Granite Soil Research Articles

Recyclable Adsorbents for Potash Brine Desalination Based on Silicate Powder: Application, Regeneration and Utilization

Silicate mineral powders (SMP) from weathered granite soil from Kazakhstan are proposed for the desalination of potash brines containing sodium, potassium and chloride ions. Batch adsorption experiments using acid-treated silicate (AS) achieved a Na+/K+/Cl− recovery of ~13/28/6 mg/g. An isothermal study best fitted the Freundlich and Dubinin–Radushkevich models for Na+ and K+/Cl−. The kinetic data were best modeled by pseudo-second-order kinetics for Na+/K+ and pseudo-first-order for Cl−. Thermodynamic calculations showed spontaneity under natural conditions. For Na+/K+, physisorption is accompanied by ion exchange. To study the possibility of sorbent reuse, several cycles of K+/Na+ adsorption–desorption were carried out under optimal conditions. AS selectively adsorbed potassium ions, maintaining a high effectiveness during five cycles providing K-form silicate fertilizers. Leachates of spent AS contain high concentrations of K/Na/Ca/Mg and other microelements essential for plants. Thus, SMP resolve two issues: the desalination of brine and the provision of fertilizer.

Color calibration of moist soil images captured under irregular lighting conditions

Soil color is a valuable indicator that visually reflects soil properties. In the field of soil science, soil color has been widely used for soil identification and property assessment. Soil color is influenced not only by soil properties but also by lighting conditions; therefore, adequately considering the effect of lighting conditions for the color-based soil assessment is essential. This paper proposes a color calibration method for moist soil images captured under irregular lighting conditions. Four samples of weathered granite soil with varying water contents were captured under nine different lighting conditions. The effect of lighting conditions on the color of moist soil was analyzed using linear regression analysis in the CIELAB color space. The findings demonstrate a linear relationship between soil color and lighting conditions. Furthermore, the slopes of the linear regression equations remained consistent across all moist soil samples, irrespective of soil type and water content. Based on this, calibration equations were derived to adjust the color of moist soil images captured under arbitrary lighting conditions to those under the desired lighting conditions. The proposed method was validated using soil images captured under natural lighting conditions, which show high accuracy in color calibration except for cases with illuminance exceeding 70,000 lux. This color calibration method provides a reliable approach to evaluating soil properties through accurate color representation and presents new possibilities for developing digital image-based soil property prediction techniques that are less sensitive to lighting conditions.

Experimental Validation of the Cementation Mechanism of Wood Pellet Fly Ash Blended Binder in Weathered Granite Soil.

In response to climate change, wood pellets have been increasingly utilized as a sustainable energy source. However, their growing utilization increases the production of wood pellet fly ash (WA) by-products, necessitating alternative recycling technologies due to a shortage of discharging landfills. Thus, this research seeks to utilize WA by developing a new sustainable construction material, called wood pellet fly ash blended binder (WABB), and to validate its stabilizing performance in natural soils, namely weathered granite soil (WS). WABB is made from 50% WA, 30% ground granulated blast-furnace slag (GGBS), and 20% cement by dry mass. WS was mixed with 5%, 15%, and 25% WABB and was tested for a series of unconfined compressive strength (qu), pH, and suction tests at 3, 7, 14, and 28 days. For the microstructural analyses, XRD, SEM, and EDS were employed. As the WABB dosage rate increased, the average qu increased by 1.88 to 11.77, which was higher than that of compacted WS without any binder. Newly cementitious minerals were also confirmed. These results suggest that the effects of the combined hydration mechanism of WABB are due to cement's role in facilitating early strength development, GGBS's latent hydraulic properties, and WA's capacity to stimulate the alkaline components of WABB and soil grains. Thus, this research validates a new sustainable binder, WABB, as a potential alternative to conventional soil stabilizers.

