The effective dynamic viscosity of a soil-rock mixture (S-RM) serves as a essential parameter for simulating flowlike landslides in the context of fluid kinematics. Accurate measurement of this viscosity is significant for understanding the remote sustainability and rheological properties of landslide hazards. This study presents a method for determining dynamic viscosity, incorporating experimental measurements and numerical inversion. The experiment involves monitoring the movement of S-RMs with varying water content and rock block concentration, followed by the calculation of centroid displacements and velocities using digital image processing. The power-law model, combined with computational fluid dynamics, effectively captures the flow-like behavior of the S-RM. A grid search method is then employed to determine the optimal parameters by comparing the predicted centroid displacement with experimental results. A series of flume experiments were conducted, resulting in the observation of spatial mass distribution and centroid displacement variations over time during soil-rock movement. The dynamic viscosity model of the S-RM is derived from the experimental data. This dynamic viscosity model was then employed to simulate an additional flume experiment, with the results demonstrating excellent agreement between the simulated and experimental centroid displacements. Sensitivity analysis of the dynamic viscosity model indicates a dependence on shear rate and demonstrates a high sensitivity to water content and rock block concentration, following a parabolic trend within the measured range. This research contributes to the fields of geotechnical engineering and landslide risk assessment, offering a practical and effective method of measuring the dynamic viscosity of S-RM. Future research could explore additional factors influencing rheological behavior and extend the applicability of the proposed method to different geological environments.

A novel framework for nonlinear thermal elastic-viscoplastic (TEVP) constitutive relationships was proposed in this study, incorporating three distinct thermoplasticity mechanisms. These four TEVP formulations, combined with an existing TEVP constitutive equation presented in the companion paper, were integrated into a coupled consolidation and heat transfer (CHT) numerical model. The CHT model accounts for large strain, soil selfweight, creep strains, thermal-induced strains, the relative velocity of fluid and solid phases, varying hydraulic conductivity and compressibility during consolidation process, time-dependent loading, and heat transfer, including thermal conduction, thermo-mechanical dispersion, and advection. The performance of CHT model, incorporating different TEVP constitutive equations, was evaluated through comparing the simulation results with measurements from laboratory oedometer tests. Simulation results, including settlement, excess pore pressure and temperature profiles, showed good agreement with the experimental data. All four TEVP constitutive relationships produced identical results for the consolidation behavior of soil that in the oedometer tests. The TEVP constitutive equations may not have a significant effect on the heat transfer in soil layers because of the identical performance on simulating soil compression. The CHT model, incorporating the four TEVP constitutive equations, was then used to investigate the long-term consolidation and heat transfer behavior of a four layer soil stratum under seasonally cyclic thermal loading in a field test, with excellent agreement observed between simulated results and measured data.

Ground subsidence is a common urban geological hazard in several regions worldwide. The settlement of loess fill foundations exhibits more complex subsidence issues under the coupled effects of geomechanical and seepage-driven processes. This study selected 21 ascending Sentinel-1 A radar images from April 2023 to October 2024 to monitor the loess fill foundation in Shaanxi, China. To minimize errors caused by the orbital phase and residual flat-earth phase, this research combined PS-InSAR technology with the three-threshold method to improve the SBAS-InSAR processing workflow, thereby exploring time-series deformation of the loess fill foundation. Compared with conventional SBAS-InSAR technology, the improved SBAS-InSAR technique provided more consistent deformation time-series results with leveling data, effectively capturing the deformation characteristics of the fill foundation. Additionally, geographic information system (GIS) spatial analysis techniques and statistical methods were employed to analyze the overall characteristics and spatiotemporal evolution of the ground surface deformation in the study area. On the other hand, the major drivers of the subsidence in the study area were also discussed based on indoor experiments and engineering geological data. The results showed gradual and temporal shifts of the subsidence center toward areas with the maximum fill depths. In addition, two directions of uneven subsidence were observed within the fill foundation study area. The differences in the fill depth and soil properties caused by the building foundation construction were the main factors contributing to the uneven settlement of the foundations. Foundation deformation was also positively and negatively affected by surface water infiltration. This study integrates remote sensing and engineering geological data to provide a scientific basis for accurately monitoring and predicting loess fill foundation settlement. It also offers practical guidance for regional infrastructure development and geological hazard prevention.

