Hao Zhang

To overcome the limitations of conventional high-viscosity high-elasticity modified asphalt, including high production costs, phase separation, and thermal degradation, this study introduces a novel fast melting Styrene-Butadiene-Styrene modifier (SBS-T) for asphalt modification. The primary novelty of SBS-T lies in its ability to mitigate phase separation and thermal degradation while simplifying the production process, thereby offering a more robust and cost-effective alternative. The viscoelastic properties of SBS-T-modified asphalt were characterized through frequency sweep tests under varying loading conditions, while its fatigue behavior was quantitatively assessed using the Simplified Viscoelastic Continuum Damage (S-VECD) model. The results indicate that the SBS-T-modified asphalt exhibits outstanding viscoelastic performance across a broad range of temperatures and loading frequencies, and can better adapt to the temperature and load changes in complex pavement environments. Among them, the influence of long-term aging on the linear viscoelastic characteristics of SBS-T-modified asphalt is greater than that of ultraviolet aging. The SBS-T-modified asphalt also shows better stiffness and resistance to shear deformation. The fatigue life of asphalt gradually decreases with the deepening of the aging degree, among which the impact of long-term aging on fatigue life is greater than that of ultraviolet aging. Under different aging conditions, SBS-T-modified asphalt has shown good fatigue performance and is suitable for practical engineering applications.

Aiming at the problems of complex process flow, high energy consumption, and difficult emulsification in the preparation of traditional SBS-modified emulsified asphalt, a preparation method of fast-melting SBS (referred to as SBS-T) modified emulsified asphalt based on the integration of modification and emulsification is proposed. Based on surface free energy theory, the contact angles between three rapid-melting SBS-modified emulsified asphalts with different dosages and three probe liquids (deionized water, glycerol, and formamide) were measured using the sessile drop method. The adhesion performance of the asphalt–aggregate system was studied by means of micromechanical methods. The evaluation indicators such as the cohesion work of the emulsified asphalt, the adhesion work of asphalt–aggregate, the spalling work, and the energy ratio were analyzed. The results show that the SBS-T modifier can significantly improve the thermodynamic properties of emulsified asphalt. With increasing modifier content, the SBS-T-modified emulsified asphalt demonstrated enhanced cohesive work, improved asphalt–aggregate adhesive work, and increased energy ratio, while showing reduced stripping work. At equivalent dosage levels, the SBS-T-modified emulsified asphalt demonstrates a slight improvement in adhesion performance to aggregates compared to conventional SBS-modified emulsified asphalt. The SBS-T emulsified modified asphalt provides an effective technical solution for the preventive maintenance of asphalt pavements.

Evaluating the burst pressure of corrosion cluster defects necessitates considering the interaction of contiguous defects. The importance of this interaction cannot be emphasized enough, as it plays a crucial role in determining the failure pressure of such pipelines. Current methods for assessing the failure pressure of corrosion cluster defects have drawbacks, including complex evaluation procedures and limited applicability. In this research, the failure mode and location of corrosion clusters with two or more defects are studied with a burst experiment on a full-scaled pipeline. Based on the failure position of the corrosion cluster, a “center failure location” method is proposed to estimate the burst pressure of colony corrosion defects. The method takes the defect in the failure position as the center; the influence of contiguous defects that interact with the central defect on its failure pressure is considered, and subsequently, the burst pressure of colony corrosion centered on the failure location is evaluated. In contrast with the current assessment methods, while the proposed approach does not reduce prediction errors, it requires fewer evaluation conditions and is operationally simpler and more versatile.

The newly developed two-component polymer (TFPU) cut-off walls have great application potential in civil engineering for water-seepage prevention. Investigating the mechanical interactions between TFPU and soil from the theoretical perspective can provide a basis for furtherly evaluating the stability of TFPU cut-off walls, which, however, has not been conducted. In this study, based on the shear testing results, the shear damage model of the TFPU-bentonite contact surface was established. Studies show that the TFPU-bentonite contact surface performs strain-softening behavior under shear and that the strain-softening behavior becomes less and less obvious when the normal stress increases. The theoretical shear stress-strain curves are in good consistent with the experimental ones, and the maximum differences between the theoretical shear stress and shear strain at yield and the experimental ones are about 3.88% and 3.40%, respectively, indicating that the shear damage model can reflect the mechanical properties of the TFPU-bentonite contact surface. The critical damage of the contact surface increases from 0.05 to 0.50 in the power function way when normal stress increases from 75 to 1200 kPa, implying that the shear failure of the contact surfaces changes from brittleness to ductility. This study provides a theoretical base for evaluating the influences of the TFPU-soil contact surface on the stability of the TFPU cut-off wall structures.

To describe the mechanical properties of the system of pipe pile‐soil reasonably and accurately, the constitutive relations of the soil around pile and pile core soil are characterized by the fractional derivative viscoelastic model. We assume that the radial and circumferential displacements of the soil around the pile and pile core soil are the functions of r, θ, and z. The horizontal dynamic control equations of soil layers are derived by using the fractional derivative viscoelastic model. Considering the fractional derivative properties, soil layer boundary condition, and contact condition of pile and soil, the potential function decomposition method is used to solve the radial and circumferential displacements of the soil layer. Then, the force of unit thickness soil layer on the pipe pile and the impedance factor of the soil layer are obtained. The horizontal dynamic equations of pipe pile are established considering the effect of soil layers. The horizontal dynamic impedance and horizontal‐swaying dynamic resistance at the pile top are obtained by combining the pipe pile‐soil boundary conditions and the orthogonal operation of trigonometric function. Numerical solutions are used to analyze the influence of pile and soil parameters on the soil impedance factor and horizontal dynamic impedance at pile top. The results show that the horizontal impedance factors of the soil layer and horizontal dynamic impedance of pipe pile by using the fractional derivative viscoelastic model can be degraded to those of the classical viscoelastic model and the elastic model. For the fractional derivative viscoelastic model of soil layer, the influence of soil around pile on the dynamic impedance is greater than that of pile core soil. The model parameter T_Oa, the inner radius of pipe pile, and the pile length have obvious effects on the horizontal impedance of the soil layer and pipe pile, while the influence of the pile core soil on the pile impedance is smaller.

To investigate the dynamic splitting tensile mechanical property of limestone under coupled static and dynamic state, the dynamic split tensile tests of limestone under one‐dimensional coupled static and dynamic load with different strain rates were performed with the help of modified split Hopkinson pressure bar (SHPB) equipment. The dynamic splitting tensile mechanical property and energy dissipation characteristic under two stress states were also compared in this research. Test results indicated that the dynamic tensile strength of the limestone specimen increased with the increase of average strain rate, exhibiting an obvious strain rate effect. In addition, dynamic tensile strength under uniaxial state was higher than that under one‐dimensional coupled static and dynamic load state under the same test condition. Moreover, the deformation modulus increased with increasing average strain rate under uniaxial state, while it decreased with increasing average strain rate under coupled static and dynamic state. Both the reflected energy and absorbed energy linearly increased with increasing incident energy. The preload in the radial direction could increase the reflected energy and decrease the absorbed energy. Moreover, the transmitted energy with preload state was slightly lower than that under uniaxial state. Finally, the dynamic tensile strength of limestone specimen increased as a power function with increasing absorbed energy.