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Comparative effects of olivine and sand on KOH-treated clayey soil

  • Abdelmaoula Mahamoud Tahir ORCID logo , Sedat Sert ORCID logo , Eylem Arslan ORCID logo EMAIL logo , Ertan Bol ORCID logo , Aşkın Özocak ORCID logo and İbrahim Atlı ORCID logo
Published/Copyright: August 29, 2025
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Open Geosciences
From the journal Open Geosciences Volume 17 Issue 1

Abstract

Improving the strength of clayey soils remains a key concern in geotechnical practice. This study presents a comparative investigation of the effects of olivine waste and sand grains on a clayey soil, both in the absence and presence of potassium hydroxide (KOH). The samples were tested under undrained conditions with varying curing periods and different confining pressures. Samples treated with sand or olivine showed increased strength, with sand outperforming olivine due to its higher volume. In the presence of KOH, the strength increased in both cases, with sand-treated samples showing higher values than those treated with olivine. Under a confining pressure of 100 kPa and a curing period of 90 days, strength increased by 399% with olivine and by 613% with sand. At 400 kPa confining pressure, these values reached 604% for olivine and 856% for sand. The highest cohesion (390 kPa) and internal friction angle (22.03°) were obtained in the sand added sample activated with KOH in 90 days, followed by the olivine added samples activated by KOH in 90 days with a cohesion value of 270 kPa and a friction angle of 20.56°. Mineralogical analyses were carried out to examine crystal formation resulting from the chemical reaction. The study presents extensive experimental data, highlighting the potential of olivine as an environmentally friendly material and a sustainable alternative for soil stabilization, with lower carbon emissions compared to conventional methods.

Keywords: soil stabilization; clay; olivine waste; sand; sustainability

Abbreviation

C

Clay content

CL

Low plasticity clay

EDS

Energy dispersive spectroscopy

FC

Fines content

KOH

Potassium hydroxide

LL

Liquid limit

LVDT

Linear variable differential transformer

MDD

Maximum dry unit weight

NaOH

Sodium hydroxide

NS

Natural soil used in the tests (clayey sol)

OWC

Optimum water content

PI

Plasticity index

PL

Plastic limit

SEM

Scanning electron microscopy

S-OL

The mixture of clay with olivine

S-OL-KOH

The mixture of clay with olivine activated by KOH

S-OL-1

The mixture of clay with olivine (1 day of curing)

S-OL-KOH-28

The mixture of clay with olivine activated by KOH (28 days of curing)

S-OL-KOH-56

The mixture of clay with olivine activated by KOH (56 days of curing)

S-OL-KOH-90

The mixture of clay with olivine activated by KOH (90 days of curing)

S-SA

The mixture of clay with sand

S-SA-KOH

The mixture of clay with sand activated by KOH

S-SA-1

The mixture of clay with sand (1 day of curing)

S-SA-KOH-28

The mixture of clay with sand activated by KOH (28 days of curing)

S-SA-KOH-56

The mixture of clay with sand activated by KOH (56 days of curing)

S-SA-KOH-90

The mixture of clay with sand activated by KOH (90 days of curing)

UU

Unconsolidated-undrained

XRD

X-ray diffraction

1 Introduction

In many rapidly growing urban areas, infrastructure must often be built on soft and problematic soils that pose significant risks to structural stability. These soils are particularly prone to settlement, low bearing capacity, and slope failures, which can lead to costly damage and safety hazards. As a result, improving the engineering properties of soft soils has become a critical concern in geotechnical engineering. In geotechnical engineering, improving the engineering properties of soft soils is a critical topic that contributes to mitigating soil-induced hazards arising from structural loads, such as bearing capacity failure and slope instability [1,2]. Managing these potential risks through the incorporation of different additives into soils has remained a continually evolving area of research in recent years [3,4]. As can be seen from Table 1, the commonly used materials for the stabilization are chemical agents that provide a bonding effect between soil particles, such as cement, lime, fly ash, and rice ash husk [5,6,7,8]. When the necessary optimum conditions are ensured, the use of these materials leads to the formation of cementing gels through pozzolanic reactions, thereby enhancing the strength of the soil, a well-established conclusion in the literature [9,10,11,12,13,14,15,16]. However, a critical issue associated with these traditional materials is their environmental impact: the production process generates a significant amount of carbon dioxide, contributing to climate change. Furthermore, even after application, harmful minerals may form as a result of sulfate attack, which can negatively affect the structural integrity of the soil [17,18,19,20,21,22]. That is why the search for new sustainable materials for soil treatment has gained increasing importance.

Table 1

Summary of recent studies on clayey soil stabilization using various additives, test methods applied, and key quantitative findings regarding strength, durability, and environmental performance

Reference Additive Test method(s) Key quantitative findings
Ghobadi et al. [23] Lime Unconfined compression test and pH test The study proved that 7% lime effectively stabilizes Hamedan clay, with maximum shear strength achieved at pH 9 due to enhanced cohesion and friction angle
Roy [24] Rice husk ash and cement Unconfined compression test and California bearing ratio The study proved that stabilizing high-plasticity clay with 10% RHA and 6% cement significantly improved the CBR by 106% and UCS by 90.6%
Modarres and Nosoudy [25] Coal waste and lime Unconfined compression test and California bearing ratio The study proved that combining coal waste (or its ash) with lime significantly improved the strength and CBR of clayey soil while maintaining heavy metal concentrations within safe environmental limits
Ali et al. [26] Polypropylene fiber Unconfined compression test, California bearing ratio test, and one-dimensional consolidation test The study showed that adding polypropylene fibers, especially at 0.4% content, significantly enhanced the strength and bearing capacity of expansive soil, while higher dosages (0.8%) greatly reduced swelling and compressibility, making it suitable for pavement subgrades
Malikzada et al. [27] Lime and fly ash Unconfined compression test and California bearing ratio test The study proved that fly ash, especially at 15% content, provides greater and more consistent CBR improvement than lime in alluvial subgrades, regardless of grain size
Rehman et al. [28] Lignosulphonate and quick lime Unconfined compression test The study concluded that a composite additive of lignosulphonate and lime effectively stabilized expansive soil, with optimized mix ratios tailored to construction scenarios, reducing lime use by up to 45% while improving strength, volume stability, and sustainability
Alijani Shirvani and Reza Noorzad [29] Sludge ash Unconsolidated–undrained compression test The study proved that incorporating sludge ash from wood and paper mills significantly improved the shear strength and reduced the swelling and compressibility of fat clay, making it a viable industrial byproduct for soil stabilization
Disu and Kolay [30] Fly ash and lime Unconfined compression test The study showed that a 15% fly ash–lime sludge geopolymer mix cured at elevated temperature significantly improved the strength and stiffness of kaolin clay due to enhanced gel formation and mineral crystallization
Khan et al. [31] Fly ash Unconfined compression test, California bearing ratio test, and one-dimensional consolidation test The study proved that mellowing time significantly influences the mechanical behavior of expansive clay stabilized with fly ash-based geopolymer, where longer delays reduce strength but improve deformability due to early-stage pore structure formation
Rehman et al. [32] Cement Unconfined compression test The study demonstrated significant improvements in strength and durability for use as a cost-effective and sustainable construction material in rural housing
Li et al. [33] Lime Unconfined compression test The study proved that 7% lime content is optimal for improving the durability of silty clay subgrades under seasonal freeze-thaw and wet-dry conditions, offering a cost-effective solution for cold region highways

Olivine is a silicate mafic mineral composed of magnesium and iron with a chemical formula of (Mg,Fe)2SiO4. This material, which is derived from natural igneous rocks, may provide both environmentally friendly and economically viable solutions for soil stabilization purposes. Additionally, the ability of this material to capture CO2 in the atmosphere means that this material can produce a sustainable solution. While Portland cement production emits nearly 900 kg CO₂ per ton, olivine weathering can sequester approximately 0.5–1.0  ton CO₂ per ton of mineral applied, with cement substitution strategies potentially reducing lifecycle emissions by up to 33% [34,35]. In addition to its environmental advantages, olivine presents economic feasibility as a stabilization material, with overall costs generally comparable to or lower than conventional stabilizers such as cement or lime. This makes olivine a promising alternative for sustainable and cost-effective ground improvement strategies [36]. According to Xeidakis [37], the enrichment of magnesium hydroxide in clayey soils reduces their swelling potential. The high magnesium oxide content of this material further indicates its promise for improving clayey soils. In addition, the presence of SiO2, Al2O3, and Fe2O3 compounds in the environment supports the likelihood of pozzolanic reactions, similar to those observed with cement and lime treatments. Therefore, using olivine as a binder in soils seems encouraging in terms of sustainable solutions [38].

