Geotechnical Tests Research Articles

Influence of Static and Repeated Surface Surcharge Loadings on Tunnel Displacement Considering Small-Strain Stiffness of Soft Clay

With the rapid development of urban metro tunnels, the effect of surface surcharge loading on existing tunnels is unavoidable. Accurate evaluation of soil deformation and tunnel displacement under surface surcharge loading is of great significance for practical engineering. In this research, the effect of static and repeated surface surcharge loadings on tunnel displacement in soft clay was investigated numerically. The hardening soil model with small-strain stiffness (HSS model) was adopted to simulate the soil response. The parameters of the HSS model were obtained through geotechnical tests. The result indicates that Shanghai layer 4 soft clay exhibits large soil shear stiffness in the small strain range. Tunnel displacement is closely related to parameters of surface surcharge loading width, burial depth of tunnel, and the horizontal distance from the centerline. The overlapping influence range of tunnel displacement was proposed. Under repeated surface surcharge loadings, the first cycle of the repeated surface surcharge loading has the greatest effect on the tunnel displacement, and the subsequent cycles of loadings still cause further increases in the tunnel displacement. The effect of repeated surface surcharge loadings on tunnel displacement gradually decreases as the burial depth of tunnel and the number of cycles increase.

A Computationally Efficient Method to Determine the Probability of Rainfall-Triggered Cut Slope Failure Accounting for Upslope Hydrological Conditions

We present a new computationally efficient methodology to estimate the probability of rainfall-induced slope failure based on mechanical probabilistic slope stability analyses coupled with a hydrogeological model of the upslope area. The model accounts for: (1) uncertainty of geotechnical and hydrogeological parameters; (2) rainfall precipitation recorded over a period of time; and (3) the effect of upslope topography. The methodology provides two key outputs: (1) time-varying conditional probability of slope failure; and (2) an estimate of the absolute frequency of slope failure over any time period of interest. The methodology consists of the following steps: first, characterising the uncertainty of the slope geomaterial strength parameters; second, performing limit equilibrium method stability analyses for the realisations of the geomaterial strength parameters required to calculate the slope probability of failure by a Monte Carlo Simulation. The stability analyses are performed for various phreatic surface heights. These phreatic surfaces are then matched to a phreatic surface time series obtained from the 1D Hillslope-Storage Boussinesq model run for the upslope area to generate Factor of Safety (FoS) time series. A time-varying conditional probability of failure and an absolute frequency of slope failure can then be estimated from these FoS time series. We demonstrate this methodology on a road slope cutting in Nepal where geotechnical tests are not readily conducted. We believe this methodology improves the reliability of slope safety estimates where site investigation is not possible. Also, the methodology enables practitioners to avoid making unrealistic assumptions on the hydrological input. Finally, we find that the time-varying failure probability shows marked variations over time as a result of the monsoon wet–dry weather.

Possible remediation of impact-loading debris avalanches via fine long rooted grass: an experimental and material point method (MPM) analysis

Debris avalanches often originate along steep unsaturated slopes and have catastrophic consequences. However, their forecast and mitigation still pose relevant scientific challenges. This is also due to the variety of mechanisms observed near high sub-vertical bedrock outcrops, such as the impact loading of soil failed upslope the outcrop, the build-up of pore water pressures in the inception zone, and the bed entrainment along the landslide propagation path. At the University of Salerno, an experimental and numerical investigation campaign started some years ago to explore the feasibility of using long-root grass to mitigate or even inhibit the inception of debris avalanches. Previous laboratory results were achieved through two twin 2-m-long columns (one bare, one vegetated), where the change in soil retention curve and soil mechanical response was assessed. As follow-up, an experimental field setup was installed in 2020 first, and in an improved configuration in 2021. Here, three different species of long-root grass were grown. In situ soil suction and water content measurements were periodically collected in the vegetated and in the original soils. In both cases, soil specimens were also collected, and laboratory geotechnical tests were performed to individuate the changes in both the water retention and strength response. Increased values of soil suction and shear strength were outlined, despite some differences, for all the grown species compared to the original soil. Using these novel experimental data, advanced large-deformation stress–strain hydro-mechanically coupled analyses were recently performed through a material point method (MPM) approach. The original slope conditions were compared to various slope configurations engineered via long-root grass. The benefits and the open issues related to this novel green technology for landslide mitigation are discussed. Some insights are outlined for the possible reduction of the soil volumes mobilized inside the inception zone of debris avalanches.

