In-filled Trench Research Articles

Broadband surface wave manipulation by periodic barriers in unsaturated soil.

Periodic wave barriers have been widely used to manipulate elastic waves propagating in saturated and single-phase soil due to their attenuation zone properties. However, it is difficult to promote application of periodic barriers in unsaturated soils due to their complex constitutive relationship. In this study, manipulation of surface waves by periodic in-filled trench barriers in unsaturated soil has been studied based on the periodic theory. The dispersion relations of a periodic structure for surface waves in unsaturated soil are determined. The attenuation mechanism of evanescent surface waves is revealed. Next, the effects of several key parameters of unsaturated soil on the attenuation zones of the periodic in-filled trench barriers are comprehensively discussed. It is found that in a particular range for material parameter, the surface waves are attenuated over the entire frequency range due to the viscosity of fluid. Finally, a periodic in-filled trench barrier is designed according to a field test of ground vibration induced by a train, and its performances in mitigating surface waves propagating in unsaturated and saturated soils are conducted and compared by conducting analysis in time domain. This investigation provides a new insight for manipulating surface waves by periodic barriers. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.

Surface wave isolation by variable depth infilled trenches

Excessive environmental vibrations generated by urban traffic pose adverse effects on nearby structures and residents. These vibrations are predominantly carried by surface waves, which are localized within the surface layer of soil. The isolation of surface waves through the embedding of periodic wave barriers in soils between the source and the receiver has gained significant attention in recent years. In this paper, a novel approach is proposed for isolating surface waves induced by urban traffic through the use of variable depth infilled trenches. This innovative design not only achieves efficient surface wave isolation but also minimizes the consumption of structural materials. Based on the measured dominant frequency range of rail transit and the available soil parameters, variable depth infilled trenches are designed with suitable dimensions. The eigenvalue equation is solved using the finite element method to derive the dispersion relations and bandgap of identical regularly spaced trenches. To study the efficacy of the proposed structure, a finite element model of the soil-infilled trench system is developed using COMSOL. The mechanism underlying the isolation of surface wave is elucidated, and the effect of variable angle α on the isolation efficiency within 40–50 Hz η40−50Hz of surface waves is studied. The results of this study reveal that for variable angle α of 15°, the surface wave isolation efficiency within 40–50 Hz η40−50Hz is 90.9 % and 92.5 % for uniformly increasing depth infilled trenches and uniformly decreasing depth infilled trenches, respectively. Although the surface wave isolation efficiencies predicted for the variable depth infilled trench arrangements are only 93.8 % and 95.5 % of those predicted for the regularly spaced identical infilled trenches, the variable depth arrangements result in a remarkable 34 % reduction in material usage. These findings highlight the potential of the proposed variable depth infilled trenches as a cost-effective and efficient solution for surface wave isolation.

Experimental Study on Reutilization of Waste Rubber Chips with Sheetpiles as a Coupled-Wave Barrier to Reduce Ground-Borne Vibrations

Abstract Purpose Environmental and man-made vibrations due to various sources have become an environmental issue in recent years. Wave barriers such as open and in-filled trenches have been commonly used in the mitigation of these vibrations. Even though the open trench has exhibited better performance than the others, it may not be applicable or feasible in many cases. Therefore, soft and stiff barriers have been used for the same purpose. The present study aims to reveal the vibration isolation performance of not only single barriers such as rubber chips in-filled trenches and sheetpiles but also a novel barrier, rubber chips-sheetpile coupled barriers. Methods Rubber chips and sheetpiles were employed as soft and stiff wave barriers, respectively. The screening effectiveness of rubber chips, sheetpiles and their coupled form was examined through comprehensive field tests. Vibrations having frequencies in the range of 10–80 Hz were generated by a state-of-the-art mobile seismic shaker and measured by highly sensitive acceleration and velocity pickups in the absence and presence of these wave barriers. The effectiveness of the wave barriers was quantitatively determined. Results and conclusion While the sheetpile was more effective than rubber chips at low frequencies, the case was vice versa at higher frequencies. However, the coupled wave barrier outperformed other barriers in each case. If one barrier could not provide the required amount of isolation or is only effective within a limited range of frequency, using a coupled barrier with the installation of the other may significantly provide better vibration isolation.