Emmanuel et al. [39] reported that when marine clays were improved with landfill leachate and olivine, a significant enhancement in soil properties was achieved with the addition of 30% olivine by weight. They also demonstrated that the improvement was actually due to the formation of hydrated magnesium aluminate and silicate phases. The increase in shear strength, attributed to reductions in both the dry unit weight and plasticity of the clay, was found to be remarkable and has been consistently observed in several other studies [40,41,42,43]. On the other hand, the use of olivine in the presence of alkaline activators such as potassium hydroxide or sodium hydroxide has been explored by a limited number of researchers. These studies have shown that the presence of alkali accelerates chemical reactions and enhances carbonation, thereby further improving the effectiveness of olivine as a soil stabilizer. It has been shown that olivine activated with potassium hydroxide (KOH) (i.e., clay + olivine and KOH) produced varying responses depending on the curing duration, with strength reaching significantly higher levels after a 90-day curing period compared to the untreated soil [44]. In a similar study, the effect of replacing KOH with sodium hydroxide (NaOH) was investigated to assess its contribution to the carbonation reactions between olivine and clay. The findings revealed that NaOH resulted in a comparatively smaller increase in strength [45]. Potassium hydroxide (KOH) was found to be an activator, which leads to a strong interaction of potassium ions with clay minerals, which enhances pozzolanic reactions and structural rearrangement, as well as its high solubility and practical applicability under laboratory conditions. When a silty soil was treated with KOH and polypropylene fibers, reductions in optimum water content (OWC) and swelling potential were observed, while the maximum dry density and drained shear strength increased. This transformation is likely driven by the influence of potassium ions, which alter the mineral’s molecular structure [46]. In a recent study performed by the authors, it was demonstrated that olivine activated with KOH significantly enhanced the soil strength, with improvements reaching up to 521%. The formation of abundant chemical bonds was further confirmed through morphological and mineralogical analyses [43]. In this study, samples containing olivine alone and those containing KOH-activated were subjected to curing periods of 1, 14, 28, and 56 days. The results showed that substantial increases in shear strength parameters (both cohesion and internal friction angle) were observed only in the KOH-activated samples, particularly at longer curing times. In contrast, for the olivine-only samples (without KOH), the strength gains were found to be largely independent of curing duration.

This study was designed to build upon and expand the findings of a previous investigation, with the aim of exploring the underlying causes of strength improvement and evaluating the causality behind the observed results. In the first stage, samples containing 25% olivine by weight were prepared based on the previous findings. Since it had been previously determined that strength gains in samples mixed solely with olivine did not vary with curing time, a 1-day curing period was selected for this group. One of the key questions at this stage was whether the observed increase in strength in olivine-added samples was due to the introduction of particles larger than clay, raising the question: Was the strength gain merely a grain size effect? To explore this, a parallel set of samples was prepared by replacing olivine with sand of similar particle size and the same proportion by weight. Unconsolidated–undrained (UU) triaxial tests were then conducted under four different confining pressures to compare their behaviors. In the second stage of testing, KOH solution was added to the previously prepared olivine- and sand-amended samples to enhance the chemical reactivity of olivine. Based on earlier results showing that chemical reactions in these systems develop over time, these samples were subjected to extended curing periods of 28, 56, and 90 days before testing. While the difference between KOH-activated and non-activated olivine had been explored in the previous study, the focus here was to determine whether the strength gain observed in the presence of KOH was unique to olivine or could also occur with KOH-activated sand. In other words, was the improvement in strength due to the specific chemical interactions of olivine, or could a similar enhancement be achieved with sand? To answer this, samples containing 25% olivine and 25% sand (both with KOH) were prepared and cured for 28, 56, and 90 days, then tested under the same conditions as the initial group. In addition, X-ray diffraction (XRD) experiments were carried out in order to search the mineralogical changes and identify the crystalline structures formed. The results obtained were then compared to determine whether the contribution of sustainable olivine material to soil strength is truly distinctive and chemically driven. The study mainly addresses the lack of comprehensive comparative analyses between olivine and other inert materials such as sand, particularly under chemical activation conditions using KOH. Although previous research has demonstrated the potential of olivine in soil stabilization, the specific contribution of its chemical reactivity, especially in long-term curing scenarios, remains insufficiently clarified in the literature. In parallel, while much attention has been devoted to chemical stabilization techniques, some experimental findings also emphasize the role of fines content and intergranular void ratios in governing the undrained shear behavior and also the dynamic properties of soils [47,48,49]. These findings suggest that strength improvements may not be solely attributed to chemical reactions but also to changes in the granular matrix, which supports the rationale behind this study’s comparative evaluation of olivine and sand. The problem in this study aims to solve is whether the enhanced strength observed in olivine-stabilized soils is solely due to grain size replacement or is fundamentally linked to mineralogical and chemical transformation, especially under alkali activation. To fill this gap, this study investigates and contrasts the strength and mineralogical evolution of sand- and olivine-added clay samples with and without KOH activation under varying curing periods. The main objective is to determine whether the performance of olivine is unique and sustainable in the presence of KOH or if comparable results can be achieved using inert materials like sand.

2 Materials and methods

2.1 Materials

2.1.1 Soil

In this experimental study, a clay with low plasticity from Kocaeli (Türkiye) was investigated. The sampling site is shown in Figure 1. The soil samples used in the experiments were first sieved through a 4.75 mm sieve. The portion passing through the 0.425 mm sieve was then subjected to liquid limit (LL), plastic limit (PL) and pycnometer experiments. The clay used in the study consisted of 96% fine-grained material and 4% sand and was classified as low plasticity clay (CL) according to the Unified Soil Classification System [50]. The physical properties of the clay are listed in Table 2.

Figure 1 Location of the sampling site: Türkiye is highlighted on the globe (upper inset), and the enlarged map shows Kocaeli Province shaded in red (lower panel).
Figure 1

Location of the sampling site: Türkiye is highlighted on the globe (upper inset), and the enlarged map shows Kocaeli Province shaded in red (lower panel).

Table 2

Physical and index properties of natural soil (clayey soil) used in the study, along with the corresponding test standards

Component Unit Value Standard
Fines content (FC) % 96 BS 410 [51]
Clay content (C) % 8
Liquid limit (LL % 41 ASTM D4318 [52]
Plastic limit (PL % 17
Plasticity index (PI) % 24
Optimum water content (OWC % 17.50 ASTM D4647 [53]
Max. dry unit weight (MDD) kN/m3 17.83
Density g/cm3 2.70 ASTM D854 [54]

2.1.2 Olivine and sand

Olivine waste was obtained during the chromite ore enrichment process of the Yıldırım Holding factory located in Elazığ (Türkiye). Its chemical properties, determined by energy dispersive spectroscopy (EDS) analyses, and its density are given in Table 3. Olivine, which is initially supplied in large particle sizes, was ground to smaller sizes before being added to the soil in order to increase the chemical surface reactivity. After the size reduction process, the materials passing through the 212 μm sieve were used as additive materials.

