Marl Soils Research Articles

Resistance and swelling of Tabriz marl soils stabilised using nano-silica and nano-alumina

The effects of nano-silica (NS) and nano-alumina (NA) additions on problematic marl soil in Tabriz, Iran were investigated. Marl soils constitute the foundations for most projects in Tabriz. Due to water absorption, these soils are liable to volume change, leading to instability risks in the foundations. Various physical and chemical methods have been employed to stabilise these soils. In the present study, for the first time, reconstructed samples of Tabriz marl were stabilised with various percentages of NS and NA, which have fewer negative environmental effects compared with ordinary additives such as Portland cement or lime. Soil swelling behaviours were evaluated experimentally using tests for Atterberg limits, density, free swelling, swelling pressure, California bearing ratio (CBR) and direct shear. Field emission scanning electron microscopy and X-ray powder diffraction analyses were conducted at curing times of 1, 7 and 28 days. It was found that NA had a greater effect on reducing the swelling of stabilised samples than NS. However, NS had a greater effect on increasing the strength (CBR).

Seed burial depth, seedling emergence, and height as affected by animal trampling in marl soils

Seed burial depth, seedling emergence, and height as affected by animal trampling in marl soils

Microstructural Evaluation of the Effect of Initial pH on Geotechnical and Geoenvironmental Characteristics of Marl Soils

Microstructural Evaluation of the Effect of Initial pH on Geotechnical and Geoenvironmental Characteristics of Marl Soils

Effects of lead contaminants on engineering properties of Iranian marl soil from the microstructural perspective

Most of the industries in the south of Iran and north of the Persian Gulf are built on marl bedrocks and these industries are major sources of heavy metal pollutants. Therefore, the engineering properties of marl soils contaminated with heavy metals (particularly lead ions) are worthy of thorough investigation. This was accomplished by artificial contamination of marl soil with varying lead concentrations and measurment of some geotechnical (granularity, Atterberg limits, compressive strength, and permeability) and geo-environmental (CEC, pH, and contaminant retention) characteristics. In addition, with the aid of X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images the changes in mineralogy and microstructural behavior of lead-contaminated soil were investigated. According to the findings of the present study, marl soil can hold about 200 cmol/kg-soil of lead concentration. As seen by SEM images, the lead precipitation changed the soil's geotechnical properties by altering the structure and texture of soil (notably flocculation). At 100 cmol/kg-soil lead concentration, the compressive strength was reduced by about 85%, while the hydraulic conductivity increased up to 170 times. Adding lead to the marl soil decreased the intensity of X-ray diffraction peaks for the main clay minerals and created new peaks associated with precipitated cerussite, shannonite, and leadhillite.

Impacts of MgO waste:GGBS formulations on the performance of a stabilised natural high sulphate bearing soil

Industrial and urban wastes have been generated over time due to urban development with severe environmental and health implications. This paper reports the valorisation of waste and industrial by-product (magnesium oxide waste – MG1 and Ground Granulated Blast furnace Slag – GGBS) to develop an alternative cementitious binder for suppressing swelling in high sulphate bearing soils due to the formation of a highly expansive crystalline hydrate (ettringite) upon treatment with Portland Cement – PC or lime. Cylinder test specimens were developed using three MG1:GGBS proportions by weight (10:90, 20:80 and 30:70) to stabilise a natural Gypsum marl soil (GM) containing high levels of sulphate at varying stabiliser dosages (6, 8 and 10 wt%), with PC as the control binder. UCS, Linear Expansion and SEM investigations were employed to assess the engineering suitability of the MG1:GGBS stabilised GM cylinder test specimen. Results suggest the viability of producing an alternative cementitious binder using up to 30 wt% MgO-waste to successfully activate GGBS at stabiliser dosages of 6–10 wt%. From a mechanical perspective, the MG1:GGBS stabilised GM soil was 1.5–3 times more than the control at 28 days moist curing age, while the resistance to linear expansion produced near-zero swellings (0.13%–0.2%) after 56 days, in comparison with the control of 3.2%. SEM micrographs showed a more compact structure with lesser voids and no morphology of ettringite. This new technology is expected to mitigate the environmental concerns of using PC and promote sustainable techniques of reusing industrial by-product materials for stabilising sulphate soils.

