Evaluation of squeezing conditions to determining support & optimal support and installation distance

Inadequate information of qualification & squeezing degree of susceptible rock, results to delay, re-construction & imposing extra expense, in the most of the tunnel project.For prediction of squeezing in tunnel, various methods depend on rock features, tunnel geometry characteristic‟s & size of tunnel and shaped plastic radius around the tunnel were proposed, which of course in them, the most important factor, as distance to tunnel face and effect of un plasticized zone radius were ignored and in fact supports design was done based on the most critical condition.In this paper, based on analytical & experimental studies, a new method was introduced, to estimate squeezing in rock masses, that, by using this method, the optimize distance of the last row of installation, work maintenance and optimal size of dig step could be determined safely, so that in addition of prevention of displacement distribution in further distances, far from the face, the support system not yield in entrant pressure.

Keywords:

Squeezing , Tunnel , Plastic zone , Distance to face