Application Research Of Rayleigh Wave In The Karst Exploration

The caves that widely exist in the karst area would cause many problems,such as the descent of the karst water,threaten the stability of the buildings on the ground and the subsidence of the caves.these hazard seriously threatens the quality and safety of the constructions, brings huge economic loss.in our country,there are many karst areas,such as GuangXi, GuiZhou,and YunNan province. In recent years, with the rapid development of economy, more and more engineering projects are built in the karst areas, In order to avoid losses from Karst, survey work before construction is very important.Rayleigh wave exploration is an efficient, rapid method of geophysical exploration, has been widely used in the field of engineering. But predecessors in the study of Rayleigh wave mostly based on layer media model which is a kind of idealized models, but karst cave is obviously not fit for this situation, this seriously limits the use of Rayleigh wave exploration. So study the Rayleigh wave used in the exploration of karst is necessary.In this paper the staggered-grid finite difference method are used to simulate Rayleigh waves, when the derivation in differential equations, using first-order elastic wave equation velocity-stress, and using a stress on space derivative instead of stress on the time derivative, derivation in time and space can be reached on any first-order difference scheme.and achieve any degree of difference scheme. In calculating frequency dispersion curve, the s transform in spectrum analysis technique are applied, greatly improving the precision of the dispersion curve. This article firstly research the wave field characteristic of Rayleigh wave in karst caves, The main consideration is the buried depth and size of karst cave, and designed two models which are same size, but buried deeply8meters and25meters, And then designed two models which are same buried depth, but width is5and10meters, Simulate the communication process of Rayleigh wave in the models, and analys the wave field records.The article also tried to locate the cave,used the spectrum analysis technology to increase the transverse resolution of surface wave exploration; the buried depth of karst cave is calculated from the frequency whose speed in horizontal is the same, and achieved the expected effect.