Assessing Horizontal Strain and Deformation From Extensometer Data

9902728伯贝延伸仪数据已与水文数据结合使用，以确定含水层和含水层弹性和非弹性比储存值。当预固结应力阈值超过过去的最大应力时，可压缩含水层经历原始或非弹性压缩。与小于过去最大预固结应力阈值的应力相关的特定存储组件是弹性的。这些具体的存储估计是基于与施加的应力相关的应变是垂直的假设。因此，与应力增加相关的任何应变都与通过水文地质单元的垂直可压缩性或特定存储而产生的压实直接相关。现场数据和毕奥的三维固结理论表明，水平应变可能很大，并从存储中贡献大量的水。这些结果表明，特定储水量的经典定义可能不适用于松散的承压含水层。与体积应变相关的计算出的压降往往比垂直应变的压降小。因此，仅假设垂直应变条件下的延伸仪数据对特定存储空间的估计可能会太低。拟议的工作包括检查来自循环应力系统的应力-应变滞后环，在这些系统中，延伸仪和水位线数据是可用的。由于伸缩仪数据通过变形的垂直分量来表示体积应变，因此可以假设应力-应变环的“形状”可以与水文数据一起用来估计或评估含水层系统的水平应变和变形分量。这一假设将使用合成数据和现有数据进行检验。检验这一假设的有效性的步骤将是首先用垂直染色模型模拟滞后环。其次，用体积应变法对相同的系统进行了模拟。第三种方法将涉及编程一个新开发的分析多孔粘性模型，该模型考虑了在外加有效应力下的存储和孔隙度的瞬变性质。这项工作将对我们从含水层测试中解释储水系数具有重大意义，并将极大地帮助我们理解下沉盆地中的含水层变形，特别是在已知地裂缝是由于过度抽水而产生的盆地中。

9902728BurbeyExtensometer data have been used with hydrograph data to determine aquifer and aquitard elastic and inelastic specific storage values. A compressible aquifer experiences virgin or inelastic compression when the preconsolidation stress threshold exceeds the past maximum stress. The component of specific storage associated with stresses less than the past-maximum preconsolidation stress threshold is elastic. These specific storage estimates are based on the assumption that the strain associated with the applied stress is vertical. Consequently any strain associated with an increase stress is directly related to the compaction through the vertical compressibility or specific storage of the hydrogeologic unit.Field data and Biot's theory of three-dimensional consolidation demonstrates that horizontal strain may be significant, and contribute large quantities of water from storage. These results suggest that the classical definition of specific storage may not be applicable for unconsolidated confined aquifers. Calculated drawdowns associated with volume strain tend to be less than those for vertical strain. Hence, estimates of specific storage from extensometer data assuming vertical strain conditions only will likely be too low. The proposed work involves examining stress-strain hysteresis loops from cyclically stressed systems where extensometer and hydrograph data are available. Because extensometer data express the volume strain through the vertical component of deformation, it is hypothesized that the "shape" of the stress-stain loops can be used in conjunction with the hydrograph data to estimate or assess the component of horizontal strain and deformation of the aquifer system. This hypothesis will be tested using both synthetic and existing data. The procedure for examining the validity of this hypothesis will be to simulate first the hysteresis loops with vertical stain models. Secondly, the same systems will be simulated using the volume strain method. The third approach will involve programming a newly developed analytic poroviscous model that accounts for the transient nature of storage and porosity under an applied effective stress. This work will have large implications in our interpretation of storage coefficient from aquifer tests and will greatly help our understanding of aquifer deformation in subsiding basins, particularly where earth fissures are known to result from over-pumping