Large-Scale Freezing and Thawing Model Experiment and Analysis of Water–Heat Coupling Processes in Agricultural Soils in Cold Regions

Heilongjiang Province, the largest commercial grain base in China, experiences significant challenges due to the environmental effects on its soil. The freezing and thawing cycle in this region leads to the transport of water and heat, as well as the exchange and transfer of energy. Consequently, this exacerbates the flooding disaster in spring and severely hampers farming activities such as plowing and sowing. To gain a better understanding of the freezing and thawing mechanisms of farmland soil in cold regions and prevent spring flooding disasters, this study focuses on Heilongjiang Province as a representative area in northeast China. The research specifically investigates the frozen and thawed soil of farmland, using a large-scale low-temperature laboratory to simulate both artificial and natural climate conditions in the cold zone. By employing the similarity principle of geotechnical model testing, the study aims to efficiently simulate the engineering prototypes and replicate the process of large-span and long-time low temperatures. The investigation primarily focuses on the evolution laws of key parameters, such as the temperature field and moisture field of farmland soil during the freeze–thaw cycle. The findings demonstrate that the cooling process of soil can be categorized into three stages: rapid cooling, slow cooling, and freezing stabilization. As the soil depth increases, the variability of the soil temperature gradually diminishes. During the melting stage, the soil’s water content exhibits a gradual increase as the temperature rises. The range of water content variation during thawing at depths of 30 cm, 40 cm, 50 cm, and 80 cm is 0.12% to 0.52%, 0.47% to 1.08%, 0.46% to 1.96%, and 0.8% to 3.23%, respectively. To analyze the hydrothermal coupling process of farmland soil during the freeze–thaw cycle, a theoretical model of hydrothermal coupling was developed based on principles of mass conservation, energy conservation, Darcy’s law of unsaturated soil water flow, and heat conduction theory. Mathematical transformations were applied after defining the relative degree of saturation and solid–liquid ratio as field functions with respect to the relative degree of saturation and temperature. The simulated temperature and moisture fields align well with the measured data, indicating that the water–heat coupling model established in this study holds significant theoretical and practical value for accurately predicting soil temperature and moisture content during the spring sowing period, as well as for efficiently and effectively utilizing frozen soil resources in cold regions.

Application of electrical resistivity tomography and geotechnical techniques for identification and characterization of collapsible soils in Bafoussam (Western, Cameroon)

Road failure catastrophes have increased in frequency in the West Cameroon area. The collapsed soil characteristics that contribute to these phenomena in Bafoussam have been investigated using the geophysical investigation combined with geotechnical tests. The result of electrical resistivity tomography shows water conditions and heterogeneity of road foundation materials: resistivity values higher than 200 Ωm indicate dry materials, values between 30 and 200 Ωm define wet materials, and values lower than 30 Ωm indicate the very wet or water-saturated materials. These water-saturated materials can therefore move, bounded by a sliding surface of high-resistivity materials. Geotechnical properties analysis shows that these materials are clayey-sensitive water (64% clay fraction; A-7-6), very plastic (liquid limit: 46–63% plasticity limit: 29–39%), compressible, with high porosity (e > 0.8), low shear strength, and high friction angle (24–37°). The quality of foundation materials associated with high slopes (> 40°) and heavy rainfall in wet seasons (July–October) means that seepage water is the main factor responsible for the mass movement observed on the road of Western Cameroon. The construction or rehabilitation of these roads should be carried out in compliance with the natural conditions of the project site.Article highlights- 2D Electrical Resistivity Tomography method is able to determine the nature, subsurface structure and water conditions of road foundation soils.- Geotechnical test can be used to define the physical and mechanical properties of road foundation soils.- These two techniques complement each other to understand the mass movement observed on two sections of road failures caused by seepage water.

