Distortion mining
goaf is proced under the surface by man-made excavation or natural geological movement; Empty & quot;, The existence of goaf makes the safety proction of mine face great safety problems, personnel and mechanical equipment may fall into the goaf and be injured
e to the lack of timely and effective backfill and grouting treatment in some places, the area of underground goaf in China is becoming larger and larger. Goaf changes and destroys the natural balance of the earth's surface and lithosphere, resulting in Goaf Collapse and other geological disasters
the collapse of goaf is caused by the goaf of ore body (layer) and the destruction of overburden. The mechanical balance of overlying rock above the orebody will be broken when the underground orebodies of various sizes are mined and mined out. Under the action of gravity and stress, cracks and fault displacement will occur. Groundwater will take advantage of the deficiency and leak into the goaf through cracks, which will accelerate the destruction of overburden, cause the movement of strata and surface, and finally form the Goaf Collapse Area
the collapse area will not only lead to the depletion of groundwater, the destruction of cultivated land, the deterioration of ecological environment, but also damage the local houses, the ground fissure deformation of roads, the construction difficulty and cost of major projects such as expressways, railways, airports and urban buildings e to the treatment of Goaf Collapse. In addition, the surface cracks will provide sufficient oxygen for the underground natural coal seam, the underground coal fire will weaken the roof pressure of the goaf, aggravate the caving, widen and lengthen the ground cracks, and finally form a vicious circle of "ground cracks fire area surface cracks"< Gravity exploration method is to use the mass loss or surplus of underground geological bodies to observe the gravity anomaly caused by them on the surface, so as to determine the distribution, size and boundary of underground geological bodies. The quality loss of goaf e to mining results in low gravity anomaly. When the goaf is well preserved, the low value resial gravity anomaly is formed. When the goaf collapses without water filling, the mass loss value remains unchanged, but the negative density value decreases and the influence thickness increases; When the water is filled, the loss mass is compensated to a certain extent, and the negative density value is reced. No matter what kind of situation actually exists in the goaf, the local resial gravity anomaly can be detected according to the general law. Using high density and high precision microgravity survey and proper data processing and interpretation methods, the area of goaf can be controlled. In order to improve the accuracy of interpretation, the digital terrain multi-slice high-precision geological reconstruction method and three-dimensional interpretation method are adopted< In the field measurement, all the electrodes are set on a certain interval measuring line, and then connected to the programmable multi-channel electrode converter with multi-core cable, so that the electrode layout can be completed at one time. In order to collect a large amount of data accurately and quickly, the electrode arrangement, electrode distance and measuring point can be quickly converted by program control. With the help of the electrical processing software, the collected data are processed and the results are illustrated, which makes the interpretation more convenient and intuitive. Based on the results of electrical resistivity tomography in goaf and inclined air shaft of a power plant, the application of electrical resistivity tomography in goaf and inclined air shaft is discussed. The results show that the two-dimensional measurement method of electrical resistivity tomography in goaf and inclined air shaft is accurate and feasible; If there is no water in goaf and inclined air shaft roadway, the resistivity tomography two-dimensional measurement results are generally high resistance abnormal closed circle, if there is water, it is low resistance abnormal closed circle< 2. Transient electromagnetic method (TEM) is to observe the inced secondary field which changes with time caused by the eddy current inced by the underground geological body ring the intermittent period of sending a pulse magnetic field to the underground. The size of the secondary field is related to the electrical property of the underground geological body. The attenuation speed of the inced secondary field of the low resistance geological body is slow and the voltage of the secondary field is large; The inced secondary field of high resistivity geological body decays faster and the secondary field voltage is smaller. According to the characteristics of the attenuation curve of the secondary field, we can judge the electrical property, nature, scale and occurrence of the underground geological body. Because the signal received by the transient electromagnetic instrument is the electromotive force of the secondary eddy current field, after normalizing the secondary potential, according to the change of the normalized secondary potential value, we can indirectly solve the geological problems such as collapse column, goaf and fault. This method has the advantages of high resolution, high efficiency, little influence by terrain, and can penetrate the high resistivity overburden, and has rapidly developed into an efficient and fast geophysical method. The transient electromagnetic method is applied to the detection of a goaf, and the effect is good. It not only infers the scope of the underground goaf, but also judges the water accumulation in the goaf
3. Very low frequency electromagnetic method
very low frequency electromagnetic method generally uses the electromagnetic wave emitted by the radio with the frequency of 15-25khz as the field source. When the electromagnetic wave meets the geological body in the process of propagation, it polarizes and proces the secondary current, which causes the inced secondary field. Generally speaking, the amplitude direction and phase of the total field and the primary field after the combination of the secondary field and the primary field are not the same, which causes the distortion of the primary field. The existence of goaf can be found by measuring the distortion of some parameters with special instruments. The VLF electromagnetic method is usually divided into two methods: dip angle method and wave impedance method. When detecting high resistance body, the wave impedance method is generally used for VLF electromagnetic method measurement. The direction of the measuring line should be consistent with the direction of the transmitting station or the angle between the measuring line and the direction should be minimum
