SU1608600A1 - Method of predicting avalanche danger - Google Patents

Abstract

The invention relates to lava science and is intended to predict local snowfalls under the influence of the entire complex of snow and meteorological factors. The aim of the invention is to improve the accuracy and reliability of avalanche hazard prediction. For this, acoustic emission signals are recorded separately in the high and low frequencies. When the intensity ratio for each of the range ≥3.5 record the onset of avalanche danger. 1 hp f-ly, 2 ill.

Description

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The invention relates to avalanche and is intended for the prediction of volcanic snow falls under the guvius of the whole complex of snow and meteorological factors. 2 of the invention is to increase the accuracy of predicted avalanche danger.

1 figure 1 shows the dependence

1VIEWS of acoustic signals: AI from voltage; Fig. 2 is a block diagram of a device for implementing a method for predicting a hazard.

Acoustic emissions of voids in the snow layer at the time of operation are: spinal

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voltages (J 5 O, 55 C (where the ultimate voltages), which makes it possible to predict the avalanche danger before the avalanche. Placing acoustic sensors in the avalanche collection allows obtaining information about the processes of snow destruction directly for the dangerous slope.

As a result of the research, it was established that each mastaba has its own characteristic frequencies: destruction of bridge connections between snow grains correspond to acoustic emission signals of 4–8 kHz, snow grain destruction - signals of 2–2.5 kHz, snow piecewise destruction frequency signals

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250-500 Hz, large-scale destruction of snow - signals with a frequency of 25 Hz.

A necessary sign of the loss of snow stability on a slope is the destruction of only large volumes of snow, which correspond to signals with a frequency below 500 Hz. Allocating signals of this frequency, besides increasing the reliability of the prediction, can significantly increase the sensitivity of the apparatus to the formation of cracks snow on the slope.

However, external sources, such as seismic, flying helicopters or lifting devices, can also excite low frequency disturbances in the depths of snow. Since the destruction of any scale in the snow is accompanied by the appearance of signals with a frequency of about 10 kHz, the increase in intensity in the low frequency interval is indeed due to the destruction of the snow mass, and, rather than interference from external sources, must be accompanied by an increase in intensity in the high frequency range.

Thus, the allocation of acoustic emission signals with a frequency of 2-16 kHz and an assessment of their intensity over the same time intervals allows one to obtain independently confirmation of the reliability of the recorded low-frequency signals as corresponding to the true snow destruction.

On the other hand, in the snow cover, besides the processes of destruction, there are processes of local restructuring of the structure, which end with healing of cracks, relaxation of stresses, i.e. snow stabilization on the slope. These processes are accompanied by acoustic emission signals with a frequency of 2-V 20 kHz. The avalanche danger is indicated only by those signals of the high-frequency range, which are reinforced by the presence of acoustic emission signals in the low-frequency range. Therefore, the acoustic emission signals of the high frequency range can only be considered as a sufficient sign of the destruction of the snow layer on the slope leading to an avalanche.

Therefore, to estimate the stress-strain state of snow cover on a slope, it is advisable to select acoustic emission signals in at least two Ranges: high-frequency, 2-16 kHz, and low-frequency 10-500 Hz, and increasing the signal intensity as a necessary sign of avalanche danger. low frequency range, and as sufficient - a similar increase in the intensity of signals in the low frequency range.

It was established in experiments that with an increase in stresses in snow, the intensity of acoustic emission signals increases, and the following steps can be distinguished:

Iп / п „0,225Cr / 6j {.

IIn / n 0.750G / G

IIIn / n 6.7 (S / (J

where is the intensity ratio

given period of time to the previous one.

It should be noted that in the transition from one tension state to another, i.e. from I to III, the angle of inclination C | considered dependencies. From this it follows that, knowing the intensity of acoustic emission signals for two equal periods of time, it is possible to determine the direction of the processes in the snow (stabilization or destabilization). For example, an increase in intensity of 3.5 times corresponds to a transition from stage I to stage II, and an increase in intensity of 9 times means a transition from stage I to stage III. The critical state, i.e. to the state preceding the avalanche, corresponds to n 7600/3 h,

The intensity of the acoustic emission signals is estimated at equal intervals of time. In practice, it is advisable to choose the length of time intervals for comparing 0.5 to 3 hours. At intervals of less than 0.5 hours, the number of pulses may be small and then random interference will reduce the objectivity of the assessment. With a time of 3 hours, against the background of a large number of pulses, the onset of dangerous changes can be overlooked, which will reduce the reliability of the operational control.

The proposed method is implemented as follows.

In the snow layer of avalanche collector 1 (Fig. 2). Acoustic sensor 3, electrically connected to preamplifier 4, whose code through the line is placed, is rigidly bonded to waveguide 2.

A SLANCH is connected to the input of amplifier 6. The signal after amplifier 6 is supplied to filters 7 and 8, by means of which the selection of the high-frequency and low-frequency components is made. After filters 7 and 8, the signal enters the discriminators 9 and 10. Each excess of the threshold level is converted into an electrical impulse and fed to counters 11 and 12, which sum these signals for a predetermined period of time. The number formed in the counters, by the signal of the timer and by pa

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and;) Registry 13. If the number in the counter is PR (1 the number in the register in 3.5 times the output of the comparator 15 appears high potential, otherwise it is low. The same functions are performed by counter 12, register 14 and compa- ny 16, but for high-frequency components of acoustic emission signals 11p4, counting the number in the counter 12

enters the buffer registers 13 14. After this, the counters of the counters are reset to zero. In company 15, a comparison of the two is eaten:

compared with the number in the register of 14 volts;, 5 times at the output of the comparator 16 appears the high potential, otherwise it is low. Item sravl

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17 performs a logical operation I. If there is a high potential, indicator 18 is turned on at both its inputs, indicating an avalanche danger. The summation time is set by timer 19.

Claims (1)

1. A method for predicting avalanche danger, including placing acoustic sensors in the snow mass, recording acoustic emission signals, characterized in that, in order to increase the accuracy and reliability of the prediction, the sensors are placed in the avalanche separation zone, acoustic emission signals are recorded separately in the low-frequency and high-frequency ranges and by reaching the ratio of the intensities of this gap, the occurrence of an avalanche hazard is determined for each of the ranges S 3,5 for each of the ranges S 3,5. 25 2, Method POP1, characterized in that the low-frequency 30 range is selected in interval 10500 Hz, and high frequency - in interfig .1 J (/ f3 6 ten Fi.2 J7 {