Influence of Loess–Mudstone Strata Structure on Slope Seismic Stability of Loess Plateau in China

The widely distributed loess–mudstone strata structure in the Loess Plateau of China is one of the fundamental reasons for the susceptibility and group occurrence of seismic landslides in the area. This study took the loess landslides induced by the Haiyuan earthquake as a case study. Through extensive field investigations, the loess cover thickness, mudstone dip angle, slope height, and slope angle were chosen as the influencing factors. Together with mathematical statistics and geotechnical tests, two models, one of a loess–mudstone slope and the other of a pure loess slope, were constructed. Their seismic stabilities under different slope angles and slope heights were compared to analyze the influence of the underlying mudstone strata on the loess slope seismic stability. Meanwhile, a sensitivity analysis of these strata factors affecting the seismic stability of the loess–mudstone slope was carried out based on the orthogonal test. The results showed that ignoring the underlying mudstone strata would lead to smaller calculation results than the actual situation. The sensitivity influence of the factors on the loess–mudstone slope seismic stability comprised the slope angle, loess cover thickness, slope height, and mudstone dip angle from high to low.

SWRC interpretation of iron ore tailings blends focusing on saturation assessment of dry stacking

ABSTRACT The study addresses challenges in dry stacking of fine-grained materials by blending itabirite iron ore slime tailings with coarser flotation tailings. It focuses on flow dynamics, capillary saturation, and the necessity to prevent large, saturated volumes. Geotechnical tests were conducted on various blends, deriving unsaturated hydraulic conductivity functions using Fredlund and Xing’s methodology. The Soil-Water Retention Curve data, combined with transient 1D analysis, assesses capillary rise. Results show capillary rise up to 50 meters with over 80% saturation, and also influenced by weather conditions penetrating up to 20 meters. Integrating up to 30% slime content in flotation tailings mitigates saturation issues. Empirical and numerical findings enable inferring saturation tendencies in distinct iron ore tailings mixtures, establishing a procedural framework for practical field applications.

Experimental investigations on the physico-mechanical and microstructural properties of loess reinforced with anionic polyacrylamide

The typical characteristics of loess, such as macropores, weak cementation, and strong collapsibility, can adversely affect the stability of building foundations, transportation infrastructure, and other geotechnical systems. To address this problem, a water-soluble anionic polyacrylamide (APAM) was used to improve the characteristics of loess. A series of multi-scale geotechnical engineering tests, such as sedimentation column, zeta potential, Atterberg limits, standard compaction, permeability, triaxial compression strength, scanning electron microscope (SEM), nuclear magnetic resonance (NMR), and X-ray diffraction (XRD) tests were conducted on the loess samples. The results showed that the APAM polymer could flocculate fine loess particles into stable agglomerates via a series of physical actions, including charge neutralization, adsorption and bridging, and hydrophobic interactions. The contact form among the loess particles changed from loose point contact to strong mosaic contact with the addition of the APAM polymer, the surface porosity, fractal dimension, and interplanar spacing of the treatment material decreased significantly. The considerable improvement of loess microstructure affected its macroscopic physical and mechanical properties. The optimum moisture content and permeability coefficient of the treated loess decreased with the increases of the APAM content, whereas the plasticity index and maximum dry density increased. Additionally, the failure strength of the loess samples first increased then decreased as the APAM content increased, which showed the maximum value at an addition amount of 0.30% content, beyond which its strength value decreased. The test results demonstrated that the APAM polymer treatment could provide significant improvement in the macroscopic physico-mechanical and microstructural properties of loess. This study will serve as a crucial resource for loess foundation stabilization using the environmentally friendly and cost-effective polymer.

