Falling Head Permeability Tests Research Articles

Hydroelectric simulation of the phreatic water response of mining cracked soil based on microbial solidification

Abstract Coal mining in ecologically fragile areas results in the failure of aquiclude layers and the loss of surface water bodies. Herein, research was conducted on the microbial solidification of cracked soils and the corresponding response of the ecological water table. A simulation of mining-induced cracked soils was performed via microbial solidification. The mechanical and hydrological properties of cracked soil samples repaired with different filling materials were compared via unconfined compressive strength and falling head permeability tests. Hydraulic-electric similarity modeling techniques were employed to evaluate the effectiveness of microbial solidification in the aquiclude layers. After low-temperature acclimation, Bacillus megaterium adapted to the geological environment of the study area, exhibiting a high viable cell density. When the cracked soil was filled with a 1:1 ratio of aeolian sand to clay particles, the microbially remediated soil demonstrated optimal mechanical and hydraulic properties. Hydraulic-electric similarity numerical simulations revealed that the ecological water table at the coalface remained within a reasonable range following microbial solidification, suggesting that microbial solidification achieved water-preserving coal mining. These findings provide a reference for restoring aquiclude layers damaged by coal mining.

Refined evaluation approach for geometrical, physical and chemical properties of completely decomposed tuff soil particles

This paper presents a refined approach for evaluating the geometrical, physical, and chemical properties of weathered soil particles and illustrates it with a completely decomposed tuff (CDT) soil. This refined evaluation approach consists of two parts. Part I separates soil into 25 sub-groups of gravel, sand, silt, and clay particles from 14 mm to less than 0.0008 mm by washing and sieving. Part II applies laboratory tests to examine the refined geometrical, physical, and chemical properties of each sub-group of materials. These laboratory tests include the dynamic and static image analysis for particle shape evaluation, the Atterberg limits test for plasticity evaluation, the falling head permeability test for hydraulic conductivity evaluation, the energy dispersive X-ray spectrometer (EDS) test and X-ray fluorescence spectrometer (XRF) test for elemental composition evaluation, and the X-ray diffractometer (XRD) test for mineral composition evaluation. The quantitative results of these refined properties of the soil materials can be expressed as a function of the particle size. The characteristics of each sub-group of particles together determine the properties of the soil mixture. This refined evaluation approach provides a new insight for examining the properties of weathered soils and their weathering degrees.

Permeability Characteristics of Improved Loess and Prediction Method for Permeability Coefficient

Due to its unique geotechnical properties, loess presents itself as a cost-effective and energy-efficient material for engineering construction, aiding in cost reduction and environmental sustainability. However, to meet engineering specifications, loess often requires enhancement. Evaluating its permeability properties holds significant importance for employing improved loess for construction materials in landfills and artificial water bodies. This study investigates the influence of dry densities, grain size characteristics, grain size distribution, and admixture contents and types on the permeability of improved loess, focusing on the Malan and Lishi loess. The falling head permeability test was conducted to analyze how each factor affects the permeability of the improved loess. The findings indicate that the permeability coefficient decreases with increased dry density and admixture content. Conversely, it demonstrates a linear increase with the average grain size (d50), restricted grain size (d60), and the product of the coefficient of uniformity and coefficient of curvature (Cu × Cc). The primary influencing factor is the type of admixture, followed by Cc and d60. Furthermore, this study developed a predictive model for permeability using a support vector machine (SVM), surpassing the predictive accuracy of linear regression and neural network models. The model provides a robust prediction for the permeability of superior loess material.

