Discussion on Dams on Sand Foundations

Price, W. G.; Potter, Alexander; Thomson, T. Kennard; Smith, George E.; Hazen, Allen; Beardsley, Ron

doi:10.1061/taceat.0002320

Cited by 16 publications

(10 citation statements)

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“…These features (the particle size decreases gradually from coarse to fine from apex to apron) reflect the facies architecture developed during their evolution and formed due to the change of hydrodynamic conditions [17][18][19]. As observed previously, the particle size of fans normally reflects the permeability of the sediment, and many empirical formulas have been founded based on the relationship between particle size and K [20,21]. The coarser particle size, the larger the K. For example, K of the alluvial fan aquifer in the northwest of the Hetao basin decreases from 2.0 m/d along the mountain front to 0.2 m/d in the downdip region [22].…”

Section: Introductionmentioning

confidence: 67%

Effects of Decaying Hydraulic Conductivity on the Groundwater Flow Processes in a Managed Aquifer Recharge Area in an Alluvial Fan

Zhang

Chang

et al. 2021

Water

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Groundwater artificial recharge and medium characteristics represent the major factors in controlling the groundwater flow processes in managed aquifer recharge areas. According to the depositional features of alluvial fans, an analogous homogeneous phreatic sand tank aquifer and the corresponding inhomogeneous scale numerical models were established to investigate the groundwater flow under the combined influence of artificial recharge (human activities) and decaying hydraulic conductivity (medium characteristics). In this study, groundwater flow through a managed aquifer recharge area in an alluvial fan was analyzed under the conditions of decaying hydraulic conductivity (K) with depth or length from apex to apron. The results showed that groundwater flow processes induced by artificial recharge were significantly controlled by the increasing decay exponents of K. The decaying K with depth or length in alluvial fan areas expanded the degree of influence of artificial recharge on groundwater flow. With the increase of decay exponents, the flow directions gradually changed from a horizontal to vertical direction. Groundwater age and spatial variability could also be increased by the increasing decay exponents. The residence time distributions (RTDs) of ambient groundwater and artificially recharged water exhibited logarithmic, exponential, and power law behavior. Penetration depth and travel times of ambient groundwater flow could be affected by artificial recharge and decay exponents. Furthermore, with the increase of decay exponents, the thickness of the artificially recharged water lens and travel times of artificially recharged water were increased. These findings have important implications for the performance of managed aquifer recharge in alluvial fan areas as well as the importance of considering the gradual decrease of K with depth and length.

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Section: Introductionmentioning

confidence: 67%

Effects of Decaying Hydraulic Conductivity on the Groundwater Flow Processes in a Managed Aquifer Recharge Area in an Alluvial Fan

Zhang

Chang

et al. 2021

Water

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“…The liquefaction threshold suggested by Turner and Nielsen (1997) (Equation 1) is based on the concept of critical fluid velocity driven by a pressure gradient according to Darcy's law (Holtz & Kovacs, 1981). The hydraulic conductivity for this calculation was based on the Hazen equation

\left(K=0.01{D}_{10}^{2}\right)

, using a D 10 of 0.17 mm (Hazen, 1911). According to the Turner and Nielsen threshold, no momentary liquefaction events were recorded between sensors P77a‐b or P77b‐c during the shown time period (Figure 8).…”

Section: Resultsmentioning

confidence: 99%

Beach and Dune Subsurface Hydrodynamics and Their Influence on the Formation of Dune Scarps

Bond,

Wengrove,

Puleo

et al. 2023

JGR Earth Surface

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Erosive beach scarps influence beach vulnerability, yet their formation remains challenging to predict. In this study, a 1:2.5 scale laboratory experiment was used to study the subsurface hydrodynamics of a beach dune during an erosive event. Pressure and moisture sensors buried within the dune were used both to monitor the water table and to examine vertical pressure gradients in the upper 0.3 m of sand as the slope of the upper beach developed into a scarp. Concurrently, a line‐scan lidar tracked swash bores and monitored erosion and accretion patterns along a single cross‐shore transect throughout the experiment. As wave conditions intensified, a discontinuity in the slope of the dune formed; the discontinuity grew steeper and progressed landward at the same rate as the R2% runup extent until it was a fully formed scarp with a vertical face. Within the upper 0.15 m of the partially saturated sand, upward pore pressure gradients were detected during backwash, influencing the effective weight of sand and potentially contributing to beachface erosion. The magnitude and frequency of the upward pressure gradients increased with deeper swash depths and with frequency of wave interaction, and decreased with depth into the sand. A simple conceptual model for scarp formation is proposed that incorporates observations of upward‐directed pressure gradients from this study while providing a reference for future studies seeking to integrate additional swash zone sediment transport processes that may impact scarp development.

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“…The effective porosity ( n e [−]) of the sand was measured using the imbibition method (Collins, 1961), arriving at an average value of 0.38. The freshwater hydraulic conductivity of the sand, K , was obtained through Darcy column testing and grain‐size analysis based on the empirical equation proposed by Hazen (1911). Darcy column tests produced K = 1,362 ± 68 m/d (based on repeated tests), while Hazen's (1911) equation provided K = 1,286 m/d, with a possible range of 1,183 to1394 m/d, considering reasonable variability in input parameters (i.e., ±0.05 mm for d 10 ) and 1.0 for the Hazen's empirical coefficient (the sand is well sorted).…”

Section: Methodsmentioning

confidence: 99%

Riparian Freshwater Lens Response to Flooding

Jazayeri

Werner

et al. 2023

Water Resources Research

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In semi-arid and arid environments, freshwater lenses ("lenses" hereafter) overlying otherwise saline groundwater have been encountered within the riparian zones and floodplain aquifers adjacent to freshwater rivers (e.g., Cartwright et al., 2010;; see Figure 1). These lenses are considered critical to the survival of salt-sensitive riparian vegetation and the health of floodplain ecosystems more broadly (Alaghmand et al., 2015;Bauer et al., 2006;Laattoe et al., 2017). In areas where saline groundwater discharge impacts river water quality (e.g., the River Murray, South Australia and the Colorado River, USA), lenses are also thought to buffer saline discharge, improving river water quality (e.g.,

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Discussion on Dams on Sand Foundations

Cited by 16 publications

References 0 publications

Effects of Decaying Hydraulic Conductivity on the Groundwater Flow Processes in a Managed Aquifer Recharge Area in an Alluvial Fan

Effects of Decaying Hydraulic Conductivity on the Groundwater Flow Processes in a Managed Aquifer Recharge Area in an Alluvial Fan

Beach and Dune Subsurface Hydrodynamics and Their Influence on the Formation of Dune Scarps

Riparian Freshwater Lens Response to Flooding

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