Geotechnical Index Research Articles

Chemical, Mineralogical and Geotechnical Index Properties Characterization of Volcanic Ash Soils

Soils derived from volcanic ash are deposits formed from the weathering of the ejected material during volcanic activity. Volcanic ash is commonly known in geotechnical engineering as a difficult and unwanted material. The difficulties are related to the high-water content, high liquid limits, low unit weights, and high void ratios, which translates into possible engineering problems (e.g. compressibility and collapsibility). The characterization of these materials is important because volcanic soils represent 0.84% of the terrestrial soil surface, 60% of which are located in tropical zones. These percentages represent areas with a high human population and constant demographic and economic growth. This paper presents the chemical, mineralogical and geotechnical index properties characterization of soils derived from volcanic ashes through laboratory testing and compares them with the results found in the literature. The SEM results shows the high void reported in the literature. The index properties obtained coincide with the ranges reported. However, lower values of dry unit weight were observed, which are related to the transportation processes of the particles and with higher index properties values due to mineralogical components such as allophane. Therefore, the study of volcanic ash soils requires a rigorous knowledge and understanding of the soil formation, depositional environment, and mineralogy. The chemical characterization of the volcanic ash plays an important role to understand water retention characteristics and their influence on the different geotechnical properties.

Automated Core Logging Technology for Geotechnical Assessment: A Study on Core from the Cadia East Porphyry Deposit

Abstract The Cadia East porphyry deposit, located approximately 20 km south of Orange, New South Wales, Australia, contains a significant resource of copper and gold. This resource is hosted within the Forest Reefs Volcanics and is spatially and temporally associated with the Cadia Intrusive Complex. To extract ore, the underground mine currently uses the block cave mining method. The Cadia East geotechnical model provides data inputs into a range of numerical and empirical analysis methods that make up the foundation for mine design. These data provide input into the construction of stress models, caveability models, ground support design, and fragmentation analysis. This geotechnical model encompasses two commonly used rock classification systems that quantify ground conditions: (1) rock mass rating (RMR) and (2) rock tunneling quality index (Q index). The RMR and Q index are calculated from estimates of rock quality designation (RQD), number of fracture sets, fracture roughness, fracture alteration, and fracture spacing. Geologists and geotechnical engineers collect information used to produce these estimates by manually logging sections of drill core, a time-consuming task that can result in inconsistent data. Modern automated core scanning technologies offer opportunities to rapidly collect data from larger samples of drill core. These automated core logging systems generate large volumes of spatially and spectrally consistent data, including a model of the drill core surface from a laser profiling system. Core surface models are used to extract detailed measurements of fracture location, orientation, and roughness from oriented drill core. These data are combined with other morphological and mineralogical outputs from automated hyperspectral core logging systems to estimate RMR and the Q index systematically over contiguous drill core intervals. The goal of this study was to develop a proof-of-concept methodology that extracts geotechnical index parameters from hyperspectral and laser topographic data collected from oriented drill core. Hyperspectral data from the Cadia East mine were used in this case study to assess the methods. The results show that both morphological and mineralogical parameters that contribute to the RMR and Q index can be extracted from the automated core logging data. This approach provides an opportunity to capture consistent geologic, mineralogical, and geotechnical data at a scale that is too time-consuming to achieve via manual data collection.

Flows of Liquefied Filtered Tailings: Laboratory-Scale Physical and Numerical Modeling

The numerical prediction of the runout and spread of liquefied-tailings flows is a complex problem that depends on many factors, including the rheological properties of the liquefied tailings. However, published benchmark problems specific to tailings flows, useful for validation and calibration of numerical models, are virtually nonexistent. This paper presents a laboratory-scale benchmark problem of liquefied-tailings flow. Gold filtered tailings were characterized via rheological measurements, geotechnical index tests, and toxicity chemical analysis. Physical flow experiments of the liquefied-tailings paste, at 70% solids concentration, were carried out in an instrumented laboratory flume with high-speed video and direct measurements of the at-rest “footprint” (lobe) dimensions. Subsequently, using the measured physical parameters, computational fluid dynamics (CFD) tools were used to solve the three-dimensional, rheology-dependent Navier–Stokes equations via the finite-volume method and a multiphase volume-of-fluid (VOF) technique. Thus, the at-rest lobe of the spilled tailings was numerically reproduced. Results show that the liquefied tailings bear nearly zero-yield stress and low viscosity, thereby practically behaving as a Newtonian fluid despite their high solid concentration. In addition, good agreement (within 14% of the main dimensions) was found between the physical and numerically simulated at-rest lobes. Hence, the use of a Navier–Stokes approach, supported on a finite-volume/VOF technique, and a Newtonian-fluid constitutive rheological model, simulates well the at-rest shape of liquefied tailings at laboratory scale. This benchmark problem will aid numerical research specific to tailings flows.