4. Ground penetrating radar (GPR)
GPR uses high-frequency electromagnetic wave to send it from the ground to the ground through antenna t in the form of wide-band short pulse, and returns to the ground after reflection by reflector, and receives it through antenna R. When propagating in the medium, the intensity and waveform of electromagnetic wave will change with the electrical properties and geometric shape of the medium. Therefore, the structure of the medium can be inferred from the two-way travel time, amplitude and waveform of the received wave. Ground penetrating radar is suitable for detecting shallow targets. Because it can replace antennas with different frequencies, it has a wide range of applications and high detection resolution, so its application in engineering has been recognized. GPR data can be processed by special software, focusing on amplitude recovery, filtering, F-K filtering and deconvolution. The time profile with high signal-to-noise ratio is obtained, which improves the identification of useful signals. The radar time profile reflects the changes of underground media more truly and comprehensively, and ensures the data quality, The electrical difference of underground medium is used to stratify and identify underground abnormal geological bodies. This method is fast and accurate, especially for the detection of underground goaf, civil air defense engineering cavern and underground karst cave< 5. MT, AMT, HMT and CSAMT methods
magnetotelluric method (MT), audio magnetotelluric method (AMT) and high frequency magnetotelluric method (HMT) are essentially passive source frequency domain electromagnetic methods for collecting natural field signals. The difference lies in the different frequency of the collected signals, the corresponding detection depth and resolution. High frequency magnetotelluric (HMT) signal frequency is high, up to 100kHz, the depth of research is shallow, from more than ten meters underground to more than 1000 meters. This depth range is just the most active depth of human mining, underground engineering construction, groundwater resources development and other proction activities. Therefore, high frequency magnetotelluric method has made great progress in both theoretical research and instrument implementation in the past ten years, and has become the main method of medium depth goaf detection. This method does not need artificial field source, has low cost, has large exploration depth, is not affected by the shielding of high resistivity layer, and has high resolution for low resistivity layer
CSAMT (controlled source audio frequency magnetotelluric method) is a method that uses a finite length wire grounded at both ends as the emission source, uses artificial source to excite the alternating electromagnetic field, observes the electromagnetic response on the surface, and calculates the wave impedance and apparent resistivity for exploration. Because of the high resolution of CSEM, CSEM can detect the geological anomaly in electrical property and become one of the methods of goaf detection. The biggest feature of this method is the use of artificial field source, which greatly increases the intensity of electromagnetic signal and makes up for the weakness of natural field source, such as weak signal and difficult observation. However, e to the existence of field source, this method also has its inherent shortcomings, such as field source additional effect, near-field effect, field source shadow effect, transition zone effect and heavy equipment, which affect the application of this method to a certain extent.
Generally, novice players are easy to lose all the time. It's good to understand the basic rules of the game. At the beginning of the game, players will have a base. The type of base determines the combat units that players can obtain at any time. They rely on different combat units to strike the enemy to the greatest extent, and seize enough resource points to expand the advantage, and finally win the game
several key points need to pay attention to:
1. Occupy resources
there will be a watchtower of resources at 6:00, 12:00, 18:00, 21:00 and the center of the map. After occupation, you can obtain the corresponding resources. The center is twice the other four points, but it is relatively difficult to keep. Please think about it yourself
2, arms selection
interstellar 2 arms restraint is quite strong, in the selection of arms, we must pay attention to the opponent's movement, try to use the arms to restrain the opponent
3. Upgrade attack and defense
in the base, you can upgrade attack and defense for arms. According to the actual situation, upgrade attack and defense or update arms first
4. The mercenary system
there will be a purchase point for mercenaries next to the base. The prophase colossus is a very powerful branch. You can decide whether to buy mercenaries according to the other party's branch. In the case of the same arms and forces, one more mercenary often determines the outcome of a battle
5, initial talent
the initial talent is related to the later development path, try to determine the development direction according to the talent advantage
tips (every time you fight with others, you need to see his defense. If he has a tank, don't rush to go all out, but go to his side, press s, and then send some soldiers to his tank, And every time we fight with others, we'll see the number of them and whether there are others behind us, and we'll also see whether we and our team-mates can fight with each other. But when we leave home, they chase our Q soldiers. Don't be afraid that if we have Q, we'll make a profit (in the case of no big difference in defense). Then you can see the current situation, you won't ask your team-mates to help you. You can ask your team-mates to see if the enemy has prism tunnels and keep the mines on both sides at any time In case others steal you, and then build 2 photons in front of your home to prevent the prism from sneaking attack. I'm not finished yet. I'm too tired to write to you next time!!
