Open Trench Research Articles

Study on the Application of Vibration Isolation by Using a Trench in Frame Structures

An isolation trench is a simple and effective method to isolate structural vibrations originating from sources of vibration other than earthquakes (machines, traffic, explosions, etc.); however, there is still not a conclusive depth of the isolation trench for frame structures. To investigate the isolation effect of a trench in the frame structure designed for ground vibration, both a field test and finite element analysis were conducted to analyze the reduced effect of the vibration. The vibration reduction analysis was based on the dynamic equation and wave theory. Considering the vibration control of an industrial plant frame, a soil-trench-building finite element model was built to analyze the vibration characteristics of the floor before and after the open isolation trench structure was used. According to the model, a dynamic test was carried out on the frame structure to assess the effect of the vibration reduction by introducing the trench. The results showed that the depth of the trench was the dominating factor in vibration isolation. When the depth of the trench reached 1~1.3 times the wavelength of the Rayleigh wave, the damping effect was the strongest. the width of the trench has little effect on the vibration isolation efficiency, and the trench must be maintained at a certain distance from the building to ensure the vibration damping efficiency. The vibration of each floor was obviously reduced after the trench was built. The vibration damping effect of the trench was significant.

RUA BARÃO RODRIGUES MENDES, RECIFE, PE: MEMORIES OF ITS JOURNEY FROM THE FROM THE 17TH TO THE 21ST CENTURY

This is an archaeological study based on the archaeological monitoring of the works for the embedding of the electrical network and data about Recife, certainly the oldest area of occupation in that city. According to the provisions of the Project, each street was treated as an archaeological site. Depending on the objectives of engineering, the open pits in the streets, sometimes long trenches, whose width of 40, 60 and sometimes even 80 cm, provided windows facing the time in which the streets were formed, were modified, and the construction techniques and materials varied. Based on the study of the open trenches, we sought to identify each ancient structure located in terms of its chronology and context. The results of the archaeological monitoring of the works also made it possible to document the process of expansion of the space occupied by the city, the construction of the mainland taken from the waters, the rivers, and the sea.

RUA BARÃO RODRIGUES MENDES, RECIFE, PE: MEMORIES OF ITS JOURNEY FROM THE FROM THE 17TH TO THE 21ST CENTURY

This is an archaeological study based on the archaeological monitoring of the works for the embedding of the electrical network and data about Recife, certainly the oldest area of occupation in that city. According to the provisions of the Project, each street was treated as an archaeological site. Depending on the objectives of engineering, the open pits in the streets, sometimes long trenches, whose width of 40, 60 and sometimes even 80 cm, provided windows facing the time in which the streets were formed, were modified, and the construction techniques and materials varied. Based on the study of the open trenches, we sought to identify each ancient structure located in terms of its chronology and context. The results of the archaeological monitoring of the works also made it possible to document the process of expansion of the space occupied by the city, the construction of the mainland taken from the waters, the rivers, and the sea.

Time-domain analysis for the scattering of plane elastic waves in half-space with an open trench

In this paper, the scattering and vibration isolation of elastic waves from the open trench are analyzed and discussed in the time domain using the scaled boundary finite element method (SBFEM). Based on the theory of soil-structure interaction, the site with an open trench is decomposed into a near-field system and an infinite far-field system. The quadtree domain decomposition technique is employed for SBFEM mesh discretization of the near-field. The far-field is rigorously modeled by the displacement unit impulse response matrix. The obliquely plane elastic wave from the far-field is converted into a traction force acting on the near/far-field boundary. The time-space domain numerical model is established for elastic wave propagation in half-space with an open trench. Finally, through numerical examples to verify the effectiveness of the method of this paper, and parametric analyze the effect law of the incidence angle and the trench depth, etc., on the vibration isolation performance.

