Soil Stabilization Research Articles

Utilization of waste materials for soil stabilization: A comprehensive review

Soil stabilization, is a crucial aspect of civil engineering, entails the modification of soil properties to meet specific engineering standards. This is conventionally achieved through compaction and the incorporation of stabilizing agents or admixtures. Lime and cement have been predominant choices for soil stabilization, demonstrating effectiveness in altering soil properties. However, recent research has unveiled a notable shift towards the utilization of waste materials, such as fly ash and rice husk ash, for soil stabilization purposes. These waste materials, when used alone or in conjunction with lime or cement, have shown promise in achieving the desired engineering outcomes. The literature review conducted for this purpose delves into the existing body of knowledge on the utilization of waste materials in soil stabilization. Emphasizing their potential benefits, the review explores the effectiveness of these materials in altering soil properties and meeting engineering specifications. By investigating alternative stabilizing agents derived from waste materials, this research contributes to a sustainable approach in soil engineering practices. The findings presented in this paper shed light on the potential of waste materials for soil stabilization, offering a viable solution for waste disposal while addressing environmental concerns associated with traditional stabilizers.

Analisis Social Return on Investment (SROI) Program CSR Pemanfaatan Limbah Fly Ash dan Bottom Ash (FABA) PT PLN Nusantara Power UP Pacitan

This research presents an evaluation of the implementation of the Corporate Social Responsibility programme based on the use of Fly Ash and Bottom Ash (FABA) waste. The form of programme implementation is the use of coal combustion waste to make products such as bricks and paving blocks. The products are used in the construction of livable houses, village road casting and soil stabilisation in several areas of Pacitan Regency, East Java. This research uses a qualitative descriptive approach by examining the social and economic impacts on local communities through six stages of Social Return on Investment (SROI) analysis. The measured social benefits were greater than the investment with a ratio of 2.4:1. This means that for every IDR 1 invested, IDR 2.4 benefits were realised. This shows that the programme has the potential for economic, social and environmental sustainability.

Effects of Land Use Change on Soil Aggregate Stability and Erodibility in the Karst Region of Southwest China

Differences in land use type and chronological age affect soil properties and plant community characteristics, which may influence soil structural stability and erodibility. However, knowledge on the effects of soil physicochemical properties on soil aggregate stability and erodibility at different land use years is limited. This study selected five land use types: corn field (Year 38th-y), corn intercropped with cabbage field (Year 38th-y + b), fruit and meridian forest (Year 6th-jgl), naturally restored vegetation (Year 6th-zr), and artificial forest (Year 7th-rgl) in the karst landscape of the Chishui River Basin in Yunnan Province. We aimed to identify the influencing factors of soil stability and erodibility under different land use time series. The results indicated that the mean weight diameter (MWD), the geometric mean diameter (GMD), and soil structural stability index (SSI values) were highest in Y6th-zr and lowest in Y7th-rgl. Conversely, the erodibility K value was lowest in Y6th-zr, suggesting that the soil structure in Y6th-zr exhibited greater stability, whereas soil stability in Y7th-rgl was lower. Redundancy and throughput analyses revealed that organic carbon and water-stable aggregates > 2.0 mm content had higher vector values. Soil bulk density, total nitrogen, organic carbon, and soil texture content were the main factors contributing to soil stability variation (0.338–0.646). Additionally, total nitrogen, organic carbon, total phosphorus, and soil texture content drove the variation in K values (0.15–1.311). Natural vegetation restoration measures can enhance soil structure to a certain extent. These findings highlight changes in soil aggregate stability and erodibility over different land use durations. The research results have important theoretical and practical significance for understanding the differences in soil erosion and soil restoration under different land use patterns in the karst landscapes of southwest China.

