Fines Content Research Articles

Development of machine learning-based standalone GUI application for predicting hydraulic conductivity and compaction parameters of lateritic soils

Hydraulic conductivity and compaction parameters are the key considerations in selecting lateritic soils for engineering construction. Nevertheless, the complexity and high cost of the required tests have driven many contractors and field engineers to skip them, resulting in a succession of engineering structure failures. To overcome this limitation, this study developed machine learning-based standalone GUI application to predict lateritic soils’ hydraulic conductivity (K), maximum dry density (MDD) and optimum moisture content (OMC) from indices including specific gravity, liquid limit, plasticity index, linear shrinkage and fine content. To achieve this goal, the geotechnical properties of three hundred samples, collected using grid sampling method from thirty different lateritic deposits in southwestern Nigeria, were evaluated through laboratory tests. The test results were used to train predictive models using artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS) and Gaussian process regression (GPR). The models’ performance was compared using coefficient of determination (R2), root mean squared error (RMSE), mean absolute percentage error (MAPE) and mean absolute error (MAE). Based on these performance metrics, ANN demonstrated the best performance (R2 = 0.9835, 0.9797, 0.9999; RMSE = 7.938, 0.252, 2.09E-08; MAPE = 0.288, 1.114, 1.587; MAE = 5.432, 0.169, 1.1E-08) for MDD, OMC and K, respectively, followed by GPR and then ANFIS. Thus, the ANN models were selected and embedded in a standalone GUI application to enhance easy and quick prediction of lateritic soils’ MDD, OMC and K. The validity of the ANN-based standalone GUI application was demonstrated by comparing it favorably to notable regression-based models in the literature.

Experimental investigation of erosion and transport of binary sediment in sewer pipes

ABSTRACT Understanding sediment transport in storm sewer systems is essential to prevent pipe blockages, associated flooding, and maintenance. In this research, a laboratory study was conducted in a pipe to investigate the erosion and transport process of a binary sediment, i.e., a material with two different particle sizes. The sediment used in this study was a mixture of two sizes of spherical glass beads (0.8 and 4 mm) and two sizes of natural soil (sand and gravel), with different amounts of small size particles. The results show that the critical velocities for the initiation of sediment transport increase linearly with a decrease in the fine particle content of the mixture. A method to predict the critical velocity of a binary mixture is proposed based on the fine content and the critical velocity of single-size large particle and single-size small particle sediments. The transport rate of the mixture lies between that of the single-size large sediment and single-size small sediment. The transport rate is increased with an increase in the fine content, which means that mixing small particles with large particles can significantly increase the transport rate of large particles and the total transport rate.

Effect of Fine Particle Content on Solution Flow and Mass Transfer of Ion-Adsorption-Type Rare Earth Ores

Fine particle content significantly affects the in situ leaching of ion-adsorption-type rare earth ores. This study investigated the effect of fine particle content on solution flow and mass transfer in leaching. The results showed that with the increase in fine particle content, the peak concentration and peak time of rare earth increased. When the fine particle content exceeded 20%, all ion-exchangeable-phase rare earth ions could be replaced with a low dosage of the leaching solution. The leachate flow rate exhibited multi-stage variation, influenced by solution permeation, ion exchange, and fluctuations in accumulated liquid height. A mass transfer analysis showed that a higher fine particle content corresponded to a smaller plate height and a larger plate number of theoretical plates. As fine particle content increased, the final rising height of capillary water decreased, with rising rates varying across different stages for the samples. Moreover, an increase in fine particle content from 5% to 20% resulted in a 94% decrease in the samples’ permeability coefficients. A mechanism analysis showed that when the fine particle content was higher, the fine particles were embedded in the gaps between coarse particles, and the ore particles in the sample were arranged continuously, resulting in a lower permeability coefficient. Then, the leaching solution could penetrate uniformly, which was beneficial for reducing leaching blind spots and improving leaching efficiency. However, excessive fine particle content might have detrimental effects. Based on these results and considering actual mining conditions, the optimal fine particle content for rare earth leaching is 20%.

