针对砂卵石地层黏聚力小、内摩擦角大、渗透系数大、流动性和稳定性差等特性所导致的土压平衡盾构掘进中易发生掌子面坍塌、喷涌等难题，研制富水砂卵石地层专用聚合型泡沫剂PSA，并在全断面富水砂卵石地层进行应用。应用结果表明： 聚合型泡沫剂PSA在全断面富水砂卵石地层的碴土改良效果与现场使用的进口泡沫剂相当，明显优于国产其他品牌的泡沫剂改良效果，满足全断面砂卵石地层盾构施工对碴土改良的要求。使用聚合型泡沫剂PSA每环可节约9.5%左右的材料用量，经济优势明显，具有广泛的推广应用价值。

The sandycobble stratum has many characteristics such as small cohesive force, large internal friction angle, large permeability coefficient and poor fluidity and stability, which would easily cause the collapse and gushing of the face when earth pressure balance shield tunneling in. Hence, a polymeric foam agent PSA is developed for the waterrich sandycobble stratum, and it is applied to shield tunneling. The applicable results show that the soil conditioning effect of the polymeric foam agent PSA in fullsection waterrich sandycobble stratum is just as good as that of imported ones and better than that of domestic foam agents, and can fully meets the soil conditioning requirements of the shield tunneling in fullsection sandycobble stratum. By adopting polymeric foam agent PSA, about 9.5% of the material consumption per ring can be saved, which shows obvious economic benefits and popularizing value.