The Study On Seismic Isolation Performance Of Granulated Rubber-Sand Mixture

China is a highly seismic country where severe damage caused by earthquakes takes place. As statistics state, about 35% of the mainland earthquakes with magnitude above seven in the world had occurred in China, causing casualties reached up to 590,000 among the 1.2 million victims killed by earthquakes worldwide in the twentieth century. In addition, one third area of the country is located in high seismic intensity zone (with seismic intensity above VII). From year 1990 to 2007, seventy events with magnitudes 7.0-7.9, six events with magnitudes above 8.0 had leveled Chinese Mainland, causing devastating disasters covering twenty-eight provinces, left 590,000 civilians killed, 760,000 injured and millions homeless. At 14:28 on May 12th, 2008, an unprecedented earthquake with magnitude 8.0 leveled Wenchuan, Sichuan Province, resulting in 69,188 victims and direct economic loss up to 845 billion yuan. For these reasons, the prevention and mitigation of earthquake damage as to minimize the seismically induced losses should be one of our country's fundamental national policies.In traditional anti-seismic design the anti-seismic safety property of structure is ensured by way of raising the function of strength and strain of the structural members. With intensive development of scientific research and experiments all kinds of assumptions and methods of seismic reduction and seismic isolation have been proposed as the times require. One of base isolation technology, have gradually mature, growing at a wide range of engineering applications. However, most of the existing seismic isolation technologies are hugely expensive, at the economic and ideological concepts behind the vast rural areas, the use of these seismic isolation technology is simply impossible. In view of the widely existing low-raise building constructions in the broad countryside, this paper is to propose a new seismic isolation method which can have a wide range of raw materials and is less costly and more feasible.A certain thickness of granulated rubber-sand mixture cushion of a certain volume ratio is paved between the foundation and ground in this new method, When earthquake happens the granulated rubber-sand mixture cushion will have shearing strain, reducing the input of high frequency volume, thus consume the earthquake energy form substrate. It is showed in shaking table experiment that the granulated rubber-sand mixture has lower dynamic shear modulus and larger damping ratio. It not only consumes part of the seismic energy but also makes the deformation concentrate in the granulated rubber-sand mixture cushion. The upper part of the structure does the relative translational. That's why the granulated rubber-sand mixture cushion can reduce the seismic response.In this paper,the seismic isolation function of granulated rubber-sand mixture cushion under masonry structure foundation and some possible factors that may have efect on its seismic isolation function are tentatively discussed through shaking table experiments.It provides some foundation for granulated rubber-sand mixture cushion's application in civil engineering.