Dynamic Analysis for High-Speed Locomotive in Distinct Depths

The study uses coupled finite or boundary element models expressed in terms of the axial wavenumber. It is found to be important to include the track in the model as this determines how the load is distributed at the soil’s surface, which significantly affects the insertion loss of the barrier. Calculations are presented for a range of typical layered grounds in which the depth of the upper soil layer is varied. Variations in the width and depth of the trench or barrier are also considered. The results show that in all ground conditions considered, the notional rectangular open trench performs best.

Relationships between soil properties and species establishment in the restoration of mined soils in the Cerrado biome.

Restoring the ecosystems of the Cerrado biome is challenging considering the diversity of phytophysiognomies present in the biome, some of which are composed of species from different strata (herbaceous, shrubby, and arboreal), which increases the complexity of restructuring the floristic composition. Other factors was involved, such as soil quality, which directly influences the success of restoration, water storage, and nutrients, the financial costs, and a slow ecological process, due to the adverse circumstances found in the area. be restored. The strong anthropogenic interventions by mining processes reduce dramatically the physical and nutritional composition of the soil. We studied two restoration areas in Paracatu, Brazil, to examine their edaphic conditions six years after mining activities ceased and relate them to the status of the restoration process. In 2009, a Cerrado restoration were established in an area previously explored for gravel extraction. Plants were sampled and identified in 11 transects along the planting lines. The diameter base (DB) and total height (HT) were measured. The physical/chemical quality of the soil substrate was determined using a collection of samples in open trenches at four types of points: Cerrado (TC); dead plant pits (TM); seedling pits having living individuals of the most abundant species (TT); and those of the second-most abundant species (TE). Cecropia pachystachya Trécul and Tapirira guianensis Aubl. were most abundant and demonstrated the potential to thrive in areas degraded by mining having low mortality rates and growth at relatively DB and HT. The physical quality indicators in the gravel pits were not limiting, indicating that substrate preparation was efficient in this regard. The organic matter content in TM, TT, and TE was low in comparison to that of TC, and the chemical conditions in the TE pit substrates were similar to those in TM pits, suggesting C. pachystachya is a species with good plasticity, whereas T. guianensis is present in pits with higher levels of phosphorus.

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.

Numerical evaluation of tire chips–filled trench barriers for effective vibration isolation

Ground vibrations induced by man-made sources like vibrating machinery, vehicular movement, traffic, construction activities involving pile driving, blasting, dynamic compaction, etc., are rising rapidly and may disrupt nearby sensitive equipment, distress, and damage sub-structures. Therefore, vibration isolation is necessary to mitigate ground-borne vibrations with suitable techniques in the present-day context. Trench barriers are one of the most efficient techniques when the other isolation techniques are inefficient at the source. Although the open trench barriers are the most efficient, their stability is still a significant concern. Hence, these trenches are generally filled with suitable absorbing materials such as sawdust, geofoam, and concrete. The present study has attempted to explore the feasibility of using shredded tire chips as an infill material by evaluating their performance using the finite element method. The performance of tire chips–filled trench barriers predicted using FE analysis is also compared with the performance of other common infill materials such as sawdust and geofoam. Numerical studies show that the vibration isolation efficiency and their performance are highly sensitive to the shear wave velocity of the soil and infill material density for infill trenches. The key findings of the study suggest that shredded tire chips can also be used as an infill material in trenches for reducing ground-borne vibrations, and its performance is comparable with geofoam-filled trenches.

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.

Analysis of the scattering of plane SH waves by multiple open trenches and its vibration isolation performance

Analysis of the scattering of plane SH waves by multiple open trenches and its vibration isolation performance

Major rebuilding and reconstruction of sewer networks in Samara

In Samara, capital rebuilding and reconstruction of sewer networks are carried out using modern trenchless methods of restoration (renovation) and rehabilitation of pipelines, as well as using the traditional method, which consists in replacing pipes in the repaired section of the pipeline network using an open trench mining method. A limited time is allotted to carry out work to eliminate an accident on the sewer network, therefore, the choice of technology for cleaning the pipeline and (or) its restoration (renovation) must be carried out promptly on the basis of pre-developed technological maps, taking into account information and documents from the information model of this section of the sewer network .

