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It has been widely recognised that near-fault ground motions can be distinctly different from far-fault ground motions, in terms of their amplitudes and spectral characteristics, and there are a number of studies investigating the effects of near-fault ground motions on the structural response. However, only a few studies focus on underground tunnels, and most of them consider vertically incident seismic waves, neglecting the wave passage effect which is critical for long tunnels. This paper investigates the consequences of near-fault pulse-like ground motions on the seismic tunnel response, with an example of a tunnel embedded in saturated poroelastic soil. The input motions are represented by obliquely incident P1 waves, and the wave passage effect along the longitudinal direction is considered by a 2.5D modelling technique. The seismic tunnel response for near-fault pulse-like and far-fault ground motions is compared. Additionally, artificial ground motions, which have consistent acceleration response spectra with the near-fault pulse-like ground motions, but without velocity pulses, are generated to gain further insight into the contribution of velocity pulses. It is shown that the near-fault pulse-like ground motions can noticeably increase the tunnel internal forces, due to large seismic energy associated with the velocity pulses. For pulse-like ground motions with similar acceleration response spectra, the fling-step velocity pulse can be more detrimental to the tunnel than the forward-directivity velocity pulse. Moreover, the amplification effect of the near-fault pulse-like ground motions on the tunnel internal forces tends to be more prominent for large vertical angles of incidence, highlighting the significance of considering the oblique incidence case for seismic design. • Interaction of the tunnel and saturated poroelastic soil for obliquely incident seismic waves. • The longitudinal tunnel response due to the wave passage effect. • Near-fault pulse-like ground motions tend to increase internal forces in the tunnel lining. • Effects of forward-directivity and fling-step velocity pulses. • Influences of pulse-like ground motions are more prominent for large vertical angles of incidence. [ABSTRACT FROM AUTHOR]

Lateral variations of shear wave velocity (V S) profile and time-averaged shear wave velocity in the upper 30 m (V S 30) are important indicators of site condition and significant contributors to uncertainty in earthquake ground motion and seismic hazards. Few previous studies involved in quantifying these lateral variations, especially at short distances, due to limited data at closely spaced sites. This study quantitatively investigated the lateral variation of V S profile and V S 30 over plain and piedmont terrains, focusing on short distances ranging from hundreds of meters to several kilometers. 2510 plain and 749 piedmont borehole profiles from the mainland China borehole profile database were employed to examine these variations using the variogram as the geo-statistics tool. The main findings include: 1) Over plain terrain, the variation in site conditions between sites does not significantly increase with separation distance within a certain range (typically from 1 km to 3–5 km). Over piedmont terrain, site condition variation steadily increases with distance. 2) The variation of site condition over piedmont terrain is higher than that over plain terrain. Nonetheless, for both terrains, the dispersion of site condition between sites at distance of <1 km is engineering negligible, and the correlation of site conditions between sites within 5 km remains strong; 3) For both terrains, the lateral variation of V S in deeper layers is higher than that in shallower layers. The study outcomes emphasize the importance of incorporating the information of nearby measurements in site condition estimations. The study outcomes can also be utilized in the optimization of borehole sampling design for microzonation projects and the evaluation of site condition dispersion at inferred sites. • Lateral variations of V S profile & V S 30 over plain & piedmont terrains were modeled. • The study focuses on lateral variations at short distance, down to < 1 km scale. • For gentle terrains, site conditions within short distance are strong correlated. • Plain has lower site condition variation than piedmont, with distinct properties. [ABSTRACT FROM AUTHOR]

River valley terrain can lead to local amplification effects of site seismic responses and significant spatial variation of strong ground motions. This paper presented a semi-analytical solution for the scattering of incident plane P-waves by a saturated river valley with arbitrary shapes containing water, using the moment method and the wave function expansion method. The influence of factors such as valley geometry shapes, soil porosity, wave incident angle and frequency on the seismic response of valley topography is further investigated. Parameter analysis shows that these factors have a significant impact on the site seismic response. Soil porosity has a greater impact on the horizontal response of the site than on the vertical response. Moreover, the soil porosity is directly related to the amplitude of the pore pressure, while the incidence angle and frequency of the incident wave determine the distribution position of the pore pressure amplitude. This semi-analytical solution can be seen as an attempt to solve the scattering problem of incident P wave by saturated river valleys of arbitrary shapes containing water. The purpose of this paper is to provide a reference and a possible way for subsequent scholars to study the analytical solution to this problem. The conclusions drawn from the parameter analysis in this paper can also serve as a theoretical basis for seismic fortification in saturated valley areas. • Semi-analytical model for plane P waves scattering by saturated river valley with arbitrary shapes containing water. • Moment method is applied to obtain the semi-analytical solution to system response. • Influence of the water, medium porosity, and incident wave on ground surface displacement is investigated. [ABSTRACT FROM AUTHOR]

This paper presents shaking tests conducted on a 1/30-scale utility tunnel model employing a multi-shaking table array system. The model utility tunnel-soil system was subjected to input motions simulating near-fault ground motions with and without velocity pulse. The test data were collected and analyzed including acceleration, strain and displacement of the soil bed and model tunnel responses. The soil data analysis indicated that the boundary effect of the model soil box used in the test was negligible. The observed small soil settlements confirmed that the physical and mechanical properties of the model soil did not change significantly in tests. The results also demonstrated that, in general, the transverse dynamic responses of the utility tunnel and surrounding soil under near-fault ground motion with velocity pulse were much greater than the case without velocity pulse. Therefore, the effect of velocity pulse should be considered in the design of utility tunnels. • Near-fault ground motions with and without velocity pulses were selected. • A series of scaled model tests were conducted by using a shake table array. • Transverse dynamic response of the utility tunnel model is analyzed through the test data and the result is given. [ABSTRACT FROM AUTHOR]