In order to study the difference of tectonic stress field between shallow and deep engineering areas

the in-situ stress field characteristics and fault stability of shallow and deep rocks were analyzed and compared by regression analysis and fault friction slip criterion based on the measured in-situ stress data of 376 groups from shallow rocks and 619 groups from deep rocks after optimized processing. The results show that the stress field in deep rocks has a tendency to change from tectonic stress field to vertical stress field. The linear correlation between the principal stress and the depth in the deep rocks is higher than that in shallow rocks. With the increase of depth

the lateral pressure coefficients KH1

Kh1 of shallow rocks approaches 1.54

0.85

respectively

while KH2

Kh2 of deep rocks are approached to 1.15

0.85

respectively. The horizontal differential stresses (η1

η2) in shallow and deep rocks have the increasing trend with depth on the whole. The shallow and deep faults are mainly in stable state when the friction coefficient μ is 1.0

while the shallow thrust fault has large sliding possibility and the possibility of deep fault slip instability is smaller as μ is 0.6. When μ is weakened to 0.4 or as low as 0.2

the sliding possibility of shallow and deep faults increases significantly. In the slide stability criterion

μ may be selected as 0.6-1.0 or 0.4-0.6 for shallow or deep fracture and as about 0.6 or 0.4 for reverse or normal fault.