Assessment of Weathering Intensity and Pedogenesis of Lithosequence Located in Two Agroecological Zones of Nigeria

Elemental oxides can help to identify processes of soil formation and the degree of soil development. This study assessed soil development and weathering intensity in soils developed on schist and older granite in upland tropical rain forest and southern guinea savanna agro ecological zones of Nigeria. Soil profile samples were collected in each of the study locations. In the laboratory, total elemental oxides was determined using the energy dispersing X-ray Fluorescence (EDXRF) XRF SPEC (Minipal 4). The relative intensity of weathering of total elemental oxides was determined by choosing titanium as the suitable indexing element and the relative gain or loss of element was estimated using relative retained element (Ro) equation. Result obtained, revealed that SiO2 was the most abundant in the soils. Distribution of Al2O3 and CaO showed the direction of the pedogenic age. Older granite soil had higher values of Al2O3 and lower values of CaO. There was negative relationship of SiO2 with Al2O3 and Fe2O3. The trace elemental oxides were less than 1% and zirconium oxide was the most retained oxide in the soils. Soil which developed on schist retained more of the trace elements than soil on older granite. There was evidence of alitization, ferritization and desillication in the soils. Parent materials contributed to loss and gain of trace elemental oxides. Older granite soil was more weathered and pedologically older than schist derived soils.

Laboratory Investigation on Excavation Performance of Foam-conditioned Weathered Granite Soil for EPB Shield Tunnelling

As weathered granite soils are extensively distributed in the Korean Peninsula, determining the optimal foam conditioning parameters for weathered granite soils can provide a high workability, low permeability, and high compressibility of weathered granite soils for successful operation of an earth pressure balance (EPB) shield tunnel boring machine (TBM). In this study, a laboratory-scale excavation apparatus was developed to conduct various laboratory excavation simulations for measuring the excavation-induced torque and the abrasivity of cutter bits. In addition, slump values, compressibility, and permeability were measured to evaluate the workability of foam-conditioned weathered granite soils. From the experimental results, the optimal foaming conditions for the weathered granite soil was obtained at foam injection ratios (F/Rs) of 60–70%, foam expansion ratios (FERs) of 15–18, and foaming agent concentrations (Cf) of 3–4%. The experimental results presented in this study can provide the rheological, mechanical, and hydraulic behavior of foam-conditioned weathered granite soils for successful EPB TBM operation.

Site quality impacts tree form, heartwood content and veneer production of plantation-grown Pinus patula

Abstract Plantation forest species were introduced into South Africa due to limited availability of native forests for wood-derived products. Currently, the Mexican pine species, Pinus patula, is the most widely planted softwood species in the country. To study the effect of growth environment on wood and processing properties for the species, sample plots were established in a 20-year rotation covering a wide range of soil geologies and altitudes in Mpumalanga, South Africa. Temperature and seasonal rainfall were also determined for the sample plots. Randomly selected sample trees were harvested from the plots and processed at a plywood plant to determine veneer recovery and quality. Trees grown on sites composed of granite soils, with higher annual maximum temperatures and less rainfall, found in the Highveld region, displayed superior tree size, slenderness, and volume growth, compared to trees grown on dolomite and shale soils common to the Lowveld region. Veneer derived from Lowveld trees had more splits which were largely related to defects. Larger trees also had a greater percentage volumetric heartwood and a smaller live crown, compared to smaller trees. Highveld trees had greater net veneer recovery and produced better quality veneer than trees grown on the Lowveld. In the Mpumalanga forestry region, strong co-relatedness exists between soil geology, altitude, and climate. Although tree form and wood properties were found to differ with varying soil geology and altitude, these differences were primarily related to climate rather than soil properties. These findings highlight the pitfalls associated with neglecting either climate or soil properties when analysing site-specific growing conditions on tree growth and form.

Investigation on the Microstructure, Unconfined Compressive Strength, and Thermal Conductivity of Compacted CDG Soil by MICP Treatment during Curing

