Assessing Horizontal Strain and Deformation From Extensometer Data

9902728 BurbeyExtensiometer数据已与水文数据一起用于确定含水层和弱透水层的弹性和非弹性特定存储值。 当先期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。 与小于过去最大先期固结应力阈值的应力相关的特定存储的组件是弹性的。 这些具体的存储估计是基于与所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压缩性或特定存储的压实直接相关。现场数据和毕奥的三维固结理论表明，水平应变可能是显着的，并从存储贡献大量的水。 这些结果表明，特定存储的经典定义可能不适用于松散承压含水层。 与体积应变相关的计算压降往往小于垂直应变。 因此，仅假设垂直应变条件，根据引伸计数据估计的比贮量可能太低。 拟议的工作涉及检查循环应力系统的应力-应变滞后环，其中可以获得引伸计和过程线数据。 由于引伸计数据通过变形的垂直分量表示体积应变，因此假设应力-应变环的“形状”可以与过程线数据结合使用，以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程序是首先用垂直应变模型模拟滞后回线。 其次，将使用体积应变法模拟相同的系统。 第三种方法将涉及编程一个新开发的分析孔隙粘性模型，该模型解释了在施加有效应力下的储存和孔隙度的瞬态性质。 这项工作将有很大的影响，在我们的解释储存系数从含水层测试，并将大大有助于我们了解含水层变形的沉降盆地，特别是在地球裂缝是众所周知的结果，过度抽水

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