Effect Of The Disturbance By Underground Coal Mining On Soil Key Physical Properties

Ecological environment is fragile in arid and semi-arid areas of the western region of China. Ecological environment problems are even more highlighted after being disturbed by human beings, such as mining and so on. As the carrier of vegetation, soil has an important influence on animal, microorganism, climate and other ecological factors. Therefore, it has great practical significance to explore the influence of mining on soil physical properties.At present, few scholars have explored the influence of mining on soil physical properties from the perspective of indoor physical simulation. According to the theory of similarity and mining subsidence, the similarity criteria and similar constants of physical simulation for the influence of mining on soil physical properties were derived. Besides, the key dimension parameters, mining method and dynamic support of the similar device are designed, which provides a three-dimensional physical simulation platform for the physical simulation test of the influence of mining on soil physical properties.In order to realize the similarity of soil layer, overburden similar materials and material laying mode were selected in this thesis. An indoor physical simulation data acquisition method, used the comparison between control group and the experimental group to reduce the boundary effect, and calculation rules of horizontal deformation of soil sampling method were proposed. The reasonable similarity of the change of soil physical properties caused by mining subsidence was analyzed from the influence scope of the subsidence, the horizontal movement and deformation of the main section and the horizontal deformation angle of mining influence range.The disturbance of soil water content and bulk density of soil was found to have spatial partition characteristics from the similarity simulation test and field soil sampling test of the soil physical properties. Coal mining could decrease the soil water content in tension and compression zone and the soil bulk density in tension zone, and the dispersion degree of soil water content and soil bulk density in the compression zone and tensile zone were increased.According to physical simulation experiment, changes of soil water and soil horizontal deformation in compression zones appears as positive correlation. Changes of soil water and soil bulk density have negative correlation with soil horizontal deformation in tension zone, and these coefficients of determination are higher than 0.39, which means it is reliable. The reducing of soil water in compression and tension zone, resulting from mining, is more and more obvious. And the changes of soil water in compression zone is more sensitive to the surface horizontal deformation than the changes in tension zone.According to the spatial comparisons between soil physical properties before and after mining, mining disturbance on soil water content, internal friction angle and cohesion appears regularities in spatial distribution. Since soil water content can affect soil cohesion and internal friction angle, cohesion and internal friction angle’s spatial distribution regularities are related with the soil water content’s: in the external tensile zone, mining decreases cohesion; from internal tensile zone to neutral zone, mining decreases soil water content and cohesion more and more, while increases internal friction angle more and more. After mining, the nuggets of soil water content, internal friction angle and cohesion decrease, and the nuggets of organic matter as well as pore space ratio increases, demonstrating mining strengthens soil water content, internal friction angle and cohesion’s spatial dependence and weakens organic matter and pore space ratio’s spatial dependence.According to the results, internal tensile zones, compression zones and neutral zones are the key zones for solving ecological environmental problems; soil water content, cohesion, internal friction angle and bulk density should be focused on to restoration; the relationships among soil physical properties and the relationship between zones should not be ignored.