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Electromagnetic Effects at Blasting Destruction of Rocks

#2000


Electromagnetic Effects at Blasting Destruction of Rocks

Tech Area / Field

  • PHY-RAW/Radiofrequency Waves/Physics
  • PHY-SSP/Solid State Physics/Physics

Status
8 Project completed

Registration date
18.09.2000

Completion date
10.11.2004

Senior Project Manager
Tyurin I A

Leading Institute
NIIIT (Pulse Techniques), Russia, Moscow

Supporting institutes

  • Institute of Dynamics of the Geosphere, Russia, Moscow\nVNIITF, Russia, Chelyabinsk reg., Snezhinsk

Collaborators

  • National Institute for Resources and Environment, Japan, Ibaraki

Project summary

One of the main problems which should be solved during the control over the Comprehensive Test Ban Treaty (CTBT) is the problem of nuclear explosion selection from numerous explosions of chemical high explosive (HE). Experiments carried out during the ISTC Project #835-98 implementation show that the model underground chemical explosions (UCE) of charges even with mass of 3 kg are accompanied by electromagnetic pulse (EMP) with broad frequency range, whose amplitude fast falls off as the distance from epicenter increases. Therefore, during on-site inspection (OSI) of declared underground explosions the EMP recording permits to establish the fact of explosion realization and a moment of detonation. During realization of several bursts, the amount of the made bursts and time intervals of their following one after another can be established by means of EMP measurements in the near zone.

The main goal of the proposed Project is further revision of recommendations for methodological and hardware support of an electromagnetic method of monitoring and verification of CTBT, developed in the ISTC Project #835-98. It will require creation of a database on electromagnetic effects at bursts of chemical HE of different yield, carried out in perse conditions. The development of principles and technique of selection by EMP of underground nuclear explosions (UNE) (based on published data) and UCE investigated in the proposed Project in the noise of natural and artificial origin will permit to obtain a technique of recognition of UNE and UCE by an electromagnetic method.

In the course of the ISTC Project #835-98 it has been demonstrated that one from significant sources of EMP for UCE is the process of the rock destruction during their shock wave loading. Therefore, an important problem of the proposed Project is the experimental and theoretical research of electromagnetic effects bound up with blasting destruction of rocks.

At the beginning of the Project it is supposed to upgrade equipment and techniques of the EMP measurement, namely: to increase sensitivity of magnetic fields transducers and to produce autonomous small-size electrical gauges; to expand possibilities of the measuring equipment of both analog and digital types; to develop a technique of recording electrical fields in the ground.

Then, at the VNIITF test site the EMP measurements will be continued in dynamic experiments with the bench-mark separation in time of possible EMP sources: at the rocks destruction at the powder installation without using explosive as possible source of EMP, and in the model explosion experiments in artificial strong media with the reference point time separation of processes. It will permit to separate in time such possible sources of EMP as a charge detonation and expansion of the cavity, destruction of the ground in a shock wave as a result of shear deformations, spell fracture of blocks after the shock wave emergence to a free surface. The measurements of EMP will be conducted also at small-scale UCE in granite with mass of HE up to 100 kg on a test site near Vyborg and at large-scale UCE with mass of HE up to 400 t at the apatite mines of the Kola peninsula.

The processing of obtained results will permit to create a database on electromagnetic effects under explosions of chemical HE with different yields and to establish the dependencies of EMP parameters on the external factors and conditions of the explosion realization. The principles and technique of selection of UNE and UCE using EMP taking account of artificial and natural noises will be formulated and developed. It will enable revision of the proposals on hardware of electromagnetic method of inspection of the underground explosions realization under the CTBT conditions.

The measurements of electric conductivity (EC) of rocks will be extended to the area of high pressures up to 150 GPa with purpose of obtaining initial data for calculation of EMP generation at bursts with the energy concentration being higher than that of chemical HE. For the purpose of studying the generation and propagation of EMP at UCE in humid and porous sandy loams, such measurements will be conducted at shock wave pressure being lower than 10 GPa and down to zero value. The measurements of EC of explosion products both behind the front of a detonation wave, and at their unloading up to stopping the cavity in rocks at camouflet bursts are also necessary for theoretical calculations of EMP generation.

On the basis of the refined scheme of experiments on study of shock polarization of rocks in the IDG explosion chambers the dependencies of surface density of an electric charge on pressure in a wave of compression for the samples of granite, basalt, marble and some other rocks are expected to be determined. The obtained data will be used to calculate the contribution of the shock polarization effect to EMP at burst of a chemical charge in typical rocks.

The development of the models of EMP generation and propagation at blasting destruction of rocks is expected to be conducted with the participation of the groups of the physicists-theorists and mathematicians from all three Institution-Participants of the Project and Prof. V.A.Terekhin, head of a theoretical department of VNIIEF. Developed by efforts of the theorists of VNIITF and IDG under the Project #835-98 the semiempirical models of the rocks conductivity behind the front of a shock wave and the rocks polarization will be advanced in the scope of this Project. In VNIITF the model of high-rate deformation of rocks describing at micromechanical level processes of their destruction at dynamic compression, expansion and shift will be created. The theorists and mathematicians of VNIIEF and RIPT jointly with Prof. V.A.Terekhin will create the specialized "electromagnetic" two-dimensional code taking account of new developed models, inhomogeneities of ground and features of the upper conducting layer. Using this code the numerical modeling of experiments carried out under the given Project and the ISTC Project #835-98 will be conducted. The advanced complex of the programs will permit to conduct numerical simulation of EMP generation at high-power bursts of chemical HE in rocks and at bursts with the high energy concentration.

This work can result in the well-grounded methodology and hardware for monitoring the amount and physical nature of underground explosions. The competence of the participants of given Project is confirmed by results of work in the area of an experimental and theoretical gas dynamics as well as in the area of a research of generation and propagation of EMP at explosions, in particular, in activities under the ISTC Project #835-98.


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