Ground Vibrational Level Research Articles

Site-Resolved Imaging of Ultracold Fermions in a Triangular-Lattice Quantum Gas Microscope

Quantum gas microscopes have expanded the capabilities of quantum simulation of Hubbard models by enabling the study of spatial spin and density correlations in square lattices. However, quantum gas microscopes have not been realized for fermionic atoms in frustrated geometries. Here, we demonstrate the single-atom resolved imaging of ultracold fermionic $^{6}$Li atoms in a triangular optical lattice with a lattice constant of 1003 nm. The optical lattice is formed by a recycled narrow-linewidth, high-power laser combined with a light sheet to allow for Raman sideband cooling on the $D_1$ line. We optically resolve single atoms on individual lattice sites using a high-resolution objective to collect scattered photons while cooling them close to the two-dimensional ground vibrational level in each lattice site. By reconstructing the lattice occupation, we measure an imaging fidelity of ~98%. Our new triangular lattice microscope platform for fermions clears the path for studying spin-spin correlations, entanglement and dynamics of geometrically frustrated Hubbard systems which are expected to exhibit exotic emergent phenomena including spin liquids and kinetic frustration.

Vulnerability assessment of building structures due to underground blasts using ANN and non-linear dynamic analysis

Building structures near the mines area are prone to blast-induced ground vibration due to underground blasting. The level of ground vibration typically quantified as Peak Particle Velocity (PPV) is used to assess the vulnerability of the buildings. However, the PPV does not take into account the dynamic characteristics of the structure. To incorporate structural response in the design and assessment process, Artificial Neural Network (ANN) was used on underground blast data from the literature to obtain the Peak Ground Acceleration (PGA). Charge weight (Q), distance from the blasting point to the monitoring point (D) and soil's elastic constant (E) were taken as input to ANN and peak ground acceleration (PGA) was the output. Safe site distance for constructing structures was determined using non-linear time history analysis of structures having periods ranging from short to long duration, incorporating soil flexibility. The main findings highlight the shortcomings of considering PPV as the sole criteria for vulnerability assessment. The structural response such as interstorey drift, and damage level and locations must be taken into account.

Research on blasting vibration effect and time-frequency characteristics of vibration signals in a road corridor at xianning nuclear power station

Drill and blast is a major method for foundation excavation in nuclear power plant engineering. For transporting heavy components to engineering construction, the blast-induced vibration of foundation excavation in a road corridor may has a great influence on new pouring mass concrete and surrounding bedrock in Xianning Nuclear Power Station, which will affect the safety of the engineering construction. So it is necessary to monitor the process of blasting excavation and put forward effective control measures on blasting vibration effect, in which the peak particle velocity (PPV) attenuation law are investigated through regression analysis of practical field data by Duvall empirical formula and the time-frequency characteristics was analyzed by wavelet transform and wavelet package decomposition. By analyzing the velocity amplitude and power spectrum density amplitude of wavelet components, it shows the blast energy of original vibration signal is mainly within the frequency below 250 Hz and has three sub-band which varies from 10 Hz to 30 Hz, from 40 Hz to70 Hz and from 75 Hz to 125 Hz, respectively. Wavelet packet analysis indicates the energy of the signal in 0-125 Hz accounts for 94.25 % of the total signal. At the same time, for the sake of ensuring the safety of road corridor, Chinese admissibility standards (GB6722-2014) of blasting-induced vibration and the constants obtained from the regression were used to establish the maximum explosive charge per delay for an acceptable ground vibration level that would not cause damage for new pouring mass concrete and bedrock in road corridor. The safety criteria of particle vibration velocity for new pouring mass concrete and bedrock in road corridor could be both set as 5 cm/s, which show the remarkable effect on blasting damage control of the new pouring mass concrete and surrounding bedrock, the results demonstrate that controlling maximum explosive charge per delay methodology can be commendably applied to road corridor to control blasting-induced vibration effects.