Instability of binary mixtures subjected to constant shear drained stress path: Insight from macro and micro perspective

AbstractLoose granular materials may also exhibit instability behaviors similar to liquefaction under drained conditions, commonly referred to as diffuse instability, which can be studied through constant shear drained (CSD) tests. So far, the research on CSD in binary mixtures is still insufficient. Therefore, a series of numerical tests using the discrete element method (DEM) were conducted on binary mixtures under CSD path. The possible model of instability is categorized into type I and type II, type I instability occurs prior to reaching the critical state line (CSL), whereas type II instability occurs after exceeding the CSL. The study analyzes the macroscopic instability behavior and the impact of fine content (FC) on macroscopic instability behavior. The numerical results show that as FC increases, the slope of the instability line (IL) increases initially and then falls in the p‐q plane. In the e‐p plane, the IL decreases initially and then ascends. The instability type of the binary mixtures is influenced not only by relative density but also by FC. The stability index increased first and then decreased with the increase of FC. The microscopic origin of binary mixtures instability is explored by investigating the fabric‐stress relationship. The collapse of the weak contact sub‐network triggers the specimen instability, while the strong contact sub‐network dictates the difficulty of achieving instability. FC influences the evolution of fabric anisotropy of the strong and weak contact networks, thereby controlling the macroscopic instability behavior of binary mixtures.

The influence of fines content on ground collapse due to internal erosion of sand-fines mixtures around defective pipes

Ground collapse caused by defective pipelines has become a global issue with the continuous advancement of urbanization. This study reproduced the internal erosion process of sand-fines mixtures around defective pipes through a series of model tests considering a relatively wide range of fines content and three hydraulic conditions. The erosion characteristics and the evolution of the cavity were analyzed to determine the triggering mechanisms of ground collapse. The results indicate that the formation and evolution of the cavity predominantly depend on fines content under hydraulic loading, which is replaced by ground settlement at lower fines content. Moreover, the scouring of groundwater amplifies the impact of internal erosion, which means the marked ground settlement at lower fines content or the expansion of the cavity even to ground collapse at higher fines content. To prevent sudden ground collapse, it is not recommended to use sand-fines mixtures with a fines content of more than 10% as embedment materials.

Thermo-mechanical response of sand-silt mixtures

The thermo-mechanical response under undrained conditions is crucial in evaluating the mechanical behaviors of sand-silt mixtures. A series of consolidated undrained triaxial shear tests were conducted to investigate the mechanical response of sand-silt mixtures with different fines contents, temperatures, and initial mean effective stresses. The results showed that the volume shrinkage was observed in all specimens during heating. The amplitudes of volume shrinkage were dependent on the fines content and initial mean effective stress. Moreover, the fines content and temperature significantly influence the peak strength, flow behavior, stress ratio at the undrained instability state, and collapsibility index. Furthermore, a unified critical state line has been established in the compression plane for both clean sand and binary mixture under different temperatures and fines contents. It is reliable and suitable to use the equivalent skeleton void ratio to illustrate the thermo-mechanical response of sand-silt mixtures under undrained conditions.

Laboratory evaluation of wicking geotextile for moisture reduction in silty sands at different fines contents

The effect of fines content on the performance of the wicking geotextile is not clear. This study developed a simple moisture reduction test method to quantify the effectiveness of the wicking geotextile in reducing moisture in silty sands at four different fines contents and four different waiting periods. The sand was prepared at an initial moist condition based on its average field moisture capacity. A wicking or non-wicking woven geotextile was placed in the middle of a soil column. The effect of a geotextile on the moisture content of the sand was evaluated by measuring their gravimetric moisture contents at different distances from the geotextile at different times. Test results show that the amount of moisture reduced by the wicking geotextile decreased with the content of fines in the silty sand. On the contrary, the non-wicking geotextile obstructed water flow, hence moisture accumulated on it. The moisture content profile in the soil column indicated the influence zone by the wicking geotextile in the silty sand, which depended on the fines content. The percent of soil moisture content reduction by the wicking geotextile identified the limit of the fines content for the effectiveness of the wicking geotextile.

The Role of Field Measurements of Fine Dead Fuel Moisture Content in the Canadian Fire Weather Index System—A Study Case in the Central Region of Portugal

The Canadian Fire Weather Index System (CFWIS), empirically developed for forests in Canada, estimates the fuel moisture content (mf) at different depths and loads through meteorological parameters. While it is often suggested that adapting an existing fire danger rating system like CFWIS for a new environment requires developing new relationships or modifying existing ones, it is worth considering if such adaptations are always necessary. Based on a dataset of field measurements for surface litter (Pinus pinaster) carried out in the central region of Portugal (2014–2023), we propose a correction of mf based on the Fine Fuel Moisture Code (FFMC) of the CFWIS. This moisture correction was used to determine the Initial Spread Index (ISI) directly and, subsequently, the Fire Weather Index (FWI). Fire records from the study region were used to analyze the performance of the corrected indices. We found that the moisture correction led to higher values and potentially more accurate indices under dry conditions but did not provide a significant improvement in predicting the number of fires and burned areas compared to the original indices. The results suggest that, in relation to fire activity, the CFWIS is sufficiently robust to variations in the fuel moisture content in the study region.

