Relationship between Land Subsidence and Hydraulic Head under Jacob Assumptions

摘要

A time-space distribution of large-scale land subsidence resulted from groundwater extraction frequently corresponds terrifically to that of groundwater level, which always behaves like a descent funnel, in a plain or basin region. In this paper, a theory of linear functional relationship between land subsidence and hydraulic head drawdown is developed under Jacob assumptions and then verified and perfected by cases study. The theoretical research and the cases study indicate: drawdown can lead to land subsidence; land subsidence value depends on not only the drawdown but also thickness and skeletal elastic specific storage of vertical compaction layer; just like seepage starts to happen in clayed formation only if hydraulic head gradient is greater than the initial, an initial drawdown is needed to start up the vertical water release and compaction; the vertical compaction of clayed formations satisfies Jacob assumptions; the vertical compaction formations consist mainly of clayed layers and interbeds, which coincides with the research conclusion of Thomas J. Burbey, Virginia University, on major directions of deformation of water-bearing deposits; land subsidence is mostly resulted from the vertical compression strain of clayed water-bearing deposits.