Changes in morphologic, hydraulic, and hydrodynamic properties of rill erosion due to surface inoculation of endemic soil cyanobacteria

Rill erosion is one of the most important causes of land degradation, and it is caused by the flow concentration on the surface of the hillslopes. It, therefore, results in several times increase in the amount of soil loss and sediment yield. However, the biological control of the rill erosion using soil microorganisms has not been adequately endeavored. In this respect, soil microorganisms have been used and accepted as one of the latest methods for managing surface erosion. Following that, we evaluated the efficacy of soil cyanobacteria inoculation in controlling rill erosion components in the current study. To this end, inoculation of cyanobacteria in mid-sized plots with dimensions of 6 × 1 × 0.5 m, at a slope of 30%, was performed on marl soil and prone to rill erosion from Marzanabad Region, northern Iran. An artificial rainfall of 50 ± 7 mm h−1 was simulated after 40 days of cyanobacteria inoculation, along with a supplementary runoff of 2 ± 0.32 L min−1. Many different outflows and soil loss and runoff hydraulic and hydrodynamic properties were then measured to assess the effects of soil cyanobacteria inoculation compared to untreated conditions. The results showed that inoculation of cyanobacteria reduced runoff volume, runoff coefficient, soil loss, and sediment concentration by 42, 64, 82, and 62%, respectively. It also increased infiltration volume by 74% showing high water retention capacity of the treated soil. Also, the hydraulic and hydrodynamic components of the flow, including velocity, depth, Froude number, and Reynolds number, were significantly reduced (P < 0.05), in contrast, the shear stress and friction coefficient did not change significantly in treated plots. The statistical analyses further showed that soil surface cyanobacterisation considerably affected morphological factors of rill depth, rill mean width, rill maximum length, and rill density by 44.34, 54.25, 40.75, and 38.21%, respectively. Overall, the findings revealed that using cyanobacteria to mitigate rill erosion is a practical and effective method for the bio-conservation of soil and water resources in most arid and semiarid areas.

Application of the dynamic cone penetrometer test for determining the geotechnical characteristics of marl soils treated by lime

Quantitative estimation of mechanical characteristics of soils and determination of their behavior using in-situ experiments have always been one of the main concerns of geotechnical engineers. So far, various methods have been introduced to achieve this goal, among which the Dynamic Cone Penetrometer (DCP) test has become more popular as one of the most accurate and efficient methods. Therefore, in this study, an attempt was made to examine the correlation between different soil parameters by performing DCP test along with a series of conventional tests including Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) tests on marl soil samples containing 2, 5, 8% lime at 1, 7 and 15 curing days. Furthermore, since the subgrade reaction coefficient (Ks) is needed in the design of pavements and their underlying materials, Plate Load Test (PLT) was performed to determine Ks. The results showed that the addition of lime up to 5% increased UCS, CBR and Ks and decreased dynamic penetrometer index (DPI) of marl soil samples. Further addition of lime had a negative effect on the mechanical characteristics of the samples. Moreover, using the equations obtained from the correlations in this study, strength characteristics and subgrade reaction coefficient of the stabilized marl soil can be estimated by knowing the DPI of the samples. The results of this study showed that the use of the DCP test as a cheap and easy-to-use method can provide a comprehensive view of soil behavior in civil engineering projects with an acceptable coefficient of determination to geotechnical engineers.

Interactive effects of hydrology and fire drive differential biogeochemical legacies in subtropical wetlands

AbstractFire is an important component of many ecosystems, as it impacts biodiversity, biogeochemical cycles, and primary production. In wetlands, fire interacts with hydrologic regimes and other ecosystem characteristics to determine soil carbon (C) gains or losses and rates of nutrient cycling. However, how legacies of fire interact with wetland hydroperiod to affect soil chemistry is uncertain. We used the Florida Everglades as a model landscape to study how fire regimes, hydroperiod, and soil types collectively contribute to long‐term C, nitrogen (N), and phosphorus (P) concentrations and stoichiometric mass ratios (C:N, C:P, N:P) in both short‐ and long‐hydroperiod subtropical wetlands that consist of marl and peat soils, respectively. We used fire records from 1948 to 2018 and hydroperiod from 1991 to 2003, and analyzed these data together with soil chemistry data collected during two extensive field surveys (n = 539) across different ecosystem and soil types throughout Everglades National Park. We also analyzed macrophyte and periphyton P concentrations (n = 150) collected from 2003 to 2016 in fire‐impacted wetland sites. Hydroperiod was the main driver of soil C concentration in both marl and peat soils, but fire played a substantial role in nutrient cycling. Particularly in marl soils, soil P concentrations were affected by the absence of fire. In the first decade post‐fire, we observed an amplification of P cycling with decreased soil C:P ratios by 95% and N:P ratios by 45%. After more than a decade post‐fire, soil P became increasingly depleted (41% lower). Macrophyte P tissue concentration was 50% higher only in the first year post‐fire, whereas periphyton P did not change. By recycling nutrients and through removal of litter accumulation, which forms a physical obstacle to photosynthesis, fire likely helps maintain high levels of macrophyte aboveground live biomass as well. Given its substantial effect on nutrient cycling, we advocate for fire management that uses fire return intervals that minimize depletion of soil nutrients and promote positive feedbacks to productivity in wetland ecosystems. In addition, coordinated management of fire return intervals and wetland hydroperiod can be used to set priorities for wetland soil nutrient concentrations and ratios.

