Shear wave velocity (Vs) is an essential parameter for soil strength and mechanical properties of rocks. Twenty profiles of multichannel analysis of surface waves (MASW), five microtremor measurements, and two geotechnical boreholes have been conducted at the King Saud University site. According to the National Earthquake Hazards Reduction Program classification, the results indicated three distinct layers. The first layer is comprised of silty sand with gravel and thickness ranges of 4-14 m of shear wave velocity (Vs) from 400 to 760 m/s, indicating site C class; the second layer features highly weathered limestone where Vs varies between 760 and 1500 m/s refers B class, while the third layer consists of compact/massive limestone where Vs varies from 1500 to 3500 m/s representing site A class. The bedrock varies in depth from south to north, showing the shallowest depth in the central zone. Moreover, the estimated shear wave velocity and bedrock depth from microtremor measurements agree with MASW results. These results specified distinct weak zones at depths ranging from 2 to 25 m through the study area, emphasizing potential geotechnical concerns associated with these weak zones. Integrating shear wave velocity and microtremor measurements is crucial for advancing sustainable urban development by providing more informed design choices considering local soil conditions. This highlights the significance of geophysical techniques in supporting sustainable development initiatives.

Lunar core samples are the key materials for accurately assessing and developing lunar resources. However, the difficulty of maintaining borehole stability in the lunar coring process limits the depth of lunar coring. Here, a strategy of using a reinforcement fluid that undergoes a phase transition spontaneously in a vacuum environment to reinforce the borehole is proposed. Based on this strategy, a reinforcement liquid suitable for a wide temperature range and a high vacuum environment was developed. A feasibility study on reinforcing the borehole with the reinforcement liquid was carried out, and it is found that the cohesion of the simulated lunar soil can be increased from 2 to 800 kPa after using the reinforcement liquid. Further, a series of coring experiments are conducted using a self-developed high vacuum (vacuum degree of 5 Pa) and low-temperature (between -30 and 50 degrees C) simulation platform. It is confirmed that the high-boiling-point reinforcement liquid pre-placed in the drill pipe can be released spontaneously during the drilling process and finally complete the reinforcement of the borehole. The reinforcement effect of the borehole is better when the solute concentration is between 0.15 and 0.25 g/mL. (c) 2025 Published by Elsevier B.V. on behalf of China University of Mining & Technology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

The S-wave velocity (SWV) is a crucial parameter in seismic site characterization and seismic microzonation. In Varanasi city, we determined the shear wave velocity through a dual approach, employing joint inversion of microtremor array survey and the Horizontal to Vertical Spectral Ratio (HVSR) method. This combined analysis from two distinct methods enhances the reliability of our S-wave velocity model for the subsurface soil strata. To assess the S-wave velocity profile in shallow subsurface soil layers, we conducted forward and inverse modelling of geophysical data. This evaluation was cross-referenced with geotechnical borehole data to ensure accuracy. Microtremor measurements were conducted at 115 single stations and 12 array stations in the city. Joint modelling of HVSR and Rayleigh wave phase velocity dispersion provided insights into the site characteristics. Utilizing neighbourhood algorithms, we inverted dispersion curves from microtremor array measurements to obtain the S-wave velocity profile. The results were validated using geotechnical borehole data in the study area. The microtremor-derived S-wave velocity disclosed significant impedance contrasts in the topsoil layer, reaching a depth of approximately 12 m, with velocities ranging from 180 to 250 m/s. The second layer, extending to around 40-50 m, exhibited velocities between 300 and 400 m/s, while the bottom layer surpassed 600 m/s. Comparisons with SPT-derived S-wave velocity confirmed a well-correlated S-wave velocity profile for the top layer. The various methods converged to an average S-wave velocity of 360 m/s up to a depth of 50 m.

This study utilized electrical resistivity imaging (ERI) to investigate subsurface characteristics near Nicolaus Copernicus University Polar Station on the western Spitsbergen-Kaffi & oslash;yra Plain island in the Svalbard archipelago. Surveys along two lines, LN (148 m) collected in 2022 and 2023, and ST (40 m) collected in 2023, were conducted to assess resistivity and its correlation with ground temperatures. The LN line revealed a 1- to 2-m-thick resistive unsaturated outwash sediment layer, potentially indicative of permafrost. Comparing the LN resistivity result between 2022 and 2023, a 600 Ohm.m decrease in the unsaturated active layer in 2023 was observed, attributed to a 5.8 degrees C temperature increase, suggesting a link to global warming. ERI along the ST line depicted resistivity, reaching its minimum at approximately 1.6 m, rising to over 200 Ohm.m at 4 m, and slightly decreasing to around 150 Ohm.m at 7 m. Temperature measurements from the ST line's monitoring strongly confirmed that the active layer extends to around 1.6 m, with permafrost located at greater depths. Additionally, water content distribution in the ST line was estimated after temperature correction, revealing a groundwater depth of approximately 1.06 m, consistent with measurements from the S4 borehole on the ST line. This study provides valuable insights into Arctic subsurface dynamics, emphasizing the sensitivity of resistivity patterns to climate change and offering a comprehensive understanding of permafrost behavior in the region.