Editorial: Special Issue on Experimental Investigations from Very Small Strains to Beyond Failure

Abstract This Geotechnical Testing Journal Special Issue on Experimental Investigations from Very Small Strains to Beyond Failure presents selected papers originally submitted to the Eighth International Symposium on Deformation Characteristics of Geomaterials held in Porto, Portugal, from September 3–6, 2023 (IS-Porto 2023). This Symposium aimed at exploring and sharing ideas about the complex stress–strain response of geomaterials, including laboratory methods from very small to large strains; anisotropy and localization; time-dependent response of soils; characteristics of treated, unsaturated, and natural geomaterials; applications in field methods; evaluation of field performance in geotechnical structures; and physical and numerical modeling in geomechanics. The Symposium was a three-day event organized by the Faculty of Engineering of the University of Porto, under the auspices of the Technical Committee TC101 Laboratory Stress Strain Strength Testing of Geomaterials of the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE). This symposium was endorsed by the Portuguese Geotechnical Society (SPG), the Faculty of Engineering of the University of Porto (FEUP), under the activities of the Research Unit Institute of R&D in Structures and Construction (CONSTRUCT) of the Portuguese Foundation for Science and Technology (FCT). Building on the tradition of previous Symposia from Sapporo in 1994 to IS-Glasgow 2019, IS-Porto 2023 brought together more than 240 researchers and practitioners from 37 countries to share their experiences and explore new directions in testing, and in constitutive and numerical modelling of geomaterials. This Special Issue of ASTM International’s Geotechnical Testing Journal assembles eleven papers that illustrate some most recent, innovative, and significant advancements in laboratory equipment and experimental methodologies and procedures for the experimental investigations of soils from very small strains to beyond failure. Although most soil research laboratories are now equipped with the latest technology, in terms of transducers or testing apparatus, the inherent complex nature of soils makes studying them an ongoing challenge. This issue reflects the variety of topics that are still being considered, from difficult terrestrial soils, such as high plasticity stiff sedimentary clays (Sorensen et al. 2023), pumice soils (Hashimoto et al. 2023), gravelly (Nikoonejad and Mohsen Haeri 2023) and residual soils (Cheng and Leong 2023), and mine tailings (Narainsamy et al. 2023), to sampling and testing soils from Mars (Chaparro-López et al. 2023). Characterizing liquefiable soils, particularly partially saturated or gassy soils, and its post-liquefaction behavior continues to remain a subject of investigation, particularly in seismic regions, and is discussed in four papers, with emphasis on the applicability of partial saturation for liquefaction mitigation (Ahmad et al. 2023; Kaminski and Grabe 2023; Mele et al. 2023; Molina-Gómez et al. 2023). Greener methods of soil improvement are also explored, for example, biocementation under chemical damage (Ribeiro et al. 2023). The guest editors of this special issue would like to gratefully acknowledge the dedication and effort of all the authors and peer-reviewers of these papers, and the collaboration of the ASTM Editorial Team in the production of this special issue.

Editorial: 2023 Reviewer Thank Yous

Abstract The individuals listed here provided reviews for the papers in Volume 46 of the Geotechnical Testing Journal (GTJ). The Co-Editors of GTJ, Dr. Majdi Othman and Dr. Nazli Yesiller, express their appreciation to the reviewers for their diligence, assiduity, and professionalism in conducting the reviews. Detailed input and constructive criticism from the reviewers allow for maintaining the high quality of the journal. The time and efforts of the reviewers are acknowledged and greatly appreciated.

Research on the Prediction Model of Loess Collapsibility in Xinyuan County, Ili River Valley Area

