Soft rock type

Mud content

Uniaxial compressive strength σ _c /MPa

Plastic deformation characteristics

Expansive soft rock (low strength soft rock)

>25%

<25

The structure is loose and weak, and the degree of cementation is poor. Under the action of engineering force, it slips along the fragrant silicate clay mineral, and it expands significantly with water.

High stress soft rock

≤25%

≥25

A little swelling in contact with water, slipping along the cage-like clay mineral under high stress conditions

Jointed soft rock

Less

Low to medium

Plastic deformation such as slip and expansion along joint surfaces such as joints

Compound soft rock

Contain

Low to high

Composite mechanism with some combination of the above