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The study area in Bundu Tuhan mainly consists of the metasedimentary rock of the Trusmadi Formation. Trusmadi Formation aged Palaeocene to Middle Eocene made up of interbedded dark grey shale and thin sandstone that shows the characteristics of deep marine sediment. Shale bed also known as phyllite unit is the major rock unit in Trusmadi Formation that is usually weathered and produced clayey soil. Clayey soil is often acknowledged as problematic soil due to its properties that tend to hold water highly compared to sandy soil, which will cause further engineering problems due to the soil creeping. The study area is prone to landslide activity, especially in the Trusmadi Formation’s slopes. Hence, this paper aims to determine the engineering properties of clayey soil from the Trusmadi Formation. Two slopes were also selected for laboratory analysis and slope inventory. The results of the analysis show that both samples are poorly sorted materials which are classified as sandy and silty clay soil and silty clay soil. The moisture content is 25.98% to 37.10%, specific gravity ranged from 2.52 to 2.57, and plasticity index ranged from 21.68% to 23.91%. The soil has inactive to a normal type of clay (0.59 to 0.97) with a very high swelling capacity (9.29% to 11.43%). The maximum dry density (MDD) ranged from 1.44 to 1.53 and optimum moisture content (OMC) of 25.47% to 25.67%. Also, both samples are classified as impermeable soil with a K value ranging from 1.74x10 −8 m/s to 2.45x10 −8 m/s. While, based on the slope inventory inspection, both slopes were comprised of metagreywacke, where the first slope was an embankment slope, and the second slope was a cut slope. The first slope has poor vegetation cover which leads to moderate erosion and instability that further caused failure which is rotational debris slide. As for the second slope with average vegetation cover, there is only minor erosion and instability present on the slope, and this slope also shows slow soil movement that indicates soil creep.

The purpose of this study was to assess the performance of high water content clayey sediments at different liquid limits as the clays are treated with cement-based solidifying materials. Three clay samples are obtained from different locations in the Kumamoto Reservoir. Two types of cement-based solidifying agents, namely, ordinary Portland cement and a cement–fly ash binder, were used. Using the initial water content of clay and the mixing amount of the solidifying agent as experimental variables, a cone penetration test was performed on the solidifying agent-stabilized clays to obtain the cone index (qc). The results showed that when the water content to cementitious content ratio (w/AW) was used as a parameter for evaluating the improvement of solidifying agent-stabilized clay, different forms of improvements were observed when different water and solidifying agent contents were used. This implied that the parameter w/AW was not suitable for evaluating the improvement of such clay. A new parameter, K, representing the content of solidifying agent, was introduced to account for the water content. For all sampled clays, the correlation coefficients for the K–ln qc relationship exceeded 0.9. Considering the effect of the liquid limit of the samples, the modified content of the solidifying agent (KL) was introduced to evaluate the cone index of the stabilized soils. It was discovered that the proposed equation unified the assessment of the improvement of the three samples of Kumamoto clayey sediments owing to the new parameter, KL.

The number of sensors, ground-based and remote, exploiting the relationship between soil dielectric response and soil water content continues to grow. Empirical expressions for this relationship generally work well in coarse-textured soils but can break down for high-surface area and intricate materials such as clayey soils. Dielectric mixing models are helpful for exploring mechanisms and developing new understanding of the dielectric response in porous media that do not conform to a simple empirical approach, such as clayey soils. Here, we explore the dielectric response of clay minerals and clayey soils using the mixing model approach in the frequency domain. Our modeling focuses on the use of mixing models to explore geometrical effects. New spectroscopic data are presented for clay minerals (talc, kaolinite, illite and montmorillonite) and soils dominated by these clay minerals in the 1 MHz–6 GHz bandwidth. We also present a new typology for the way water is held in soils that we hope will act as a framework for furthering discussion on sensor design. We found that the frequency-domain response can be mostly accounted for by adjusting model structural parameters, which needs to be conducted to describe the Maxwell–Wagner (MW) relaxation effects. The work supports the importance of accounting for soil structural properties to understand and predict soil dielectric response and ultimately to find models that can describe the dielectric–water content relationship in fine-textured soils measured with sensors.

Unconfined compressive strength (UCS) can be used to assess the applicability of geopolymer binders as ecologically friendly materials for geotechnical projects. Furthermore, soft computing technologies are necessary since experimental research is often challenging, expensive, and time-consuming. This article discusses the feasibility and the performance required to predict UCS using a Random Forest (RF) algorithm. The alkali activator studied was sodium hydroxide solution, and the considered geopolymer source material was ground-granulated blast-furnace slag and fly ash. A database with 283 clayey soil samples stabilized with geopolymer was considered to determine the UCS. The database was split into two sections for the development of the RF model: the training data set (80%) and the testing data set (20%). Several measures, including coefficient of determination (R), mean absolute error (MAE), and root mean square error (RMSE), were used to assess the effectiveness of the RF model. The statistical findings of this study demonstrated that the RF is a reliable model for predicting the UCS value of geopolymer-stabilized clayey soil. Furthermore, based on the obtained values of RMSE = 0.9815 and R2 = 0.9757 for the testing set, respectively, the RF approach showed to provide excellent results for predicting unknown data within the ranges of examined parameters. Finally, the SHapley Additive exPlanations (SHAP) analysis was implemented to identify the most influential inputs and to quantify their behavior of input variables on the UCS.

