| With the Hanpoya Tunnel of Yunyang-Wanzhou Express Highway taken as engineering background, construction experience of tunnels at loosened fragmentized surrounding soft rock in domestic and overseas is first analyzed and summarized in this paper, and the construction technical measures are put forward for this tunnel. To proceed with the properties of loose fragmentized surrounding soft rock such as looseness of its structure, poor cohesion, becoming less crowded and giving birth to pressure and subsequent collapse after excavation, the following technical measures have to be taken including presupport, bench method with short excavation, early closure of support structure, strengthening the support structure and covering excavation face as necessary with shotcrete, so that the loosened fragmentized surrounding rock can be passed safely.Three Dimension Finite Element Method ( 3D FEM) is chosen to simulate dynamic mechanical properties of the presupport of closely-set small-diameter pilot steel pipes for the section of Hanpoya Tunnel with shallow depth in loosened fragmentized surrounding rock and initial support structures during excavation. According to the results of calculation, the laws are analyzed that groud surface settlement, arch crown settlement, horizontal convergence between arch feet, inner stress in shotcrete and axial force of bolts vary with each construction step, and some meaningful results have been attained to instruct construction, and finally the loosened fragmentized surrounding rock was safely passed through.In order to prove the effectiveness of construction techniques put forward for the loosened fragmentized surrounding rock in Hanpoya Tunnel and reasonableness of results by 3D FEM, some measuring items had been carried out such as ground surface settlement, arch crown settlement, cross-section convergence of tunnel, stress in shotcrete and touch pressures between initial and second reinforced concrete lining during...
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