Fiber reinforcement has been demonstrated to mitigate soil liquefaction, making it a promising approach for enhancing the seismic resilience of tunnels in liquefiable strata. This study investigates the seismic response of a tunnel embedded in a liquefiable foundation locally improved with carbon fibers (CFs). Consolidated undrained (CU), consolidated drained (CD), and undrained cyclic triaxial (UCT) tests were conducted to determine the optimal CFs parameters, identifying a fiber length of 10 mm and a volume content of 1 % as the most effective. A series of shake table tests were performed to evaluate the effects of CFs reinforcement on excess pore water pressure (EPWP), acceleration, displacement, and deformation characteristics of both the tunnel and surrounding soil. The results indicate that CFs reinforcement significantly alters soil-tunnel interaction dynamics. It effectively mitigates liquefaction by enhancing soil stability and slowing EPWP accumulation. Ground heave is reduced by 10 %, while tunnel uplift deformation decreases by 61 %, demonstrating the stabilizing effect of CFs on soil deformation. The fibers network interconnects soil particles, improving overall structural integrity. However, the increased shear strength and stiffness due to CFs reinforcement amplify acceleration responses and intensify soil-structure interaction, leading to more pronounced tunnel deformation compared to the unimproved case. Nevertheless, the maximum tunnel deformation remains within 3 mm (0.5 % of the tunnel diameter), posing no significant structural risk from the perspective of the experimental model. These findings provide valuable insights into the application of fibers reinforcement for improving tunnel stability in liquefiable foundations.

Permeable reactive barrier (PRB) integrated with electrokinetic geosynthetic (EKG) is an enhancement technique to improve the efficiency of in-situe heavy metal contaminated soil remediation. In this study, EKG-PRB was considered under cyclic loading conditions to remediate copper contaminated soil. Also, the basis of remediation is the implementation of electrokinetic geosynthetic (EKG) materials as electrodes and fabricated composite nanofibers as a permeable reactive barrier. Therefore, nanofibers electrospun with graphene nanoparticle inclusion were designed and constructed. To assess the performance of EKG-PRNB technique on remediation of a copper contaminated soil, an experimental apparatus was designed, and various tests were categorized into EKG and EKG-PRNB groups. All tests were carried out under the similar conditions, cyclic loading (7-113 kPa), drainage condition (open cathode-closed anode), duration (60 h), and a voltage gradient of 1 V cm- 1 with a tolerance of +/- 0.1. The EKG was carried out without utilizing the PRB, while EKG-PRNB experiments were conducted using a permeable reactive nanofiber barrier in different positions, adjacent to cathode (PRNB0) and at a distance of 4 cm from the cathode (PRNB1). According to the results, PRNB were fabricated with a specific surface area of 19.423 m2 g- 1 and a maximum adsorption capacity of 81.43 mg g-1. Copper removal efficiency in drainage water reached 97.4 %, with copper immobilization efficiency approximately 14 %. Results demonstrated that the positioning of the reactive barrier had no statistically significant impact on the electrokinetic remediation system performance, removal efficiency, settlement, and consolidation degree.

Microbial-induced calcite precipitation (MICP) is an environmentally friendly treatment method for soil improvement. When combined with carbon fiber (CF), MICP can enhance the liquefaction resistance of sand. In this study, the effects of CF content (relative to the sand weight of 0%, 0.2%, 0.3%, and 0.4%) on the liquefaction resistance of MICP-treated silica and calcareous sand were investigated. The analysis was conducted using bacterial retention test, cyclic triaxial (CTX) test, LCD optical microscope, and scanning electron microscopy (SEM). The results showed that with the increase in CF content, the bacterial retention rate increased. Additionally, the cumulative cycles of axial strain to 5%, excess pore water pressure to initial liquefaction, as well as strength and stiffness, all increased with higher CF content. This trend continued up to the CF content of 0.2% for silica sand and 0.3% for calcareous sand, beyond which the cumulative cycles began to decrease. The great mechanical system of CF, calcite, and sand particles was significantly strengthened after MICP-treated. However, the reinforced calcite did not completely cover the CF, and excess CF hindered the connection between sand grains. The optimal amount of CF in silica and calcareous sands were 0.2% and 0.3%. This study provides valuable guidance for selecting the optimal CF content in the future MICP soil engineering.

Annual freeze-thaw (F-T) cycles can cause significant damage to soil structures, particularly roads. This study explored the effectiveness of adding carbon fibers (CF) to clay to enhance its performance during F-T cycles. The CF were mixed with clay at varying rates, ranging from 0.1 to 0.4%, based on the weight of the dry soil. Dynamic tests were conducted on unreinforced and reinforced samples after subjecting them to 0, 3, 6, and 9 F-T cycles under 100 kPa and 300 kPa confining pressure. The findings revealed that the inclusion of CF led to an increase in both the shear modulus and damping ratio. Specifically, the sample containing 0.3% CF demonstrated a significant 30% increase in shear modulus compared to the pure sample at the same cyclic stress level. Moreover, while the shear modulus decreased with the number of F-T cycles, this reduction was less pronounced in samples reinforced with CF compared to pure samples.