Experimental Study of the Effects of Some Selected Geotechnical Indices on the Unconfined Compressive Strength of Lateritic Soil

This study undertook an experimental study of the comparative effects of Atterberg limits, particles size and compaction parameters on the unconfined compressive strength of selected soils. This was with a view to ascertaining which of the combinations of the soil properties will produce a good prediction of the unconfined compressive strength. To achieve this aim, soil samples were obtained from selected locations within Ife Central Local Government Area, Osun State, Nigeria. The following tests were conducted on the soil samples, following standard procedures: natural moisture content determination, specific gravity, Atterberg limits, compaction and unconfined compressive strength. Using Regression tool, the results obtained from the laboratory tests were used to develop the relationships between each of the index properties and unconfined compressive strength. Results showed that the natural moisture content of soil samples ranges between 18.48 % and 25.03 %; specific gravity ranges between 2.35 and 2.69; liquid limit ranges between 39.95 % and 83.98 %; plastic limit ranges between 29.32 % and 51.18 %; and plasticity index is between 8.74 % and 33.56 %. The maximum dry density ranges between 15.30kN/m3 and 19.30kN/m3 with their optimum moisture contents ranging between 13.80 % and 35.50 % while unconfined compressive strength is between 36.00 kN/m2 and 97.14 kN/m2. The results of regression analysis showed that effective size and coefficient of uniformity have the greatest effect (R2 = 0.82) on unconfined compressive strength of the tested soil samples. Therefore, the study concluded that effective size and coefficient of uniformity could be used to estimate the unconfined compressive strength of the soils.

Analyses of some Geotechnical Indices of the Federal Polytechnic, Ado-Ekiti Lateritic Soil used for Bricks

Analyses of some Geotechnical Indices of the Federal Polytechnic, Ado-Ekiti Lateritic Soil used for Bricks

Examination of Factors Affecting the Shear Strength of Granulated Blast Furnace Slag

Blast furnace slag (BFS) is an alternative material used in various civil engineering functions, such as stabilization of problematic soils, ready mixed concrete production, road and foundation construction and fill material. In this study the geotechnical index properties and shear strength behaviour of Granulated Blast Furnace Slag (GBFS) were determined for fine, medium and coarse grained samples at loose, medium and dense densities. The sieve analysis was performed and GBFS was divided in three sections; coarse (4.75 mm - 2 mm), medium (2 – 0.425 mm) and fine grained (< 0.425 mm) samples. The consolidated drained direct shear tests were conducted with saturated samples at a shear rate of 0.20 mm/min. The test results have shown that GBFS had comparatively higher specific gravity than usual soils (3.0 – 3.4). GBFS was basic (pH >7) and non- plastic characteristic (NP). The maximum shear stress of the samples was obtained at 5% - 10% axial deformation range. The internal friction angle of fine, medium and coarse grained samples were with in the range of 14° - 33°, 27° - 42° and 46° - 50°, respectively. The highest internal friction angle for fine and medium grained samples were obtained for dense samples. Increment of density affects the internal friction angles of medium grained samples positively. However, no significant change in the internal friction angle of the coarse grained samples was observed. The cohesion of GBFS samples ranged between 7 and 39 kPa.

Permafrost geotechnical index property variation and its effect on thermal conductivity calculations

Geotechnical borehole and sample data from three databases compiled by the Geological Survey of Canada were analyzed to determine the variability of geotechnical index properties within frozen soils. The analysis included 2662 boreholes with geological setting data, up to 60 m depth, within the Mackenzie Valley and Delta region of the Northwest Territories. A total of 7539 samples, each with soil and ice classifications and gravimetric moisture content data were included. Gravimetric and volumetric moisture contents were analyzed by general soil type to determine their coefficient of variation (COV) with depth and geologic setting. As expected, variability between geologic settings corresponded to the nature of the soil's depositional environment, and volumetric ice content variability decreased with increasing depth. General soil type was also used to determine the COV for dry density, specific gravity, and Atterberg limits for samples where testing was available. The variability of frozen thermal conductivities was estimated using Monte Carlo simulation and common equations from the literature based on the geotechnical index property variation. Recently-derived equations for thermal conductivity showed less variability compared to earlier methods.

