液氮和盐水联合冻结在盾构开仓换刀中的应用

Application of Combined Freezing of Liquid Nitrogen with Saline Water in Shield Opening and Tool Replacement

盾构法被越来越多地应用于隧道工程。盾构掘进过程中,由于地层对刀具的破坏,常需要开仓更换刀具。当常规盾构开仓方法有较大的局限性时,可以采用人工冻结法加固刀盘四周岩土层实现常压开仓换刀。针对超大埋深富水复合地层的盾构开仓换刀,提出了地面液氮垂直冻结+盾构切口环环向盐水冻结的加固方法。以珠江三角洲水资源配置工程土建施工B2标为例,分析了液氮和盐水联合冻结的总体思路、冻结壁计算、冻结壁设计、冻结孔施工、冻结效果和液氮用量等内容。研究结果表明:①该工程的液氮冻结孔的排间距、孔间距、孔深度和孔数量等设计合理;②该工程的盾构切口环环向盐水冻结管路的布置方案合理:③冻结孔的成孔效率与成孔偏差呈负相关关系;④积极冻结期的液氮消耗速度是维护冻结期的2倍。液氮和盐水联合冻结法成功应用于盾构常压开仓换刀,对于今后类似工程的设计和施工具有重要的指导意义。

Shield tunneling has been increasingly applied in tunnel engineering.During shield tunneling,it is often necessary to open the warehouse and replace the cutting tools due to the damage of the stratum to the cutting tools.When conventional shield tunneling methods have significant limitations,the artificial freezing method can strengthen the surrounding rock and soil layer of the cutter head to achieve opening and tool replacement under constant pressure.For the opening and tool replacement of the shield machine in the deep and water-rich composite stratum,the reinforcement method of vertical freezing of ground liquid nitrogen combined with circumferential brine freezing of the shield machine is proposed.Taking the B2 Bid of civil construction of the Pearl River Delta water resources allocation project as an example,this paper analyzes the general idea of joint freezing of liquid nitrogen and saline water,calculation and design of freezing wall,construction of freezing hole,freezing effect,and liquid nitrogen consumption.The following conclusions have been drawn that the design scheme of the row spacing,hole spacing,hole depth,and hole number of liquid nitrogen freezing holes are reasonable;The layout scheme of the shield tunnel incision circumferential saline freezing pipeline is reasonable;The drilling efficiency of frozen holes is negatively correlated with drlling deviation;During the active freezing period,the liquid nitrogen consumption rate is twice that of the maintenance freezing period.The combined freezing method of liquid nitrogen with saline water had been successful applied to the opening and tool replacement of shield tunneling under normal pressure,which has important guiding significance for the design and construction of similar projects in future.