Investigation of cellulosic fines removal in dissolving pulp production with small-holed screen plates

This study investigates the influence of hole diameter and hole spacing on the fractionation performance using an industrial scale pressure screen. The objective is to increase the quality of the long fiber fraction during dissolving pulp production by separating cellulosic fines from unbleached softwood sulfite pulp containing 8% (w/w) primary fines (fibrous particles shorter than 0.200 mm fiber length). Different screen basket designs were applied, using the same hole spacing while varying hole diameter, and vice versa. This allowed a comparison of the separate influence of hole diameter and hole spacing on the separation efficiency. Production parameters of screening devices are always a compromise between separation efficiency, runnability/plugging, and throughput. High aperture velocity, high feed consistency and low reject rate were identified as the crucial operating parameters for high cellulosic fines removal efficiency, which turned out to be positive in terms of throughput. Considering the different hole diameters, the industrial trials showed that smaller holes yielded better fractionation results. Whereas reduced hole spacing resulted in a denser fiber network on the screen, reducing the amount of fines and short fibers passing, thereby leading to worse fractionation results. By choosing suitable screening conditions, we found that the weight-weighted fines content was reduced more than 50 percent using a one stage fiber fractionation screen set up under industrial conditions. The lowered fines content in the long fiber fraction is expected to allow a reduced purification effort and a lower chemical demand in the subsequent processes of dissolving pulp production. By reducing the fines fraction, consisting of short fibers, fiber fines, as well as mainly short-chain alkali-soluble carbohydrates (hemicelluloses), improvements in process efficiency and dissolving pulp quality can be achieved.

Characterization of mine spoils for the reclamation of degraded lands of the Jos-Bukuru tin field, central Nigeria

Tin mining operations on the Jos Plateau have left a lasting impact on the environment, resulting in derelict land, mine spoils, and over a thousand abandoned mining ponds. These ponds have become potential hazards, endangering unsuspecting members of the public. This study aims to provide a comprehensive geochemical and geotechnical characterization of the mine spoils to assess their suitability for the reclamation and restoration of the degraded mined lands. The geochemical analysis reveals that the mine spoils exhibit a strong to moderate level of acidity, with a pH range of 3.91 to 5.90 (average: 4.85). Furthermore, they display deficiencies in essential nutrients such as phosphorus (average: 0.02%) and potassium (average: 0.31%), as well as trace elements such as copper (average: 19.15 ppm), manganese (average: 165.15 ppm), and zinc (average: 53.24 ppm). Notably, the mine spoils are enriched in iron (average: 6.31%). These findings highlight the inadequate presence of both micronutrient and macronutrient elements necessary for successful revegetation which is a crucial component of reclamation. Results from the geotechnical tests indicate that the mine spoils possess an average fines content of 56.03%, a mean liquid limit of 38.06%, and a mean plasticity index of 15.52%. Additionally, the average linear shrinkage value is measured at 10%. The average values for maximum dry density (MDD) and optimum moisture content (OMC) are 1.65 g/cm³ and 19%, respectively. The unsoaked California bearing ratio (CBR) averages 34.64%, while the coefficient of permeability for the spoil is approximately 1.24x10-3 mm/sec. Furthermore, the spoils average cohesion (C) was measured to be 12.150 while the mean angle of internal friction is 30.77 KN/M2. These results collectively indicate that mechanical and chemical stabilization, involving the use of lime, fly ash, and other soil-stabilizing agents is imperative for the effective reclamation of the degraded lands using the mine spoils. Such measures if adopted and implemented will mitigate the risk of accidents and drowning incidents from mining ponds and other abandoned pits involving unsuspecting members of the public and will contribute to the overall environmental restoration efforts in the Jos-Bukuru Tin Field.