Vibration mitigation using dual-open and infilled trenches in layered soil media: Field tests and numerical simulations

Ground-borne vibrations are increasing at a rapid rate due to the rise in urban expansion and industrial activities. The current solution to mitigate the unwanted vibrations is limited to the use of single trenches that require unrealistic depths. This paper presents the possibilities of using dual open and infilled trenches to mitigate the vibrations generated due to continuous harmonic motions. Full-scale field tests and comprehensive numerical studies were performed to systematically design dual trenches. The field vibration tests were performed under a wide range of frequencies using the Lazan-type mechanical oscillator. Similarly, numerical studies have been performed using finite element analysis software, PLAXIS 2D. Expanded polystyrene (EPS) geofoams of different densities, bentonite, ceramsite, concrete, and sand-rubber mixture were used as the infill materials. The normalized depths of 0.40 and 0.50 were observed as the optimal values to reach an average amplitude reduction ratio (average ARR) of 0.25 for the dual open and EPS15-infilled trenches, respectively. The isolation efficiency of EPS15-infilled trenches was observed to be 178 % higher compared to the EPS48-infilled trenches. The performance difference between EPS15 and ceramsite-filled dual trenches was observed to be only 4 % in terms of average ARR, the former being superior.

Periodic WIB-trench wave barriers for seismic surface waves

Seismic surface waves possess detrimental characteristics of low frequency and significant amplitude, posing a threat to buildings and structures. This paper proposes a novel combined wave barrier, referred to as the periodic WIB-trench barrier, which is designed specifically for the purpose of isolating seismic surface waves. The periodic WIB-trench barrier consists of wave impeding blocks (WIB) and infilled trenches. The surface wave bandgaps of the periodic WIB, infilled trench, and the combined wave barrier have been compared, while the vibration modes of these three barriers have also been acquired to reveal the mechanism of the bandgaps of surface waves. Subsequently, a finite barrier transmission model has been established to analyze the vibration isolation performance of the periodic WIB-trench barrier in both the frequency domain and time domain. The results demonstrate that the proposed combined wave barrier exhibits larger bandgap widths and lower boundary frequencies when compared to the periodic WIB and periodic infilled trenches. Specifically, the bandgaps of the periodic WIB-trench barrier ranges from 4.5 to 6 Hz, 9.5 to 12.8 Hz, and 15 to 20 Hz. Through the confinement of surface wave energy within the barrier unit cells or the conversion of surface waves into body waves, an effective vibration mitigation approach proposed in this paper can be achieved. This research offers a novel perspective on the design of periodic barriers for seismic surface waves isolation purpose.

Numerical Analysis of the Mitigation Performance of a Buried PT-WIB on Environmental Vibration.

Environmental vibration pollution has serious negative impacts on human health. Among the various contributors to environmental vibration pollution in urban areas, rail transit vibration stands out as a significant source. Consequently, addressing this issue and finding effective measures to attenuate rail transit vibration has become a significant area of concern. An infilled trench can be arranged periodically along the propagation paths of the waves in the soil to attenuate vibration waves in a specific frequency range. However, the periodic infilled trench seems to be unsatisfactory for providing wide band gaps at low and medium frequencies. To improve the isolation performance of wave barriers at low to medium frequencies, a buried PT-WIB consisting of a periodic infilled trench and a wave impedance block barrier has been proposed in this paper. A three-dimensional finite element model has been developed to evaluate the isolation performance of three wave barriers. The influence of the PT-WIB's parameters on isolation performance has been analyzed. The results indicate that the combined properties of the periodic structure and the wave impedance block barrier can effectively achieve a wide attenuation zone at low and medium frequencies, enhancing the isolation performance for mitigating environmental vibration pollution.