The laboratory experiment is an effective tool for the rapid assessment of the unsaturated soil slopes instability induced by extreme weather events. However, traditional experimental methods for unsaturated soils, including the measurement of the soil-water characteristic curve (SWCC), soil hydraulic conductivity function (SHCF), shear strength envelope, etc., are time-consuming. To overcome this limitation, a rapid testing strategy is proposed. In the experimental design, the water saturation level is selected as the control variable instead of the suction level. In the suction measurement, the suction monitoring method is adopted instead of the suction control method, allowing for simultaneous testing of multiple soil samples. The proposed rapid testing strategy is applied to measure the soil hydro-mechanical properties over a wide suction/saturation range. The results demonstrate that: (1) only 3-4 samples and 2-5 days are in need in the measurement of SWCC; (2) 7 days is enough to determine a complete permeability function; (3) only 3 samples and 3-7 days are in need in the measurement of the shear strength envelope; (4) pore size/water distribution measurement technique is fast and recommended as a beneficial supplement to traditional test methods for unsaturated soils. Our findings suggest that by employing these proposed rapid testing methods, the measurement of pivotal properties for unsaturated soils can be accomplished within one week, thus significantly reducing the temporal and financial costs associated with experiments. The findings provide a reliable experimental approach for the rapid risk assessment of geological disasters induced by extreme climatic events.

In this study, a flexible vertical graphene (VG) strain sensor was developed for monitoring geogrids deformation. The VG material was fabricated using radio frequency plasma-enhanced chemical vapor deposition, followed by spin-coating a polydimethylsiloxane (PDMS) solution for film curing, resulting in a flexible sensor within a PDMS substrate. The VG sensor was integrated with a wireless Bluetooth data acquisition system for automated and remote strain measurement. The stability performance of VG sensors was examined and effectively improved through cyclic loading tests in the laboratory. The drift ratio of electrical resistance before cyclic loading tests is 37.01%, which is reduced to only 0.5% after cyclic loading tests. Calibration tests show that the maximum measurement resolution and maximum measurement range of VG sensors is 0.7 micro-strain and 40000 micro-strain, respectively, indicating that VG sensors are highly effective for both high-strain resolution identification and large-strain measurement. Pullout tests demonstrate an average error of 5.67% between VG sensors and fiber Bragg grating sensors, suggesting that VG sensors are a promising alternative for large strain, wireless, and long-term geogrid monitoring.

Research on conductive models of damaged soil that consider the effect of microcrack expansion (the degree of saturation and suction) is weak. By assuming an equivalent conductive path a unit series-parallel conductive model of damaged soil under environmental loads was proposed. This model shows the change in soil porosity and fractal dimension. To verify that, the soil was damaged by rainfall cycles (simulated natural drying and rainfall). Electrical measurements and X-ray microscopy tests were performed to obtain the damaged soil resistivity, porosity, and fractal dimension variation. The resistivity was calculated based on the conductive model, and the error was approximately 7.9% compared with that of the test. In addition, the soil damage variable related to soil porosity and fractal dimension was introduced, and it exhibited a logarithmic relationship with soil resistivity. Variations in soil damage during the rainfall cycles were observed. In the top layer, the soil porosity increased and the fractal dimension decreased owing to microcrack expansion, resulting in an increase in soil damage. In contrast, in the bottom layer, the soil porosity decreased and the fractal dimension increased, resulting in a decrease in soil damage due to particle migration from the top area and pore fill.