Collapsibility is a unique engineering geological property of loess. Choosing appropriate parameters to build the prediction model of loess collapsibility is an essential step toward solving the loess collapsibility problem. A case study was performed for the loess in Xinyuan County of the Yili River Basin, China. A large amount of data was collected from preliminary geotechnical tests in this region. Mathematical statistics were applied to analyse the correlations between the loess collapsibility and soil parameters. Multiple linear regression and neural network theories were adopted to build this region’s prediction model of loess collapsibility. The results showed that microscopically, the soils in this region were predominantly flocculated structures. The soil particles were flaky and in bracket contact, and the pores were round or irregularly shaped. Regarding the material composition, the soils were primarily composed of quartz and albite, with a low hematite content. In the study area, the correlation coefficients between the collapsibility coefficient of the loess vs. the density, dry density, saturation, porosity ratio, and porosity varied between 0.628 and 0.857, indicating a strong or very strong correlation. In terms of predicting loess collapsibility, the effectiveness of neural networks based on RBF (radial basis function) and multiple linear regression models was contrasted. The latter was discovered to be more appropriate, dependable, and accurate, with an accuracy percentage of 94.42%. Simultaneously, the model’s assessment index is 0.014 for the root mean squared error (RMSE), 0.962 for the correlation coefficient (CC), 0.919 for the Nash–Sutcliffe efficiency coefficient (NSE), and −1.494 percent for the percent bias (PBIAS). It works well for estimating whether local loess may collapse. Therefore, the RBF neural network model built in the present study has adequate precision and meets the engineering requirements. Our research sheds new light on loess collapsibility assessment in this region.

Soil property recovery from incomplete in-situ geotechnical test data using a hybrid deep generative framework

Geotechnical testing serves to assess the strength and stiffness of in-situ soils, for purposes such as informing foundation design. Despite its importance, time constraints, financial considerations, and site-specific limitations often restrict testing to isolated locations with limited horizontal resolution. Therefore, this paper presents a novel hybrid generative deep learning model designed to approximate soil properties across sites based on sparsely sampled geotechnical data. The model uses geological subsurface samples derived from random field theory as ‘a priori’ data for a conditional variational auto-encoder (CVAE) model. By doing so, it attempts to map the relationship between in-situ data and the corresponding spatial coordinates, as well as the inherent link between in-situ data and spatial distribution. Then, in the post-processing phase, a Kriging model interpolates minor discrepancies between the measured and predicted values. To demonstrate its practical application, this paper focuses on cone penetration testing (CPT) as the geotechnical test method. The model's development is thoroughly discussed, followed by the validation using in-situ data and an analysis conducted with synthetic data. It is shown that the uncertainty associated with CVAE-Kriging depends upon both the distance from the sample point and the site's inherent complexity. The proposed methodology not only offers refined subsurface modeling but also expands the understanding of uncertainty in geotechnical testing. Practically, it can assist geotechnical engineers with insights during the survey phase.

Experimental study on stress distribution characteristics of a shield tunnel under passive failure

Urban rail transit construction will inevitably encounter tunnel working conditions with extremely complex surrounding environment and buried deep shield tunnel, and the stability of the tunnel surface cannot be ignored. A series of passive instability geotechnical model tests were carried out on the tunnel faces at different burial depths. The earth pressure, lateral earth pressure coefficient and soil arch area evolution law caused by passive instability of the tunnel face in sandy cobble stratum were studied. Once the preset position is reached, the rotation is stopped using the cutterhead and the screw excavator and the shield machine continues the jack, simulating passive instability of the tunnel face. The results show that the soil pressure in the horizontal earth pressure is significantly more affected by the passive instability of the tunnel face than the vertical direction. The soil in front of the excavation caused by the ejection of the shield machine is squeezed and moved forward, resulting in a decrease in horizontal earth pressure perpendicular to the direction of shield tunnel excavation. The results of the passive instability region obtained by numerical simulation are larger than those obtained by model experiments, because the numerical simulation method fails to consider the compacting effect caused by the extrusion of sandy cobble formations. It can be found that the uplift value of C/D = 1.0 is significantly greater than that of C/D = 1.5, which also confirms the conclusion that the instability area with a relatively small burial depth is larger and develops farther to the front of excavation.