Table 3

Chemical composition and physical properties (density) of olivine and sand used as soil additives in the experimental program

Composition Unit Olivine Sand
Mg % 35.86 2.63
Si % 24.58 30.92
O % 35.77 40.25
Fe % 3.79 11.41
K % — 0.96
Ca % — 3.08
Ti % — 0.77
C % — 0.46
Al % — 9.54
Unit weight g/cm3 3.30 2.70

To eliminate the influence of particle size differences between olivine and sand, both materials were brought to comparable size distributions. For this purpose, separate sieve analyses were performed on each material. The sand was processed to obtain a grain size similar to that of olivine by washing it through a 75 μm sieve. Chemical properties and densities are given in Table 3. The initial particle size distributions, as well as those after sieving, are presented in Figure 2. Figure 3 shows 100× magnified views of olivine and sand after sieving. Although both materials were adjusted to fall within the sand-sized fraction (75–212 µm), it should be noted that olivine was not considered or treated as a type of sand in this study. Instead, it was evaluated as an industrial waste product with potential chemical reactivity. The decision to reduce olivine to this specific grain size was made deliberately, in order to enhance its surface area and reactivity and to ensure that any observed differences in soil behavior could not be attributed solely to grain size effects. By comparing it with a quartz-based river sand of matching particle size distribution, the aim was to distinguish the contribution of olivine’s chemical and mineralogical characteristics from purely physical effects. This distinction is critical to the experimental design and the interpretation of results, as further discussed in subsequent sections.

Figure 2 Particle size distribution curves of natural soil, olivine, and sand before and after pre-treatment processes (sieving and washing).
Figure 2

Particle size distribution curves of natural soil, olivine, and sand before and after pre-treatment processes (sieving and washing).

Figure 3 Scanning electron microscopy (SEM) images of the materials after the sieving process: (a) olivine and (b) sand (magnification ×100, scale bar = 100 µm).
Figure 3

Scanning electron microscopy (SEM) images of the materials after the sieving process: (a) olivine and (b) sand (magnification ×100, scale bar = 100 µm).

2.1.3 Potassium hydroxide

Potassium hydroxide (KOH) is a strong base that is highly soluble in water. It plays an important role in the chemical industry and laboratories due to its high reactivity and solubility in water. In this study, KOH was used as an activator because of its high reactivity. Its chemical formulation is produced by electrolysis of potassium chloride and induces an exothermic reaction on contact with polar solvents or water. Its temperature and molarity are the essential factors in its effective use [55]. In the stabilization of fine-grained soils, KOH is more expensive than sodium hydroxide (NaOH); however, due to its superior effectiveness in enhancing strength, it is often the preferred choice. The application of KOH can lead to a significant long-term increase in the strength of the treated soil [56].

2.2 Method

2.2.1 Compaction test

The compaction process involves layering the soil and reducing its voids under the effect of compressive loading, which result in a decrease in volume and an increase in dry density. In this experimental study, the Harvard miniature compaction method was used for all samples. To determine the OWC and maximum dry density, both the natural soil (NS) and soil mixtures (with olivine or sand) at different weight percentages (10, 15, 20, and 25%) were mixed with varying water contents (5, 10, 15, and 20%) until a homogeneous consistency was achieved. The mixture was then placed into the mold in four equal layers. Each layer received ten blows from a 1.51 kg hammer dropped from a height of 310 mm. For the fourth layer, the last ten blows were applied using a mold extension (collar), which was then removed to allow the sample to be taken at the mold height. After compaction, the sample was weighed, and a portion of it was placed in an oven at 100–105°C for 24 h to determine the moisture content. This procedure was repeated for all samples to determine the maximum dry density and the OWC.

2.2.2 Composition and preparation of samples

The materials used in this experimental study include clay, olivine, sand, and KOH. Clay, as the NS and the primary material in this study, is represented by the abbreviation “NS.” The samples prepared by mixing clay with olivine are denoted as “S-OL,” while those mixed with sand only are labeled as “S-SA.” When these mixtures are activated with KOH, the abbreviation is suffixed with “–KOH” to indicate chemical activation.

According to the compaction test results, the natural clay and each mixture exhibited different maximum dry densities and OWCs. Based on these results, the mixtures with the highest OWC were selected for further testing to ensure a fair comparison. These corresponded to the mixtures containing 25% sand and 25% olivine by weight (i.e., 75% NS and 25% additive).

To produce consistent samples, each was prepared in its own mold, measuring 70 mm in height and 35 mm in diameter, using the OWC determined from the compaction tests. Standard Proctor energy was maintained using a single compaction layer; however, due to the reduced mold volume (67 cm3), the number of blows was adjusted from 25 to 6. Samples containing olivine and sand without KOH were cured for only 1 day, as previous studies showed that olivine alone did not show a significant increase over time [43]. In contrast, samples with KOH activation were subjected to curing periods of 28, 56, and 90 days to observe the effects of chemical reactions over time. The sample preparation process and the used equipment can be observed from Figure 4.

Figure 4 Step-by-step procedure of sample preparation, including mixture formulation, mechanical mixing, compaction into cylindrical molds, and preservation of the compacted soil samples for curing.
Figure 4

Step-by-step procedure of sample preparation, including mixture formulation, mechanical mixing, compaction into cylindrical molds, and preservation of the compacted soil samples for curing.

Based on previous studies [57,58,59], the KOH concentration used in the samples was set at 10 M. After cooling, the prepared KOH solution was added to the olivine or sand mixtures, considering their respective OWCs. For the samples without KOH, the water content was adjusted solely based on the OWC. During the curing process, all samples were stored in sealed plastic containers to prevent any loss or alteration of moisture content. Curing was carried out at ambient temperature for all durations (Table 4).

Table 4

Identity, composition, and curing conditions of soil samples prepared with olivine and sand additives, with or without KOH activation

No. Sample symbol Description of samples Soil rate (%) Olivine rate (%) Sand rate (%) KOH molarity (mol/L) Curing (day)
1 NS Natural soil 100 — — — 0
2 S-OL-1 Soil + 25% olivine 75 25 — — 1
3 S-OL-KOH-28 Soil + 25% olivine + KOH 75 25 — 10 28
4 S-OL-KOH-56 Soil + 25% olivine + KOH 75 25 — 10 56
5 S-OL-KOH-90 Soil + 25% olivine + KOH 75 25 — 10 90
6 S-SA-1 Soil + 25% sand 75 — 25 — 1
7 S-SA-KOH-28 Soil + 25% sand + KOH 75 — 25 10 28
8 S-SA-KOH-56 Soil + 25% sand + KOH 75 — 25 10 56
9 S-SA-KOH-90 Soil + 25% sand + KOH 75 — 25 10 90

2.2.3 UU triaxial test

The UU shear strength parameters of the soils were assessed through a triaxial compression test in accordance with ASTM D2850 [60]. The test system is equipped with an internal LVDT sensor that continuously measures axial deformation during loading. The tests were conducted without prior saturation or consolidation procedures, consistent with the UU test conditions. As such, no pore water pressure measurements were recorded, and B-value determination was not applicable. A visual representation of the testing setup is provided in Figure 5.

Figure 5 Fully automated triaxial test apparatus used for UU shear tests.
Figure 5

Fully automated triaxial test apparatus used for UU shear tests.

