Backward erosion testing : Magnolia Levee

Using a confined flume device, an experimental study investigated the critical horizontal gradient of soils obtained from a site identified as potentially vulnerable to backward erosion piping (BEP). Tests were conducted on glacial outwash material obtained from a sand and gravel quarry in the vicinity of Magnolia Levee in the community of Magnolia, OH. The two bulk samples collected from the quarry had similar grain-size distributions, grain roundness, and depositional environments as the foundation materials beneath the levee. Samples were prepared at various densities and subjected to gradual increases of flow in a wooden flume with an acrylic top until BEP was observed. The critical average horizontal gradient ranged from 0.21 to 0.30 for a bulk sample with a coefficient of uniformity of 1.6, while tests conducted on a bulk sample with a coefficient of uniformity of 2.5 yielded critical average horizontal gradients of 0.31 to 0.36. The critical average gradients measured during these tests compared favorably to values in the literature after applying adjustments according to Schmertmann’s method.

Enhancing the Flexural Strength of Concrete using Recycled Iron and Steel Slag Aggregate

Concrete is strong in compression but weak in tension hence, considerable effort is required to improve concrete’s tensile strength by the use of pre-stressed concrete and addition of admixtures or additives. In this study, the use of recycled iron and steel slag (RISS) aggregate to improve the tensile strength of concrete was considered. The paper assessed the mineralogical composition of RISS and granite aggregates, and gradation. It also determines the effects of RISS aggregate on the flexural strength of concrete beams of 150 × 150 × 600 mm containing 0, 10, 20, 40 and 60% RISS aggregate replacement in mix ratios 1:1½:3, 1:2:4 and 1:3:6 with water cement ratios 0.65,0.60 and 0.55 respectively. Diffractograph of RISS and granite aggregate showed that RISS contains Magnetite, Ilmenite and Quartz, while granite contains Quartz, Annite, Microcline and Albite as the predominant minerals. The coefficient of uniformity and concavity of RISS and granite aggregate for maximum aggregate size of 37.5 mm are 4.35 and 1.33; and 4.64 and 1.76 respectively. Both aggregates contain quartz as the predominant mineral and are well graded. The result of the Flexural strength at 28 days curing is within 0.135 – 0.250 MPa specified byBS8500 – 2:2015. Flexural strength of concrete beams cast with RISS aggregate is relatively higher than concrete cast with granite aggregate. Flexural strength, a measure of tensile strength of concrete is improved as percentage RISS aggregate increased.

The effectiveness of dayligting through the toplighting design in large-volume building models

The utilization of daylighting as an effort to reduce the usage of building energy needs to be optimized. This is because, low-rise buildings with large volumes require specific strategies for proper light distribution throughout the space. Hence, this study aims to explore and compare the effectiveness of daylighting in the openings design of skylight, roof monitor, and sawtooth in large-volume buildings in Bandung. The effectiveness is assessed by examining lighting performance based on distribution patterns, the value of Daylight Factor (DF), and the Coefficient of Uniformity (CU). Experimental research method with simulation program known as Velux Daylight Visualizer 3.0 is used to present and analyze the lighting data. The results showed that the type, position (openings' height and distance), as well as the opening direction affected the distribution patterns and daylighting performance. Based on the simulation, the skylight opening is the most effective in meeting the standard value of Daylight Factor (> 2%) and Coefficient of Uniformity (CU min. 0.3 and DF min. 0.8%). Thus, space and openings model with a percentage roof area of 16.3% in the simulation can be used as a reference for large-volume buildings because, it meets the requirements of Daylight Factor value and sufficient Coefficient of Uniformity.

