The roof breaks along dipping weaknesses in the sandstone caused by thin, discontinuous shale laminae. Some sandstone roof falls occur along inclined bedding, such as these examples from the Jellico and Harlan coal beds in eastern Kentucky. Trends: Local falls in sandstone generally occur along bedding weaknesses, which may follow overall bed ...
The mechanical properties and acoustic emission characteristics of thick hard roof sandstone were investigated. Samples were taken from the 30.87-m thick sandstone roof in a mine in the Shengdong coal field, China. Firstly, the composition and microscopic characteristics were analyzed by XRD and FE-SEM, respectively. Moreover, the indirect …
Mining disturbances may cause fissure water in the sandstones of a coal seam roof to link up with the coal seam, further causing changes in the moisture conditions of coal–rock systems such as ...
The roof of the mining seam consisted of four mudstone layers and two thin coal seams (see Fig. 1). This combined roof mudstone-coal formation had a total thickness of approximately 9 m and was generally very weak, with an uniaxial compressive strength (UCS) of 10–20 MPa. Above this formation was a thick and more competent sandstone …
The "rock-gangue" structure refers to the semi-arch structure formed by extruding no caved rock and caved gangue. This structure form is the most common structure form in top coal caving stope, especially when the upper direct roof is sandstone with larger thickness and higher strength, the collapse of which is easy to form bulk …
The coal mine has an annual output of 20 million tons per year, but its thick and hard roof restricts its development. The buried depth of the C1 coal seam is …
The increase in the water-flowing fractured zone and roof caving height caused by coal seam mining had an clear influence on the seepage characteristics of the roof, and the fracturing grouting of ...
The main water filling sources affecting #7 coal mining in the deep Kongzhuang coal mine are sandstone water at the boundary of the Lower Shihezi Formation and sandstone fissure water at the roof of the Shanxi Formation. #7 coal roof sandstone fissure aquifer has poor and uneven fissure development, the overall water …
The triaxial compression test was carried out on the 50 mm × 100 mm standard specimen to explore the characteristics of a coal mine roof sandstone. The triaxial compression curve is shown in Figure 4. The uniaxial compressive strength was 131.7 MPa, the elastic modulus was 29.7 MPa, the Poisson's ratio was 0.228, the …
Along with the gradual depletion of high-quality coal resources in eastern China, the focus of coal mining is gradually shifted to the northwest region [1,2].Rich in coal resources, the eastern Ningxia is an important coal production base in China [].However, multi-layered sandstone aquifers are widely distributed in the eastern Ningxia, and their …
200m, but a 30-m thick layer of hard sandstone is present above the roof of the coal seam, resulting in a large periodic pressure step during the mining process. In addition,
The ignition source of gas explosion accident in Babao Coal Mine is not CSC, but seems to be electric sparks generated by the breakage and ionization of premixed gas due to the electricity from the extrusion and collapse of roof sandstone during the periodic weighting, and the location of explosion source might be the goaf of the −4164 …
Another common condition in Fire Clay coal mines is shale roofs with kettlebottoms. Kettlebottoms are isolated, tubular blocks of sandstone or hard shale in mine roofs; …
The more complex the hydrogeological conditions of a mine, the more likely the coal seam is to experience water inrush during the mining process, and the greater the degree of the water inrush hazard. The scientific and reasonable prediction of water inrush in mines with complex hydrogeological conditions is of great significance to the safe and …
2.1 Experiment Design 2.1.1 Specimen Preparation. The sandstone and coal samples in this experiment were taken from the 13 # coal seam of a coal mine in Shanxi Province, China. Coal and rock blocks were removed from a long-wall entry and immediately wrapped with plastic film to ensure freshness and prevent weathering.
Sandstone channels: their influence on roof control in coal mines. Full Record. Related Research. Abstract. The purpose of this report is to familiarize the coal mining industry …
At an underground coal mine in the western U.S., ground control problems and roof falls have occurred in areas where the geological formation in the mine roof consists of a water saturated sandstone unit. This sandstone unit occurs in channels or washouts, due to the depositional environment of the coal and strata beds. It is quite common for the
details went unnoticed until the mine hit a sandstone channel, fault, or poor roof conditions which necessitated the operator to aimlessly turn headings left and right without success until the area had to be abandoned. Other mine operators were made aware of the benefits of underground mapping and geologic forecasting techniques
The basic roof is fine sandstone with a thickness of 3.2 m. The tensile strength of the fine sandstone is 3.2 MPa, ... The influences of coal mining and roof activity on the mine pressure behavior of a …
The electricity generation and discharge characteristics of the roof sandstone of the Renlou coal mine described in Section 3 comprehensively demonstrate that the electrical effect generated by the roof sandstone can ionise the combustible gas and cause a gas explosion. Fig. 12 shows the electric spark generated during the cracking of the ...
The stability of the composite structures formed by coal pillar and roof rock is of great significance to safe production and sustainable development of coal mines. In …
The main water filling source in the mining area is the sandstone fissure aquifer of the 3 coal roof. This aquifer is composed of gray white quartz medium grained sandstone and fine grained ...
In this study, the roof sandstone of the Zhangshuanglou Coal Mine in Jiangsu Province and the roof sandstone of Renlou Coal Mine in Anhui Province were …
roof instability. Therefore, for these mines, studies of roof instability were a natural consequence, although not the original objective. ... sandstone, coal, and some fresh-water limestone lenses found in the upper third of this group. Flint (8) states that the Johnstown limestone is persistent and is used as a stratigraphic guide in Somerset ...
interaction is the immediate roof rock competency (4). The shale unit shown in figure 2 directly above the Eagle Coalbed varies in thickness from 0 to 10 ft. In areas of Harris, this shale unit can either be laminated, sandy, or nonexistent (replaced by a sandstone scour). These fluctuations explain the range in Coal Mine Roof
In Chinese coal mines, roof accidents account for 50 to 55% of injuries each year [1,2,3,4,5]. ... The main roof is 8 m thick and comprised of medium sandstone. The complex roof structure is a typical thin-layered sand-mudstone interbed roadway roof. The immediate floor is 2 m thick and comprised of sandy mudstone, and the main floor is 7 m ...
explore the characteristics of a coal mine roof sandstone. The triaxial compression curve is. shown in Figure 4. The uniaxial compressive strength was 131.7 MPa, the elastic modulus.
Masabattula (2010) showed that sandstone in the immediate roof was responsible for almost 40% of the total reported roof fall incidents in Indian underground coal mines during 1997–2006, whereas shale (a relatively more unsafe roof type) was responsible for comparatively less (nearly 17%) roof falls incidents (Masabuttula, 2010). …
The roof of coal seams are mostly soft rock with weak cementation. To further study the mechanical characteristics and deformation control scheme of the roadway with weakly cemented siltstone as roof, this paper took Linchang coal mine as the research background and adopted field investigation methods, laboratory experiments, …
duce. Roof falls are also one of the more prominent hazards in underground hard coal mines, which has been confirmed by statistical data from hard coal mines in the USA, India and Poland [1–3]. The longwall mining system is the main system used in Poland's hard coal mines. Retreat longwalls with natural roof caving in the gob are the most ...