scholarly journals In-situ estimation of subsurface hydro-geomechanical properties using the groundwater response to Earth and atmospheric tides

2021 ◽  
Author(s):  
Timothy C. McMillan ◽  
Martin S. Andersen ◽  
Wendy A. Timms ◽  
Gabriel C. Rau
Keyword(s):  
Water Levels ◽  
Atmospheric Tides ◽  
New Approach ◽  
Geomechanical Properties ◽  
Groundwater Response ◽  
In Situ Conditions ◽  
The Impact ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

Abstract. Subsurface hydro-geomechanical properties crucially underpin the management of Earth's resources, yet they are predominantly measured on core-samples in the laboratory while little is known about the representativeness of in-situ conditions. The impact of Earth and atmospheric tides on borehole water levels are ubiquitous and can be used to characterise the subsurface. We illustrate that disentangling the groundwater response to Earth and atmospheric tidal forces in conjunction with hydraulic and linear poroelastic theories leads to a complete determination of the whole hydro-geomechanical parameter space for unconsolidated systems. Further, the characterisation of consolidated systems is possible when using literature estimates of the grain compressibility. While previous field investigations have assumed a Poisson's ratio from literature values, our new approach allows for its estimation under in-situ field conditions. We apply this method to water level and barometric pressure records from four field sites with contrasting hydrogeology. Estimated hydro-geomechanical properties (e.g. specific storage, hydraulic conductivity, porosity, shear-, Young's- and bulk- moduli, Skempton's and Biot-Willis coefficients and undrained/drained Poisson's ratios) are comparable to values reported in the literature, except for consistently negative drained Poisson's ratios which are surprising. Our results reveal an anisotropic response to strain, which is expected for a heterogeneous (layered) lithological profile. Closer analysis reveals that negative Poisson's ratios can be explained by differing in-situ conditions to those from typical laboratory core tests and the small strains generated by Earth and atmospheric tides. Our new approach can be used to passively, and therefore cost-effectively, estimate subsurface hydro-geomechanical properties representative of in-situ conditions. Our method can be used to improve our understanding of the relationship between geological heterogeneity and geomechanical behaviour.

scholarly journals Assessing the hydrological impacts of agricultural changes upstream of the Tunisian World Heritage sea-connected Ichkeul Lake

2015 ◽  
Vol 365 ◽  
pp. 61-65 ◽  
Author(s):  
J. Aouissi ◽  
Z. L. Chabaane ◽  
S. Benabdallah ◽  
C. Cudennec
Keyword(s):  
Agricultural Land ◽  
World Heritage ◽  
Water Levels ◽  
World Heritage Site ◽  
Landsat Images ◽  
Heritage Site ◽  
Unesco World Heritage Site ◽  
Ichkeul Lake ◽  
The Impact

Abstract. The impact of changes in agricultural land use and practices as a controlling driver of hydrologic response and as a source of diffuse pollution, are studied in the Joumine River basin, discharging into the Ichkeul Lake, northern Tunisia, a UNESCO World Heritage site since 1979. The lake is characterized by a very specific hydrological functioning based on a seasonal alternation of water levels and salinity through its link to the Mediterranean Sea. Three Landsat images, in situ surveys and SWAT modelling were used to simulate and assess streamflows and nitrate loads under retrospective land uses.

Disentangling the groundwater response to Earth and atmospheric tides reveals subsurface processes and properties

2020 ◽  
Author(s):  
Gabriel Rau ◽  
Timothy McMillan ◽  
Mark Cuthbert ◽  
Martin Andersen ◽  
Wendy Timms ◽  
...  
Keyword(s):  
Water Level ◽  
Amplitude Ratio ◽  
Atmospheric Tides ◽  
Frequency Domain Method ◽  
Specific Storage ◽  
Strain Anisotropy ◽  
Geomechanical Properties ◽  
Groundwater Response ◽  
Borehole Water ◽  
Harmonic Components

