Clay Soil Research Articles

Enhancing clay soil reinforcement using MICP-BIN method with biochar-induced nucleation

The microbially induced carbonate precipitation (MICP) method has gained extensive use in the realm of soil stabilisation. This study presents a novel microbial solidification technique known as the biochar-induced nucleation (MICP-BIN) method for reinforcing clay soil. Corn stover biochar was employed as an auxiliary material, mixed with dry clay powder, and subsequently reinforced using the MICP technique. Direct shear tests, drying experiments, X-ray diffraction, and scanning electron microscopy were also conducted to investigate the efficacy of the MICP-BIN method. Compared with that of the remoulded soil, the shear strength of the treated soil exhibited a substantial increase of 22.4%, the CaCO3 content increased by 30%, and the shear strength improved by 389.5%. Similarly, the internal friction angle exhibited increases of 22.7% and 405.2%, while the cohesion showed improvements of 9.4% and 344.3%, respectively. The MICP-BIN method is found to increase suction for a given water content. Furthermore, biochar-amended soil possesses highest water-retention ability (especially at lower suction magnitude), followed by MICP-amended soil, MICP-BIN-amended soil, and untreated soil. This study demonstrated the promising results achieved by combining biochar and the MICP-BIN technique, providing a novel approach for reinforcing soft ground.

Utilization of cement deep mixing pile for soft soil foundation: a malaysian case study

Cement deep mixing piles, as representatives of deep mixing technology, are mature and widely applied. However, effective application cases of cement deep mixing piles are relatively scarce in countries like Malaysia in Southeast Asia. In this paper, the application of cement deep mixing pile reinforcement in Malaysia is presented. Solidifying material was selected for deep mixing piles based on the soil conditions using unconfined compressive strength (UCS) tests. The relationship between the strength of deep mixing piles on-site and soil properties (type, organic matter content, and ion content) was analyzed. And a quality evaluation of the deep mixing piles in the project is conducted based on Kolmogorov-Smirnov (K-S) tests and relevant standards. Results show that fly ash cement is suitable as a solidifying agent for acidic soil layers containing organic matter in the local area. The strength of piles is significantly related to the soil condition. The UCS of cement mixing piles in silty clay and peat soils is smaller than clay. The overall correlation between organic matter content in the soil and UCS is negative, particularly when the organic matter content ranges from 10% to 14%, resulting in a significant drop in UCS. The bilateral significance probability is greater than 0.05 in K-S test, indicating that the UCS results in the projectconform to a normal distribution. Additionally, the evaluation of the overall quality of the mixing piles aligns with the requirements in the Japanese standard “Manual of Deep Mixing Construction Technology for Harbors and Airports” and the Chinese standard “Technical Code for Building Foundation Detection”.

Antioxidant Compound of Curcuma mangga Val. with Variation in Rhizome Parts and Soil Types

The scientific name of Curcuma mangga Val. (CM), that is commonly known as temu mangga, contains polyphenols, categorized as antioxidant compounds. These antioxidant compounds can neutralize free radicals. The study aims to determine the influence of rhizome parts and soil types on the antioxidant properties of CM. The research stages include sorting, peeling, washing, blanching, drying, and compositional analysis (antioxidant activity, total phenolic, flavonoid, andtannin). The study utilized a Completely Randomized Design (CRD) with rhizome parts (main, 1 tiller) and soil types (clay, lime, and sand) as variables. Both rhizome part and soil type have significant effects on the antioxidant activity and antioxidant compounds of CM. The chosen CM, specifically the main rhizome with clay soil type, exhibits an antioxidant activity of 82.50% RSA, total phenolic of 647.50 mg GAE/100 g db, flavonoids of 620.2 mg QE/100 g db (dry basis), andtannins of 167.07 mg CE/100 g db.