Novel Open Trench Techniques in Mitigating Ground-Borne Vibrations due to Traffic under a Wide Range of Ground Conditions

This study proposes the novel geometrical design of open trenches in contrast to the traditional rectangular type of open trench, in order to improve the efficiency in mitigating the traffic-induced ground vibrations. The novel geometric design involves the variation in cross-sectional shape, cross-sectional area, sidewall inclination, depth of trenches, and the number of trenches. In addition, the efficiency of the multirow trenches with shallower depths, in contrast to the single-row deep trench, is also assessed for further mitigating the low-frequency ground vibrations. It is argued that these novel open trenches would change the wave propagation direction while also weakening the wave propagation capability in the original direction. A two-dimensional (2D) finite-element study is performed to investigate the isolation efficiency of novel open trench techniques with varying cross sections in a linear elastic, isotropic, and homogeneous half-space. A steady-state vertical harmonic excitation of the ground surface was simulated. The numerical results show that compared with the rectangular open trench, the part of the area behind the new cross section trench has better isolation efficiency, Cross section 6 seems to be the most efficient of the six cross sections, and the isolation efficiency is improved by nearly 10.2% compared. Increasing the cross-sectional area could not effectively improve the isolation efficiency of the open trenches. Selection of inclination of the hypotenuse to an appropriate angle, increasing the number and depth of open trenches could improve the isolation efficiency. The vibration isolation performance of the trenches in the soft soil was better than the stiff soil. Besides, an excessively high groundwater table is usually detrimental to the isolation efficiency of the trenches.

INFLUENTIAL FACTORS AFFECTING THE DEPTH OF EXCAVATED TRENCH IN UNSATURATED SOILS DUE TO NONLINEAR SUCTION DISTRIBUTION

Depth of an excavated trench plays a vital role on stability as well as economic efficency of an open trench. As design and analysis excavation construction method, selection of an appropriate excavated depth value of a trench without support structures is necessary. In practice, excavated trench is usually located above ground water table or under unsaturated soil condition. Therefore, the depth of unsupported trench is significantly affected by unsaturated soil properties, especially suction distribution and physical properties of soil as well. To date, there have been a few theories and research works reported on the method of determining a suitable depth of a trench under unsaturated condition. However, previous works tend to assume that the distribution of soil suction is either constant or linear with depth; as a result of this assumption, the designed results are often overestimated compared to practical results. In this paper, the effect of nonlinear distribution of suction was taken into account to propose an equation to estimate the depth of an excavated trench without support structures. Eventually, an example of numerical computation was executed to figure out the factors that affect the depth of excavated trend considering non linear suction distribution of unsaturated soils.

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.

A case study on the determination of the excavated trench depth in unsaturated soil constructed by trench method without supporting structures

Together with the excavated width, the depth of trench play avital role in stability as well as economics effectiveness of a trenchconstructed by open trench method. It is widely recognized that a steeperangle of an open trench, a smaller amount the excavated soil required;however, the trench is unstable. In this case, an external supporting structuresystem is obliged to prevent the trench from falling into the excavation zone.In addition, an open trench is normally located above the water table, henceunder unsaturated condition. One of the most important characteristics ofunsaturated soil is negative pore water pressure which brings about thematric suction, higher negative pore water pressure, higher matric suction;consequently, higher shear strength of soil. On the other hand, there is a fewtheories and research works have been reported on the method ofdetermining a suitable depth of a trench under unsaturated condition.Previous works tend to assume that the distribution of matric suction iseither constant or linear with depth; as a result of this, the designed resultsare often overestimated compared to practical results. In this paper, theeffect of distribution of matric suction was taken into account to propose anequation to estimate the depth of a trench that can be applied withoutsupporting structure. Finally, an example of numerical calculation of a depthof the open trench was described.

