In this study, the role of zeolite and polyvinyl alcohol (PVA) fibers on the durability of cement-stabilized clayey sand soil under freeze-thaw and wet-dry cycles was investigated. Laboratory tests, including unconfined compressive strength (UCS), scanning electron microscope (SEM), and ultrasonic pulse velocity (UPV), were performed to evaluate the effect of zeolite replacement ratio and fiber content on the durability and mechanical characteristics of the stabilized soil. The results showed that the mechanical properties of cemented samples decreased significantly under wet-dry cycles compared to freeze-thaw cycles. The optimal zeolite replacement ratio to achieve the most appropriate durability behavior of cement-treated clayey sand was 20%. Compared to the unreinforced samples, the samples with 0.8% fibers showed a lower reduction in UCS and mass loss under wet-dry and freeze-thaw cycles. The reduction in UCS was limited to 13% and 15%, respectively. The mass loss was limited to 5.2%, which indicates the positive effect of fibers in improving the durability of soil. Samples containing zeolite and fibers had lower mass loss in wet-dry and freeze-thaw conditions than samples without zeolite and fibers. Finally, the SEM microstructural observations justified the results of the durability tests.

An experimental study was conducted to evaluate the effects of crumb rubber (CR) on mechanical properties of roller compacted concrete (RCC) for use in pavements. In the experiment, proportions of 0%, 10%, 20% and 30% by volume (vol) CR, were incorporated into RCC as sand replacement material. Mixtures were made at cement contents of 275 kg/m3 (11%) and 201 kg/m3 (8.6%). The water content quantities used to prepare RCC mixtures, were determined from the moisture-dry density relationship obtained based on the soil compaction approach. Various mechanical properties were measured comprising compressive strength, splitting tensile strength, ultrasonic pulse velocity, static and dynamic moduli of elasticity. Also measured were pore-related physical tests consisting of water absorption and volume of permeable pores. It was found that cement content has significant influence on the amount of CR that can be suitably utilized in RCC mixtures. The RCCs prepared at the adequate cement content of 275 kg/m3, exhibited suitable performance for all mixtures containing up to 20% vol CR content. Results showed that the standard relationships between compressive strength, static and elastic moduli as established for normal concretes, are also applicable to RCCs.

The loaded rock experiences multiple stages of deformation. It starts with the formation of microcracks at low stresses (crack initiation, CI) and then transitions into unstable crack propagation (crack damage, CD) near the ultimate strength. In this study, both the acoustic emission method (AEM) and the ultrasonic testing method (UTM) were used to examine the characteristics of AE parameters (b-value, peak frequency, frequency-band energy ratio, and fractal dimension) and ultrasonic (ULT) properties (velocity, amplitude, energy attenuation, and scattering attenuation) of bedded shale at CI, CD, and ultimate strength. The comparison involved analyzing the strain-based method (SBM), AEM, and UTM to determine the thresholds for damage stress. A fuzzy comprehensive evaluation model (FCEM) was created to describe the damage thresholds and hazard assessment. The results indicate that the optimal AE and ULT parameters for identifying CI and CD stress are ringing count, ultrasonic amplitude, energy attenuation, and scattering attenuation of the S-wave. Besides, damage thresholds were detected earlier by AE monitoring, ranging from 3 MPa to 10 MPa. CI and CD identified by UTM occurred later than SBM and AEM, and were in the range of 12 MPa. The b-value, peak frequency, energy ratio in the low-frequency band (0-62.5 kHz), correlation dimension, and sandbox dimension showed low values at the peak stress, while the energy ratio in a moderate-frequency band (187.5-281.25 kHz) and amplitude showed high values. The successful application of FCEM to laboratory testing of shales has demonstrated its ability to quantitatively identify AE/ULT precursors of seismic hazards associated with rock failure. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published 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/).

