Study And Treatment For Geological Disaster Of Tunnel With Unsymmetrical Pressure

In the construction of mountain tunnels, the phenomenon of unsymmetrical pressureat the tunnel entrance exists usually. The problem of tunnel with shallow andunsymmetrical pressure takes much trouble to the entrance construction of the tunnel.Entering into the tunnel safely depends on the treatments of the unsymmetrical loadedsection. If the treatment of the entrance is carried well, it well lead to the construction besafe and successfully, which ensures the construction safety, quality and progress.Otherwise, geological disaster will occur such as landslide and collapse.Taking Qinglong Tunnel of Yiba Highway as an engineering example and aiming atthe shallow buried tunnel with unsymmetrical pressure, a system study has been carried, itinclude the theoretical analysis, numerical simulation, monitoring and measurement forlandslide and collapse.The main contents are as follows:(1) Based on the previous study detailedly, the factors that affect the stability of thetunnel portal section have been summarized. The affection for the tunnel has beenanalysed for the different construction.(2) Using ABAQUS finite element software the construction inside tunnel and theconstruction of retaining wall is simulated. The affection of them for the stability of theslope has been analysed. At the same time the results have been confirmed through the sitemonitoring and measurement.(3) The tunnel that appears “half good half poor” geological condition and thedifferent methods of the tunnel excavation has been simulated by ABAQUS finite elementsoftware. The distributions of the displacements and stresses of the tunnel surroundingrock have been obtained. Combining with the actual situation of the schemen, the stagedivision method of excavation can be used to improve the stability of the tunnel withunsymmetrical pressure.(4) Based on the related literatures, the formulae for calculating the size of a tunnelexcavation section are proposed, which have been well applied to the tunnel construction and confirmed in the site. The results of the study can be used as the reference for thesimilar shallow tunnels with unsymmetrical pressure.