As an eco-friendly treatment method, the microbially induced calcite precipitation (MICP) approach has been widely adopted in sand, but its use on compacted fine-grained soils remains scarce. In this study, compacted completely decomposed granite (CDG) soils at both the dry and wet side of the optimum water content (dry- and wet-of-optimum) were treated by the MICP approach, using a bacterial suspension and chemical reagents at fixed concentrations. After various curing periods, the microstructure (by scanning electron microscopy testing), the produced calcium carbonate content, the unconfined compressive strength (UCS), and the thermal conductivity were analyzed through a series of laboratory tests. The testing results indicate that the sample at dry-of-optimum exhibits a flocculated microstructure, while a dispersed microstructure is shown for the sample at wet-of-optimum. The calcium carbonate content increases with the curing period until reaching a stable value at around 6 days’ curing. After 6 days’ curing, the MICP process is relatively static, without significant amounts of calcium carbonate produced. With this treatment, the UCS of the sample is improved, where higher efficiency was observed for the sample at wet-of-optimum conditions. The variation of UCS for the MICP-treated samples with respect to the curing period follows the same trend as that of calcium carbonate content. At dry-of-optimum, the air-solid phases control the heat transfer in the MICP-treated samples with a discontinuous water phase, leading to insignificant effects of the MICP treatment on the thermal conductivity. In contrast, the water-solid phases dominate the heat transfer in the MICP-treated samples at wet-of-optimum, resulting in variation of the thermal conductivity with the curing period similar to that for the calcium carbonate content.

Free Head Shear Test on Decomposed Granite Soil

The study presents the test results of Completely Decomposed Granite (CDG) soil tested under drained triaxial compression, direct shear and simple shear tests. Special attention was focused on the modification of the upper halve of conventional Direct Shear Test (DST) to behave as freehead in movement along with vertical strain control during shear stage by using Geotechnical Digital System (GDS). The results show that Free Direct Shear Test (FDST) has clear effect on the measured shear stress and vertical strain during the test. It has been found that shear strengthparameters measured from FDST were closer to those measured from simple shear and drained triaxial compression test. This study also provides an independent check on the consistency of the data by providing an interpretation for angle of dilation together with shearing resistance by using flow rule analysis

The Contribution of Fe(III) Reduction to Soil Carbon Mineralization in Montane Meadows Depends on Soil Chemistry, Not Parent Material or Microbial Community

AbstractThe long‐term stability of soil carbon (C) is strongly influenced by organo‐mineral interactions. Iron (Fe)‐oxides can both inhibit microbial decomposition by providing physicochemical protection for organic molecules and enhance rates of C mineralization by serving as a terminal electron acceptor, depending on redox conditions. Restoration of floodplain hydrology in montane meadows has been proposed as a method of sequestering C for climate change mitigation. However, dissimilatory microbial reduction of Fe(III) could lead to C losses under increased reducing conditions. In this study, we explored variations in Fe‐C interactions over a range of redox conditions and in soils derived from two distinct parent materials to elucidate biochemical and microbial controls on soil C cycling in Sierra Nevada montane meadows. Soils derived from basalt showed greater rates of Fe(III)‐reduction at increasing soil moisture levels than granitic soils. Increases in Fe(III) reduction, however, were only associated with elevated rates of C mineralization in one basalt soil. Known Fe(III)‐reducing taxa were present in all samples but neither the relative abundance nor richness of Fe(III)‐reducers corresponded with measured rates of Fe(III) reduction. Under reducing conditions, Fe(III)‐reduction was only coupled to C mineralization in the soil with the greatest amount of Fe‐oxide bound C. However, Fe‐oxide ‐bound C was below theoretical limits for C sorption onto Fe‐oxides and not detectable in all soils. Overall, our results suggest that “what's there” in terms of soil chemistry may be a more important driver of C mineralization coupled to Fe(III) reduction than “who's there” in the microbial community.

Field Investigation and Finite Element Analysis of Landslide-Triggering Factors of a Cut Slope Composed of Granite Residual Soil: A Case Study of Chongtou Town, Lishui City, China

