Trench Barrier Research Articles

An experimental investigation of the effect of barrier trench on vibration propagation on a laboratory scale model

Vibration waves caused by construction or mining operations may cause damage to nearby structures or sensitive machinery and equipment. Some measures are implemented to eliminate or reduce this negative environmental effect of vibration. The barrier trench, one of these methods, aims to reduce the vibration by creating a suitable barrier between the structure and the vibration source on the ground. In this study, the effect of trench depth and distance from the source on vibration waves was simulated with a designed laboratory-scale test set-up to determine the effective parameters in barrier trench use. In addition, the effects of the superimposition of the source vibration wave with the reflected and refracted vibration waves from the trench, which has not been previously discussed in the literature, were also investigated. A laboratory scale gypsum-plaster block with dimensions of 200 cm × 90 cm x 70 cm was prepared and a Schmidt hammer was used as the impact energy source to generate vibration throughout the gypsum block. A trench barrier was opened at different depths on the test block and 588 vibration recordings were taken by the vibration monitor in different locations of the designed set-up. Statistical analyses were performed using vibration measurement results, trench source distance, and trench depths. As a result, vibration estimation equations depending on trench depth and the distance between the vibration source point and the trench were developed and how the presence of trench affects vibration propagation is revealed. It was found that vibrations increase due to the superposition of the source and reflected waves in front of the barrier trench. As the barrier depth increases, it is understood that the vibrations emanating from the near-surface vibration energy source are better blocked by the barrier. Thus, this study provides fundamental information on designing barrier trenches to avoid adverse effects of vibrations.

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 mitigation by periodic wave barriers under a moving load: theoretical analysis, numerical simulation and experimental validation.

Periodic wave barriers (PWB) open a new window for vibration mitigation. However, the Doppler effect is rarely considered in most of the previous investigations on the control of ambient vibration induced by moving loads. This article reveals the significance of the speed and frequency of moving loads on surface waves, and improves the design method of PWB for ambient vibration reduction and isolation. First, the theoretical expression of the main frequency band of surface waves propagating in an elastic half-space caused by a moving load was obtained. Comparisons with the numerical results under three different types of traffic loads were also conducted and good agreement was found. Second, the theoretical expression and numerical results were verified by experimental studies. Some inherent properties of wave propagation caused by a moving load in an elastic half-space were also revealed. Third, two kinds of PWBs, i.e. periodic empty trench barrier and periodic pile barrier, were introduced to mitigate wave propagation. It has been confirmed that if the attenuation zones of PWB match the target frequency bands given by the theoretical expression, good vibration mitigation can be achieved. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.

Active trench barrier RC-IGBT with pinch-off and carrier accumulation effects

Active trench barrier RC-IGBT with pinch-off and carrier accumulation effects

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.

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.

Active isolation tests of metamaterial-based barriers and foundation

This study investigates the performance of novel metamaterial-based barriers and foundation on mitigating waves transmitting from a vibrational source to the surrounding soil. An active isolation system is a wave barrier built close to the vibration source to reduce the wave radiating from the source of vibration on the structure to surrounding soil. This research reports the efficacy of the proposed isolation system using an active excitation field test, thereby expanding the applicability of such wave barriers beyond passive isolation. The test barrier is a trench barrier infilled with a layered periodic metamaterial that is composed of alternating layers of polyurethane and reinforced concrete (RC). Tests are also conducted on an empty trench for comparison. A mobile shaker mounted on top of a steel frame is utilized to simulate an active vibration source. By mechanically reorienting the shaker, active isolation tests can be conducted in all three directions (vertical, horizontal inline, and horizontal crossline). Motions on the ground surface, periodic barrier, foundation, and steel frame are monitored using three-dimensional (3D) geophones and 3D accelerometers. The effects of the barrier length, the infilled material, and the total number of barriers on the isolation behavior at various exciting frequencies, and excitation directions are investigated. Tests also include the scenario where the wave barrier is used along with a metamaterial-based periodic foundation. Experimental studies show that vibrations generated from the shaker mounted on top of the steel frame are effectively restrained by a metamaterial-based foundation. The performance of the periodic barriers is better than that of an empty trench within certain frequency ranges. The wave isolation performance is enhanced with the increasing barrier length. This research provides the benchmark for the future design of periodic barriers and periodic foundations in buildings or other vibration-sensitive facilities.

Research on the effect of the moving water table on passive isolation effectiveness using a multiple open trench barrier

Research on the effect of the moving water table on passive isolation effectiveness using a multiple open trench barrier

Influence of Geometrical Dimensions on Negative Differential Resistance in Silicon Based Trench MOS Barrier Schottky Diode

In this paper, ISE-TCAD, a device simulation software, is used to carry out simulation experiments on silicon-based trench MOS Schottky (TMBS) diodes with different trench dimensions under the condition of forward biases and obtain a series of experiment data associated with the negative resistance. Simulation results show that TMBS diodes under forward biases produce the negative resistance effect. The negative resistance effect intensifies linearly with the increase of mesa width and mitigates wavily with the increase of trench depth. The coupling effect of trench oxidization layer on electric field attenuates the change in device field strength, leading to the fact that TMBS devices present a weaker negative resistance effect than trench barrier Schottky (TBS) diodes which have the same parameters, but are free of oxidization layer. The study result provides a feasible basis for the effective application of TMBS negative resistance features to the design and production of corresponding semiconductor devices and circuits.