Risk for nitrogen leaching after application of solid manure in autumn differs between manure types

Manure application performed in autumn requires regulation due to the risk of nitrogen (N) leaching during winter. On the other hand, application of manure in spring can pose some practical problems depending on the risk for N immobilization and the difficulty in ploughing heavy clay soils during this time of year. The risk for leaching is likely to differ between different soil texture and manure characteristics. In this study, we sought to estimate the risk for nitrogen leaching depending on the carbon/nitrogen ratio (C/N) of the manure, time for manure application, and soil type. We combined 3-year lysimeter experiments with 2-year field plot experiments and laboratory soil incubations and compared results with those from an empirical model. We compared effects of manure application on two soils (silty clay and loamy sand) and solid manures with different representing C/N ratios. In incubations, only manure with a C/N-ratio below 14 contributed with significant amounts of leachable N during the first months after application. In the lysimeter study, N leaching was unaffected by the timing of the application of the manure with C/N-ratio 18. However, regarding manure with C/N-ratio 10, N leaching was elevated with 10–15 kg N per ha after manure application in October compared to November and March on both soil types. The mineral N analyses from soil profiles in the field experiments showed a similar pattern, however, the increase was higher on the loamy sand compared to the silty clay. The ammonia emissions did not differ between manure types, but were on average 24% of applied NH4-N after application in October when air temperature was on average 12°C compared to only 3% of applied NH4-N in November and March when air temperature was on average 5°C. Similar to lysimeter results, the modelled N leaching was higher the earlier the manure application occurred in autumn. However, the model also predicted increased leaching for the manure with a high C/N-ratio, and a smaller effect on leaching on clay soil. Considering this, the model calculations overestimated the leaching effects from manure with a high C/N-ratio and underestimated the leaching effects on clay soil.

Estimation of Cation Exchange Capacity for Low-Activity Clay Soil Fractions Using Experimental Data from South China

The cation exchange capacity (CEC) of the clay fraction (<2 μm), denoted as CECclay, serves as a crucial indicator for identifying low-activity clay (LAC) soils and is an essential criterion in soil classification. Traditional methods of estimating CECclay, such as dividing the whole-soil CEC (CECsoil) by the clay content, can be problematic due to biases introduced by soil organic matter and different types of clay minerals. To address this issue, we introduced a soil pedotransfer functions (PTFs) approach to predict CECclay from CECsoil using experimental soil data. We conducted a study on 122 pedons in South China, focusing on highly weathered and strongly leached soils. Samples from the B horizon were used, and eight models and PTFs (four machine learning methods, multiple linear regression (MLR) and three PTFs from publication) were evaluated for their predictive performance. Four covariate datasets were combined based on available soil data and environmental variables and various parameters for machine learning techniques including an artificial neural network, a deep belief network, support vector regression and random forest were optimized. The results, based on 10-fold cross-validation, showed that the simple division of CECsoil by clay content led to significant overestimation of CECclay, with a mean error of 14.42 cmol(+) kg−1. MLR produced the most accurate predictions, with an R2 of 0.63–0.71 and root mean squared errors (RMSE) of 3.21–3.64 cmol(+) kg−1. The incorporation of environmental variables improved the accuracy by 2–10%. A linear model was fitted to enhance the current calculation method, resulting in the equation: CECclay = 15.31 + 15.90 × (CECsoil/Clay), with an R2 of 0.41 and RMSE of 4.48 cmol(+) kg−1. Therefore, given limited soil data, the MLR PTFs with explicit equations were recommended for predicting the CECclay of B horizons in humid subtropical regions.