Filtering property of periodic in-filled trench barrier for underground moving loads

The filtering properties of a 2-dimensional (2D) periodic in-filled trench barrier system subjected to anti-plane and in-plane moving loads are investigated separately by combining the spatial Fourier transform and periodic structure theory. By the aid of spatial Fourier transform, the governing equation of the periodic system is reduced in dimension. Based on the periodic structure theory, the closed-form solution of the dispersion equation for anti-plane wave is obtained; while for in-plane wave, the State-Space-Transfer-Matrix-Method (SSTMM) is introduced to solve the dispersion relation. Furthermore, the attenuation zones (AZs) varying with the transformed wave number, i.e., the AZs-kx graph, are obtained. Comparing the load-speed-line cluster of the moving excitation source with the obtained AZs-kx graph, the vibration isolation regions of the 2D periodic in-filled trench barrier in frequency-wave number space under moving loads can be found. To validate the present theoretical results, the performances of a 2D finite periodic in-filled trench barrier embedded in soil matrix and subjected to anti-plane and in-plane moving loads are numerically simulated, respectively. It is found that the AZs-kx graph plays a crucial role in revealing the isolation mechanism of the periodic in-filled trench barrier under moving loads. Theoretically speaking, it can be used to derive the vibration isolation regions for arbitrary excitation time histories of the moving-load inputs. The methodology proposed in the present paper can be used to design the continuous-type periodic wave barrier for isolating ambient vibration induced by moving loads.

Influence of Geometric Dimensions in Screening Efficiency of Geofoam Crumb Rubber Infilled Trench

Abstract: This study evaluates the influence of geometric dimensions in screening efficiency of styrene butadiene crumb rubber and expanded polystyrene geofoam infilled trench (GRFT). Since used rubber is a waste product, its proper disposal is matter of concern.Experimental analysis was conducted in the laboratory conditions. Intermittent arrangement or alternate arrangement in particular composition ratio (CR) was used to arrange infill material. Impact loading condition used for the analysis and efficiency of the system evaluated based on the amplitude reduction ratio (ARR).The results show that geometric dimensions like length, breadth and depth have significant effect on the efficiency of GRFT wave barrier system.

Analysis of Coir Composite In-filled Trench in Mitigating Ground Vibration

Abstract: Ground vibration is a significant geo hazard that might detrimentally affect civil engineering designs and constructions. Vibrations caused by heavy vehicles, mining railway, traffic and other construction activities have become the major reason for ground vibrations. These destructive vibrations can be isolated by providing open or in filled trench barriers as it creates material discontinuity. In this study the performance of coir composite in filled trenches in mitigating ground vibration experimentally as well as numerically by using PLAXIS 2D software is carried out by varying different parameters such as geometrical parameters, source distance, load intensities etc. It was observed that the proposed trench having coir and latex components in equal proportions can efficiently isolate the ground vibrations.

Performance of rubber-concrete composite periodic barriers applied in attenuating ground vibrations induced by metro trains

Recently, the use of periodic vibration isolation barriers (PVIBs) has emerged as a significant method for attenuating environmental vibrations along the propagation path. Previous studies have indicated that periodic infilled trenches and piles can effectively isolate low-frequency surface waves. However, a considerable number of these periodic structures require full-size shipments or cast-in-place construction, thus increasing the shipment difficulty or construction period. In addition, few experimental studies have reported on the performance of PVIBs under underground excitation. To solve these problems, this study proposes a novel periodic composite rubber-concrete barrier (PCRCB) with prefabricated assembly characteristics. A laboratory test was performed, in which the calculated frequency band gap (FBG) and attenuation zones of the optimised PCRCB were validated under ground-borne and underground hammering excitations. Then, a numerical model was developed to analyse the vibration mitigation effect of the optimised PCRCB considering the metro train loads. The results of the laboratory study demonstrated that the depth of the impact load affects ground vibration attenuation. The optimised PCRCB has been proven to exhibit good vibration isolation performance. The results of the numerical study demonstrate that the vibration mitigation effect of the PCRCB on the ground surface is good under underground metro train loads. The insertion loss (IL) increases, but its value is less than 2 dB, with the ratio of burial depth to tunnel base depth increases from 1 to 2 times. Accordingly, the ratio of the burial depth to the tunnel base depth is recommended to be 1 in the vibration isolation project of an underground metro train.

