富水地层地铁超长联络通道冻结位移场演化规律研究

Evolution law of freezing displacement field in ultra-long connected aisle in water-rich stratum

人工冻结法因其安全可靠、环境友好等优点,被广泛应用于地铁联络通道的地层加固中。然而,相较于传统的联络通道,采用冻结法加固超长联络通道存在冻结体量大,地表冻胀控制难度高等特点。现有的研究成果难以充分描述其冻结位移场的发展规律,为此,依托福州市地铁2号线上洋站~鼓山站区间超长联络通道,该联络通道采用分区冻结主体和泵站、错开起始冻结时间等措施对地表冻胀进行控制。采用现场实测数据分析、数值模拟以及灰色关联分析等研究方法对该超长联络通道的冻结温度场和位移场的演化规律进行研究。研究结果表明:在错开冻结起始时间的情况下,冻结温度场和位移场的分布仍然具有良好的对称性,同时确定了冻结壁的薄弱位置应在该超长联络通道推迟冻结一侧的洞深方向12~15 m范围内。在联络通道洞身上方存在一个“圆饼”状的冻胀集中区域,地层位移场的发展表现出以该区域为核心向外衰减的特点,该联络通道的隆起特征值为43.16 mm,影响特征范围为21.95 m。就地层温度、盐水温度以及通道埋深而言,隆起特征值对通道埋深最为敏感,而影响特征范围受盐水温度影响最为显著。因此,为控制地表冻胀,在隧道的设计阶段可科学适当地加深超长联络通道的埋深,或在维护冻结期内安全合理地控制盐水的最低温度。研究成果可为今后同类长距离水平冻结工程的冻胀控制提供参考。

The artificial ground freezing method is widely used for the reinforcement of subway communication passages due to its advantages in terms of safety,reliability and environmental friendliness.However,as compared to traditional communication channels,the freezing method has the characteristics of a large frozen volume and high difficulty in controlling ground frost heave.However,it is difficult to fully describe the development law of its freezing displacement field.Therefore,based on the engineering background of the superlong connecting passage between Yangzhan and Gushan Station on Fuzhou Metro Line 2,the connecting passage adopted measures such as zoning freezing main body and pumping station,staggering the initial freezing time and so on to control the ground frost heave.The evolution laws of a freezing temperature field and displacement field in this super-long connecting channel was studied using research methods such as field measurement data analysis,numerical simulation,and grey correlation analysis.The research results show that the distribution of both the freezing temperature field and displacement field remains symmetrical even when the freezing start time is staggered,and it is determined that the weak position of freezing wall should be within 12~15 m of the hole depth on the delayed freezing side of the super-long connecting passage.There is a“round cake”-shaped concentrated area of frost heaving above the tunnel body,and the development of stratum displacement field shows the characteristics of outward attenuation with this area as the core.The uplift characteristic value of the communication channel is 43.16 mm;The influence characteristic range is 21.95 m.In terms of formation temperature,brine temperature and channel buried depth,the uplift characteristic value is the most sensitive to the channel buried depth.The influence characteristic range is most significantly affected by brine temperature.Therefore,it is suggested that in order to control ground frost heave,the buried depth of the super-long communication channels can be deepened scientifically and appropriately during design stage of tunnels or lowest temperature of brine can be controlled safely and reasonably during the maintenance and freezing period.It can provide reference for controlling frost heave in similar long-distance horizontal freezing projects in the future.