Abstract:
The patterns of zonal disintegration and stability structures of surrounding rock of the equivalent excavation rectangular, straight wall semi-circle arch and circular sections under isotropic isostatic conditions are studied through the theoretical analysis, field measurement and simulation analysis. The conclusions are drawn as follows: the patterns of zonal disintegration of three sections are different. The zonal disintegration of rectangular section exhibits "
"distribution; and the straight wall semicircle arch and circular section show "
" and "petal" shaped distributions. The displacement characteristics of three sections are similar; the shallow part of the displacement isoline has an upright "egg shell" shape and the deep part has a "bowl" shape. The abutment pressure decreases at the main fracture surface, concentrates at the head of the main fracture surface in the outermost layer, and increases at the complete rock layer between fracture surfaces, showing a zoning concentration. The abutment pressure propagates outward with the characteristics of "wave trough-wave crest-wave trough" that gradually increases. The chord length of an ideal square fracture surface has a relationship of a_n\text + 1 = \sqrt \text2 a_n(
n=1, 2, 3, 4). After the zonal disintegration of the shallow surrounding rock is formed, it is equivalent to the pseudo-excavation of deep surrounding rock. Three sections have the bearing structures of multi-layer "
" shaped surrounding rock. The principle of roadway stability is to promote the interdependence and co-bearing of multi-layer bearing structures. The specific measures include encrypted, thickened, lengthened bolt (cable)supporting structures. The relationship between shallow and deep multi-layer bearing structures is established. The stable anchor solid is formed in the shallow part to promote the stability of the surrounding rock in the deep part. The precise grouting should be employed to repair the main fracture surface of the surrounding rock and to limit the slip of the main fracture surface.
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