<p>In situ quantification of subsurface hydro-geomechanical properties is challenging and requires significant effort. Evolving research illustrates that subtle harmonic components in groundwater head measurements caused by Earth and atmospheric tides can be utilised to explore groundwater systems with little effort compared to traditional investigations. One long standing problem has been that, for dominant tidal components, Earth and atmospheric tides occur at the same frequency which prevents the use of the groundwater response to their individual forcing to infer subsurface properties. While Acworth et al. (2016) offered a way forward, their approach has assumptions that limit the applicability. Here, we illustrate an extended method that disentangles the borehole water level response and attributes magnitude and phase to their individual drivers. As a result, we obtain individual changes in harmonic properties of the drivers and their groundwater response (amplitude ratio and phase shift) using borehole water level records from different locations. In conjunction with groundwater flow and poroelastic theory, these properties can be used to infer the state of confinement, quantify specific storage and hydraulic conductivity as well as barometric efficiency of the formation. Further, because the stresses imposed by Earth and atmospheric tides are volumetric and uniaxial, respectively, their individual responses can be used to reveal strain anisotropy. Our new approach is passive, i.e. it only requires the measurements of atmospheric and groundwater pressure records, and can provide further insight into subsurface processes and properties using information hidden in standard pressure records.</p><p> </p><p>Acworth, R. I., Halloran, L. J. S., Rau, G. C., Cuthbert, M. O., and Bernardi, T. L. ( 2016), An objective frequency domain method for quantifying confined aquifer compressible storage using Earth and atmospheric tides, Geophys. Res. Lett., 43, 11,671–11,678, doi:10.1002/2016GL071328.</p>

Sonic to ultrasonic Q of sandstones and limestones: Laboratory measurements at in situ pressures

Geophysics ◽  
2009 ◽  
Vol 74 (2) ◽  
pp. WA93-WA101 ◽  
Author(s):  
Clive McCann ◽  
Jeremy Sothcott
Keyword(s):  
Wave Attenuation ◽  
Shear Waves ◽  
Compressional Wave ◽  
Ultrasonic Frequency ◽  
Laboratory Measurements ◽  
Compressional Waves ◽  
Wave Velocities ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

Laboratory measurements of the attenuation and velocity dispersion of compressional and shear waves at appropriate frequencies, pressures, and temperatures can aid interpretation of seismic and well-log surveys as well as indicate absorption mechanisms in rocks. Construction and calibration of resonant-bar equipment was used to measure velocities and attenuations of standing shear and extensional waves in copper-jacketed right cylinders of rocks ([Formula: see text] in length, [Formula: see text] in diameter) in the sonic frequency range and at differential pressures up to [Formula: see text]. We also measured ultrasonic velocities and attenuations of compressional and shear waves in [Formula: see text]-diameter samples of the rocks at identical pressures. Extensional-mode velocities determined from the resonant bar are systematically too low, yielding unreliable Poisson’s ratios. Poisson’s ratios determined from the ultrasonic data are frequency corrected and used to calculate thesonic-frequency compressional-wave velocities and attenuations from the shear- and extensional-mode data. We calculate the bulk-modulus loss. The accuracies of attenuation data (expressed as [Formula: see text], where [Formula: see text] is the quality factor) are [Formula: see text] for compressional and shear waves at ultrasonic frequency, [Formula: see text] for shear waves, and [Formula: see text] for compressional waves at sonic frequency. Example sonic-frequency data show that the energy absorption in a limestone is small ([Formula: see text] greater than 200 and stress independent) and is primarily due to poroelasticity, whereas that in the two sandstones is variable in magnitude ([Formula: see text] ranges from less than 50 to greater than 300, at reservoir pressures) and arises from a combination of poroelasticity and viscoelasticity. A graph of compressional-wave attenuation versus compressional-wave velocity at reservoir pressures differentiates high-permeability ([Formula: see text], [Formula: see text]) brine-saturated sandstones from low-permeability ([Formula: see text], [Formula: see text]) sandstones and shales.

