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兰州市城关区黄土塌陷易发性分区研究

Study on the Susceptibility Zoning of Loess Subsidence in Chengguan District, Lanzhou City

  • 摘要: 兰州市城关区地处陇西黄土高原西部边缘,地表广泛发育自重湿陷性黄土,受极端降水和管道渗漏影响,近年来地面塌陷频发,威胁城市安全。本研究依托兰州城市地质钻孔数据库建设项目,基于1 076个钻孔数据,系统分析城关区67.92 km2建成区湿陷性黄土分布特征,识别出黄土层厚度、湿陷等级、湿陷深度、湿陷类型及黄土原生性5个关键影响因子。采用层次分析法(AHP)结合GIS空间叠加技术,构建浸水塌陷易发性评价模型,划分高、中、低三级易发区。结果表明:高易发区(面积为12.86 km2,占比为15.37%)集中于南北两山前缘Ⅱ级以上高阶地,包括大砂坪、伏龙坪等9个片区,其黄土厚度大(>10 m)、湿陷等级高(Ⅲ–Ⅳ级);中易发区(40.87 km2,48.86%)分布于高易发区外围,湿陷等级以Ⅱ–Ⅲ级为主;低易发区(29.92 km2,35.77%)位于黄河河谷及Ⅰ级阶地,湿陷性较弱。研究揭示,城区塌陷主控机制为“隐蔽性渗水-渐进式崩解”,提出基于钻孔数据与GIS的精细化分区方法,突破传统小样本分析局限,首次实现米级精度的塌陷风险空间刻画。研究成果明确了城关区重点防控区域,为减灾规划与管网改造提供科学依据,并为黄土高原城市灾害防控提供技术范式。建议近期开展大比例尺地质调查与管网渗漏排查,中远期推进智慧管廊建设,从源头遏制塌陷灾害。

     

    Abstract: Chengguan District of Lanzhou City, located at the western margin of the Longxi Loess Plateau, is characterized by extensive surface deposits of self-weight collapsible loess. Frequent ground collapses triggered by extreme precipitation and urban pipeline leakage have posed significant threats to urban safety in recent years. Supported by the Lanzhou Urban Geological Borehole Database Construction Project, this study analyzed 1,076 boreholes to delineate the distribution of collapsible loess within the 67.92 km2 built-up area. Five key influencing factors were identified: loess thickness, collapsibility grade, collapsible depth, collapsibility type, and loess origin. An Analytic Hierarchy Process (AHP)-GIS spatial overlay model was developed to assess water-induced collapse susceptibility, classifying the study area into high-, moderate-, and low-susceptibility zones. Results indicate that high-susceptibility zones (12.86 km2, 15.37%) are concentrated in Class II or higher terraces along the northern and southern mountain fronts (e.g., Dashaping and Fulongping), featuring thick loess layers (>10 m) and high collapsibility grades (III–IV). Moderate-susceptibility zones (40.87 km2, 48.86%) surround high-risk areas with collapsibility grades II–III, while low-susceptibility zones (29.92 km2, 35.77%) occupy the Yellow River valley and Class I terraces with weaker collapsibility. The study reveals a "hidden seepage-progressive collapse" mechanism and proposes a refined zoning methodology integrating borehole data and GIS, overcoming limitations of small-sample analyses and achieving meter-level spatial characterization of collapse risks. These findings provide critical insights for disaster mitigation planning and pipeline network optimization in Chengguan District, offering a replicable framework for loess plateau cities. Immediate measures include large-scale geological surveys and pipeline leakage detection, while long-term strategies advocate smart utility tunnel systems to address collapse risks at their source.

     

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