Geotechnical characteristics and consolidation properties of Tianjin marine clay

Tianjin, which is located on the west shore of the Bohai Sea, is part of China\'s Circum-Bohai-Sea Region, where very weak clay is deposited. From the 1970s to the early 21st century, Tianjin marine clay deposits have been the subject of numerous geotechnical investigations. Because of these deposits\' geological complexity, great depositional thickness, high water content, large void ratio, excessive settlement, and low shear strength, the geotechnical properties of Tianjin marine clay need to be summarized and evaluated based on various in situ and laboratory tests so that Tianjin can safely and economically sustain more infrastructure in the coming decades. In this study, the properties of Tianjin marine clay, especially its consolidation properties, are summarized, evaluated and discussed. The focus is on establishing correlations between the geotechnical property indexes and mechanical parameters of Tianjin marine clay. These correlations include the correlations between the water content and the void ratio, the depth and the undrained shear strength, the liquid limit and the compression index, the tip resistance and the constrained modulus, the plasticity index and the ratio of undrained shear strength and the preconsolidation pressure. In addition, the primary consolidation properties of Tianjin marine clay, such as the intrinsic compression line (ICL), sedimentation compression line (SCL), compression index, Cc, coefficient of consolidation, Cv, and hydraulic conductivity change index, Ckv, are evaluated and discussed. A secondary consolidation property, i.e., the secondary compression index, Ca, is also investigated, and the results show that the ratio of Ca/Cc for Tianjin marine clay can be used to calculate Ca in secondary consolidation settlement predictions.

The Influence of Organic Matter Content on the Rheological Model Parameters of Soft Clay

Soil samples with different organic matter contents and their geotechnical index properties were determined. With an improved direct shear creep apparatus, the rheological characteristics of the soil samples were tested under stepwise loading, and the strain-time curves (creep curves) under different loads were obtained. Based on the Nishihara model, a new nonlinear viscoelasto-plastic soil rheological model (improved Nishihara model) was proposed by introducing a nonlinear Hooke element, which is capable of reflecting the rheological properties of artificial soft clay and natural soft clay. The results of the fitting indicate that the organic matter content is an important factor in the creep behavior of soft clay, and there is a good correlation between the organic matter content and the rheological model parameters.

Hazard susceptibility related to clay shrinkage–swelling phenomena in north-eastern Tunisia (Grombalia area)

The investigation of the shrinkage–swelling phenomena in argillaceous formations of the Grombalia area (north-eastern Tunisia) has allowed the identification of three classes of clays. The first class contains three argillaceous formations and has a low susceptibility towards shrinkage–swelling phenomena. The second class, represented by four argillaceous formations, has an average susceptibility. The third class, comprises four argillaceous formations that have a high susceptibility. Therefore, in the study region, the hazard susceptibility towards the constructions can be significant for certain zones, because of the extension of constructions which is the result of the development of demography and industry in the recent years. Three indices have been determined to obtain these classes: the lithology indices, the mineral composition indices and the geotechnical indices. A description of the lithology of geological formations and X-ray diffraction results from analysis on bulk samples allow recognising the amount of clays in each formation. However, argillaceous formations composed essentially by clays does not mean that it has a high susceptibility towards shrinkage–swelling phenomena. To improve interpretation, XRD results reveal the volume proportion of minerals that exists in each argillaceous formation. Indeed, formations having high susceptibility towards shrinkage–swelling phenomena show a high volume of smectites and/or interstratified. The additional data provided from geotechnical study on argillaceous formations have allowed an inference about the degree of the shrinkage–swelling susceptibility for all the argillaceous formations in the Grombalia area. In fact, geotechnical results have allowed determining the plasticity index value, the methylene blue value and the linear shrinkage value. Determining the degree of the shrinkage–swelling susceptibility must be inferred from the three indices (lithology, mineralogy and geotechnical), because applying only the results of one feature can lead to a false decision.