Mimicking skyglow at ecosystem level in a large-scale lake enclosure facility

2021 ◽  
Author(s):  
Andreas Jechow ◽  
Günther Schreck ◽  
Christopher C. M. Kyba ◽  
Stella A. Berger ◽  
Lukas Thuile Bistarelli ◽  
...  
Keyword(s):  
Large Scale ◽  
Light Pollution ◽  
Homogeneous Surface ◽  
Light Emitting ◽  
Illumination System ◽  
In Situ Conditions ◽  
Ecosystem Level ◽  
White Light Emitting Diodes ◽  
The Impact

Abstract Light pollution is an environmental stressor of global extent that is growing exponentially in area and intensity. Artificial skyglow, a form of light pollution with large range, is hypothesized to have environmental impact at ecosystem level. However, testing the impact of skyglow at large scales and in a controlled fashion under in situ conditions has remained elusive so far. Here we present the first experimental setup to mimic skyglow at ecosystem level outdoors in an aquatic environment. Spatially diffuse and homogeneous surface illumination that is adjustable between 10 mlx and 10 lx, resembling rural to urban skyglow levels, was achieved with white light-emitting diodes at a large-scale lake enclosure facility. The illumination system was enabled by optical modeling with Monte-Carlo raytracing and validated by measurements. Our method can be adapted to other outdoor and indoor skyglow experiments, urgently needed to understand the impact of skyglow on ecosystems.

scholarly journals DAHITI – an innovative approach for estimating water level time series over inland waters using multi-mission satellite altimetry

2015 ◽  
Vol 19 (10) ◽  
pp. 4345-4364 ◽  
Author(s):  
C. Schwatke ◽  
D. Dettmering ◽  
W. Bosch ◽  
F. Seitz
Keyword(s):  
Time Series ◽  
Water Level ◽  
Satellite Altimetry ◽  
Water Levels ◽  
Altimeter Data ◽  
Inland Waters ◽  
New Approach ◽  
Inland Water ◽  
Rivers And Lakes

Abstract. Satellite altimetry has been designed for sea level monitoring over open ocean areas. However, for some years, this technology has also been used to retrieve water levels from reservoirs, wetlands and in general any inland water body, although the radar altimetry technique has been especially applied to rivers and lakes. In this paper, a new approach for the estimation of inland water level time series is described. It is used for the computation of time series of rivers and lakes available through the web service "Database for Hydrological Time Series over Inland Waters" (DAHITI). The new method is based on an extended outlier rejection and a Kalman filter approach incorporating cross-calibrated multi-mission altimeter data from Envisat, ERS-2, Jason-1, Jason-2, TOPEX/Poseidon, and SARAL/AltiKa, including their uncertainties. The paper presents water level time series for a variety of lakes and rivers in North and South America featuring different characteristics such as shape, lake extent, river width, and data coverage. A comprehensive validation is performed by comparisons with in situ gauge data and results from external inland altimeter databases. The new approach yields rms differences with respect to in situ data between 4 and 36 cm for lakes and 8 and 114 cm for rivers. For most study cases, more accurate height information than from other available altimeter databases can be achieved.

scholarly journals Kalman filter approach for estimating water level time series over inland water using multi-mission satellite altimetry

2015 ◽  
Vol 12 (5) ◽  
pp. 4813-4855 ◽  
Author(s):  
C. Schwatke ◽  
D. Dettmering ◽  
W. Bosch ◽  
F. Seitz
Keyword(s):  
Time Series ◽  
Kalman Filter ◽  
Water Level ◽  
Satellite Altimetry ◽  
Water Levels ◽  
Altimeter Data ◽  
New Approach ◽  
Inland Water ◽  
Filter Approach

Abstract. Satellite altimetry has been designed for sea level monitoring over open ocean areas. However, since some years, this technology is also used for observing inland water levels of lakes and rivers. In this paper, a new approach for the estimation of inland water level time series is described. It is used for the computation of time series available through the web service "Database for Hydrological Time Series over Inland Water" (DAHITI). The method is based on a Kalman filter approach incorporating multi-mission altimeter observations and their uncertainties. As input data, cross-calibrated altimeter data from Envisat, ERS-2, Jason-1, Jason-2, Topex/Poseidon, and SARAL/AltiKa are used. The paper presents water level time series for a variety of lakes and rivers in North and South America featuring different characteristics such as shape, lake extent, river width, and data coverage. A comprehensive validation is performed by comparison with in-situ gauge data and results from external inland altimeter databases. The new approach yields RMS differences with respect to in-situ data between 4 and 38 cm for lakes and 12 and 139 cm for rivers, respectively. For most study cases, more accurate height information than from available other altimeter data bases can be achieved.

