Based on investigations carried out on two large blast furnaces at WISCO,the features and reasons of erosion of hearth and bottom lining are analyzed focusing on the effect of zinc existence on the formation of circular cracks in the hearth.

Calculation on circumferential crack and axial crack resistance of embedded pipe below dam;

5 m standard span prefabricated long T-beam appears a circumferential crack after form removal,through theoretical analyzing,the uneven settlement of pedestal and shrinkage of concrete are probably the main cause for crack.