Generation Of High Frequency P And S Wave Energy By Rock Fracture During A Buried Explosion
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Generation Of High Frequency P And S Wave Energy By Rock Fracture During A Buried Explosion Its Effect On P S Discriminants At Low Magnitudes
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Author :
language : en
Publisher:
Release Date : 2004
Generation Of High Frequency P And S Wave Energy By Rock Fracture During A Buried Explosion Its Effect On P S Discriminants At Low Magnitudes written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.
High stresses in the source volume of an underground explosion produce a shell of crushed and fractured rock surrounding the shot point. We have modeled this process using a micro-mechanical damage mechanics in an effective medium source model to calculate the nucleation, growth, and interaction of fractures from an array of preexisting flaws. We have found that the nucleation and growth of fracture damage generates secondary seismic radiation that can be comparable in amplitude to the radiation generated by the pressure pulse itself. This secondary radiation is higher frequency than the primary radiation and can have a large shear wave component if there is a preferential orientation of the initial flaws or if there is a significant regional pre-stress field. It can be significant in the interpretation of regional discriminants that use local S phases. We have explored the scaling properties of this secondary radiation by modeling the chemical NPE explosion and US nuclear explosions in granite: HARDHAT, SHOAL, and PILEDRIVER. Finally, we have initiated work to understand the effect of frozen rock at the source point on the seismic coupling in hard rock. Existing data can be explained if ice controls the sliding friction on preexisting cracks.
Generation Of High Frequency P And S Wave Energy By Rock Fracture During A Buried Explosion
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Author :
language : en
Publisher:
Release Date : 2007
Generation Of High Frequency P And S Wave Energy By Rock Fracture During A Buried Explosion written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
The micromechanical damage mechanics developed by Ashby and Sammis (1990) was used to explore the effects of rock fracture on the seismic coupling of explosions. An important focus was the effect of ice in the fractures. The main effect of ice in the cracks of crystalline rock is to bridge the existing cracks forming a larger number of smaller cracks. Ice also increases the coefficient of friction on the cracks resulting in a significant increase in both elastic stiffness and fracture strength, both of which are temperature and strain-rate dependent. The damage mechanics model was used to interpret laboratory data on frozen rock and a field experiment in which chemical explosions were detonated above and below the permafrost layer in Alaska to directly observe the effect of ice in rock on the seismic coupling. Finally, we used the equivalent elastic medium model for an explosive source developed by Johnson and Sammis (2001) to explore the effect of an increase in both elastic stiffness and compressive strength on the amplitude of far-field seismic radiation. Our conclusion is that an explosion in frozen rock should have a smaller apparent yield than the same explosion in rock at temperatures above the freezing point and that the effect should be larger in limestone than in granite.
Shear Wave Generation From Contained Explosions
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Author :
language : en
Publisher:
Release Date : 1996
Shear Wave Generation From Contained Explosions written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1996 with categories.
The usefulness of the amplitude ratio of seismic phases such as Lg/P, as well as the ratio of magnitudes to discriminate explosions from earthquakes depends, in part, on the efficiency of shear wave production from seismic sources. We are studying shear wave generation at the source, initially from explosions within limestone blocks. Initially the samples are subjected to hydrostatic stress. However, we will be able to also simulate tectonic strain energy release in future experiments. Using a 1.6m long, 0.8m diameter sample subjected to an ambient pressure of up to 1 MPa, with a centrally placed explosive source, we propose to study the amplitude of shear wave generation of stress wave induced radial cracking in symmetric and asymmetric cavities. In unstressed rock, this shear wave production is expected to be controlled in part by the natural anisotropy of the rock. We expect to measure the SIP ratio from tamped explosions using (0.2 to 2 gram charges). Later tests will be conducted in partially decoupled asymmetric cavities, and the resultant shear wave radiation pattern will be compared to previous detailed finite element calculations of P and S wave radiation versus frequency and angle for elliptical cavities of aspect ratios in the range of 1:3 to 1:10. In order to measure the P and S waves generated from explosions, we developed a measurement method that is given in detail in this report. The initial test results for the tamped and decoupled explosions in cylindrical cavities in limestone show that the amplitude of SV/P for the decoupled experiment in limestone is -0.7, whereas it varies over a range of -1 to 3 for overdriven cavities, depending on angle from the cylindrical axis. Moreover, tensional cracks are generated in these cavities which resemble those inferred to have occurred in a similar geometry in the Sterling experiment.
