Determination of Mining-Induced Changes in Hydrogeological Parameters of Overburden Aquifer in a Coalfield, Northwest China: Approaches Using the Water Level Response to Earth Tides

The determination of changes in hydrogeological properties (e.g., permeability and specific storage) of aquifers disturbed by mining activity is significant to groundwater resource and ecological environment protection in coal mine areas. However, such parameters are difficult to continuously measure in situ using conventional hydrogeological methods, and their temporal changes associated with coal mining are not well understood. The response of well water level to Earth tides provides a unique probe to determine the in situ hydrogeological parameters and their variations. In this study, the tidal responses of well water level were employed to characterize the changes in hydrogeological parameters of the overburden aquifer induced by longwall mining in a coalfield, northwest China. Based on the long-term hourly recorded water level data, two analytical models were used to determine the temporal changes of permeability and specific storage of the overburden aquifer. The results showed that the hydrogeological parameters changed with the longwall coal face advance. When the longwall coal face approached the wells, the aquifer permeability increased several to dozens of times, and the response distance ranged from 80 m to 300 m. The specific storage decreased before the coal face reached wells and recovered after the coal face passed. The results of this study indicate that the hydrogeological parameter changes induced by coal mining are related to the location of the well relative to the coal face and the stress distribution in the overburden aquifer. This study revealed the changes in permeability and specific storage associated with the mining disturbance which could have great significance for quantitative assessment of the impact of mining on overburden aquifer.

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Determination of Hydrogeological Parameters of Aquifer Using the Air Compressor Pumping

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.448-453.3989 ◽

2013 ◽

Vol 448-453 ◽

pp. 3989-3992

Author(s):

Xue Jiang ◽

Xiu Juan Liang ◽

Chang Lai Xiao ◽

Chuan Du ◽

Zhong Kai Wang

Keyword(s):

Hydraulic Conductivity ◽

Water Level ◽

Oil Shale ◽

Pumping Test ◽

Comprehensive Analysis ◽

Graphic Method ◽

Air Compressor ◽

Hydrogeological Parameters

When the buried depth of water level is very large, the air compressor is used in pumping test. In the limited conditions, the value of the water level was not measured, but the recovery value of water level could be measured. In this case, the sp value of the water level drawdown was not able to be measured accurately when the pumping test stopped. So the hydraulic conductivity of aquifer could only be determined according to the linear graphic method of the water level recovery test. However, water level recovery characteristics of each period were not the same, and the raising rate of water level were not equal. Thus, there was a deviation when the hydraulic conductivity was solved with the linear graphic method. According to the existing data, the thesis combined the water level recovery fitting of the entire curve fitting with Dupuit formula of artesian well, determining the sp value and hydrogeological parameters of aquifer. After comprehensive analysis, the parameters obtained are more reasonable, which can provide a good reference for in-situ mining of oil shale in this area.

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Hydrogeological Characterization of Coastal Aquifer on the Basis of Observed Sea Level and Groundwater Level Fluctuations: Neretva Valley Aquifer, Croatia

Water ◽

10.3390/w12020348 ◽

2020 ◽

Vol 12 (2) ◽

pp. 348

Author(s):

Veljko Srzić ◽

Ivan Lovrinović ◽

Ivan Racetin ◽

Fanito Pletikosić

Keyword(s):

Sea Level ◽

Data Availability ◽

Problem Analysis ◽

Clay Layer ◽

In Situ Tests ◽

Specific Storage ◽

Hydrogeological Parameters ◽

Area Of Interest

Hydrogeological data availability is often limited to local areas where usual in situ tests or methods are applied (slug/bail or pumping tests, Electrical Resistivity Tomography (ERT)). Because most problems (e.g., saltwater intrusion mitigation) require problem analysis on larger scales (catchment or sub catchment), hydrogeological identification of global character is preferable. This work leads to the determination of aquifer hydrogeological parameters on the basis of observed sea level, groundwater piezometric head found inland, and barometric pressure. When applied to observed signals, the approach led efficiently to final hydrogeological characterization. After identification of dominant tidal constituents from observed signals, barometric efficiency was successfully determined. Following available information on geological settings, an appropriate conceptual model was applied and updated to count for polychromatic signals. Final determination of hydrogeological parameters relied on root mean square error (RMSE) minimization and led to determination of (i) presence of three stratigraphic units: unconfined sandy aquifer on the top, a confining layer made of clay, and a confined gravel layer; (ii) existence of the clay layer under the sea with a total length of 1400 m; (iii) a clay layer has been identified as confining one by both spectral analysis and determined leakance value; and (iv) estimated confined aquifer specific storage ranging from 2.87 × 10−6 to 4.98 × 10−6 (m−1), whereas hydraulic conductivity ranged from 7.0 × 10−4 to 7.5 × 10−3 (m s−1). Both range intervals corresponded to previous in situ findings conducted within the area of interest.