Laboratory investigation of the influence of fines content on the mechanical behavior of sand

The present article seeks to examine and discuss the experimental results that were obtained from a series of straight box shear tests. For this, different soils were prepared with clean sand, which was brought from the Wilaya (Province) of Chlef that is located in northern Algeria, mixed with silt from the same site, clay from the town of M'zilla or clayey loam that is composed half of this same clay and half of silt. The percentages of sand replacement by the selected additions were 0, 10, 20, 30, and 40% in mass ratio. The samples thus prepared were then tested with respect to dry shear, under the normal stresses equal to 100, 200, and 400 kPa. The results obtained showed that the shear strength of the sand from Chlef decreases when the silt content increases from 0 to 40%. With regard to the sand-clay and sand-silt-clay mixtures, it was found that the shear strength decreases until reaching a threshold value that coincides with the addition content of 20%. Then, beyond that value, it begins to increase as the addition fraction increases. Likewise, it turned out that cohesion increases with increasing silt content, while for sand-clay and sand-silt-clay mixtures, this cohesion increases until reaching a maximum value which coincides with the addition of 20% silt content. The same trend was observed for the variation of the direct shear strength, while the friction angle exhibited an inverse behavior.

A New Shear Wave Velocity-Based Liquefaction Probability Model Using Logistic Regression: Emphasizing Fines Content Optimization

A new liquefaction probability model based on shear wave velocity (Vs) was developed through a detailed comparative analysis of existing evaluation methods. Publicly available shear wave velocity liquefaction data were used to evaluate multiple existing liquefaction probability assessment methods under various probability contours and fines content levels. Significant performance differences were observed among the formulae under varying fines content levels. To construct the new model, the random forest feature importance ranking algorithm was employed to select the key parameters, including the effective stress-normalized shear wave velocity (Vs1), corrected cyclic resistance ratio (CSR7.5), magnitude (MW), depth (Z), and fines content (FC). Using these parameters, a new liquefaction probability assessment formula was developed utilizing the logistic regression model to predict the liquefaction probability. The new formula’s performance was subsequently evaluated through a detailed case analysis and validation. The results demonstrate that the new formula achieves a higher accuracy (3–11%) for the liquefaction assessment compared to the existing formulae, performing consistently well across different probability contours and fines content levels, especially in areas with high fines content. This study provides theoretical support and empirical evidence for optimizing the shear wave velocity-based liquefaction probability assessment methods.

Effects of low clay content on the anisotropic behavior of sand-clay mixtures: laboratory investigation using TSHCA

Undrained behavior of sandy soil with fines content is a challenge in geotechnical research. In this article, the effect of low clay content (plastic Kaolin) on the anisotropic behavior of sand is studied. In the technical literature, there are different data about the effect of fine particles (generally high percentage), but there are not enough studies on low fines content (especially plastic fines) and anisotropic conditions. For this purpose, 30 undrained tests are performed using a torsional shear hollow cylindrical apparatus (TSHCA) with constant (αo) and (b) values on Firoozkuh sand. The specimens had Kaolin contents of 0, 3, 5, 7 and 10%, and the inclination angle (αo) is varied from 15o to 60o. The specimens are prepared by dry deposition method and are consolidated under P'c= 100 and 200 kPa. The results of the experiments show that increasing the (αo) leads to more contractive behavior in sand. By adding clay particles to the host sand up to 3%, the peak strength of the specimen is increased (7% and 6% for α=15°and 30°, respectively), and then with the increase of clay content up to 10%, the strength of the specimen is decreased (33% and 22% for α=15°and 30°, respectively). But at α = 60o, with the addition of 5% clay, decrease in the peak strength is observed (about 15%) and with a further increase in the clay content, unlike the angles of 15o and 30o, increase in the peak strength of the specimen is observed, so that at 10% clay, the strength of the specimen is higher than the host sand (about 7%), which can be attributed to the cohesion nature of the clay particles. With the increase of clay content, anisotropy degree is decreased. In other words, with the increase of fines content, the anisotropic behavior is decreased.

Hyperspectral Reflectance Assessment for Preliminary Identification of Degraded Soil Zones in Industrial Sites, India

The study explores the potential of next-generation satellite hyperspectral imaging systems for screening and predicting surface‐soil contamination and degradation by exploiting various spectral indices and signature‐matching techniques at a heavily industrialized area in India. The soil moisture content, desertification and salinity status, clay or fine material content, heavy metal content, vegetation health status, and stress levels were assessed from continuum-removed spectral reflectance values. Results indicated the presence of water in two tailings ponds, high salinity, and desertification values in most of the tailings ponds and dump sites, clay boundary liner along four ponds, high heavy metal indices along three ponds and all dump sites, highly stressed vegetation near all tailings ponds and coal dump sites, and pollutants in nearby water channels. The results suggest a strategy for the initial identification of priority areas for ground-based investigations and an alternative rapid methodology to monitor large industrial hubs in India.