Stabilizing problematic soils with new materials can reduce environmental problems and improve mechanical properties. This research uses the results of various tests, such as unconfined compressive strength (UCS), indirect tensile strength (ITS), ultrasonic pulse velocity (UPV), direct shear test, and standard Proctor compaction, to evaluate the effect of curing time and the nano aluminum oxide contents on the mechanical and shear characteristics of clay soil stabilized with cement and nano aluminum oxide. This research showed that the optimal content of replacing cement with nano aluminum oxide to stabilize clay soil is 0.9% by weight of cement. Adding the optimal content of nano aluminum oxide to cement-stabilized clay soil increased UCS and ITS by 28% and 51%, respectively. Also, the drained internal friction angle and cohesion increased by 17 and 25%, respectively. The results of UPV non-destructive testing can also be used to predict the mechanical characteristics of stabilized clay. By reducing cement consumption and enhancing soil stabilization, this research contributes to Sustainable Development Goals (SDGs) by promoting resource efficiency, lowering environmental impact, and supporting durable infrastructure development.

Conventional triaxial apparatus has limited capabilities for advanced testing of frozen soils, such as loading under controlled temperature and volume change measurements. To bridge this gap, in this paper, we presented a novel ultrasound-integrated double-wall triaxial cell designed specifically for stress and strain-controlled, as well as temperature-controlled testing of frozen soils. Monitoring pore ice content during triaxial tests in frozen soils poses a significant challenge. To overcome this hurdle, we developed an in-cell ultrasonic P wave measurement setup, which was integrated into the triaxial device to monitor freeze advancement at any stage of the test. We proposed a three-phase poromechanics-based approach to estimate the pore ice content of frozen soil samples based on the P-wave velocity. A series of creep tests under different freezing temperatures have been undertaken for frozen soil samples to investigate the effect of ice content and temperature on the volumetric deformations of frozen soils during creep tests. Our study demonstrates the potential of the proposed ultrasound-integrated double-wall triaxial apparatus for creep tests of frozen soils.

The increasing demand for sustainable civil engineering solutions requires balancing present-day infrastructure needs with environmental preservation for future generations. This study explores the potential of xanthan gum, an eco-friendly biopolymer, for stabilizing clayey sand as an alternative to traditional soil stabilizers. Various concentrations of xanthan gum (0.25 % to 1.5 %) and curing durations (7, 14, and 28 days) were evaluated using standard geotechnical testing methods, including compaction, unconfined compressive strength (UCS), indirect tensile strength (ITS), ultrasonic pulse velocity (UPV), and scanning electron microscopy (SEM) analysis. The soil samples comprised 80 % poorly graded sand and 20 % high-plasticity clay. Results showed a significant improvement in soil properties, with just 0.25 % xanthan gum after a 7-day curing period leading to notable increases in UCS and tensile strength. However, further increases in xanthan gum concentration yielded diminishing returns in strength enhancement. Extending the curing time from 7 to 28 days improved compressive strength and stiffness. Additionally, xanthan gum-enhanced samples exhibited increased energy absorption, stiffness, and brittle behavior, forming a denser soil matrix and improving the particle bonding, supported by UPV results and SEM imagery. Also, the relationship between the stiffness from UCS tests and the ultrasonic pulse velocity was obtained. The findings underscore xanthan gum's potential as a sustainable and effective soil stabilizer for geotechnical applications.

Microbially Induced Calcite Precipitation (MICP) is an eco-friendly method for improving sandy soils, relying on micro-organisms that require nitrogen and essential nutrients to induce carbonate mineral precipitation. Given the substantial annual generation of chicken manure (CM) and the associated challenges in its disposal resulting in environmental pollution, the nutrient-rich composted form of this waste material is proposed in this study as a supplementary additive (along with more costly industrial reagents, e.g., urea) to provide the necessary carbon and nitrogen for the MICP process. To this end, different CM contents (5 %, 10 %, and 15 %) along with various concentrations of cementation solution (1 M, 1.5 M, and 2 M) are employed in multiple improvement cycles to augment the efficiency of the MICP technique. Unconfined Compressive Strength (UCS), Ultrasonic Pulse Velocity (UPV), and Water Absorption (WA) tests are performed to assess the mechanical properties of the samples before and after exposure to freeze-thaw (F-T) cycles, while SEM, XRD, and FTIR analyses are carried out to delineate the formation of calcite within the porous structure of MICP-CM-treated sands. The findings suggest that an optimum percentage of CM (10 %) in the MICP process not only contributes to environmental conservation but also significantly enhances all the mechanical properties of bio-cemented sandy soils due to markedly improved bonding within their porous fabric. The results also show that although prolonged exposure to consecutive F-T cycles causes a reduction in strength and stiffness of enhanced MICP-treated soils, the mechanical properties of such geo-composites still remain within an acceptable range for optimal CM-enhanced biocemented mixtures, significantly superior to those of MICP-treated sands.