Background Loess is prone to large deformation and flow slide due to natural and artificial interfaces inside. The strength of these interfaces controls the mechanical properties of loess. Obtaining their mechanical parameters through in-situ testing is essential for evaluating the mechanical stability in loess engineering with interfaces. Methods By developing a borehole micro static cone penetration system and creating various types of loess with interfaces, extensive borehole penetration model tests were conducted to observe changes in cone tip resistance during penetration. The response surface method was used to analyze the impact of various test conditions on the calculated resistance. A three-dimensional surface fitting method was employed to establish the relationship between penetration parameters and shear strength parameters, which was validated through in-situ testing. Results The developed borehole micro static cone penetration system achieves overall miniaturization while providing significant penetration power and ensuring an effective penetration distance. Cone tip resistance development during penetration can be divided into three stages: initial, rapid increase, and slow increase. The transition times between these stages vary for different soils. Calculated resistance is positively correlated with dry density and normal stress and negatively correlated with water content. A quadratic positive correlation was established between calculated resistance and shear strength parameters during penetration. In composite soils, the interaction between water content and normal stress is strong. Compared to intact soil samples, the shear strength parameters of composite soils are more prominently influenced by water content. Conclusion A system for testing interface mechanical parameters was innovatively developed, fulfilling the need to obtain interface shear strength parameters for deep soil. This study can provide support for ensuring the long-term stability of the loess slope or subgrade with interfaces.

Reconstructing historical climate change from deep ground temperature measurements in cold regions is often complicated by the presence of permafrost. Existing methods are typically unable to account for latent heat effects due to the freezing and thawing of the active layer. In this work, we propose a novel method for reconstructing historical ground surface temperature (GST) from borehole temperature measurements that accounts for seasonal thawing and refreezing of the active layer. Our method couples a recently developed fast numerical modeling scheme for two-phase heat transport in permafrost soils with an ensemble-based method for approximate Bayesian inference. We evaluate our method on two synthetic test cases covering both cold and warm permafrost conditions as well as using real data from a 100 m deep borehole on Sardakh Island in northeastern Siberia. Our analysis of the Sardakh Island borehole data confirms previous findings that GST in the region have likely risen by 5-9 degrees C between the pre-industrial period of 1750-1855 and 2012. We also show that latent heat effects due to seasonal freeze-thaw have a substantial impact on the resulting reconstructed surface temperatures. We find that neglecting the thermal dynamics of the active layer can result in biases of roughly -1 degrees C in cold conditions (i.e., mean annual ground temperature below -5 degrees C) and as much as -2.6 degrees C in warmer conditions where substantial active layer thickening (>200 cm) has occurred. Our results highlight the importance of considering seasonal freeze-thaw in GST reconstructions from permafrost boreholes. Plain Language Summary Long-term changes in the temperature of the atmosphere are recorded in the solid Earth due to the insulating properties of soil and rock. As a result, it is possible to estimate past changes in temperature at the interface between the ground and the atmosphere by measuring ground temperatures deep below Earth's surface. In cold regions, the presence of permafrost, that is, ground that remains frozen throughout the year, complicates such analyses due to the effects of water freezing and thawing in the soil. In this work, we present a new method for reconstructing past changes in ground surface temperature from boreholes situated in permafrost using a computational model of heat flow that accounts for these effects. We evaluate our method on both synthetic test cases as well as real data from a 100 m deep borehole in northeastern Siberia. Our results demonstrate that annual freezing and thawing of water near the surface has a substantial impact on the reconstructed ground surface temperature (GST), especially in regions where permafrost is thawing. The proposed method is the first to be widely applicable to ground temperatures measured in permafrost and thus constitutes a valuable new tool for understanding past and present climate change in cold regions.

This study aims to investigate the feasibility of deriving in situ horizontal stresses from the breakout width and depth using the analytical method. Twenty-three breakout data with different borehole sizes were collected and three failure criteria were studied. Based on the Kirsch equations, relatively accurate major horizontal stress (a H ) estimations from known minor horizontal stress (a h ) were achieved with percentage errors ranging from 0.33% to 44.08% using the breakout width. The Mogi-Coulomb failure criterion (average error: 13.1%) outperformed modi fied Wiebols-Cook (average error: 19.09%) and modi fied Lade (average error: 18.09%) failure criteria. However, none of the tested constitutive models could yield reasonable a h predictions from known a H using the same approach due to the analytical expression of the redistributed stress and the nature of the constitutive models. In consideration of this issue, the horizontal stress ratio (a H /a h ) is suggested as an alternative input, which could estimate both a H and a h with the same level of accuracy. Moreover, the estimation accuracies for both large-scale and laboratory-scale breakouts are comparable, suggesting the applicability of this approach across different breakout sizes. For breakout depth, conformal mapping and complex variable method were used to calculate the stress concentration around the breakout tip, allowing the expression of redistributed stresses using binomials composed of a H and a h . Nevertheless, analysis of the breakout depth stabilisation mechanism indicates that additional parameters are required to utilise normalised breakout depth for stress estimation compared to breakout width. These parameters are challenging to obtain, especially under field conditions, meaning utilising normalised breakout depth analytically in practical applications faces signi ficant challenges and remains infeasible at this stage. Nonetheless, the normalised breakout depth should still be considered a critical input for any empirical and statistical stress estimation method given its signi ficant correlation with horizontal stresses. The outcome of this paper is expected to contribute valuable insights into the breakout stabilisation mechanisms and estimation of in situ stress magnitudes based on borehole breakout geometries. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