Avaliando o coeficiente de uniformidade de um sistema central de pivô / Evaluation of the coefficient of uniformity of a central pivot system

En las zonas áridas y semi-áridas del mundo, la producción agrícola depende de un riego eficiente, siendo el objetivo garantizar las mejores condiciones de utilización del agua y el óptimo aprovechamiento por parte de la planta. Cuando los sistemas de riego se utilizan para aplicar fertilizantes y pesticidas, la uniformidad de la aplicación se vuelve aún más crítica por lo que es importante que los propietarios y operadores de los sistemas de riego, en nuestro caso, pivote central, comprueben periódicamente la uniformidad de sus sistemas. La uniformidad de riego depende del grado de qué agua se aplica de manera uniforme en diferentes áreas del campo. Para su determinación se pueden utilizar varios métodos/fórmulas. Para un sistema de riego por pivote central, el método más habitual es el de Heerman y Hein que se basa en la norma UNE-EN ISO 1154. En la evaluación el valor obtenido fue de 82.43%, que está en el rango que permite considerarlo como razonable, pero que requiere ser monitoreado constantemente.

Evaluation of erosion characteristics of soils using the pinhole test

This paper investigates the erosion characteristics of soils using the pinhole test. The tests were conducted with two undisturbed clay samples and five disturbed sandy soil samples. Based on the pinhole test results, a process to analyze the critical shear stress and erosion rate was proposed. The result indicates that the particle size distribution and coefficient of uniformity of soils are significant factors that affect the erosion characteristics of the soil. Samples with a grain size ranging from 0.2 to 0.6 mm is most susceptible to soil erosion. The erosion coefficients can be used to distinguish between the low erodible soils (ND3 and ND4) and high erodible ones (D1 and D2). Furthermore, it is interesting to note that the critical shear stress might be used as an identification parameter for erosion characteristics of the soil: τc > 3.5 Pa (ND3), 3.0 Pa < τc < 3.5 Pa (D2), and τc < 3.0 Pa (D1).

Impact of the Intermittency Movement of Center Pivots on Irrigation Uniformity

A computer model was developed to simulate the varying depths of water applied to the ground due to the intermittent movements of a typical center pivot. The stop–go model inputs include the sprinkler application depth, the sprinkler pattern, that pattern’s wetted radius, the center pivot’s % timer setting, the move cycle time, and the end tower maximum travel speed. The model outputs were the depth of application in the pivot’s movement direction, the distribution uniformity (DU), and the coefficient of uniformity (CU). The results revealed that the pivot circular application uniformity is mostly a function of the move distance as a percent of the sprinklers’ wetted radius. This, in turn, is a function of the percent timer setting, the cycle time, and the end tower travel speed. Due to this, the high-speed center pivots had corresponding lower application uniformities compared to low-speed machines, and sprinklers with larger wetted radii resulted in better uniformity. Shortening the cycle time also resulted in higher uniformity coefficients. Based on these results, it is recommended that the run time be set based on the pivot end-tower’s travel speed and sprinkler wetted radius, such that the end tower move distance is equivalent to the sprinkler wetted radius. This will reduce wear to the tower motors due to the on–off cycling, especially for slow travel settings and for sprinklers with larger wetted radii. The ponding depths at different percent of the move distance, for the potential runoff, were estimated, which were set to be equivalent to the wetted radius.

Influence of Crushed Rock Properties on the Productivity of a Hydraulic Excavator

Among many factors that influence an excavator’s performance and productivity, the volume of the bucket load and duration of the excavator working cycle are crucial. In this paper, both factors were investigated, including the granulometric composition of the excavated material. The volume of material in the bucket was determined by photogrammetric analysis while the excavator cycle time was measured by analysis of video recordings captured by a digital video camera during the excavator operation. Interconnections between the angle of repose, slewing angle, particle size distribution of material, and their effects on hydraulic excavator productivity were analyzed. It was found that a larger number of fine particles in granular materials with a higher coefficient of uniformity resulted in an increase in the volume of the bucket load. Correlation analysis revealed significant interconnection between the bucket fill factor and swell factor. It was also found that calculation of the production rate according to ISO (International Organization for Standardization) standards was more accurate for materials with a higher angle of repose while the CECE (Committee for European Construction Equipment) standard was more appropriate for materials with lower angles of repose.

