The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
Lucia Simeoni - One of the best experts on this subject based on the ideXlab platform.
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laboratory tests for measuring the time lag of fully grouted Piezometers
Journal of Hydrology, 2012Co-Authors: Lucia SimeoniAbstract:Summary Time-lag is the most important parameter describing the conformance of a piezometer because it represents the time that it takes for the instrument to reach equilibrium when there is a pore water pressure change in the soil. The use of fully grouted Piezometers would make the installation easier and faster than the conventional one, since it prevents the failure risks during the placement of the sand pack and the overlying bentonite seal. This paper describes a number of laboratory tests performed to evaluate the time-lag of fully grouted Piezometers. A pore water pressure change was applied at the bottom of cylindrical samples of grout and the pressure equalization was measured at the top. The samples were made of a cement–bentonite mixture and were 2 cm, 4 cm or 8 cm in height. Time-lags resulted in no longer than 6 min, that is a time generally acceptable in geotechnical projects. It was also found that the time-lag relies on the pore water pressure value. For a given draining path length, the higher the pore water pressure the shorter the response time. This behavior has been explained by assuming that the time-lag depends on both the hydraulic and compressible characteristics of the grout mixture and that these characteristics vary with the pore water pressure because the grout is in a quasi saturated state.
G. Van Der Kamp - One of the best experts on this subject based on the ideXlab platform.
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Meteorological, soil moisture, surface water, and groundwater data from the St. Denis National Wildlife Area, Saskatchewan, Canada
Copernicus Publications, 2019Co-Authors: R. Anne, S. Udhathoki, A. M. Ireso, C. Spence, G. Van Der KampAbstract:The St. Denis National Wildlife Area is located in the seasonally frozen and semi-arid Canadian Prairies, close to Saskatoon, Saskatchewan. The site has a hummocky terrain and is underlain by clay-rich glacial tills. Though the site is only 4 km2 it contains hundreds of wetlands containing ponds which range in size, in permanence (from ephemeral to permanent), and in their interactions with groundwater (recharge and discharge ponds are present). The site was established as a research area in 1968 and has long-term records of hydrological observations, including meteorological, snow, soil moisture, surface water (ponds) and groundwater data. Some records, notably the pond level and chemistry data, span the period 1968 to present. Other datasets, notably water level observations from networks of Piezometers, have been collected sporadically at different locations and times. Some datasets are collected manually on an annual basis, including pond surveys and snow surveys. Meteorological data have been collected by automatic weather stations since 1989 and have been maintained and upgraded over time, with a flux tower added to the site in 2011. Automatically logged soil moisture profiles and collocated Piezometers have been running since 2013. A lidar survey from 2005 provides a 1 m resolution digital elevation map (DEM) of the site and surrounding landscape. The compiled data are available at https://doi.org/10.20383/101.0115 (Bam et al., 2018).
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monitoring of total soil moisture on a scale of hectares using groundwater Piezometers
Geophysical Research Letters, 1997Co-Authors: G. Van Der Kamp, Randy SchmidAbstract:A method has been developed for continuous measurement of total soil moisture on a scale of hectares. The method is based on accurate measurement of groundwater pressures in thick clay formations and depends on the principle that changes of mechanical load result in changes of groundwater pressure. The resulting data are similar to those obtained by conventional weighing lysimeters, but on a much larger scale and with no significant hydrologic disturbance of the site. Several years of field testing show the method to be practicable.
Jan Tullis - One of the best experts on this subject based on the ideXlab platform.
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a new perspective on paleopiezometry dynamically recrystallized grain size distributions indicate mechanism changes
Geology, 2010Co-Authors: Michael Stipp, Martin Scherwath, Jan Tullis, Jan H. BehrmannAbstract:The dynamically recrystallized grain size is a material parameter associated with dislocation creep of crystalline solids that is especially important as a flow stress indicator via piezometer calibrations. Grain sizes have been measured in many studies of deformed rocks as well as metals and ceramics, but global analyses of the frequency distribution of dynamically recrystallized grain sizes are lacking. Here we present the first systematic investigation of the recrystallized grain size distribution, for quartz. The grain diameters, compiled from 555 samples of 31 studies of quartz mylonites deformed over a wide range of conditions, extend from ∼3 μm to 3 mm, with distinct maxima at 10–20 μm and 70–80 μm, and minima at 35–40 μm and ∼120 μm. The frequency maxima correlate with distinct microstructures and the minima with the transitions between these microstructures, which we interpret to result from the dominance of the recrystallization mechanisms of bulging, subgrain rotation, and grain boundary migration recrystallization. These results demonstrate the necessity of distinct piezometer calibrations for different recrystallization mechanisms and highlight the importance of the recrystallized grain size for theoretical models of dynamic recrystallization.
