Research On Mechanical Properties And It's Controlling Factors Of Coal Measures Rocks In The Deep Part Of Huainan Panji Mining Area

As the depth of resource exploration and coal mining increases year by year,mining methods are gradually becoming intelligent,and the requirements for the exploration of deep coal mining geological conditions and the prediction of disaster-causing factors are getting higher and higher.To find out and study the geological conditions of deep coal resources and the physical and mechanical properties of rocks in deep coal measures is not only a major basic scientific problem,but also a practical subject to ensure the sustainable development of China's coal industry.The results can provide more accurate and complete geological basic data for the design,construction and safe production of deep mines,so as to take effective measures and prevention measures in advance to reduce or avoid the occurrence of mine geological disasters.This paper taked the deep exploration area of the Huainan Panji mining area as the research object,closely combined the geological survey and detailed survey engineering of the study area,made full use of the favorable conditions of surrounding production mines,and through the use of drilling data processing,in-situ testing,laboratory tests and theoretical analysis,the in-situ stress and geothermal conditions of deep coal-measure rocks in Panji mining area were determined,and the microcomposition,sedimentary environment and structural characteristics of coal-measure rocks were analyzed,and the mechanical properties of rock under conventional conditions,ground temperature and in-situ stress were obtained,and the differences of rock macroscopic mechanical properties and its main controlling factors were studied,and the geological nature control mechanism of rock mechanical behavior in deep coal measures was revealed.The main achievements are as follows:1)The mineral composition,content,and microstructure of deep coal measures were statistically analyzed by using rock and mineral micro-section identification,image analysis and X-ray diffraction methods,and the microscopic characteristics of different lithological rocks in the study area were obtained.The main mineral of sandstone is quartz,the average content is more than 65%,the structure is mainly pore cementation,and the content and grain size of sandstone debris in different layers are quite different.The content of clay minerals in the mineral composition of mudstone is relatively high,accounting for about 60%,and terrigenous clastic minerals account for about 30%,and the content of each layer is not very different.The content of non clay minerals such as siderite varies greatly in different layers.2)Based on the statistical analysis of the exploration drilling core and logging data in the study area,the lithological type compositions of the roof and floor of the deep main coal seams and the structural characteristics of the rock mass were obtained.On the plane,the roof and floor lithology types of the five main mineable coal seams in the deep part are dominated by mudstone.The thickness of the roof and floor sandstone in the study area gradually increases from east to west,and the mudstone is gradually decreasing.In the vertical direction,the layer with the highest sandstone content is the Lower Permian,which gradually decreases upwards,while the mudstone content is the opposite;the rock quality designation(RQD)and borehole sonic logging can directly reflect the structural characteristics of the deep rock mass.The RQD value of the roof and floor of the coal seam is more consistent with the planar distribution of the borehole logging wave velocity.Near the turning end of the Panji anticline and the fault in the middle of the study area,the RQD value of and logging wave velocity are both small,and the rock quality and rock mass are poor.Far away from large-scale structures and fold areas in the area,the RQD value and logging wave velocity have an increasing trend,and both are affected by the distribution of plane lithology and tectonic effects3)Selected the ground kilometer borehole hydraulic fracturing method and the underground roadway stress relief method to carry out the in-situ stress test in the study area,combined with the interpretation results of the AE method test,the type,magnitude and direction of the current in-situ stress field in the deep study area were obtained.The results show that the maximum horizontal principal stress is between 30?55MPa in the depth range of-1000?1500m,and increases linearly with the increase of depth.The maximum horizontal principal stress is about 1.3 times of the vertical principal stress,revealing that the deep in-situ stress field is dominated by horizontal tectonic stress,and the ratio of maximum to minimum principal stress is between 1.116?2.469,with an average of 1.511,and decreases gradually with the increase of depth.The direction of the maximum principal stress in the study area is NEE direction,which tends to be close to EW direction with the increase of depth.And the current in-situ stress field in the deep is controlled by regional tectonics,and the magnitude and direction of in-situ stress at different positions in the study area are different,which are affected by regional F66 fault and Panji anticline.4)Based on the approximate steady-state borehole temperature measurement data in the Panji mining area,a correction formula for the temperature change of the temperature measurement hole was established,combined with the temperature measurement results of the underground roadway,the simple temperature measurement hole data in the study area was corrected,and the deep ground temperature in the Huainan Panji mining area was obtained.The gradient value varies from 1.52?/100m to 3.41?/100m,with an average gradient of 2.46?/100m.The floor temperature of the main coal seam increases linearly with the increase in depth.Calculated and analyzed the ground temperature distribution at three levels of-1000m,-1200m and-1500m in the study area,and and drawn the corresponding contour map of the ground temperature distribution.5)The mechanical test results of coal measures rocks in the study area under conventional conditions showed that:The mechanical property parameters of rocks with different lithologies are quite different,and the distribution of mechanical parameters of rocks with the same lithology in the same layer is also relatively discrete,and the lithological effects of the mechanical properties of coal measures rocks are obvious.There are good linear relationships between the compressive strength and tensile strength,elastic modulus and cohesion of lithological rocks in the study area.In the vertical direction,the compressive strength of the coal roof and floor sandstones of No.11-2 coal in the Upper Shangshihezi Formation is the highest,and the roof siltstone strength of No.3 coal in the Lower Shihezi Formation is the highest,and the average strength of mudstone in the roof and floor of the main mineable coal seams does not change significantly with the layer positions.6)The triaxial mechanical tests of coal measures rocks under different confining pressures were carried out in accordance with the variation range of deep in-situ stress.The results show that the strength of coal measures rocks increases gradually with the increase of confining pressure,and the increase range is larger at the initial stage and decreases at the later stage within the test confining pressure range.Through regression analysis of the triaxial rock mechanics test parameters of coal-measure rocks,the prediction model of the mechanical strength and peak strain of coal-measure rocks with different lithologies in the deep part of Huainan mining area with confining pressure was established,and based on the analysis of a large number of test results,the lithology influence coefficient of coal measure rocks in the study area was determined.7)Within the range of temperature changes in deep coal measure strata,constant temperature uniaxial compression tests of coal measure rocks under different temperature conditions was carried out.The results show that the influence of temperature on the strength and deformation properties of coal measure rocks is weaker than that of lithology and confining pressure.Mechanical parameters such as uniaxial compressive strength generally show a decreasing trend with increasing temperature.Rocks of different layers and different lithologies are affected differently by temperature.According to the change characteristics of strength with temperature,the mechanical properties of coal measure rocks are divided into three types:type ?-strength decreases with increasing temperature,type ?-unchanged strength fluctuation and type ?-strength increases with temperature8)The influence of factors such as the material composition,microstructure,RQD,borehole logging wave velocity,deep in-situ stress and temperature environment of the roof and floor rocks of the main mineable coal seam in the study area on the mechanical properties of the rocks were analyzed.And clarified the main controlling factors such as sedimentary characteristics,rock mass structural characteristics and confining pressure that affect the rock mechanical properties of deep coal measures,and revealed the geological nature control mechanism of the materiality,structure and occurrence of rock mechanical behavior of deep coal measures.Figure[140]Table[43]Reference[245]...