| 1. |
- Boström, Anders E, 1951, et al.
(författare)
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Screening effects of open trenches to ground vibrations induced by highspeed trains on a poroelastic halinspace
- 2011
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Ingår i: 5th International Symposium on Environmental Vibration, ISEV 2011; Chengdu; China; 20 October 2011 through 22 October 2011. - 9787030323736 ; , s. 777-783
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Konferensbidrag (refereegranskat)abstract
- An analytical model is proposed to investigate the screening effects of trenches to the train-induced ground vibrations in three-dimensional conditions. A fully saturated poroelastic half-space is firstly utilized to model the ground. Placed on the top of the poroelastic half-space, the embankment and soil banks beside the trenches are modelled as elastic layers with appropriate widths. The rails and sleepers are modelled as Euler beams and an anisotropic Kirchhoff plate, respectively. Biot's theory is applied to characterize the fully saturated poroelastic half-space, considering the coupling between the soil skeleton and the fluid. The governing equations are solved in the transformed domain based on Fourier transforms and Fourier series;the time domain results can be obtained by the fast Fourier transform(FFT). Numerical examples are given for a moving x2000 train that operates on the saturated poroelastic half-space. The influences of coupling effect between soil skeleton and pore water on the screening efficiency of the trench are investigated. Furthermore, the screening effects of open trenches on the poroelastic half-space are compared with that of trenches on the single-phase elastic half-space. It is found that the single-phase elastic half-space model will underestimate the screening effect of the trench significantly for supercritical train speeds.
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| 2. |
- Cao, Zhigang, 1983, et al.
(författare)
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Dynamic response of a poroelastic half-space to accelerating or decelerating trains
- 2013
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 1095-8568 .- 0022-460X. ; 332:11, s. 2777-2794
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic response of a fully saturated poroelastic half-space due to accelerating or decelerating trains is investigated by a semi-analytical method. The ground is modeled as a saturated poroelastic half-space and Blot's theory is applied to characterize the soil medium, taking the coupling effects between the soil skeleton and the pore fluid into account. A detailed track system is considered incorporating rails, sleepers and embankment, which are modeled as Euler-Bernoulli beams, an anisotropic Kirchhoff plate, and an elastic layer, respectively. The acceleration or deceleration of the train is simulated by properly choosing the time history of the train speed using Fourier transforms combined with Fresnel integrals in the transformed domain. The time domain results are obtained by the fast Fourier transform (FFT). It is found that the deceleration of moving trains can cause a significant increase to the ground vibrations as well as the excess pore water pressure responses at the train speed 200 km/h. Furthermore, the single-phase elastic soil model would underestimate the vertical displacement responses caused by both the accelerating and decelerating trains at the speed 200 km/h.
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| 3. |
- Cao, Zhigang, 1983, et al.
(författare)
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Semi-analytical analysis of the isolation to moving-load induced ground vibrations by trenches on a poroelastic half-space
- 2012
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 1095-8568 .- 0022-460X. ; 331:4, s. 947-961
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Tidskriftsartikel (refereegranskat)abstract
- A semi-analytical model is proposed to investigate the screening efficiency of trenches to moving-load induced ground vibrations. The ground is modeled as a fully saturated poroelastic half-space governed by Biot's dynamic poroelastic theory. The trenches are obtained by placing three rectangular elastic layers with appropriate width upon the poroelastic half-space. By Helmholtz decomposition, the displacement fields of the elastic layers are decomposed into three scalar potentials. Analytical solutions are obtained based on Fourier transform and Fourier series in the transformed domain. The time-domain results are obtained by the fast Fourier transform (FFT). The different performances of trenches on a saturated poroelastic half-space and a single-phase elastic half-space to the moving load-induced ground vibration are identified. It is found that the discrepancy of the screening efficiencies between the two models becomes significant when the load speed approaches the Rayleigh wave speed of the ground surface. Also, some parametric studies for the screening efficiency of the trench on the poroelastic half-space are presented.