Impact of Wetting and Drying Cycles on the Hydromechanical Properties of Soil and Implications on Slope Stability

The soil-based infrastructure is the backbone of the global economy, connecting people, enhancing quality of life, and promoting health and safety. However, its vulnerabilities are becoming apparent due to climate change, mainly through frequent wetting and drying (wd) cycles. Despite few studies in the past, research showing the stability of flood embankments in the long term, incorporating the impact of wetting and drying cycles on the hydromechanical characteristics of soil, is scarce. This study aimed to assess the impact of controlled wd cycles on the hydromechanical properties of clay and silty sand soils and its implications for the stability of a typical flood embankment. Volumetric changes were monitored during the wd cycles. The soil water characteristic curve (SWCC), saturated hydraulic conductivity (ksat), effective cohesion (c′), and effective angle of internal friction (ϕ′) were measured at 1 and 10 wd cycles. The results indicated that the 10 wd cycles decreased the saturated moisture content and resulted in a flatter SWCC compared to the 1 wd cycle for clayey soil. The ksat value was also significantly higher at 10 wd cycles than 1 wd cycle for clayey soil. An insignificant difference was found in both the SWCC and ksat at 1 and 10 wd cycles for silty sand soil. The ϕ′ value for the clayey soil decreased from 28.5 to 20.1 as the wd cycles increased from 1 to 10, while c′ remained unchanged at 10 kN/m2. On the other hand, for the silty sand soil, ϕ′ increased from 34.6 to 37.5 with an increase in wd cycles from 1 to 10, and c′ remained constant at 1 kN/m2. Numerical modelling of transient water flow coupled with a slope stability analysis revealed that the stability of a flood embankment depends on the evolution of soil hydromechanical properties due to wd cycles and the duration of flooding. These findings underscore the need for proactive measures to mitigate landslide risks in regions prone to frequent wd cycles, thereby ensuring the safety and resilience of slopes and associated infrastructure.

Stabilization Of Clay Soil With Rice Husk Ash And Cement

Stabilization Of Clay Soil With Rice Husk Ash And Cement

Soil quality index to access the impacts of long‐term vinasse application in sugarcane areas

AbstractSoil quality index (SQI) helps quantify management practices impacts on the soil, providing information for producers in decision‐making. Through evaluation in sugarcane areas, soil indicators were used to develop SQI to access and quantify the impacts of long‐term vinasse application on the soil. The treatments consisted of two soil types: clayey (490 g kg−1 clay) and sandy (80 g kg−1 clay) and two conditions: with (70 m3 ha−1 year−1) and without vinasse application for 10 years. Soil samples were collected in the 0‐ to 10‐cm, 10‐ to 20‐cm, and 20‐ to 30‐cm layers in each treatment. Four soil functions were developed to calculate SQI: root environment quality (REQ), air/water ratio (AWR), soil chemical quality (SCQ), and soil tolerance to erosion (STE). Twelve soil indicators related to soil fertility and aggregation/structure were used. The long‐term vinasse application increased water storage (32%–58% of soil porosity), sum of bases (11–19 mmolc dm−3) and aggregate stability index (41% vs. 78%) compared to without vinasse treatment in sandy soil. In the clayey soil, vinasse increased (p < 0.05) the REQ, SCQ, and STE functions by 10%, 14%, and 13%, respectively, besides not affecting AWR. The long‐term application of vinasse promoted greater benefits, proportionally, in the sandy soil, with increments (p < 0.05) of 30% in AWR, 25% in SCQ, and 27% in STE. According to the SQI, long‐term vinasse application increased the capacity of the clay soil to perform its functions by 8%, while it increased to the sandy soil was 22%.

Impact of winter conditions on wind erosion susceptibility of clay soils

Impact of winter conditions on wind erosion susceptibility of clay soils

A contribution to the study of phosphate’s effects on calcareous soils to be stabilized with lime and natural pozzolana

