Study On The Pre-support Technology In Tunnel Excavation

The pre-support technologies are applied more and more abroad in order to conquer the bad influences appearing when the tunnels are excavated in bad geologic segments. The stratum forward the excavated face is supported or reinforced before it's excavated, then it can be safer and the damage can reduce during excavation. The techniques of pre-support are been studied in this thesis, and some important conclusion is made.Firstly, the mechanics performance of the surrounding rock was analyzed during the tunnel was excavated, especially, in the cracked terrane and the hydrostratum;the criterion of the surrounding rock's stabilization was summarized.Secondly, different grout schemes are contrasted and analyzed;the stabilization and distortion of the surrounding rock was analyzed through the FLAC^3D method .and the techniques of detecting grout effect are be studied; The selecting of grout fluids is discussed; The selecting rationally of grout parameter is discussed, among them the maximal grout press due to the cleavage produced by the water press is discussed .And then, the interaction of the anchor and the surrouding rock was discussed; pre-anchor pole's support mechanism is studied;The pressure on the anchor pole in different stratums is studied, The support parameter of pre-anchor pole are presented. The construction of the advanced anchor was discussed.Finally, summarizing the problem faced by the construct of the TBM in the tunnel excavation;and discuss the technics of the forepoling(pre-grout , advanced anchor) construction.