The determination of shear strength parameters of the soils involves subjecting a soil sample to the maximum stress it can withstand without failure under a given confining pressure. Initially, UU triaxial tests were performed on NS samples at confining pressures of 100, 200, 300, and 400 kPa, at a shear rate of 0.8 mm/min. Based on the compaction test results, mixtures containing 25% olivine and 25% sand by weight exhibited the highest dry densities; so shear strength focused on these mixtures. The selected samples were cured for different durations (1, 28, 56, and 90 days), and both activated (with KOH) and non-activated olivine and sand mixtures were tested under the same confining pressures. The UU testing method was chosen to simulate undrained field conditions, assuming rapid loading scenarios where drainage does not occur. The tested samples are shown in Figure 6.

Figure 6 Visual grouping of all prepared soil samples after UU triaxial tests, including untreated soil (NS), olivine-treated (S-OL), sand-treated (S-SA), and KOH-activated combinations at different curing periods.
Figure 6

Visual grouping of all prepared soil samples after UU triaxial tests, including untreated soil (NS), olivine-treated (S-OL), sand-treated (S-SA), and KOH-activated combinations at different curing periods.

2.2.4 Microscopic examinations

Microstructural analyses including scanning electron microscopy (SEM) and EDS were performed in this study. To support the findings related to maximum strength development, XRD analysis was conducted on NS samples, as well as on samples treated with olivine, sand, and their KOH-activated forms after 90 days of curing. All samples were fully dried prior to analysis. All tests were conducted in the laboratories of Sakarya University in Türkiye.

3 Results and discussion

3.1 Compaction test

A compaction curve was drawn for each sample, as shown in Figure 7, to determine the maximum dry unit weight (MDD) and OWC. As the proportions of olivine and sand increased, the MDD also increased, while the OWC decreased, resulting in an overall improvement in soil strength. For samples treated with different percentages of olivine (10, 15, 20, and 25% by weight), the MDD increased by 3.14, 6.78, 9.14, and 12.73%, respectively, compared to the NS, as summarized in Table 5. Meanwhile, the OWC decreased by 8.57, 14.29, 20.00, and 25.71%, respectively. Similarly, for samples treated with different percentages of sand (10, 15, 20, and 25 wt%), the MDD increased by 1.07, 2.97, 3.65, and 5.55%, respectively. The corresponding reductions in OWC were 2.86, 8.57, 20.00, and 25.71%, respectively. The reasons for the increase in MDD can be explained by both the high specific gravity (3.30) and particle sizes of olivine. In contrast, the increase in MDD in sand-treated samples is mainly due to particle size, as the specific gravity of sand (2.70) is similar to that of NS. In a related study examining the effects of olivine and lime on compaction, it was found that the MDD of lime-treated soils was lower than that of NS, whereas the opposite was observed for olivine-treated soils [61]. The reduction in MDD in the lime-treated samples was attributed to the low density of lime, which fills the voids without significantly increasing mass. The reductions in OWC observed with both olivine and sand are likely due to their lower water absorption capacities compared to NS. These trends are consistent with findings reported in previous studies [40,45].

Figure 7 Compaction curves showing the variation of dry unit weight with water content for soil samples treated with (a) different percentages of olivine and (b) different percentages of sand, compared to NS.
Figure 7

Compaction curves showing the variation of dry unit weight with water content for soil samples treated with (a) different percentages of olivine and (b) different percentages of sand, compared to NS.

Table 5

Optimum water content (OWC), maximum dry density (MDD), and their percentage changes for soil samples treated with varying proportions of olivine and sand

Sample Olivine rate (%) Sand rate (%) OWC (%) MDD (kN/m3) Reduction in OWC (%) Increase in MDD (%)
NS — — 17.50 17.83 — —
S-OL-10 10 — 16.00 18.39 8.57 3.14
S-OL-15 15 — 15.00 19.04 14.29 6.79
S-OL-20 20 — 14.00 19.46 20.00 9.14
S-OL-25 25 13.00 20.10 25.71 12.73
S-SA-10 — 10 17.00 18.02 2.86 1.07
S-SA-15 — 15 16.00 18.36 8.57 2.97
S-SA-20 — 20 14.00 18.48 20.00 3.65
S-SA-25 — 25 13.00 18.82 25.71 5.55

3.2 UU triaxial test

To determine the undrained shear strength parameters, UU triaxial compression tests were conducted on NS, S-OL, S-OL-KOH, S-SA, and S-SA-KOH. All tests were carried out under different curing periods (1, 28, 56, and 90 days) and confining pressures (100, 200, 300, and 400 kPa), as given in Figures 8 and 9 and Table 6.

Figure 8 Deviator stress ( σ d {\sigma }_{{\rm{d}}} ) versus axial strain ( ε z {\varepsilon }_{{\rm{z}}} ) curves obtained from UU triaxial tests for (a), (c), (e), and (g) olivine-treated samples and (b), (d), (f), and (h) sand-treated samples under different confining pressures: (a) and (b) 100 kPa, (c) and (d) 200 kPa, (e) and (f) 300 kPa, and (g) and (h) 400 kPa.
Figure 8

Deviator stress ( σ d ) versus axial strain ( ε z ) curves obtained from UU triaxial tests for (a), (c), (e), and (g) olivine-treated samples and (b), (d), (f), and (h) sand-treated samples under different confining pressures: (a) and (b) 100 kPa, (c) and (d) 200 kPa, (e) and (f) 300 kPa, and (g) and (h) 400 kPa.

Figure 9 Failure envelopes of treated and untreated soil samples at different curing periods under UU triaxial testing: olivine-treated samples (a) 1 day, (c) 28 days, (e) 56 days, and (g) 90 days; sand-treated samples (b) 1 day, (d) 28 days, (f) 56 days, and (h) 90 days.
Figure 9

Failure envelopes of treated and untreated soil samples at different curing periods under UU triaxial testing: olivine-treated samples (a) 1 day, (c) 28 days, (e) 56 days, and (g) 90 days; sand-treated samples (b) 1 day, (d) 28 days, (f) 56 days, and (h) 90 days.

Table 6

Percentage increase in max. deviator stress under different confining pressures and the corresponding shear strength parameters (cohesion c u and internal friction angle ϕ u) for treated and untreated samples

Max. deviator stress increase rate (%) Shear strength parameters
Cell pressure (kPa)
Sample Cure (day) 100 200 300 400 c u (kPa) ϕ u (°)
NS 0 — — — — 88 0
S-OL-1 1 140.83 136.87 139.13 155.49 190 3.14
S-OL-KOH-28 28 327.22 339.11 376.63 441.04 250 15.20
S-OL-KOH-56 56 346.59 389.36 427.45 511.27 255 18.52
S-OL-KOH-90 90 399.06 489.61 498.05 604.17 270 20.56
S-SA-1 1 152.66 160.34 132.61 195.38 177 7.29
S-SA-KOH-28 28 366.86 402.79 492.93 569.94 240 21.80
S-SA-KOH-56 56 513.02 589.94 633.70 734.68 330 21.55
S-SA-KOH-90 90 613.02 675.42 723.37 856.07 390 22.03