When investigating the potential use of lime and natural pozzolana for subgrade soils containing phosphate, especially on agricultural lands, the effectiveness of these traditional binders needs to be assessed because of the possible deleterious effect of phosphates anions. This paper addresses this question using the problematic marly soil of Medea which was deliberately contaminated with a common fertilizer mono ammonium phosphate (0, 2, 4 and 6% by dry weight) and then stabilized with lime and/or natural pozzolana (0, 8%),(0, 20%) by dry weight respectively. Micro and macrostructural changes of these mixtures were studied under X-Ray diffraction test and Scanning electron microscope imaging. Variations of pH levels on a 90 days period, Atterberg limits between 1 to 30 days of curing, normal Proctor parameters, immediate bearing index at optimum moisture were also carried out. Overall, the results indicate that the uncontaminated marly clay soil wasn’t very reactive to lime stabilization even with 8% lime and it required the addition of natural pozzolana with lime to exhibit some improvements. Aside from that, phosphates proved to be deleterious for stabilizing marly clay of Medea producing considerable impact on all the results. It was also shown that calcite present in the soil can interfere with the employed stabilization technique.

Evaluation of the Changes in the Strength of Clay Reinforced with Basalt Fiber Using Artificial Neural Network Model

In this research, the impact of basalt fiber reinforcement on the unconfined compressive strength of clay soils was experimentally analyzed, and the collected data were utilized in an artificial neural network (ANN) to predict the unconfined compressive strength based on the basalt fiber reinforcement ratio and length. For this purpose, two different lengths of basalt fiber (6 mm and 12 mm) were added to unreinforced bentonite clay at ratios of 0%, 1%, 2%, 3%, 4%, and 5%, and unconfined compressive tests were performed on the prepared reinforced clay samples to determine the unconfined compressive strength (qu) values. The evaluation of the obtained experimental results was carried out by creating ANN models. To validate the prediction capabilities of the ANN, a comparative analysis was performed using linear regression, support vector machines, and Gaussian process regression models. Ultimately, a five-fold cross-validation technique was employed to objectively evaluate the overall performance of the model. The evaluations revealed that the ANN model predictions using data obtained from experimental studies showed the highest accuracy and were in close agreement with the experimental results.

Using stem water potential derived from continuous reading sensors for irrigation scheduling: nectarine as a test case

AbstractWe investigated on-site soil and plant based sensors translated to stem water potential for nectarine orchard irrigation control on heavy clay soil. Irrigation targeted predetermined stem water potential (SWP) thresholds for each phenological stage. Sensors were compared to SWP in six trees in a drying and wetting plot where irrigation was withheld periodically, allowing SWP to reach moderate water stress. Other sensor readings were regressed on SWP for those times, and the regressions were used for irrigation scheduling. The latter kept stage I and III SWP at ~ − 0.9 MPa, and moderate water stress in stage II (SWP ~ − 1.5 MPa). Weekly adjustments were made according to the thresholds. Results showed that tensiometers could be used for stages I and III, as they were very sensitive. However, when stress was applied soil water tension exceeded tensiometer range at 30 cm depth.Soil water content sensors had slower responses than the others, so they might be difficult to use for precise irrigation in heavy soils. Dendrometers responded quickly and therefore might be more useful for management even in moderate water stress, even with their sensitivity to climatic conditions. Analysis showed to maintain SWP within ± 0.1 MPa, 2 tensiometers, 10 soil water content sensors and 7 dendrometers stations are needed. Signal-to-noise (SNR) ranks were SWP > 30 cm tensiometers > 60 cm tensiometers > dendrometers > 30 cm soil water content > 60 cm soil water content sensors for the full season. Nonetheless, in some stages tensiometer SNR was greater than that of SWP.

Formulation and Implicit Numerical Integration of a Kinematic Hardening Model for Unsaturated Soils

ABSTRACTCurrently, our understanding of material‐scale deterioration resulting from meteorologically induced variations in pore water pressure and its significant impact on infrastructure slopes is limited. To bridge this knowledge gap, we have developed an extended kinematic hardening constitutive model for unsaturated soils that refines our understanding of weather‐driven deterioration mechanisms in heterogeneous clay soils. This model has the capability of predicting the irrecoverable degradation of strength and stiffness that has been shown to occur when soils undergo wetting and drying cycles. The model is equipped with a fully coupled and hysteretic water retention curve and a hysteretic loading–collapse curve and has the capability to predict the irrecoverable degradation of strength and stiffness that occurs during cyclic loading of soils. Here, we employ a fully implicit stress integration technique and give particular emphasis to deriving a consistent tangent operator, which includes the linearisation of the retention curve. The proposed algorithm is evaluated for efficiency and performance by simulating various stress and strain‐driven triaxial paths, and the accuracy of the integration technique is evaluated through the use of convergence curves.