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| 4. |
- Yuan, Z. H., et al.
(författare)
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Analytical solution for calculating vibrations from twin circular tunnels
- 2019
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Ingår i: Soil Dynamics and Earthquake Engineering. - : Elsevier BV. - 0267-7261. ; 117, s. 312-327
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Tidskriftsartikel (refereegranskat)abstract
- The calculation of vibrations from a single tunnel embedded in a full- or half-space due to underground moving trains has been well studied in the literature. A common assumption made in the majority of vibration prediction models is to neglect the presence of a neighboring tunnel, however, twin tunnels are a particularly preferred construction for urban underground railways with one as the inbound tunnel and the other as the outbound tunnel. The neglect of the interaction between twin tunnels may lead to inaccuracies of the calculation of vibrations from underground railways. The present paper proposes a novel analytical solution, which takes the multiple scattering effects between the two tunnels into account. The two tunnels are modelled as elastic hollow cylinders and the soil surrounding the tunnels as an elastic, homogeneous full-space containing two cylindrical cavities. The wave field in the full-space with two cavities consists of outgoing waves from each tunnel outside the two scattering surfaces while the wave field in the tunnel wall is a combination of outgoing and regular cylindrical waves. The translation of the outgoing cylindrical wave functions is required to satisfy the boundary conditions at the other tunnel. Numerical results show that there are two critical velocities for a twin tunnel in a full-space system, both of which are around the shear wave velocity of the soil. Through comparison with the single tunnel solution, the addition of a second tunnel at different separation distances and angles has a significant influence on the soil response, especially in the high frequency range, but the response at the tunnel with the source is not much affected.
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| 5. |
- Yuan, Z. H., et al.
(författare)
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Analytical wave function method for modelling a twin tunnel embedded in a saturated poroelastic full-space
- 2019
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Ingår i: Computers and Geotechnics. - : Elsevier BV. - 0266-352X .- 1873-7633. ; 114
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Tidskriftsartikel (refereegranskat)abstract
- An analytical wave function method for the calculation of vibrations from two tunnels embedded in a saturated poroelastic full-space due to a harmonic point load is given, in which the multiple scattering between twin tunnels is considered exactly. The two tunnels made of viscoelastic material are modelled as two hollow cylinders. The soil surrounding two tunnels is water-saturated, and modelled as a two-phase poroelastic material. The wave field in the full-space with two circular cavities is a superposition of outgoing waves outside the two cavity surfaces. As there is water in the soil, the hydraulic boundary at the tunnel-soil interface is necessary when solving this multi-scattering problem. The translation properties of outgoing waves are adopted to apply boundary conditions described in two sets of cylindrical coordinates. The proposed analytical method for modelling twin tunnels provides a new tool to study the interaction between twin tunnels buried in a poroelastic medium. Some typical numerical results are given to illustrate the influence of the soil permeability and the permeability of the tunnel-soil interface on the displacement and pore pressure responses. In addition, the results for a single tunnel are compared to those of a twin tunnel with various separation distances and angles.
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| 6. |
- Yuan, Z. H., et al.
(författare)
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Closed-Form Analytical Solution for Vibrations from a Tunnel Embedded in a Saturated Poroelastic Half-Space
- 2017
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Ingår i: Journal of Engineering Mechanics - ASCE. - : American Society of Civil Engineers (ASCE). - 1943-7889 .- 0733-9399. ; 143:9, s. 04017079-
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Tidskriftsartikel (refereegranskat)abstract
- A closed-form analytical solution for ground-borne vibrations from a tunnel embedded in a saturated poroelastic half-space is proposed in this paper. The tunnel modeled as an elastic hollow cylinder is surrounded by the water-saturated poroelastic material. The total wave field in the poroelastic half-space with a cylindrical cavity consists of the outgoing cylindrical waves and the down-going plane waves. In addition to the traction-free condition on the ground surface and the continuous conditions of displacement and stress at the tunnel-soil interface, hydraulic boundary conditions on these two scattering surfaces are required to solve this multiple-scattering problem. The transformation properties between the plane and cylindrical wave functions are employed to apply the boundary conditions expressed in both the rectangular and cylindrical coordinate systems. Numerical results for the displacements of the solid on the ground surface and the pore pressure in the saturated soil attributable to a harmonic point load applied at the tunnel invert are presented. The influence of the soil permeability and the hydraulic boundary at the tunnel-soil interface on the free-field responses is investigated. The proposed solution can serve as a benchmark for other computational methods and as an efficient tool for predicting vibrations from a tunnel embedded in a saturated poroelastic half-space.