Permeability characteristics and mechanism of tungsten tailings treated by the acid solutions

<p>Most of the tungsten tailings (TTs) are filled in the open. As a result, the phenomenon that acid rain influences the engineering geological characteristics of tungsten tailings is impossible to avoid, especially in southern China, where acid rain occurs frequently. This work studied the permeability properties of TTs treated with different acid solutions. The HCl, H2SO4, and H3PO4 solutions were prepared as the permeate fluids with pH values of 7, 5, 4, and 3. The falling head permeability test studied the TTs’ permeability characteristics under different acid solutions action. The microscopic mechanism of the movement of the acid solutions and TTs was analyzed based on X-ray diffraction results and nuclear magnetic resonance. The experimental results show that the permeability coefficient of TTs decreases first and then increases with the pH value of HCl and H2SO4 solutions and first increases and then decreases and then increases with the pH value of H3PO4 solutions. When the pH value >3, the effect of acid on the permeability coefficient is satisfied with HCl >H2SO4> H3PO4; otherwise, it is satisfied with H2SO4> H3PO4> HCl. The development law of T2 spectrum distribution is consistent with the permeability coefficient of TTs treated with the same acid solution. The acid solutions react with chlorite and calcite in the tailings, which affects the permeability of TTs treated by the acid solution. Therefore, preventing the infiltration of acid solutions from entering the tailings is conducive to improving the stability of tungsten tailings dams.</p>

Study of Residual Soil Permeability Coefficient Post Addition of Coal Fly Ash

Residual soil is soil that is often used as barrier cover soil at the closure of B3 waste storage facilities. This is because the shear strength of the soil is quite good. The minimum value of the soil permeability coefficient (k) for barrier hoods at the closure of B3 waste storage facilities is 10-7 cm/sec. Many residual soils have a soil permeability coefficient (k) of less than 10-7 cm/sec. Because the dominant compound in coal fly ash is silica, mixing this fly ash with residual soil can reduce the value of the soil permeability coefficient (k) and is also expected to increase the shear strength value of the soil. In this study, residual soil samples were mixed with fly ash at 5%, 10%, 15%, 25% and 35% of the dry weight of the soil. This research aims to determine the effect of adding fly ash on the parameters of dry density, shear strength and soil permeability. The tests carried out were standard proctor testing, direct shear test, and Falling-Head permeability testing. The residual soil used in this research came from Hamlet I, Bintang Meriah Village, Pancur Batu District, Deli Serdang Regency. Based on standard proctor testing, the maximum density (gd max) of original soil is 1,410 gr/cm3. The largest maximum density (gd max) was obtained when adding 15% fly ash, namely 1.471 gr/cm3. In the direct shear test, the original soil cohesion value was 0.024 kg/cm² with an internal shear angle of 37.96º. In the variation of adding 15% fly ash, the cohesion value was 0.131 kg/cm² with an internal friction angle of 53.08º. Based on the Falling-Head permeability test, the original soil permeability coefficient value was 1.98 x 10-6 cm/s. The permeability coefficient value for variations in adding 15% fly ash was obtained at 8.02 x 10-8 cm/s.

Comparative study on the hydraulic conductivity of pervious concrete slabs by constant and falling head permeability tests

Comparative study on the hydraulic conductivity of pervious concrete slabs by constant and falling head permeability tests

Comparison of Hydraulic Conductivity Estimation using Falling Head and Mini Disk Infiltrometer in Gypsiferous Soil

Hydraulic conductivity (K) was calculated using falling head (FH) and Mini Disk Infiltrometer (MDI) for 15 Gypsiferous soil. In this study the hydraulic conductivity was predicted by basic infiltration rate (BIR) and using two methods, Wooding-Gardner (W-G) and van Genuchten-Zhang (V-Z). Hydraulic conductivity was measured using a falling head permeability test, and the results were compared to the expected values. A statistical analysis (t-test) was performed to show the significant differences between the two methods and the falling head. The results showed high agreement between (K) values estimated by (FH) and (BIR) for different gypsum content, the results showed that Both methods did not succeed in estimating the hydraulic conductivity for different gypsum content. Values derived from (W-G) method are exaggerated and the values derived from the (V-Z) method are very low compared to the values derived from (FH).

