Effect of hydraulic gradient on the permeability characteristics of foam-conditioned sand for mechanized tunnelling

2020 ◽  
Vol 99 ◽  
pp. 103377 ◽  
Author(s):  
Qinxin Hu ◽  
Shuying Wang ◽  
Tongming Qu ◽  
Tao Xu ◽  
Shuo Huang ◽  
...  
Keyword(s):  
Hydraulic Gradient ◽  
Permeability Characteristics ◽  
Mechanized Tunnelling

scholarly journals Permeability Characteristics of Tailings considering Chemical and Physical Clogging in Lixi Tailings Dam, China

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Zengguang Xu ◽  
Xuemin Yang ◽  
Junrui Chai ◽  
Yuan Qin ◽  
Yanlong Li
Keyword(s):  
Permeability Coefficient ◽  
Solution Concentration ◽  
Hydraulic Gradient ◽  
Small Concentration ◽  
Column Experiments ◽  
Tailings Dam ◽  
Concentration Gradients ◽  
Permeability Characteristics ◽  
Average Flow Velocity ◽  
Physical And Chemical

Chemical and physical clogging frequently occur in tailings dam. The clogging seriously influences the safety of tailings dam. This paper conducts several column experiments to analyse the physical and chemical clogging of the Lixi tailings dam in China. The experiment results of chemical clogging show that average flow velocity and permeability decrease by approximately 50% to 60%. The experiment results of physical clogging show that these values decrease by approximately 50% to 70%. For physical clogging, a higher hydraulic gradient could result in a larger extent of decrease in the permeability coefficient. The permeability did not decrease when the hydraulic gradient was equal to 0.125. The results of chemical clogging column experiments show that ferrous ion solution concentration is disproportional to the permeability coefficient. This scenario can be attributed to the extremely small concentration gradients.

scholarly journals Effect of bentonite slurry on the function of foam for changing the permeability characteristics of sand under high hydraulic gradients

2021 ◽  
Author(s):  
Fanlin Ling ◽  
Shuying Wang ◽  
Qinxin Hu ◽  
Shuo Huang ◽  
Zhiyao Feng
Keyword(s):  
Permeability Coefficient ◽  
Fine Particles ◽  
Initial Permeability ◽  
Hydraulic Gradient ◽  
Screw Conveyor ◽  
Pressure Balance ◽  
Permeability Characteristics ◽  
Bentonite Slurry ◽  
Hydraulic Gradients ◽  
Injection Ratio

During earth pressure balance (EPB) shield tunnelling in sandy ground, not only foam but also other conditioning agents need to be injected to reduce the permeability of muck and avoid water spewing out of the screw conveyor. Permeability tests were carried out to study the permeability characteristics of conditioned sand under high hydraulic gradients. A low bentonite slurry injection ratio (BIR) enhanced the workability of foam-conditioned sand. As the hydraulic gradient increased, the initial permeability coefficient of conditioned sand increased, and the initial stable period became shorter or disappeared. The BIR had a more significant effect on the permeability of conditioned sand than the foam injection ratio (FIR), and this effect gradually weakened as the hydraulic gradient increased. The initial permeability coefficient of the foam-bentonite slurry-conditioned sand decreased by approximately an order of magnitude compared with that of the foam-conditioned sand. With the addition of bentonite slurry, suitable sand conditioning can accept a higher water content (w) and lower FIR, resulting in suitable ranges of w and FIR that are more flexible. Finally, the mechanism of stabilizing foam under the action of bentonite slurry was discussed by considering the interaction between foam bubbles and fine particles.

