南昌复合地层盾构渣土改良技术

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。

Ground Conditioning Technology for Shield Tunneling in Composite Strata in Nangchang

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∶〖KG-*2/3〗1) and foam solution (with the foam concentration being 3%) may be used for grounding conditioning, and the consumption of bentonite shall be increased. 