Table 5 Classification of rock mass structure.

Block structure

Integral structure

The rock mass is complete with huge-block shape and undeveloped structural plane, and the spacing is greater than 1 m

Block structure

The rock mass is slightly complete with block shape and slightly developed structural plane, and the spacing is generally 1–0.5 cm

Fractured block structure

The rock mass is slightly complete with fractured block shape and moderately developed structural plane, and the spacing is generally 0.5–0.3 m

Layered structure

Extremely-thick layered structure

The rock mass is complete with extremely-thick layered shape and no developed layers, and the spacing is greater than 1 m

Thick layered structure

The rock mass is slightly complete with thick layered shape and slightly developed layers, and the spacing is generally 1–0.5 cm

Medium-thick layered structure

The rock mass is slightly complete with medium-thick layered shape and moderately developed layers, and the spacing is generally 0.5–0.3 cm

Interlayer structure

The rock mass is slightly complete or has poor integrity with inter-layered shape and slightly developed or developed layers, and the spacing is generally 0.3–0.1 m

Thin layered structure

The rock mass has poor integrity with thin-layered shape and developed layers, and the spacing is generally less than 0.1 m

Mosaic structure

The rock mass integrity is poor, the rock blocks are tightly embedded, and the structural plane is slightly developed to developed. The spacing is generally 0.3–0.1 m

Fragmented structure

The rock mass is broken, the structural plane is well developed, and the spacing is generally less than 0.1 m

Granular structure

The rock mass is broken. Rocks, cuttings, and mud are mixed together