Abstract: Near blasting beneath the just completed primary support line is a special condition; it relates to many problems such as the primary support failure and subsidence. A design and construction example of an engineering of the Qingdao Metro Line 2 close (250 mm) beneath the just completed primary support line 3 tunnel, is employed, controlling vibration and deformation with measures such as the self-feeding pipe shed, tunneling crown, assisted middle hole cut, applied tensile force for the existing tunnel load, and reasonable blasting vibration control indexes are proposed according to analogy. The variation law of deformation and internal force of existing tunnel in building construction is revealed by using the finite element analysis software MIDAS-GTS for numerical analysis of 3D model. The measures taken achieve the desired effect. Primary support structure of the line 3 has no abnormal, through theoretical calculation and experimental analysis. Research results have an important reference value to blasting under special condition in design and construction.

Key words: blasting excavation, underneath pass, blasting vibration, shock absorption, deformation control