In-filled Trench Research Articles

Theoretical analysis of a row of piles as passive barriers and an equivalent in-filled trench model

A theoretical study on the ground vibration isolation efficiency by a row of piles as passive barrier in a three-dimensional context was presented. The analysis was accomplished with the aid of integral equations governing Rayleigh wave scattering, used to predict the complicated Rayleigh wave field generated by a number of irregular scatters embedded in an elastic half-space. Then, the passive isolation effectiveness of a row of piles for screening Rayleigh wave was studied in detail. The effects of relevant parameters on the screening effectiveness were investigated and analyzed from the perspective of equivalence with in-filled trench. The results show that using a row of rigid piles as wave barrier is more effective than that of flexible ones, and an optimum reduction of vibration can be achieved either by increasing the size of piles or by decreasing the net spacing between the piles. Finally, based on the derived integral equation for Rayleigh wave scattering, the principle of equivalent modeling of the barrier of piles by an in-filled trench is put forward, which simplifies the analysis of vibration isolation by a row of piles.

Screening effectiveness of open and in-filled wave barriers: A full-scale experimental study

The isolation of ground-borne vibrations caused by heavy traffic, construction activities and railway transportation has gained importance in recent years with rapid urbanization. Open or in-filled trenches have commonly been used as wave barriers in reducing unwanted vibrations. There only few experimental data concerning the effects of frequency of excitation, soil layering, material type and dimensions of the wave barrier on vibration control and isolation. In the present study, a series of full scale field experiments were conducted in order to investigate the screening efficiency of open, water filled and geofoam filled trenches. The attenuation of ground borne vibration was examined to determine the effects of frequency, distance and complex behavior of layering and irregular geometry of soil profile. Moreover, the results obtained from the experimental tests were compared with the numerical and experimental findings available in literature. Consequently, the field tests confirmed that the geofoam filled trench can be used as an efficient isolation system for reducing the transmission of ground-borne vibrations.

Efficiency of Trenches on Vibration Isolation under Time Dependent Loads

Results from some parametric studies were presented to assess the dynamic response of soil surface and to investigate the effectiveness of trenches in reducing vibrations due to time dependent loads acting vertically on the soil surface for twodimensional (2-D) problems by coupling finite and infinite elements. The effects of various parameters such as height of the trench, infill materials and location of the trench on screening efficiency have been investigated. It is concluded that using open or in-filled trenches can reduce the vibrations of a structure; especially the use of an open trench provides better isolation than using an in-filled trench. Efficiency of isolation increases with height of trench. The trench height has appeared as the most important parameter on screening vibrations. The location of the trench is also effective on dynamic response of soil surface. Coupling finite and infinite elements can be easily applied to study the isolation problems.

Numerical study on screening of surface waves using a pair of softer backfilled trenches

Vibration screening effectiveness of a pair of in-filled trenches is numerically studied under conditions of plane strain using PLAXIS 2D in a linear elastic, isotropic, and homogeneous half-space acted upon by a steady-state vertical excitation. Barrier efficiency is analyzed in terms of reduction of vertical and horizontal vibration components with respect to the variations in barrier geometry and in-fill material parameters. The geometric features are normalized with respect to Rayleigh wavelength of vibration in soil. The in-fill trench material is considered to be softer and accordingly assigned lower shear wave velocities than the half-space. Non-dimensional design charts are developed and the key parameters participating in wave screening process are identified. Some recommendations are made regarding the optimal selection of these parameters. Comparison with a few published results shows close agreement. Such an isolation scheme may be advantageous in circumstances where a single trench requires unrealistic depth.

Reduction of Railway-induced Vibration using In-filled Trenches with Pipes

Reduction in railway-induced vibrations in urban areas is a very challenging task in railway transportation. Many mitigation measures can be considered and applied. Among these, a little attention has been paid to trenches. In this study, a numerical investigation on the effectiveness of in-filled trenches with pipes in reducing railway vibrations due to passing trains is presented. Particularly, a series of two-dimensional dynamic analysis was performed to model the behavior of ballasted railway track under harmonic load with ABAQUS software as a Finite Element method. In so doing, two types of in-filled trenches with pipes with steel and concrete materials have been investigated in this paper. In addition, effectiveness of pipes made of steel and concrete, filled with loose sand and clay in railway-induced vibration reduction has been assessed. The results point out that using in-filled trench with pipes does not effective a lot on railway-induced vibration reduction in comparison to other railway-induced vibration reduction methods. However, in-filled trenches with steel pipes are much more effective than in-filled trenches with concrete pipes. Moreover, filling pipes with loose sand and clay does not have any effect on vibration reduction efficiency of these in-filled trenches.

