학술논문
土压平衡盾构穿越高渗透砂层砂土改良技术 / Sand Improvement Technology for Soil Pressure Balance Shield Tunneling Through High Permeability Sand Layers
Document Type
Academic Journal
Author
Source
铁道建筑 / Railway Engineering. 63(12):21-25
Subject
Language
Chinese
ISSN
1003-1995
Abstract
依托西安地铁一号线三期韩非路站—沣河森林公园站区间盾构隧道下穿沣河工程,通过数值模拟分析了盾构隧道施工过程中孔隙水压力变化特征及影响范围,明确了喷涌发生的条件,继而进行砂土改良试验,对工程现场砂土参数进行优化.结果表明:不管是隧道纵断面还是横断面,由上而下孔隙水压力均逐渐增大,纵向影响范围约9 m,隧道横向孔隙水压力近似呈漏斗状分布,影响范围约26 m;施工过程中螺旋出土器排土口处水头高度2.06 m、渗流量26.2 cm3/s,两者均超过喷涌发生的临界值;采用钠基膨润土泥浆对砂土进行改良,膨润土泥浆与砂土的质量比为1∶7时,改良后砂土流动性能逐渐提高,黏聚力增大,内摩擦角减小,抗渗性能明显提升,能有效防止喷涌现象.综合考虑施工要求、经济性和现场应用效果,采用钠基膨润土作为砂土改良剂时,建议钠基膨润土与水的质量比取1∶9,且泥浆膨化时间在16～24 h,钠基膨润土泥浆与砂土的质量比取1∶7.
Based on the shield tunneling under the Fenghe River project in the Hanfei Road-Fenghe Forest Park section of Xi'an Subway Line 1 Phase 3,the characteristics and impact range of pore water pressure changes during shield tunnel construction were analyzed through numerical simulation.The conditions for the occurrence of the surge were clarified,and then sand improvement tests were conducted to optimize the sand parameters on the engineering site.The results show that whether it is the longitudinal or transverse pore water pressure of the tunnel gradually increases from top to bottom,with an influence range of about 9 m,and the transverse pore water pressure of the tunnel has an approximate funnel-shaped distribution,with an influence range of about 26 m.During the construction process,the water head height at the soil discharge outlet of the screw excavator is 2.06 m,and the seepage flow rate is 26.2 cm3/s,both of which exceed the critical value for surging.Using sodium-based bentonite slurry to improve sandy soil,when the mass ratio of bentonite slurry to sand is 1∶7,the flowability of the improved sand is improved,the cohesion is increased,the internal friction angle is reduced,and the impermeability is significantly improved,which can effectively prevent the phenomenon of surging.Taking into account construction requirements,economy,and on-site application effects,when using sodium-based bentonite as a sand improvement agent,it is recommended to have a mass ratio of 1∶9 between sodium-based bentonite and water,and a mud swelling time of 16～24 h.The mass ratio of sodium-based bentonite slurry to sand should be 1∶7.
Based on the shield tunneling under the Fenghe River project in the Hanfei Road-Fenghe Forest Park section of Xi'an Subway Line 1 Phase 3,the characteristics and impact range of pore water pressure changes during shield tunnel construction were analyzed through numerical simulation.The conditions for the occurrence of the surge were clarified,and then sand improvement tests were conducted to optimize the sand parameters on the engineering site.The results show that whether it is the longitudinal or transverse pore water pressure of the tunnel gradually increases from top to bottom,with an influence range of about 9 m,and the transverse pore water pressure of the tunnel has an approximate funnel-shaped distribution,with an influence range of about 26 m.During the construction process,the water head height at the soil discharge outlet of the screw excavator is 2.06 m,and the seepage flow rate is 26.2 cm3/s,both of which exceed the critical value for surging.Using sodium-based bentonite slurry to improve sandy soil,when the mass ratio of bentonite slurry to sand is 1∶7,the flowability of the improved sand is improved,the cohesion is increased,the internal friction angle is reduced,and the impermeability is significantly improved,which can effectively prevent the phenomenon of surging.Taking into account construction requirements,economy,and on-site application effects,when using sodium-based bentonite as a sand improvement agent,it is recommended to have a mass ratio of 1∶9 between sodium-based bentonite and water,and a mud swelling time of 16～24 h.The mass ratio of sodium-based bentonite slurry to sand should be 1∶7.