南昌复合地层盾构渣土改良技术

Ground Conditioning Technology for Shield Tunneling in Composite Strata in Nangchang

为解决在南昌富水条件下砂层与泥质粉砂岩复合地层中喷涌、结"泥饼"、渣土"流塑性差、含水量高、渗透系数大"等施工难点,以南昌地铁1号线中子(中山西路站—子固路站)区间、八八(八一广场站—八一馆站)区间盾构施工为背景,通过数据统计及案例分析,得出液态高分子聚合物可作为抑制喷涌常态措施,泥质粉砂岩及富水砾砂层地质条件下,选取泡沫剂作为渣土改良添加剂,在砂砾石与泥质粉砂岩的复合地层,可考虑添加一定量的膨润土或高分子聚合物,解决砂砾石地层中渣土流动性差、防喷涌及粉质泥沙岩中结"泥饼"等问题。砂砾层体积与渣土总体积之比小于等于1/3时,渣土改良方式采用泡沫剂与分散剂溶液;大于1/3而小于2/3时,改良方式采用膨润土与泡沫剂溶液;大于等于2/3时,改良方式采用水土比8∶1膨润土与浓度为3%泡沫剂溶液,但膨润土用量应增加。

During shield tunneling in the composite strata consisting water-rich sand and silty sandstone in Nanchang, difficulties such as water/muck gushing, muck blocking, poor muck plasticity, water-rich muck and highly-permeable muck may be faced. In the paper, the ground conditioning applied in the construction of Zhong-Zi running tunnel and Ba-Ba running tunnel on Line 1 of Nanchang Metro is studied. Conclusions drawn are as follows： 1 ） Liquid high-molecular polymer may be taken as the common measure to control the water/muck gushing;Foam may be taken as the ground conditioning agent in silty sandstone geology and water-rich gravel sand strata; 2 ） In the composite ground consisting of sand gravel and silty sandstone, some bentonite or high-molecular polymer may be added so as to solve such problems as low fluidity of mucks, water/muck gushing and muck blocking;3） Where the volume of the sand gravel is not more than 1/3 of the total volume of the mucks, foam and dispersing solution may be used for grounding conditioning;Where the volume of the sand gravel ranges from 1/3 to 2/3 of the total volume of the mucks, bentonite and foam solution may be used for grounding conditioning;Where the volume of the sand gravel is equal to or larger than 2/3 of the total volume of the mucks, bentonite solution （ with the water-bentonite ratio being 8∶1 ） and foam solution （ with the foam concentration being 3%） may be used for grounding conditioning, and the consumption of bentonite shall be increased.