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1

Technical safety of buildings around polish quarries against harmful seismic vibrations caused by rock blasting

Chrzan Tadeusz, Sobotka Jerzy

Inżynieria Bezpieczeństwa Obiektów Antropogenicznych

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2023

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Nr 1

53--60

EN

This paper presents the results of measurements of the elliptical distribution of seismic vibrations generated during rock blasting. The technical safety of a building in the area of seismic vibrations is determined by the vibration velocity that does not exceed the line B included in zone II of the scale of dynamic influences [SWD]. The hypothesis proved in the paper is that for both elliptical and circular distributions of the vibration velocity in rock mining with blasting material [BM] there is a directionality of the horizontal radial component Vx and the tangential component Vy of the vibration velocity. The magnitude of the components Vx and Vy of the vibration velocity at the same distance from the vibration source depends on the directional angle "α" between the line of the blast holes and the line connecting the centre of the surface of the rock block being mined with [BM] and the place of measurement. The elliptical shapes of the graphs Vx and Vy obtained during the mining of the BM of the basalt deposit, which depend on the value of the directional angle, were compared with the shape of the circular velocity graphs Vx and Vy. New correlations are given that take into account the directional angle when calculating the maximum vibration velocity values needed to determine the damage caused to a bulding by the SWD.A dynamic impact scale [SWD] for the assessment of building damage as the vibration velocity acting on the building increases is given and discussed. Vibration velocity diagrams measured during the excavation of BM rock are presented for circular distributions in accordance with theoretical predictions. A vibration velocity diagram for an elliptical distribution, inconsistent with a circular distribution, measured during the excavation of BM rock is presented. It is shown that the directionality of the horizontal radial and tangential components of vibration velocity exists for both circular and elliptical distribution of vibration velocity in rock excavation with BM. In the conclusions, for the elliptical velocity field of the vibrations, the conditions to be observed in order to be able to direct the smallest vibrations towards the built up area are given.

2

Predicting the peak particle velocity from rock blasting operations using Bayesian approach

Aladejare Adeyemi Emman, Lawal Abiodun Ismail, Onifade Moshood

Acta Geophysica

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2022

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Vol. 70, no 2

581--591

EN

Measuring the blast-induced ground vibration at blasting sites is very important, to plan and avoid adverse effects of blasting in terms of the peak particle velocity (PPV). However, the measurement of PPV often requires time, cost, and logistic commitment, which may not be economical for small-scale mining operations. This has prompted the development of numerous regression equations in the literature to estimate PPV from a relatively easier to estimate scaled distance (SD) measurement. With numerous regression equations available in the literature, there is a challenge of how to select the appropriate model for a specific blasting site, more so that rocks behave differently from site to site because of different geological processes that rocks are subjected to. This study develops a method that selects appropriate models for specific blasting sites by comparing the evidence and occurrence probability of different regression models. The appropriate model is the model with the highest evidence and occurrence probability given the available blasting site SD data. The selected model is then integrated with prior knowledge and available blasting SD data in Bayesian framework for probabilistic characterization of PPV. The SD and PPV data at the opencast coal mine, Jharia coalfield in the Dhanbad district of Jharkhand, India, is used to illustrate and validate the approach. The mean and standard deviation of simulated PPV samples from the proposed approach are 12.38 mm/s and 7.36 mm/s, respectively, which are close to the mean of 12.03 mm/s and standard deviation of 9.24 mm/s estimated from the measured PPV at the site. In addition, the probability distribution of the simulated PPV samples is consistent with the probability distribution of the measured PPV at the blasting site.

3

Experimental study of the effect of rock blasting with various cutting forms for tunnel excavation using physical model tests

An Huaming, Song Yushan, Yang Deqiang

Archives of Civil Engineering

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2021

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Vol. 67, nr 3

599--618

EN

Cutting blasting has been widely used for tunnel excavation. The cutting forms significantly influence the blasting effect. This research focuses on the study of the relationship between cutting forms and blasting effects. Similarity theory is proposed for the experimental study of the rock blasting using small models. Then four experimental modes with different cutting forms are used to study the blasting effect due to the cutting forms. The cutting depth, borehole utilization rate, fragments volume, and average fragment size are analysed. The blasting effects with various cutting forms are compared. The influences of the borehole space and the blasting delay are discussed. It is concluded that the spiral cutting form can produce more fragments and is recommend for the small section tunnel excavation.

4

Wyznaczenie pola obciążeń generowanych wybuchem wydłużonych ładunków cylindrycznych

Papliński A.

Materiały Wysokoenergetyczne

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2018

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T. 10

77--87

PL

Przedmiotem pracy jest wyznaczenie pola obciążeń generowanych w górotworze wybuchem wydłużonych ładunków cylindrycznych. Podczas prac strzałowych w otworach wiertniczych stosowane są ładunki o długościach kilkunastu metrów i większych. W związku z tym, stacjonarny rozkład pól naprężeń i przemieszczeń ustala się w obciążanym górotworze wokół otworu, w którym detonacja przemieszcza się ze stałą prędkością. W pracy przedstawione zostało stacjonarne rozwiązanie określające rozkłady ciśnienia oraz prędkości radialnej i wzdłuż osi symetrii wytwarzanych ruchomym obciążeniem przemieszczającym się wzdłuż kawerny cylindrycznej wyciętej w nieograniczonym ośrodku materialnym. Obciążany ośrodek opisywany jest modelem jednofalowym, w którym prędkość rozprzestrzeniania się małych zaburzeń określona jest wielkością modułu odkształceń objętościowych. Rozwiązanie wyznaczane jest z wykorzystaniem metody przekształceń całkowych. Przedstawiono rozwiązanie przykładowe, w którym przemieszczające się wzdłuż cylindrycznego otworu wymuszenie o stałej wielkości oddziałuje na ośrodek w określonym czasie.

EN

Dynamic load field generated in the rock mass by detonation of elongated cylindrical charges is determined. In practical blasting operations charges of dozen and more meters long are employed. Therefore, in the ambient medium around of the hole in which the charge detonates, a stationary field of stress and displacements is established. In the paper a stationary solution is presented which estimates the fields of pressure as well as of radial and axial velocity generated by a moving load propagating with constant velocity along the cylindrical hole cut in an infinite medium. The loaded medium is described by a one-wave model in which the small displacements speed is determined by the magnitude of the bulk modulus. The solution is estimated using integral transformations. A sample solution is provided, for a constant-value moving load acting on the internal surface of the hole for a given interval of time.