The purpose of geophysical exploration (including coal fire detection) is to give the geological information of underground space in the exploration area as detailed as possible, including stratum, lithology, structure, geometric occurrence state and so on. Three-dimensional visualization model is to simulate three-dimensional scene on computer and reproduce the three-dimensional distribution of geological structure and geophysical information, which is an important means to correctly understand geological structure. This can provide scientific basis for the description of various geological and geophysical phenomena, provide accurate and intuitive geological and geophysical models for engineers and technicians, and facilitate analysis and measurement.
Three-dimensional modeling work we carried out in Wuda coal fire area. The specific method is to use Surpac Vision software, based on the data of geophysical fields such as magnetism and electricity measured on the ground and in aviation, to establish a three-dimensional model of underground coal fire distribution by applying two-dimensional and three-dimensional inversion methods and combining with relevant geological data such as mining exploration and engineering, and to intuitively give the corresponding relationship between coal fire combustion state and geophysical fields such as magnetism and electricity, and to establish a three-dimensional model between the three-dimensional shape of coal fire and magnetic and electric anomalies on the ground or in the air (Figure 5? 1? 1)。
Figure 5-1-1surfac software work main interface
(1) Surpac software and its application method
Surpac Vision is a large-scale digital mine software, which is widely used in all stages of the whole mine life cycle, such as resource evaluation, mine planning, production planning management and so on. A set of three-dimensional and block-based modeling tools can be formed, and civil engineering can be designed graphically, three-dimensional models can be established, and engineering databases can be established to solve the construction management of boundary optimization in complex projects. At present, the software has passed the audit and certification of the Ministry of Land and Resources.
Surpac Vision is a professional 3D digital software for mine engineering, but it is widely used in geophysical exploration and geology.
(1)Surpac Vision's powerful three-dimensional graphics system can intuitively generate and display various graphics such as the three-dimensional structure of geophysical anomalies and the ground terrain model. Establishing a realistic three-dimensional geophysical model is beneficial to interactive geophysical interpretation and three-dimensional geometric design.
(2)Surpac Vision's powerful, open and flexible database management function is conducive to processing huge geological and geophysical data, technical data query and comprehensive analysis, calculation, statistics and statements.
(3)Surpac Vision has an open data exchange mode and secondary development function, which is beneficial to the communication and cooperation between geophysical prospecting and other majors.
In order to truly apply Surpac visualization software to geophysical modeling, it is necessary to solve the data input interface problem of geophysical investigation and interpretation results.
We mainly focus on the following three aspects.
Input method of (1) contour map. Give coordinates to geophysical grid point data to form three-dimensional coordinate discrete point data, then use the discrete point data interface of software to input data, and then re-grid to form isoline map.
(2) Input method of electrical inversion of underground 3D geological body. The result of electrical inversion is to invert the shape of underground geological body in the form of profile. For this geological body, it is necessary to input data according to the borehole data format within a certain distance.
(3) Data input method of underground 3D magnetic model. The results of magnetic three-dimensional inversion are mainly three-dimensional polygonal rectangles, which are widely distributed. If drilling is still used for input, the amount of data is too large, which will affect the running speed of the software. By studying the internal format of the software, the input of underground three-dimensional magnetic model is realized by programming.
(2) the result of establishing the three-dimensional model of coal fire.
According to the results of aeromagnetism, avionics, high-density electrical method and geophysical survey and inversion of radon survey in Wuda coalfield fire area, based on Surpac Vision software, the obtained data are processed by three-dimensional digital visualization model through the compiled program. All processing results are saved in digital form, and some processing results are shown in Figure 5? 1? 2 ~ Figure 5? 1? Five performances.
Fig. 5- 1-2 visualization model of coal fire geophysical investigation based on geophysical inversion results
Figure 5? 1? The lower part is a three-dimensional digital visualization model of underground magnetic body in Wuda coalfield fire area based on the three-dimensional inversion result of aeromagnetic δ T anomaly. There are three-dimensional color isolines of aeromagnetic δ T anomaly and three-dimensional color isolines of apparent resistivity of shallow underground calculated according to the results of aeroelectrical survey (23250Hz). According to the characteristics of rock physical properties changing with temperature in this area, Figure 5? 1? The underground magnetic body may be a strongly magnetic sintered rock mass. The apparent resistivity corresponding to the burning rock mass is also very high, which may be due to the high temperature of the burning rock mass. As can be seen from the figure, aeromagnetic and avionics anomalies are relatively consistent in space, and it is very effective and fast to detect coal fires in coal mine fire areas by using aeromagnetic and avionics technologies.
Fig. 5- 1-3 visualization model of coal fire geophysical profile based on the survey results of high-density electrical method.
Coloring is based on resistivity values.
Fig. 5- 1-4 visualization model of coal fire geophysical profile based on high-density electrical survey results.
Isograms and colors are based on resistivity values.
Figure 5? 1? 5 is the superposition effect diagram of radon gas, temperature, energy spectrum, aeromagnetism and high-density electrical method measurement results in the fire area of Wuda coalfield. The yellow thin line in the picture is the observed exposure range of surface coal fire. At the bottom of the figure is the solid model of fire area based on the resistivity of high-density electrical method180 Ω m, in which the red part is the solid generated according to the measurement results of high-density electrical method, and the blue part is the solid extrapolated from it. The superposition effect shows that all kinds of detection anomalies are in good agreement in three-dimensional space, which shows that the applied coal fire detection method can effectively delineate coal fire anomalies from different angles.
Fig. 5- 1-5 visualization model of coal fire geophysical exploration based on geophysical results
Based on high-density electrical method180 Ω m, the solid model of fire area, in which the red part is the solid generated according to the measurement results of high-density electrical method, and the blue part is the solid extrapolated from it.
(3) The application of 3D model in coal fire exploration and extinguishing.
Research on 3D digital visualization model of geophysical prospecting survey in Wuda coalfield fire area shows that:
(1) 3D digital visualization model shows various information such as 3D shape and scale of geophysical anomalies intuitively. 3-D digital geophysical inversion results are beneficial to interactive geophysical interpretation (Figure 5? 1? 2. Figure 5? 1? 3. Figure 5? 1? 5)。
(2) In the coal field fire prevention and extinguishing work, the location of fire source and the delineation of fire area undoubtedly play a vital role in the success or failure of fire extinguishing. For a long time, it has been a difficult and hot issue in coal field fire prevention and extinguishing research, and there is no very effective general method so far.
By realistically simulating the underground three-dimensional digital visualization model of coal mine fire, the fire area is delineated intuitively and accurately, and the fire area scale, burning depth and fire source position are inferred, providing reliable scientific data for fire prevention and extinguishing (Figure 5? 1? 2 ~ Figure 5? 1? 5)。
(3) In the grouting fire prevention and extinguishing work, according to the three-dimensional digital visualization model of coal fire, accurately locate the drilling hole in a planned way, scientifically design the drilling depth and other parameters, guide the fire extinguishing construction, improve the grouting effect, and reduce the blindness of fire prevention and extinguishing grouting (Figure 5? 1? 5)。