Fiber-reinforced polymer (FRP) wrapping is a potential technique for coal pillar reinforcement. In this study, an acoustic emission (AE) technique was employed to monitor coal specimens with carbon FRP (CFRP) jackets during uniaxial compression, which addressed the inability to observe the cracks inside the FRP-reinforced coal pillars by conventional field inspection techniques. The spatiotemporal fractal evolution of the cumulated AE events during loading was investigated based on fractal theory. The results indicated that the AE response and fractal features of the coal specimens were closely related to their damage evolution, with CFRP exerting a significant influence. In particular, during the unstable crack development stage, the evolutionary patterns of the AE count and energy curves of the CFRPconfined specimens underwent a transformation from the slight shock-major shock type to the slight shock-sub-major shock-slight shock-major shock type, in contrast to the unconfined coal specimens. The AE b-values decreased to a minimum and then increased marginally. The AE spatial fractal dimension increased rapidly, whereas the AE temporal fractal dimension fluctuated significantly during the accumulation and release of strain energy. Ultimately, based on the AE count and AE energy evolution, a damage factor was proposed for the coal samples with CFRP jackets. Furthermore, a damage constitutive model was established, considering the CFRP jacket and the compaction characteristics of the coal. This model provides an effective description of the stress-strain relationship of coal specimens with CFRP jackets. (c) 2024 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/).

To achieve the repeatability of aerospace thermal components, C/TaC-SiC composites were fabricated. Cycle ablation and bending tests were carried out. After 3 x 60 s of ablation beyond 2100 degrees C, the mechanical property retention rate was 80.9%. Interestingly, a reaction similar to ouroboros ring, in which the cyclic reactions of TaC being oxidized to Ta2O5 and Ta2O5 being reduced to TaC, occurred in the central ablation region of C/TaC-SiC composites. On the one hand, the continuous generation of TaC could prevent liquid state Ta2O5 from being blown off central ablation region, playing a similar role in water and soil conservation. On the other hand, liquid Ta2O5 covered the surface of C/TaC-SiC composites during ablation process, contributing to block the inward permeation of oxidized gases. In addition, novel Grotto structures were detected in the transitional ablation region of C/TaC-SiC composites. The formation reason of the Grotto structure has also been discussed.

In this paper, flexible conductive composite materials were prepared from flexible graphite and carbon fiber by mould pressing, and their micromorphology was studied by SEM. The influence of carbon fiber content on the mechanical properties and electrical conductivity of the flexible conductive composite material was studied, and the corrosion rate of the flexible conductive composite material coupling with galvanized steel in soil with different SO42- concentrations was studied. The results showed that the tensile strength reached 5.82 MPa when the mass ratio of carbon fiber to flexible graphite was 1:20, and the volume resistivity achieved 4.76 x 10-5 Omegam when the mass ratio of carbon fiber to flexible graphite was 1:30. With the increase in molding pressure, tensile strength and electrical conductivity had a slight increase. When the flexible conductive composite material was coupled with galvanized steel, sulfate could accelerate the galvanic cell corrosion between the flexible graphite grounding material and galvanized steel. The increase in the sulfate concentration led to more corrosion acceleration. With the increase in corrosion time, the corrosion potential of the flexible graphite grounding material and galvanized steel coupling body decreased to its lowest at 30 days, and then increased gradually. The corrosion current was the highest at 30 days, and then decreased gradually.

Studies show that adding carbon fiber to concrete to form a conductive network can make concrete feel its own stress, strain, cracks, and damage according to the change of conductive network, and improve the strength and durability of concrete. In view of the self-sensing characteristics of carbon fiber, carbon fiber reinforced cement-based composites are put forward as a new intelligent sensing material. Through unconfined compressive strength test, resistivity test, microscopic test, and model test, the influence of fiber volume fraction and fiber length on unconfined compressive strength and resistivity change rate of carbon fiber reinforced cement-based composites are studied. A carbon fiber reinforced cement-based composites sensor is made according to the optimal ratio, which is implanted into cement-based composites components to establish the functional relationship between the sensor resistivity change rate and the stress of cement-based composites components, so as to realize the stress monitoring of cement-based composites components by the sensor. The results show that, in the study of the strength of carbon fiber reinforced cement-based composites, the unconfined compressive strength of carbon fiber reinforced cement-based composites is affected by both carbon fiber volume fraction and carbon fiber length, and the compressive strength increases first and then decreases with the increase of both. In the test range, 2% is the optimal volume fraction and 6 mm is the optimal fiber length. In the study of the resistivity change rate of carbon fiber reinforced cement-based composites, when the carbon fiber volume fraction is 1% and the fiber length is 3 mm, the resistivity change rate of the specimen is the largest, and the self-sensing sensitivity of carbon fiber reinforced cement-based composites is the best. There is an obvious exponential relationship between the resistivity change rate of the sensor embedded in the component and the stress of the cement-based composites component. Through establishing a stress prediction formula based on resistivity change rate, the stress state monitoring of the cement-based composites structure can be realized.