Performance Evaluation of the Screw Nailed Walls in Tabriz Marl

Urban development and rapid extension of cities have been accompanied by considerable growth in excavation projects. Soil nail walls have been found to be an economical solution to many soil reinforcement and excavation support problems. To overcome some of the intrinsic problems with the conventional grout soil nails, screw soil nails were developed in recent years that provide several advantages over grouted soil nails. Tabriz marl outcrops at considerable parts of this city. Considering the rapid development of the Tabriz (as one of the biggest industrial cities of Iran), a large part of new urban areas and industrial zones will be located on marl soils. Therefore, it is necessary to evaluate the efficiency of the screw nailing method in Tabriz marl soils. In the present study, the performance of the walls reinforced by screw and grouted nails in different types of Tabriz marls was studied. For this purpose, a three-dimensional (3D) modeling is performed using the ABAQUS software. The results of the numerical analyses revealed that the failure zone of the screw and grout nailed walls is similar and consisting of parts entitled A and B. There is no significant difference between the characteristics of part B at both of the screw nailing and grout nailing methods. While, the A part of the failure zone and the maximum soil displacements in this part at the screw nailing method are smaller than those of the grout nailing method. At all types of the Tabriz marl, the lateral and vertical displacements of the reinforced walls by screw nails are smaller than those of grout nails, and in the case of yellow marl, the difference is considerable, while, at brown marl, it is negligible. The results of analyses show that the screw nail performs better than the pressurized cement grouted nail in terms of wall displacement. The efficiency of the screw nails increases in comparison to grouted nails by proceeding with the excavation process. At yellow marl because of lower elastic modulus value, the performance of the screw and grouted nails is more obvious than the other types of marl. The rate of increase in settlement values and maximum settlement of the soil for screw nailed walls are smaller than those of grout nailed walls. Also, the settlement profile of ground surface behind the wall is consisting of two parts, including critical and non-critical parts. The difference in the behavior of the screw and grouted nailed walls is obvious in the critical part of the soil behind the wall.

Application of the Dynamic Cone Penetrometer (DCP) Test for Determination of the Geotechnical Characteristics of Marl Soils Treated by Lime

Quantitative estimation of mechanical characteristics of soils and determination of their behavior using in-situ experiments have always been one of the main concerns of geotechnical engineers. So far, various methods have been introduced to achieve this goal, among which the Dynamic Cone Penetrometer (DCP) test has become more popular as one of the most accurate and efficient methods. Therefore, in this study, an attempt was made to examine the correlation between different soil parameters by performing DCP test along with a series of conventional tests including Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) tests on marl soil samples containing 2, 5, 8% lime at 1, 7 and 15 curing times. Furthermore, since the modulus of subgrade reaction (Ks) is needed in the design of pavements and their underlying materials, Plate Load Test (PLT) was performed to determine Ks. The results showed that the addition of lime up to 5% increased UCS, CBR and Ks and decreased dynamic penetrometer index (DPI) of marl soil samples. Further addition of lime had a negative effect on the mechanical characteristics of the samples. Moreover, using the equations obtained from the correlations in this study, strength characteristics and modulus of subgrade reaction of the stabilized marl soil can be estimated by knowing the DPI of the samples. The results of this study showed that the use of the DCP test as a cheap and easy-to-use method can provide a comprehensive view of soil behavior in civil engineering projects with an acceptable coefficient of determination to geotechnical engineers.

