关键词: 盾构隧道, 大直径盾构, 浅覆土, 穿越施工

Abstract: In order to reveal the effect of large diameter shield tunneling under railway culvert, the mechanical behavior of the operating railway bridge and culvert caused by shield crossing were predicted by numerical method, based on the practice of large diameter slurry balance shield for boring North Huancheng Road underground expressway tunnel in Hangzhou. Then the implementation effects such as shield construction parameters, controlling technology and bridge deformation were verified by field testing. The numerical analysis shows that the maximum settlement will reach 21.6mm at the bottom of the bridge and culvert, while the maximum tensile stress will reach 1.60MPa at the top and bottom of the middle wall of the bridge during the shield tunneling machine passing without the underneath soil strengthened. On the contrary, the maximum settlement and tensile stress will reduce to 9.3mm and 1.46MPa respectively when the underneath soil is reinforced. In the actual practice, the pressure at the cutting face is 15kPa larger than the static earth pressure. However, to ensure the operating bridge and culvert structure in the state of security during shield machine passing, the cutting face pressure increases to 25kPa larger than the static earth pressure, the total thrust and torque reduces by 10% approximately respectively considering the upper load decrease 13%. Furthermore, the tail grouting volume is parameterized between 150% and 200%. The field testing shows that the deformation of bridge and culvert will upheaval 3-4mm before the shield crossing, then translate into settlement about 4mm after the shield crossing. After 3 days since crossing completed, the differential settlement will decrease and tend to be stable gradually, and the final stability value is about 0.01%.

Key words: shield tunneling, large diameter shield tunneling, shallow covering, crossing construction