An approach for strength development assessment of cement-stabilized soils with various sand and fine contents

Cement stabilization is a well-established ground improvement technique. However, there have been limited investigations aimed at the effect of heterogeneous soil types with varying amounts of coarse-grained (sand) and fine-grained (silt and clay) substances, on the strength enhancement of cement-stabilized soils. In this cement stabilization research study, sand (S) and clayey silt (F) were mixed together to have a variety between coarse- and fine-grained fractions at 100, 75, 50, 25, and 0 % by dry weight, designated as the ratio of S:F=100:0, 75:25, 50:50, 25:75, and 0:100, respectively. The water content was prepared at the range of 1.25–2.50 optimal water content to simulate field applications. The strength enhancement of cement-stabilized soils was influenced by the fine content, water content, and cement content. The soil–water to cement ratio (s-w/c) was effectively incorporate the impact of both water and cement contents on the strength enhancement, for a given a specific fine content. The generalized correlation between unconfined compressive strength, qu and s-w/c could be represented as a power function: qu = M/(s-w/c)N. In this equation, M and N are constants that are primarily influenced by the fine content. The shear strength ratio versus fine content chart was proposed as a means to assess the effect of fine content on the strength of cement-stabilized soil with varying s-w/c. A stepwise approach for assessing the strength enhancement of cement stabilization in soil based on physical characteristics (i.e., plasticity index and fine content) was proposed and validated. The robustness of the proposed approach was realized by the low mean absolute percent error, (MAPE<7.0 %) and high coefficient of determination (R2 > 0.95) for measured and predicted strengths comparison. This technique serves as a valuable tool for mix design, specifically in relation to clay mineral and fine content. It supports in making engineering decision regarding the appropriate amount of water and cement needed to achieve strength requirements throughout the requisite curing period, while minimizing the number of repetitions needed.

Investigating the competency of some selected soft computing techniques for modeling of lateritic soil strength based on index properties

This study aims to assess the capability of some soft computing techniques including ANN, M5P and RF to accurately predict the strength of selected lateritic soils in southwestern Nigeria from index properties including specific gravity, linear shrinkage, liquid limit, plasticity index, fine sand content, and fines content. To achieve this goal, the experimental dataset obtained from the laboratory analysis of three hundred soil samples taken from thirty different lateritic deposits within southwestern Nigeria was divided into model and gaging dataset. The model dataset contains two hundred and forty data points, which were divided into 70% for training and 15% each for testing and validation of the proposed models. The gaging dataset contains sixty data points, which were used to validate the proposed models against prominent existing models in the literature. The models performances were evaluated using various statistical estimators. Based on the statistical estimators, the proposed models outperformed the existing models in the literature and provided satisfactory performances, thus, they are validated. The obtained R2 values using the ANN model are 0.9967, 0.9963, 0.9989, and 0.9852 for training, testing, validation, and gaging dataset, respectively; the R2 values obtained for M5P model are 0.6676, 0.5501, 0.636 and 0.6727; and the R2 values for RF model are 0.8346, 0.6380, 0.7564, and 0.7901. This implies that ANN provided the most reliable model for the prediction of the soil strength. Thus, ANN is strongly recommended for prediction of lateritic soil strength.

High-strength fiber-reinforced concrete: assessing the impact of polyvinyl alcohol, glass, and polypropylene fibers on structural integrity and cost efficiency

This study delves into the realm of high-strength fibre reinforced concrete (HSFRC), a pivotal material in contemporary construction, with a focus on elucidating its mechanical robustness and durability enhancements facilitated by fibre reinforcement. Previous research on HSFRC has provided mixed results and often neglected the cost implications. However, this study incorporates an array of fibres, encompassing steel, polypropylene, and polyvinyl alcohol, in varied proportions as well as their cost implications to provide a comprehensive evaluation of their impact. Through standardized tests such as compression strength, splitting-tensile strength, flexure strength, water permeability, and ultrasonic pulse velocity tests, alongside an exhaustive cost–benefit analysis, the study uncovers the substantial influence of fiber type and proportion on HSFRC 's properties. Noteworthy findings indicate that both fiber type and fiber ratio can change the strength and durability properties of concrete considerably, however, the use of 1.5% glass fiber gives the best results, in improving the properties of HSC. Moreover, despite the initial higher costs associated with HSFRC production, its protracted durability and diminished maintenance requisites yield substantial long-term economic advantages. Consequently, it is inferred that judicious selection of fiber types and proportions plays a pivotal role in maximizing the performance and cost-effectiveness of HSFRC, thereby advocating for its broader integration within the construction sector. Subsequent research endeavours should concentrate on fine tuning fiber content and types to further elevate HSFRC 's properties.

