Efficient time–frequency approach for prediction of subway train-induced tunnel and ground vibrations

In this paper, an efficient time–frequency approach is presented for the prediction of subway train-induced tunnel and ground vibrations. The proposed approach involves two steps. In the first step, a time domain simulation of the vehicle–track subsystem is used to determine the track–tunnel interaction forces and, in the second step, the resulting forces are then applied to a 2.5 D FEM–PML model of the tunnel–soil system. There are two main aspects to the novelty and contribution of this work: First, the errors of the linearized Hertzian wheel–rail contact models in the calculation of the track–tunnel interaction forces are quantified by a comparison with the nonlinear Hertzian contact model. The results show that the relative errors are less than 2%. Second, an efficient time–frequency analysis framework is proposed, including the use of a strongly coupled model in the time domain solution and a 2.5 D FEM–PML model in the frequency–wavenumber domain solution. Finally, the accuracy and efficiency of the proposed approach are verified by comparison with a time-dependent 3 D approach, where three types of soil, i.e. soft, medium, and hard, are considered.

The LAI Coupling Associated with the M6 Luxian Earthquake in China on 16 September 2021

Periodic signals replaced noise that was found in continuous seismic data, particularly in the nighttime, from the broadband seismometer at the MVP-LAI (monitoring vibrations and perturbations in the lithosphere, atmosphere and ionosphere) system before the occurrence of the Luxian earthquake on 16 September 2021. A short distance of ~150 km between the MVP-LAI system and the epicenter of the Luxian earthquake suggests the periodic singles as promising seismo-phenomena, due to that the radius of the earthquake preparation zone is ~380 km for an M6 event. Integration of geophysical parameters, including atmospheric pressure, vertical electric field, radon concentration, groundwater level and precipitation, at the MVP-LAI system provides an excellent opportunity for studying the seismo-LAI coupling associated with the Luxian earthquake. Analytical results show that ground vibrations, atmospheric pressure and total electron content varied from ~10−3 to ~10−2 Hz before the Luxian earthquake. The seismo-LAI coupling in the relatively low frequency band (~10−3 Hz) can be referred to as the acoustic-gravity waves triggered by the amplified ground vibrations. In contrast, the seismo-LAI coupling in a relatively high frequency band (~10−2 Hz) would be caused by micro-cracks and/or the high-mode natural frequency that further drives changes of TEC due to the atmospheric resonance.

Reducing Blasting-Induced Ground Vibrations at the Velkolom Čertovy Schody-Západ Quarry

The study discusses the use of the electronic initiation system and software modeling to reduce ground vibrations induced by blasting works. The main part compares non-electric and electronic initiation systems, namely how the system-type affects the peak vector sum (PVS). The study evaluates blasting works conducted between 2011 and 2020 at the Velkolom Čertovy schody quarry. KonĘprusy limestone deposit mined from a quarry Velkolom Certovy schody belongs to one of the most significant mining locations in the Czech Republic. The main mining technology used in breaking rock mass at the Velkolom Čertovy schody quarry is blasting (namely bench blasts and overburden blasts). Blasting generates ground vibrations that affect the surroundings of the quarry. The information on ground vibrations is continuously collected at the predetermined measurement sites through a monitoring network. The network constantly monitors peak particle velocity (PPV), PVS, frequency, and other parameters. The key measurement site appears to be Prošek Dome (M15) in the Koneprusy Caves. At this measurement site, the limit value of the PVS is stipulated at 3.0 mm s-1. If this value is exceeded, it is necessary to establish measures which lead to blasting restrictions (e. g. decrease in the weight of the deck charge, bench blast rows reduction). To meet the criteria, the Velkolom Čertovy schody-západ quarry started to use the electronic initiation system (E*STAR) along with the specialized software Paradigm for vibration modeling. This study, using data collected at the measurement sites Prošek Dome (M15) and KonĘprusy No. 19, compares the PVS generated by the non-electric initiation system (Shock*Star) without modeling and by the electronic initiation system (E*STAR) with modeling. As reference years for non-electric initiation were stipulated years 2011, 2012, 2013, and for electronic initiation years 2018, 2019, and 2020. An analysis of 467 bench blasts executed at the quarry was conducted - or rather, the analysis of the PVS values collected at the pre-selected measurement sites. The analysis shows that the average value of the PVS at the measurement site Prošek Dome (M15) decreased from 2.05 mm s-1 to 1.64 mm s-1 when using the electronic initiation system with vibration modeling. The decrease in the PVS value was observed at the measurement site KonĘprusy No. 19 as well, namely from 0.48 mm s-1 to 0.31 mm s-1. In addition, significantly fewer occasions of exceeding the PVS limit value were reported at the measurement site Prošek Dome (M15), specifically from 6.7 % to 2.7 % of the blasting works conducted within the selected reference years. The study also describes fundamental principles of work with the Paradigm software. Based on the vibration analysis, parameters of the bench blasts need to be adjusted: timing, number of deck charges or rows, etc. Finally, the study summarizes the benefits of the electronic initiation system with modeling.