Evaluating Construction Risks of Modified Shield Machine Applicable to Soft Soils Based on Fuzzy Comprehensive Evaluation Method

Figure 4

Unmodified and modified shield machines. (a) Unmodified shield. (b) Modified shield with enlarged diameter. (c) Cutterhead in upper-soft lower-hard ground. (d) Cutterhead in soft soil.

(a)

(b)

(c)

(d)