Environmentally persistent free radicals (EPFRs) are produced during biochar pyrolysis and, depending on biochar application, can be either detrimental or beneficial. High levels of EPFRs may interfere with cellular metabolism and be toxic, because EPFR-generated reactive oxygen species (e.g., hydroxyl radicals (center dot OH)) attack organic molecules. However, center dot OH can be useful in remediating recalcitrant organic contaminants in soils. Understanding the (system-specific) safe range of EPFRs produced by biochars requires knowing both the context of their use and their overall significance in the existing suite of environmental radicals, which has rarely been addressed. Here we place EPFRs in a broader environmental context, showing that biochar can have EPFR concentrations from 108-fold lower to 109-fold higher than EPFRs from other environmental sources, depending on feedstock, production conditions, and degree of environmental aging. We also demonstrate that center dot OH radical concentrations from biochar EPFRs can be from 104-fold lower to 1017-fold higher than other environmental sources, depending on EPFR type and concentration, reaction time, oxidant concentration, and extent of environmental EPFR persistence. For both EPFR and center dot OH concentrations, major uncertainties derive from the range of biochar properties and the range of data reporting practices. Controlling feedstock lignin content and pyrolysis conditions are the most immediate options for managing EPFRs. Co-application of compost to provide organics may serve as a postpyrolysis method to quench and reduce biochar EPFRs.

Earthquakes and rainfall both cause soil damage and strength degradation of cutting slopes, resulting in increased slope instability. However, few studies have been conducted on the failure mechanisms of cutting slopes under earthquakes and rainfall. In this study, field electrical measurements were conducted to evaluate the damage to a cutting slope hit by the Yangbi Earthquake (MS = 6.4) in Yunnan Province, China. After material segmentation using the resistivity probability density statistical method, we observed several damaged areas running along the slope depth direction, forming several potential sliding surfaces. Furthermore, considering the slope damage after the earthquake, a discrete element model of the slope was developed, and the dynamic process of the gravel-soil landslide under rainfall was analyzed. Compared with low cutting slope with thin overburden sliding along one sliding surface, the results indicate that the high cutting slope with thick overburden slides along several sliding surfaces that formed by the earthquake-step sliding mods. Slope sliding can be divided into four stages: First, the slope body at the bottom area slid and accelerated firstly, while several cracks appear on the top area due to tension (initial stage and acceleration stage). Thereafter, the upper slope body gradually slides along its respective sliding surface. The body at the bottom area of the slope was pushed by that at the upper area and slid at a high velocity along the sliding surfaces due to secondary acceleration (secondary acceleration stage). Finally, the sliding velocity of the slope gradually decreases, and an accumulation is formed, entering a stable stage (deceleration stage).

In this study, a novel 2D method for measuring soil surface suction, leveraging infrared thermal imaging technology is presented. The main principle of this method is the establishment of a correlation between soil surface water content and a normalized interfacial temperature difference. Subsequently, we link unsaturated soil surface suction to the normalized interfacial temperature difference through the soil-water characteristic curve. To validate the proposed method, an in-situ calibration test was conducted to ascertain the requisite parameters. Then, the method was tested under varying meteorological conditions at two distinct in-situ sites using the same test protocol as the calibration phase. The results demonstrate a strong agreement compared to measured values, affirming the feasibility and robustness of the proposed approach. This method offers several noteworthy advantages, including rapidity, non-contact operation, non-destructiveness, and robustness to environmental fluctuations. It holds promise for advancing investigation of the spatial and temporal evolution of hydro-mechanical properties of in-situ soil under the influence of climate change.

Electrical resistivity tests can potentially be applied in loess damage testing under combined freeze-thaw cycle (FTC) and earthquake conditions, which is crucial for preventing and controlling loess landslides. However, two challenges involving loess electrical resistivity measurements and damage characterization should be addressed. To achieve loess spatial resistivity measurements in extreme environments with low-uncertainty, a novel, multichannel, four-point method utilizing flexible electrodes is proposed. For loess damage characterization, a novel fusion algorithm is developed that integrates the electrical conductivity model with a data-driven process to eliminate the influence of moisture content and temperature on resistivity. To validate this approach, loess resistivity tests and damage characterizations were conducted using a combination of FTCs and earthquakes. The results indicate that the proposed method addresses the challenge of continuous measurement, ensuring that the discrepancy between the calculated and CT test results remains within an acceptable range, where the relative error ranged from 0 to 0.15. In addition, in the top and bottom areas, where considerable soil moisture exists, the calculation error associated with the previous empirical model was reduced considerably, with the relative error primarily ranging from 0.04 to 0.44.