Stress Performance Evaluation of Shield Machine Cutter Head during Cutting Piles under Masonry Structures

Table 4

Building damage grade evaluation standard.

Risk level	Maximum slope	Differential settlement (mm/m)	Building distortion (rad/m)	Risk description
1	＜1/500	＜2	＜4 × 10^−3	Ignorable: shallow damage is unlikely
2	1/500∼1/200	2∼5	4 × 10^−3∼1 × 10^−2	Minor: may be damaged in shallow parts, but has no effect on the structure
3	1/200∼1/50	5∼20	10^−2∼4 × 10^−2	Moderate: shallow damage, possible structural damage, possible related rigid pipe damage
4	＞1/50	＞20	＞4 × 10^−2	Serious: building structure damage, rigid pipeline damage, possible other pipeline damage

Note. newly added evaluation annotations by Yang and Zhang [24].