In situ determination of a rock mass modulus using a high resolution tiltmeter

1996 ◽  
Vol 33 (2) ◽  
pp. 350-355 ◽  
Author(s):  
Bassam Saleh ◽  
Abdallah I Husein Malkawi ◽  
Pierre A Blum
Keyword(s):  
Rock Mass ◽  
High Resolution ◽  
Boussinesq Model ◽  
New Approach ◽  
Structural Work ◽  
Rock Mass Modulus ◽  
Elastic Rock ◽  
The Impact

A very high resolution tiltmeter (10–8 rad, 0.002 s) developed by P.A. Blum, in 1957 was used to establish a new approach to directly evaluate the in situ average elastic rock-mass modulus. Five tiltmeters were installed on the facades of the Louvre museum to study the deformations induced by internal structural work and by the impact of the Paris metro traffic movement. The measured data from the tiltmeter were used to determine the elastic rock modulus of the museum's foundation using the Boussinesq model. The results obtained by the developed approach are consistent with the typical elastic rock-mass modulus for the rock found in the museum's foundations. Key words: rock-mass modulus, tiltmeter, deformation, Boussinesq model.

scholarly journals Design and implementation of an illumination system to mimic skyglow at ecosystem level in a large-scale lake enclosure facility

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Andreas Jechow ◽  
Günther Schreck ◽  
Christopher C. M. Kyba ◽  
Stella A. Berger ◽  
Lukas Thuile Bistarelli ◽  
...  
Keyword(s):  
Large Scale ◽  
Light Pollution ◽  
Homogeneous Surface ◽  
Light Emitting ◽  
Illumination System ◽  
In Situ Conditions ◽  
Ecosystem Level ◽  
White Light Emitting Diodes ◽  
The Impact

AbstractLight pollution is an environmental stressor of global extent that is growing exponentially in area and intensity. Artificial skyglow, a form of light pollution with large range, is hypothesized to have environmental impact at ecosystem level. However, testing the impact of skyglow at large scales and in a controlled fashion under in situ conditions has remained elusive so far. Here we present the first experimental setup to mimic skyglow at ecosystem level outdoors in an aquatic environment. Spatially diffuse and homogeneous surface illumination that is adjustable between 0.01 and 10 lx, resembling rural to urban skyglow levels, was achieved with white light-emitting diodes at a large-scale lake enclosure facility. The illumination system was enabled by optical modeling with Monte-Carlo raytracing and validated by measurements. Our method can be adapted to other outdoor and indoor skyglow experiments, urgently needed to understand the impact of skyglow on ecosystems.

scholarly journals Experimental study of shale drillability with different bedding inclinations under varying wellbore pressure conditions

2021 ◽  
Vol 11 (4) ◽  
pp. 1751-1759
Author(s):  
Shuai Chen ◽  
Xiangchao Shi ◽  
Heng Bao ◽  
Leiyu Gao ◽  
Jie Wu
Keyword(s):  
Mechanical Properties ◽  
Shale Gas ◽  
Physical And Mechanical Properties ◽  
In Situ Conditions ◽  
Wellbore Pressure ◽  
Development Engineering ◽  
The Impact ◽  
The Relationship ◽  
Insight Into

AbstractIn the practice of shale gas development engineering, it is important to understand the physical and mechanical properties of shale. The bedding inclinations of shale are known to significantly influence its physical and mechanical properties. This study mainly examined the influence of bedding inclinations on drillability under different wellbore pressures. The bedding inclinations used in this study varied from 0° to 90°, with a gradient of 15°. The wellbore pressure values used varied from 0 to 25 MPa, with a gradient of 5 MPa. The results show that the drillability index of shale increases exponentially with increasing wellbore pressure at different bedding inclinations. The proposed exponential empirical model can describe the relationship between the drillability index and wellbore pressure. When the wellbore pressure is less than 15 MPa, bedding inclinations significantly influence the drillability index, and the drillability index of shale shows a “W”-type variation trend as the bedding inclinations increase in the range of 0° to 90°. The influence of bedding inclinations on drillability decreases gradually with increasing wellbore pressure. When the wellbore pressure increases to 25 MPa, the impact of bedding inclinations on drillability is virtually undetectable. The results of this study can provide reasonably insight into the effect of bedding inclinations on shale deformation under the drill bit, and useful prediction for the drillability index under in situ conditions.

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