Muck Improvement Technology for Connec-tion Passage of Shield Tunneling Metro Tun-nels in Coastal Areas
[Objective]In the process of the earth pressure balance shield machine advancing in the coastal area cohesive soil layer,phenomena such as mud cake formation,unsmooth muck discharge,and blockage of the soil chamber often occur.In order to meet the requirements of shield tunneling,it is nec-essary to study the muck improvement technology in the cohe-sive soil layer.[Method]Based on a silty clay shield tunne-ling project of the connection passage on Ningbo Metro Line 5,the optimal mass fraction and the best injection ratio of the foa-ming agent are determined through the muck improvement test.The test results are applied to the shield tunneling construction site of the connection passage to verify the reliability of the im-provement technology.The finite element method is used to analyze the influence of shield tunneling construction on the de-formation of the soil layer at the site before and after the muck improvement.[Result & Conclusion]The optimal mass frac-tion and the best injection ratio of the foaming agent are deter-mined to be 3%and 20%respectively through tests.The test results are applied to the muck improvement at the shield tun-neling construction site of the connection passage.It is found that both the torque and thrust of the shield cutter head decrease significantly after the improvement of the soil layer at the site,and no mud cake is formed at the cutter head.The on-site con-struction is in a good state.The finite element method analysis shows that despite the increasing after the muck improvement,the ground settlement is relatively small.
metro tunnelcostal areaconnection passageshield tunneling methodmuck improvement technology