scholarly journals Error on the Estimation of Sand Size Parameters When Using Small Diameter Sieves and a Solution

2021 ◽  
Vol 8 ◽  
Author(s):  
Patricia Lopez-Garcia ◽  
Juan J. Muñoz-Perez ◽  
Antonio Contreras ◽  
Juan Vidal ◽  
Bismarck Jigena ◽  
...  
Keyword(s):  
Grain Size ◽  
Small Diameter ◽  
Beach Nourishment ◽  
Average Error ◽  
Manual Method ◽  
Granulometric Analysis ◽  
Mechanical Procedure ◽  
Sand Size

Analyses were carried out to determine the main sand size parameters (median grain size D50 and sorting σ) for beach nourishment purposes using the sieving method aboard a dredger. Due to a lack of space and the need to carry and use the material with ease, the sieves are commonly small (10 cm diameter), and the shaking procedure is usually performed by hand. However, the influence of shaking, either mechanically or manually, has not yet been studied with 10 cm diameter sieves. Therefore, 20 samples were taken from inside the hopper of a trailing suction dredger and sieved both manually and mechanically for 10 min. The results showed that manual sieving yielded higher D50 values than the mechanical procedure. The average error arising from using the manual method was 14%, but it can reach 36.5%. The granulometric analysis carried out for different shaking times has shown that this error is < 5% when at least 20 min of shaking is performed. The mechanical procedure gave always finer sand results. In addition, the overfill ratio calculated for both mechanical and manual results reached differences of up to 48%.

scholarly journals Analysis of Bearing Strength of Post-Tensioning Anchorage Zone with Respect to Relative Bearing Area and Lateral Confinement Design

2021 ◽  
Vol 11 (18) ◽  
pp. 8386
Author(s):  
Jin-Kook Kim ◽  
Jun-Mo Yang
Keyword(s):  
Error Rate ◽  
Small Diameter ◽  
Average Error ◽  
Displacement Curve ◽  
Proportional Limit ◽  
Lateral Confinement ◽  
Bearing Strength ◽  
Bearing Plate ◽  
Load Displacement ◽  
Post Tensioning

This study aimed to evaluate the bearing strength of the post-tensioning anchorage zone with respect to the relative bearing area and lateral confinement design of spiral and stirrup rebars. Eleven specimens were fabricated and tested to fracture in accordance with EAD 160004-00-0301. Load-displacement curves and fracture modes were analyzed. Then, the conventional design equation for the bearing strength and previous findings on the relative bearing area was re-investigated in comparison with the test results. From the test, the representative findings are as follows: (1) A specimen with relatively small size and less lateral reinforcement is more likely to be affected by the wedge action of the anchorage device; however, a larger specimen is affected by both concrete crushing and/or spalling; (2) The behavior of the anchorage zone is markedly affected by the local behavior near the anchorage bearing plate, and the sectional efficiency is mostly determined by A/Ag; (3) For specimens with A/Ag = 9.52, the proportional limit of the load-displacement curve is determined by the yield of spiral rebar or fracture of the bearing plate, but the later part of the curve is determined by lateral confinement; (4) The maximum A/Ag that could produce 100% sectional efficiency is about 2.0 for the anchorage bearing plate used in the test; (5) For a fully confined specimen with a small-diameter spiral for minimum anchorage spacing, the stirrup rebar design mainly influences crack occurrence and patterns when the size of the specimen is equal to the minimum anchorage spacing; however, the area of the load-displacement curve after the proportional limit as well as crack occurrence and patterns are also influenced by stirrup rebar design when A/Ag is relatively large; (6) Finally, a revised design model is proposed to effectively estimate the ultimate bearing strength of the post-tensioning anchorage zone without respect to A/Ag. From the comparison of the design equations, it was concluded that the proposed equation provides a more reliable prediction with a 14.0% average error rate and 5.7% standard deviation of error rate.

scholarly journals Evaluation of Effect of Beach Nourishment Considering Grain Size on Chigasaki Coast

2007 ◽  
Vol 54 ◽  
pp. 631-635
Author(s):  
Takaaki UDA ◽  
Genji AOSHIMA ◽  
Takumi YAMANO ◽  
Atsushi YOSHIOKA ◽  
Kou FURUIKE ◽  
...  
Keyword(s):  
Grain Size ◽  
Beach Nourishment

scholarly journals FIELD EXPERIMENT ON BEACH NOURISHMENT USING GRAVEL AT JINKOJI COAST