Landslides caused by excavations and precipitation events are widespread types of slope failures in southwest Zhejiang, China, in areas with granite residual soil. Investigations of the effect of high precipitation on the hydrological response, stability, and evolutionary mechanism of cut slopes in granite soil areas are lacking. The characteristics of historical landslides in Chongtou Town in southwestern Zhejiang were summarized, and a typical slope was selected for analysis. The hydraulic and mechanical properties of the residual soil and fully weathered granite were tested, and the surface displacements on the slope were monitored. Geo-studio was utilized to establish a coupled seepage-deformation model to validate the numerical method and investigate the landslide-triggering factors of the cut slope. The results showed nearly all historical landslides in Chongtou Town were triggered by precipitation events, and the slide bodies consisted of residual soil and fully weathered granite with similar geotechnical properties. The simulated and measured horizontal displacements were in good agreement, indicating the reliability of the established model and parameters. The stability coefficient decreased with an increase in the gradient or height of the cut slope. The critical height values were 5.3 m, 5.5 m, 5.7 m, 6.0 m, and 6.3 m at slopes of 60°, 65°, 70°, 75°, and 80°, respectively. Long-term torrential rain and short-term high-intensity precipitation events are likely to trigger landslides when the precipitation event lasts longer than 26 h and 78 h, respectively. The landslide formation includes four stages: slope evolution, formation of unloading zone at slope foot, migration and loss of soil particles, and instability of the cut slope. The findings can be used to prevent and manage landslides on cut slopes in areas with granite residual soil.

Effect of weathering on short‐ and long‐term mechanical behaviour of granitic soils from the Benggang area under unloading conditions

AbstractAs regional soils collapse during the development of Benggang landforms, the release of geostress results in soil disintegration. This phenomenon is associated with soil instability, and it necessitates a study on the mechanical behaviour of decomposed granitic soils in response to unloading in the Benggang area. This study addressed the short‐ and long‐term mechanical behaviour of granitic soils with various degrees of weathering in response to unloading. Triaxial unloading and multi‐stage unloading creep tests were performed, including a comparative study of consolidated undrained (CU) triaxial tests. The deformation characteristics of granitic soils differed with the degree of weathering and the initial stress level. The most significant adverse effect of creep behaviour under unloading and undrained conditions was found in granitic soils with the greatest loss rate of maximum shear stress in contrast to the cases of CU compression and one‐time unloading. Additionally, increasing time‐dependent deformation was observed with increasing degree of weathering and initial stress level, which suggested that creep behaviour under unloading conditions accelerated soil erosion and instability in the Benggang area. The results of this study highlighted the potential influences of geostress release and time‐dependent deformation on soil instability in the Benggang area and advanced the understanding of mechanical mechanisms during the development of Benggang landforms.

Impact of mica on geotechnical behavior of weathered granitic soil using macro and micro investigations

The micaceous weathered granitic soil (WGS) is frequently encountered in civil engineering worldwide, unfortunately little information is available regarding how mica affects the physico-mechanical behaviors of WGS. This study prepares reconstituted WGS with different mica contents by removing natural mica in the WGS, and then mixes it with commercial mica powders. The geotechnical behavior as well as the microstructures of the mixtures are characterized. The addition of mica enables the physical indices of WGS to be specific combinations of coarser gradation and high permeability but high Atterberg limits. However, high mica content in WGS was found to be associated with undesirable mechanical properties, including increased compressibility, disintegration, and swelling potential, as well as poor compactability and low effective frictional angle. Microstructural analysis indicates that the influence of mica on the responses of mixtures originates from the intrinsic nature of mica as well as the particle packing being formed within WGS. Mica exists in the mixture as stacks of plates that form a spongy structure with high compressibility and swelling potential. Pores among the plates give the soil high water retention and high Atterberg limits. Large pores are also generated by soil particles with bridging packing, which enhances the permeability and water-soil interactions upon immersion. This study provides a micro-level understanding of how mica dominates the behavior of WGS and provides new insights into the effective stabilization and improvement of micaceous soils.

Site observations of weathered granitic soils subjected to cementation and partial drainage using SCPTU

Because of the cementation inherited from the parent rock, weathered granitic soil is usually susceptible to disturbance, which poses considerable challenges for laboratory characterization. The cone penetration test with pore pressure measurements has long been known for its reliability in site investigations and stratigraphic profiling. However, although extensive piezocone test results and experience are available for sedimentary soil, similar advances are yet to be made for weathered granitic soil. Moreover, the experience from sedimentary soil may not be directly applicable to weathered profiles because of the essentially different natures of the two types of geomaterials. This study performs seismic piezocone tests in a weathered granitic profile comprising residual granitic soil, completely weathered granite, and highly weathered granite. Pore pressure is measured at both the cone mid-face and the shoulder, and the effects of penetrometer size and penetration rate are considered. A series of updated soil behavior type charts is proposed to interpret the test results, thereby allowing the effect of weathering to be evaluated. This paper offers an important extension to the sparse data on the in situ responses of weathered materials.

