郑州市下穿中州大道矩形顶管隧道工程具有断面超大、覆土浅、4条隧道平行布置、净间距小等特点，地表沉降控制难度大。为有效控制地表沉降，采取同步注浆及二次注浆、渣土改良及出渣量、顶管机防背土、6刀盘控制及盲区处理、顶管隧道止退等关键技术。实践表明，超大断面矩形顶管在覆土浅、净间距小、地层多次扰动等复杂情况下，选择合适的注浆参数、精细化地控制出渣量及6刀盘操控、实施有效地止退等技术控制地表沉降是切实有效的。

The tunnel crossing underneath Zhongzhou Avenue in Zhengzhou has such features as superlarge crosssection, shallow cover, 4 parallel tunnel tubes and small spacing between the tunnel tubes, therefore there is great difficulty in the settlement control. Countermeasures, including simultaneous grouting, secondary grouting, ground conditioning, muck discharge control, soil carrying prevention, control of 6 cutter heads, blind area treatment and backward movement prevention are taken to control the ground settlement. In the end, the settlement is well controlled. The practice shows that the countermeasures taken are feasible and effective.