Determination of the maximum traction force of the screw working body when piercing the soil

Laying of gas distribution pipelines, water mains, sewerage systems, power cables and communication cables is performed both by laying it in an open trench and by trenchless methods.

Deep-seated gravitational slope deformation involving glacial evidence in the Rodoretto Valley (NW Alps)

ABSTRACT The Rodoretto Valley (about 25 km2) (Western Alps, NW Italy) shaped in the metamorphic bedrock, covered by Quaternary sediments, is involved in significant deep-seated gravitational slope deformation (DSGSD). A detailed field survey revealed several morpho-structures typically related to DSGSD phenomena (open fractures, doubled ridges, scarps, trenches, counterscarps and bulging reliefs) and other significant gravitational morphologies, here defined as gravitational valleys, not previously reported in geological literature.Fieldwork also allowed us to distinguish various types of glacial sediments, reconstructing the supply basins, relatively dating glacialism to LGM and Late Glacial-Holocene and evaluating their gravitational dislocation. The wide extension of the area characterized by DSGSD and incredibly big dimension of single morpho-structures are the most important recognized features. In particular, we observed that entire sectors of the study area were gravitatively conditioned not only by local slid along the Rodoretto slopes but also by movement towards the nearby and deeper Germanasca Valley.

Finite Element Analysis of Wave Barriers Used to Reduce Train Induced Vibrations

The finite element method is used to simulate the soil vibration behavior due to the Basrah-Baghdad passenger train and its effect on a targeted building in the Al-Ma'qal quarter, Basrah governorate. Three-dimensional dynamic elastic analyses are performed to calculate the particle velocities for a train speed of 120 km/hr. The effectiveness of screening using active (10 m long) open trench barriers with variable depth (2 m - 5 m) and width (0.4 m - 0.8 m), is being studied. For a given trench width (0.4 m), the results of the parametric study revealed a considerable effect of trench depth where the screening capability near the trench is increased by (10.4 %, 26.1 %, 36.3 %) due to a (50 %, 100 %, 150 %) increase in depth. The results are less sensitive to the variation in trench width. The screening capability of a double open (0.4 m × 10 m × 2 m) trench system was also investigated, where a mitigation improvement of (36.4 %) was achieved. The vibration mitigation using single and double trench systems, filled with (40 %) rubber content mixture, was also analyzed. It is concluded that using the additional passive trench increases the mitigation of the single system by around 19.1 %. An important finding is that the (40 % rubber + 60 % native cohesive soil) mixture proved to be a good filling material, since the infilled-trench systems produced comparable screening ratios to the open systems, where (97.7 %) and (85.4 %) were accomplished for the single and double systems, respectively.

A full-scale field study on mitigation of environmental ground vibrations by using open trenches

Environmental ground vibrations induced by construction operations, machine foundations, vehicular and railway traffic may cause discomfort to the dwellers in their immediate vicinity and malfunctioning of sensitive equipment in nearby structures. Associated with technological development and rapid industrialization, undesired vibrations around the residential areas have increased. Hence, the isolation of those vibrations has become an important issue. Open trenches are mainly employed as wave barriers in mitigation of undesired vibrations. Recent studies have focused on the parameters affecting the vibration isolation performance of open and in-filled trenches. It is stated that screening effectiveness mainly depends on the type of the vibration source and geometric dimensions of open trenches along with the local site conditions. In the present study, a series of full-scale field experiments were conducted to identify the effects of governing parameters on efficiency. The amplitudes of ground vibrations, artificially generated on the site, were measured through highly sensitive accelerometers at different test configurations. It was concluded that the frequency of vibrations had more influence than the actual depth of the barrier on screening effectiveness. Better isolation can be achieved in a region close to the trench while the effectiveness decreases at great distances. In addition, the results were compared with those of recently reported in experimental studies.