Laboratory investigation on static and dynamic properties, durability, and microscopic structure of Nano-SiO2 and polypropylene fiber cemented soil under coupled seawater corrosion and cyclic loading

Cemented soils in coastal harbors are susceptible to adverse factors such as seawater corrosion and cyclic dynamic loading, which may consequently reduce their stability and durability. In recent years, Nano-SiO2(NS) has been widely used to enhance the mechanical properties of cemented soil. However, this enhancement may potentially lead to a reduction in ductility. Conversely, polypropylene fibers (PP) have attracted widespread attention for their potential to enhance the ductility of cemented soils, but their ability to improve the strength of cemented soils is limited. To address these issues, this study focused on utilizing five different nano-dosages combined with four different fiber dosages to enhance cemented soils. These enhanced soils were then subjected to curing periods of 7, 28, and 60 days in seawater environments. The study employed various tests including unconfined compressive strength tests (UCS), uniaxial cyclic loading tests, scanning electron microscopy tests (SEM), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR) to investigate the potential impacts of these additives on durability, strength, corrosion resistance, and microstructure evolution. The results of the study indicate that seawater corrosion and cyclic loading contribute to a reduction in the stability of cemented soils. However, the addition of NS and PP effectively enhances the compressive strength and durability of these soils. The optimal combination ratio is achieved when the dosages of NS and PP are 3.6 % and 0.8 %, respectively. In this case, the growth rate of unconfined compressive strength of cemented soils surpasses the sum of each individual dosage, increasing by 137.7 %, 245.6 %, and 235.3 % after 7, 28, and 60 days of curing, respectively. Furthermore, the growth rate of PP on the compressive strength of cemented soils remains largely unaffected by seawater corrosion. The optimal composite dosage of cemented soils effectively mitigates the increase in porosity caused by seawater corrosion. C-S-H enhances the mechanical interlocking between hydration products and PP by encapsulating PP, reducing energy transfer losses in cemented soils, and increasing their dynamic modulus. The volcanic ash reaction and nucleation effect of NS further enhance this effect, and their combined use significantly improves the seawater corrosion resistance of cemented soils.

STUDY ON ENGINEERING PROPERTIES OF SOIL USING STONE DUST AND BAGASSE ASH

In the discipline of civil engineering, soil stabilization is the process of enhancing and improving the engineering qualities of soil so that it can support large loads without failing. The safe and efficient disposal of waste material without causing harm to society is a significant concern in a well-managed ecosystem. Utilizing solid waste products to stabilize soil has become more popular recently as a successful way to manage trash from many sectors. This paper reviews the usage of various solid waste items that have been applied to stabilize soft soils. However, there are numerous approaches and strategies for stabilizing this soil. This research offers a method for stabilizing soft soil using waste products. An investigation into the stabilizing potential of bagasse ash and sisal fiber for highly compressible clayey soil has been prompted by the rising expense of building traditional stabilizers and the necessity of inexpensively consuming industrial and agricultural wastes for value trade. There is a growing demand for sustainable construction, which is why recent research has concentrated on sustainable resource consumption trends. We can employ natural and biodegradable resources, as well as waste products, to obtain. This study was a large-scale laboratory experiment to explore the use of natural fibers, industrial waste, and agricultural waste to improve the engineering qualities of moderately compressible clay. The purpose of this study was to determine whether Stone Dust and Bagasse Ash were suitable for stabilizing clayey soil. The results of testing for consistency limits, maximum dry density, optimal moisture content, UCS, and (soaked) CBR were obtained using percentages of 10%, 15%, and 20% by weight of dry soil for Bagasse Ash and 6%, 8%, and 10% for Stone Dust. In this work, expansive soil was stabilized using Stone Dust and Bagasse Ash. Bagasse Ash was fixed at 15%, after that Stone Dust was changed to 3%, 6%, and 9%. Key Words: Compaction test, CBR, UCS, Stone Dust, Bagasse Ash

Mechanisms of enhancing MgO for stabilization/solidification of Pb-contaminated red clay through CO2 sequestration

