By theoretical analysis and model experiment, the features of different kinds of covering layers and the problems existing in the construction of diversion and river closure are analyzed. Critical technical issues under deep  thickness covering layer condition such as the covering layer stability , the covering layer protection, the stability calculation of closure block, the artificial block stability and the preventive measures against embankment collapsing in alluvial riverbed are studied also. In addition, the practical computation formula for block stability is improved, and the empirical equations for the stability calculation of hexahedron steel reinforcement cage are deduced. It is the first to put forward that the stop- move stability of tetrahedron steel reinforcement cage is obviously better than that of hexahedron steel reinforcement cage, yet their start- move stability differs slightly.