Twenty-one field explosive enlargement tests were carried out on six different soil test sites. The embedded charge were 0.05-51 kg and their embedded depths were 1.20-12.5 cm. Five explosively formed cavities were employed for the soil mechanical test on the variation patterns of natural density

pore-solids ratio

saturation degree

compressibility

compression modulus

internal friction angle and cohesive strength. The test results show that the radii of soil mass affected by explosion are four to six times larger than radii of explosively formed cavities. Soil performance indices such as natural density

dry density

saturation degree

compression modulus

cohesive strength are decreased with the increasing of distance to the center of charge. The indices such as pore-solids ratio

compressibility

coefficient of permeability are increased with the increasing of distance to the center of charge. No low-density region where density is lower than undisturbed soil is found around the caves. The variation pattern of internal friction angle of soil by explosive shock is not clear