Abstract：The construction of vertical drainage bodies causes compacting effect. The stress change in soft clay and the range of construction disturbance zone due to construction of vertical drainage bodies are analyzed using the column cavity expansion theorem in the light of a plane stress problem. The increment of pore water pressure and the stress change in soft clay are prominent. The plastic zone around a vertical drainage body is like a bottle. Within the depth of Z0，the radius of plastic zone depends on the initial stress and undrained shear strength of the soft clay，and increases with the depth. Below Z0，the radius of plastic zone is invariable，and its value depends on the initial stress，undrained shear strength，secant modulus of soft clay，the types of vertical drainage bodies and the guide tube，length of and distance between vertical drainage bodies，etc. The construction disturbance mainly occurs within the plastic zone with the heave of ground surface as a byproduct. In-situ soil test reveals that in comparison with the untreated soft clay ground，the shear strength of the soft clay in the ground treated with vertical drainage bodies decreases greatly in the Pearl River Delta and the settlement of treated soft clay ground increases. Theoretical analysis shows that the radius of construction disturbance zone in the soft clay ground is about 1.2 times of that of the plastic zone and 9 times of that of the guide tube of vertical drainage bodies.