Isolation of plane shear wave using water saturated trench barrier

The article presents a theoretical investigation of the propagation of normally and obliquely incident plane shear waves past a rectangular trench filled up with water saturated soil sandwiched between anisotropic elastic media. The motivation for this work is due to the effectiveness of the isolation of waves by the in-filled rectangular trench. Unlike the most of the previous researchers, this model considers the soil–structure interaction effects and directly determines the influence of barrier in the form of in-filled trench on the mode of wave propagation. It is of interest to determine the reflection and transmission coefficients, and the energy partition distribution of shear waves in the in-filled rectangular trench showing the influence of barrier on the propagation of waves. An extensive parametric study through numerical computation is carried out to investigate the influence of the material properties of the in-filled trench and the amplitude ratios on shear waves. The in-filled trench barrier directly declines the intensity of waves significantly in such a way that the waves do not create any hazards to the nearby structures, if exists at all.

The horizontal amplitude screening effects of a rectangular strip in-filled trench

The horizontal amplitude screening effects of an in-filled trench are solved using the boundary element method in the frequency domain. Dimensionless parametric studies are performed to assess the screening effects of the trench in terms of the geometry, in-filled material, foundational embedment, and shear wave velocity ratio of the in-filled material to the surrounding soil. The results show that the screening effects of the in-filled trench depend highly on the trench geometry and the velocity ratio of the in-filled material to the surrounding soil. The embedment ratio of the foundation and other factors are relatively unimportant.

Effects of Geometrical Properties of Rectangular Trenches Intended for Passive Isolation in Sandy Soils

Wave barriers are placed actively and passively in the ground to reduce the transmission of vibration produced by industry, traffic, train, etc. They include open trenches, in-filled trenches and sheet piles, etc. In most recent studies, the researchers have worked on parameters such as depth, width, length of trenches and also, the distance between the source of vibration and trench in cohesive soils. Most researches are evaluation on screening induced by shallow foundation. In this study the passive isolation has been investigated with the help of open trenches screening against the vibration produced by deep foundations in sandy soils, and the effect of trench angle and radius have been studied. Moreover, the reasons for amplitude increasing before open trenches have been evaluated. Three dimensional finite element analyses (FEM) with ANSYS software are used to achieve an exact parametric study on passive screening. The assumed strains are less than 10-3so the bilinear Elasto-Plastic behavior has been utilized.

Full scale experimental study on vibration scattering using open and in-filled (GeoFoam) wave barriers

Ground vibrations induced by machine foundations can cause unfavourable effects on the nearby buildings ranging from annoyance to structural damage. Most of these vibrations propagate in the form of surface (Rayleigh) waves. Machine foundations produce a steady state vibration, for which, wave barriers can be a successful technique to minimize these effects by scattering the generated steady state surface waves. A full scale field experimental study has been conducted to investigate the protective performance of both open and in-filled trench with GeoFoam material as well as to examine the influences of wall geometry and location from the vibratory source on the isolation efficiency. An innovative approach to construct GeoFoam trench as a wave barrier is proposed in this study as well. The results of the field experimental investigations are analyzed and interpreted to provide recommendations for implementation in design. Experimental results show that both open and GeoFoam barriers can effectively reduce the transmitted waves. The field experimental results have been compared with those obtained from the developed numerical model using a finite element package, ABAQUS.

Field experiments on wave propagation and vibration isolation by using wave barriers

In this paper, the obtained results from the experimental studies describe the basic characteristics of wave propagation and ability of possible measures to reduce the impact of soil vibrations on structural response for both active and passive isolation cases. A series of field tests on the foundation vibrations generated by electrodynamic shaker are performed to examine the screening efficiency of open and in-filled trench barriers which are constructed for full-scale measurement. From field measurements of amplitude with and without the barrier, the amplitude reduction ratio is estimated at different points of interest. Wave propagating characteristics and frequency-dependent screening effects of the wave barriers are investigated according to various isolation material stiffnesses. The remarkable outcomes from these experimental studies can be briefly generalized as follows: backfilled trench with softer material than soil is more effective for the passive isolation than the active one. The reduction effects of wave barriers depend on the frequency of vibration source for both passive and active isolation cases. In-situ measurements confirm that vibration screening systems using open or in-filled trench barriers can be applied as a reduction measure for soil vibrations due to a moving load which is considered as stationary wave source in this problem.

