by Marc finite element software,and analyzes the influence of crown deflection angle and pile web diameter.(2)The combined test of shear wave and compression wave was carried out by using the bending expansion element method,and a reasonable method was chosen to determine the propagation time of shear wave and compression wave.The elastic dynamic parameters,such as initial shear modulus,lateral limit modulus and Poisson’s ratio of rubber-sand mixtures were obtained.The influence of rubber content and confining pressure on the elastic dynamic parameters of rubber sand was analyzed,and on this basis,the coupling effect of two factors and the related mechanical mechanism were discussed.(3)Through the GDS resonant column device,the torsional resonant column tests of rubber sand with different rubber content under different confining pressures were carried out to explore the relationship between rubber content and confining pressure on the dynamic shear modulus dynamic shear strain relationship and damping ratio dynamic shear strain relationship of rubber sand at small strain stage.On the basis of qualitative analysis,the quantitative analysis was further carried out,and the rubber content and confining pressure were summarized by comparing with the existing literature.The influence law of dynamic shear modulus and damping ratio of rubber-sand mixtures was discussed.What’s more,the internal mechanism of test phenomenon and law was discussed.(4)The dynamic shear modulus and damping ratio of rubber-sand mixtures with different particle size ratios were obtained through the torsional resonance column test under different rubber content and confining pressure with GDS resonance column device.The internal mechanism of the influence of particle size ratio on the dynamic characteristics of rubber-sand mixtures was analyzed and discussed by comparing with the existing literature.(5)Through the GDS resonant column device,the influence of the density of the sample on the dynamic shear modulus and damping ratio of the rubber-sand mixtures was studied.The test results,influence rules and the internal mechanism were analysed and discussed.On this basis,the resonance column test was carried out on rubber-sand mixtures with different particle sizes with the same particle size ratio.The influence of particle size and dry or wet state of sample on the dynamic shear modulus and damping ratio of rubber-sand mixtures were analyzed.(6)Based on the analysis of rubber content and particle size characteristics of rubber-sand mixtures,combined with the existing research of the research groups,the rubber-sand mixtures with relatively better proportion and particle size characteristics was selected.Through resonance column test and cyclic single shear test,the dynamic shear modulus and damping ratio-dynamic shear strain curves of rubber-sand mixtures in small strain and large strain sections were obtained,and the dynamic characteristic curves were summarized by theoretical conversion.