2011 ◽  
Vol 1 (32) ◽  
pp. 100 ◽  
Author(s):  
Takayuki Kumada ◽  
Takaaki Uda ◽  
Takeo Matsu-ura ◽  
Michio Sumiya
Keyword(s):  
Grain Size ◽  
Pacific Ocean ◽  
Field Experiment ◽  
Beach Nourishment ◽  
Core Sampling ◽  
The Pacific ◽  
The Pacific Ocean

Beach nourishment using 87,000 m3 of gravel with grain size between 2.5 and 13 mm was experimentally carried out until April 2008 at the Jinkoji coast, which faces the Pacific Ocean and is surrounded by artificial headlands. Monitoring surveys, a boring test and core sampling on the beach were carried out to investigate the mechanism of the formation of gravel layers and their effect on protecting the foot of the seawall. It was found that the nourishment gravel was deposited with a slope of 1/8 at the foot of the seawall, thus providing some protection to the seawall, and that the nourishment gravel was stably deposited without offshore discharge.

Sand size variability inside the hopper of a trailing suction dredger for beach nourishment purposes

2019 ◽  
Vol 39 (6) ◽  
pp. 513-520
Author(s):  
P. Poullet ◽  
J.J. Muñoz-Perez ◽  
P. Lopez ◽  
S. García-Lopez ◽  
R. Martell ◽  
...  
Keyword(s):  
Beach Nourishment ◽  
Size Variability ◽  
Sand Size

The effect of filter cake deposition on the hydraulic conductivity of boreholes

2021 ◽  
Author(s):  
Rein Nijhof ◽  
Jan van Lopik ◽  
Martin Bloemendal
Keyword(s):  
Grain Size ◽  
Hydraulic Conductivity ◽  
Filter Cake ◽  
Drilling Fluid ◽  
Short Circuit ◽  
Small Diameter ◽  
Unconsolidated Sediments ◽  
Direct Result ◽  
Sealing Capacity ◽  
Cake Formation

<p>Efficient construction and operation of borehole heat exchangers (BHEs) are essential in its contribution to the energy transition. In practice, implementation of BHE at larger scale requires low construction costs and high production rates. This requires small diameter drillings to reduce drilling and backfilling material costs, in which achieving a proper backfilling is a challenge. At present, there is an urgent need to improve the available techniques with more effectively and efficiently backfill methods for BHEs. In current Dutch practice, sealing (to prevent short-circuit flow between penetrated aquifers) is achieved by using either clay or grouts as backfilling materials, both have their pro’s and con’s. In optimisation of applying backfilling materials and methods, the filter cake, formed during the drilling procedure, also has a sealing capacity and is overlooked in addressing the sealing of the borehole.</p><p> </p><p>In this study the effect of filter cake formation on sealing capacity in unconsolidated sediments is quantified. Filter cake formation in unconsolidated porous formations (aquifers) is a complex process, which is affected by pressure differences between the borehole and the aquifer, aquifer characteristics (e.g. grain size distribution, porosity and permeability) and drilling mud/fluid properties.</p><p>A laboratory configuration is designed to stimulate different scenarios during the construction of a BHE. Consequently, the effectiveness, in terms of hydraulic conductivity, of the formed filter cake is determined by falling head tests.</p><p>Uniform aquifers with the smallest grain size tested (D50 = 0.22 mm) show a two order of magnitude reduction in hydraulic conductivity, as a direct result of filter cake formation. In contrast, filter cake formation is absent in uniform more coarse sands (D50 ≥ 0.65 mm). This demonstrates that filter cake deposition is highly variable with the grain size of the aquifer penetrated. Moreover, the experiments performed indicate that the deposition of a filter cake is not limited by additive concentrations in the drilling fluid or the duration of drilling fluid exposure to the formation.</p><p>This preliminary study creates the foundation for further research, since the experiments demonstrate the potential of filter cakes to significantly contribute to the sealing capacity within a borehole.</p>

Analysis of Variance about the Sadiment Size in Jiuyuangou and Tuwei River Watershed’s Silt Dam

