泥水盾构隧道施工引起的地面沉降分析及预测

通过对杭州庆春路过江隧道泥水盾构施工地面沉降监测数据的分析,总结了地面沉降的特点及影响因素,并结合实测数据给出了地面沉降的修正双曲线预测公式。分析表明：Peck公式适用于杭州软土地层中泥水盾构施工引起的地面沉降预测,其中地面沉降槽宽度参数K取值0.25～0.32,地层损失率V1取值0.04%～0.33%。地面沉降主要为盾构脱离0～5d或6d内的盾尾沉降以及扰动土体长期固结沉降,分别约占总沉降量的57.27%和41.08%。适当提高切口泥水及同步注浆压力使地面微隆,可以抵消部分地层损失,减少地面沉降。由地层损失引起的横断面地面沉降曲线较规则,基本呈现高斯曲线分布;而地面隆起变形较无规则,会使沉降曲线偏离高斯曲线分布。引入新参数C后的修正双曲线模型可用于泥水盾构软土地层中施工引起的地面沉降的预测。

Analysis and Prediction of Ground Settlements Due to Slurry Shield Tunneling in a River-crossing Tunnel

Through analysis of monitored ground settlements of Hangzhou Qing-chun Road cross-river tunnel,characteristics and influencing factors of ground settlements due to large-diameter slurry shield tunneling were summarized,and a modified hyperbolic model was proposed to predict the settlements.The results indicate that： 1.Peck equation is well used to predict ground settlements induced by slurry shield tunneling in Hangzhou district.The trough width parameter ranges from 0.25～0.32 while soil volume loss from 0.04%～0.33%.2.Settlements before the shield tail leaving the monitoring sections are small,while soil closure at the shield tail and long-term consolidation settlements make most of the total settlements,with percentages of 57.27% and 41.08% respectively.3.Increasing the pressure of slurry and synchronized grouting appropriately can counterbalance some ground loss,which can reduce the ground settlements.4.Transverse ground settlements induced by ground loss represent the shape of Gaussian curve while heave movements behave irregularly.Ground heave movements due to large pressure of slurry and synchronized grouting often lead to the transverse ground settlements＇ deviation from Gaussian curve.5.The modified hyperbolic model can be used to predict ground settlements due to slurry shielding in Hangzhou district with great accuracy.