As shown in Figure 8, the samples exhibited two different types of behavior: ductile or brittle. Ductile behavior refers to gradual deformation before failure, while brittle behavior involves sudden failure with minimal deformation. NS, S-OL, and S-SA exhibited ductile behavior, while KOH-activated samples, both S-OL-KOH and S-SA-KOH, exhibited brittle behavior. Similar trends have been reported in previous studies [41,43,62]. The strain values for NS samples ranged from 17.14 to 20%. For S-OL samples, the strain reached approximately 20%. In contrast, S-OL-KOH samples cured for 28, 56, and 90 days showed significantly lower strains, ranging between 1.85 and 5.71%. S-SA samples exhibited strain values between 19.94 and 20%, while S-SA-KOH samples (at the same curing durations) ranged from 2.86 to 5.71%. These observations indicate that the addition of KOH altered the deformation characteristics of the soil, shifting its behavior from ductile to brittle. The deviator stress values of the NS samples were lower than those of the S-OL and S-SA samples. This increase can be attributed to the inclusion of olivine and sand grains, which contributed to a higher dry density. Furthermore, the deviator stress values of the KOH-activated samples (S-OL-KOH and S-SA-KOH) were higher than those of their non-activated counterparts (S-OL and S-SA). This enhancement is due to the presence of KOH, which facilitates chemical reactions that transform the olivine- or sand-treated clay matrix into a more cemented structure through the formation of chemical bonds [43]. Weakly cohesive soils are characterized by limited particle adhesion due to weak interparticle bonding and a high void ratio. In this context, two key mechanisms of improvement were observed: first, enhanced compaction efficiency resulting from the inclusion of olivine and sand grains and second the activation of chemical bonding within crystalline phases in the presence of KOH. The presence of KOH significantly increases the structural strength of the soil and its ability to grain alignment and cohesion. One of the defining characteristics of strongly cohesive soils is the strong bonding between particles. It is understood that in the absence of KOH, soil particles can move more freely under load, whereas in the presence of KOH, the activation of chemical bonds restricts particle movement, improving the overall soil stability.

As shown in Figure 9, the NS exhibited a cohesion value of 88 kPa with an internal friction angle of zero. In the presence of olivine alone (S-OL), the shear strength increased, with cohesion increasing from 88 to 190 kPa and the internal friction angle increasing to 3.14 degrees. When olivine was replaced with sand (S-SA), cohesion increased to 177 kPa, accompanied by a higher internal friction angle of 7.29 degrees. Given the similarity of results between these two cases, distinguishing their performance is challenging without considering the average maximum deviator stress. In this context, sand slightly outperformed olivine in terms of mechanical strength, possibly due to its larger grain volume, which leads to denser compaction and a lower void ratio, consistent with the values presented in Table 7. It should be noted that, in both cases, the observed improvements in shear strength are attributed solely to the granular effect of olivine and sand, without chemical activation.

Table 7

Void ratio (e), porosity (n), and degree of saturation (Sr) of NS and samples treated with 25% olivine or sand, with and without KOH activation

No. Sample symbol Description of samples e n (%) Sr (%)
1 NS Natural soil 0.52 34.30 95.13
2 S-OL-1 Soil + 25% olivine 0.45 30.90 88.91
3 S-OL-KOH-28 Soil + 25% olivine + KOH 0.44 30.62 87.58
4 S-OL-KOH-56 Soil + 25% olivine + KOH 0.42 29.73 86.92
5 S-OL-KOH-90 Soil + 25% olivine + KOH 0.42 29.77 84.84
6 S-SA-1 Soil + 25% sand 0.41 29.03 90.17
7 S-SA-KOH-28 Soil + 25% sand + KOH 0.38 27.40 93.53
8 S-SA-KOH-56 Soil + 25% sand + KOH 0.38 27.64 93.76
9 S-SA-KOH-90 Soil + 25% sand + KOH 0.39 28.15 89.93

For the KOH-activated olivine-treated samples (S-OL-KOH), cohesion values corresponding to curing periods of 28, 56, and 90 days were 250, 255, and 270 kPa, respectively. The corresponding internal friction angles were 15.20°, 18.52°, and 20.56°. In the case of KOH-activated sand-treated samples (S-SA-KOH), cohesion values for the same curing periods were 240, 330, and 390 kPa, with internal friction angles of 21.80°, 21.55°, and 22.03°, respectively. As presented in Table 6, the rate of increase in deviator stress for each sample was calculated relative to the deviator stress of the NS, allowing for a comparative evaluation of strength enhancement.

As shown in Figure 10, the strength of all samples increased with longer curing periods in the presence of KOH. Similar trends have been reported in previous studies, where the compressive strength of soils increased with extended curing periods [27,63]. These strength gains in KOH-activated samples are attributed to the activation of chemical bonds between atoms in the crystalline phases, a mechanism that will be discussed in detail in the XRD analysis section.

Figure 10 Variation of maximum deviator stress with curing time for KOH-activated soil samples under different confining pressures: (a) olivine-treated samples and (b) sand-treated samples.
Figure 10

Variation of maximum deviator stress with curing time for KOH-activated soil samples under different confining pressures: (a) olivine-treated samples and (b) sand-treated samples.

3.3 XRD analysis

XRD analysis was conducted to determine the mineralogical composition of the NS, clayey soil samples treated with olivine and sand (S-OL-1 and S-SA-1), and samples treated with olivine and sand in the presence of potassium hydroxide after 90 days of curing (S-OL-KOH-90 and S-SA-KOH-90). The corresponding chemical compositions are presented in Figures 11 and 12, as well as in Tables 8 and 9. Variations in the diffraction peaks reveal changes in the mineral composition of the samples, providing valuable insights into the crystalline phases that directly influence the structural behavior of the soil.

Figure 11 XRD spectra showing mineralogical composition of (a) NS, (b) olivine, and (c) sand based on peak intensity versus 2θ angle.
Figure 11

XRD spectra showing mineralogical composition of (a) NS, (b) olivine, and (c) sand based on peak intensity versus 2θ angle.

Figure 12 XRD patterns of selected treated soil samples: (a) S-OL-1, (b) S-SA-1, (c) S-OL-KOH-90, and (d) S-SA-KOH-90, showing mineralogical changes after treatment and curing.
Figure 12

XRD patterns of selected treated soil samples: (a) S-OL-1, (b) S-SA-1, (c) S-OL-KOH-90, and (d) S-SA-KOH-90, showing mineralogical changes after treatment and curing.

Table 8

Identified mineral phases from XRD analysis of NS, olivine, and sand samples, along with their corresponding chemical formulas

Pic NS Olivine Sand
1 Chlorite–serpentine Olivine (forsterite) Kaolinite
((Mg, Al)6(Si, Al)4O10(OH)8) (Mg2(SiO4) ) (Al2Si2O5(OH)4)
2 Quartz — Quartz
(SiO2) (SiO2)
3 Anorthite — Anatase
(CaAl2Si2O8) (TiO2)
4 Calcite — Corundum
(CaCO3) (Al2O3)
5 — — Albite
(Na(AlSi3O8))
6 — — Potassium oxide
(K2O)
7 — — Calcium carbonate
(CaCO3)
8 — — Calcium Oxide
(CaO)
Table 9

XRD-identified mineral phases in selected mixture samples (S-OL-1, S-SA-1, S-OL-KOH-90, and S-SA-KOH-90) along with their corresponding chemical compositions