Fracture mapping in challenging environment: a 3D virtual reality approach combining terrestrial LiDAR and high definition images

The latest technological developments in computer vision allow the creation of georeferenced, non-immersive desktop virtual reality (VR) environments. VR uses a computer to produce a simulated three-dimensional world in which it is possible to interact with objects and derive metric and thematic data. In this context, modern geomatic tools enable the remote acquisition of information that can be used to produce georeferenced high-definition 3D models: these can be used to create a VR in support of rock mass data processing, analysis, and interpretation. Data from laser scanning and high quality images were combined to map deterministically and characterise discontinuities with the aim of creating accurate rock mass models. Discontinuities were compared with data from traditional engineering-geological surveys in order to check the level of accuracy in terms of the attitude of individual joints and sets. The quality of data collected through geomatic surveys and field measurements in two marble quarries of the Apuan Alps (Italy) was very satisfactory. Some fundamental geotechnical indices (e.g. joint roughness, alteration, opening, moisture, and infill) were also included in the VR models. Data were grouped, analysed, and shared in a single repository for VR visualization and stability analysis in order to study the interaction between geology and human activities.

Effects of homogeneous hydrocarbonic contamination on the bearing capacity of in-situ concrete piles buried in silty sand

So far, many researches have been done on the effects of hydrocarbon (especially oil) contamination on such soil strength and geotechnical indices as cohesion, angle of internal friction, shear strength, permeability, dry density, and so on. In the present research, effort has been made to model buried concrete piles with known dimensions, and study the effects of the length and diameter ratios (L/L0 and D/D0) on their load bearing capacity using the results of previous researches, the values of the geotechnical and strength parameters of oil-contaminated silty sand (SM) specimens, and the PLAXIS 2D Software. Results have shown that with an increase in the percent hydrocarbon contamination, the ultimate load bearing capacity of a pile follows a gradual decreasing trend. Again, an increase in the pile length ratio causes an increase in the load bearing capacity, but one in the diameter ratio causes a decrease in the bearing capacity.

Geotechnical Index Properties of Soils in Abua and Environs: A Case Study of Obedum-Anyu-Emelago Road

The frequent collapse of engineering structure and in incessant cracks witnessed on walls of buildings within the Obedum-Anyu-Emelego axis of Abua/Odual Local Government Area of Rivers State prompted the need for geotechnical investigation to assess the suitability of soils and characterize their engineering properties as a guide to foundation designs. Soil samples were obtained between 0 and 30 metres depth and used in the study. The field boring and laboratory results shows that the stratigraphy is predominantly of medium with soft to firm brown mottle grey salty peaty clay and soft to firm grey mottle brown salty peaty clay in shallow borings of 2 m. The organic peaty clay layers are very poorly suited to support foundations due to very high compressibility compared to other materials. Laboratory analyses showed that the clays are characterized by moderately high moisture content and compressibility and fairly low undermined strength. CBR values between 5.7 percent to 8.5 percent, liquid limit between 38.8 percent and 50.6 percent, plasticity limit 18.8 percent and 25.5 percent. Comparison of these ranges of geotechnical properties with Bench Mark for sub grade indicated that they are of low standard. Recommendation includes the need for stabilization with lime and cement to avoid the collapse of structure or buildings within the study area.

Systematic Studies on Defining Interaction Process of Clay Minerals for Achieving Synthetic Mixtures as Composite Materials Applied in Stabilization Works

By considering the worldwide use of composite materials in stabilization works, according to sustainable and ecological principles, the present paper is focused on the analysis of changes of several geotechnical properties depending on components of bi-mineral mixtures and interaction existing among various mineral types. Correlations of soil geotechnical indices as plasticity limits, particle size distributions, linear swelling and chemical-mineralogical composition have been determined for two clay bi-mineral mixtures (montmorillonite-illite and kaolinite-illite). Dependency of plasticity limits with mineralogical compositions and ion nature in absorption complex and linear relations between activity factor and liquid limit – plasticity index have been carried out. Effect of moisture content on soil properties, which influenced the aggregation or dispersion processes, has been investigated through a parallel preparation of samples resulting from the mixing of the component material in dry and wet state. Analysis of swelling characteristics has indicated various behaviors of clay soils depending on type and amount of mineral components. The influence of adsorbed ions on physical and mechanical soil characteristics on clay mineral mixtures, as well as long-term structural variations have been studied. The results will lead to improvement of material performances used in stabilization according to internal soil changes mixture behavior.