2014 ◽  
Vol 1010-1012 ◽  
pp. 1140-1144
Author(s):  
Li Li ◽  
Wei Ying Sun ◽  
Qi He ◽  
Xin Xin Hou
Keyword(s):  
Grain Size ◽  
Analysis Of Variance ◽  
Coarse Sand ◽  
Sediment Grain Size ◽  
Separation Effect ◽  
River Watershed ◽  
Drilling Hole ◽  
Reduction Effect ◽  
Sand Size

Analysising twenty-one silt dams in Jiuyuangou watershed and thirty-six silt dams in Tuwei River Watershed drilling hole sampling’s data, Jiuyuan gou Watershed’s silt dams in coarse sand size mainly concentrated in the 0.05mm,Tuwei River Watershed’s silt dams in coarse sand size mainly concentrated in the 0.05mm~0.10mm,The dam upstream sand size is generally larger than the dam downstream, sorting depends on sediment dam on the dam upstream tosand size, dam upstream sediment grain size is coarse separation effect is better, warping dam and reduction effect is more obvious.

scholarly journals Evaluation of Effect of Beach Nourishment using Fine and Coarse Sand by Contour-line-change Model Considering Change in Grain Size

2007 ◽  
Vol 54 ◽  
pp. 641-645
Author(s):  
Takaaki UDA ◽  
Takayoshi YOSHIZOE ◽  
Yasushi MACHII ◽  
Takeshi YAMAMOTO ◽  
Kou FURUIKE ◽  
...  
Keyword(s):  
Grain Size ◽  
Beach Nourishment ◽  
Coarse Sand ◽  
Contour Line ◽  
Change Model

scholarly journals POSSIBILITY OF OFFSHORE DISCHARGE OF NOURISHMENT SAND IN TERMS OF SAND VOLUME AND GRAIN SIZE COMPOSITION

2018 ◽  
pp. 47
Author(s):  
Toshinori Ishikawa ◽  
Takaaki Uda ◽  
Toshiro San-nami ◽  
Jun-ichi Hosokawa ◽  
Tetsuyuki Tako
Keyword(s):  
Grain Size ◽  
Survey Data ◽  
River Mouth ◽  
Size Composition ◽  
Beach Nourishment ◽  
Fine Sediment ◽  
Sagami Bay ◽  
Grain Size Composition ◽  
Fine Material

On the Shonan coast facing Sagami Bay, part of the nourishment sand was considered to be transported offshore, devaluing the effect of beach nourishment. Beach changes after the beach nourishment were investigated using the Narrow Multi-Beam survey data, which have been collected since 2002. Analysis of the sand volume and grain size composition in the subareas showed that the effect of the beach nourishment on the deposition of fine sediment in the offshore zone was negligible, and that the fine material in the offshore zone was mainly brought from the erosion of the river mouth terrace.

scholarly journals Benthic microalgae under the influence of beach nourishment in the Gulf of Odessa (the Black Sea)

2013 ◽  
Vol 19 (2) ◽  
pp. 120-128 ◽  
Author(s):  
Anastasiya Snigirova
Keyword(s):  
Grain Size ◽  
Black Sea ◽  
Beach Nourishment ◽  
Fine Sand ◽  
Benthic Microalgae ◽  
The Black Sea ◽  
Shore Protection ◽  
The North ◽  
Sand Nourishment ◽  
Sand Grain Size

Abstract Snigirova A., 2013: Benthic microalgae under the influence of beach nourishment in the Gulf of Odessa (the Black Sea) [Paplūdimių papildymo smėliu poveikis bentosinių dumblių bendrijoms Odesos įlankoje (Juodoji jūra)]. - Bot. Lith., 19(2): 120-128. The coast of the Gulf of Odessa (Odessa Bay) in the north-western part of the Black Sea is exposed to abrasive processes, which lead to its destruction. One of the measures for landslides stabilization is sand nourishment, which was held on the beach of the gulf in October 2007. As a result of shore protection works, the sand grain size on the beaches of Odessa has decreased by 53% on average. The influence of sand grain size on the abundance and biomass of benthic microalgae was investigated. Benthic microalgae were presented mostly by Bacillariophyta and Dinophyta. Other groups of Chlorophyta, Cyanophyta and Cryptophyta were less presented. The abundance and biomass of algae increased threefold and fourfold, accordingly, as a result of sand nourishment. Significant influence of fine sand particles on the biomass and abundance of microalgae was revealed. However, the structure of algological assemblages changed because of the increase of mixotrophic groups of algae contribution.

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