Influence On Surface Motion Due To Underground Group Cavities

A lot of investigations of earthquake damage show that local site conditions cangreatly affect the surface motion subjected to incident seismic waves. The effectsrepresent primarily magnification and reduction, and consequently influence thedistribution of earthquake damage. Local site conditions include the irregularity ofground shape and the inconsistency of medium such as alluvial valley, accidentedlandform, underground cavities, faultage, delamination in soil, etc. It is a significantquestion for discussion in Earthquake Engineering to estimate the amplificationquantificationally on sorts of specific field.In order to solve radically the problem of excess traffic jam, severe groundshortage, environment deterioration increasingly, it is an inevitable trend for moderncity development to exploit and utilize the underground space cosmically. Largegroup cavities on account of underground engineering construction can without failaffect the surface motion of neighborhood along the line of the cavities. Estimatingthe amplification quantificationally is greatly significant for earthquake securityevaluation of existent ground buildings and aseismatic defence of arranged projects.Furthermore, it can provide theoretical foundation for a great deal of work againstearthquake.Wave function expansion method is applied to the problem of impact on surfacemotion due to underground group cavities subjected to incident SH waves. Basing onthe symmetry characteristic of plane SH waves, a set of wave functions that satisfythe boundary conditions on the surface of half space is constructed by using imagetechnique. Finally, analytical solutions in closed form are presented for theunderground group cavities without linings and the lined underground group cavities.Numerical results indicate that displacement amplitudes on the earth's surface aremagnified obviously comparison with single cavity. They change more rapidly onspace than single cavity. Moreover, there are many factors such as the frequency andangle of incident SH waves, the depth of cavities and the shear moduli of linings thatinfluence the amplification of ground motion remarkably.