Biostimulant potential of two agrochemical tolerant microalgae isolated from subtropical clay soil

Biostimulant potential of two agrochemical tolerant microalgae isolated from subtropical clay soil

Ultimate Bearing Capacity of Clay Soils Determined Using Finite Element Analysis and Derivative-based Cubic Regression

Ultimate Bearing Capacity of Clay Soils Determined Using Finite Element Analysis and Derivative-based Cubic Regression

The Effect of Varying Compaction Levels on Soil Dynamic Properties and the Growth of Canola (Brassica napus L.)

Extremely low field emergence rates for canola are primarily attributed to soil compaction from field traffic during and after planting. This study aimed to determine the critical compaction level for canola emergence across different soil types. A laboratory experiment was conducted using sandy loam, silt clay, and clay soils, compacted to five levels (zero to four) using Proctor hammer drops after sowing canola (Brassica napus L.). The lab results were validated through two years of field experiments in sandy loam, applying four compaction levels (zero to three) using a tractor. Soil properties (bulk density and surface resistance) and canola growth parameters (plant emergence rate, count, height, and above-ground biomass) were measured. Zero compaction resulted in lower bulk density and surface resistance across all soil types. Laboratory results showed maximum emergence rates of 95% for sandy loam, 100% for silt clay, and 60% for clay, while field emergence rates were 63% and 87.59% in the first and second years, respectively, both at zero compaction. Recommendations include light or no compaction for sandy loam, and zero compaction for silt clay, while clay soil did not achieve the 80% emergence target at any compaction level. These results can assist agricultural producers in optimizing their seeding equipment setup and managing field traffic for canola production.

Assessment of Waterlogging and Mitigation Strategies for Alanda Micro Watershed Using Remote Sensing in Akola District of Vidarbha Region, India

The socio-economic progress of Vidarbha, where 89% of the land is used for rainfed farming, is significantly influenced by water resources. Unfortunately, waterlogging, driven by insufficient drainage and erratic weather conditions, poses serious challenges to agricultural productivity and soil health. The Alanda micro watershed in Barshitakli tehsil, Akola district, Vidarbha region of Maharashtra, features hard basaltic terrain and clay soils primarily used for agriculture. Poorly drained soils have caused waterlogging and salinization, highlighting the need for assessment of mitigation measures for the waterlogging to improve agricultural productivity and address climate change impacts. Waterlogging can be effectively identified through remote sensing techniques like NDWI, NDMI and NDVI, using high-resolution Landsat 8 imagery processed in ArcGIS 10.8. These methods facilitate the analysis and management of waterlogged areas, which is critical for improving agricultural output. The NDVI, NDWI and NDMI maps of the Alanda micro watershed highlight vegetation health, moisture levels and waterlogging potential, with the northern regions showing higher moisture and increased waterlogging risk. Mitigating waterlogging in the area requires the implementation of efficient drainage systems, soil improvement through organic matter and deep tillage and precise water management practices, including levelling fields to prevent water accumulation and using drought-resistant crops.