just last year, e to the lack of proction capacity and the mining boom, the overall price of computer hardware has been soaring to the peak. Memory was even once jokingly known as the best financial proct in 2018, with the market price nearly doubled
at that time, some instry leaders predicted that the price of computer hardware would be hot until at least 2020, which directly made many DIY players feel at the bottom
but who would have thought that within half a year of this remark, the market price immediately went down, the memory price even went down again and again, and even indivial brands had a short-term continuous shock
now it's time for students to start school in spring, and the major e-commerce platforms have also launched the first wave of promotion activities in the next year. Many student party members and those who need to change planes are hesitant to see such a price trend. Is it suitable to install planes now
with the release of new hardware approaching, should we start with low price? Or wait a little longer
should we buy early and enjoy early, or buy late and enjoy discount? Today we will analyze the current trend of hardware market in detail
the decline of raw materials ushers in a new era of price rection
in fact, whether it's CPU, graphics card, memory or solid state disk. Although there are many kinds of proct functions, as a semiconctor instry proct, wafer is indispensable in the proction process
in recent years, demand for semiconctor chips has reached the peak in the market e to the expansion of mobile phone market and the drive of virtual money bubbles. Wafer as an important semiconctor raw material, its price is naturally rising
at present, 92% of the world's wafers are supplied by shinyue (27%), Shenggao (26%), Taiwan global (17%), Shichuang (13%) and LG (9%)
as the third largest wafer manufacturer in the world, the chairman of Taiwan global wafer once told the media last year that all the proction capacity of the enterprise has reached 2020, and the supply of wafers in the market exceeds the demand, so there is no possibility of price rection
we know that the larger the size of the wafer, the more chips can be cut. Last year, the downstream OEM manufacturers have extended their procts from 12 inch wafers to 8 inch and 6 inch wafers
it's good to say that e to the high precision of proction technology, the fluctuation of proct price also lags slightly
however, the shortage of raw materials directly leads to a serious shortage of storage grain proction capacity for OEM manufacturers of memory, solid-state hard disk and other memories. This is why since 2017, the original memory of about 200 yuan will rise several times in a short time
it's better to calculate by man than by nature
since last year, e to the sharp decline in smartphone shipments, the collapse of bitcoin, and the decline in revenue of OEM manufacturers, the overall demand for wafer raw materials by OEM manufacturers has slowed down e to a combination of various reasons
in the context of the general environment downturn, some people have begun to press the button
recently, Shengke electronics of Taiwan announced that the price of 12 inch wafers will be reced by 6% - 10% from Q2 of 2019. In addition, it is reported that the major OEM manufacturers have been actively negotiating with shinyue and Shenggao to rece the price of wafers
in the era of big price rection of computer accessories, we can see the hope
will the price of memory increase
the oversupply of the memory market is actually more serious than expected
since the end of last year, suppliers have been actively recing prices to seek the market, but the demand in the personal installation market has been suppressed to a very low level e to the overall high price and the large shortage of Intel processors
the inventory of memory manufacturers has always been unable to be digested. This situation finally broke out this year, and the memory price began to return to the normal price range
from the perspective of consumers' subjective feelings, the decline of memory is from 30 yuan to 50 yuan, and the price of indivial brands has been reced by 80 yuan, but the overall price is still at the high level of 400 yuan, so most people are not very sensitive to this kind of price rection
after consulting terminal agents, we learned that the recent decline in memory prices has not significantly stimulated sales
it can be inferred that if the demand can not be released all the time, there is still room for the memory price to continue to decline in the future, or even return to the range of 300 yuan
according to the current inventory digestion rate, the situation of high inventory will remain until about August this year
this is undoubtedly a good thing for consumers
graphics card, I said it would rise, do you believe it
most people are more concerned about the graphics card market.