Field Testing on active isolation of vibrating foundations in Middle-frequency range

Open or in-filled trenches are usually used for suppressing disturbing ground vibrations induced by various man-made sources such as construction activities, transportation systems and power plants. However, using a trench to suppress low-frequency excitations, may be either impractical or inefficient. This study evaluates different mitigation strategies to suppress middle-frequency ground vibrations (i.e. between 25 and 40 Hz), generated by a rotating mass vibrator mounted on a shallow foundation in the field. The mitigation strategies encompassed placing isolating materials including sand-rubber mixture (SRM) in bags and block-type EPS geofoam, in sidewalls and bottom of a cubic pit excavated underneath the vibrating foundation and then backfilling the pit. Using EPS geofoam resulted in up to 30% and 20% reduction in ground vibration amplitudes of vertical and horizontal components, respectively. However, SRM-filled bags provided better efficiency which increased with rubber content. For instance, up to 40% and 50% reduction were observed, respectively in vertical and horizontal ground vibrations, when a SRM mixture with 25% rubber content was used. The excavation depth in current study was comparably lower than that of an open trench, for the same vibration reduction level, and thus considerably reduced the earthwork volume.

A state-of-the-art review paper on the vibration screening techniques using open and in-filled trenches

A state-of-the-art review paper on the vibration screening techniques using open and in-filled trenches

Full scale field studies for assessing the vibration isolation performance of single and dual trenches

The ground-borne vibrations induced due to construction operations transmit to the surroundings in the form of stress waves. These vibrations severely impact sensitive structures and cause human annoyance. Present solutions to vibration isolation using barriers are limited to the use of single open and infilled trenches. However, one of the significant drawbacks of using single trenches is its insignificant depth requirements. Hence, an attempt has been made to explore the possibilities of utilizing dual open and infilled trenches by conducting a full-scale experimental investigation under different frequencies of excitations. A well-accepted material, geofoam, was used as an infilling material in the two trenches of the same geometries. The influence of three different vibration locations was analyzed under five combinations of single and dual trenches. The findings from the experimental study suggest that the use of dual trenches suppresses the vibrations more effectively than single trenches. The dual open and geofoam-infilled trenches of the normalized depth of 0.3 decreased the vertical vibrations by 76% and 65%, respectively, compared to no trench conditions. Moreover, to achieve a 50% reduction in vibration, the normalized depths required for the single and dual open trenches were found to be 0.27 and 0.14, respectively.

Assessing vibration isolation performance of single and coupled wave barriers through field experiments

Wave barriers have become a common practice in the mitigation of undesired ground vibrations when direct isolation of the source has not been applicable. Even though the vibration isolation performance of open and in-filled trenches has been scrutinized, only a limited number of experimental studies are available about stiff wave barriers such as piles and sheetpiles. The present study aimed at assessing not only the screening effectivenesses of single barriers such as open trench and sheetpile but also the coupled open trench-sheetpile barrier. 15 m long, 0.75 m wide, 3 m deep single open trench and 15 m long, 8 m deep sheetpile were investigated in full-scale vibration tests. The influences of excitation frequency, source-barrier distance and barrier type on the vibration isolation were examined. The efficacy of the single and coupled-wave barriers was quantitatively presented within a wide range of frequencies (10–80 Hz) based on field measurements using highly sensitive accelerometers and geophones. No vibration isolation was provided at the excitation frequency of 10 Hz, while all the wave barriers provided an appreciable amount of reduction in the amplitudes of the vibrations at other frequencies. In most of the test configurations, the open trench and the coupled-wave barrier exhibited similar isolation performance and outperformed the sheetpile. In cases the sheetpile has already been installed, the implementation of an open trench in front of the sheetpile may noticeably improve the screening effectiveness.