Application of FEM tools in efficient field implementation of dynamic replacement of soft soils

ABSTRACT A dynamic finite element methodology (FEM) was developed to simulate an entire dynamic replacement (DR) program of clay with sand involving multiple poundings. The main objective of this research was to employ FEM and geotechnical test data such as cone penetration test (CPT) data at the site to predict the maximum achievable sand column (SC) depth and the corresponding optimum levels of attributing parameters such as number and height of pounder drops. Another goal was to predict the pore pressure generated in clay due to pounding. A full-scale ground improvement project was used to guide the analytical process. Comparison of FEM predictions and field measurements showed the potential of using FEM to achieve the above objectives in advance of the field work. Finally, a step – by-step procedure for using a FEM procedure to predict the optimum field setup and hence improve the efficacy of DR field implementation is illustrated.

Failure Mechanism and Deformation-Based Design of Narrow Geosynthetic Reinforced Soil Walls

In recent years, the working performance of mechanically stabilized earth (MSE) walls has shown their outstanding stability and capacity to accommodate large deformation. The behavior and failure mechanisms of conventional MSE walls have been carefully examined. In cases where space is limited, such as in mountainous regions, in coastal regions, and for road expansion, the conventional MSE wall can be modified by adjusting the length of reinforcement to conform the construction area. For narrow geosynthetic reinforced soil (GRS) wall, the modification and arrangement of reinforcement components, including reinforcement tensile strength, vertical spacing, and aspect ratio, play key roles in the behavior of reinforced earth walls and can also lead to differences in the distribution of lateral earth pressure compared with conventional MSE walls. In this study, a series of geotechnical centrifuge tests are conducted to clarify the failure behaviors, distribution of lateral earth pressure, and deformation progresses of narrow GRS walls. Among the investigated variants, it is verified that improved reinforcement strength leads to a significant decrease in horizontal wall displacement. The relationship among lateral earth pressure, zero-earth-pressure zone, and horizontal displacement can be applied to predict the deformation of a narrow GRS wall.

Relationship between resistivity and physical properties of seafloor sediments in the hydrate production test area of the South China Sea

The vast distribution, abundant reserves, and high combustion utilization rate of natural gas hydrate make it an appealing alternative energy source. Nevertheless, the special physical and mechanical properties of the hydrate production test area in the South China Sea have led to frequent geological disasters, requiring monitoring and early warning of potential geohazards. To facilitate this process, a model was established to determine the relationship between sediment resistivity and physical properties in this area. However, there is currently no suitable sediment resistivity inversion model for this region. We obtained an 8 m-long core sediment sample from the hydrate production test area in the South China Sea using a core sediment sampler aboard the research vessel “Marine Geology 6”. Indoor geotechnical tests were conducted to determine the vertical variation characteristics of the sediment, and indoor resistivity tests were performed to obtain its resistivity vertical variation. Using empirical power function formulae, we established a relationship model between resistivity and physical properties, which we then compared with relevant data from nearby sea areas. This model lays the foundation for using in situ resistivity to invert the dynamic changes of sediment physical properties and promote the development of deep-sea engineering geology.

Geotechnical laboratory testing of lunar simulants and the importance of standardization

A comprehensive program of geotechnical index tests performed on two regolith simulants, namely LHS-1 and LMS-1, are presented and discussed in this study. The index tests included a 2D analysis of particles shapes and measurements of grain density, particle size distribution, plastic and liquid limit, thermal conductivity, and maximum and minimum dry density. The detailed testing methodologies are provided, and their results are discussed and compared with data available in the literature from similar tests on the same regolith simulants. Additionally, a thorough analysis of the data in contrast with data of lunar soils is presented. The observed spread on the index tests results is explained by the indiscriminate use of different procedures, regolith mass, and methodologies across different laboratories and highlight the importance and urgency for planetary scientist to agree on best practices in geotechnical testing of regolith and extra-terrestrial simulants.

