Abstract: The mechanical behaviour of intersection of horizontal adit and main tunnel in Wanxian to Liangping expressway in Southwest China is studied by using 3D finite element numerical simulation method and in-situ test. Due to adit construction, the research demonstrates the disadvantageous distribution of deformation and internal forces in intersection of adit and main tunnel, particularly in its side-wall connected to the adit. Comparing with the case of no adit, because of arch tunnel set being broken; the intersection structure is subjected to combination of complicated stresses including transverse stress, but not the axial stress. Therefore, it is necessary to take some reasonable reinforcement measures to guarantee safety of the intersection of adit and main tunnel. Furthermore, the intersection angle is more small, the stress concentration of intersection is more high. For example, while intersection angle is 60 degree, the maximum coefficient of stress concentration is up to 1.95; but while intersection angle is 90 degree, the maximum coefficient of stress concentration is about 1.5. The results are helpful for designing and construction of intersection of main tunnel and adit in major highway tunnel.

Key words: major tunnel, adit construction, intersection angle, arch tunnel set, stress concentration