Horizontal hollow pipes used as vibration isolation barriers: Numerical modelling and design optimization

Open trenches are one of the most popular vibration isolation techniques used to reduce the transmission of ground vibrations. Despite several advantages of this systems for isolating ground vibrations, the major drawback is the geotechnical instability of the trenches. To solve this issue, the author have created a novel approach that involves filling the open trenches with hollow pipes in specific pattern. This is a novel method for mitigating ground vibrations by burying hollow pipes horizontally. Through the use of three-dimensional (3D) finite-element modeling, the effectiveness of such hollow pipes in decreasing ground vibrations generated by harmonic stress excitation on the ground surface was investigated. Compared to open trench barriers and in-filled trench, these pipe assemblages have been demonstrated to be highly successful in reducing ground vibration transmission while addressing issues of instability and enhancing vibration isolation efficiency. In PLAXIS3D, a dynamic numerical model is developed, and the results are validated against available solutions. Then, an optimized design technique for wave barriers is developed, and explore the effect of layered soil on vibration isolation effectiveness of hollow pipes.

An experimental study on vibration isolation by open and in-filled trenches

Abstract The mitigation of vibrations due to a harmonic load induced by a mechanical oscillator is studied experimentally. The vertical components of soil particle velocities are measured (via geophones) at different locations apart from the source, where various frequencies (30–70 Hz) are generated. For normal conditions where no mitigation means are used, it is found that the measured peak particle velocities are proportional to the excitation frequencies. The mitigation effect of constructing an active (near source) open (0.4 m wide × 3 m long × 2 m deep) trench barrier is also studied. The measurements revealed velocity increase at the points in front of the trench due to the reflected waves. This increase is proportional to the vibration frequency. Although the presence of the barrier greatly reduced the peak particle velocities beyond it, it is found that the efficiency of screening is more pronounced at high vibration frequencies. Increased and fluctuated trends of the amplitude reduction ratio are reported away from the barrier. It is realized that passive (near target) screening is less effective for all frequencies except at 30 Hz. Active and passive trenches, filled with native soil–rubber mixture at various ratios (20–40% rubber), are also considered. The rubber material is in a form of tire chips purchased from the Unit of Recycling Scrap Tires in Al-Diwaniyah Tires Factory. Although the in-filled trenches are less effective in screening the vibrations, similar trends and behavior to the open trenches are noted. It is found that the mitigation efficacy is increased with the rubber content.

The effect of viscosity of saturated soil on the surface wave attenuation by periodic in-filled trench

Investigations on the ambient vibration reduction by periodic wave barriers have been received more and more attention in recent years. However, the role of energy dissipation caused by the viscosity of soil is usually ignored in most of the previous studies. The surface wave attenuation in saturated viscoelastic soil by periodic in-filled trench is investigated in this study. Firstly, the constitutive model of saturated viscoelastic soil is constructed by introducing Kelvin viscoelastic model into the Biot's theory. Secondly, the complex band structure of surface waves propagating in periodic in-filled trench is calculated. A finite model for analyzing ambient vibration isolation is built, and the responses of the site under external excitation are numerically solved both in frequency domain and time domain. The roles of the viscosity of soil and the periodic barrier in the surface wave attenuation are comprehensively discussed, and some findings are obtained. Soil's viscosity reinforces the attenuation when the frequencies of surface waves fall in the attenuation zone. However, the contribution of the viscosity is not obvious. Contrary to the attenuation zone, soil's viscosity plays a key role in the attenuation when the frequencies of surface waves are out of the attenuation zone.