Effect of Bio-Cementation with Rice Husk Ash on Permeability of Silty Sand

The scarcity of competent soils in the desired locations has forced geotechnical engineers to look for soil stabilization that is sustainable and environment-friendly. In this regard, bio-cementation technology has received a lot of interest in this area because of its benefits over traditional soil stabilization techniques. The present study aims to examine the influence of the bio-cementation technique with and without Rice Husk Ash (RHA) on the permeability property of silty sand. Biocemented soil samples were prepared with various combinations of the bacterial solution (0.5, 1.0, and 1.5 optical density (OD)) and cementation solution (0.5, 1.0, and 1.5 molarity) at 0, 3, 7, 14, and 28 curing days. The RHA, an agricultural waste with good pozzolanic qualities, was added to the control soil and the biocemented soil samples at 5, 10, and 15% by weight. A falling head permeability test was employed in this study. The test results showed that the permeability of the soil decreased when the bio-cementation technique, with or without RHA, was applied. The permeability of the soil decreased with increasing BS and CS concentrations in all curing days. A greater decrease in the permeability value was seen when the RHA additive was added to the bio-cemented soil. The results of the micro-analysis tests were also in support of this reduction. Overall, the addition of RHA up to 10% with 1.0 OD BS and 1.0M CS at a 14-day curing period was noted to optimally reduce the permeability property of the soil. Doi: 10.28991/CEJ-2023-09-11-016 Full Text: PDF

A Novel Semi‐Analytical (Inertial) Solution for Determining Permeability of Highly Pervious Porous Materials Using the Two‐Reservoir Laboratory Setup

AbstractTwo conventional experimental procedures for determination of the water permeability of saturated porous medium are the constant and the falling head permeability tests. The first one is more applicable on more permeable materials where the outflow from the sample is measured at variety of constant water heads, while the second one is more convenient for low permeable materials, utilizing the continuous measurements of the water head falling due to filtration through the saturated sample. However, neither of the two is useful for materials of high permeability and large cross‐sectional area. The constant head permeability test faces technical issues since a significant and continuous water discharge is required, while the falling head permeability test has limitations due to neglection of the Forchheimer's high‐velocity flow through the sample, but also the influence of inertia on the fluid mass. Here we proposed an approach for determination of the water permeability of saturated porous medium based on the agreement between the measured water level change in two connected reservoirs containing a porous sample and the new semi‐analytical expression describing that change by accounting for the mentioned theoretical deficiencies. This efficient approach has been tested on four pervious paver samples, and results showed satisfactory agreement with the constant head permeability data. It has been also confirmed the proposed semi‐analytical solution is more accurate than the falling head permeability approach in case of highly pervious materials, while for low permeable materials it reduces to the conventional approach.

Effect of sodium silicate and cement on the improvement of engineering properties of organic soil

The study is aimed at evaluating the effect of adding sodium silicate and cement to organic soil. Geotechnical properties of organic soil are determined before and after the addition of the stabilizing materials, which in this case are cement and sodium silicate. The results obtained after treatment were analyzed and evaluated to determine whether the strength values reached are adequate for strong subgrades for pavement, and airports construction. Organic soil samples used in this study were obtained from Kayseri Free Area in Turkey. Index properties and geotechnical properties of organic soil, which was identified as sample P, were determined and this formed the reference upon which strength improvements of each mix design sample were obtained. Optimum moisture content and maximum dry density of the soil and the various mixes were obtained using standard proctor test. Unconfined compressive tests (UCS), California bearing ratio (CBR), and Falling head permeability tests were used to determine geotechnical properties. UCS tests were conducted on air cured samples for 1, 7, and 28 days. Soaked and unsoaked CBR samples were tested after 1, 7 and 28 days. Hydraulic conductivity was determined using the falling head permeability test. From the experiments, sodium silicate and cement were seen to improve the strength of organic soil and provide acceptable subgrade strength and CBR values. CBR and UCS tests indicated that longer curing periods improved strength even more. Higher values were obtained for 7 days cured samples than for 1-day samples with the highest values being obtained for 28 days cured samples. Design mixes with higher cement and sodium silicate compositions gave the highest values of strength. In conclusion, sodium silicate and cement give positive results when it comes to stabilizing organic soil.