Silty sandy soils usually have low shear strength due to their non-cohesive structure, weak internal bonds, and high porosity. Environmental challenges, such as freeze-thaw (F-T) cycles, also reduce the mechanical characteristics and instability of infrastructures and structures built on these soils. Biopolymers and fibers offer a sustainable solution to improve soil strength and F-T strength. However, while much research focuses on stabilizing silty sand, fewer studies examine the combined effects of biopolymers and fibers on soil properties under F-T cycles. Additionally, the correlation between ultrasonic pulse velocity (UPV) and unconfined compressive strength (UCS) in biopolymer-stabilized and fiber-reinforced soils still needs to be explored. This study examines the stabilization of silty sand using Persian gum (PG) (0.5-3%) and kenaf fibers (KF) (0-1.5%) with lengths of 6, 12, and 18 mm at the curing times of 7, 28, and 90 days. The samples were subjected to F-T cycles (0, 1, 2, 3, 6, and 12). The results showed that the highest UCS was achieved with 2.5% PG and 1% KF (12 mm) after 28 days. After 12 F-T cycles, the UCS reductions were 41% for sample with 2.5% PG and 34% for sample 2.5% PG and 1%KF. The swelling after freezing for the 2.5% PG and 1% KF sample and the 2.5% PG sample was 4.8% and 3.45%, respectively. A correlation between UPV and UCS after various F-T cycles was suggested. The scanning electron microscopy (SEM) analysis revealed increased voids, weakened polymer bonds, and cracks after 12 F-T cycles.

Coal waste (CW) could be used for soil stabilization due to the pozzolanic elements it contains. There hasn't been much investigation into how different fibers affect the mechanical qualities of stabilized sand, although adding fibers of any kind to soils may improve the soil because of fiber characteristics like rigidity. For this reason, several tests were carried out on sand that contained 6% cement (by dry weight of used sand), 5 wt% CW, 0, 0.25 wt%, and 0.50 wt% fiber, as well as the unconfined compressive strength (UCS) test, indirect tensile strength (ITS) test, unconsolidated undrained triaxial test (UU), scanning electron microscope (SEM) test and ultrasonic pulse velocity (UPV) test. The results showed that in comparison to other fiber reinforced mix designs, the specimen reinforced with 0.5% fibers and the mix design of 0.25 wt% glass and 0.25 wt% polypropylene (PP) fibers exhibited the maximum strength. Examining the impact of fiber type found that glass fibers influence PP strength more favorably than other fiber types. The use of PP fibers is an excellent solution for the problem of large strains in design processes, while adding glass fibers is considered a suitable treatment for issues related to small strains.

This study is focused on optimizing electromagnetic acoustic transducer (EMAT) sensors for enhanced ultrasonic guided wave signal generation in steel cables using CAD and modern manufacturing to enable contactless ultrasonic signal transmission and reception. A lab test rig with advanced measurement and data processing was set up to test the sensors' ability to detect cable damage, like wire breaks and abrasion, while also examining the effect of potential disruptors such as rope soiling. Machine learning algorithms were applied to improve the damage detection accuracy, leading to significant advancements in magnetostrictive measurement methods and providing a new standard for future development in this area. The use of the Vision Transformer Masked Autoencoder Architecture (ViTMAE) and generative pre-training has shown that reliable damage detection is possible despite the considerable signal fluctuations caused by rope movement.