This paper critically evaluates and proposes innovative approaches to address the technical challenges associated with extracting existing piles and backfilling the associated boreholes, specifically in the context of Japan. Japan's rapid post-war economic growth has resulted in an infrastructure that is now aging, necessitating the demolition and subsequent reuse of structures. The prevalent use of pile foundations in soft soil conditions in Japan presents unique challenges following demolition, including differential settlement and complications for future construction on the same site. Current practices in Japan for pile removal are outdated and rely heavily on field experience without the support of standardized guidelines, leading to unresolved issues in improving the removal process. This paper provides an in-depth review of the status of technological advances in pile extraction and removal, as well as the development of backfill materials, with a focus on Japan's unique geological, demographic, and urban development factors. It highlights the risks associated with the traditional wire rope method and presents an innovative pile tip gripping and lifting method that aims to improve safety and efficiency by minimizing friction and preventing accidents. It also discusses the critical role of backfill treatment in preventing subsidence and outlines the performance requirements for fill materials, emphasizing the need for materials that provide uniform strength, prevent material segregation, and resist groundwater infiltration. Specifically, the paper discusses the development of cement-based fillers for borehole backfilling in Japan and demonstrates the effectiveness of sodium carbonate and thickeners in improving the physical and rheological properties of cement slurries. Finally, the paper emphasizes the urgent need for innovative technologies and methodologies for pile extraction, removal, and borehole backfilling in the Japanese context, highlighting their importance in ensuring safe, sustainable, and efficient land use in urban areas while addressing environmental concerns and stakeholder interests in land transactions and construction projects.

Borehole instability in naturally fractured rocks poses significant challenges to drilling. Drilling mud invades the surrounding formations through natural fractures under the difference between the wellbore pressure (Pw) and pore pressure (Pp) during drilling, which may cause wellbore instability. However, the weakening of fracture strength due to mud intrusion is not considered in most existing borehole stability analyses, which may yield significant errors and misleading predictions. In addition, only limited factors were analyzed, and the fracture distribution was oversimplified. In this paper, the impacts of mud intrusion and associated fracture strength weakening on borehole stability in fractured rocks under both isotropic and anisotropic stress states are investigated using a coupled DEM (distinct element method) and DFN (discrete fracture network) method. It provides estimates of the effect of fracture strength weakening, wellbore pressure, in situ stresses, and sealing efficiency on borehole stability. The results show that mud intrusion and weakening of fracture strength can damage the borehole. This is demonstrated by the large displacement around the borehole, shear displacement on natural fractures, and the generation of fracture at shear limit. Mud intrusion reduces the shear strength of the fracture surface and leads to shear failure, which explains that the increase in mud weight may worsen borehole stability during overbalanced drilling in fractured formations. A higher in situ stress anisotropy exerts a significant influence on the mechanism of shear failure distribution around the wellbore. Moreover, the effect of sealing natural fractures on maintaining borehole stability is verified in this study, and the increase in sealing efficiency reduces the radial invasion distance of drilling mud. This study provides a directly quantitative prediction method of borehole instability in naturally fractured formations, which can consider the discrete fracture network, mud intrusion, and associated weakening of fracture strength. The information provided by the numerical approach (e.g. displacement around the borehole, shear displacement on fracture, and fracture at shear limit) is helpful for managing wellbore stability and designing wellbore-strengthening operations. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

South Korea has implemented borehole -type seismometers for reliable earthquake observations and earthquake early -warning systems, with approximately 85% of seismometers being replaced by borehole -type seismometers after the Gyeongju earthquake. Although these seismometers are more effective at detecting earthquakes owing to the reduced artificial ambient noise, they do not record surface -level shaking. Therefore, it is necessary to estimate ground surface shaking directly associated with potential damage when using borehole -type seismometers without surface sensors. This study investigated and compared various methods, including the stochastic point -source ground -motion model, transfer function based on ambient noise, and one-dimensional site response, to estimate horizontal seismograms of the ground surface. We assessed the accuracy of these methods by comparing the waveforms generated in event cases (magnitude from 2.5 to 5.8, with epicentral distances spanning 22 km - 209 km) in terms of Fourier spectra, intensity, and spectral acceleration. Among the methods assessed, the transfer function approach, which does not account for the geophysical characteristics such as V S 30 , proved to be the most appropriate for correcting ground -surface effects.