Field-Scale Apparent Electrical Conductivity Mapping of Soil Properties in Precision Agriculture

The physical examination of a functioning cacao farm revealed varying pod production rates in its area. Agricultural soil nutrients assessment is usually through soil geochemical/chemical analyses which are laborious and expensive, necessitating faster/cheaper alternatives. This investigation assessed the physical properties that can substitute for geochemical analysis of soil nutrient. The study was executed at 0.3 m depth. The Volumetric Water Content-VWC and Apparent Electrical Conductivity-ECa of the soils were determined using VG-meter-200 moisture-meter and resistivity earth-meter. 912 ECa/VWC points were measured. Soil textural classes (51-sample) were established using Bouyoucos method. Falling head permeability test was conducted on nine cored soil samples for water infiltration assessment. The soils ECa (10-344 µS/cm) and VWC distributions (2-69%) showed similar variation, increase in VWC corresponds to rise in ECa value; soil moisture aids the mobility of ions in solution and a rise in ECa connotes presence of more dissolved ions. The soils were classified as sandy loam, loamy sand and sandy clayey loam. Soils’ permeability ranged from 4.11x10-5-3.97x10-3 cm/sec; infiltration rate varied inversely with the ECa accounting for the moisture variation. Low permeable soil has high nutrient retention and water-holding capacities. Soil physical properties were effective in evaluating the nutrient inconsistency.

Measurement of pore volume, connectivity and clogging of pervious concrete reactive barrier used to treat acid mine drainage.

It has recently been shown that pervious concrete is a promising, effective technology as a permeable reactive barrier system for treatment of acid mine drainage (AMD). However, pore clogging also occurs simultaneously during AMD treatment. In the present study, mixtures of pervious concrete were made and used in a column experiment during which pore clogging occurred in the samples. Pore volume, connectivity and other parameters of pervious concrete were evaluated using five (5) different methods comprising the volumetric method (VM), linear-traverse method (LTM), image analysis (IA), falling head permeability test and X-ray microcomputed tomography. It was found that pervious concrete effectively removed from AMD, about 90 to 99% of various heavy metals including Al, Fe, Zn, Mn and Mg. Cr concentration significantly increased in the treated effluent, owing to leaching from cementitious materials used in mixtures. The VM and LTM gave statistically similar pore volume results, while IA's values were 20 to 30% higher than those of the conventional methods. The falling head permeability test and IA were found to be effective in quantifying pore clogging effects. Pervious concrete exhibited high pore connectivity of 95.0 to 99.7%, which underlies its efficacious hydraulic conductivity.

Experimental studies on hydraulic conductivity of different straw fiber cement treated mud

Hydraulic conductivity characteristics of mud treated by rice straw fiber and cement were investigated by falling head permeability tests. The experimental results indicated that the water conductivity significantly decreased by the inserting of either cement or rice straw fiber. Comparing with cement-treated mud, the addition of rice straw fiber considerably reduced the water conductivity of the mud composite. Moreover, empirical equations were revealed to predict the value of hydraulic conductivity for the modified-mud.

A novel countermeasure for preventing scour around monopile foundations using Ionic Soil Stabilizer solidified slurry

A novel scour prevention countermeasure of using the Ionic Soil Stabilizer (ISS) solidified slurry was investigated in this study. The ISS-solidified slurry is composed of Ionic Soil Stabilizer, Dispersion Resistance Agent (DRA), silt (or silty clay) and distilled water. It can be placed on the seabed immediately after monopile was installed, or in the developed scour holes. In present study, the first type was adopted as the scour protection layer around monopile. The scour morphology and the performance of scour protection layer was firstly analyzed based on flume experimental results. Furthermore, the falling head permeability tests, Zeta potential tests and scanning electron microscope (SEM) tests were carried out to investigate the scour protection mechanism of ISS-solidified slurry. Finally, the performance of the ISS-solidified slurry as scour protection layer was remarked comprehensively. The results indicate that the ISS-solidified slurry for scour protection is favorable and cost-effectiveness. Compared with the untreated seabed, the ISS-solidified slurry layer can bear with the greater critical shear stress required for the initial scour. The DRA can keep the fluidity of ISS-solidified slurry within an appropriate range and facilitate the hardening process in water simultaneously, so the DRA is indispensable for ISS-solidified slurry when it is used as scour protection layer in field.