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| 7. |
- Yuan, Z. H., et al.
(författare)
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The influence of pore-fluid in the soil on ground vibrations from a tunnel embedded in a layered half-space
- 2018
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 1095-8568 .- 0022-460X. ; 419, s. 227-248
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Tidskriftsartikel (refereegranskat)abstract
- A computationally efficient semi-analytical solution for ground-borne vibrations from underground railways is proposed and used to investigate the influence of hydraulic boundary conditions at the scattering surfaces and the moving ground water table on ground vibrations. The arrangement of a dry soil layer with varying thickness resting on a saturated poroelastic half-space, which includes a circular tunnel subject to a harmonic load at the tunnel invert, creates the scenario of a moving water table for research purposes in this paper. The tunnel is modelled as a hollow cylinder, which is made of viscoelastic material and buried in the half-space below the ground water table. The wave field in the dry soil layer consists of up-going and down-going waves while the wave field in the tunnel wall consists of outgoing and regular cylindrical waves. The complete solution for the saturated half-space with a cylindrical hole is composed of down-going plane waves and outgoing cylindrical waves. By adopting traction-free boundary conditions on the ground surface and continuity conditions at the interfaces of the two soil layers and of the tunnel and the surrounding soil, a set of algebraic equations can be obtained and solved in the transformed domain. Numerical results show that the moving ground water table can cause an uncertainty of up to 20 dB for surface vibrations.
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| 8. |
- Yuan, Z. H., et al.
(författare)
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The wave function method for calculation of vibrations from a twin tunnel in a multi-layered half-space
- 2019
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Ingår i: Soil Dynamics and Earthquake Engineering. - : Elsevier BV. - 0267-7261. ; 125
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Tidskriftsartikel (refereegranskat)abstract
- The ground vibrations due to underground moving trains cause disturbances to nearby buildings and their residents, which has been viewed as an important environmental issue. Various numerical or semi-analytical models are used to calculate the vibrations from underground railways, however, most of the prediction models adopt a single tunnel-soil system for modelling vibrations from underground trains and neglect the influence of a neighboring tunnel. In this paper, a semi-analytical wave function method is proposed for modelling vibrations from twin tunnels in a multi-layered viscoelastic and poroelastic half-space. The two tunnels are modelled as two hollow cylinders while the surrounding soil is modelled as a multi-layered half-space containing two circular cavities. The vibrations of the tunnel walls are taken as a superposition of outgoing and regular cylindrical waves. The wave field in the soil layer containing two cavities consists of down-going and up-going plane waves and cylindrical waves propagating outwards from each tunnel. In the wave function method, the transformation and translation of the plane and cylindrical waves make it possible to apply the boundary conditions at the scattering surfaces. Numerical results show that the half-space model predicts higher surface vibrations than a full-space model at equivalent surface locations. When the second tunnel is added near a deeper existing tunnel, a wider range of the free-field response above the two tunnels is significantly changed, however, the response below twin tunnels is less affected. If the separation distance between the two tunnels is smaller than five times the tunnel diameter, a twin tunnel model in a half-space is more suitable for an accurate vibration prediction at the ground surface. The cutoff effect of the rigid base is more visible for shallow bedrock at lower frequencies while the influence of the bedrock is quite limited at higher frequencies.
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