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Well Water Level Analysis Based on Barometric Pressure Effects and Earth Tides

Earth Sciences ◽

10.11648/j.earth.20190801.11 ◽

2019 ◽

Vol 8 (1) ◽

pp. 1

Author(s):

Fenghe Ding

Keyword(s):

Water Level ◽

Barometric Pressure ◽

Pressure Effects ◽

Earth Tides ◽

Well Water ◽

Well Water Level ◽

Level Analysis

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Confined well water level

Rock Stress and Earthquakes ◽

10.1201/b10555-144 ◽

2010 ◽

pp. 829-832

Author(s):

F Huang ◽

Y Zhang ◽

G Lai ◽

R Yan

Keyword(s):

Water Level ◽

Well Water ◽

Well Water Level

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Fixed Electrode Conductivity Sensor for Deep Well Water Level Monitoring

Water International ◽

10.1080/02508068708686567 ◽

1987 ◽

Vol 12 (1-2) ◽

pp. 53-54

Author(s):

Mark Austin

Keyword(s):

Water Level ◽

Well Water ◽

Deep Well ◽

Conductivity Sensor ◽

Well Water Level ◽

Fixed Electrode ◽

Level Monitoring ◽

Water Level Monitoring

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Analysis of the Response Mechanism of Confined Aquifer Well Water Level System to Bulk Strain

Chinese Journal of Geophysics ◽

10.1002/cjg2.1464 ◽

2009 ◽

Vol 52 (6) ◽

pp. 1389-1401

Author(s):

Xu-Yan LIU ◽

Xiao-Jing ZHENG ◽

Lin WANG ◽

Ying-Feng JI

Keyword(s):

Water Level ◽

Well Water ◽

Confined Aquifer ◽

Level System ◽

Response Mechanism ◽

Bulk Strain ◽

Well Water Level

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A review of specific storage values from pore pressure response to passive in situ stresses: Implications for sustainable groundwater management

10.5194/egusphere-egu2020-11002 ◽

2020 ◽

Author(s):

Wendy A Timms ◽

M Faysal Chowdhury ◽

Gabriel C Rau

Keyword(s):

Groundwater Management ◽

Pore Pressure ◽

Pressure Response ◽

Earth Tides ◽

Low Permeability ◽

Specific Storage ◽

Sustainable Groundwater Management ◽

In Situ Stresses ◽

Pore Pressure Response

Specific storage (Ss) values are important for analyzing the quantity of stored groundwater and for predicting drawdown to ensure sustainable pumping. This research compiled Ss values from multiple available studies based on pore pressure responses to passive stresses, for comparison and discussion with relevant poroelastic theory and groundwater applications. We find that Ss values from pore pressure responses to passive in situ stresses ranged from 1.3x10-7 to 3.7x10-5 m-1 (geomean 2.0x10-6 m-1, n=64 from 24 studies). This large Ss dataset for confined aquifers included both consolidated and unconsolidated strata by extending two recent literature reviews. The dataset included several passive methods: Individual strains from Earth tides and atmospheric loading, their combined effect, and values derived from soil moisture loading due to rainfall events. The range of Ss values spans approx. 2 orders of magnitude, far less than for hydraulic conductivity, a finding that has important implications for sustainable groundwater management. Both the range of values and maximum Ss values in this large dataset were significantly smaller than Ss values commonly applied including laboratory testing of cores, aquifer pump testing and numerical groundwater modelling.&#160;Results confirm that Ss is overestimated by assuming incompressible grains, particularly for consolidated rocks. It was also evident that Ss that commonly assumes uniaxial conditions underestimate Ss that accounts for areal or volumetric conditions. &#160;Further research is required to ensure that Ss is not underestimated by assuming instantaneous pore pressure response to strains, particularly in low permeability strata. However, in low permeability strata Ss could also be overestimated if based on total porosity (or moisture content) rather than a smaller free water content, due to water adsorbed by clay minerals. Further evaluation is also required for influences on Ss from monitoring bore construction (ie. screen and casing or grouting), and Ss derived from tidal stresses (undrained or constant mass conditions) that could underestimate Ss applicable to groundwater pumping (drained or changing mass conditions). In summary, poroelastic effects that are often neglected in groundwater studies are clearly important for quantifying water flow and storage in strata with changing hydraulic stress and loading conditions.&#160;

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