Experimental Study On Cyclic Shear Test Of Dynamic Characteristics Of Rubber-Sand Mixture

In recent years,the frequent earthquake damaged the people's productions and life,especially in rural urban areas.Many low and multi-storey houses have collapsed seriously in the previous large earthquake,which causing heavy casualties.Therefore,to improve the seismic performance of rural housing is the priority of disaster prevention and mitigation work.But the existing seismic design of the structure is to use the elastic and plastic deformation of structure itself to consume part of the seismic energy,which cannot fundamentally reduce the seismic effect of housing.While the seismic isolation design method of the structure really reduce the earthquake action of housing,but cannot be extensive applied very well in the village and small town buildings which often because of its expensive price,construction inconvenience and process complexity and other reasons.Rubber-sand mixtures are a kind of new composite material,which have the characteristics of low cost,environmental protection and energy consumption,and can be widely used 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.Therefore,the cyclic shear tests which excited by different ways are conducted on the seismic isolation cushion which at different cycles times,different water content and different vertical loading times of dynamic shear modulus and damping ratio were researched.The main research contents and conclusions are as follows:1.The research status are summarized preliminarily by reading some domestic and foreign literature on the waste tire and its particle material used in civil engineering.2.Cyclic shear tests conducted on three different rubber mass fraction samples which considered four vertical consolidation pressure and five different strain amplitude.Then analyzed the dynamic shear modulus and damping ratio changes with the 60 horizontal shear,and obtained the Gd-N curves,D-N curves.The results show that 20 times is the critical point that rubber-sand mixture's dynamic shear modulus ratio and damping ratio change versus cycle times.3.The water contents of rubber particles and sand particles were tested to determine the maximum water content of the material.According to the tests of water content,five kinds of water content were selected,and cyclic shear tests were carried out for the samples with the same rubber mass fraction under different water contents.The tests considered the three kinds of vertical stress,five kinds of strain amplitude and effect of three kinds of rubber mass fraction on its dynamic characteristics,and the hysteresis curves,dynamic shear modulus and damping ratio curve along with the change of water content were obtained.Besides,the dynamic shear modulus was obtained by fitting with maximum dynamic shear modulus,and the variation law of the maximum dynamic shear modulus of the sample under different conditions was analyzed.The results show that,considering the effect of water content on the dynamic characteristics,30% ratio of rubber sand is more suitable for practical engineering.The dynamic shear modulus and maximum dynamic shear modulus of the rubber sand have a critical value of 11.6% with the change of water content,and the damping ratio is not an obvious influence factor due to the water content.4.Cyclic shear tests were carried out on the samples with the same mass fraction of rubber under 4 different previous vertical loading times.The influence of three different vertical stress,five kinds of strain amplitude and three kinds of rubber mass fraction on the dynamic characteristics of the test was considered,and the dynamic shear modulus and damping ratio with the change of vertical loading times were obtained.The results show that,the rubber sand mixture of dynamic shear modulus increases with the increase of the previous vertical load times,and the critical value is 500 times with the change of vertical loading times.The discrete character of sand damping ratio with the change of vertical loading times is improved by adding rubber particles and geocell.5.Finally,the results of each chapter in his essay are summarized and some prospects are proposed.