A Novel Self-Controlled Double Trench Gate Snapback Free Reverse-Conducting IGBT With a Built-in Trench Barrier Diode

A novel double gate snap-back free reverse-conducting insulated-gate bipolar transistor (RC-IGBT) is proposed in this article, which merges a trench field stop IGBT and a trench barrier diode in a monolithic device. The backside n-channel works at weak inversion mode in forward conduction state and can be automatically turned into strong inversion mode in the reverse conduction state. Therefore, bidirectional conduction capability with snapback free characteristics is achieved in the novel RC-IGBT. Performance comparison with conventional RC-IGBT is carried out based on Sentaurus device simulations, the results show that the novel RC-IGBT device in this article exhibits excellent overall performance in both IGBT and diode modes, the reverse recovery performance is significantly improved owing to the topside trench barrier structure and backside self-controlled carrier injection, compared to the conventional RC-IGBT, the proposed device demonstrates 32% lower ${I}_{\text {rrm}}$ and 63% lower ${t}_{\text {rr}}$ .

Effects of water table on ground-borne vibration screening effectiveness by using open trenches

The seasonal variations in groundwater table would significantly change the dynamic responses of the ground and the screening performances of wave barriers. This paper develops a two-dimensional finite element model based on COMSOL to describe the propagation of waves in a layered ground with open trenches. This layered ground is modelled as a dry layer resting on a saturated half-space. The influence of the moving groundwater table on isolation efficiency of barriers is then investigated, considering the infiltrated water in trenches. The effects of soil hydraulic properties and geometrical parameters of the trench are also analyzed respectively. Results show that a low value of the permeability coefficient of saturated half-space may have a significantly detrimental effect on the screening performance due to the low frequency behaviors of the medium. Placing a trench in vibration-strengthening (weakening) zones results in a better (worse) isolation effect, and with a critical water table (Hw,c), increasing trench depth and width can hardly achieve a satisfactory screening efficiency (75% reduction) due to the occurrence of resonance in the dry layer. In addition, a multiple trench isolation system is simulated in the condition of high water levels and its shielding performance is compared to the single trench barrier. A triple trench barrier is found to be a preferred alternative because it can achieve a much better screening efficiency. Specially for Hw,c, a multiple trench barrier can effectively eliminate the adverse effect of the resonance and achieve more than 75% reduction of ground vibration.

Vibration isolation effect study of in-filled trench barriers to train-induced environmental vibrations

An in-filled trench barrier is usually used to reduce the damages from train-induced environmental vibrations. To find the vibration isolation effect of an in-filled trench barrier, this paper analyses the reflection coefficients and transmission coefficients of the Rayleigh wave at the interface between in-filled trenches and the soil. In our calculation formulas of ground vibrations, a single point and a single frequency excitation, as well as multi-point and multi-frequency excitation, are simultaneously derived in a soil-in-filled-trench system.Using these formulas and a numerical analysis, the effects of an in-filled trench barrier on the environmental vibrations induced by running trains are analyzed. The results show that the reflection coefficients increase, while the transmission coefficients decrease, with the density and elastic modulus of the in-filled material. The vibration isolation effect is clearly better than that without trenches. In a certain width range, the transmission coefficient and vertical acceleration levels decrease with the increase of trench width. The influences of the transmission coefficient and the vibration isolation effects are not clear with the trenches’ depth variation. The vertical vibrations of the ground pick-up point are all smaller than those without in-filled trenches.

A novel low turnoff loss carrier stored SOI LIGBT with trench gate barrier

A novel low turnoff loss carrier stored (CS) silicon-on-insulator (SOI) lateral insulated gate bipolar transistor (LIGBT) with trench gate barrier (CS SOI TGLIGBT) is proposed. The proposed CS SOI TGLIGBT features a trench gate inserted between the pwell and n-drift. Firstly, the trench gate acts as a hole barrier to prevent the hole from injecting directly into pwell in the on-state, which introduces carrier stored effect and realizes a uniform carriers distribution in the n-drift region, resulting in a decrease of the on-state voltage drop (Von). Secondly, due to the carrier stored effect and the assisted depleted effect induced by the trench gate, large number of carriers can be quickly removed at the initial turnoff process, leading to a decrease of turnoff loss (Eoff). The influences of gate trench barrier on Von and Eoff are investigated. Simulation results show that the proposed CS SOI TGLIGBT can achieve a 59% lower Eoff compared with the conventional SOI trench gate LIGBT at the same Von of 1.15 V.

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.