The significance of source-receiver interaction in the response of piled foundations to ground-borne vibration from underground railways

The numerical prediction of vibration in buildings due to underground railways involves modelling many physical phenomena. Not least of these is the dynamic soil-structure interaction that exists between the various elements of the system. The majority of existing models assume that the interaction between the railway tunnel and the building’s foundation is negligible, with the two sub-systems behaving as though they are uncoupled. This paper presents some initial results from a three-dimensional model that accounts for the through-soil coupling between a tunnel and a piled foundation. The model is based on the pipe-in-pipe model, of a circular, longitudinally invariant tunnel excited by wheel-rail roughness, coupled to a boundary-element model of the foundation using an iterative wave-scattering approach. Initial test cases, involving single piles and pile-groups, highlight new details of tunnel-pile and pile-pile interaction, as well as predicting the effect of piles on ground vibration levels.

Evaluation of blast efficiency in aggregate quarries: facts and fictions

Evaluation of blast efficiency in quarrying of aggregate stones is one of the most important decisions that should be made by quarry operators for productivity assessment. The regulatory authorities also evaluate blast efficiency for environmental safety compliance. In carrying out this task, there is usually a conflict of interests between the quarry operators and the regulatory authorities. The quarry operators wish to blast and deliver the run-off-mine (ROM) to the processing plant at the least minimum cost with little or no boulders. On the other hand, the regulatory authorities want blast operations to be carried out with minimum disturbances to the environment irrespective of their incurred costs, fragmentation distributions, and effects on further quarrying processes. This conflict of interest calls for different approaches for evaluating blast efficiency by the various interest groups. Nevertheless, there must be an established standard that considers both process efficiency and environmental safety and acceptable to all the critical stakeholders in the sector. However, many of the currently available approaches and models for evaluating blast efficiency do not include safety but production efficiency. The chosen method primarily depends on the further use of quarried products. While quarry operators may evaluate blast efficiency by counting of boulders, shovel loading rate, visual observation, fragment size distribution, and cost analysis, the regulatory authorities majorly based their judgment on the level of blast-induced ground vibration by measuring the peak particle velocity of production blasts. This paper attempts to suggest a common ground and wholistic approach for evaluating blast efficiency and make a distinction between blast efficiency and fragmentation efficiency.

Theoretical study of MgNa+ ionic system: potential energy curve, vibrational levels, dipole moments, radiative lifetimes and laser-cooling analysis

An extensive ab-initio quantum chemistry study and a discussion of the possible laser cooling and formation of the heteronuclear ionic MgNa+ molecule is presented in this paper. Our work is based on the use of non–empirical pseudo-potentials for the Mg2+ and Na+ cores, large Gaussian basis sets, parametrized l–dependent polarization potentials, and full valence configuration interaction calculations. We present here adiabatic potential energy curves of the ground and 44 low-lying excited electronic states of 1,3Σ+, 1,3Π, 1,3Δ symmetries, and their spectroscopic parameters (Re, De, Te, ωe, ωexe, and Be). Furthermore, numerous ionic – neutral avoided crossings, specially between higher adjacent electronic states of 1,3Σ+, 1,3Π symmetries, are identified and interpreted. The energy separations between these avoided crossings are also calculated. The electric dipole moment curves have been computed for a wide range of inter-nuclear distances. The vibrational energies are obtained by solving the nuclear Schrodinger equation, using the calculated potential energy curves. Thereafter, spontaneous and black-body radiation induced transition rates are calculated to obtain the ground and excited states vibrational level lifetimes. It has been observed that the lifetimes of the ground state vibrational levels are of the order of a second, while those of the excited states, mainly the 21Σ+ state, have the order of a nanosecond.

Data analysis and prediction of ground vibrations due to deep vibro-techniques

Deep vibro-techniques impart vibrations into the ground to achieve targeted improvement. One of the common geotechnical challenges of these techniques is the question of how vibration attenuates over distance and its effect on nearby structures. In this paper, ground vibration data from several deep vibro-technique projects with different vibrators are analysed. Best-fit estimates of the field data are evaluated through analytical regression, and comparisons of the field data against requirements from some standard codes of practice for admissible vibrations are made. A preliminary estimate of ground vibration levels can be obtained from the empirical relations of vibrator energy and distance. Such an assessment, when coupled with the monitoring and collection of actual field data, should enable further predictions to be more refined. In addition to analysing ground vibration data, predictions of ground vibration and comparisons of theoretical predictions against regressions of the field data are demonstrated. Average estimates of soil profile and strengths are included in the evaluations as well. Suggestions for better predictability of ground vibrations are also given. Moreover, recommendations for safe working distances from existing structures or services are made for different types of vibrators and vibro-techniques.

