Undrained Pore Pressure Response Of Sand Under Different Modes Of Cyclic Loading

Pore pressures within saturated subsurface formations respond to stress changes due to loading as well as to changes in pore pressure at the boundaries of the formation. The pore-pressure dynamics within a thick aquitard in response to water table fluctuations and mechanical loading due to soil moisture changes have been simulated using a coupled stress–strain and groundwater flow finite element formulation. This modelling approach isolates the component of pore-pressure response of soil moisture loading from that caused by water table fluctuations, by using a method of superposition. In this manner, the contributions to pore-pressure fluctuations that occur as a result of surface moisture loading (e.g., precipitation, evapotranspiration) can be isolated from the pore-pressure record. The required elastic stress–strain properties of the aquitard were obtained from the measured pore-pressure response to barometric pressure changes. Subsequently, the numerical simulations could be calibrated to the measured response by adjusting only the hydraulic conductivity. This paper highlights the significance of moisture loading effects in pore-pressure observations and describes an efficient technique for obtaining in situ stress–strain and hydraulic properties of near-surface aquitards.

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Pore pressure response of seabed in standing waves and its mechanism

Coastal Engineering ◽

10.1016/j.coastaleng.2014.06.005 ◽

2014 ◽

Vol 91 ◽

pp. 213-219 ◽

Cited By ~ 22

Author(s):

Hu Wang ◽

Hong-jun Liu ◽

Min-sheng Zhang

Keyword(s):

Pore Pressure ◽

Standing Waves ◽

Pressure Response ◽

Pore Pressure Response

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Effects of deviatoric stress on undrained pore pressure response to fault slip

Journal of Geophysical Research Atmospheres ◽

10.1029/97jb01358 ◽

1997 ◽

Vol 102 (B8) ◽

pp. 17943-17950 ◽

Cited By ~ 34

Author(s):

Herbert F. Wang

Keyword(s):

Pore Pressure ◽

Fault Slip ◽

Deviatoric Stress ◽

Pressure Response ◽

Pore Pressure Response

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Experimental study of the hydro-mechanical response of Opalinus Clay – Part 2: Influence of the stress path on the pore pressure response

Engineering Geology ◽

10.1016/j.enggeo.2018.02.011 ◽

2018 ◽

Vol 237 ◽

pp. 92-101 ◽

Cited By ~ 3

Author(s):

Katrin M. Wild ◽

Florian Amann

Keyword(s):

Experimental Study ◽

Pore Pressure ◽

Mechanical Response ◽

Stress Path ◽

Pressure Response ◽

Opalinus Clay ◽

Pore Pressure Response

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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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