Showing items related by title, author, creator and subject.

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  Fusion of Time-Lapse Gravity Survey and Hydraulic Tomography for Estimating Spatially Varying Hydraulic Conductivity and Specific Yield Fields

  Tsai, Jui-Pin; Yeh, Tian-Chyi Jim; Cheng, Ching-Chung; Zha, Yuanyuan; Chang, Liang-Cheng; Hwang, Cheinway; Wang, Yu-Li; Hao, Yonghong; Univ Arizona, Dept Hydrol & Atmospher Sci; Department of Civil Engineering; National Chiao-Tung University; Hsinchu Taiwan; et al. (AMER GEOPHYSICAL UNION, 2017-10)

  Hydraulic conductivity (K) and specific yield (S-y) are important aquifer parameters, pertinent to groundwater resources management and protection. These parameters are commonly estimated through a traditional cross-well pumping test. Employing the traditional approach to obtain detailed spatial distributions of the parameters over a large area is generally formidable. For this reason, this study proposes a stochastic method that integrates hydraulic head and time-lapse gravity based on hydraulic tomography (HT) to efficiently derive the spatial distribution of K and Sy over a large area. This method is demonstrated using several synthetic experiments. Results of these experiments show that the K and Sy fields estimated by joint inversion of the gravity and head data set from sequential injection tests in unconfined aquifers are superior to those from the HT based on head data alone. We attribute this advantage to the mass constraint imposed on HT by gravity measurements. Besides, we find that gravity measurement can detect the change of aquifer's groundwater storage at kilometer scale, as such they can extend HT's effectiveness over greater volumes of the aquifer. Furthermore, we find that the accuracy of the estimated fields is improved as the number of the gravity stations is increased. The gravity station's location, however, has minor effects on the estimates if its effective gravity integration radius covers the well field.
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  A COMPARISON OF METHODS FOR MEASUREMENT OF PRESSURE IN HYDRAULIC LINES

  Sprague, Susan; Chorney, Andrew; Naval Air Warfare Center Aircraft Division (International Foundation for Telemetering, 2000-10)

  This presentation summarizes a study characterizing strain gages and pressure transducers used to measure the fluid pressure within aircraft hydraulic lines. A series of laboratory calibrations and finite element analyses was performed to demonstrate the quality of data from both pressure transducers and strain gages under variations in both temperature and external strains on the hydraulic lines. Strain gages showed a marked susceptibility to external strains on hydraulic lines, and wide variations in susceptibility to temperature changes. Pressure transducers were found to be relatively immune to both conditions. It is recommended that strain gages be used for trend data only.
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  Investigation of relations between the geometrical properties and hydraulic properties of jointed rock through numerical simulation.

  Panda, Bibhuti Bhusan.; Kulatilake, P. H. S. W.; Glass, Charles E.; Lever, Paul J.A.; Contractor, Dinshaw N. (The University of Arizona., 1995)

  Effect of joint geometry parameters and joint transmissivity on the hydraulic properties of jointed rock including the equivalent permeability tensor is investigated through a series of numerical experiments. The equivalent continuum hydraulic behavior of jointed rock was found to be sensitive to the orientation of the joint sets in a joint network system. The chances for the equivalent continuum behaviour were found to increase with the increase of joint density and joint size. It was found that for some joint systems, the equivalent continuum behavior does not exist irrespective of the rock block size; joint systems with low orientation angles, low joint densities and small joint sizes seem to have chance belonging to this category. The equivalent continuum behavior of a joint system can be expressed with respect to a cut-off value for the first invariant of fracture tensor (F0). If the F0 value for a given joint network is more than the cut-off value, then the joint system can be approximated by an equivalent continuum. For the joint systems investigated in this study, values between 10 and 30 were found for cut-off F0. A threshold value of F0 between 3 and 6 was found to achieve a non-zero average block permeability (K0). Both the threshold value and the cut-off value of F0 were found to depend on the relative orientations of joint sets. Chances to reach equivalent continuum behavior for a rock mass having a certain joint configuration increases with the increase of block size. REV size for a joint system was found to depend on the orientation of the joint sets and on the distribution of joint size and density. REV size seems to decrease with increasing joint density. The block size corresponding to the aforementioned cut-off F0 can be considered to provide the REV size for a given joint configuration. For a considered joint network, K0 increases with the increase of block size until the block size is equal to REV size. The K0 value at the REV size for a joint system increases with increase in joint size and joint density. The relation between K0 and F0 seems to depend on the relative orientation of the joint sets in the joint network. Joint hydraulic conductivity plays a major role on the equivalent continuum behaviour and permeability anisotropy. A non linear relation seems to exist between the directional permeability and the fracture tensor component for the connected joint configuration when rock blocks contain minor discontinuities. For rock blocks containing major discontinuities this relation becomes linear.