摘要
人工地层冻结法施工中,地下水渗流会影响冻结过程中的热传导机制,导致温度场重分布、冻结壁发育异常及地表冻胀变形加剧等难题,存在工程风险。本文基于COMSOL Multiphysics软件建立数值分析模型,研究人工冻结法施工过程中不同渗流速度下土体温度与变形场发展规律,分析渗流作用对冻结壁发育成型及地表冻胀变形的影响,并根据地下水渗流特点,提出不同渗流速度下对应的冻结管优化布置调控方法。研究表明:地下水渗流作用会引发上下游区域温度梯度差异扩大,上游侧冻结壁发育受阻,冻结壁呈现非对称形态,导致冻结时间延长,施工完成后地表最大冻胀变形量超过预警值。根据地下水渗流方向和大小,对冻结管采用非均匀排布方法,通过动态调控冻结管空间密度,显著提升冷量利用效率,抑制地层冷温迁移,使冻结壁均匀发展,有效缩短冻结周期。优化后的结果表明,高渗流速度下(v=0.8 m·d^(-1))冻结施工完成后,地表最大冻胀量亦可控制在规范预警值之下,有效防止施工区周边建筑物发生冻胀损伤。
Artificial ground freezing(AGF)is a geotechnical technique widely used in underground construction.It provides temporary stabilization of the soil by freezing the pore water to form a“frozen wall”with suffi⁃cient strength and impermeability.This technique is crucial in applications such as foundation pit excavation,shaft sinking,and tunnel excavation,as it can effectively prevent groundwater infiltration,support surrounding strata,and reduce the risk of soil collapse.However,groundwater seepage significantly disrupts the heat con⁃duction mechanism during freezing,leading to a series of critical engineering issues such as redistribution of the temperature field,irregular development of the frozen wall,and increased risk of frost heave deformation at the surface.These issues may eventually cause construction delays,compromise structural stability,and even pose potential threats to surrounding buildings and infrastructure,thereby posing major engineering risks.The influ⁃ence of groundwater seepage on AGF mainly manifests in three aspects:(1)uneven temperature distribution;(2)irregular development of the frozen wall;and(3)increased risk of frost heave deformation at the surface.First,the convective heat transfer caused by groundwater flow disrupts the temperature gradient distribution that originally relies on heat conduction,resulting in an increased temperature difference between the upstream and downstream sides of the frozen wall.Second,as the freezing front on the upstream side develops slowly due to the obstruction caused by seepage,the frozen wall may exhibit asymmetric growth,thereby weakening its over⁃all structural strength.Third,frost heave deformation is closely related to water migration.Groundwater seep⁃age transports unfrozen water into the freezing zone,where it crystallizes and causes heave deformation within the soil matrix.If not properly controlled,surface uplift may exceed the warning thresholds specified in engi⁃neering codes,potentially damaging surrounding buildings.To thoroughly investigate and address the above is⁃sues,this study established a numerical model on the COMSOL Multiphysics platform,which enabled the cou⁃pled simulation of multiple physical processes of heat conduction,fluid flow,and mechanical deformation.The core objective of this model was to investigate the spatiotemporal evolution patterns of soil temperature and defor⁃mation fields during the AGF under different groundwater seepage velocities.By systematically analyzing the in⁃fluence of groundwater seepage on the formation and evolution of the frozen wall,as well as the mechanisms af⁃fecting frost heave deformation at the surface,this study revealed the complex regulatory effects of groundwater flow on the freezing process.The results showed that groundwater seepage significantly increased the tempera⁃ture gradient between the upstream and downstream regions of the frozen wall.The development of the frozen wall exhibited significant asymmetry because the freezing speed at the upstream front was strongly suppressed by seepage.This asymmetry not only reduced the overall structural performance of the frozen wall but also extend⁃ed the freezing duration.After construction was completed,the maximum frost heave deformation at the surface may exceed the warning thresholds specified in relevant engineering standards,necessitating measures to prevent damage to surrounding structures.To address this problem,this study proposed a non-uniform layout strategy for freezing pipes,dynamically adjusting the spatial density based on the direction and velocity of groundwater flow.This optimized layout significantly improved the efficiency of cold energy utilization,limited its migration within the soil,promoted the uniform development of the frozen wall,and shortened the freezing duration.Un⁃der high seepage velocity conditions(v=0.8 m·d^(-1)),the optimized model confirmed the effectiveness of this strategy.After construction,the maximum surface frost heave deformation was controlled below the warning threshold,preventing potential damage to surrounding buildings.By integrating numerical simulation with engi⁃neering optimization strategies,this study provides theoretical support and practical guidance for the design and implementation of AGF technology under groundwater seepage conditions.The findings highlight the impor⁃tance of incorporating groundwater dynamics into AGF system design and provide feasible solutions to enhance the safety and efficiency of underground engineering under complex hydrogeological conditions.
作者
周海祚
刘玲霞
时卓航
胡俊
李成虎
夏博洋
张京京
王善兴
姜学军
ZHOU Haizuo;LIU Lingxia;SHI Zhuohang;HU Jun;LI Chenghu;XIA Boyang;ZHANG Jingjing;WANG Shanxing;JIANG Xuejun(School of Civil Engineering,Tianjin University,Tianjin 300072,China;Fuzhou Metro Line 6 East Adjustment Section Co.,Ltd.,Fuzhou 350011,China;School of Civil Engineering and Architecture,Hainan University,Haikou 570228,China;China Railway 18th Bureau Group Co.Ltd.,Tianjin 300400,China;Tianjin China Railway Engineering Testing Co.,Ltd.,Tianjin 300042,China;Municipal Engineering Co.,Ltd.of China Railway 18th Bureau Group,Tianjin 300222,China)
出处
《冰川冻土》
2025年第4期1015-1023,共9页
Journal of Glaciology and Geocryology
基金
福州地铁科技资助计划项目(JS6D-XM-KY-2024-001)资助。
关键词
冻胀变形
渗流
冻结管布置
数值模型
frost heave deformation
seepage
arrangement of freezing pipes
numerical model