Rock Fracture And Blasting
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Author : Zong-Xian Zhang
language : en
Publisher: Butterworth-Heinemann
Release Date : 2016-04-26
Rock Fracture And Blasting written by Zong-Xian Zhang and has been published by Butterworth-Heinemann this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-04-26 with Technology & Engineering categories.
Rock Fracture and Blasting: Theory and Applications provides the latest on stress waves, shock waves, and rock fracture, all necessary components that must be critically analyzed to maximize results in rock blasting. The positioning of charges and their capacity and sequencing are covered in this book, and must be carefully modeled to minimize impact in the surrounding environment. Through an explanation of these topics, author Professor Zhang’s experience in the field, and his theoretical knowledge, users will find a thorough guide that is not only up-to-date, but complete with a unique perspective on the field. Includes a rigorous exposition of Stress Waves and Shock Waves, as well as Rock Fracture and Fragmentation Provides both Empirical and Hybrid Stress Blasting Modeling tools and techniques for designing effective blast plans Offers advanced knowledge that enables users to choose better blast techniques Includes exercises for learning and training in each chapter
Seismic Effects Of Blasting In Rock
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Author : A.A. Dauetas
language : en
Publisher: CRC Press
Release Date : 1993-01-01
Seismic Effects Of Blasting In Rock written by A.A. Dauetas and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993-01-01 with Science categories.
The results of theoretical and experimental investigations of seismic waves depending on natural and technological factors are discussed, with methods for engineering calculations of industrial blast parameters.
Empirical Observations Of Earthquake Explosion Discrimination Using P
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Author :
language : en
Publisher:
Release Date : 2007
Empirical Observations Of Earthquake Explosion Discrimination Using P written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
We continue exploring methodologies to improve earthquake-explosion discrimination using regional amplitude ratios such as P/S. The earliest simple source models predicted P/S wave amplitudes for explosions should be much larger than for earthquakes across the body wave spectrum. However empirical observations show the separation of explosions from earthquakes using regional P/S amplitudes is strongly frequency dependent, with relatively poor separation at low frequencies (≈ 1 Hz) and relatively good separation at high frequencies (> ≈3 Hz). We demonstrate this using closely located pairs of earthquakes and explosions recorded on common, publicly available stations at test sites around the world e.g. Nevada, Lop Nor, Novaya Zemlya, Semipalatinsk, India, Pakistan, and North Korea. We show this pattern appears to have little dependence on the point source variability revealed by longer period surface wave modeling. For example regional waveform modeling shows strong tectonic release from the May 1998 India test in contrast with very little tectonic release in the recent North Korea test, but the P/S discrimination behavior is similar in both events, using the limited regional data available. While accepted explosion P-wave models have been available for many years, the frequency behavior of the P/S discriminant has inspired a variety of competing models to explain how explosions generate S-waves. We briefly review some of these models in the context of the P/S discriminant observations. One hypothesis is that S-waves are generated mainly from conversion of P-waves and surface waves, so S-waves from explosions can be predicted from the P-wave models via a frequency dependent transfer function. A different hypothesis is that significant generation of S-waves comes from the CLVD (compensated linear vector dipole) component created by spall above the explosion. A recent model by Fisk (2006) shows the explosion S-wave spectra can be modeled using the P-wave spectra with the corner frequency reduced by the ratio of the wave velocities, which seems to imply a direct generation of S-waves in the source region. We examine a number of nuclear tests from around the world in light of these models. Given the importance of depth on some of the model predictions we reexamine some of the overburied explosions in Nevada. We also look at chemical explosions, including dedicated single shots at different depths and mining shots at adjacent open pit and underground mines to look at depth effects. Finally we examine a subset of Nevada data with signal above noise up to 16 Hz to determine if discrimination performance saturates at frequencies around 6 Hz as some models predict, or continues to improve at higher frequencies.