3D analysis of in-filled trench as passive barriers for ground vibration isolation

The three-dimensional (3D) problem of the ground vibration isolation by an in-filled trench as a passive barrier is studied theoretically. Integral equations governing Rayleigh wave scattering are derived based on the Green’s solution of Lamb problem. The integral equations are solved accurately and efficiently with an iteration technique. They are used to evaluate the complicated Rayleigh wave field generated by irregular scatterers embedded in an elastic half-space solid. The passive isolation effectiveness of ground vibration by the in-filled trench for screening Rayleigh wave is further studied in detail. Effects of relevant parameters on the effectiveness of vibration isolation are investigated and presented. The results show that a trench filled with stiff backfill material gets a better isolation effect than a soft one, and increasing the depth or width of the in-filled trench also improves its screening effectiveness. The effectiveness and the area of the screened zone are surging with the increase in the length of the in-filled trench.

Surface Wave Tests for Vibration Mitigation Studies

Wave barriers (open or in-filled trenches) are often used in engineering practice to reduce ground vibrations caused by industrial activities or transportation systems. Typically, most of the energy is transmitted in the form of Rayleigh waves so that information related to their propagation can be very useful in the design process. This technical note presents a case study in which both active and passive surface wave tests have been used in the design of a vibration mitigation barrier. It is shown that several pieces of information can be inferred from these tests for specific applications: source characterization in terms of dominant frequencies and direction of propagation; dominant wavelength for the preliminary design; and soil characterization for the construction of a numerical model aimed at analyzing the performance of the wave barrier.

Using multiple neural networks to estimate the screening effect of surface waves by in-filled trenches

Trenching is an economical and effective method to reduce surface vibrations and isolate structures from shaking. Previous reports on vibration screening concentrated on either experimental work or analytical study. Due to the construction of more complex structures in the last two decades, presenting more complicated boundary conditions, a variety of numerical methods have been used. Complexity of formulation, the large number of parameters involved, and the difficulty and time required to analyze an effective vibration screening makes the direct numerical approach impractical. The purpose of this paper is to explore the use of an artificial neural network to estimate the effectiveness of a vibration screening trench. Three artificial neural networks, BPN, GRNN, and RBF, are used to evaluate the performance of a chosen physical model. The results show that all three models can be used to evaluate effectiveness of screening trenches with varying accuracy, with GRNN having the highest accuracy. There is much stronger agreement with data of numerically calculated results for neural networks than for empirical multi-variate regression methods.

Reduction of ground vibration by means of barriers or soil improvement along a railway track

Trains running in built-up areas are a source to ground-borne noise. A careful design of the track may be one way of minimizing the vibrations in the surroundings. For example, open or infilled trenches may be constructed along the track, or the soil underneath the track may be improved. In this work, the influence of the track design and properties on the level of ground vibration due to a vehicle moving with subsonic speed is examined. A coupled finite element-boundary element model of the track and subsoil is employed, adopting a formulation in the moving frame of reference following the vehicle. The computations are carried out in the frequency domain for various combinations of the vehicle speed and the excitation frequency. The analyses indicate that open trenches are more efficient than infilled trenches or soil stiffening–even at low frequencies. However, the direction of the load is of paramount importance. For example, the response outside a shallow open trench may change dramatically when horizontal load is applied instead of vertical load.

Wave Barriers for Reduction of Train-Induced Vibrations in Soils

This paper is aimed at studying the effectiveness of different vibration countermeasures in isolating the ground vibrations induced by trains moving at sub- and supercritical speeds, with respect to the Rayleigh wave speed of the supporting soils. The vibration countermeasures considered herein include the installation of open trenches, in-filled trenches, and wave impeding blocks. The 2.5D finite/infinite element approach developed previously by the authors is employed in this study. This approach allows us to consider the load-moving effect of the train in the direction normal to the two-dimensional profile considered, and therefore to obtain three-dimensional results using only two-dimensional elements. The moving train is simulated as a sequence of moving wheel loads that may vibrate at some specific frequencies. The performance of the three types of wave barriers in isolating soil vibrations for trains moving at sub- and supercritical speeds with various excitation frequencies is evaluated with respect to some key parameters, along with suggestions made for enhancing the isolation efficiency.