Numerical analysis of tunnel behaviour considering the spatial variability of geotechnical parameters

This study applies random field theory to simulate the spatial variability of the ground where a tunnel was excavated in a granitic soil mass, in the city of Porto (Portugal). Numerical analyses are performed using the finite-element method combined with random field theory to simulate tunnel excavation. A parametric study to analyse the influence of the correlation coefficient is performed. The results are compared with the measured values and the values obtained with the deterministic computation. The performance of the models is evaluated using two measures of error: root mean squared error (RMSE) and mean absolute deviation (MAD). With the random fields approach (correlation length equal to 0.5) values of MAD equal to 2.18 and RMSE equal to 4.16 were obtained, whereas with the deterministic approach values of MAD equal to 2.29 and RMSE equal to 4.26 were obtained. Furthermore, the performance of the models improves as far as the correlation coefficient increases. Therefore, it is concluded that the results obtained using random fields are better than those obtained using the deterministic analysis.

Effect of Composite Microbial Biopolymer Treatment on Hydraulic Conductivity of Completely Decomposed Granite Soil

In southeast China, slope with completely decomposed granite (CDG) soil is susceptible to landslide under heavy rainfall, due to the fissure-rich and slaking characteristics of this kind of soil. In this context, this study attempted to hydraulically improve the CDG soil in a low-carbon manner by using the composite of xanthan gum and guar gum (i.e., two different microbial biopolymers), as an alternative to cement. Hydraulic conductivity of the treated soil was measured using a tailer-made apparatus. Test result shows that the biopolymer content of 2% could lower the conductivity by over 1000 times, and the ratio of 1:1 between Xanthan and guar gums yielded the best performance in general. Application of composite biopolymer to the slope with weathered granitic soil was investigated using the finite element method simulation. Numerical result indicates that the treatment can eliminate the slope failure effectively under rainfall with a hundred-year return period.

Predicting soil carbon in granitic soils using Fourier-transform mid-infrared (FT-MIR) spectroscopy: the value of database disaggregation

Soil carbon (C) is an important component in quality assessments and efficient models are required to estimate C rapidly. Accurate C assessments are valuable in monitoring land-use changes. Fourier-transform mid-infrared (FT-MIR) spectroscopy has proved to be a powerful tool for assessing C. The potential of FT-MIR spectroscopy to estimate C was evaluated using the following techniques: (1) three algorithms [partial least squares (PLS)], principal component regression (PCR), and classical least squares (CLS); and (2) disaggregating the dataset into subgroups based on soil depth and texture. The C contents of samples collected in the Johannesburg Granite Dome were determined by dry combustion for comparison. The soils ranged considerably in C (0.123–2.650%), clay (2.80–41.20%), and silt content (8.56–23.75%). Using standard normal variant (SNV), Savitzky-Golay smoothing and PLS, the best-performing model was the horizons subgroup which provided values of root mean square error for prediction (RMSEP) between 0.079 and 0.095%, root mean square error for calibration (RMSEC) = 0.041 − 0.092, r 2 pre = 0.6174–0.8459, r 2 cal = 0.6599–0.9778, residual prediction variation (RPD) = 2.404–2.753, and ratio of performance to interquartile range (RPIQ) = 2.667–3.454. The pronounced accuracy of FT-MIR spectroscopy coupled with PLS, pre-processing techniques, and textural subgroups confirms the potential of infrared spectroscopy as an efficient tool for estimating C content. Future studies should investigate the combined effects of FT-MIR spectroscopy and subgroups grouped according to soil types and land-uses when predicting C.

