Soybean urease-induced calcium carbonate precipitation (SICP) is an innovative and eco-friendly approach with demonstrated potential for mitigating soil liquefaction. However, the specific impacts of the concentrations of soybean urease and salt solutions require further elucidation. The research examines how the two compositions influence calcium carbonate formation. Dynamic characteristics of one-cycle SICP-treated clean and silty sand were analyzed based on cyclic triaxial tests. It was revealed that SICP-treated specimens of both liquefied sand and silty sand exhibit reduced accumulation of excess pore pressure and diminished strain growth under cyclic loading, thereby delaying liquefaction failure. Although higher concentrations of both soybean urease and salt solution can enhance liquefaction resistance, salt solution concentration has a more pronounced effect on improving liquefaction resistance due to the more production of calcium carbonate. Scanning electron microscopy observations confirmed the presence of calcium carbonate crystals at the interfaces between sand particles and between sand and fine particles. These crystals effectively bond the loose sand and fine particles into a cohesive matrix, reinforcing soil structure. A direct linear correlation was established between the liquefaction resistance improvement and precipitated calcium carbonate content. Notably, the one-cycle SICP treatment method adopted in this study demonstrates a better biocementation effect compared to cement mortar or multi-cycle MICP-treated sand under the same content of cementitious materials. These findings provide valuable insights for optimizing SICP treatments, aiming to reduce the risk of soil liquefaction in potential field applications.

Stinging nettle (Urtica dioica L.) has been observed to grow spontaneously on metal-contaminated soils marginalised by heavy industrial use, thereby presenting an opportunity for the economic utilisation of such lands. This study explores the potential of nettle as a fibre crop by producing short fibre-reinforced polylactic acid (PLA) composites through compounding and injection moulding. Whole stem segments from three nettle clones (B13, L18, and Roville), along with separated fibre bundles from the L18 clone, were processed. The fibre bundles were separated using a roller breaker unit and a hammer mill. From separation with the hammer mill, not only cleaned fibre bundles but also the uncleaned fibre-shive mixture and the undersieve fraction were processed. The Young's modulus of all composites exceeded that of unreinforced PLA, with mean values ranging from 5.7 to 8.1 GPa. However, the tensile strength of most composites was lower than that of pure PLA, except for the two composites reinforced with cleaned fibre bundles. Of these two, the reinforcement with fibre bundles from separation with the hammer mill led to superior mechanical properties, with a higher Young's modulus (8.1 GPa) and tensile strength (61.8 MPa) compared to those separated using the breaking unit (7.2 GPa and 55.9 MPa). This enhancement is hypothesised to result from reduced fibre damage and lower fibre bundle thickness. The findings suggest that nettle cultivation on marginal lands could be a viable option for producing short-fibre composites, thereby offering a sustainable use of these otherwise underutilised areas.

Employing soil improvement techniques to mitigate and prevent the detrimental effects of liquefaction on foundations often leads to a significant increase in construction costs in engineering projects. Developing simple, cost-effective, and eco-friendly liquefaction mitigation methods has always been one of the main concerns of geotechnical engineers. Researchers introduced the induced partial saturation (IPS) method to increase the liquefaction resistance of the saturated foundations, which is based on decreasing the saturation degree of the saturated sand. In this study, hollow cylinder torsional shear tests were conducted on loose saturated and desaturated calcareous sand to assess the liquefaction behavior of desaturated sand. Soil compressibility is the primary parameter affecting the liquefaction behavior of desaturated sand. As saturation degree, back pressure, and effective confining pressure significantly influence soil compressibility, their effects on the liquefaction resistance of desaturated sand were investigated. The pore pressure development during cyclic loading reveal that, unlike saturated samples, desaturated samples do not exhibit an excess pore pressure ratio reaching one, even when the double amplitude shear strain surpasses 7.5 %. Finally, the test results demonstrated a notable correlation between liquefaction resistance ratio, maximum volumetric strain, and the maximum generated excess pore pressure ratio, and a pore pressure model was proposed.

