GEOLOGICAL AND SEISMIC WAVE FIELD CHARACTERS OF COAL-FIELD COLLAPSE PILLAR

Collapse pillars, existing in late Paleozoic coal-bearing formation in Shanxi province and north China, is caused by the collapse of Ordovician limestone karst. To coal-mining, Collapse pillars destroy the continuity of coal seam, refine mechanizing settlement, and even lead to gas and water outburst, threaten workers and coal-mine safety. it is an important subject to exactly explore the scale and property of collapse pillar for coal-field geological and geophysics workers.

Seismic exploration is a main geophysical exploration method for study of the collapse pillar, and a prerequisite for seismic exploration is understanding the seismic wave field characteristics of collapse pillar, and seismic wave field forward modeling is an important method to understand the characteristics of seismic wave field.

First of all, it summarizes the geological background, genesis and space distributed features of collapse pillar in this paper; and disserts on structural features and composition of collapse in detail; constructs geologic model and seismic model of collapse pillar.

Secondly,with Gaussian beam method, this dissertation analysis the ray pathway of collapse pillar models,summarizes out reflection by collapse-pillar's top and delay-diffracted wave are the characteristic waves of collapse pillar,which can be received on surfaceGoutlines that delay diffracted wave 's substance is that when seismic wave traverses low-velocity body underground, ray path and travel time differ from the ones on normal condition,such difference could show the property of low-velocity body underground.

Lastly, in practical seismic time section by work-area example is showed.

Finally, using project examples discussed the identification problem of collapse pillar in the seismic time section.

In summary, the collapse pillar is a special geological body, it has obvious characteristics of the geological and seismic wave field, with the method of seismic exploration can detect it.