Analysis Of The Effect Of Blasting Pattrerns On Ground And Building Vibration Levels Around The Mine At Blasting In Pit 2 Banko West PT Bukit Asam Tbk tanjung Enim, South sumatera Province

PT Bukit AsamTbk is one of the coal mining companies in Indonesia that uses an open pit mining system. Demolition of B2-C overburden rocks at the location of electrification mining in Pit 2 Banko Barat is not economical if it is doing by ripping-dozing process so that drilling and blasting activities are carried out. After blasting activities, ground vibration will arise as an effect of the blasting. It is known that the distance of the blasting location with the residential area is at a distance of 1350-1800 m for this reason that vibration measurements must be carried out with the Blasmatet III device. Ground vibration is one of the problems that must be minimized so that the ground vibration level is in accordance with SNI 7571; 2010 did not exceed the vibration threshold that could cause damages, especially for residents. The ground vibration level can be controlled in various ways such as setting the point initiation point, setting the delay time with a higher value, planning the powder factor and finally using the Air deck method. Based on research carried out for 60 days with blasting 17 times which produces different vibrations. The vibration value used for the comparison of the effects of the blasting pattern is used in 6 data, 3 data for the Box cut blasting pattern, which are 0.52, 0.53, 0.56 and for data on the Corner cut blasting pattern which is 0.63, 0.69, 0.73. While for the comparison of data using Air deck, 6 data are used, 3 values of the results of the vibration of the water deck method are 0.73, 0.69,58 and for non-Air decks the results of the vibration are 1.17, 1.05, 0, 88. Calculation of the results of the comparison of the vibration comparison using the delay time there are 6 data used, namely 3 with a delay time of 42 & 67 with the results of vibration, namely, 0.58, 0.69, 0.73 while the delay time 42 & 109 the result of vibration is 0.50, 0.56, 0.58. Of the overall soil vibration values, settlements around the blasting area are in the safe category (PVS <3 mm / s).

Analysis of Distance On Ground Vibration at Around Residential Areas in PT Semen Padang Indarung West Sumatera Province

One of the blasting activity impact in Exsisting Pit by PT Semen Padang is producing the ground vibration. Analyzing the blasting distance needed to know the level of ground vibration. From that analysis, the actual value and prediction value of Peak Vector Sum (PVS) and value of vibration by SNI 7571 : 2010. The measuring of ground vibration level is done in Mess APN as residents settlement, wich is located as far as 611 meters from blasting location. The measurement starts by measuring the blasting geometry, the amount of drill hole, blasting distance, and ground vibration for about 13 data. Those data are processed using Shotplus-I to make the blasting design and the ground vibration level will be known by using blastmate. From the 13 data of ground vibration Mess APN that known on the distance 464 m the result of ground vibration is 1.651 mm/s while on the distance 478 the result of ground vibration is 2.382. Based on the result that can be seen there is an anomaly data, that caused the same blasting geometry treatment for rock structure on mine site. Beside, according measurement data wich are measured in Mess APN, the average value of ground vibration is 1.511 mm/s. It show that the ground ground vibration does not cause a significant impact in Mess APN as residents settlement and does not exceed the limit value of class 2 building category by SNI 7571:2010 (limit value is 3 mm/s)

The shadow effect on the ground surface due to vibration transmission from a railway tunnel