Reduction of train-induced building vibrations by using open and filled trenches

A numerical investigation on the effectiveness of open and in-filled trenches in reducing the building vibrations due to passing trains is presented. Particularly, a two-dimensional soil-structure system containing the cross-section of a railway embankment, the underlying soil, a trench barrier and a nearby six-storey building is considered. For the analysis, a time domain coupled boundary element-finite element algorithm is employed. Unlike most of the previous formulations, this model completely considers the soil-structure interaction effects and directly determines the effect of the wave barrier on the structural response. The effects of geometrical and material properties of the trench and its backfill material on the structural response are investigated. The results point out that using a trench barrier, a reduction level up to 80% of the building vibrations and internal forces can be achieved. Increasing the depth or the width of a trench may improve its reduction effect and a softer backfill material results in a better isolation effect.

Three-Dimensional Analyses of Wave Barriers for Reduction of Train-Induced Vibrations

This paper explores the use of a three-dimensional finite-element analysis to model soil vibrations due to high-speed trains on bridges. Finite-element meshes include the bridge superstructure, bridge foundations, nearby building foundations, and piles. Wheel elements represented by appropriate mass, damping and stiffness factors were used to simulate a moving high-speed train. Along the mesh boundaries, absorbing boundary conditions were employed to avoid fictitious wave reflections. Isolation methods to reduce soil vibrations were investigated including construction of open and infilled trenches and soil improvement. Vibration isolation effects due to building foundations and piles were also studied. The finite-element results indicate that suitable axial stiffness between two simple beams can reduce vibration significantly, especially at a near-resonance condition. Operating with an appropriate train velocity to avoid resonance can be another way to reduce vibrations. Suitable mat foundations can significantly reduce soil horizontal vibration, but cannot isolate vertical vibration. Soil improvements near the bridge do not effectively attenuate low-frequency vibrations. Infilled and open trenches can isolate soil vertical vibration; however, their efficiency seems disproportionate to their cost.

Reduction of train-induced vibrations on adjacent buildings

In this paper, the procedure for deriving an infinite element that is compatible with the quadrilateral Q8 element is first summarized. Enhanced by a self mesh-expansion procedure for generating the impedance matrices of different frequencies for the region extending to infinity, the infinite element is used to simulate the far field of the soil-structure system. The structure considered here is of the box type and the soils are either homogeneous or resting on a bedrock. Using the finite/infinite element approach, a parametric study is conducted to investigate the effect of open and in-filled trenches in reducing the structural vibration caused by a train passing nearby, which is simulated as a harmonic line load. The key parameters that dominate the performance of wave barriers in reducing the structural vibrations are identified. The results presented herein serve as a useful guideline for the design of open and in-filled trenches concerning wave reduction.

A parametric study of wave barriers for reduction of train-induced vibrations

In this paper, a finite/infinite element scheme developed previously by the authors is employed to investigate the effectiveness of three different wave barriers, i.e., the open trench, in-filled trench, and elastic foundation, in reducing the ground vibrations caused by the passage of trains. The mathematical model adopted herein is the two-dimensional profile that contains the cross-section of the railway, barrier and underlying soils, with the moving train loads simulated as a vertical harmonic line load. Concerning the effect of isolation, the geometric and material parameters of the three barriers investigated include the distance to rail, depth, width and thickness, damping ratio, shear modulus, mass density, Poisson's ratio, elastic modulus, etc. Also examined is the effectiveness of the three barriers with respect to different exciting frequencies. Conclusions are made regarding the selection of optimal parameter values for the three barriers in isolating the train-induced ground vibrations. © 1997 John Wiley & Sons, Ltd.

Active Isolation of Machine Foundations by In-Filled Trench Barriers

Vibratory energy transmitted through propagating waves generated by machine foundations can be detrimental to adjacent structures or sensitive equipment operating nearby. Most of the vibratory energy affecting structures nearby is carried by surface waves that propagate in a zone close to the ground surface. Thus, for machine foundations vibrating at moderate to high frequencies, vibration amplitudes in the vicinity of the foundation can be reduced significantly by installing an annular in-filled trench wall around it. An in-filled trench wave barrier reduces the ground motion by interception, scattering, and diffraction of the surface waves. This approach of isolating a vibrating machine foundation from its surroundings is known as active isolation. This paper presents a numerical investigation on active isolation of machine foundation by in-filled trench wave barriers in a three-dimensional viscoelastic half-space. A rigorous boundary element method (BEM) algorithm for dynamic analysis of three-dimensional solids has been used to study the effects of various geometric and material parameters on the performance of the in-filled trench barriers. Important dimensionless parameters have been identified and design guidelines are presented.