Simulation Study Of The Shallow Tunnel By Excavation With Advanced Support In Grouting

The broken shallow tunnels frenquently appear in the actural project, to solve theproblem of such works, the vertical grouting method have become imperative. The history ofthe development of tunnel shallow, the mechanical properties of fragmentized wall rock andthe vetical grouting theory are carried out a systematic exposition, the main influencingfactors of the settlement of tunnel vault are analyzed and summarized, on the basis, the effectsof parameters on the tunnel vault deposition and its machanical properties are studied bytheoretical analysis, numerical simulation and in-situ test and so on. Conclusions are asfollows.The properties of tunnel surrouding rock under the shallow-buried fragmented strata areelaborated, it is pointed out that the shear strength of the broken rock is mainly controlled bythe weak structural plane or weak interlayer;The principle of the tunnel pre-supporting is further studied, to ensure the stability of thetunnel surrouding rock, the pre-supporting force should always be greater than the originalinternal force which can keep the rock stable and equilibrium before construction;The reinforcement mechanism and action effect of the vertical grouting are analyzed, itis found that pre-supporting can improve the stress state of surrouding rock in the front ofworking face, and enhance the stability of surrouding rock;By comparing the iMPact of different parameters on the vertical displacement of thedome, it is found that vertical grouting plays an irreplaceable role in this research. The iMPactof grouting width, grouting depth, tunnel depth and other factors on the action effect ofpre-supporting is further explored.In the shallow broken rock tunnel(especially the ultra-shallow), with the increasing widthof the surface grouting, vault settlement would tend to a stable value, that is, the iMPact of thewidth became weaker.The iMPact of grouting depth on the vault settlement is same as the above, the vault settlement would tend to a stable value with its increased, finally, its value istaken from the economic considerations.Under the same grouting depth and width, the iMPactof own depth on the vault displacement is quite large in the ultra-shallow tunnel, it is almostlinear, therefore, what extent support effort to be needed in different depth is further studied.