The hydrologic behavior of Loess and Marl soils in response to biochar and polyacrylamide mulching under laboratorial rainfall simulation conditions

Due to the high costs associated with the control of soil erosion, the precise selection of practical techniques towards this end is a prerequisite for sustainable land management. For the proper application of anti-erosion measures, a good knowledge of the behavior of soil erosion and hydrological properties is required. Research has indicated that biochar (BC) and polyacrylamide (PAM) are important soil amendments to enhance the physical and hydrological characteristics of soil. However, little is known about the response and mechanisms underlying the wearing away of Marl and Loess erosion-prone soils treated with individually and with a combination of BC and PAM. Therefore, we tested the effectiveness of these anti-erosion techniques on the variability of 1) hydrological components (i.e., time to runoff, the runoff coefficient, and infiltration), 2) runoff quality components (i.e., pH and electrical conductivity (EC)), and 3) erosion components (i.e., upward-splash, downward-splash, net-splash erosion, soil loss, and sediment concentration) at two locations with the Marl and Loess soils under rainfall simulation conditions. The study treatments consisted of control (200 ml water), BC (800 g m−2), PAM (2 g m−2), and BC (800 g m−2) + PAM (2 g m−2). The treatments were sprayed uniformly over the small plots (0.3 × 0.5 × 0.5 m in dimension; 0.25 m2 in area) with a slope of 20% using three replicates. Rainfall with an intensity of 50 mm h−1 for 0.5 h was applied. The results showed that (a) the use of PAM alone delayed the time to runoff with a rate of 41.4% compared to the control treatment in the Marl soil, and all treatments delayed the time to runoff for the Loess soil (BC = 37.1% and PAM = BC + PAM = 12.9%); (b) among the study treatments, PAM had the greatest effect as it decreased the runoff coefficient by 2.47% and 13.67%, and improved infiltration by 0.02% and 0.13% in Marl and Loess soils, respectively; (c) BC and BC + PAM increased the pH values of the runoff whereas the application of PAM partially reduced the pH compared to the control plot in both the soils studied; (d) the application of BC and BC + PAM significantly (p < 0.05) increased the EC of runoff released from both tested soils. In contrast, PAM had the least influence on the EC of the runoff compared to the control condition; (e) the maximum effect on the reduction of soil loss was attributed to BC for Marl and Loess soils with rates of −14.07% and −83.21%, respectively. Additionally, the maximum benefit of the reduction in sediment concentration was attributed to PAM (-14.87%) and BC (−78.35%), respectively, in Marl and Loess soils; (f) all treatments reduced the upward-splash, downward-splash, and the net-splash erosion for both soils studied in the range of −13.69% (BC + PAM in Loess soil) to −73.68% (BC in Marl soil) in comparison with the control treatment.

Runoff and soil loss from small plots of erosion-prone marl soil inoculated with bacteria and cyanobacteria under real conditions

Land degradation is a major global concern that is exacerbated in the erosion-prone marl and calcium carbonate-rich mudstone slopes. Several studies have therefore focused on finding ways to inhibit soil erosion among which, soil inoculation has been recently introduced as a new technique. However, the success of such treatment has not been adequately taken into account. Following this, in this study, we assessed the hydrological responses of an erosion-prone marl soil due to surface inoculation of bacteria and cyanobacteria. The individual bacteria and cyanobacteria and their combination were inoculated (in three repetitions) on 0.5 m × 0.5 m-sized plots filled by marl soil from the Marzanabad Region in the north of Iran. The entire plots were thoroughly exposed to natural conditions in an open area at the campus of Faculty of Natural Resources of Tarbiat Modares University in Noor, Mazandaran Province, Iran. After 32 days of inoculation, five erosive natural rainfalls occurred on the experimental plots, from 10 to Jan. 29, 2018. The rainfalls on control plot led to a relatively high runoff yield (i.e., 223–2010 ml) and coefficient (i.e., 2.3–7.6%), a considerable soil loss (i.e., 1.32–17.96 g), and sediment concentration (i.e., 2.4–9 g l−1). Whilst, in the inoculated (i.e., bacteria, cyanobacteria, and bacteria + cyanobacteria) plots, the runoff volume, runoff coefficient, soil loss, and sediment concentration varied between 56 and 1116 ml, 2.3–9.4%, 0.16–4.04 g, and 1.01–3.61 g l−1, respectively. It, therefore, verified that the soil inoculation decreased the runoff yield and coefficient (29–77%), soil loss (77–89%), and sediment concentration (60–76%), as compared to the control. On the whole, we found that the soil inoculation technique could be considered as a bio-strategy to conserve/restore marl soil lands, where the viability of conventional methods is low.

Utilization of Portland cement with limestone powder and cement kiln dust for stabilization/solidification of oil-contaminated marl soil.