Prediction of permeability for fully weathered granite amended with fly ash by fractal dimensions

Fully weathered granite (FWG) is a commonly used material for filling the subgrade of the highway. Existing conventional laboratory experiments indicated that it can be classified as sandy soil as per its particle diameter. Blending fly ash within FWG, referring to fly ash-amended fully weathered granite (FAFWG), seems to heighten its strength and bearing capacity. To estimate the optimal proportion of fly ash, the unconfined compressive strength (UCS) tests had been conducted on six categories of FWG specimens with different contents of fly ash and lime (as an activator) for optimization. The California bearing ratio (CBR) tests on the FWG specimens and those with the optimal proportion of fly ash (12%) and lime (4%) had been further conducted to evaluate the improvement effect of fly ash and lime on engineering properties. The permeability of FAFWG also is compliant with different blending ratios of fly ash and governs the durability of subgrades. For convenience, it was theoretically presented in terms of a fractal dimension of specimens by the image recognition technique. The rationality of the proposed method has been verified by the falling head permeability tests.

Permeability Analysis of Dredged Material and Its Stabilization Using Surkhi/Brick Dust

Abstract: This study presents the permeability and strong relationship of dredged soil stabilized with surkhi/brick dust which is to be used for constructing road embankments. Tests like the unconfined compressive strength test and the falling head permeability test were conducted. The test results showed that as the percentage replacement of surkhi increases, the samples become less permeable. Showing that the surkhi tends to cover up the pore spaces of the soil, causing the water to have fewer passageways. Large amount of sediments are dredged from rivers and lakes as a result of environmental dredging in India. These dredged materials (DM) have poor Geotechnical properties and are normally treated as wastes. On the other Hand, there is a huge demand of sub-grade materials due to the increasing number of highway construction projects in the J&K. Thus, the reuse of the dredged material as sub-grade material may be considered as an Environmental-friendly and economical option. For the stabilization of dredged material various waste materials can be effectively used. brick dust is one such waste product. The surkhi/brick dust is generated from brick kilns. The amount of brick dust produced every year is in the range of 3-4 million ton. This project therefore intends to study the stabilization of dredged material procured from Sindh Nallah having a higher content of alluvial Soil using Surkhi/Brick dust as an additive. Soil stabilization by this means can be utilized on airport pavements, highway pavements, earthen dams and many other situations where sub-soils are not suitable for construction. Keywords: dredged material Sindh Nallah, surkhi, Dredged soil, CBR, UCS, proctor test, porosity, void ratio and permeability

Multi-scale In Situ Investigation of Infiltration Parameter in Pervious Concrete Pavements

Abstract Embedded infiltration rings have been historically used to estimate the infiltration properties of pervious concrete (PC) pavements. However, no methodical study has evaluated the effect of the size of embedded rings on the infiltration characteristics of these special pavement systems. The objective of this research was to assess the infiltration rate of PC using a multi-scale, in situ approach through embedding rings of various sizes in pavement slabs. Essentially, this investigation attempted to identify the most appropriate size of the embedded ring that can estimate infiltration rates of PC slabs in a reliable manner. To meet the proposed objective, a multi-scale in situ experimental program was designed, in which five infiltration rings of inner diameter ranging from 100 to 580 mm were embedded into three PC slabs of dimensions 3 × 2.5 × 0.15 m. A surface infiltration test was also conducted on PC slabs and was found to vary from 0.36 to 1.87 cm/s. The embedded infiltration rate (EIR) was estimated using a falling head permeability test by ponding water above the pavement surface and measuring the time taken to drain. EIRs decreased from 1.36 to 0.27 cm/s with increasing ring diameter from 100 to 580 mm. Field tests also indicated that infiltration rates for smaller ring diameters (180 mm and lower) had higher uncertainty, which was attributed to the inability of achieving optimum compaction efforts inside of smaller rings. Based on the findings, the optimum size for estimating the infiltration rate of PC was found to be 270 mm. It is noteworthy that this diameter is in the range suggested by ASTM C1701, Standard Test Method for Infiltration Rate of In Place Pervious Concrete, i.e., 300 mm. This research helped identify the practicable specimen size that could be utilized by researchers and practitioners to estimate the most reliable field infiltration rates through PC.