Response of soil particles around bedrock outcrops to sorting of rock surface flow derived outcrops in a rocky desertification area

Soils around bedrock outcrops, even if they are protected by vegetation to some extent after ecological restoration, are prone to being washed away by rock surface flow (RSF) derived from these outcrops in rocky desertification land. However, the extent of the scouring scale and sorting effect of RSF on the soils around outcrops remains unknown. To solve this problem, a series of soils around bedrock outcrops exposed in sloping farmland (SF, without RSF), abandoned land (AL, 1 year of RSF) and shrub–grassland (SG, 5 years of RSF) were examined by the laser diffraction method in a natural ecological restoration area of rocky desertification, where the duration of the RSF is also the time for ecological restoration. It was found that the RSF had a limited effect on the particle size distribution of the soils, only having a significant scouring effect on the soils at the rock–soil interface within a horizontal distance of 2 cm from the outcrops and an insignificant effect on the soils far away from the outcrops in terms of horizontal distance (10 cm and 20 cm). The particle size distributions of the soil around the outcrops were related to erosion caused by the RSF, but mainly benefited from ecological restoration. Compared with SF, the fine particle content in the soils around the outcrops significantly decreased in AL, but significantly increased in SG. Within a short period (1 year) after natural recovery, the RSF had a reduced effect on the fine particles of the soil around the outcrops; however, this did not occur after a long period (5 years). The results of this study further explain the influence of the RSF on soil erosion and leakage loss in karst areas.

Effects of Palm Kernel Shells (PKS) on Mechanical and Physical Properties of Fine Lateritic Soils Developed on Basalt in Bangangté (West Cameroon): Significance for Pavement Application

The utilization of an agricultural waste product known as palm kernel shells (PKS) combined with fine laterites (from basalt in Bangangté, West Cameroon) to produce low-cost and innovative materials with good bearing capacities for road pavement was investigated. Fine laterites from two soil profiles (BL31 and BL32) and made up of kaolinite, hematite, goethite, gibbsite, anatase, ilmenite and magnetite minerals were partially replaced with PKS at 15%, 25%, 35%, and 45% by weight. Physical and mechanical tests, including particle size distribution, Atterberg limits, unsoaked and soaked California Bearing Ratio (UCBR and SCBR), unconfined compressive strength (UCS), and tensile strength (Rt), were performed on the different mixtures. After the addition of PKS, a decrease in fine particle content (77 to 38%), liquidity limit (LL: 72 to 61%), plasticity index (PI: 30 to 19%), maximum dry density (MDD: 1.685 to 1.29 t/m3), and optimum moisture content (OMC: 27.5 to 24.0%) was noticed. Additionally, there was an increase in UCBR (16–72%), SCBR (14–66%), UCS (1.07–7.67 MPa), and Rt (2.24–9.71 MPa). This allows new materials suitable for the construction of base layers for low trafficked roads (T1–T2), as well as sub-base and base layers for high trafficked roads (T3), to be obtained. This newly formed material can be recommended locally for road construction works, though more in-depth studies are required.

Investigation of Unresolved Interface "Rag Layer" in Athabasca Oil Sand Bitumen In Situ Recovery.

Steam-assisted gravity drainage (SAGD), the leading commercial in situ bitumen recovery process, involves the underground injection of steam and produces at the well head a hot fluid containing water, hydrocarbons, and sand. This fluid is subjected to separation by diluent addition and gravity in several parallel treaters. Occasionally, the separation may be disrupted in one or few treaters by the occurrence of an unresolved interface or "rag layer" while continuing without disruption in the rest of the treaters. In the current study, we investigate "rag layer" occurrence based on the quantification of laboratory-scale and SAGD field tests and imaging of the "rag layer" morphology. The quantification results show that the formation and volume of the "rag layer" are affected by solids, mixing speed, and solvent addition. The microscopic images demonstrate the presence of both water-in-oil or oil-in water emulsions with a distinct transition between the continuous phases. The visual detection boundaries of the "rag layer" are defined as the threshold between the agglomerated and individual droplet layers. The extent of agglomeration increases in the proximity to the oil-water interface. The contribution of hydrophobic fine inorganic solids (less than 10 μm) to forming a "rag layer" is supported by their accumulation observed at the treaters' oil-water interface, compared to the feed. In well-controlled field operations, the perceived randomness of "rag layer" occurrence could be associated with the fluctuation of fine solid contents in the feed.