Pb-contaminated soil poses significant environmental and health risks as well as soil stability issues. Research on sandy soils highlights CO2-enhanced reactive MgO as a promising solution for improving the solidification of Pb-contaminated soils. However, carbonation effects can differ markedly between soil types owing to varying soil properties. In this study, we evaluated the effects of CO2-enhanced reactive MgO on the engineering and environmental characteristics of Pb-contaminated red clay and explored its mechanism of carbonation solidification. The results showed that CO2-enhanced reactive MgO increased the strength of Pb-contaminated red clay to over 3 MPa within 1 h, which was approximately 25 times the strength of untreated soil (0.2 MPa) and significantly higher than that of reactive MgO-treated, uncarbonated soil (0.8 MPa). The pH of the carbonated soil (9–10) facilitated Pb2+ immobilization, and the increase over the initial parameter elevated the electrical conductivity value. Moreover, CO2-enhanced reactive MgO reduced the Pb2+ leaching concentration to below 0.1 mg/L, even at high Pb concentrations (10,000 mg/kg). Pb2+ transformed into lead carbonates during the carbonation process, with the hydrated magnesium carbonates forming a dense internal structure. This solidification mechanism included chemical precipitation, physical adsorption, and encapsulation. Notably, the carbonation time should be controlled within 1 h to prevent soil expansion. Together, these findings support the potential of CO2-enhanced reactive MgO for efficient and low-carbon application in the solidification of Pb-contaminated red clay.

Mechanical performance of eco-friendly self-compacting concrete (SCC) mixtures and two-way slabs partially containing cement kiln dust as cement replacement and internally reinforced with waste plastic mesh

A large quantity of cement kiln dust (CKD) is produced annually during the production of Portland cement. The majority of the produced CKD remains unused except in specific cases related to soil stabilization projects. The current research investigates the production of self-compacting concrete (SCC) mixtures, in which CKD is used as a substitute for cement in different weight proportions, 3 %, 6 %, 9 %, 12 %, and 15 %. The hardened mechanical properties of SCC, such as compressive strength, splitting tensile strength, and flexural strength, as well as the fresh state characteristics (i.e., slump flow diameter, T500, V-funnel, and L-box tests), were recorded and compared with the control mixture which was entirely cast using cement. Results revealed that with an increase in the CKD content beyond 6 %, the slump flow diameter of SCC mixtures significantly decreased. Also, the increase ratios in the V-Funnel flow time for self-compacting concrete mixtures, when replacing cement with CKD ratios of 3 %, 6 %, 9 %, 12 %, and 15 %, were 13.3 %, 30 %, 46 %, 58 %, and 66.7 % respectively, compared with the reference mixture. Additionally, the impact behavior of two-way SCC slabs cast using CKD ratios ranging from 3 to 15 % and internally strengthened using various patterns of recycled plastic mesh was investigated. Strengthening the SCC slabs using two layers of recycled plastic grids proved to be effective in preventing the projectile from penetrating the whole thickness of the SCC slabs, regardless of the CKD content.

Research on the enhancement material and culture method of soil aggregates composed of feldspathic sandstone and sand

The Mu Us Sandy Land is a region characterized by wind-blown sand and soil erosion in northern China. To enhance the soil quality of this area, various organic materials were incorporated into the mixed soil at a volume ratio of 1:2 for feldspathic sandstone to sand. Culture was conducted in the field and under constant temperature conditions in laboratory culture chambers. Four treatments were established in the experiment, each calculated based on weight ratio and controlled (with no organic material added, CK); single application of straw (5% straw, P1); single application of biochar (5% biochar, P2); combined application of biochar and straw (5% biochar + 5% straw, P3). After 90 days of culture, soil samples were collected for analysis of various indicators such as soil aggregate particle size distribution, water stability of soil aggregates, mean weight diameter, mean geometric diameter, and fractal dimension using dry sieving and wet sieving methods. The objective is to establish a scientific basis and provide technical support for addressing the challenges associated with compound soil and implementing rational fertilization measures. The research results indicate that: (1) The quantity of aggregates > 0.25 mm under different treatments follows the order CK < P1 < P2 < P3, and the differences between treatments are significant (P < 0.05); (2) Soil water stability, mean weight diameter (MWD), mean geometric diameter (GMD), and fractal dimension of soil aggregates in compound soil with different organic material additions are superior to the control, and the effect of biochar on improving soil aggregates is better than that of corn straw. The combined application of both significantly improves the effect compared to single applications. In both culture modes, under wet sieving, the P3 treatment shows the highest MWD and GMD of soil aggregates, with an increase ranging from 3.45% to 85% and 4.55% to 38.46%, respectively, compared to other treatments. (3) The trend of fractal dimension among treatments is consistent: P3 < P2 < P1 < CK, and the differences between treatments are significant (P < 0.05). Moreover, there is a good negative correlation linear equation relationship between the fractal dimension (y) and WR > 0.25 (x) of compound soil, with a correlation coefficient of up to 0.9851. In conclusion, the incorporation of organic materials can effectively enhance the proportion of macroaggregates in compound soil consisting of Feldspathic sandstone and sand, thereby improving soil stability and erosion resistance. The optimal outcome is achieved through the combined application of biochar and straw. Indoor culture proves to be more effective than field culture, while wet sieving accurately reflects the structural characteristics of compound soil under both dry and wet sieving treatments.

