Research On Dynamic Response And Physical Character Parameter Inversion Of Isolation Cushion Constructed By Geocell Reinforced Rubber-sand Mixture

In recent years, the productions and lives of people suffered great damages because of earthquakes occurred frequently, especially in village-town areas, many low and multi-storey houses have collapsed seriously during the relatively large earthquakes, which bringing about a large number of casualties and destructions of property. Moreover,structural seismic design is use the elastic and plastic deformation of structure itself to consume earthquake energy, and this method can,but it doesn’t fundamentally,reduce the earthquake action of structures, and the randomness of earthquakes is also very strong. While the seismic isolation design method of the structure can, fundamentally and greatly,reduce earthquake action of houses, but the existing scheme of seismic isolation technologys can not be extensive applied very well in the village and small town buildings, which often because of its expensive price,complex working procedures, construction inconvenience, and so on.Rubber-sand mixtures have good characteristics, such as low cost,lightweight, environmental protection, energy consumption,etc, are a kind of new composite granular materials, and it have a broad application space in civil engineering. With rubber-sand mixtures adding in geocell,which can gets a kind of inexpensive cushion that can be used for the vibration isolation layer of the low rise village and small town buildings,its full name is isolation cushion constructed by geocell reinforced rubber-sand mixture. Therefore, the tests of shaking table which excited by different ways are conducted on the seismic isolation cushion which at different paving styles and different vertical stress, and the comparative analysis of its dynamic response are researched, at the same time,the inversion of the physical character parameters of it are studied under dynamic conditions. In addition, physical characteristics, laterally confined compression, direct shear and three axis CD shear tests have conducted respectively on the rubber-sand mixtures which will fill in the inner of it.The main research contents and works are as follows:1. The research status are summarized preliminarily by reading some domestic and foreign literature on the application of the waste tire and its particles in civil engineering.2. Physical properties tests and laterally confined compression tests are conducted on dry samples with seven different rubber mass fraction,and in order to study on the compression properties of samples, twelve grade vertical loads are considered. The variation of physical and mechanical parameters, such as cumulative settlement, springback,vertical elastic and plastic strain, density, void ratio, compression coefficient and compression modulus, of samples are analysised.3. Direct shear tests on rubber-sand mixtures which have the same rubber mass fraction at three different initial states, including drycompact, dry-loose and moist-loose, are conducted, and in order to study on the direct shear characteristics of samples, four different vertical stress are also considered, at the same time, eleven different rubber mass ratio are considered when samples are in the dry-compact or dry-loose conditions, seven different rubber mass ratio are considered when samples are in the water moist-loose conditions. The shear stress-shear strain curves which come from tests of samples under different initial states has been fitted by the hyperbolic curve. The comparative analysis of the variation of the shear strength characteristics, such as shear stressshear strain curves, internal friction angle, cohesion, shear strength envelope, vertical displacement-shear displacement curves, of samples under different initial states are discussed. Meanwhile, the change rule of the fitted parameters, for example,shear modulus and reference strain,under different initial state of samples are analyzed.4. A series of three axis CD shear tests on dry samples with seven different rubber mass ratio under six confining pressures are conducted.Shear strength test values, the deviatoric stress-axial strain curves and volumetric strain-axial strain curves of samples are obtained and analysised. Based on the Duncan-Chang hyperbolic curve mode,deviatoric stress- axial strain curve of samples are fitted. The change rule of the initial tangent modulus, ultimate deviator stress, and damage ratio of samples are analysised. In addition, the comparative analysis of themechanical of samples obtained from axis CD shear tests respectively with some existing similar tests and direct shear tests from this paper are dicussed.5. Shaking table tests on the isolation cushion constructed by geocell reinforced rubber-sand mixture at different paving styles under different vertical pressure are conducted by used self designed shaking table, and the table is actuated by two different kind excitation, one is the instantaneous impact,the other is draw-release. Meanwhile, Shaking table tests on two kinds seismic isolation layer, which are the unreinforced rubber-sand mixture and geotextile bag reinforced rubber-sand mixture,are also conducted respectively. The rubber mass ratio of the dry rubber-sand mixtures in different paving styles seismic isolation layer are30%. The dynamic response of these vibration isolation cushion are analyzed, and the test results show that all the vibration isolation cushion can separate and filter the high frequency fluctuation of the vibration.6. Will compressive zone of the isolation cushion constructed by geocell reinforced rubber-sand mixture which paved by full or square simplified as viscoelastic model. Combined with displacement response of it under the action of dynamic load, the physical character parameters of dynamic characteristics of it are inversed by the inverse equation which deduced from the assuming model. The relationships of the period of vibration, horizontal dynamic shear stiffness, horizontal dynamic shear modulus, damping ratio with dynamic shear strain respectively of it are analyzed. In addition, the variation of physical character parameters obtained from inversion and the variation of dynamic characteristics obtained from cyclic simple shear tests are studied by comparative analysis.7. Finally, the results of each chapter in this essay are summarized,and some prospects are proposed.