Preliminary stabilisation of stormwater biofilters and loss of filter material

2016 ◽  
Vol 74 (4) ◽  
pp. 787-795 ◽  
Author(s):  
D. N. Subramaniam ◽  
P. B. Mather
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Tap Water ◽  
Filter Material ◽  
Internal Diameter ◽  
Significant Drop ◽  
Wetting And Drying ◽  
Stabilisation Period ◽  
Sand Particles ◽  
Filter Layer

Stabilisation affects performance of stormwater biofilters operating under intermittent wetting and drying, mainly due to wash-off of filter material. Understanding the dynamics of solids wash-off is crucial in designing stormwater biofilters. The current study analysed the dynamics of solids wash-off in stormwater biofilters and quantified the loss of solids from the filter. Four Perspex™ bioretention columns (94 mm internal diameter) were fabricated with a filter layer that contained 8% organic material and were fed with tap water with different numbers of antecedent dry days (0–40 day) at 100 mL/min. Samples were collected from the outflow and tested for particle size distribution and total solids and turbidity. Solids of particle size less than 50 microns were washed off from the filter during the stabilisation period, indicating that no sand particles were washed off. The very first event after commissioning the filter resulted in the highest wash-off of solids (approximately 75 g of fines) while a significant drop in wash-off followed from the second event. An empirical model fitted to the data showed that preliminary stabilisation of a filter occurs in the first three events, during which almost 25% of fines are lost from the filter.

scholarly journals Weathering-induced deformation of crushed weak rocks and its countermeasure

2019 ◽  
Vol 92 ◽  
pp. 09003
Author(s):  
Andius D. Putra ◽  
Masaya Takahashi ◽  
Mamoru Kikumoto
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Compression Stress ◽  
Test Results ◽  
Compression Tests ◽  
Wetting And Drying ◽  
Weak Rocks ◽  
One Dimensional ◽  
Significant Compression ◽  
Hydraulic Process

Geotechnical issues such as differential settlements have been reported usually in embankments made of materials derived from weak rocks such as mudstones, siltstones, and shales. The primary cause of the issue is a gradual weakening due to weathering. Crushed weak rocks tend to turn into smaller particles under repeated wetting and drying processes. This phenomenon is a mechanical-hydraulic process known as “slaking”. The present paper discusses the deformation of crushed weak rocks due to slaking and its countermeasure. We performed a series of one-dimensional slaking tests on several weak rocks. We first performed one-dimensional compression tests on dried samples, and applied wetting and drying cycles to the samples while keeping the compression stress constant. The test results revealed that particle size distribution of the samples was broadened due to cyclic wetting and drying processes and that significant compression was exhibited. Moreover, we explored possible countermeasures for reducing the slaking-induced deformation and revealed that compacting the soil to a denser state is the most effective way in reducing the slaking-induced deformation of the crushed mudstone.

A procedure for the design of protective filters

2007 ◽  
Vol 44 (4) ◽  
pp. 490-495 ◽  
Author(s):  
G L. Sivakumar Babu ◽  
Amit Srivastava
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Relative Density ◽  
Size Distribution ◽  
Analytical Procedure ◽  
Filter Material ◽  
Seepage Velocity ◽  
Base Soil ◽  
Insight Into

Current procedures for the design of filters to protect the soil from erosion and piping are solely based on particle-size distribution (PSD) curves of the filter medium and base soil. In the present work, an analytical solution is presented in a single derivation for the design of the filter, which takes into account factors like pore size, permeability, and factor of safety against soil boiling conditions. The solution obtained from the proposed analytical procedure provides insight into the role of seepage velocity, relative density of the filter material, and the ratio of filter density to base soil density on the performance of the filter.Key words: filter, erosion, particle-size distribution, permeability, seepage velocity, relative density.

Hydraulic conductivity of saturated granular soils determined using a constriction-based technique

2012 ◽  
Vol 49 (5) ◽  
pp. 607-613 ◽  
Author(s):  
Buddhima Indraratna ◽  
Vo Trong Nguyen ◽  
Cholachat Rujikiatkamjorn
Keyword(s):  
Particle Size ◽  
Hydraulic Conductivity ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Granular Medium ◽  
Laboratory Tests ◽  
Filter Material ◽  
Granular Soils ◽  
Empirical Power ◽  
Semi Empirical

This study presents a new semi-empirical approach for predicting the saturated hydraulic conductivity of noncohesive (granular) soils through a constriction size–based technique. For the same particle-size distribution of a granular filter material, there can be many different void distributions depending on the as-compacted density. Therefore, particle-size distribution is not unique in determining the hydraulic conductivity as proposed in numerous earlier studies. In contrast, the constriction-size distribution is unique for a given as-placed density of the material, and therefore it is a better representation of hydraulic conductivity as proposed in this study. Accordingly, the hydraulic conductivity of a granular medium can be represented by an empirical power function that has been established on the basis of 60 laboratory tests.

