Experimental Study on the Preparation of Improved Soil Substrate from Coal Gangue

With the continuous development of China’s industry, the disorderly discharge and accumulation of coal gangue in mining areas have become a key ecological problem, which not only occupies a large amount of land, but also causes various pollution phenomena. Therefore, the comprehensive utilization of coal gangue has become a research hotspot in the field of environmental governance. In this paper, by mixing coal gangue and fly ash with straw in different ratios to prepare compound soil substrate and growing lettuce, the effects of different ratios of the three wastes and coal gangue particle sizes on crop growth were analyzed by measuring cotyledon area, plant height and other indexes. The experimental results showed that the best proportion of soil matrix improvement was 42.9% coal gangue, 7.1% fly ash, 10% straw and 40% soil, where the coal gangue particle size proportion was 20% fine particles, 20% medium particles and 60% coarse particles. This experiment mixed coal gangue with typical solid wastes, which will, to a certain extent, solve the problem of solid waste dumping and resource scarcity in China and provide a scientific reference for the comprehensive utilization of the three wastes and the repair of soil in mining areas

Risk Assessment of Compound Dynamic Disaster Based on AHP-EWM

The coal mine in deep mining can easily form a compound dynamic disaster with the characteristics of rock burst and gas outburst. In this paper, the analytic hierarchy process (AHP) and the entropy weight method (EWM) are combined, and the fuzzy comprehensive evaluation (FCE) secondary evaluation model of compound dynamic disaster is proposed to evaluate the risk of compound dynamic disaster, which avoids the problems of the imperfect evaluation index system and strong subjectivity of index weight. Based on the statistical analysis of typical compound dynamic disaster cases in China, three first-level indicators were established, and sixteen second-level indicators were developed. The verification results show that the accuracy and weight are better than the traditional evaluation methods. Combined with geological and mining data, the compound dynamic disaster risk assessment was carried out on the second mining area of mine B, in the Pingdingshan mining area, and the result was grade II (weak risk). Corresponding prevention measures and parameters were implemented, and no compound dynamic disaster occurred during the working face excavation

Analysis of U-Shaped Steel Failure Characteristics in Rock Burst Roadway and Design of Stable Structure and Constant Resistance O-Shed

The U-shaped steel support has good surface protection and is one of the main supporting forms of the roadway under rock bursts. However, in the supporting process of roadways under rock burst, there are poor mechanical properties of lap joints, resulting in a serious decline in the anti-impact performance of U-shaped steel supports. Using a combination of laboratory experiments and theoretical analysis, we study the sliding mechanism of the U-shaped steel bracket’s overlap section bearing and find the key factors affecting the sliding performance of the overlap section. The characteristics of deformation and failure of U-shaped steel supports under impact loads are analyzed by numerical calculations. An improved method for optimizing the sliding performance of the lap section is proposed to provide theoretical support for the design of stable and constant-resistance energy-absorbing O-shed supports. The research results show that the frictional properties between the contact surfaces of the overlapped sections, especially the frictional properties between the contact surfaces of the clamp and the U-shaped steel, determine the sliding characteristics of the U-shaped steel overlapped sections, which are the key factors affecting the bearing capacity of the support. The single-point maximum bearing capacity of the U-shaped steel bracket under the uniformly distributed impact load is basically close to the maximum bearing capacity of the U-shaped steel bracket under the concentrated impact load. When the U-shaped steel bracket is uniformly loaded, its bearing capacity can be increased several times. When a gasket is added between the U-section steel and the clamping bolt in the lap section, the bearing capacity changes smoothly during the sliding process, which greatly improves the friction performance between the contact surfaces, and can greatly improve the overall bearing capacity, energy absorption, and anti-impact performance of the support structure. Based on this, a stable and constant energy-absorption O-type shed structure for the impacted underground roadway in Laohutai Mine was proposed. The field application proved that improving the sliding performance at the joint of the U-shaped steel support can effectively control the deformation of the roadway under the impact load