富水砂层与黏性土地层等普通地层相比，其孔隙率大、渗透性强、含水量大，在此类地层中带压进舱作业的难点是地层气密性封堵难度大。在高压环境中，为了尽量减小气体的逃逸，以西安地铁3号线土压平衡盾构在全断面富水砂层中成功带压进舱为依据，通过采用盾体外部膨润土泥浆封堵、掌子面用高效能泥浆形成泥膜封堵、盾尾采用加大同步注浆量和盾尾油脂注入等方法，以及一系列气密性检测等措施，成功进行了带压进舱作业，并得出土压平衡盾构全断面富水砂层气密性封堵的方法及气密性合格的判定方法。

Compared to cohesive soil strata, waterrich sand strata have higher porosity, higher permeability and higher water content. When hyperbaric operation is needed during shield boring in waterrich sand strata, it is of great importance to keep the air tightness of the strata around the shield. An EPB shield for Line 3 of Xi’an Metro bores through fullface waterrich sand strata, and hyperbaric operation has to be conducted. The strata around the shield is sealed by bentonite slurry, which is injected through the holes on the shield; the tunnel face is sealed by filter membrane formed by highefficient slurry, the simultaneous grouting and grease injection at the tail shield is enhanced, so as to ensure the air tightness of the sand strata around the shield and in turn to facilitate the hyperbaric operation. Furthermore, a series of air tightness testing and evaluation means are used to verify the sealing effect. In the end, successful air tightness has been achieved and successful hyperbaric operation has been conducted.