Abstract The prediction of the ground vibration transmitted from tunnels to neighbouring buildings is a vital step in the assessment of the ground-borne noise in buildings. In empirical models it is commonly assumed that the level of ground vibration reduces monotonically with the distance away from the tunnel alignment. In reality, a ‘shadow’ zone is observed above the tunnel. This is first illustrated using measurements made above an operational railway line. To understand and characterise this effect, a study has then been carried out using various simulation models. Using an analytical model for the response to a point force acting in a homogeneous full-space, it is shown that the response is principally in the form of shear waves which radiate to the side rather than compressional waves which radiate in the direction of the load. This leads to a ‘shadow’ zone forming above a certain frequency, even in the absence of a tunnel and the absence of a free ground surface. The ground surface is next introduced by considering the response of a half-space to a point force, using a semi-analytical model. This is shown to exhibit similar behaviour although with differences caused by the free ground surface. Finally, a numerical 2.5-dimensional finite element/boundary element model is used to determine the response of a half-space ground to a force acting at the bottom of a concrete tunnel. The extent of the shadow is defined as the width to the point of maximum response. This depends largely on the depth of the excitation force and the shear wave speed of the soil. Although similar features are found with or without the tunnel, the presence of the tunnel structure causes a reduction in the shadow width, and the level difference within the shadow region is slightly increased. A tunnel with a smaller diameter leads to an increase in the frequency at which a given shadow effect occurs, but the tunnel lining thickness has negligible influence. The existence of shadow effect should be taken into account when making predictions of ground vibration using empirical models.

Isolation of ground vibration induced by high speed railway by DXWIB: Field investigation

In this Technical Note, a new material (i.e., Duxseal) with high damping ratio is introduced to the wave impeding block (WIB) as an active vibration isolating barrier in the free field. To evaluate the performance of the Duxseal-WIB (DXWIB), a set of field tests are performed at three test sites of Jinan-Qingdao high-speed railway of China subjected to a moving load at a high speed of 250 km/h. Accelerations in the X-, Y-, and Z-directions are monitored at multiple distances away from the track. Characteristics of ground vibrations in both time and frequency domains are analyzed using the test data. The effectiveness of DXWIB in reducing the level of ground vibration is discussed and demonstrated by comparing with the case with traditional WIB.

High resolution vibronic state-specific dissociation of NO2+ in the 10.0-15.5 eV energy range by synchrotron double imaging photoelectron photoion coincidence.

Vacuum ultraviolet (VUV) photoionization and dissociative photoionization of NO2 in the 10.0-15.5 eV energy range have been investigated in detail by using high-resolution double imaging photoelectron photoion coincidence (i2PEPICO) at synchrotron SOLEIL. Five low-lying electronic states of the NO2+ cation, X1Σg+, a3B2, b3A2, A1A2 and B1B2, are prepared with well-resolved vibronic structures and their state-specific dissociation mechanisms are unraveled and discussed. The present experimental results clarify that except the X1Σg+ ground electronic state and the first three vibrational levels of the a3B2 electronic state, the other cationic states of NO2+ within the present energy range are totally dissociative towards the NO+(X1Σ+) + O(3P) and/or NO+(X1Σ+) + O(1D) dissociation limits. An energy barrier exists along the direct dissociation route of the a3B2 state, and the b3A2 electronic state is a quasi-bound state with a very shallow well, both of which adiabatically correlate to the NO+(X1Σ+) + O(3P) dissociation limit. The a3B2 state mainly with bending vibration excitations undergoes a non-adiabatic transition to the 23A''(3B1) repulsive state along its bending potential energy curve and then predissociates into the NO+(X1Σ+) + O(3P) products. Our experimental results firstly demonstrate that the NO+(X1Σ+, v) fragment ions produced from individual vibronic levels of the dissociative NO2+(a3B2, b3A2) states are produced at the v = 0 ground vibrational level with a high rotational population due to the excitation of the vibrational bending mode of NO2+ and the associated imparted torque upon dissociation. The slower predissociations of the A1A2 and B1B2 electronic states via their spin-orbit couplings with the repulsive 23A''(3B1) state produce the NO+(X1Σ+) and O(3P) fragments with a long vibrational progression. In addition, the B1B2 state can also undergo a radiationless transition such as internal conversion into the hot X1Σg+ state and then dissociate into the second dissociation channel correlated to the NO+(X1Σ+) and O(1D) products.