Design of sustainable bituminous concrete pavement with cement–treated granular layers constructed on stabilized subgrade

Purpose Designing a sustainable bituminous concrete with long-term performance is a challenging problem. In addition, strength of the subgrade has a crucial impact on pavement design. This paper aims to concentrate on subgrade soil stabilization with granite dust powder (GDP) and crumb rubber powder (CRP) to improve the engineering properties of the soil. Further design of bituminous concrete pavement with cement-treated layers in base and subbase course layers was carried out with life cycle cost analysis and life cycle assessment for 1 km of a four-lane national highway. Design/methodology/approach Subgrade soil stabilized with GDP and CRP is characterized as per Indian Standards (IS)-2720 to determine the optimum dosage. Further, the mechanistic-empirical pavement design was carried out using Indian Road Congress-37 (2018), analyzed using IITPAVE software and validated with ANSYS software. The life cycle cost analysis is carried out using the net present value method, and the life cycle assessment is performed according to the cradle-to-grave approach. Findings A soil mix comprising 10% GDP and 2.5% CRP yielded a soaked California bearing ratio value of 6.58%. In addition, the design of bituminous concrete pavement with cement-treated granular layers showed a 26.9% reduction in life cycle cost and 59.4% reduction in total carbon footprint per kilometer compared to the pavement with traditional aggregate layers. Originality/value The research on subgrade stabilization with sustainable materials like GDP and CRP incorporating mechanistic empirical pavement design, life cycle cost analysis and life cycle assessment is limited. Overall, the study recommends the use of GDP and CRP to stabilize soil for subgrade application and incorporate cement-treated granular layers, which offer economic and environmental benefits compared to traditional pavement construction.

The Effect of Adding Bamboo Leaf Ash and Cement on the Stability of Clay Soil

Subgrade soil or clay subgrade is a type of soil with very high pore water characteristics, causing problems for civil structures, both buildings and road pavements. Bamboo leaf ash contains several compounds such as silica (SiO2) at 77.24%, while cement contains several calcium oxide (CaO) compounds at 60%. Bamboo leaf ash has a high silica content which functions as a support for pozzolanic reactions with clay soil. The variations in the mixture of bamboo leaf ash and cement used are 2%, 3%, 4%, 5% and 6% for bamboo leaf ash and 20% for cement by weight of soil, with a curing time of 4 days. From the two tests that have been carried out, namely soil compaction (Standard Proctor) and Unsoaked CBR (California Bearing Ratio), the optimum values ​​obtained for soil compaction (Standard Proctor) and CBR (California Bearing Ratio) Unsoaked are in the variation of soil + cement addition of 20% + Bamboo Leaf Ash 3%. In the soil compaction test (Standard Proctor), the dry volume weight value was 1,728 gr/cm3 and the optimum water content value was 16.02%, while in the Unsoaked CBR (California Bearing Ratio) the optimum CBR percentage value was 10.25%.

Improvement of mechanical behavior of cemented soil reinforced with waste sisal fibers: An optimal selection and modification research

In response to escalating environmental concerns, this study explored the use of sisal fiber as a sustainable alternative to traditional cement or synthetic fibers for soft soil stabilization. An optimal selection test was conducted to determine the optimal sisal fiber characteristics and their impact on the mechanical performance of cemented soil. The findings indicated that incorporating sisal fibers into cemented soil inhibits crack propagation, thereby enhancing its strength and ductility. A significant improvement was achieved by incorporating optimal fiber parameters (content = 0.4 %, length = 11 mm) into the cemented-soil, the compressive strength reached 4.4 MPa (by 29.4 %). In addition, to further improve the work performance of sisal fiber-cemented soil (SFCS), alkaline and acetylation treatments were applied, respectively, to prevent volume instability and degradation of sisal fiber. The study also evaluated the effects of these modification methods on the physical properties of sisal fiber and the strength of sisal fiber-cemented soil (SFCS). The results showed that a 6 % NaOH treatment was determined to be the most effective modification method, reducing the moisture affinity of sisal fiber, improving fiber-matrix bonding, and consequently enhancing the mechanical properties of SFCS (by 18.7 %). However, it should be noted that an excessively high concentration may adversely affect fiber properties, negatively impacting the strength of SFCS (by up to 11.59 %).

