Water-flowing Fractured Zone Research Articles

Height of the Water-Flowing Fractured Zone of the Jurassic Coal Seam in Northwestern China

Research on the height of the water-flowing fractured zone (HWFFZ) is important for mine safety and regional eco-environmental conservation in the Jurassic coal field of northwestern China. Using the Cuimu coal mine as a case study, on-site measurement, mechanical theory calculation, and numerical simulation were used to analyze the regularity of the HWFFZ in this area. A television borehole wall imaging system with a light source allowed us to examine the size and shape of fissures intuitively, allowing the top boundary of the HWFFZ to be determined. Per mechanical theory, the overlying strata in the decreasing stress zone was simplified as a clamped rectangular plate and the formula for calculating HWFFZ was obtained by comparing the value of the ultimate deflection of the thin plate and the height of the free space in the lower part of the stratum. In addition, the dynamic development of the HWFFZ was simulated using realistic failure process analysis software. The unusual characteristics of the HWFFZ were analyzed from two aspects: the inapplicability of the traditional empirical formula and the difference of the overlying strata structure of the Jurassic and the Carboniferous Permian coalfields. These strata can be divided into layered and integrated strata in the Jurassic coalfield.

Evolution mechanism of water-flowing zones and control technology for longwall mining in shallow coal seams beneath gully topography

The height and evolution mechanism of fractured water-flowing zones are of great importance for prevention of water inrush disasters and protection of immediate environments, particularly in ecological vulnerable areas. In this paper, comparative approaches including empirical formula calculation, physical simulation, numerical simulation and PROTEM transient electromagnetic analysis are employed to identify the development of the fracture zones caused by water-flowing so as to ensure mining safety and protection of groundwater in shallow coal seams beneath gully topography. An empirical formula was used to calculate the height of the water-flowing fracture zone, and an experimental study utilizing a model based on a similar material was adopted to analyze the movement and fracture development of the overlying strata. Results provide a reasonable basis from which a rational mining height may be determined. The PROTEM transient electromagnetic apparatus was employed to detect the water-flowing structure conductivity of the overlying strata induced by mining beneath gully topography in the field. The water-flowing fracture of the overlying strata can be estimated according to comprehensive analysis of the apparent resistivity changes of the field, gully surface crack development and aquifer water level. Accordingly, the control technologies in the field were implemented and discussed regarding preventing gully water from rushing into underground mining spaces through water-flowing fracture zones. Results indicate that safe and efficient mining of shallow seams beneath gully topography can be achieved by prevention of gully accidents and protecting the surface water resources of the ecological environment.

Research on the Height of Water-Flowing Fractured Zone under the Weak Roof Strata and Fully Mechanized Caving Condition

The first working face production has suspend because of the great roof water inrush in Mindongyi coal mine, which has weak roof strata and mining use the fully mechanized caving method. In order to detect the height of water-flowing fractured zone, loses of drilling fluid observation method has carried on the flied test, the results showed that while the full-mechanized caving mining thickness is 7.7 m, the height of water-flowing fractured zone is 79.78 m, and the ratio of height to thickness is 10.36, meanwhile, the numerical simulation and similar material simulation have proved the test results are correct. The study enriched the domestic research fruits of the height of water flowing fractured zone, and provided technical references for Mindongyi coal mine mining.

Research on the Influence by Different Dip Angles Faults of the Damage Height of Superincumbent Stratum

For the issue of fault impact on the height of water-flowing fractured zone, the study worked out several damage heights of superincumbent stratum under the influence of different dip angles faults. The research shows that small angle fault influence area is apt to develop a wide range of the plastic zone,and the water-flowing fractured zone of high-angle fault influence area is apt to increase along the fault surface and breakover the aquifers of coal seam roof and floor.

The Numerical Simulation of Overburden Strata Failure Law by Full-Mechanized Caving Mining in Extra Thick Coal Seams

Given the irrationality and limitations in thick coal seam of the empirical formula of height of water flowing fractured zone , this article reveals the special thick seam fully mechanized mining damaging rules of overlying rock and determines the height of water flowing fractured zone with 3D finite element numerical simulation,according to the complex geological conditions and the special thick seam fully mechanized mining methods of Laohutai ore mining working face E5400 as an example. Results show that the destruction of repeated mining area of the overlying rock will have superposition effect and the superposition effect will increase with the development of mining; the fracture sharp of water fracture zones is in close proximity to the "arch". Simulation results and the actual detection height fitting is better, so it assesses the range of overburden water flowing fracture zones and rationality of the height.

Numerical Simulation Analysis of Coal Mining with Paste-like Backfill under Water Based on UDEC

Based on the instance of extremely thick coal seam mining under aquifer in Gonggeyingzi Coal Mine, the theoretical calculation for the height of water flowing fracture zone in this coal mine was 30.6m and calculation model was established. Analyzed by the UDEC software, the surface displacement of backfill mining was 1532mm and the height of overburden rock plastic zone was 36.5m. Compared with 135m away from coal roof to aquifer, slicing backfill mining under aquifer was confirmed to be safe and feasible based on the theoretical calculation and analysis of UDEC. The results provided the basis for the safety of extremely thick coal seam mining under aquifer in this coal mine.

Development Rule of Full-Mechanized Caving Mining Water-Flowing Fracture Zone in Yanzhou Mining Area

The heights of fully-mechanized mining water-flowing fracture zone of Yanzhou mining area were measured by borehole simple hydrology method .In order to confirm the influence degree of the geology and mining factors to the damage height of overburden rock , the paper analyses the measured data by using grey relation analysis theory, and concludes that the face span, mining thickness and mining depth are main influence factors to the height of the water-flowing fracture zone. On this basis, the paper reveals the general rules of fully-mechanized caving mining overburden rock destruction with the on conditions of gentle dip, thick coal seam and hard and medium hard roof by using regression analysis method.

Numerical Simulation of Failure of Overburden in Coal Mining under Reservoir

The Water-flowing fractured zone’s height and its distribution has an important effect on stability of the surrounding rock and the safety in the subsequent production under reservoir. In the paper the Drucker-Prager yielding law is used. The limit value of tensile stress and shear stress is used to judge the water-flowing fractured zone’s height and its distribution. The fitting formula is obtained by origin software under different advance of the work face. The peak value of horizontal movement is 1.13m. The symmetrical subsidence basin is formed in the center of work face. The peak value of subsidence is 3.86m. The sum of surface subsidence accounts for about 43 percent of the mining height. The advance of around 300m is the distance that the water flowing fractured zone’s height reaches the highest value. The biggest height of water- flowing fractured zone is 146m.

Forecasting of destroyed height of overlying rock with the top coal caving based on ANN

Analyzed the rule of the Water Flowing Fractured (WFF) zone’s development during the fully mechanized top coal caving. Six influence factors of WFF’s height were selected, viz. mining thickness, base rock thickness, dip angle, uniaxial compressing strength of roof, mudstone proportion in overlying rock, and structure of overlying rock. The height-forecasting model of WFF was established based on the Artificial Neural Net-work techniques, and was applied in the first fully mechanized top coal caving face under sea in China.