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Abstract The mea surement s of g ro und st resses by using the hydraulic cracking method w ithin the deep boreholes w ere pro ceeded at the Qinling ex t ra-lo ng tunnel di st rict. Based on the practical measuring result s, and combined w ith the g eological ci rcumsta nces at the measuring point s, the paper makes the discussions o n the follow ing impor tant aspects: the inf luences of topog raphic-g eomo rpholog y o n the measuring resul ts, the co ncent ratio n o f st resses, the g round st resses at the deep po rtions, etc. The result s show tha t the gro und st resses at Qinling ex t ra-long tunnel district hav e been ex pressed in some speciali ties mainly by the g rav itatio nal st ress-field. Finally , combined wi th the engineering practices, the paper discusses the pro blems co ncerned w ith the axial selectio n of the tunnel, the rock burst during construction, etc.
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Received: 18 July 1996
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1996, Vol. 13 