Investigating the utilization of oxidized textile residue as a strengthening substance in the composition of subgrade soil for pavement construction

&lt;p&gt;The textile industry, vital in the country's industrialization and playing a crucial role in the national economy, generates solid byproducts known as textile sludge. Integrating waste into stabilized soils, along with textile sludge (TS), fly ash (FA), and asphalt additives, offers scientific, economic and sustainability benefits. This study aimed to examine the subsurface solidification technique employing sludge and two supplement additives (asphalt and fly ash additive) implemented on pavement groundwork and supporting layers. The research involved characterization tests and physical soil stabilization with TS and stabilizers (fly ash, and asphalt) at proportions of 2.5%, 5%, 7.5%, 10%, 15%, and 20% as soil additives, which were carried out experimentally. The test results highlighted the potential application of soil-textile sludge mixtures in pavement strata (support and subgrade). The inclusion of fly ash has been proven to be the most effective method for chemically stabilizing the sludge. The maximum dry density was achieved with soil containing 10% textile sludge, supplemented with 15% fly ash. This resulted in a notable increase in UCS value from 235 kN/m2 to 242 kN/m2 and an improvement in CBR value from 4.1% to 9.12%. Furthermore, the addition of 5% bitumen further enhanced the UCS value, reaching 451 kN/m2 and significantly increased the CBR value to 21.6%. Stabilizing textile sludge offers significant environmental benefits by mitigating issues associated with improper waste disposal.&lt;/p&gt;

Chemical and Mechanical Soil Stabilization Techniques for Foundations

Introduction: The geotechnical study is crucial for foundation design and herein the feasibility of stabilizing soil from Quillollaco Formation in Loja, Ecuador with quicklime. Methodology: Laboratory tests followed ASTM standards. Unaltered soil samples were extracted at depths ranging from 2,00 to 3.00 m and fed quicklime at varying percentages (13,00 to 21,00% and 3,00% for quicklime) during curing periods of 7 to 28 days. Before obtaining results, the soil was classified by primary classification. Laboratory tests included Atterberg limits, Standard Proctor, unconfined compressive strength and permeability. Results: Consequently, the results indicated that the soil is primarily clay with low plasticity. Although the addition of quicklime increases plasticity and compressive strength, the improvement is minimal and varies with dosage and cure time. Greater compaction and workability are observed with lower quicklime contents. Regarding permeability, moderate to high improvement is recorded with quicklime addition, suggesting enhanced drainage capacity. Disscusion: Stabilization of quicklime soil may improve some geomechanical properties, but its effectiveness and profitability could be limited, especially in clay soils of low plasticity. Emphasis is placed on the need to consider soil stabilization alternatives that are efficient and sustainable from economic and environmental points of view.

Soil multifunctionality increases after grazing abandonment in semiarid rangelands

Grazing by domestic animals is an economic activity that can alter the ecosystem structure and functioning of drylands. Some rangelands are experiencing a temporary or complete abandonment of grazing, but the effects of these practices on the ecology of drylands are poorly studied. Plant patches are recognized as fertility islands in drylands. Unvegetated inter-patches, far from being lifeless, harbor diverse soil microbial communities, habitually in the form of biocrusts. Here, we determined changes in plant, biocrust, and bare soil cover after grazing cessation over a 63-year period in Patagonian semiarid drylands. We also quantified, at microsite (2.25 m2) and plot (2500 m2) scales, temporal changes in soil multifunctionality by using four specific soil multifunctionality indexes associated with soil carbon, fertility, biogeochemical cycling, and stability. Our results indicate that biocrusts, although with low cover values, colonize new soil areas following grazing cessation, whereas bare soil cover increases at the expense of plants. We found that soil multifunctionality consistently increased with time since grazing cessation at the microsite scale, with biocrusts showing the highest multifunctionality values. We also observed that soil multifunctionality increased over time after grazing cessation at the plot scale, with bare soil and plants being more important than biocrusts due to their greater cover. Overall, our field study shows that the abandonment of grazing leads to a natural recovery of soil functioning in semiarid rangelands, with biocrusts and microbial communities of bare soils playing central roles, but at different spatial scales.

