The system comprises three major components a sand bed, a pair of concrete slabs, an arrey of springs and shock absorbers. A sand bed seismic absorption system is used to minimize and absorb the seismic waves during an earthquake. The system compromises of a bed of damp sand between two polymer membranes. The membrane consists of polyane, a ? exible and durable material used mainly in trash bags and onsite construction. The polymer membrane also keeps the sand damp and maintains the moisture within. The reason for use damp sand is because the water forms “bridges that connect the sand particles”.
The effect acts like rubberband between the grains. It is very important to maintain the moisture as too much water in the sand can form quick sand. Upon this sand bed is a concrete slab with many coil springs and shock absorbers and then a second concrete slab. The structure to be protected is placed on the second concrete slab. In the event of an earthquake, the sand bed acts to slow the propagation of seismic waves, and spreading them evenly throughout the area of the sand bed. As the seismic waves propagate through the sand, it has slowed enough for the coil springs to absorb the rest.
The concrete slabs should be of a thickness and strength to bear the weight of the structure to be supported. For comparison a seismic wave that propagates through granite at a speed of a 4km/sec will be slowed to a speed of 300 m/sec in sand. The springs must be of suf? cient size, strength and number to support the weight of the upper concrete slab as well as any structure to be supported. In a preferred embodiment the springs are compression coil spring made from high strength steel such as maraging steel. Maraging steel particularly suitable for springs of the invention comprises 18% nickel and 1-2% beryllium.
In a preferred embodiment the maraging steel additionally comprises 0. 5% bismuth to adapt the the invention it is desirable to determine the strength and ? exibility of individual springs. A spring is foreseen and conceived to support certain weight to be able to work. The conception studied for its work as to absorb shocks, twisting, compression and extension to keep for the object endowed with this system a horizontal stability. The dimension of springs suitable for the invention were studied.
The necessary values may be calculated using known formulas to calculate springs ? exibility ‘f’ and maximum tolerable oad Tmax f=8n(D)3/G(d)4 Tmax=8DPk/pie(d)3 An earthquake proof structure is supported on a foundation by a seismic shock absorption system adapted to isolate foundation. The shock absorption system coprises a plurality of elastomeric pads supporting the structure on the foundation to isolate the structure from horizontal and vertical movements impurted surrounding the foundation are subjected to seismic activity. the pads are between the structure, such as a building and the foundation. The shock absorption system is adapted for use on level ground as well as for side-hill application.