Experimental study of train-induced vibration in over-track buildings in a metro depot

Over-track buildings in Chinese metro depots have recently been designed to accommodate the rapid urbanization and massive construction of urban rail transit systems. However, train-induced vibration and noise impacts in over-track buildings need to be carefully assessed to provide comfortable working or living environments for the building's occupants. Vibration and noise measurements were carried out in a typical 28-story load-bearing wall supported residence and a 4-story steel-framed office building during train pass-by events in the Qianhai metro depot in Shenzhen, China. Measured points were set at ground level adjacent to the building support structures as well as on upper floors.Train induced noise levels were within both FTA and Chinese limits. Floor vibration levels in the low-rise building were within FTA limit but not the more stringent Chinese limit. Ground-borne vibration signals in the throat area contained high level, short duration impacts generated as cars passed over discontinuities in rails at a switch. Ground vibration levels near the columns under the low-rise building were significantly greater than at the load bearing walls of the high-rise building by 20 dB or more. Levels within the buildings near columns or walls were only 5 dB higher in the low-rise building. The low-rise building transfer structure apparently significantly reduced transmission into the building above the platform. Vertically aligned load bearing walls in the high-rise building more effectively transmitted vibration. The measured vibration reduction from floor to floor was meaningfully less than recommendations in FTA guidelines.This research enriches the database of train-induced vibration and noise in over-track buildings, provides insights into the vibration transmission process into and within over-track buildings and is of value for the design and construction for similar over-track buildings in future train depots.

Electron-Impact Dissociation of Vibrationally-Excited Molecular Hydrogen into Neutral Fragments

We present convergent close-coupling (CCC) calculations of electron-impact dissociation of vibrationally-excited molecular hydrogen into neutral fragments. This work follows from our previous results for dissociation of molecular hydrogen in the ground vibrational level [Scarlett et al., Eur. Phys. J. D 72, 34 (2018)], which were obtained from calculations performed in a spherical coordinate system. The present calculations, performed utilizing a spheroidal formulation of the molecular CCC method, reproduce the previous dissociation cross sections for the ground vibrational level, while allowing the extension to scattering on excited levels.

The effect of tunnel construction on future underground railway vibrations

This paper investigates the effect of initial tunnel construction on the future ground vibration levels generated during underground railway line operation. This is important because tunnel construction results in soil disturbance, thus inducing high soil strain levels near the tunnel lining. The resulting soil stiffness degradation impacts the future generation of ground-borne traffic vibration and it's propagation to the foundations of nearby buildings, however has never been investigated. Therefore, to address this, this work develops a novel hybrid modelling approach, consisting of a construction simulation model and an elastodynamics model. First the convergence-confinement method is used to determine the stress state induced during tunnel construction using a tunnel boring machine (TBM). Next a 2.5D FEM-PML model consisting of vehicle-track-tunnel-soil is used to predict the vibration fields induced by underground trains. To link the approaches, the soil stiffness degradation contours computed from the tunnelling simulation act as inputs for the 2.5D underground railway model. This facilitates the assessment of the effect of tunnel construction on vibration levels. It is found that railway ground-borne vibration levels are underestimated if construction effects are ignored, with discrepancies of up to 10 dB found at higher frequencies. Therefore, when estimating future vibration levels during the underground railway design stage (e.g. for subway, metro, high-speed lines … etc), tunnel construction should be considered as an operational source of uncertainty.

A different methodology to control and predict ground vibrations from mine blasting

Ground vibration prediction and control from mine blasting is a complex task involving disciplines such as geotechnical engineering, explosives engineering, and geology. Despite the importance of controlling ground vibrations, the mining industry commonly uses empirical methodologies based on concepts related to the nuclear tests era (charge weight scaling relationships). Over the past decade, attempts have been made to popularize more elaborate methodologies. These methods range from basic waveform superposition to analytical and numerical methods. Such methodologies are difficult to utilize daily because of their complexity, sometimes low accuracy (despite their sophistication), requirement for difficult to obtain parameters, and time needed to reach solutions using complex algorithms. In this paper, a different methodology to control and predict ground vibrations from blasting is presented. This methodology uses a semi-empirical approach, where the generation and propagation of ground vibration waves and the ground vibration characteristics at a point of interest are considered through the collection of a signature waveform. The methodology allows assessment of the optimum delay between charges to minimize and control ground vibration levels. A case study is included to demonstrate the benefits and the methodology in detail.

