Prediction of water flow into rock tunnels: an analytical solution assuming an hydraulic conductivity gradient

Author(s):  
L. Zhang ◽  
J.A. Franklin
2018 ◽  
Vol 49 (3) ◽  
pp. 299-308 ◽  
Author(s):  
Keisuke Inoue ◽  
Hiroomi Nakazato ◽  
Tomijiro Kubota ◽  
Koji Furue ◽  
Hiroshi Yoshisako ◽  
...  

2007 ◽  
Vol 7 (1) ◽  
pp. 59-66 ◽  
Author(s):  
D.E. Rolston

The science of soil-water physics and contaminant transport in porous media began a little more than a century ago. The first equation to quantify the flow of water is attributed to Darcy. The next major development for unsaturated media was made by Buckingham in 1907. Buckingham quantified the energy state of soil water based on the thermodynamic potential energy. Buckingham then introduced the concept of unsaturated hydraulic conductivity, a function of water content. The water flux as the product of the unsaturated hydraulic conductivity and the total potential gradient has become the accepted Buckingham-Darcy law. Two decades later, Richards applied the continuity equation to Buckingham's equation and obtained a general partial differential equation describing water flow in unsaturated soils. For combined water and solute transport, it had been recognized since the latter half of the 19th century that salts and water do not move uniformly. It wasn't until the middle of the 20th century that scientists began to understand the complex processes of diffusion, dispersion, and convection and to develop mathematical formulations for solute transport. Knowledge on water flow and solute transport processes has expanded greatly since the early part of the 20th century to the present.


2016 ◽  
Vol 96 (4) ◽  
pp. 496-503 ◽  
Author(s):  
Nathan E. Derby ◽  
Francis X.M. Casey ◽  
Thomas M. DeSutter

Spills of brine wastewater produced during oil well drilling are occurring more frequently in the Great Plains, resulting in crop production loss on affected soil. Remediation requires removal of salt from the topsoil, which might be accomplished by leaching to subsurface horizons or subsurface drains. A laboratory study determined the effects of brine on saturated hydraulic conductivity (Ks) of four nonimpacted surface soils from western North Dakota, USA. Repacked soil cores were subjected to saturated water flow, followed by one pore volume of brine. Subsequent saturated water flow leached brine from the soil and reduced Ks as much as 97% (0.086–0.003 cm h−1) within 24 h. Effluent total dissolved solids (TDS) approached 250 000 mg L−1 then declined (5 mg L−1) with continued leaching, but Ks did not increase. Removal of soluble salts during leaching increased the relative sodium concentrations (ESP > 55), causing clay swelling/dispersion and reduced Ks. Postbrine gypsum application (11.2 Mg ha−1) to replace exchangeable sodium with calcium did not improve Ks. This evidence suggests that if subsurface drainage is used for reclaiming brine-impacted soils that special attention be given to where dispersion/swelling is occurring, leaching water quality, and closely positioning calcium amendments within the high sodium zones.


2010 ◽  
Vol 37 (3) ◽  
pp. 183 ◽  
Author(s):  
Helen Bramley ◽  
Neil C. Turner ◽  
David W. Turner ◽  
Stephen D. Tyerman

Little is known about water flow across intact root cells and roots in response to hypoxia. Responses may be rapid if regulated by aquaporin activity, but only if water crosses membranes. We measured the transport properties of roots and cortical cells of three important crop species in response to hypoxia (0.05 mol O2 m–3): wheat (Triticum aestivum L.), narrow-leafed lupin (Lupinus angustifolius L.) and yellow lupin (Lupinus luteus L.). Hypoxia influenced solute transport within minutes of exposure as indicated by increases in root pressure (Pr) and decreases in turgor pressure (Pc), but these effects were only significant in lupins. Re-aeration returned Pr to original levels in yellow lupin, but in narrow-leafed lupin, Pr declined to zero or lower values without recovery even when re-aerated. Hypoxia inhibited hydraulic conductivity of root cortical cells (Lpc) in all three species, but only inhibited hydraulic conductivity of roots (Lpr) in wheat, indicating different pathways for radial water flow across lupin and wheat roots. The inhibition of Lpr of wheat depended on the length of the root, and inhibition of Lpc in the endodermis could account for the changes in Lpr. During re-aeration, aquaporin activity increased in wheat roots causing an overshoot in Lpr. The results of this study demonstrate that the roots of these species not only vary in hydraulic properties but also vary in their sensitivity to the same external O2 concentration.


SOIL ◽  
2016 ◽  
Vol 2 (3) ◽  
pp. 421-431 ◽  
Author(s):  
Eléonore Beckers ◽  
Mathieu Pichault ◽  
Wanwisa Pansak ◽  
Aurore Degré ◽  
Sarah Garré

Abstract. Determining soil hydraulic properties is of major concern in various fields of study. Although stony soils are widespread across the globe, most studies deal with gravel-free soils, so that the literature describing the impact of stones on the hydraulic conductivity of a soil is still rather scarce. Most frequently, models characterizing the saturated hydraulic conductivity of stony soils assume that the only effect of rock fragments is to reduce the volume available for water flow, and therefore they predict a decrease in hydraulic conductivity with an increasing stoniness. The objective of this study is to assess the effect of rock fragments on the saturated and unsaturated hydraulic conductivity. This was done by means of laboratory experiments and numerical simulations involving different amounts and types of coarse fragments. We compared our results with values predicted by the aforementioned predictive models. Our study suggests that it might be ill-founded to consider that stones only reduce the volume available for water flow. We pointed out several factors of the saturated hydraulic conductivity of stony soils that are not considered by these models. On the one hand, the shape and the size of inclusions may substantially affect the hydraulic conductivity. On the other hand, laboratory experiments show that an increasing stone content can counteract and even overcome the effect of a reduced volume in some cases: we observed an increase in saturated hydraulic conductivity with volume of inclusions. These differences are mainly important near to saturation. However, comparison of results from predictive models and our experiments in unsaturated conditions shows that models and data agree on a decrease in hydraulic conductivity with stone content, even though the experimental conditions did not allow testing for stone contents higher than 20 %.


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