摘要
弱透水层释水变形伴随着水力参数(渗透系数K和贮水率Ss)的瞬态变化,传统的“移动窗口”式反演方法假定每个反演窗口的初始状态是静态的,这与弱透水层释水变形存在明显滞后效应的实际情况不符。本文提出了在高维参数反演优化情境下,时间域上模型参数的动态变化可与空间域上模型参数的一维非均质性等价,因而可用地质统计反演方法可用于识别弱透水层瞬态K和Ss的新思路,实现了该方法在水文地质领域的创新性应用。以上海越流含水层系统为例,运用似线性地质统计反演算法,高精度地拟合了F16分层标处的长观变形数据,获取了原位透镜体状弱透水层K和Ss的瞬态特征。反演结果显示,观测时段内K的变幅为1.02×10^(-5)~5.89×10^(-4)m/a,平均值为1.38×10^(-4)m/a,Ss的变幅为4.34×10^(-4)~6.02×10^(-3)m^(-1),平均值为2.65×10^(-3)m^(-1)。基于反演所得参数瞬态特征,分析原位弱透水层在1994年前后分别以弹性和塑性变形为主,弱透水层K呈现与含水层水位相反的季节性变化特征,该现象可能与渗流力作用下细粒物质在含水层与弱透水层透镜体交界面附近的对孔隙的阻塞和疏通作用有关。该方法可获取完整观测时段内水文地质参数的动态变化轨迹,在计算评价地表水-地下水交互领域的河床渗透性、原位修复领域的渗透反应墙渗透性等的动态演化特征方面具有潜在的应用价值,并可作为构建水文地质领域、岩土工程等领域有关本构模型的有效辅助手段。
Aquitard compaction is accompanied by transient changes in hydraulic parameters(i.e.,hydraulic conductivity K and specific storage Ss).The conventional“parameter optimization window”method commonly assumes that the initial condition of a physical process of interest is static,which is greatly inconsistent with the existence of an apparent time lag in aquitard drainage caused by the hydraulic response to groundwater level variations within bounding aquifers.From the perspective of high-dimension parameter optimization,the transience of a parameter in the time domain is equivalent to the heterogeneity in the 1D space domain.Consequently,the geostatistical inversion approach can be used to characterize the transience of aquitard K and Ss,and this is the creative application of this methodology in hydrogeology.In this study,the long-term compaction of the lower confined aquifer system,which includes three aquitard lenses,was recorded at the extensometer site F16 in Shanghai,China.The classical quasi-linear geostatistical approach was employed to interpret the observed compaction.The inversion results revealed that aquitard K varied between 1.02×10^(-5) m/a and 5.89×10^(-4) m/a,with an average value of 1.38×10^(-4) m/a,while Ss varied between 4.34×10^(-4) m^(-1) and 6.02×10^(-3) m^(-1),with an average value of 2.65×10^(-3) m^(-1).The inverse transience of aquitard K and Ss suggested that the aquitard compaction turned from elastic to inelastic behavior around the year 1994.Furthermore,the inversed K demonstrated a seasonal variation pattern that was reversed to that of the aquifer groundwater level.This abnormal phenomenon was analyzed as being partially attributed to the alternation of attachment and detachment of fine-grained particles in the pore space near the contact surface between the aquifer and the aquitard lens.The proposed new parameter estimation method demonstrates the ability to capture temporal variations of model parameters within a complete monitoring period.This suggests potential application value in calculating and evaluating the temporal variations in streambed permeability as well as the permeability of permeable reactive barriers used for in-situ,passive contamination remediation,and so on.Also,this newly introduced methodology can serve as a supplementary means for constructing relative constitutive models in the research areas of hydrogeology and geotechnical engineering.
作者
庄超
余文平
严龙
张健翼
窦智
杨蕴
周志芳
王锦国
ZHUANG Chao;YU Wenping;YAN Long;ZHANG Jianyi;DOU Zhi;YANG Yun;ZHOU Zhifang;WANG Jinguo(School of Earth Sciences and Engineering,Hohai University,Nanjing,Jiangsu 211100,China;Nanjing Hydraulic Research Institute,Nanjing,Jiangsu 210029,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2024年第1期324-331,共8页
Acta Geologica Sinica
基金
国家自然科学基金项目(编号42272279,41902244)
国家重点研发计划项目(编号2019YFC1804300)
中国博士后面上基金项目(编号2021M692866)联合资助的成果。
关键词
弱透水层
瞬态水力参数
地质统计反演
时空等价性
aquitard
transience of hydraulic parameters
geostatistical inversion
spatiotemporal equivalence