Wave Generation From Explosions In Cavities In Rock
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Author :
language : en
Publisher:
Release Date : 1998
Wave Generation From Explosions In Cavities In Rock written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1998 with categories.
We have developed a measurement mehtod to monitor P- and S-waves generated from laboratory-scale explosions in meter-sized rock media at a series of stations, and invented a unique device to drill spherical cavities with diameters of up to 10 cm in rock. We have also conducted laboratory experiments in which spherical/cylindrical charges of 0.2 to 1.9 g mass were detonated at the center of spherical/cylindrical cavities with radii from 0.6 to 1.5 cm in Bedford limestone and the waves generated by the explosions were recorded in the near field within 250 mm. The reccords and post-explosion studies clearly demonstrate the P-waves generated from both explosions in cavities and crack propagation in rock. The peak particle displacement induced by P-waves ranges from 9 to 15 um at 150 to 210 mm from the source for the spherical cavity experiment with 1.9 g explosives, and 8 to 4 um at 150 to 220 mm from the source with 0.8 g explosives, 35 to 10 um at 150 to 240 mm for the tamped cylindrical cavity experiment with 1.2 g explosives and 7 to 2 um at 150 to 190 mm from the source for the decoupled cylindrical cavity experiment with 0.24 g explosives.
Numerical Experiments Investigating The Source Of Explosion S Waves
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Author :
language : en
Publisher:
Release Date : 2007
Numerical Experiments Investigating The Source Of Explosion S Waves written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
In this study we use validated explosion simulations to investigate the locations at which explosion S-waves originate. Several mechanisms for generating S-waves from an explosion source have been put forward. These mechanisms include tectonic release, non-symmetrical source effects, non-linear source effects, conversion of P-waves to S-waves off the free surface, and scattering of near-source Rayleigh waves. Each of these mechanisms is physically sound, and each mechanism likely contributes to the observed S-wave field. Identifying where explosion S-waves originate provides an important constraint on the contribution of each S-wave mechanism. The simulations in this study are based on the well-recorded 1993 Nonproliferation experiment (NPE) (chemical kiloton). A regional 3-dimensional model surrounding the NPE is validated by first extracting vertical cross-sections cutting through the NPE source and stations at which the NPE was recorded. We then generate synthetic seismograms using a 2-dimensional finite difference calculation for each event-station path. Good agreement between synthetic and observed seismograms provides confidence that the model and simulations are reasonably accurate. The origin of S-waves is determined through both analysis of the simulated wavefield evolution and using the timereversal method to refocus far-field S-waves back to their origin. Preliminary results suggest that the primary S-wave pulse originates near the free surface and at high-impedance geologic interfaces that are close to the explosion. These results suggest that scattering can account for much of the observed S-wave energy radiated from the NPE explosion.
Seismic Effects Of Blasting In Rock
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Author : A.A. Dauetas
language : en
Publisher: Routledge
Release Date : 2017-11-01
Seismic Effects Of Blasting In Rock written by A.A. Dauetas and has been published by Routledge this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-11-01 with Science categories.
The results of theoretical and experimental investigations of seismic waves depending on natural and technological factors are discussed, with methods for engineering calculations of industrial blast parameters.
Seismic Waves From An Underground Explosion In A Salt Bed
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Author : D. S. Carder
language : en
Publisher:
Release Date : 1962
Seismic Waves From An Underground Explosion In A Salt Bed written by D. S. Carder and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1962 with Nuclear excavation categories.