The interest of people in consuming their own agricultural products is on the rise, leading to an increase in the number of urban gardens established in Bogotá over the past years. These gardens operated using the biointensive method as a model for urban agriculture present an environmentally sustainable alternative. However, this system comes with challenges and limitations that may hinder the establishment of such a project. To test this, an urban garden focused on biosystems with high levels of agricultural biodiversity was established within a greenhouse of the Universidad Nacional de Colombia, Bogotá campus. This was carried out in an area with a covered and an uncovered section. A weed germination trial was conducted in planting containers, assessing the relative representation of weeds in two random samplings taken from different containers over a two-month measurement period and a previous soil analysis was realized to evaluate the physical and chemical conditions of the soil. Consequently, 13 weed species were identified in the soil bank of weeds, with Veronica spp. being the most relatively represented in both samplings. However, within the established orchard, the predominant plants were those belonging to the Poaceae family, such as Lolium temulentum and Cenchrus clandestinus. Finally, through the biointensive method and the addition of organic materials such as biochar and regular topsoil, soil properties like structure, porosity, and friability were improved. This, in turn, enabled better root development and the successful establishment of various cultivars in the garden.

Clays from the Saiss basin (northern Morocco) used traditionally in the ceramic industry in the Fez area were studied using mineralogical and physicochemical techniques to evaluate their potential suitability as raw materials for ceramics manufacture. X-ray diffraction was used to determine their mineralogical composition. The physical properties determined were particle-size distribution and consistency limits. The chemical composition was determined using X-ray fluorescence analysis and Fourier-transform infrared spectrometry. The structural changes of the mineral phases in the raw materials during firing were studied over a temperature range of 500-1000°C. In the pottery site from Fez, generally potters use a mixture of 25% fine clay (ARFS) from the upper part of the Miocene marls and 75% sandy clay (ARFR) from the lower part of the Miocene marls. The ARFS clay yielded very rigid specimens after firing that artisan potters would find difficult to handle so as to produce desired shapes and sizes. However, the specimens obtained from ARFR clay show signs of faltering. The mixture of these two clayey materials from this pottery site is therefore necessary to obtain the optimal paste for ceramics purposes. The chemical compositions indicated that SiO2, Al2O3, CaO and Fe2O3 are the major minerals, with trace amounts of K2O and MgO. Quartz, feldspars and clay minerals prevail in all samples. Kaolinite, illite and smectite are the dominant clay mineral phases, with traces of chlorite and interstratified illite-smectite. The classification of these samples using appropriate ternary diagrams showed that the proportions used in the mixture produce a new material with adequate characteristics for the production of traditional ceramics.

The mass transfer mechanisms in landslides are complex to monitor because of their suddenness and spatial coverage. The active clayey Harmalière landslide, located 30 km south of Grenoble in the French Alps, exhibits two types of behavior: in its upper part, decameter-sized clay blocks slide along a listric slip surface, while a flow-like mechanism is observed in a clayey remolded material a few hundred meters below the headscarp. The landslide underwent a major retrogression affecting 45 ha in March 1981 and has experienced multiple reactivations since then. The last major event took place on the 26th of June 2016, and a large investigation survey was conducted to better understand the reactivation mechanism. A multi-method investigation was carried out at different temporal and spatial scales, including aerial photograph and light detection and ranging processing, correlation of optical satellite images, global navigation satellite system monitoring, continuous seismic monitoring, and passive seismic survey. The morphological evolution of the landslide was traced over the last 70 years, showing a headscarp retrogression of 700 m during multiple reactivations and a total mass transfer of more than 6 × 106 m3. The detailed study of the 2016 event allowed to track and understand the mechanism of a mass transfer of 1 × 106 m3 in 5 weeks, from a sliding mechanism at the headscarp to an earthflow at the toe.