Geotechnics of municipal sludges and residues for landfilling

This paper presents a comprehensive review of reported field and laboratory investigations and theoretical work concerning the geotechnical behaviour/properties of water treatment residue (WTR), biosolids and sewage sludge materials, which are by-products of municipal water and wastewater treatment processes. After describing the backgrounds to the generation of these materials and various disposal options (with a focus on landfilling), including associated geotechnical issues, their physical, geotechnical index, compaction, undrained strength and effective-stress strength properties are described, including the effects of oxidation, biodegradation and viscous gel-like pore fluid for biosolids/sewage sludge material. Characteristic compressibility, consolidation and permeability behaviour/properties are also presented for these materials and linked with microstructure and the chemicals added during the treatment processes. The paper then focuses on various geotechnical issues pertinent to landfill (monofill) disposal of these materials, including undrained strength requirements, design strength, on-site and laboratory strength measurements and water content–strength correlations. Since such correlations are material specific, with the geotechnical properties of biosolids, sewage sludge and WTR materials varying between water/wastewater treatment plants, they cannot be applied more widely with confidence. Alternative approaches to predicting undrained strength are described, including a power–law strength relationship with water content, which can be applied more generally.

Spatial variability analysis of subsurface soil in Mashhad city, NE Iran

Reliable characterization of subsurface soil in urban areas is a major concern in geotechnical and geological engineering projects. In this regard, this research deals with development of a 3D geological engineering model on Mashhad City soil using Sequential Gaussian Simulation (SGS) approach. The intense variability of soil in the study area has sometimes caused serious problems in civil engineering projects in the city. Therefore, a better understanding of these deposits is critical for current and future civil engineering work. The main objectives of this study were investigating the spatial variability of soil through variograms and then predicting the values of soil properties at unsampled locations using SGS method. In this study, some geotechnical index parameters including percentage of fine grained material, plasticity index, and liquid limit have been employed as input data. A database including the data of 1750 boreholes was built and the hard data were transformed into normal scores in order for them to be applicable as input data in SGS modeling. Maps related to the average of all realizations along with Coefficient of Variation (CV) were provided for each variable as well. Then the maps were interpreted according to Mashhad City sedimentary environment.

Evaluating the Correlation Between the Geotechnical Index and the Electromagnetic Properties of Fouled Ballasted Track by a Full-Scale Laboratory Model

To determine the correlation between water content or fouling of a railroad track and ground-penetrating radar (GPR) signals, a full-scale railway track model was designed and constructed at the University of Massachusetts Amherst. A track section was simulated by creating a model consisting of rails and ties placed on a ballast layer on a subballast layer. The model was constructed three times with three fouling percentages. Each model was tested with water-content conditions of dry, field capacity, and two points in between these extremes. Frequency antennae of 450 MHz and 2 GHz were used to evaluate the conditions. The design and construction of the full-scale track in addition to the GPR data analysis and interpretation are presented in this paper. The results show that the dielectric permittivity and frequency spectrum can be used as an indicator of percentage of fouling and water content of a track. In addition, a linear correlation was observed between the percentage of fouling and the water content under field capacity conditions.

Geotechnical evaluation of Ankara clay as a compacted clay liner

This study investigates the geotechnical properties, and mineralogical and permeability characteristics of “Ankara clay” to evaluate its suitability as a compacted clay landfill liner material. The geotechnical index properties of the clayey soil samples collected from the western part of Ankara were determined. All the soil samples were tested for permeability by means of falling head compaction permeameter apparatus. The mineralogy of the soil samples were examined by X-ray diffraction and scanning electron microscope analyses. The cation exchange capacities of the soil samples were determined by the methylene blue adsorption test in order to determine the presence of swelling clay minerals in the soil samples. The influences of the geotechnical indices and mineralogy of Ankara clay on the hydraulic conductivity were investigated. Several landfill profiles containing various compacted clayey lining systems were simulated by the Hydrologic Evaluation of Landfill Performance model. All the soil samples tested led to hydraulic conductivities lower than the suggested regulatory limits (1 × 10−9 m/s) and therefore, are suitable to be utilized as compacted clay liners in potential sanitary landfill sites. Recommendations regarding field construction of the compacted clay liner are provided.

