Study On Structure Behavior Of Highway Tunnel In High Geo-Stress Field

The deep-buried tunnel with large sections is applied more and more in the mountainous areas, so the high geo-stress problems which have a remarkable influence on the terrain stability and the tunnel's support system in the underground projects are often found in the circumstances. That makes deep-buried tunnel's support system mechanical behaviors different from common traffic tunnels.This paper takes Cangling tunnel which was designed by New Austrian tunneling method (NATM) with the maximum buried depth 768.2m and the total length of 2×7500m, as the background. The rock mass that tunnel area cuts through is intact and with high strength. The in suit geo-stress is up to 22 MPa. The paper study with the methods , combining with model test and numerical simulation to analyze the practical mechanical behavior, which provides the basis data to monitor and maintain the tunnel's structure safety during the service period.Main contents and research findings of this paper are list below:1,According to the drilling data of in suit geo-stress to back analysize the initial geo-stress field and the rock parameters, the geo-stress distribution along the tunnel axis which can be considered as the most foundation material to the rock and structure stability.2,Indoor model test sets the geometry similarity ratio(1:35) and the gravity similarity ratio (1:1) as the basic similarity ratio, to control all the physical and mechanical parameters. Taking long-term safety-monitored sections of Cangling tunnel as tested subjects, indoor model tests simulate the tunnel's construction process strictly. And the geo-stress field is simulated by exert different boundary loads to the model, so that the practical mechanical behavior about main structures of expressway tunnel are studied.3,Finite elements method(FEM) is applied to simulate the plastic and elastic behavior of the terrain and support system's stress and displacement pattern of the tunnel portal. On the same time, load-structure model is used to evaluate the enlarge section's secondary lining safety.