Load-bearing characteristics of surface conductor in deepwater gas hydrate formations

The surface conductor is the first structural casing in deepwater natural gas hydrate (NGH) development, bearing the top load while suspending the casings of various layers. NGH decomposition leads to formation settlement, changing the mechanical properties of the formation and reducing the bearing capacity of the surface conductor, threatening the safety and stability of the wellhead. Understanding the bearing characteristics of the surface conductor in the hydrate formation can guide the safe drilling operation in the field. By introducing the negative skin friction theory of pile foundations and based on conventional bearing capacity models, a method for calculating the bearing capacity of surface conductors in NGH formations was developed. Using an NGH drilling simulation apparatus, the accuracy of the bearing capacity theoretical model was verified, empirical coefficients under different conditions were obtained, and the influence of soil parameters, hydrate saturation, and decomposition temperature on the bearing capacity of surface conductors was quantified. The results indicated that compared to clay, sandy soils have higher porosity and significantly weakened strength after the decomposition of NGH; when the hydrate saturation in the formation is 20%, the reduction in bearing capacity of the surface conductor in sand exceeds 30%, and in clay soils, it decreases by 25% after complete decomposition of NGH; as the hydrate saturation increases, the reduction in the bearing capacity of surface conductors after decomposition becomes more significant. Verified through Experimentation, the error of the hydrate-bearing strata-bearing capacity model is around 10%. For short-term test production operations of NGH in water, the design depth for surface conductors is around 100 meters. These research results can provide a scientific theoretical basis for the design of conductor depth below the mud， and reduce operational risks.

Effect of Testing Mechanisms on the Load-Strain-Time Behavior of Geosynthetic Reinforcements

Abstract This study compares how geosynthetics behave under load, under strain, and over time when subjected to confined tensile tests in soil, employing two commonly used mechanisms in research. One test type simulates a reinforced layer, where tensile loads are indirectly applied to the geosynthetic via stresses transferred from the soil. In contrast, the other test applies tensile loads directly to the geosynthetic material using clamps while under soil confinement. The objective is to elucidate how these testing mechanisms might yield differing in-soil tensile characteristics for different geosynthetics. The study involved conducting load-strain-time tests on samples of nonwoven and woven geotextiles, as well as a geogrid, under varying sustained loads over a 120-h period within a sand clay soil providing soil confinement to geosynthetics at different surcharge levels. The results suggest that soil confinement plays a significant role in shaping the load-strain-time behavior of geosynthetics. Furthermore, it was noted that the impact of testing mechanisms on this behavior is contingent upon the type and stiffness of the geosynthetics, as well as their interaction with the confining soil. In general, in-soil tests in which tensile loads are mobilized by geosynthetics and transferred from the soil provide more confident results for better simulating operation conditions. Tests that directly apply tensile loads to the geosynthetic while maintaining stationary soil confinement may yield misleading results, especially for geosynthetics that have poor interaction with the soil.

Challenges Experienced by Teachers when Integrating Indigenous Knowledge Systems in Natural Sciences Practical Work

This study explored what challenges teachers experienced when integrating indigenous knowledge systems (IKS), which are culture specific, into practical work in natural sciences classrooms with diverse learners. Using an exploratory qualitative case study based on an interpretive paradigm, three natural sciences teachers and two subject advisors were purposively selected from the Harry Gwala district in the KwaZulu–Natal province of South Africa. Semi-structured interviews, a focus group interview and practical work lesson observations were used to collect data that were analysed using thematic content analysis. The findings show that when indigenous knowledge was integrated with practical work, real-life activities were simulated in the classrooms. The introduction of real-life situations and IKS-based practical activities invited IKS-based learner behaviour. When simulating real-life practices, the learners’ socio-cultural beliefs became manifest. It was reported that learners assigned traditional gender roles for the practical work activities. Recent initiates into adulthood did not participate in activities that included the use of open fires because it was forbidden in their culture. Learners were also not willing to work with clay soil based on the belief that it attracted goblins, despite evidence showing its use in the building of huts and making of pots. Furthermore, teachers recognised the need to manage the conflicts and controversies that might result from integrating IKS into practical work. The study recommends education districts to establish contextualised resource centres for IKS integration that take into account the socio-cultural beliefs of local learners as a way to support the teachers.