준설토의 간극비 변화 관찰을 위한 물리탐사기법의 적용

해성점토를 활용한 준설매립공사에서는 준설토의 거동분석이 선행되어야 한다. 본 연구에서는 침강압밀하는 준설토의 밀도와 간극비 변화를 관찰하기 위해 물리탐사기법을 적용하였다. 서해안에서 채취한 흙에 대한 기본물성시험을 실시하였고, 침강압밀시험기에 시료를 단계적으로 투기하여 시간에 따른 계면고와 탄성파의 변화를 관찰하였다. 흙의 침강압밀이 완료된 후 하방향의 투수시험을 실시하여 조간대의 영향이 준설토의 물리적 특성에 미치는 영향을 관찰하였다. 또한 초소형 전기저항탐침을 관입하여 깊이에 따른 시료의 전기비저항을 측정하였다. 모든 실험이 완료된 후, 시료를 채취하여 간극비를 계산하였다. 실험결과, ML 시료의 특성상 급격한 침강을 보여 침강압밀특성을 육안으로 관찰하기 어려웠으나, 단계투기가 계속될수록 탄성파의 속도는 증가하는 경향을 보였다. 하방향 투수에 따른 조간대 영향은 매우 적어 관찰할 수 없었다. 한편 탄성파 속도로 추정한 시료의 간극비는 단계투기에 따라 선형적으로 증가하는 경향을 나타내었다. 전기비저항으로부터 계산된 간극비는 깊이에 따라 반복적으로 증가, 감소하는 형태를 나타내었으며 이는 단계투기에 따라 층을 이루고 있는 시료의 영향으로 파악된다. 시료채취, 탄성파 속도, 그리고 전기비저항으로부터 구한 간극비를 비교한 결과, 서로 유사한 관계를 나타내었다. 본 연구는 물리탐사기법이 준설토의 간극비 관찰에 효과적으로 활용될 수 있음을 보여준다. It is necessary to understand the behavior of the soils for the dredging constructions. The objective of this study is to estimate void ratio and density changes of the dredged soils by using the geophysical testing methods. A series of laboratory tests is performed to obtain geotechnical index properties of the specimen, retrieved from the west coastal of Korea. The sedimentation and self-weight consolidation tests are carried out with observing changes of the interfacial height and the elastic wave velocities. The same amounts of the soils are poured into the testing column at intervals of 12 hours until the interheight reaches to a certain level. After the completion of the sedimentatation and self-weight consolidation tests, downward permeability test is performed to assess a tidal influence in the nearshore. The mini resistance cone is penetrated into the specimen to measure the electrical resistivity with depth. All tests are completely finished, the weight of specimens are measured to calculate the void ratio with the depth. Experimental results show that the aspects of the self-weight consolidation are invisible during dredging process because of rapid sedimentation characteristics of ML. However, the elastic wave velocities increase with increasing in the effective stresses. During permeability test, measured permeability and the elastic wave velocities maintain almost identical values. Void ratio based on the elastic wave velocities changes linearly with time during the step dumpings. Void ratio estimated by the electrical resistivity represents the repeatedly layered depositions according to the step-by-step dumpings. Void ratio determined by soil sampling is similar to those of elastic waves and electrical resistivity profiles. This experimental study demonstrates that the geophysical testing methods may be an effective method for evaluating the behavior of dredged soils.

The relationship between geotechnical index properties and the pore-size distribution of compacted clayey silts

Abstract In this study, the relationships between geotechnical index properties and the pore-size distribution of compacted natural silt and artificial soil mixtures, namely, silt with two different clays and three different clay percentages (10%, 20%, and 40%), were examined and compared. Atterberg’s limit tests, standard compaction tests, mercury intrusion porosimetry, X-ray diffraction, scanning electron microscopy (SEM) analysis, and Brunauer-Emmett-Teller specific surface analysis were conducted. The results show that the liquid limit, the cumulative pore volume, and specific surface area of artificially mixed soils increase with an increase in the percentage of clay. The cumulative pore volume and specific surface area with geotechnical index properties were compared. High correlation coefficients were observed between the specific areas and both the liquid limit and the plasticity index, as well as between the cumulative pore volume and both the clay percentage and the S coefficient. In addition, qualitative SEM analyses were conducted.