Soil Water Content Regression Analysis of Measurement Data from Hyperspectral Camera in Weathered Granite Soils

Soil water content is one of the most common physical parameters that cause landslides or debris flow. Therefore, it is of very importance to determine or predict the water content quickly and non-destructively. This study investigates the hyperspectral information in the visible near-infrared regions (VNIR) of different samples of granite soils possessing varying water content. Totally 162 granite samples were taken from each mountain area. The samples with different water contents were examined using a hyperspectral radiometer operating in the 400~1000nm range by obtaining the spectral curves. It was found that the variation of VNIR is consistent with the water content variation of weathered granite soils, and the hyperspectral camera was able to detect it. A Partial Least Squares Regression (PLSR) analysis was applied to develop a calibration-model. The PLSR model resulted in a good correlation between the water content and VNIR profile. The results demonstrate that the hyperspectral camera combined with the PLSR model can be a useful and non-destructive tool for determining soil water contents in the weathered granite soils.

Laboratory investigation of CDG soil as source of fine aggregates for Portland cement concrete

Completely decomposed granite (CDG) soil is a typical and abundant in-situ weathered soil on the ground around the world. This paper investigates the possibility of CDG soil as fine aggregates for production of Portland cement concrete. It first develops a washing and sieving method to separate the CDG soil into its constitutional particles including gravel, sand, silt, and clay. It further examines the properties of the CDG sand using Hong Kong and other standards of fine aggregates for concrete. The first type of the property is the geometrical property including the size gradation, stereomicroscope observation, SEM observation, and shape statistical analysis of the sand particles. The second type is the physical property including magnesium sulphate soundness, compacting bulk density, relative density, and water absorption. The third type is its chemical property including chemical elements, acid-soluble chloride content, water-soluble chloride content, acid-soluble sulphate content, total sulphur content, and presence of humus. The fourth type is the mechanical property including drying shrinkage, effect of organic substances, and alkali silica reaction potential. These test results show that all the properties of the CDG sand well meet the standard requirements and can be used as fine aggregates in Portland concrete.

Soil Water Characteristic Curve Analysis of Weathered Granite Soils with Various Fine Content

Determining the parameters related to unsaturated soil properties considering capillary and adsorption phenomena is challenging. In addition, the matric suction generated in unsaturated soil increases the stability of the slope; however, the decrease in matric suction owing to heavy rain causes a decrease in slope stability. Therefore, it is crucial to determine the parameters of unsaturated soil accurately. In this study, the engineering characteristics in the unsaturated state were analyzed using weathered granite soil, which is typically distributed in mountainous areas in Korea. Four samples were prepared in which the compositions of the fine contents of weathered granite soil were 0%, 10%, 20%, and 30%, and a soil characteristic curve test was performed on the samples. In the coefficient prediction method, the widely applied van Genuchten model was used to analyze the air entry value and parameter values according to the fine content of weathered granite soil in the range of the drying process. As a result, a correlation between the fine content in the weathered granite soil and the air entrainment value and parameter values was identified.

Effectiveness and characteristics of atmospheric CO2 removal in croplands via enhanced weathering of industrial Ca-rich silicate byproducts

Enhanced weathering of industrial Ca-rich silicate byproducts in croplands is potentially profitable for large-scale atmospheric CO2 removal; during the weathering process, CO2 dissolves to form HCO3− and CO32− in alkaline soil pore water, which eventually flows into the ocean. However, the effectiveness of such systems is still in doubt, owing to the unrealistic models used for prediction and the insufficient consideration of the dynamic influences of soils on fluid chemistry. We determined the effectiveness of such systems for atmospheric CO2 removal, along with their characteristics, through a set of batch- and flow-through-type laboratory experiments, using andosol and decomposed granite soil as agricultural and non-agricultural soils, respectively, and Portland cement, steelmaking slag, and coal fly ash as industrial byproducts. The results of the batch-type experiments demonstrated that agricultural soils were suitable for CO2 removal, owing to their moderately high pH and Ca concentrations in pore water that prevented intensive calcium carbonate precipitation. The flow-through experiments demonstrated that a higher Ca-content byproduct can have a large atmospheric CO2 removal capacity. However, the magnitude of CO2 removal and its time-dependent behavior were difficult to predict because they were not in conjunction with the changes in the average pH value. This indicated that the diffusive transport of CO2 from the atmosphere-soil interface to deeper soils was more complex than expected. Maximizing CO2 removal requires a better understanding of the diffusive transport of CO2 through gas-filled pore spaces, created by unsteady-state air–water two-phase flow, due to intermittent rainfall.