The early evaluation of coal resources in China mainly penetrated into coalfield geological exploration, such as the division of exploration levels such as coal prospecting, general survey, detailed survey and fine survey, and the division of coal seam stability, geological structure types and hydrogeological types. Most of them are qualitative and empirical. Due to the planned economy, there has been no real assessment of coal resources.
The comprehensive evaluation of coal resources in China began in the early 1990s. Since the reform and opening up, great progress has been made in coal industrial production and coalfield geological exploration. Obviously, the two kinds of forecasting coal results, namely, roughly forecasting the total coal resources and qualitatively evaluating its reliability, can not meet the needs of strategic development research of coal industry and long-term planning of coalfield geological exploration. Therefore, at the beginning of the third coal prediction, both prediction and evaluation were put forward. Based on the existing theories and methods of mineral resources evaluation at home and abroad, a set of evaluation methods suitable for the characteristics of coal resources and meeting the needs of coal resources exploration and coal industry development planning were developed. During this period, Wang Xizeng and Li Hengtang of Coal Science Research Institute completed the project of "Technical and Economic Evaluation Method of Coal Resources-Application of Analytic Hierarchy Process in Coal Resources Evaluation"; China General Bureau of Coalfield Geology has completed the project "Coal Accumulation Law and Coal Resources Evaluation in Ordos Basin" (China General Bureau of Coalfield Geology,1996); Zhao, Northern Coal Testing Center of Ministry of Geology and Mineral Resources, etc. Complete the project of "Comprehensive Evaluation of Development and Construction Conditions of Early and Middle Jurassic Coal Resources in Ordos"; Wu Chonglong of China Geo University developed a fuzzy comprehensive evaluation system for coal resources classification (CRCVS). Han, Department of Geology of China University of Mining and Technology, cooperated with Coal Geological Exploration Institute of Jiangsu Coal Geology Bureau and Changchun Institute of Coal Science to complete such topics as "Study on comprehensive evaluation method of coal resources in the border area of Sulu, Henan and Anhui" and "Statistical prediction of comprehensive information of coal resources in key mining areas (Fuxin mining areas)".
On the basis of geological evaluation and evaluation of mining technical conditions, coal economics researchers have made many achievements in economic evaluation of coal resources. For example, Wang Lixin (1996) put forward the economic evaluation theory of coal resources with the value of coal resources as the core, and formed the corresponding evaluation method. Liu Haibin (1997) put forward the principles and methods of evaluating the value of coal resources assets based on exploration cost, development investment, operation cost, external cost and coal price in mining areas.
The content of modern coal resources evaluation is very rich. According to the nature of the evaluation unit, it can be divided into four categories: exploration stage, well construction stage, development stage and pit closure stage (Wang, 1998). Or development, exploration and prediction (China Coal Geology Bureau,1996); According to the evaluation content, it can be divided into the following categories (Wang, 1998):
1) single factor evaluation, such as structural complexity evaluation, coal seam thickness and other occurrence conditions evaluation;
2) Comprehensive evaluation of coal resources, including evaluation based on exploration type, evaluation based on development priority, evaluation based on mining technology, evaluation based on mine geological conditions and comprehensive evaluation based on mine input-output analysis, etc.
3) Evaluation of mineral resources conditions and development modes;
4) Evaluation of coal resources and its associated minerals;
5) Economic benefit evaluation of coal resources development.
The above classification basically summarizes the content in the field of coal resource evaluation, which has certain guiding significance for coal resource evaluation.
Second, the comprehensive evaluation of coal resources
The essence of comprehensive evaluation is to extract its essential attributes from the subject of the evaluated object and transform them into quantifiable value scales to measure the state or behavior of the evaluated object. If the comprehensive evaluation of mineral resources is regarded as a system, then the basic elements of this system will be evaluation objects, evaluation objectives, evaluation models (including evaluation index system and evaluation mathematical methods), evaluation groups and their preferences. After determining the evaluation object (the discovered unexploited coal resources in waida) and the target (the availability of development and construction), it will be the key to ensure the scientific, practical and credible evaluation results by correctly selecting the evaluation method model, organizing a reliable evaluation team and integrating their preferences.