Sand production is a crucial geotechnical issue for safe and efficient gas recovery from natural gas hydrate (NGH) reservoirs. Although the same gas production method of depressurization was chosen for the production trials in the Nankai Trough and the Northern South China Sea, their sand production behaviors differed greatly due to the skeleton diversity of sand in the Nankai Trough and clayey‐silt in the Northern South China Sea, which resulted in different sand control and sand production characteristics. In this study, we conducted experiments to compare sediment responses and sand production behaviors from these two typical gas hydrate‐bearing sediments (GHBSs) before, during, and after hydrate dissociation under depressurization. The results reveal the fluid and sand production rates in both GHBSs are relatively low before and after hydrate dissociation. However, the sand production rate in sandy GHBS keeps stable at a relatively high value during the whole hydrate dissociation period, accompanied by a high fluid production rate and continuous sample subsidence. In contrast, the fluid and sand production rates are proved to be high only at the early stages of hydrate dissociation in clayey‐silty GHBS with sand production decreasing obviously afterward, and the sample subsidence rate exponentially decay until the ultimate subsidence is reached. After experiments, two kinds of particle plugging phenomena, sand bridge and mud cake, are found to form outside sand screens in sandy and clayey‐silty GHBSs, respectively. Differences in permeability, particle migration, and plugging characteristics are thought to be the main inducement of the variability in sand production behaviors in different GHBS types. These findings indicate that sand‐production control strategies should obey geological engineering integration and differ according to the GHBS type. Specifically, we should concern sand production risk in sandy GHBS during and after hydrate dissociation, whereas more attention should be paid to the early stages of hydrate dissociation in clayey‐silty GHBS. In this study, we conducted experiments to compare sediment responses and sand production behaviors from these two typical gas hydrate‐bearing sediments before, during, and after hydrate dissociation under depressurization.

Stabilization of soil using cement can increase the bearing capacity, compaction, and strength characteristics. However, limited research has been conducted on cemented clayey sand, and there is a lack of knowledge of the combined effect of clay content and cement content on the strength and deformability characteristics of mixed soil. In the present study, two soil mixtures were prepared: (1) Soil A consists of 80% sand and 20% clay, and (2) Soil B consists of 60% sand and 40% clay. The prepared mixtures were stabilized by Portland cement at target ratios of 1%, 2%, and 3% by dry weight, and they were cured for 7, 14, and 28 days. A series of unconfined compression tests were performed on the untreated and cement-treated specimens. There was a continuous increase in the unconfined compressive strength (UCS) with the increase in cement content, clay content or curing period. The deformability index rose with the growth of the clay content, but it decreased over time with increasing the curing period. Two empirical equations have been developed on the basis of the cement and clay contents to predict the UCS of cemented clayey sand at any curing time (≤ 28 days). Keywords: Clayey sand, Cement stabilization, Compaction tests, Unconfined compressive strength, Deformability index, Energy absorption capacity.

Accelerating creep before catastrophic failure commonly follows a power‐law velocity‐acceleration relationship, with the exponent typically near 2 but often evolving from 1 to 2 at a certain point, indicating a dynamic transition. The underlying mechanisms, however, remain unclear. Here we investigate this transition by monitoring the slip displacement of clayey soil during fluid‐injection creep experiments. This transition is discontinuous in the first run but becomes continuous in the initially pre‐sheared sample. Using a regularized rate‐and‐state friction model, we explicitly examine the relationship between the exponent and the frictional properties of the soil. This model describes the dynamic transition, with the exponent evolving from 1 to 2 across a broad range of frictional parameters. Furthermore, by incorporating idealized shear localization processes, the model qualitatively reproduces the shear‐history‐dependent transition. Our study demonstrates that a combination of structural evolutions and frictional properties may explain slow and fast slips observed in various shear systems. Plain Language Summary Predicting when materials will fail or natural hazards will occur is complex because it involves various physical processes and parameters. An empirical power‐law velocity‐acceleration relationship has proven effective and reliable for forecasting creep failure and natural events like landslides and volcanic eruptions. Although its exponent is typically 2, it can evolve from 1 to 2 over time, indicating a dynamic transition between two distinct acceleration regimes. In our fluid‐injection experiments on clayey soil, we observe a slow‐to‐fast transition in slip displacement and a multi‐layered shear zone. This transition is initially discontinuous but becomes continuous when the sample is pre‐sheared. To elucidate the mechanism, we use a slider block to simplify landslide movement, with the friction of the slip surface governed by a regularized rate‐and‐state friction model. For a velocity‐weakening slip surface, this model predicts a shift from velocity‐independent to velocity‐weakening steady‐state friction, demonstrating a continuous slow‐to‐fast transition with the exponent evolving from 1 to 2. Furthermore, the combination of friction and shear localization processes qualitatively reproduces the discontinuous transition observed in experiments. These results indicate that slow and fast slips can be modulated by both frictional property and structural evolution, encouraging the consideration of their combined effects. Key Points Fluid‐injection creep experiments on clayey soil show two distinct acceleration regimes, with a dynamic transition based on shear history The regularized rate‐and‐state friction model describes the power‐law velocity‐acceleration relationships and exponents for both regimes The model, coupled with idealized shear localization in a multilayer structure, qualitatively reproduces the history‐dependent transitions