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the recrystallized grain size piezometer for quartz
Geophysical Research Letters, 2003Co-Authors: Michael Stipp, Jan TullisAbstract:D=1 0 3.56±0.27 * s 1.26 ±0.13 , with no change in slope at the regime 2–3 transition and no effect of temperature or a/b stability field. Another experimental piezometer relation for regime 1 of Hirth and Tullis [1992] differs in slope, suggesting that different recrystallization mechanisms require different piezometer calibrations. INDEX TERMS: 3902 Mineral Physics: Creep and deformation; 5120 Physical Properties of Rocks: Plasticity, diffusion, and creep; 8030 Structural Geology: Microstructures; 8159 Tectonophysics: Rheology—crust and lithosphere; 8164 Tectonophysics: Stresses—crust and lithosphere. Citation: Stipp, M., and J. Tullis, The recrystallized grain size piezometer for quartz, Geophys. Res. Lett., 30(21), 2088, doi:10.1029/2003GL018444, 2003.
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a recrystallized grain size piezometer for experimentally deformed feldspar aggregates
Tectonophysics, 1999Co-Authors: Alice Post, Jan TullisAbstract:Abstract A recrystallized grain size piezometer for low-temperature migration recrystallization in feldspar has been experimentally calibrated. Hot-pressed samples of fine-grained albitic feldspar (grain size 1–10 μm) and a natural albitic feldspar aggregate (∼150 μm) were deformed in simple shear and axial compression at a temperature of 900°C and a confining pressure of 1500 MPa. Transmission electron microscopy (TEM) verified that deformation occurred by recrystallization-accommodated dislocation creep. Grain size distributions were measured from scanning electron microscopy (SEM) photographs of polished and etched samples. The results yield a recrystallized grain size piezometer relationship of d=55±5·σ−0.66±0.07 where d is the geometric mean grain size (μm) and σ the differential stress (MPa). The exponent is higher than that determined in previous studies of other materials for rotation recrystallization and high-temperature migration recrystallization, indicating that different recrystallization mechanisms have distinct recrystallized grain size piezometer relationships.
Eva V Arntze - One of the best experts on this subject based on the ideXlab platform.
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conducting slug tests in mini Piezometers
Ground Water, 2016Co-Authors: Adley G Fritz, Rob D Mackley, Eva V ArntzeAbstract:Slug tests performed using mini-Piezometers with internal diameters as small as 0.43 cm can provide a cost effective tool for hydraulic characterization. We evaluated the hydraulic properties of the apparatus in a laboratory environment and compared those results with field tests of mini-Piezometers installed into locations with varying hydraulic properties. Based on our evaluation, slug tests conducted in mini-Piezometers using the fabrication and installation approach described here are effective within formations where the hydraulic conductivity is less than 1 × 10(-3) cm/s. While these constraints limit the potential application of this method, the benefits to this approach are that the installation, measurement, and analysis is cost effective, and the installation can be completed in areas where other (larger diameter) methods might not be possible. Additionally, this methodology could be applied to existing mini-Piezometers previously installed for other purposes. Such analysis of existing installations could be beneficial in interpreting previously collected data (e.g., water-quality data or hydraulic head data).
W L Erendrech - One of the best experts on this subject based on the ideXlab platform.
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automated time series modeling for Piezometers in the national database of the netherlands
Ground Water, 2019Co-Authors: Willem Ja Zaadnoordijk, Aris Lourens, W L ErendrechAbstract:The Geological Survey of the Netherlands (TNO-GSN) maintains a public national database of groundwater head observations. Transfer function-noise modeling has been applied to the time series in order to extract the impulse response functions for precipitation and evaporation for each piezometer. An automated procedure has been developed to assess the quality of the time series and of the models. The time series models of sufficient quality offer far more homogeneous data on the piezometric head than the original measurements. This allows for improved mapping of the head at a specific date or of characteristics of the head like average summer or winter levels. Also, the separation of precipitation and evaporation from other influences is useful for groundwater management and policy. The individual time series models are available online with interactive graphics (https://www.grondwatertools.nl/grondwatertools-viewer). The spatial patterns of the impulse response function characteristics can support analyses of the groundwater system.