Stabilization/solidification (S/S) is a technique that has been widely used to treat contaminated soils using several types of stabilizers, such as ordinary Portland cement (OPC). In this research, marl soil that was collected from eastern Saudi Arabia was contaminated by either diesel or crude oil at different dosages (i.e., 2.5, 5, and 10% by the dry weight of the soil) and tested to assess its geotechnical and environmental properties. Thereafter, the contaminated soil was stabilized using OPC, limestone powder (LSP), and cement kiln dust (CKD) at different proportions. The contaminated-stabilized soils were evaluated by measuring the changes in their geotechnical properties, and both metal and hydrocarbon contents. Results of this investigation indicated that the S/S treatment of the contaminated soils enhanced the compaction characteristics with a significant improvement in the unconfined compressive strength (UCS) results, and all of S/S-treated mixtures were found to pass the strength criterion of the U.S. Environmental Protection Agency (USEPA) (i.e., 340kPa after 28days of curing). Moreover, The UCS results of the stabilized soils were compared to the minimum strength requirements for both paved and unpaved road materials (i.e., 1380 and 690kPa, respectively). Finally, scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses were used to elucidate the changes in the microstructure of the stabilized soils.

Field measurement of effects of individual and combined application of biochar and polyacrylamide on erosion variables in loess and marl soils

Controlling soil erosion, especially in its initial stages, is greatly important in natural resources management. Consequently, the present research aimed to control splash and interrill erosion in two soil types (marl at Marzan-Abad and loess at Maraveh-Tapeh sites in northern Iran) using biochar (BC) and polyacrylamide (PAM). We established 0.5 × 0.5-m plots and applied BC (800 g·m−2), PAM (2 g·m−2), and BC + PAM (800 g·m−2 + 2 g·m−2) with control plots and three replications on a slope of ~25%. We used a rainfall simulator to achieve rainfall intensity of 50 mm·h−1 with 30-min duration in the experiments. Analysis of the results obtained from the variables of splash and interrill erosion during the rainfall-runoff process showed that the PAM significantly (p ≤ 0.05) increased all study variables of splash erosion. For interrill erosion, it reduced the variables of soil loss and sediment concentration. However, the difference was not significant (p > 0.05) compared to the control plot and runoff from the two treatment sites increased relative to that from the control plots. The plot treated with BC showed decreased runoff volume, runoff coefficient, and soil loss compared to the control plot at the Marzan-Abad site, but the differences were not statistically significant (p > 0.05). However, the plot in which loess soil was treated with BC at the Maraveh-Tapeh site exhibited considerably (p ≤ 0.05) increased runoff and soil loss compared to the control plot. The entire results verified a wide range for benefit reduction of study treatments from +25.09 to −37.49% for runoff and from +38.59 to −231% for soil loss with more effectiveness for Maraveh-Tapeh Loess soil as well as combined application of BC and PAM. These findings contribute to improved understanding of proper application of soil amendments to control runoff and soil loss in loam and loess soils.

Silene lulakabadensis (Caryophyllaceae), a New Species from Iran

Silene lulakabadensis Heidari, F. Ghahrem. &amp; Assadi is described as a new species from Zanjan Province, Iran. The new species is a dark green plant, perennial and woody at the base, that was collected on marl soil slopes at 2100 m. It is believed to be closely related to S. eriocalycina Boiss. from section Auriculatae (Boiss.) Schischk. but is a smaller plant, with much shorter internodes, and pinkish-white retuse to emarginate petals with very small or no scales. It is a very rare plant and its conservation status is assessed as Critically Endangered.

The Effects of Land Use Change on the Rainfall Erosion Processes in a Marl Soil under Simulated Rainfalls in the West of Zanjan

The Effects of Land Use Change on the Rainfall Erosion Processes in a Marl Soil under Simulated Rainfalls in the West of Zanjan

The Influence of Natural Pozzolans Structure on Marl Soil Stabilization

Marl as a calcareous soil has heterogeneous nature in terms of structure and properties. Any change in the water content of marl can cause significant strength loss; therefore, prior stabilization while constructing civil infrastructures is necessary. A fundamental element in soil stabilization is the relationship between soil structure and stabilizers, but this important factor has been ignored in the available literature, especially in the case of marl soil. Lately, alternative environmentally friendly additives (natural pozzolans) as well as traditional chemical stabilizers (cement and lime) have been successfully used for stabilization of marl soil. This paper presents the results of an experimental study which investigates the influence of natural pozzolans structure on marl soil stabilization. Transmission electron microscopy (TEM), X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR) tests were used for size and structure analysis of marl soil and two types of natural pozzolans called Qizkorpi and Mamaloo of Iran which have been successfully used for marl soil stabilization by the authors, recently. Based on the obtained results by TEM, FTIR, and XRF tests, due to the similarity of the structure and size of Gizkorpi volcanic ash and marl soil when compared to that of Mamaloo volcanic ash, it can be concluded that the electrostatic and magnetic interactions in marl and Gizkorpi volcanic ash lead to a better stabilization and strengthen of the marl, while these interactions are less in Mamaloo volcanic ash when mixed with the marl soil.