Performance Optimization of a Newly Designed Dynamic Fluidic Sprinkler

HighlightsThe results confirmed that the optimal combination of structural parameters was achieved with the factor combination of 25 mm length of the tube, 150 kPa pressure, 3 mm diameter of the tube, and 5 mm nozzle diameter.The influencing factors in decreasing order of importance were: working pressure, length of the tube, and nozzle diameter for coefficient of uniformity, and nozzle diameter working pressure and diameter of the tube for range.Droplet velocities from test 7 ranged between 0 and 6.0 m/s, while that from test 2 was slightly larger, ranging from 0 to 6.7 m/s under low-pressure conditions.ABSTRACT: To select the appropriate combination of the factors for the dynamic fluidic sprinkler, hydraulic performance tests at low pressure were conducted. The main structural parameters in this study were the length of the tube (L), pressure (H), the diameter of the tube (M), nozzle diameter (N), they are represented by factors A, B, C, and D, respectively. An orthogonal array with four factors and three levels was selected, and the direct analysis technique was used to analyze the test data. The droplets and velocities data of the sprinkler were obtained by a Thies Clima Laser Precipitation Monitor. MATLAB R20014a software was used to calculate the simulated coefficient of uniformity (CU). The results showed that the optimum values of the structural parameters were: the length of the tube (25 mm), the working pressure (150 kPa), the diameter of the tube (3 mm), and the nozzle diameter (5 mm). The factors affecting coefficient of uniformity and range, in decreasing order of importance were nozzle diameter, pressure, length of the tube, and the diameter of the tube. The highest coefficient of uniformity obtained was 91% when the length of the tube was 25 mm. Droplet sizes decreased with the increase of pressure. Droplet size ranging from 0.1 to 4 mm was obtained under test 7 with a mean droplet size of 0.38 mm. The study can give a reference to the operation for saving water in sprinkler irrigated fields. Keywords: Droplet, Dynamic fluidic sprinkler, Orthogonal test, Structural parameter, Uniformity, Velocity.

Effect of the particle-size distribution variability on the SWCC predictions of coarse-grained materials

The particle-size distribution (PSD) is the key information required by several models for prediction of the soil-water characteristic curve (SWCC). The performance of these models has been extensively investigated in the literature; however, limited studies have been undertaken with respect to the uncertainty associated with the SWCC predictions resulting from the variability in the PSD. This study aims to investigate the influence of the variability of the PSD in the prediction of SWCCs using five different models applied to three different glass beads (GBs). The PSD curves were determined by sieve analysis, laser diffraction, and image analysis. The various testing procedures were statistically evaluated to understand the influence of variability of the PSD in terms of the coefficient of uniformity (CU) and de size of particles corresponding to 10% in the PSD (D10). For each prediction model, a combination of PSD curves and their coefficient of variation were used to estimate the SWCCs. Both the CU and D10 proved to have a strong relationship with the predicted SWCCs. The CU appears to influence more the residual suction prediction while the D10 seems to have a major role for the transition and residual stages.

Analytic Representation of the Optimal Flow for Gravity Irrigation

The aim of this study is the deduction of an analytic representation of the optimal irrigation flow depending on the border length, hydrodynamic properties, and soil moisture constants, with high values of the coefficient of uniformity. In order not to be limited to the simplified models, the linear relationship of the numerical simulation with the hydrodynamic model, formed by the coupled equations of Barré de Saint-Venant and Richards, was established. Sample records for 10 soil types of contrasting texture were used and were applied to three water depths. On the other hand, the analytical representation of the linear relationship using the Parlange theory of infiltration proposed for integrating the differential equation of one-dimensional vertical infiltration was established. The obtained formula for calculating the optimal unitary discharge is a function of the border strip length, the net depth, the characteristic infiltration parameters (capillary forces, sorptivity, and gravitational forces), the saturated hydraulic conductivity, and a shape parameter of the hydrodynamic characteristics. The good accordance between the numerical and analytical results allows us to recommend the formula for the design of gravity irrigation.