Study of the field hydraulic conductivity of thin open-graded friction courses

Permeability of asphalt pavements is a property of interest due to its impact on durability and, potentially, safety. In the case of open-graded friction courses (OGFC), the focus with permeability is on the improved drainage capacity that reduces splash and spray, and hydroplaning potential. Multiple research efforts have developed permeameters to evaluate field permeability. However, most of these efforts consider unidirectional linear Darcy flow, which is not sufficient to describe flow through OGFC layers during testing conditions. The objective of this investigation was to examine the use of an approximate analytical solution based on 2D flow proposed by researchers at UT-Austin to study the field permeability of thin OGFC layers. Additional values for a shape factor were proposed to test relatively large areas of thin OGFC layers. Furthermore, it was found that the use of vacuum grease to prevent water flow between the base of the permeameter and the pavement surface clogged the OGFC surface voids, which notably reduced hydraulic conductivity. To overcome this issue, this study evaluated the use of a closed-cell high-density foam pad as a sealant method. Lastly, the study showed the need for a minimum volume of water to provide a smooth drop in water head during testing. This is necessary to allow for accurate measurement of the three time readings required to describe the nonlinear relationship between elevation head and flow rate during a falling-head permeability test. The lessons learned from this study were summarized in a set of guidelines for the successful development of a new permeameter. These guidelines can be used by other highway agencies interested in evaluating the field hydraulic conductivity of thin OGFC layers.

Stability and permeability characteristics of porous asphalt pavement: An experimental case study

The systematic behavior of porous asphalt pavement (PAP) under normal traffic conditions has been studied in detail in the present work. In the first phase, an observation program measured the stability by Marshall Test for all the prepared design mix samples with normal bitumen (60/70). For the permeability test in the second phase of observation, a model is developed in the laboratory on the same falling head permeability test. The maximum permeability reaches 0.394 cm/sec for a fresh sample and 0.245 cm/sec after one year of environmental exposure. The maximum stability was 26.9 kN, and the average value obtained was 21 kN. The present work approach provides effectively reliable results in terms of stability and permeability of porous asphalt mix. The primary goal of this research is to reduce the possibility of floods and increase driver protection during inclement weather. A particular emphasis was placed on the mix ratio differences between aggregates to achieve the desired permeability while maintaining the necessary stability. The findings indicate that the checked sample looked excellent in terms of permeability.

Assessment of innovative dented sheet liner on the improvement of hydraulic properties of pervious concrete pile

The Pervious Concrete Pile (PCP) is a technique that has emerged as an innovative method to improve radial consolidation and the bearing capacity of soft soils. The PCP, a stiffer vertical column (pile), has voids on the surface that accelerate the radial consolidation and eventually improve soft soils' bearing capacity. Since the PCP is stiffer material, the performance does not depend on the confined soil, unlike other drains. As the rate of radial consolidation hinges on the drain's hydraulic conductivity, ensuring the permeability of PCP along its total length is essential. An innovative method of dented sheet liner has been introduced in this study to improve the hydraulic conductivity of PCP. This method was introduced to create surface roughness and regular voids along the length of PCP. Malleable material like aluminium has been dented with specified patterns as a liner on the inner surface and introduced along with conventional formwork, which shall be removed after the concrete's final setting time. A series of laboratory experiments such as compressive strength, split tensile strength, porosity, and falling head permeability tests were performed on PCP cast using dented sheet liners. The results were compared with the conventional PCP properties to establish the efficiency of dented sheet liner in improving the hydraulic conductivity of pervious concrete. The results show that using dented sheet liners, the hydraulic properties porosity and permeability of PCP have been increased up to 22.5% and 79%, respectively, with minimum reduction in the strength parameters.