PDF(6629 KB)
PDF(6629 KB)
PDF(6629 KB)
裂隙岩层地下水位动态变化对降雨的响应
Response of Dynamic Changes in Groundwater Level in Fractured Rock Layers to Rainfall
地下水位是地下结构工程抗浮设计的关键参数,为明确裂隙岩层中地下水位动态变化对降雨的响应规律,运用实测手段,测试得到裂隙岩层中的水位变化数据和场地的降雨量数据,并对两者进行线性拟合分析。结果表明:地下水位变化与降雨密切相关,丰水期升高、枯水期降低,水位峰谷变化幅度范围为3.34~17.55 m;另外,地下水位增量随降雨量的增长斜率在0.006~0.025之间变化,反映出地下水位变化对降雨的响应快慢不一,主要受降雨强度、场地地势、地表水系和开挖施工等因素的影响。结合岩层的透水性可给出抗浮设计建议措施,裂隙岩渗透系数>20 m/d时,地下结构需增强被动抗浮措施或增加主动排水减压措施,渗透系数在10~20 m/d时需适当增加抗浮安全系数,渗透系数<10 m/d时则按正常工况设计。研究成果可以为地铁车站抗浮设计提供参考。
[Objectives] Large-scale urban underground space development has led to numerous anti-floating problems. Groundwater level is a key parameter in the anti-floating design of underground structures, but it is inherently dynamic and influenced by various factors. This study aims to investigate how groundwater level in fractured rock layers dynamically responds to rainfall. [Methods] Field monitoring was conducted along a subway line, with seven groundwater level monitoring points and two meteorological monitoring points installed. Real-time data of groundwater level in fractured rock layers and rainfall at the site were collected. Based on these data, the annual variation patterns of groundwater level and rainfall were analyzed. Groundwater level increments under moderate to heavy rainfall conditions (daily rainfall ≥10.0 mm) were extracted, and a linear fit was performed between rainfall and groundwater level increments. [Results] Groundwater level variations were closely related to rainfall, rising during wet periods and falling during dry periods, with peak-to-valley amplitudes ranging from 3.34 to 17.55 meters. Additionally, the slope of the linear fitting between groundwater level increment and rainfall ranged from 0.006 to 0.025, indicating varying response speeds of groundwater level changes to rainfall. These differences were mainly influenced by rainfall intensity, site topography, surface water systems, and excavation activities. Based on the permeability of the rock layers, recommendations for anti-floating design were proposed: when the permeability coefficient of fractured rock exceeds 20 m/d, underground structures should strengthen passive anti-floating measures or increase active drainage and pressure relief measures; when the permeability coefficient ranges from 10 to 20 m/d, the anti-floating safety factor should be appropriately increased; when the coefficient is below 10 m/d, standard design practices are sufficient. [Conclusions] The study identifies the main factors influencing groundwater level fluctuations, quantifies the response of groundwater level to rainfall, and proposes an anti-floating design method that accounts for the permeability coefficient of rock layers. This approach addresses the limitations of traditional anti-floating designs that assume a uniform design water level and provides practical guidance for the anti-floating design of subway stations.
裂隙岩层 / 地下水位 / 降雨量 / 线性拟合 / 渗透系数
fractured rock layers / groundwater level / rainfall / linear fitting / permeability coefficient
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Based on the soil and ecological survey and data of rainfall and groundwater level,this paper comparatively analyzed the response relationship between groundwater level and rainfall in different landform types(including mobile dunes,semi-fixed dunes,fixed dunes,woodland at dune site,high coverage meadow,plough of meadow and low coverage meadow) in the dune-meadow alternate region in Horqin,Inner Mongolia,China,the impact of an identified rainfall on the groundwater levels in different landform types,and impact of different rainfall to the groundwater levels in an identified landform type. The results show as follows:(1) the rainfall events less than 13 mm had no impact on the groundwater level in the mobile and semi-fixed dunes,and the rainfall events less than 4 mm had no effect on the groundwater level in the fixed dune and woodland at dune site;in dune area,the underground water level increased with the increase of the vegetation coverage,and the lag time of the rise of underground water level declined with the increase of the vegetation coverage;(2) after a larger rainfall event,the groundwater level of mobile and semi-fixed dunes had a clear downward trend;however,if the rainfall intensity reached 40 mm·h-1 in mobile dunes or 22 mm·h-1 in semi-fixed dunes,the groundwater level might occur mutation;(3) if the previous rainfall was effective rain,and the two rainfalls were within a short interval, the previous rainfall would influence the dry sand bed thickness and soil moisture,then promote the recharge of groundwater with rain,and this kind of promotion was more obvious in dune than in meadow;(4) in meadow area,rainfall intensity greatly influenced the groundwater level which was obviously affected by the seasonal and surface vegetation coverage,and the fluctuation of groundwater level was more significant after rain; (5) because of the shallow depth of the groundwater level in meadow area,capillary water was close to or even extended to the ground;in some small rainfall events,the groundwater level would rise higher than that in some greater rainfall events;(6) plough had a significant negative effect on the recharge and storage of groundwater in the meadow of arid area. Plough and over grazing had an obvious negative effect on the conservation of groundwater after rain in the meadow of arid area,but this article cannot give the quantization result of rational exploitation, which needs supplement and perfection of data. In addition,afforestation and maintenance of high coverage of surface vegetation is conducive to the storage of groundwater and rainfall recharge of groundwater,and giving priority to ecological management in dune-meadow transition zone near the lake and meadow whose groundwater discharge is weak has more advantages to the storage of shallow groundwater.
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