Pic S-OL-1 S-SA-1 S-OL-KOH-90 S-SA-KOH-90
1 Amesite Chlorite–serpentine Illite Potassium manganese oxide
((Mg2Al)(AlSiO5(OH)4)) ((Mg, Al)6(Si, Al)4O10(OH)8) (K(Al4Si2O9(OH)3)) (K2Mn4O8)
2 Olivine (forsterite) Quartz Quartz Muscovite
(Mg2SiO4) (SiO2) (SiO2) (KAl2(Si3Al) O10(OH)2)
3 Quartz Anorthite Calcium silicide Iron hydroxide
(SiO2) (CaAl2Si2O8) (CaSi2) (Fe(OH)2)
4 Calcite Calcite Forsterite Quartz
(CaCO3) ((Mg0.03Ca0.97)(CO3)) ((Ni3,Mg7)2SiO4) (SiO2)
5 Corundum — Calcite Protoenstatite
(Al2O3) ((Mg0.03,Ca0.97)(CO3)) (MgSiO3)
6 Mathiasite (K(Ti13Cr4FeZrMg)O38) — Calcium Carbonate Aluminum oxide
(CaCO3) (Al1.92Cr08O3)
7 Protoenstatite — Titanium trioxide Sanidine
(MgSiO3) (Ti3O) (KAlSi3O8)
8 Ferdisilicite Natroalunite Calcium carbonate
(FeSi2) (Na0.58K0.42Al3(SO4)2(OH)6) (CaCO3)
9 Olivine (fayalite) — — Corundum
(Al2O3)
(Fe2(SiO4))
10 — — — Potassium titanium oxide hydrate
(K2TiO4·H2O)

The XRD analysis revealed that the dominant minerals present in the untreated NS sample are in the order of quartz, calcite, anorthite and chlorite–serpentine. In the NS sample, primary peaks are located between 20° and 40° on the 2θ axis, with the most prominent peak corresponding to quartz at exactly 26.72°. For the olivine sample, the diffraction peaks differ in position but represent the same crystalline phase. The single phase of olivine is forsterite Mg2(SiO4), which is consistent with the EDS analysis results indicating a high concentration of magnesium (Mg) compared to iron (Fe). The most intense peak for the forsterite phase occurs at 52.16°. In the sand sample, the dominant minerals identified based on intensity include quartz, calcium carbonate, anatase, kaolinite, corundum, albite, potassium oxide, and calcium oxide. The main peaks are located between 20° and 30° on the 2θ axis, with the highest intensity peak corresponding to quartz at 26.62°.

For the S-OL-1 sample, the dominant minerals identified based on peak intensity include amesite, olivine (forsterite), quartz, mathiasite, corundum, protoenstatite, ferdisilicite, and olivine (fayalite). The main diffraction peaks are located between 26.96° and 62° on the 2θ axis, with the most intense peak corresponding to quartz also at 26.96°. A similar observation was also reported in a previous study [61]. For the S-SA-1 sample, the dominant crystalline phases are chlorite–serpentine, quartz, anorthite, and calcite. The main peaks are located between 26° and 30° on the 2θ axis, with the highest peak corresponding to quartz at 26.78°.

For the S-OL-KOH-90 sample, the dominant crystalline phases identified include calcium silicide, quartz, illite, forsterite, calcite, calcium carbonate, titanium oxide, and natroalunite. The main diffraction peaks are located between 26° and 40° on the 2θ axis with the most intense peak corresponding to calcium silicide at exactly 32.44°.

For the S-SA-KOH-90 sample, the dominant crystalline phases observed include potassium manganese oxide, muscovite, iron hydroxide, quartz, protoenstatite, aluminum oxide, sanidine, calcium carbonate, corundum, and potassium titanium oxide hydrate. The main diffraction peaks are located between 20° and 30° on the 2θ axis, with the most prominent peak corresponding to quartz. In all the samples, except for the SOL-KOH-90 sample, quartz remains the dominant phase, which is consistent with the major mineral composition of the NS, contributing approximately 75% to each mixture.

In Figures 11 and 12, the numbers at the peaks indicate the minerals listed in Tables 8 and 9. Upon comparison, it can be observed that the S-SA-1 samples exhibited greater strength than the S-OL-1 samples, not due to dissolutive or cohesive chemical interactions but rather due to their higher volumetric content. In contrast, the mechanical contribution of olivine was limited by its high density, which reduced its volumetric presence in the soil matrix despite its mass.

The S-SA-KOH-90 samples showed higher strength than the S-OL-KOH-90 samples for two main reasons: first, due to their higher volumetric content, and second, due to their stronger dissolutive and cohesive chemical interactions in the presence of KOH. In the S-OL-KOH-90 sample, the crystalline phases directly associated with KOH were identified: illite [K(Al4Si2O9(OH)3)] and natroalunite [Na0.58 K0.42Al3(SO4)2(OH)6].

On the other hand, in the S-SA-KOH-90 sample, four crystalline phases directly bonded with KOH were identified: potassium manganese oxide [K2Mn4O8], muscovite [KAl2(Si3Al)O10(OH)2], sanidine [KAlSi3O8], potassium titanium oxide hydrate [K2TiO4H2O]. These are solid crystals formed through the dissolution of silicate (SiO4) and aluminate (AlO2) phases, which directly contribute to the improvement of shear strength parameters [58,64]. These mineralogical changes confirm that, despite being considered chemically inert, sand particles can contribute to strength development through the formation of reactive crystalline phases when combined with KOH.

4 Conclusions

In this study, a series of experimental analyses were carried out to investigate the behavior of clayey soil treated with either olivine or sand, both in the presence and absence of KOH. The findings led to several important conclusions:

  • As the proportion of olivine and sand increased, the maximum dry unit weight increased, while the OWC decreased. This trend is attributed to the compaction efficiency and particle characteristics of the additives.

  • Void ratio values confirmed that sand led to a more compact soil structure than olivine. While the NS had an average void ratio of approximately 0.52, this value was reduced to 0.43 with olivine and to 0.39 with sand. This difference is mainly due to the higher volumetric content of sand compared to olivine, which has a higher specific gravity but occupies less volume.

  • Sand contributed to the increase in dry density solely through its grain structure, whereas olivine contributed through both its grain size and higher specific gravity. However, despite olivine’s higher density, sand-treated samples exhibited greater shear strength, highlighting that an increase in dry density does not directly translate to an increase in shear strength.

  • Stress–strain behavior revealed that untreated NS, olivine-treated soil (S-OL), and sand-treated soil (S-SA) all exhibited ductile behavior. In contrast, samples activated with KOH (S-OL-KOH and S-SA-KOH) exhibited brittle behavior, likely due to the formation of rigid cementitious bonds restricting particle movement. While ductile behavior provides greater deformation capacity and energy absorption under load, brittle behavior may lead to sudden failure without significant warning, which is critical for evaluating the safety and serviceability of geotechnical structures.

  • Among all tested combinations, S-SA-KOH-90 and S-OL-KOH-90 demonstrated the highest shear strength values. At a confining pressure of 100 kPa, compared to NS, the strength increased by 399% for olivine and 613% for sand. Although sand exhibited higher shear strength values under certain conditions, the contribution of olivine, particularly when used with KOH, was substantial and cannot be overlooked. Given its chemical reactivity and environmental benefits as an industrial byproduct, olivine presents itself as a promising alternative that merits further research, especially in terms of long-term performance, cost-effectiveness, and scalability in field applications.

  • XRD analysis confirmed the formation of several crystalline phases in the presence of KOH that may be responsible for the enhanced strength, including natroalunite, potassium manganese oxide, muscovite, sanidine, and potassium titanium oxide hydrate. These phases are believed to result from chemical reactions between KOH and silicate/aluminate components in the soil matrix. While no adverse effects such as alkali–silica reactions or excessive pH increases were observed during laboratory-scale testing, further investigation is recommended to assess the long-term geochemical stability of KOH-activated systems, especially under field conditions and extended curing durations.

  • Overall, olivine waste from the chromite ore enrichment process has shown promise as an environmentally sustainable alternative for clayey soil stabilization. It enhances shear strength while also offering the benefit of reducing carbon emissions. However, the results also demonstrate that sand, with similar granulometry and inert chemical properties, can yield comparable improvements when volumetrically optimized. This indicates that the performance gains attributed to olivine in some studies may not be entirely unique and that other economical and accessible materials, such as sand, can offer viable alternatives for certain stabilization applications.