Fluid injection is widely used to enhance permeability in rock formations by creating or dilating transport pathways for resources such as oil, gas, heat, or CO2. The dynamic propagation of damage induced by fluid injection is governed by fluid flow, dynamic poroelastic deformation, mixed tensile and shear failure, and damage-induced antipermeability degradation. However, the transition from elastoplastic deformation to mixed-mode failure, as well as the induced dynamics, remains ambiguous. This study combines the dynamic Biot's poroelasticity and coupled Drucker-Prager plasticity, Grady-Kipp damage, and antipermeability degradation to simulate dynamic hydraulic fracturing. An explicit predictor-corrector scheme was employed to solve the dynamics of saturated porous media and identify the key factors controlling dynamic damage propagation. The proposed model was tested on soil column consolidation and rock hydraulic fracturing driven by a pre-existing crack, demonstrating good agreement between the numerical and experimental results. Simulation results indicate that damage zones facilitate preferential flow during fluid injection due to damage-induced degradation. The most extensive damage zone is observed under strong damage-permeability coupling. Shear plasticity, tensile damage, and induced seismicity are dominated by fracturing dynamics induced by fluid injection. Oscillations in the temporal-spatial evolution of damaged and plastic points, cumulated potency, and moment magnitude confirm the fracturing dynamics. Shorter injection times result in stronger dynamics and more significant damage propagation. The period of oscillations in cumulated potency increases with injection time while their amplitude gradually decreases due to energy release. These findings highlight injection-induced fracturing dynamics, offering novel insights into the dynamic propagation of damage coupled with matrix antipermeability degradation.

This study aims to understand the effect of injection rate on injection-induced fracture activation in granite. We performed water injection-induced slip tests on samples containing either a smooth or a rough fracture at four different injection rates under undrained conditions and monitored the acoustic emission (AE) signals during the tests. Experimental results reveal that the critical activation fluid pressure is related to the injection rate, pressure diffusion rate, stress state, and fracture roughness. For the smooth fracture, as the injection rate increases, the critical activation fluid pressure increases significantly, while the injection rate has little effect on the critical activation fluid pressure of the rough fracture. The quasi-static slip distance of fractures decreases as the injection rate increases, with rough fractures exhibiting a greater overall slip distance compared to smooth fractures. The number of AE events per unit sliding distance increases with the injection rate, while the global b value decreases. These results indicate that higher injection rates produce more large-magnitude AE events and more severe slip instability and asperity damage. We established a linkage between fluid injection volume, injection rate, and AE events using the seismogenic index (S). The smooth fracture exhibits a steadily increasing S with the elapse of injection time, and the rate of increase is higher at higher injection rates; while the rough fracture is featured by a fluctuating S, signifying the intermittent occurrence of largemagnitude AE events associated with the damage of larger fracture asperities. Our results highlight the importance of fracture surface heterogeneity on injection-induced fracture activation and slip. (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/).

In this study, a high-confining pressure and real-time large-displacement shearing-flow setup was developed. The test setup can be used to analyze the injection pressure conditions that increase the hydro-shearing permeability and injection-induced seismicity during hot dry rock geothermal extraction. For optimizing injection strategies and improving engineering safety, real-time permeability, deformation, and energy release characteristics of fractured granite samples driven by injected water pressure under different critical sliding conditions were evaluated. The results indicated that: (1) A low injection water pressure induced intermittent small-deformation stick-slip behavior in fractures, and a high injection pressure primarily caused continuous high-speed large-deformation sliding in fractures. The optimal injection water pressure range was defined for enhancing hydraulic shear permeability and preventing large injection-induced earthquakes. (2) Under the same experimental conditions, fracture sliding was deemed as the major factor that enhanced the hydraulic shear-permeability enhancement and the maximum permeability increased by 36.54 and 41.59 times, respectively, in above two slip modes. (3) Based on the real-time transient evolution of water pressure during fracture sliding, the variation coefficients of slip rate, permeability, and water pressure were fitted, and the results were different from those measured under quasi-static conditions. (4) The maximum and minimum shear strength criteria for injection-induced fracture sliding were also determined (m = 0.6665 and m = 0.1645, respectively, m is friction coefficient). Using the 3D (three-dimensional) fracture surface scanning technology, the weakening effect of injection pressure on fracture surface damage characteristics was determined, which provided evidence for the geological markers of fault sliding mode and sliding nature transitions under the fluid influence. (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/).

