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A curved discontinuity near the ground can cause the scattering of seismic waves and significantly affect the ground and underground motions, posing some challenges in seismic design. In this paper, a series solution for the scattering and diffraction of plane SH waves from a semi-circular discontinuity in an elastic half-plane is first presented using the wave function expansion method, aiming to reveal the effects of the discontinuity properties on wave scattering and seismic motion. Based on the correspondence principle of viscoelasticity, the influence of the damping ratio of the medium on the seismic motion is also discussed. Finally, by combining the series solution and the inverse Fourier transform, the ground and underground motions induced by a transient plane SH wave are analyzed by exhibiting the wave field snapshots at different times and the waveform curves of different measurement points on the ground. The results indicate that both the stiffness of the discontinuity and the damping ratio of the medium have a great influence on the propagation of seismic waves and play an important role in seismic calculations. • Scattering of plane SH waves by a semi-circular discontinuity is studied by analytical method. • The damping effects of the medium are introduced into the theoretical model. • The effects of properties of the discontinuity and medium on seismic motion are discussed. • Both the steady incident waves and the transient incident waves are considered. [ABSTRACT FROM AUTHOR]

A series of direct shear tests on specimens with artificial joints were performed to investigate the rate-dependent characteristics of damage and roughness degradation of three-dimensional joint surfaces under different normal stresses and shear velocities. A novel method was proposed to identify and extract the damaged area of joint surfaces based on the combination of the three-dimensional scanning technology and the color image segmentation method. Based on the proposed method, two main failure modes were identified on the joint surface, including asperity wear and debris backfilling. By controlling different shear displacements and shear velocities, the rate-dependent damage evolution of the joint surface during shearing was revealed. Four damage states are defined to better understand the local damage mechanism of joints. The statistical results indicate that the damage area ratio increases with increasing normal stress and shear velocity. The damage develops more rapidly at a higher shear velocity during progressive shearing. Furthermore, the three-dimensional roughness parameter θ max ∗ / (C + 1) is measured in 36 analysis directions on the sheared joint surfaces to quantitatively describe the asperity degradation. It is observed that the average roughness parameter increases with increasing shear velocity under the same normal stress but decreases with increasing shear displacement. The results in the present study may provide some references for revealing the mechanical behavior and damage state of joints subjected to dynamic loads. Highlights: A new method is proposed to identify and extract the damage area of joint surfaces based on the three-dimensional scanning technology and the color image segmentation method. The damage area ratio increases with increasing normal stress and shear velocity. The damage develops more rapidly at a higher shear velocity during progressive shearing compared with that at a lower shear velocity. The three-dimensional roughness parameter is measured in 36 analysis directions on the sheared joint surfaces to quantitatively describe the asperity degradation. [ABSTRACT FROM AUTHOR]

• The optimal ratio of mixed-modified silt was 1% lignin and 40% construction waste fine aggregate. • Modified silt's CBR value can satisfy the standards for subgrade filling. • The silt particle gradation was improved by the construction waste fine aggregate. • The polymers generated by lignin enhanced the silt particle's cohesion. The silt in the alluvial plain of the Yellow River is characterized by uniform particle size, high porosity, and large material compressibility, which poses a challenge for filling roadbeds in this area. The study investigated the impact of lignin and construction waste fine aggregate on the physical and mechanical properties of the modified silt. The construction waste modified silt with a fine aggregate content of 30% construction waste has good compressive strength, shear strength, and degree of consolidation. The lignin modified silt with 0.5% lignin concentration has higher compressive strength, cohesiveness, internal friction angle, and compression modulus. The fuzzy comprehensive evaluation identified the optimum proportioning of 1% lignin and 40% construction waste fine aggregate for the composite modified silt and the engineering characteristics and modification mechanism of the optimum modified silt were analyzed. The California bearing ratio (CBR) test results indicated that the value of optimum composite modified silt silt increases by 118.48% compared to the plain silt, and it meets the requirements for subgrade fill as specified in the guidelines. The scanning electron microscope (SEM) test results showed that the addition of lignin and fine aggregate improved the grain composition and enhanced the silt compactness. The study demonstrates that incorporating lignin and fine aggregate in silt material can enhance its engineering properties, thereby meeting the minimal standards of filling highway subgrades. These findings can serve as a valuable reference for enhancing the quality of silt in the region. [ABSTRACT FROM AUTHOR]