Influence of the Sand Particle Shape on Particle Size Distribution Measured by Laser Diffraction Method

2014 ◽  
Vol 28 (2) ◽  
pp. 195-200 ◽  
Author(s):  
Cezary Polakowski ◽  
Agata Sochan ◽  
Andrzej Bieganowski ◽  
Magdalena Ryzak ◽  
Rita Földényi ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Particle Shape ◽  
Diffraction Method ◽  
Laser Diffraction ◽  
Soil Science ◽  
Sand Particle ◽  
Sand Fraction ◽  
Sand Particles

Abstract The aim of this paper was to show how the shape of sand particles affects the results of particle size distribution obtained by the laser diffraction method. On the basis of the results obtained one can conclude: the shape of the investigated particles influences particle size distribution obtained by the laser diffraction method. This phenomenon occurs in the sand fraction, as shown in our investigation. The importance of this effect depends on the type of the measured material and on the aim of the investigations. For most researchers in soil science and sedimentology who investigate sand fractions, this impact can be negligible. Further investigations with other soil and sediment fractions are needed.

MOISTURE TENSION, DIFFUSIVITY, AND CONDUCTIVITY OF A LOAM SOIL DURING WETTING AND DRYING

1965 ◽  
Vol 45 (1) ◽  
pp. 78-86 ◽  
Author(s):  
W. J. Staple
Keyword(s):  
Particle Size ◽  
Soil Moisture ◽  
Particle Size Distribution ◽  
Bulk Density ◽  
Size Distribution ◽  
Packed Columns ◽  
Silt Loam ◽  
Surface Soils ◽  
Wetting And Drying ◽  
Loam Soil

Soil moisture tensions, diffusivities, and conductivities in packed columns of Grenville silt loam during wetting were compared with those during drying. In the moisture range 0.3 to 0.4 cm3/cm3 tensions on wetting were only one third of those on drying. Diffusivities and conductivities on wetting exceeded those on drying in the ratios 5:1 and 10:1 respectively. These data depended on the bulk density and particle size distribution of the soil. The observed wetting to drying ratios of D and K should be representative for fragmented surface soils although lower ratios may occur below plow depth.

scholarly journals The Effect of Particle Size Distribution And Shape On The Microscopic Behaviors of Loess Via DEM

2021 ◽  
Author(s):  
Xi-An Li ◽  
Jianqiang Sun ◽  
Hongyu Ren ◽  
Tuo Lu ◽  
Yongbiao Ren ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Contact Force ◽  
Engineering Properties ◽  
Dry Density ◽  
Normal Contact ◽  
Clay Particles ◽  
Normal Contact Force ◽  
Sand Particles

Abstract Loess has loose metastable structure, which is not difficult to be destroyed under load. As the core and soul of loess structure, it is part of the main research directions of loess engineering properties at present to study its microscopic behaviors and then realize the interpretation and prediction of macroscopic mechanical properties. In this study, based on the analysis of the basic physical properties of loess samples from seven different places, each sample was scanned by X-ray with continuous slice CT, and the three-dimensional microstructure of loess samples was established. According to the computer graphics method, each particle is equivalent to an ellipsoid, and the flattening rate and elongation rate of particles in each sample are quantitatively counted. Taking the particle size distribution (PSD) and shape parameters (flatness and elongation) of each sample as the control factors for generating discrete element method (DEM) samples, a series of triaxial compression simulation tests were carried out, and the microscopic behaviors of each sample were studied within the whole test framework. Comparing the results of seven different samples, it is shown that both PSD and particle shape have effects on stress-strain relationship, dry density and the normal contact force of loess samples. Most of the sand particles (> 0.075mm) are flat particles, while the clay particles (< 0.005mm) are mainly near spheres. When the volume fraction of sand particles is large, the dry density of the sample is the lowest. However, when the content of near spherical clay particles is large and the particle size distribution is good, and the average coordination value is large, which shows that it has strong normal contact force, and thus higher shear strength.

Experimental Study on Development Characteristics of Dynamic Pore-Water Pressure of Anti-Filter Material in High Earth-Rock Dam

2011 ◽  
Vol 250-253 ◽  
pp. 2435-2439
Author(s):  
Fan Li Meng ◽  
Li Shuang Pan ◽  
Cheng Yuan Lu
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Pore Water ◽  
Stress Ratio ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Ambient Pressure ◽  
Filter Material ◽  
The Relationship

A series of dynamic triaxial tests which used saturated samples of three different particle size distribution anti-filter materials in high earth-rock dams have been investigated for the development of dynamic pore-water pressure. The experimental results show that the relationship between μd/σ'm and N/Nf in the same consolidation condition are unitary if we applied different dynamic stress to the same particle size distribution anti-filter material. Besides, if N/Nf <0.6, the value of μd/σ'm increases quickly. The increase rate of μd/σ'm will be slower if N/Nf≥0.6. When the consolidation stress ratio is invariant, the change of ambient pressure has no effect on relationship between μd/σ'm and N/Nf. When the gradation and ambient pressure of anti-filter material are changeless, the change of consolidation stress ratio has obvious effects on relationship between μd/σ'm and N/Nf. When the value of consolidation stress ratio is increase, the number of dynamic pore-water pressure ratio obviously decrease. When the consolidation condition of anti-filter material is changeless, the change of anti-filter material’s grade doesn’t have obvious effects on the relationship between μd/σ'm and N/Nf.

Effects of Particle Size Distribution on Corrosion Rate of Carbon Steel in Soil

2020 ◽  
Vol 69 (4) ◽  
pp. 102-106
Author(s):  
Shota Ohki ◽  
Shingo Mineta ◽  
Mamoru Mizunuma ◽  
Soichi Oka ◽  
Masayuki Tsuda
Keyword(s):  
Particle Size ◽  
Carbon Steel ◽  
Corrosion Rate ◽  
Particle Size Distribution ◽  
Size Distribution
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