In this study, the effects of grain size and moisture content on the interface shear strength of sandy soils against a polypropylene biaxial geogrid were evaluated using a large-scale shearing device. Soil specimens with various maximum grain sizes (2.0–13.2 mm) and moisture contents (5%–11%) were sheared against the geogrid at normal stress values of 250–750 kPa. The interface shear strength was primarily influenced by the soil’s internal shear strength, the friction between the soil and the geosynthetic plane surface, and the resistance provided by the transverse ribs. The results indicated that the shear strength of the soil–geogrid interface decreased as the maximum grain size of the soil decreased. The lower interface shear strength was primarily a consequence of the reduced internal shear strength and friction. The internal shear strength contributed more than 50% of the shear strength of the soil–geogrid interface, whereas the contributions from the friction or transverse ribs were less than 30%. The transverse ribs provided effective resistance when the median of the particle size distribution was greater than the thickness of the transverse ribs. Increasing the soil moisture content reduced the interface shear strength, especially when the moisture content exceeded the optimal moisture content. Increasing the moisture content also negatively impacted the bearing resistance of the transverse ribs.

Dynamic stress concentration in tunnels and underground structures during earthquakes often leads to serious structural damage. A series solution of wave equation for dynamic response of underground circular lining tunnels subjected to incident plane P waves is presented by Fourier‐Bessel series expansion method in this paper. The deformation and stress fields of the whole medium of surrounding rock and tunnel were obtained by solving the equations of seismic wave propagation in an elastic half space. Based on the assumption of a large circular arc, a series of solutions for dynamic stress were deduced by using a wave function expansion approach for a circular lining tunnel in an elastic half space rock medium subjected to incident plane P waves. Then, the dynamic response of the circular lining tunnel was obtained by solving a series of algebraic equations after imposing its boundary conditions for displacement and stress of the circular lining tunnel. The effects of different factors on circular lining rock tunnels, including incident frequency, incident angle, buried depth, rock conditions, and lining stiffness, were derived and several application examples are presented. The results may provide a good reference for studies on the dynamic response and aseismic design of tunnels and underground structures.

This study evaluated the deformation behaviour, vertical stress, strain, and failure mode of a 14 m-high (H) geogrid-reinforced slope supporting an 8 m-high embankment using centrifuge models. Tests were conducted at an acceleration of up to 40g. Additional tests were conducted to investigate the effects of layer spacing (0.5 to 1.0 m at prototype scale) and slope inclination (45° to 90°) on the performance of the reinforced slopes. The maximum strain (∼0.04%) occurred in the reinforcement layer nearest to the crest of the slope. Potential slip surfaces were identified from peak strains in the reinforcement layers. The vertical stress was redistributed owing to the tensile behaviour of the geogrid, and vertical stress within the soil slope was transferred to the area near the face of the slope (0.26–0.77H from the face). As the layer spacing increased (from 0.5 to 1.0 m), the potential slip surface moved away from the slope face with increasing deformation, which reduced the overall stability of the reinforced slope. The model with a vertical slope generated the largest reinforcement strain (∼0.2%), vertical settlement, and surface bulging compared with the model with a mild slope.