Blasting seismic effect and monitoring process
The explosive explosion causes a shock wave, which gradually decays in rock into stress wave, and energy is gradually reduced. When it is destroying the rock, only the elastic vibration of the rock mass is formed, and the seismic wave is formed. The energy of seismic waves accounts for only 2-6% of the total explosion. According to the seismic wave propagation path, it can be divided into two categories: one is propagated along the inside of the rock mass, referred to as a body wave; the other is to propagate along the surface of the rock, referred to as a face wave. The body wave can also be divided into longitudinal waves and horizontal waves, and the surface wave can be divided into Rayleigh wave and Ravbo. Among them, the Rayleigh wave frequency is low, slow attenuated, large amplitude, long period of time, and is a large amount of energy carrying the earthquake.
Method for blasting seismic safety evaluation
There are three main methods: blasting seismic mining supplier integrity, dynamic analysis and single parameter method. The first two methods or insufficient precision or the theoretical is not perfect, and they are rarely adopted. Single parameter method control indicator has the largest vibration speed, maximum acceleration, maximum displacement, energy ratio, etc. of which is most convenient, and most of them use them for safety assessment standards. The blasting vibration criterion in the terrestrial building in my country (GB6722-2003), using the protective object in the location peak vibration speed and the main oscillator frequency. The quality point vibration speed can be synthesized from the horizontal radial velocity, horizontal tangential speed, and vertical velocity of mutual verticality, wherein the horizontal radial speed is small, so we only need to measure the vertical speed.
ground building and structures To protect the object. According to the existing research results, the speed peak of the base is greater than the speed peak of the column; the speed peak of the column is greater than the speed peak of the wall, the roof panel and the circle beam; the speed peak of the upper surface is greater than the speed peak of the lower surface; The lower speed peak is greater than the speed peak above the wall. Therefore, the measuring point is selected on the upper surface; if the foundation buried under the soil layer, select the closest foundation and solid water as the measuring point.
In general, if the geological conditions are not changed, the distorting speed of the explosion is greater than the point away from the explosion source. Therefore, the protective object selects the most recent buildings from the explosion. Based on the corner, the probe is placed in the angle, and a instrument can simultaneously measure the vibration speed at three o’clock at the same time to more fully understand the impact of blasting on the entire building. The probe needs to be firmly bonded using gypsum and foundation.
On-site monitoring implementation After the monitoring point is determined, the use of raw gypsum powder and water is used as a paste, and the sensor is bonded in the tunnel.The test point of the surface, about 10 min gypsum can be tested. During the installation, the vertical speed sensor should be kept vertically with the horizontal plane; the level of the horizontal speed sensor should be parallel to the horizontal plane, and the horizontal direction of the horizontal speed sensor has a bubble. If the installation is in a horizontal state, the bubble should be in the middle position of the scale. You can contact Beijing Tianzhu Technology Sensors to sensor-related materials.
If a three-phase speed test (vertical, diameter, cutting) is used, the vertical speed is measured by a vertical sensor, and the radial direction, the radial, tangential speed is measured by two horizontal sensors. The mounting radial horizontal sensor should be horizontally directed, and the tangential level speed sensor is vertically vertically and horizontally horizontally.
Blasting vibration monitoring should be considerable attention
Selection of blasting vibration monitoring points should pay attention to the following points:
for Ensure the safety of the tunnel structure, need to be reasonable in the tunnel. The number of points should be more enough to have enough data to analyze the decay regulatory law of ground vibration propagation and the relationship between parameters such as burst. The effects of different landforms and geological conditions should be considered, and it is easy to understand the analysis of these factors on the effects of blasting vibration effects. The number of measuring points and settings can be adjusted according to the actual situation.
Test results analysis
Waveform analysis
The characteristic of the blasting vibration waveform is a short interval for multiple vibrations, because once blasting It is usually a segment explosion, and each blast will produce different vibration peaks depending on the amount of dose and blasting conditions (such as clamping conditions, cannon dispersibility, pharmaceutical structure, etc.), so according to different in waveform analysis The peak change of the moment, first find the peak vibration speed corresponding to different explosions, such a blasting vibration, and the peak vibration information under more proportional distance is obtained, and the reliability of the statistical analysis of vibration data is increased. Accuracy also improves the efficiency of vibration testing.
Today’s vibration tester has a FFT analysis tool software, which requires wavelet analysis, HHT analysis and other analytical methods. , Select the vibration waveform segment that is cared for spectrum analysis is an important part of the test results analysis, and the spectrum analysis needs to be unified.
Vibration duration
Blasting vibration duration is divided into a vibration duration and all blasting vibration duration. A vibration wave can be divided into a main vibration segment and a tail segment. From the beginning to wave to the amplitude attenuation to a \u003d AMAX / E as the main oscillating wave, the main vibration wave is in the duration of the segment vibration wave, according to the segment vibration wave, according to the segmentation wave, the interval, the damping characteristics of the media can be analyzed. All blasting vibration duration refers to the initial end of the vibration waveDuring the time, most cases the duration of all blasting vibration is not concerned, but it is also one of the important indicators of the anti-blasting vibration, and there is a meaning in consideration of vibration fatigue damage.
Seismic wave propagation speed (Vw)
Time label in the seismic waveform, can read out the timing of the zibuk to the measurement point, calculate the first to measurement points Waves (TW \u003d TB-TA), and different measurements to the distance difference (RW \u003d RB-RA), seismic wave versus VW \u003d RW / TW. When the measurement point is too close, since the difference is too small, if the sampling frequency is too low, the seismic wave wave speed is calculated low, and the error is large. Therefore, the two-point spacing should be increased when the wave speed is calculated, and the two detection points should be triggered simultaneously.
Only after entering the building group, after repeated blasting experiments and further optimized the blasting parameters according to the monitoring data and its regression analysis, the control digging feet, the control single-segment maximum medicine, multiple times Batch detonation and subtraction branch small guide tunneling, thereby controlling the blasting vibration effect at a lower level to ensure the safety of the surface building group security and blasting operations.
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