Description of ASTAVIT, a rapid assessment method of soil structural stability based on image recognition

Measuring soil structure stability has always been a challenge, and various approaches have been proposed, mainly related to measuring soil aggregate stability upon wetting. This paper presents a rapid and cost-effective tool for evaluating soil structural stability named ASTAVIT, which stands for Aggregate STability Assessment using VIdeo Tests. The ASTAVIT principle involves visually monitoring the spreading of aggregates. This has already been implemented in the SLAKES smartphone application (now renamed Moulder), which simplifies the measurement of soil aggregates with minimal equipment. The aim of this work was to develop a robust, adaptable, and representative enough method that can be widely used in soil science laboratories. The protocol has been modified to use a 3D-printed plate, which source file is provided with this paper, to record the immersion of up to 96 individual aggregates in water. The increase in the projected area of the aggregates during slaking is tracked using image recognition software, ImageJ. The final stability index is determined based on this area increase. Soil structural stability can be assessed within an hour using a procedure that involves placing aggregates on a plate, filming, and analyzing. This method provides an objective evaluation of soil stability in a timely manner. The amount of soil used per test is similar to that used in Le Bissonnais tests (ISO 10930), ensuring representative results. The ASTAVIT index demonstrates expected behaviors of aggregate stability, as evidenced by its correlation with other soil characteristics and its ability to differentiate between soils that have undergone different tillage practices. An indicative classification of the ASTAVIT index into four categories of soil stability, similar to the Le Bissonnais tests, is proposed. ASTAVIT is expected to facilitate a broader implementation of structural stability studies.

Appraisal of Bhatta Waste as an Admixture for the Stabilization of Fill Soil

Testing of soil and knowing its strength parameter’s is one of the basic components in construction. Testing of soil is carried out to find whether the existing soil can endure the burden of structure withheld upon it or not. In case of a weak soil, one can find difficult to pursue construction or any development project. While talking of solutions, there are many methods to improve its strength and properties: one of them which we decided to work on is ‘Appraisal of Bhatta Waste as an Admixture for the Stabilization of Fill Soil’. It’s a kind of cost effective &amp; economical means of improving soil, as the basic material required for stabilization is Bhatta waste, which is normally easily available material. The main objective of our test is to check the effectiveness of Bhatta waste on mechanical properties of filled material. The testing comprised of performing Atterberg limit, UCS, direct shear test, sieve analysis, Moisture dry density and Permeability test. The Bhatta waste passing no. 40 sieve is mixed with fill soil and testing on different proportions was carried out. Summary was prepared for explanation of engineering properties of different proportions, while further testing on higher proportions is recommended.

Iron mineral type controls organic matter stability and priming in paddy soil under anaerobic conditions

Associations of iron (hydr)oxides (FeOx) with organic carbon are vital in regulating the stability of soil organic carbon (SOC). Like SOC, FeOx is chemically dynamic in soils, particularly under anaerobic conditions. However, previous research has not clarified how the stability of FeOx (goethite versus ferrihydrite) and the formation pathway of FeOx-OC associations (adsorption versus coprecipitation) affect the stability of FeOx-bound OC and, subsequently, the priming effect (PE) under anaerobic conditions. With an aim to bridge this gap, we incubated paddy soils for 80 d under anaerobic conditions after adding free 13C-glucose, ferrihydrite- or goethite-bound 13C-glucose formed by either adsorption or coprecipitation. Compared with the free glucose addition, the FeOx-bound glucose addition increased 13CO2 production by 8%–21% but reduced 13C–CH4 production by 7%–10%. Ferrihydrite-bound glucose was mineralised more than goethite-bound glucose; this is consistent with its lower crystallinity facilitating reduction and, thus, higher OC bioavailability. Glucose induced a negative priming effect (PE) for CO2 but a positive PE for CH4, whereas FeOx-bound glucose showed the opposite trend. This may be because FeOx-bound glucose provides an energy source and electron acceptor for Fe-reducing bacteria; this promotes the dissimilating reduction of iron and combines with an aggravated microbial P limitation resulting from the FeOx input. The crystallinity of FeOx affected the amount of primed CH4 rather than its formation pathway. In conclusion, the crystallinity of FeOx controls the stability of FeOx-OC associations and the PE of SOC decomposition under anaerobic conditions.