In this work, environmentally friendly materials based on zein, glycerol, and xanthan gum (XG) are developed through the innovative use of extrusion and injection-molding methodologies for this type of bioplastic materials. This methodology has never been applied to thermoplastic zein materials and this approach represents a significant advancement over traditional cast film methods, enabling enhanced control over properties and expanding potential applications thanks to the possibility of producing new geometries. Mechanical properties show that XG increases the stiffness and hardness of the materials, achieving elastic modulus of 1294 MPa and tensile strengths of 21 MPa. The thermal stability of the formulations is also enhanced by the addition of XG, which considerably increases the maximum degradation rate temperature from 259 up to 340 degrees C. The wettability of the materials is assessed by contact angle measurements, which show a very high hydrophilicity (29 degrees), nonetheless, it was decreased to not so extremely low contact angle values thanks to the addition of XG (50 degrees), which is very positive from the point of view of food packaging applications. Finally, all materials proved to be completely disintegrated under controlled compost conditions after 9 weeks of incubation in controlled compost soil conditions, verifying the great environmentally friendly value of these formulations.

This study elucidates the findings of a computational investigation into the stimulation characteristics of natural reservoir systems enhanced by high-voltage electropulse-assisted fluid injection. The presented methodology delineates the comprehensive rock-fracturing process induced by electropulse and subsequent fluid injection, encompassing the discharge circuit, plasma channel formation, shockwave propagation, and hydro-mechanical response. A hydromechanical model incorporating an anisotropic plastic damage constitutive law, discrete fracture networks, and heterogeneous distribution is developed to represent the natural reservoir system. The results demonstrate that high-voltage electropulse effectively generates intricate fracture networks, significantly enhances the hydraulic properties of reservoir systems, and mitigates the adverse impact of ground stress on fracturing. The stimulationenhancing effect of electropulse is observed to intensify with increasing discharge voltage, with enhancements of 118.0%, 139.5%, and 169.0% corresponding to discharge voltages of 20 kV, 40 kV, and 60 kV, respectively. Additionally, a high-voltage electropulse with an initial voltage of U0 1/4 80 kV and capacitance C 1/4 5 mF has been shown to augment the efficiency of injection activation to approximately 201.1% compared to scenarios without electropulse. Under the influence of high-voltage electropulse, the fluid pressure distribution diverges from the conventional single direction of maximum stress, extending over larger areas. These innovative methods and findings hold potential implications for optimizing reservoir stimulation in geo-energy engineering. (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/).

Polylactic acid (PLA) and tapioca starch biocomposites offer a sustainable alternative to petroleum-based plastics for single-use packaging. This study focused on optimizing injection molding parameters for a novel PLA/tapioca starch blend using response surface methodology (RSM). Injection temperature had the most significant impact on tensile strength. The optimal parameters identified were injection temperature of 181 degrees C, pressure of 40 MPa, and speed of 300 mm/s, achieving a tensile strength of 25.34 MPa without defects. Morphological analysis revealed smoother fracture surfaces and presence of microfibrils denoting increased ductility. Mechanical properties, including 16 % elongation, 24.5 MPa flexural strength, and 9.32 kJ/m2 impact strength, were comparable to conventional plastics. Enhanced biodegradation in ambient soil conditions was observed, while migration tests showed no leaching in most stimulants, supporting its potential for sustainable packaging applications.

Giant reed (Arundo donax L.) is a plant species with a high growth rate and low requirements, which makes it particularly interesting for the production of different bioproducts, including natural fibers. This work assesses the use of fibers obtained from reed culms as reinforcement for a high-density polyethylene (HDPE) matrix. Two different lignocellulosic materials were used: i) shredded culms and ii) fibers obtained by culms processing, which have not been reported yet in literature as fillers for thermoplastic materials. A good stress transfer for the fibrous composites was observed, with significant increases in mechanical properties; composites with 20% fiber provided a tensile elastic modulus of almost 1900 MPa (78% increase versus neat HDPE) and a flexural one of 1500 MPa (100% increase), with an improvement of 15% in impact strength. On the other hand, composites with 20% shredded biomass increased by 50% the tensile elastic modulus (reaching 1560 MPa) and the flexural one (up to 1500 MPa), without significant changes in impact strength. The type of filler is more than its ratio; composites containing fibers resulted in a higher performance than the ones with shredded materials due to the higher aspect ratio of fibers.