FORMATION MECHANISM AND INITIAL CONDITION OF SOIL CAVITY
土洞形成的机理及起始条件

The formation mechanism and factors affecting of soil cavity are analyzed. It is realized that super- hydrostatic pressure makes the soil block spalled and fissured,and hydrodynamic pressure makes soil fine grain migrated. Both actions induce the enlargement of soil cavity. The initial conditions of soil cavity formation,i. e.,the critical declined magnitude of water level crHD,critical water flowrate vcr and critical discharge Qcr are formulated.