Advancements in Soft Soil Stabilization by Employing Novel Materials through Response Surface Methodology

Stabilization using industrial by-products is presently gaining importance in the construction sector for improving the geotechnical characteristics of soft soils. The optimum dosage of stabilisers has become of great interest to experimenters in terms of improved strength, time, and economy for construction projects. This work presents the utilization of biomedical waste ash for improving the strength of soft soil. In this paper, response surface methodology (RSM) was adopted to determine the optimum combination curing period (C) and biomedical waste ash (BA) quantity for attaining the maximum unconfined compressive strength (UCS) of soft soil and to reduce the number of trial tests required. The response factors C and BA were varied from 0 to 14 days and 4% to 20%, respectively, and the experiments were conducted according to the experimental plan provided by the RSM design. Based on a Face-centred Central Composite Design (FCCCD), a mathematical equation was created for the experimental results. Analysis of variance (ANOVA) was used to determine the generated model’s significance, and the results indicated a statically significant model (p ≤ 0.05). The results revealed that the curing period imparts more influence towards strength improvement, and the optimum dosage was 19.912% BA, with curing of 14 days to yield a maximum UCS of 203.008 kPa. This optimization technique may be suggested to obtain a preliminary estimation of strength prior to stabilization.

Enzymatic Diagnostics of Soil Health of the European Part of Russia with Lead Contamination

Lead (Pb) is one of the most common environmental pollutants. Lead has an acute toxic effect on soil biotas and the enzymatic system of soils. The objective of this study is to carry out enzymatic diagnostics of soil health in the European part of Russia after Pb contamination. As a part of the simulation experiment, Pb (at maximum permissible concentrations (MPCs) of 1, 10, and 100) was used to contaminate 12 types of soils in the south and center of the European part of Russia, which differed in their physical and chemical properties. To assess soil health, the activity of oxidoreductases (catalase, dehydrogenases, and cysteine reductase) and hydrolases (invertase, urease, and phosphatase) was studied. Most enzymes were inhibited with increased Pb dosage. The most sensitive soils to Pb contamination, assessed by enzyme activity, are soils of semi-deserts and dry steppes. Cysteine reductase is considered the most sensitive enzyme to Pb contamination. The most informative indicators for Pb contamination were phosphatase, cysteine reductase, and invertase. The P (phosphatase) cycle and the redox enzyme (catalase) also have instability in Pb-contaminated soils. The C (invertase and dehydrogenases) and N (urease) cycles do not change significantly when contaminated with lead. The results of this study can be used for the diagnostics of the condition of soils in different natural areas after Pb contamination.

Engineering properties of pozzolanic cement-stabilized organic soil

In this study, the engineering properties of organic soil (OS) stabilized with pozzolanic cement (PC) were investigated. In tests, 10, 15 and 20% proportions of PC were added to organic soil. Consistency limit, Proctor, unconfined compressive strength (UCS), triaxial (TA), swelling and compressibility tests were performed on the OS stabilized with PC. The addition of PC to OS increased the maximum dry density (MDD) and optimum moisture content (OMC) values. The UCS values for the OS stabilized with PC increased up to day 56 and then there was a reduction in the UCS after day 56. The internal friction angle value increased by 26% and the cohesion intercept value increased by 86% for the OS stabilized with PC. With the increase in the cement content in the OS stabilized with PC, the UCS, internal friction angle and cohesion intercept values increased. Swelling of the OS stabilized with PC rapidly reduced up to day 10, and this reduction slowed after day 10. The compressibility of the OS stabilized with PC increased up until day 10, and this increase slowed after day 10. With an increase in the cement content in the OS stabilized with PC, swelling and compressibility values reduced. As a result of the study, it appears that pozzolanic cement is an effective stabilizer for organic soil.