In this context, the present study encourages future researchers to consider not only the chemical composition but also the volumetric characteristics, reactivity potential, and economic feasibility of alternative materials in soil stabilization studies.

tel: +902642955707

  1. Funding information: Authors state no funding involved.

  2. Author contributions: Abdelmaoula Mahamoud Tahir: conceptualization, investigation, methodology, data curation, formal analysis, writing – original draft. Sedat Sert: project administration, supervision, writing – review and editing. Eylem Arslan: writing – review, visualization, supporting data interpretation. Ertan Bol and Aşkın Özocak: supervision, writing – review and editing. İbrahim Atlı: material supply. All authors have read and agreed to the published version of the manuscript.

  3. Conflict of interest: The authors have no relevant financial or non-financial interests to disclose.

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Received: 2025-05-20
Revised: 2025-07-13
Accepted: 2025-08-01
Published Online: 2025-08-29

© 2025 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

Articles in the same Issue

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  2. Seismic response and damage model analysis of rocky slopes with weak interlayers
  3. Multi-scenario simulation and eco-environmental effect analysis of “Production–Living–Ecological space” based on PLUS model: A case study of Anyang City
  4. Remote sensing estimation of chlorophyll content in rape leaves in Weibei dryland region of China
  5. GIS-based frequency ratio and Shannon entropy modeling for landslide susceptibility mapping: A case study in Kundah Taluk, Nilgiris District, India
  6. Natural gas origin and accumulation of the Changxing–Feixianguan Formation in the Puguang area, China
  7. Spatial variations of shear-wave velocity anomaly derived from Love wave ambient noise seismic tomography along Lembang Fault (West Java, Indonesia)
  8. Evaluation of cumulative rainfall and rainfall event–duration threshold based on triggering and non-triggering rainfalls: Northern Thailand case
  9. Pixel and region-oriented classification of Sentinel-2 imagery to assess LULC dynamics and their climate impact in Nowshera, Pakistan
  10. The use of radar-optical remote sensing data and geographic information system–analytical hierarchy process–multicriteria decision analysis techniques for revealing groundwater recharge prospective zones in arid-semi arid lands
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  13. Spatial-temporal evolution of habitat quality in tropical monsoon climate region based on “pattern–process–quality” – a case study of Cambodia
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https://doi.org/10.1515/geo-2025-0868
Keywords for this article
soil stabilization; clay; olivine waste; sand; sustainability
Creative Commons
BY 4.0