On the plate-like and layer-like response of slab foundations to ground-borne vibration

The increasing urban population is leading to the exploitation of building sites, close to surface or underground railways, with considerable levels of ground-borne vibration. An important design consideration regards the levels of perceptible vibration and/or re-radiated noise in the completed buildings. A fundamental question concerns to what extent the mass and stiffness of a building foundation influences these levels. This paper explores this question in relation to a concrete slab foundation.Previous research has explored the influence of the coupling between a thin, flexural plate and an elastic half-space on the free-surface displacements arising from surface Rayleigh waves. Here, a numerical, wave-based approach is used to model the slab foundation as an elastic layer of finite thickness, overlying the half-space. The latter is subjected to incident waves in the form of Rayleigh, P- and SV-waves. It is found that thin-plate theory alone is insufficient for modelling the slab over the full frequency range of interest, and that the assumed soil-slab boundary condition plays a significant role. Design plots are presented in order to summarise the influence of the salient dimensionless parameters, and to help guide the design of a slab foundation to achieve a specific reduction in ground vibration level.

Measurements of rail vibration in a residential building behind a wave barrier trench

The authors have previously reported on a wave barrier trench that was constructed to reduce vibration transmission from railroad to a multifamily residential building [J. Acoust. Soc. Am. 139, 2159]. The reduction in ground vibration levels due to the trench was measured in several site conditions [J. Acoust. Soc. Am. 140, 3281]. This paper extends the study with additional measurements of vibration transmission into the building and structure-borne propagation within the building.

Formation and vibrational stabilization of cold heteronuclear molecules by a single infrared pulse with time-dependent frequency

We consider the formation and vibrational stabilization of cold heteronuclear molecules using infrared nanosecond pulses. Starting with a pair of colliding cold atoms of dissimilar species, our objective is the formation of a molecule in its electronic and vibrational ground level by means of the interaction with the laser field. In order to meet this goal, we propose the employment of a single pulse with a time-dependent frequency following a predefined transition pathway. We show that the proposed scheme can efficiently form cold molecules in the vibrational ground level. Calculations are performed for a model representing the formation of LiCs molecules in the milikelvin temperature range.

A Numerical Analysis of Ground Vibration Induced by Typical Rail Corrugation of Underground Subway

A two‐step approach is used to establish a numerical prediction model to study the impact of typical rail corrugation on ground vibration from an underground subway. In the first step, a vehicle‐track‐tunnel rigid‐flexible coupling subsystem is established based on a lumped mass model dynamics and finite element analysis cosimulation method to simulate the generation of vibration. In the second step, a track‐tunnel‐soil three‐dimensional (3D) finite element subsystem is built to simulate the propagation of the vibration. The ground vibration response is obtained by applying the wheel‐rail force calculated from the first step. A section of Chengdu Metro Line 3 is studied, and the accuracy of the numerical prediction model is then verified by comparison with in‐situ measurement. Based on that, the impact of corrugation on wheel‐rail interaction and ground vibration is investigated by taking rail corrugation in typical subway sections and track geometry irregularities as system input excitation. In addition, to further analyze the sensitivity between different wavelength components in the rail corrugation samples and ground vibration, the measured rail corrugation is decomposed into five kinds with different wavelength components by filtering. The results show that the typical rail corrugation has a large impact on ground vibration response, which increases significantly in the range 8–16 Hz and 50–80 Hz, and the impact decreases with the distance from the vibration source. For typical subway rail corrugation with the significant wavelength of 125 mm and the secondary significant wavelength of 63 mm, the ground vibration response is sensitive to two wavelength components at 40–60 mm and 60–100 mm. Rail corrugation with the short wavelength of 60–100 mm significantly affects ground vibration levels.