Performance of Open and In-Filled (Geofoam) Trenches in Mitigating Ground-Borne Vibrations Induced by Impact Loading

The open or in-filled trenches are often used in engineering practice to mitigate ground vibration induced by different types of vibration sources. A novel approach which is considering the effect of Rayleigh wavelength on the efficiency of open and in-filled trenches coupled with regular specific normalized dimensions was implemented in this study. While impact loading is a very common type of loading (in, e.g., machine foundations, driven pile installation), it was rarely studied in the past. The loading is selected to consist of 12 impact pulses. In this study, it was shown that Rayleigh wavelength controls the effect of trench-normalized dimensions on its performance, and therefore, studying the trench effectiveness based only on its normalized dimensions is a limited assumption. For open trenches, the depth of trench is the key parameter controlling its efficiency, while its width does not have a significant effect except for shallow trenches (normalized width of less than 0.7) in the condition of low Rayleigh wavelength (2.0 m). Also, it was shown that the trench should be installed at a normalized distance of at least 1.0. Furthermore, the numerical results revealed that the effect of the normalized width of the geofoam trench on its efficiency for Rayleigh wavelength {lambda }_{R}=2.0 , mathrm{m} was more than that for {lambda }_{R}=8.0 , mathrm{m}. Also, several graphs for the design of geofoam trenches under different Rayleigh wavelengths were proposed in this study, which could be useful in practice.

Vibration Isolation of a Rubber-Concrete Alternating Superposition In-Filled Trench for Train-Induced Environmental Vibration Based on 2.5D Indirect Boundary Element Method

A new train-induced vibration isolation measure of rubber-concrete alternating superposition in-filled trench is presented in this paper. For analyzing the vibration isolation effect of the new measure, this paper establishes a 2.5D train-track-layered foundation-filled trench model to analyze the dynamics of track and layered foundation with the in-filled trench. The correctness of the model is verified by using the measured data of the Sweden X-2000 high-speed train. The vibration isolation effect of the rubber-concrete alternating superposition in-filled trench is calculated by using the actual soft soil foundation parameters of the X-2000 high-speed train, and the vibration isolation effect is also compared with that of the empty trench, rubber in-filled trench, and concrete in-filled trench. The results show that the vibration isolation effect of the rubber-concrete alternating superposition in-filled trench proposed in this paper is better than that of the C30 concrete in-filled trench, especially the impact on displacement. Compared with low-frequency vibrations generated by the lower train speed, the rubber-concrete alternating superposition in-filled trench has a better vibration isolation effect on high-frequency vibrations caused by higher-speed trains. The rubber-concrete alternately superposition in-filled trench has the frequency band characteristics of elastic waves. Elastic waves in the passband frequency range can propagate without attenuation, while the elastic waves in the forbidden frequency range will be filtered out.

Estimation and prediction of screening efficiency of Sand Crumb Rubber (SCR) mix infill trench

ABSTRACT The present study investigates the efficiency of using sand crumb rubber mixture for vibration isolation and its prediction using machine learning. Safe disposal of waste rubber from tire industries is a matter of concern due to its detrimental effects. A two-dimensional finite element (FE) analysis was performed in ABAQUS, considering a strip foundation as the source of vibration. The effectiveness of the screening was evaluated by calculating the Amplitude Reduction Factor (Arf ) for open and infilled trench (OT and IFT) for different trench geometry (distance from the source, depth and width). In previous studies, modelling such screening problems has mostly been accomplished through regression models. The present study explored the Support Vector Regression (SVR) model since machine learning excels in modelling complex behaviours. The SVR model's optimum parameters were successfully determined by performing a grid search and selecting the best model using the Preferential Ranking Organization Method for Enrichment Evaluation (PROMETHEE) technique.