Subsurface Geotechnical Competence Evaluation Using Geoelectric Sounding and Direct Cone Penetrometer Test at Plural Garden Estate, Ilaramokin Southwestern Nigeria

In order to evaluate the geotechnical competence of the subsurface soil materials at Plural Garden Estate, Ilaramokin Southwestern Nigeria, geotechnical investigations involving geoelectric sounding and Direct Cone Penetrometer Test (DCPT) was carried out in the estate. A total of 27 VES points and 8 DCPT points were occupied across the study area. A, H, K, Q and KH are the five sounding curve types delineated in the area. Resistivity values of the top soil, weathered layer, fractured layer and fresh bedrock vary from 65-864, 156-1698, 28-217, 433-12167 ohm-m respectively, while their thicknesses vary from 0.7-3.7, 2.4-10.5 and 6.3-40.1 m in the upper three layers respectively. The geoelectric sounding results were presented as depth slices at depths of 0.5, 0.75, 1.0 and 2.0 m competency maps. Larger part (70 to 80 %) of the surfaces (1.0 and 2.0 m) considered in the study area are characterized as moderate to high competent. The depth slice iso-resistivity maps indicated that geotechnical competence increases with depth within the shallow depths considered (0.5, 0.75, 1.0 and 2.0 m). Geotechnical test involving DCPT were done at common depth of 1.0 m to validate the 1.0 m competency map. The DCPT agreed with the geoelectrical derived 1.0 m depth slice competence map. Some zones suspected to be very low and low competence were revealed to be competent based on DCPT suggesting that the low resistivity may be due to the presence of non-plastic clay and moisture.

WNMS: A New Basaltic Simulant of Mars Regolith

The use of planetary regolith can be explored via the utilization of simulants. The existing Martian simulants have differences due to varying source materials and design parameters. Additional simulants are needed because the few available simulants do not replicate the compositional diversity of Martian regolith. This study discusses the development of a low-cost construction simulant of Mars. The area of Winder Nai in Pakistan was selected for field sampling of basalt because of local availability and easy access. The dust was produced from rock samples through mechanical crushing and grinding. The physical properties, composition, mineralogy, and surface morphology were evaluated via geotechnical tests, Energy Dispersive X-ray (EDX) spectroscopy, X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM), respectively. The designed simulant has a well-graded particle size distribution with a particle density and bulk density of 2.58 g/cm3 and 1.16 g/cm3, respectively. The elemental composition of Winder Nai Mars Simulant (WNMS) is within ±5 wt% of the Rocknest and the average Martian regolith composition except for SO3. For SiO2, Al2O3, and Fe2O3, WNMS has a good match with the Martian regolith. The content of CaO and TiO2 in WNMS is higher than, and content of MgO is lower than, the average Martian values. The rock can be classified as basalt based on the Total Alkali Silica (TAS) diagram. XRD spectrum indicates the occurrence of plagioclase and pyroxene as the main signature minerals of basalt. The particle morphology of WNMS is angular to subangular, and the simulant indicates the presence of 3.8 wt% highly paramagnetic particles. The volatile loss is 0.25 wt% at 100 °C, 1.73 wt% at 500 °C, and 3.05 wt% at 950 °C. The composition of WNMS, basaltic mineralogy, morphology, magnetic properties, and volatile content are comparable with MMS-2 and a few other simulants.

Macro- and Micro-Characteristics and Mechanical Properties of Xigeda Formation Claystone in Luding County, Western Sichuan, China

Claystone is actually a type of hard soil or soft rock. To reveal the engineering geological characteristics of the Xigeda formation claystone in Luding County (Western Sichuan, China), some experiments, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and geotechnical tests, are performed. The testing results indicate that the Xigeda formation claystone primarily consists of silt, clay, and other fine-grained materials. It is characterized by interbedded yellow and gray thin layers with a horizontal lamination structure. The yellow and gray claystones are made of the same materials but differ in their proportions. Additionally, yellow claystone is characterized by a higher density, resulting in enhanced cementation among clay particles. The permeability coefficient of Xigeda formation claystones ranges from 3.62 × 10−4~7.34 × 10−4 cm/s. The cohesion of yellow and gray claystones decreases with increasing moisture content, and the decline is greater at higher moisture contents. However, the relationship between internal friction angle and moisture content is different. The mechanical properties of the Xigeda formation exhibit significant differences in sensitivity to changes in moisture content across various regions. Notably, the claystone within the study region experiences a particularly pronounced weakening of its mechanical properties when exposed to water.