Effect of the trench shape on the electrical properties of silicon based trench barrier schottky diode

With the globally enhancing demand for the energy saving and environmental protection of electronic products, the requirement for Schottky diode which is widely used in electronic products becomes higher and higher. The trench metal-oxide-semiconductor barrier Schottky (TMBS) diode is more and more favored because of its excellent performance. The shape of the trench plays an important role in determining the electrical properties of the Schottky diode. However, there is no intensive study on this point. In this study, we propose two novel trench structures, i. e., filleted corner trench and ladder trench. By performing the simulation with Medici, it is found that compared with the traditional trench TMBS diode, the filleted corner trench TMBS diode has a breakdown voltage with 15.8% increase under the conditions of the same leakage current and the forward turn-on voltage. Also, the ladder trench TMBS diode can reduce the leakage current by 35%, while have a breakdown voltage not smaller than the right angle trench TMBS and a forward turn-on voltage only a little bit higher than the right angle trench TMBS.

Superconducting State of a Disk with a Pentagonal/Hexagonal Trench/Barrier

We study the influence of a pentagonal (hexagonal) trench or barrier on the superconducting properties of a perforated disk. Effects associated to the pinning (anti-pinning) force of the central hole and the trench (barrier) and the interplay between the boundary conditions and the shape of the inner defects on the vortex configuration are studied for a thin disk. Also, we considered two cases for the value of the order parameter at the surface. The first one is ψ s ≠0; this is the usual supercondutor/vacuum interface, for which the deGennes parameter is b→∞. The second one is ψ s =0, which is the surface of the sample in a complete normal state, simulated by b=0. The vorticity, Gibbs free energy, magnetic induction, supercurrent density, magnetization and Cooper pairs density as a function of the external magnetic field are calculated. We show that in our sample new phenomena are possible due to the competing interactions of the boundary and the geometry of the sample and the added geometry of the nanoengineered trench and barrier.

Physical exclusion of adult click beetles from wheat with an exclusion trench

Click beetles, the adult stage of wireworms, will enter fields of their preferred hosts (i.e., grasses, pasture, and cereals) from various reservoir habitats, and lay eggs which give rise to wireworm problems in subsequent years. To prevent click beetles, Agriotes obscurus, from immigrating into fields, a portable trench barrier composed of an extruded, PVC plastic trough was evaluated in 2001 in Agassiz, British Columbia, Canada. Plots of wheat or bare ground that were surrounded by trenches had significantly lower numbers of males in pheromone traps and females in pitfall traps relative to non-trenched plots. Exclusion was more pronounced in the first part of the study (about 75 % reduction) than later in the study (30–42 %), likely due to gradual within plot emergence of overwintered beetles and/or flight activity. The potential for use of exclusion devices for click beetle control and future directions for research are discussed.

Effects of open trench siding on vibration-screening effectiveness using the two-dimensional boundary element method

The two-dimensional boundary element method in frequency domain is used to investigate the screening effectiveness of the open trench–wall barrier system on reducing vibration generated by a footing. Sheet piles or diaphragm walls are on both sides of the open trench as a vibration barrier in this study. The results showed that screening effectiveness of the open trench without siding is greater than that of the open trench–wall barrier system, which is essential for stabilizing the excavation surface in practice. The trench depth of the barrier system appears to govern the screening efficiency of the barrier, and increase in depth results in better vibration-screening effectiveness. The influence of the open trench width, the embedded length of the trench wall and the distance between the vibration source and the barrier are proven to be insignificant. The screening effectiveness of an open trench barrier with walls increases with the frequency of the vibration.

The effectiveness of wave barriers on the dynamic stiffness coefficients of foundations using boundary element method

A comprehensive numerical investigation has been carried out to indicate the influence of wave barriers on the complex dynamic stiffness coefficients of the surface supported foundations under dynamic loads. In the considered problems the underground is regarded as an elastic homogeneous half-space and as a layer on the top of a rigid bedrock. The results of the present numerical simulation are obtained by using the substructure approach in the frequency domain which is formulated on basis of the boundary element method (BEM). The validations of the numerical results are shown through comparison with published numerical data. The results point out that using an open trench barrier with appropriate distance surrounding the vibration source, a notable reduction level can be achieved.

Three-dimensional modelling of train-track and sub-soil analysis for surface vibrations due to moving loads

Two mathematical models and numerical techniques for solving problems associated with the wave propagation in a track and an underlying soil due to passing trains are presented and compared. For the analysis, the thin layer method/flexible volume method (TLM/FVM) and the boundary element method (BEM) are employed to investigate the three-dimensional dynamic response of the free field nearby railway lines induced by the moving loads acting on the surface of a homogeneous or layered half-space. Particular interest is paid to influence of the mechanical properties of the railway track configuration on the vibrations covering surface propagation. A common feature of all simulation models is the application of the sub-structuring approach in the frequency domain. The results of the present numerical simulation are initially compared to an analytical and other numerical solutions. A comprehensive numerical investigations have been carried out to indicate the influence of different parameters on the amplitude reduction due to presence of an open trench. The results point out that using an open trench barrier with appropriate geometrical properties, a notable reduction level can be achieved.