Articles in the same Issue

  1. Research Articles
  2. Seismic response and damage model analysis of rocky slopes with weak interlayers
  3. Multi-scenario simulation and eco-environmental effect analysis of “Production–Living–Ecological space” based on PLUS model: A case study of Anyang City
  4. Remote sensing estimation of chlorophyll content in rape leaves in Weibei dryland region of China
  5. GIS-based frequency ratio and Shannon entropy modeling for landslide susceptibility mapping: A case study in Kundah Taluk, Nilgiris District, India
  6. Natural gas origin and accumulation of the Changxing–Feixianguan Formation in the Puguang area, China
  7. Spatial variations of shear-wave velocity anomaly derived from Love wave ambient noise seismic tomography along Lembang Fault (West Java, Indonesia)
  8. Evaluation of cumulative rainfall and rainfall event–duration threshold based on triggering and non-triggering rainfalls: Northern Thailand case
  9. Pixel and region-oriented classification of Sentinel-2 imagery to assess LULC dynamics and their climate impact in Nowshera, Pakistan
  10. The use of radar-optical remote sensing data and geographic information system–analytical hierarchy process–multicriteria decision analysis techniques for revealing groundwater recharge prospective zones in arid-semi arid lands
  11. Effect of pore throats on the reservoir quality of tight sandstone: A case study of the Yanchang Formation in the Zhidan area, Ordos Basin
  12. Hydroelectric simulation of the phreatic water response of mining cracked soil based on microbial solidification
  13. Spatial-temporal evolution of habitat quality in tropical monsoon climate region based on “pattern–process–quality” – a case study of Cambodia
  14. Early Permian to Middle Triassic Formation petroleum potentials of Sydney Basin, Australia: A geochemical analysis
  15. Micro-mechanism analysis of Zhongchuan loess liquefaction disaster induced by Jishishan M6.2 earthquake in 2023
  16. Prediction method of S-wave velocities in tight sandstone reservoirs – a case study of CO2 geological storage area in Ordos Basin
  17. Ecological restoration in valley area of semiarid region damaged by shallow buried coal seam mining
  18. Hydrocarbon-generating characteristics of Xujiahe coal-bearing source rocks in the continuous sedimentary environment of the Southwest Sichuan
  19. Hazard analysis of future surface displacements on active faults based on the recurrence interval of strong earthquakes
  20. Structural characterization of the Zalm district, West Saudi Arabia, using aeromagnetic data: An approach for gold mineral exploration
  21. Research on the variation in the Shields curve of silt initiation
  22. Reuse of agricultural drainage water and wastewater for crop irrigation in southeastern Algeria
  23. Assessing the effectiveness of utilizing low-cost inertial measurement unit sensors for producing as-built plans
  24. Analysis of the formation process of a natural fertilizer in the loess area
  25. Machine learning methods for landslide mapping studies: A comparative study of SVM and RF algorithms in the Oued Aoulai watershed (Morocco)
  26. Chemical dissolution and the source of salt efflorescence in weathering of sandstone cultural relics
  27. Molecular simulation of methane adsorption capacity in transitional shale – a case study of Longtan Formation shale in Southern Sichuan Basin, SW China
  28. Evolution characteristics of extreme maximum temperature events in Central China and adaptation strategies under different future warming scenarios
  29. Estimating Bowen ratio in local environment based on satellite imagery
  30. 3D fusion modeling of multi-scale geological structures based on subdivision-NURBS surfaces and stratigraphic sequence formalization
  31. Comparative analysis of machine learning algorithms in Google Earth Engine for urban land use dynamics in rapidly urbanizing South Asian cities
  32. Study on the mechanism of plant root influence on soil properties in expansive soil areas
  33. Simulation of seismic hazard parameters and earthquakes source mechanisms along the Red Sea rift, western Saudi Arabia
  34. Tectonics vs sedimentation in foredeep basins: A tale from the Oligo-Miocene Monte Falterona Formation (Northern Apennines, Italy)
  35. Investigation of landslide areas in Tokat-Almus road between Bakımlı-Almus by the PS-InSAR method (Türkiye)
  36. Predicting coastal variations in non-storm conditions with machine learning
  37. Cross-dimensional adaptivity research on a 3D earth observation data cube model
  38. Geochronology and geochemistry of late Paleozoic volcanic rocks in eastern Inner Mongolia and their geological significance
  39. Spatial and temporal evolution of land use and habitat quality in arid regions – a case of Northwest China
  40. Ground-penetrating radar imaging of subsurface karst features controlling water leakage across Wadi Namar dam, south Riyadh, Saudi Arabia
  41. Rayleigh wave dispersion inversion via modified sine cosine algorithm: Application to Hangzhou, China passive surface wave data
  42. Fractal insights into permeability control by pore structure in tight sandstone reservoirs, Heshui area, Ordos Basin
  43. Debris flow hazard characteristic and mitigation in Yusitong Gully, Hengduan Mountainous Region
  44. Research on community characteristics of vegetation restoration in hilly power engineering based on multi temporal remote sensing technology
  45. Identification of radial drainage networks based on topographic and geometric features
  46. Trace elements and melt inclusion in zircon within the Qunji porphyry Cu deposit: Application to the metallogenic potential of the reduced magma-hydrothermal system
  47. Pore, fracture characteristics and diagenetic evolution of medium-maturity marine shales from the Silurian Longmaxi Formation, NE Sichuan Basin, China
  48. Study of the earthquakes source parameters, site response, and path attenuation using P and S-waves spectral inversion, Aswan region, south Egypt
  49. Source of contamination and assessment of potential health risks of potentially toxic metal(loid)s in agricultural soil from Al Lith, Saudi Arabia
  50. Regional spatiotemporal evolution and influencing factors of rural construction areas in the Nanxi River Basin via GIS
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  52. Effect of microscopic pore–throat structure heterogeneity on waterflooding seepage characteristics of tight sandstone reservoirs
  53. Environmental health risk assessment of Zn, Cd, Pb, Fe, and Co in coastal sediments of the southeastern Gulf of Aqaba
  54. A modified Hoek–Brown model considering softening effects and its applications
  55. Evaluation of engineering properties of soil for sustainable urban development
  56. The spatio-temporal characteristics and influencing factors of sustainable development in China’s provincial areas
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  58. Gold vein mineralogy and oxygen isotopes of Wadi Abu Khusheiba, Jordan
  59. Prediction of surface deformation time series in closed mines based on LSTM and optimization algorithms
  60. 2D–3D Geological features collaborative identification of surrounding rock structural planes in hydraulic adit based on OC-AINet
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  69. Seismic prediction of Permian volcanic rock reservoirs in Southwest Sichuan Basin
  70. Application of CBERS-04 IRS data to land surface temperature inversion: A case study based on Minqin arid area
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  74. Hazard classification of active faults in Yunnan base on probabilistic seismic hazard assessment
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  81. Oil accumulation process of the Kongdian reservoir in the deep subsag zone of the Cangdong Sag, Bohai Bay Basin, China
  82. Investigation of velocity profile in rock–ice avalanche by particle image velocimetry measurement
  83. Optimizing 3D seismic survey geometries using ray tracing and illumination modeling: A case study from Penobscot field
  84. Sedimentology of the Phra That and Pha Daeng Formations: A preliminary evaluation of geological CO2 storage potential in the Lampang Basin, Thailand
  85. Improved classification algorithm for hyperspectral remote sensing images based on the hybrid spectral network model
  86. Map analysis of soil erodibility rates and gully erosion sites in Anambra State, South Eastern Nigeria
  87. Identification and driving mechanism of land use conflict in China’s South-North transition zone: A case study of Huaihe River Basin
  88. Evaluation of the impact of land-use change on earthquake risk distribution in different periods: An empirical analysis from Sichuan Province
  89. A test site case study on the long-term behavior of geotextile tubes
  90. An experimental investigation into carbon dioxide flooding and rock dissolution in low-permeability reservoirs of the South China Sea
  91. Detection and semi-quantitative analysis of naphthenic acids in coal and gangue from mining areas in China
  92. Comparative effects of olivine and sand on KOH-treated clayey soil
  93. YOLO-MC: An algorithm for early forest fire recognition based on drone image
  94. Earthquake building damage classification based on full suite of Sentinel-1 features
  95. Potential landslide detection and influencing factors analysis in the upper Yellow River based on SBAS-InSAR technology
  96. Assessing green area changes in Najran City, Saudi Arabia (2013–2022) using hybrid deep learning techniques
  97. An advanced approach integrating methods to estimate hydraulic conductivity of different soil types supported by a machine learning model
  98. Hybrid methods for land use and land cover classification using remote sensing and combined spectral feature extraction: A case study of Najran City, KSA
  99. Streamlining digital elevation model construction from historical aerial photographs: The impact of reference elevation data on spatial accuracy
  100. Analysis of urban expansion patterns in the Yangtze River Delta based on the fusion impervious surfaces dataset
  101. A metaverse-based visual analysis approach for 3D reservoir models
  102. Late Quaternary record of 100 ka depositional cycles on the Larache shelf (NW Morocco)
  103. Integrated well-seismic analysis of sedimentary facies distribution: A case study from the Mesoproterozoic, Ordos Basin, China
  104. Study on the spatial equilibrium of cultural and tourism resources in Macao, China
  105. Urban road surface condition detecting and integrating based on the mobile sensing framework with multi-modal sensors
  106. Application of improved sine cosine algorithm with chaotic mapping and novel updating methods for joint inversion of resistivity and surface wave data
  107. The synergistic use of AHP and GIS to assess factors driving forest fire potential in a peat swamp forest in Thailand
  108. Dynamic response analysis and comprehensive evaluation of cement-improved aeolian sand roadbed
  109. Rock control on evolution of Khorat Cuesta, Khorat UNESCO Geopark, Northeastern Thailand
  110. Gradient response mechanism of carbon storage: Spatiotemporal analysis of economic-ecological dimensions based on hybrid machine learning
  111. Comparison of several seismic active earth pressure calculation methods for retaining structures
  112. Review Articles
  113. Humic substances influence on the distribution of dissolved iron in seawater: A review of electrochemical methods and other techniques
  114. Applications of physics-informed neural networks in geosciences: From basic seismology to comprehensive environmental studies
  115. Ore-controlling structures of granite-related uranium deposits in South China: A review
  116. Shallow geological structure features in Balikpapan Bay East Kalimantan Province – Indonesia
  117. A review on the tectonic affinity of microcontinents and evolution of the Proto-Tethys Ocean in Northeastern Tibet
  118. Special Issue: Natural Resources and Environmental Risks: Towards a Sustainable Future - Part II
  119. Depopulation in the Visok micro-region: Toward demographic and economic revitalization
  120. Special Issue: Geospatial and Environmental Dynamics - Part II
  121. Advancing urban sustainability: Applying GIS technologies to assess SDG indicators – a case study of Podgorica (Montenegro)
  122. Spatiotemporal and trend analysis of common cancers in men in Central Serbia (1999–2021)
  123. Minerals for the green agenda, implications, stalemates, and alternatives
  124. Spatiotemporal water quality analysis of Vrana Lake, Croatia
  125. Functional transformation of settlements in coal exploitation zones: A case study of the municipality of Stanari in Republic of Srpska (Bosnia and Herzegovina)
  126. Hypertension in AP Vojvodina (Northern Serbia): A spatio-temporal analysis of patients at the Institute for Cardiovascular Diseases of Vojvodina
  127. Regional patterns in cause-specific mortality in Montenegro, 1991–2019
  128. Spatio-temporal analysis of flood events using GIS and remote sensing-based approach in the Ukrina River Basin, Bosnia and Herzegovina
  129. Flash flood susceptibility mapping using LiDAR-Derived DEM and machine learning algorithms: Ljuboviđa case study, Serbia
  130. Geocultural heritage as a basis for geotourism development: Banjska Monastery, Zvečan (Serbia)
  131. Assessment of groundwater potential zones using GIS and AHP techniques – A case study of the zone of influence of Kolubara Mining Basin
  132. Impact of the agri-geographical transformation of rural settlements on the geospatial dynamics of soil erosion intensity in municipalities of Central Serbia
  133. Where faith meets geomorphology: The cultural and religious significance of geodiversity explored through geospatial technologies
  134. Applications of local climate zone classification in European cities: A review of in situ and mobile monitoring methods in urban climate studies
  135. Complex multivariate water quality impact assessment on Krivaja River
  136. Ionization hotspots near waterfalls in Eastern Serbia’s Stara Planina Mountain
  137. Shift in landscape use strategies during the transition from the Bronze age to Iron age in Northwest Serbia
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