Assessing Horizontal Strain and Deformation From Extensometer Data

根据引伸计数据评估水平应变和变形

• 批准号: 9902728
• 负责人: Thomas Burbey
• 金额: $ 10.25万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-08-15 至 2001-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9902728&HistoricalAwards=false
• 关键词: Assessing; Horizontal; Strain; Deformation; Extensometer

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

burbeyextensometer数据已与水文数据一起用于确定含水层和含水层的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应力相关的应变是垂直的假设。因此，任何与应力增加有关的应变都与通过垂直压缩性或水文地质单元的特定储存而产生的压实直接相关。现场数据和Biot的三维固结理论表明，水平应变可能是显著的，并从储存中贡献了大量的水。这些结果表明，比库容的经典定义可能不适用于松散的承压含水层。计算出的与体积应变相关的收缩往往小于与垂直应变相关的收缩。因此，仅假设垂直应变条件下从延伸计数据估计的特定存储可能太低。提出的工作包括检查从循环应力系统的应力-应变迟滞回线，其中延伸计和水文数据可用。由于延伸仪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”可以与水文数据结合使用，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将是首先用垂直染色模型模拟迟滞回路。其次，采用体积应变法对同一系统进行模拟。第三种方法将涉及编写一个新开发的分析孔隙粘性模型，该模型考虑了有效应力作用下储层和孔隙度的瞬态性质。这项工作将对我们从含水层测试中解释蓄水系数有很大的影响，并将极大地帮助我们了解沉降盆地的含水层变形，特别是在已知由过度抽水引起的地裂缝的地方