There are many mathematical methods used in comprehensive evaluation, such as weighted summation method, fuzzy mathematics method, grey system method and analytic hierarchy process. These methods have their own characteristics and limitations, so it is not comprehensive to choose a single method as the method model of coal resources comprehensive evaluation system.
Evaluation index is the reflection of the essential attribute of the evaluation object and the basis of the evaluation behavior process. The essential attribute of coal resources is abstract, and the main part of its multi-attribute field can only be described with limited indicators, and an approximate expression can be made. Each evaluation index has a different position in the evaluation process (table 14- 1), that is, its importance is different, so it is necessary to determine the weight of the index in the evaluation process. Therefore, the reasonable selection and setting of evaluation index and the correct determination of evaluation index weight will directly affect the evaluation process and evaluation effect. In order to comprehensively and essentially reflect the essential attributes of the evaluation object, the principles of systematicness, operability, universality and the combination of qualitative and quantitative should be considered when establishing an evaluation index system composed of evaluation indexes and their weights, so as to achieve concise, practical and relatively reasonable results.
Three. Overview of evaluation methods
The development of any science and method has gone through the development process from qualitative to semi-quantitative and quantitative. Quantification is an inevitable trend, so is the evaluation of mineral resources. Whether it is geology, mining technical conditions or economic evaluation, it is from early subjective evaluation and expert experience qualitative evaluation, to qualitative and semi-quantitative comprehensive evaluation of objective indicators, and finally to the highest level comprehensive principle evaluation of objective indicators. In this development process, the evaluation method has changed from simple to complex, from extensive to fine, and the objectivity, rationality and scientificity of evaluation have been continuously improved.
Table 14- 1 Comprehensive Evaluation System of Coal Resources and Characteristic Classification Standard
(According to Mao Jiehua et al., 1999)
When constructing a scientific and reasonable evaluation system, it is the main basic work and key to organize a reliable evaluation team, establish a reasonable index system and choose a reasonable method model. Among them, the index system and method model are the most important.
At present, AHP, weighted average method, cluster analysis method, neural network, grey theory, fuzzy comprehensive evaluation method, fuzzy cluster analysis method and grey cluster analysis method are usually used to establish index system and method model. Different methods have different functions, characteristics and scope of application. Because the above methods involve a lot of operations, the application of computer technology becomes inevitable. There are many available visual programming languages, such as Visual Basic and Visual C ++.
The evaluation of coal resources needs the support of a large number of basic data, so it is also inseparable from database tools. At present, the common visual database software is Visual FoxPro. The software has powerful project and data management functions and convenient application development capabilities, but its biggest defect is that the graphics function and spatial data function are extremely poor, and it is difficult to realize the scientific management of most coal resources evaluation data with spatial characteristics and a large number of maps representing evaluation results. In contrast, Geographic Information System (GIS) is the best choice for data processing of coal resources evaluation.
GIS is the product of the information age. It can not only store, analyze and express the attribute information of various objects in the real world, but also deal with their spatial positioning characteristics, organically combine their spatial and attribute information, query, retrieve and analyze real objects from both spatial and attribute aspects, and express the results vividly and accurately in various intuitive forms. At present, GIS is widely used in natural resource management, urban and regional planning, mapping, municipal facilities management, land use, environmental protection, electric power, communication, transportation, petroleum, education and other fields (Zhang Dashun et al., 1994).
As an advanced computer application program, the application of GIS in the comprehensive evaluation of coal resources will inevitably make the evaluation work start from a higher starting point, which will not only make the evaluation work in line with international standards, but also make the evaluation results more accurate, intuitive and easy to operate.