Effect of freeze-thaw cycles on characteristics of marl soils treated by electroosmosis application

Marly clay consists of 35 to 65% calcareous materials and it has a very low load bearing capacity, particularly after experiencing the freeze-thaw cycles. Since the presence of this soil may cause erosion and the probable succeeding destruction of foundations and embankments, and occurrence of tensile cracks in roads, the treatment of marl is desirable in construction. In this study, initial tests revealed that the Unconfined Compressive Strength (UCS) of a highly calcareous marl was dramatically decreased to almost zero only after the first freeze-thaw cycle. Afterwards, the marl samples were treated by electroosmosis application in an electroosmosis cell designed for this study. The effects of various voltage gradients of 0.46, 0.92 and 1.84 V/cm and the treatment periods of 1, 3 and 7 days on characteristics of marl were investigated experimentally. After the electroosmosis treatment, undisturbed samples were taken from the zones around anode, cathode and in-between of the poles. The UCS of the samples was measured after applying up to 16 freeze-thaw cycles. The results indicated that the electroosmosis treatment increased the load bearing capacity of the marl significantly. The UCS of a sample taken from around the anode increased by 2.8 times in comparison with the untreated one. As the best case, a seven-day application of electroosmosis under the voltage gradient of 0.92 V/cm showed a UCS value of about 271 kPa even after 16 freeze-thaw cycles.

Maxent Data Mining Technique and Its Comparison with a Bivariate Statistical Model for Predicting the Potential Distribution of Astragalus Fasciculifolius Boiss. in Fars, Iran

The identification of geographical distribution of a plant species is crucial for understanding the importance of environmental variables affecting plant habitat. In the present study, the spatial potential distribution of Astragalus fasciculifolius Boiss. as a key specie was mapped using maximum entropy (Maxent) as data mining technique and bivariate statistical model (FR: frequency ratio) in marl soils of southern Zagros, Iran. The A. fasciculifolius locations were identified and recorded by intensive field campaigns. Then, localities points were randomly split into a 70% training dataset and 30% for validation. Two climatic, four topographic, and eight edaphic variables were used to model the A. fasciculifolius distribution and its habitat potential. Maps of environmental variables were generated using Geographic Information System (GIS). Next, the habitat suitability index (HSI) maps were produced and classified by means of Maxent and FR approaches. Finally, the area under the receiver operating characteristic (AUC-ROC) curve was used to compare the performance of maps produced by Maxent and FR models. The interpretation of environmental variables revealed that the climatic and topographic parameters had less impact compared to edaphic variables in habitat distribution of A. fasciculifolius. The results showed that bulk density, nitrogen, acidity (pH), sand, and electrical conductivity (EC) of soil are the most significant variables that affect distribution of A. fasciculifolius. The validation of results showed that AUC values of Maxent and FR models are 0.83 and 0.76, respectively. The habitat suitability map by the better model (Maxent) showed that areas with high and very high suitable classes cover approximately 22% of the study area. Generally, the habitat suitability map produced using Maxent model could provide important information for conservation planning and a reclamation project of the degraded habitat of intended plant species. The distribution of the plants identifies the water, soil, and nutrient resources and affects the fauna distribution, and this is why it is relevant to research and to understand the plant distribution to properly improve the management and to achieve a sustainable management.

3D finite element modeling to predict the foamed sulfur asphalt marl soil mixes rutting behavior

Abstract This research was executed to predict and discuss the rutting behavior of marl soil treated with foamed sulfur asphalt (FSA) with the mixtures of the same soil treated with standard foamed asphalt (FA) for road bases structure. Marl soil-FA/FSA mixtures at their optimal binder contents were evaluated for creep tests at three different deviator stress and at 40 °C temperature. The wheel track test was conducted at 40 °C temperature. Rutting of the treated mixtures at their optimal asphalt contents was modeled using ABAQUS software and outputs of models were compared with the experimental observation and calibrated using wheel tracking tests results. The calibrated models can well predict the rutting performance of marl stabilized mixtures.