Physical Properties of Isolated Perfused Renal Tubular Basement Membranes

1971 ◽  
Vol 29 ◽  
pp. 390-391
Author(s):  
Jared Grantham ◽  
Larry Welling
Keyword(s):  
Basement Membrane ◽  
Basement Membranes ◽  
Transport Mechanisms ◽  
Permeability Characteristics ◽  
Peritubular Capillaries ◽  
Strategic Location ◽  
Tubular Lumen ◽  
Glomerular Filtrate ◽  
Urine Formation ◽  
Renal Tubular

In the course of urine formation in mammalian kidneys over 90% of the glomerular filtrate moves from the tubular lumen into the peritubular capillaries by both active and passive transport mechanisms. In all of the morphologically distinct segments of the renal tubule, e.g. proximal tubule, loop of Henle and distal nephron, the tubular absorbate passes through a basement membrane which rests against the basilar surface of the epithelial cells. The basement membrane is in a strategic location to affect the geometry of the tubules and to influence the movement of tubular absorbate into the renal interstitium. In the present studies we have determined directly some of the mechanical and permeability characteristics of tubular basement membranes.

MGP NAPL management using hydraulic gradient modification

2006 ◽  
Vol 14 (2) ◽  
pp. 639-644
Author(s):  
G.M. Thomas ◽  
J.F. Morgan ◽  
M.J. Gefell ◽  
J. Shi
Keyword(s):  
Hydraulic Gradient

Influence of Pumps on Salinity of a Coastal Aquifer with Legal Protection (A Zone in the North of Isla Cristina, Huelva, Spain)

1991 ◽  
Vol 24 (11) ◽  
pp. 251-260 ◽  
Author(s):  
A. González ◽  
E. Romero
Keyword(s):  
Coastal Aquifer ◽  
Salt Water ◽  
Legal Protection ◽  
Hydraulic Gradient ◽  
Water Mixture ◽  
Residual Flow ◽  
Legal Requirements ◽  
The North ◽  
North Side ◽  
Rational Distribution

In this article we show that the legal measures for protection of aquifers are not enough to lessen the pumping if the users are not associated and determined to have a rational distribution of water. The expansive agriculture on the North side of Isla Cristina (Huelva, Spain), based on citrus and strawberry growing, uses high volumes of groundwater that comes from a tertiary age detritic coastal aquifer with a significant lack of resources. This causes a decrease of the residual flow to the sea, deep pumpcones, and an inversion of the hydraulic gradient, which initiates the progressive salinization of the aquifer northwards, in the sense that the fresh-salt water mixture zone is moving. The problem is worsening because the number of uncontrolled pump-works in the areais increasing. This problem could be alleviated if a Users Community for the whole aquifer were created, itself to watch over the fulfilment of the legal requirements and to regulate the water extractions.

scholarly journals Impacts of Consolidation Time on the Critical Hydraulic Gradient of Newly Deposited Silty Seabed in the Yellow River Delta

2021 ◽  
Vol 9 (3) ◽  
pp. 270
Author(s):  
Meiyun Tang ◽  
Yonggang Jia ◽  
Shaotong Zhang ◽  
Chenxi Wang ◽  
Hanlu Liu
Keyword(s):  
Yellow River ◽  
Yellow River Delta ◽  
Hydraulic Gradient ◽  
River Delta ◽  
Theoretical Formula ◽  
The Yellow River ◽  
The Yellow River Delta ◽  
Critical Hydraulic Gradient ◽  
Seepage Flows ◽  
The Yrd

The silty seabed in the Yellow River Delta (YRD) is exposed to deposition, liquefaction, and reconsolidation repeatedly, during which seepage flows are crucial to the seabed strength. In extreme cases, seepage flows could cause seepage failure (SF) in the seabed, endangering the offshore structures. A critical condition exists for the occurrence of SF, i.e., the critical hydraulic gradient (icr). Compared with cohesionless sands, the icr of cohesive sediments is more complex, and no universal evaluation theory is available yet. The present work first improved a self-designed annular flume to avoid SF along the sidewall, then simulated the SF process of the seabed with different consolidation times in order to explore the icr of newly deposited silty seabed in the YRD. It is found that the theoretical formula for icr of cohesionless soil grossly underestimated the icr of cohesive soil. The icr range of silty seabed in the YRD was 8–16, which was significantly affected by the cohesion and was inversely proportional to the seabed fluidization degree. SF could “pump” the sediments vertically from the interior of the seabed with a contribution to sediment resuspension of up to 93.2–96.8%. The higher the consolidation degree, the smaller the contribution will be.

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