Guangxi Highway Tunnel Portal Support Technology Research

As a result of terrain limitation and technical standard demand in mountain areas, more and more highway tunnels will be constructed. Because the stratum of the highway tunnel adit section is quite thin, and in most cases it belongs to the severity or entire weathering zone, the surrounding rock is general fragment and difficult to be constructed. Facing with this situation, a urgent problem is how to hold the stress characteristic of surrounding rock of the adit section and select the reasonable supporting method.In this thesis, at first, the author gives a summarization to the conventional supporting characteristic and the application method of the highway tunnel adit section, and the experience to choose supporting parameters by using analogy method in Guangxi highway tunnel. Then the author takes the Huale third tunnel as a project example, to study its construct excavation and supporting of tunnel adit section, to establish a finite element model to analysis the excavation and support of the V level surrounding rock of the tunnel adit section, finally to obtain the main conclusions of this thesis, they are, take the tunnel adit section supporting design and construction seriously; as for those defective geological condition areas, at least two kinds of supporting methods should be adopted, form the union supporting in order to strengthen the supporting effects; pre-reinforcement in advance is one effective method to improve the stratum; supports should be in time, and cross-section should be latched-up; Strengthen the base can improve the ground supporting capacity and better control the crown deformation of adjacent rocks.This research results may provides the reference for supporting design and the construction in highway tunnel adit section.