青岛地铁一期工程M3线试验段区间隧道K15+838.35～+660埋深8.15～13.1m，穿越VI级富水砂层，地面环境复杂，施工风险极高。在地面不具备降水及垂直加固的条件下，为达到控沉防塌的效果，保证地面建筑物及洞内施工安全，应用洞内环向水平旋喷桩超前支护技术，同时，采用一系列相配套的超前支护技术及加固措施，弥补了水平旋喷桩在砂层及碎石层中不能咬合的缺陷，确保了富水软岩地铁隧道的开挖支护安全。

K15+838.35～+660 section of the trial section of the first phase of line M3 of Qingdao Metro, with 8.15~13.1 m overburden, runs through Grade VI waterrich sand strata. Furthermore, the tunnel section has complex ground surface environment. Therefore, there is great risk in the construction of the tunnel section. However, dewatering and vertical reinforcement can not be executed from the ground surface. Therefore, horizontal jet grouting piles, as well as a series of advance reinforcement technologies are adopted, so as to guarantee the safety of the surface buildings and the tunneling labors. The disadvantage of horizontal jet grouting piles in sand strata and crushed stone strata, i.e., failure in interlocking, is solved, which guarantees the safety of tunneling in waterrich soft ground.