scholarly journals MODELING OF STABILITY OF SIDE ROCKS IN A COAL MASIFWITH DIFFERENT METHODS OF SUPPORT THE WORKINGS

2021 ◽  
Vol 37 (3) ◽  
pp. 28-34
Author(s):  
V. Yu. Dovhal
Keyword(s):  
Static Field ◽  
Rock Massif ◽  
Shear Stresses ◽  
Support Structures ◽  
Coal Seams ◽  
Rock Stratum ◽  
Static Loads ◽  
Flexible Support ◽  
Coal Rock ◽  
The Stability

Purpose of work. Determine the conditions of the side rocks stability in a coal massif with different ways of support coal-rock stratum to ensure safe working conditions for miners in the excavation areas of a coal mine with steep coal seams. To achieve this goal, laboratory studies were carried out on models of optical and equivalent materials. The modeling of the stability of side rocks in a coal-rock massif was carried out with the methods of support roadways with vertical timber setsand wooden crib supports: 4-point chock.On models made of optical materials in the analysis of the static field of the distribution of shear stresses in side rocks, the regularity of the change in hazardous manifestations of rock pressure, depending on the deformability of support structures, was recorded. On equivalent models of support structures, the deformation characteristics of experimental samples were determined and their effect on the integrity of the roof under the action of static loads was established. When using rigid support structures in the form of vertical timber sets made of wooden racks to protect sliding drifts, there is a deterioration in the stability of side rocks and destruction of the roof. When using flexible support structures in the form of wooden crib supports: 4-point chock, a smooth deflection of the roof and its integrity are observed. A decrease in the size of the stress concentration zone in the model of a coal-rock massif with workings after the compaction of flexible support structures located above the haul roadway, due to a change in their rigidity, when as a result of the convergence of side rocks, a smooth deflection is provided and the movement of the roof is limited. To ensure the stability of side rocks and development workings, as well as reduce the level of injuries of miners from landslides and collapses in the excavation areas of coal mines that develop steep seams, it is advisable to use flexible support structures, when using which, a smooth deflection of side rocks and their integrity in the mined-out area is ensured coal massif.

scholarly journals Determination of Water-Proof Coal (Rock) Pillar Height in Mining Coal Seam Group under Water-Bearing Rock Stratum

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Feng Wan ◽  
Hongqing Zhang ◽  
Peijun Zhou ◽  
Jie Guo
Keyword(s):  
Fracture Zone ◽  
Coal Seams ◽  
Rock Stratum ◽  
Pillar Height ◽  
Rock Pillar ◽  
Maximum Value ◽  
Coal Rock ◽  
Mining Coal ◽  
Water Proof

In order to determine the reasonable height of water-proof coal (rock) pillar when mining multiple coal seams under aquifer, this paper analyzes the expansion height of water-conducting fracture zone when coal seams mining. Considering the expansion law of water-conducting fracture zone in coal seams mining, two schemes of coal seams mining in upper and lower groups and one-time mining of all coal seams are designed for comparative analysis, and the height of water-proof coal (rock) pillar is determined based on the expansion height of water-conducting fracture zone. The results show that the height of water-proof coal (rock) pillar is calculated as 91.08 m when mining upper and lower groups and 105.46 m when mining all coal seams at the same time. According to UDEC numerical simulation results, the height of water-proof coal (rock) pillar is 56.08 m when mining upper and lower groups and 86.36 m when mining all coal seams at the same time. Comparing the results of theoretical calculation and numerical analysis, the maximum value is selected as the final result, and the reasonable water-proof coal (rock) pillar height is determined to be 105.46 m.

scholarly journals Predicting the producing well stability in the place of its curving at the underground coal seams gasification

2019 ◽  
Vol 123 ◽  
pp. 01019 ◽  
Author(s):  
Mykhailo Petlovanyi ◽  
Vasyl Lozynskyi ◽  
Pavlo Saik ◽  
Kateryna Sai
Keyword(s):  
Stress State ◽  
Coal Seam ◽  
Rock Massif ◽  
Curvature Radius ◽  
The Finite Element Method ◽  
Gas Generator ◽  
Coal Seams ◽  
Efficient Operation ◽  
Gas Generators ◽  
The Stability

The relevant issues have been studied of ensuring the stability of producing wells in the place of their curving when uncovering the mining extracted area for the underground gas generator operation. It is emphasized that the design planning of efficient operation of underground gas generators in downhole gasification technology is impossible without consideration of the stress state of the rock massif, which can lead to a danger of the wellbore cutting and emergency shutdown of the technological system operation. The parameters of geomechanical models have been developed and substantiated for the study of the stress state of the “rock massif – producing well” system under the conditions of the Lviv-Volyn coal basin. A computer simulation has been performed of change in the stress state of a laminal massif around a well with a curvature radius in the range of 5 – 25 m with the use of the finite element method. The exponential function has been revealed of the tensile stresses value in the roof of the seam from the angle of the producing well entry into the coal seam. It is recommended the rational angle of a well entry into the coal seam, which is in the range of 21 – 28 degrees, and an appropriate curvature radius will be 5 – 10 m.

scholarly journals The influence of the rigidity of mining security structures on the stability of side rocks in the coal-rock massif

2021 ◽  
Vol 3 (1(59)) ◽  
pp. 19-22
Author(s):  
Anton Korol
Keyword(s):  
Flexural Rigidity ◽  
Compressive Load ◽  
Rock Massif ◽  
Crushed Rock ◽  
Original Material ◽  
Dimensionless Stress ◽  
Coal Rock ◽  
Mine Workings ◽  
The Stability ◽  
Stratified Rock

The object of research is the processes of controlling the state of side rocks to prevent the collapse of the stratified rock strata in the coal-rock massif containing the workings. The studies carried out made it possible to establish the influence of the rigidity of the guard structures of mine workings on the stability of side rocks in the coal-rock massif. It is proved that as a result of the action of an external compressive load on the supporting lateral rocks, the structure, in the form of a model of bunches made of wooden posts, increases its rigidity until the destruction of the security structure. After that, there is an increase in the convergence of side rocks and their destruction. The change in the stiffness of the crushed rock in the filling massif model, which is used to support the lateral rocks, occurs as a result of the compaction of the original material. This is due to repackaging of crushed rock fractions of different sizes and its additional grinding. As a result of this interaction of the side rocks with the filling massif, the integrity of the roof and soil is ensured and convergence is limited. To assess the stability of side rocks, it is proposed to use a dimensionless stress concentration factor k. This coefficient takes into account the rigidity of the guard structures of the mine workings and the flexural rigidity of the side rocks. It was found that when the values of the coefficient k are close to zero (k→0), there is a loss of stability of the guard structures of mine workings and the destruction of side rocks in the coal-rock massif. The preservation of the integrity of the side rocks and the stability of security structures is ensured at values of k>0.1, which corresponds to the parameters of the pliable supporting structures. Most favorably on the condition of side rocks in the coal-rock massif is influenced by the method of backing up the mined-out space of crushed rock. The use of this method excludes the collapse of side rocks. When solving the problem of stability of mine workings at the stage of making technical decisions, it is necessary to predetermine the issues of rigidity of security structures with deformation characteristics of side rocks.

THE ESTABLISHMENT OF DYNAMIC PARAMETERS OF THE ZONE OF LIMIT STATE OF COAL-ROCK MASSIF

2019 ◽  
pp. 34-40
Author(s):  
А. Molodetskyy ◽  
◽  
О. Gladkaya ◽  
V. Slyusarev ◽  
◽  
...  
Keyword(s):  
Limit State ◽  
Rock Massif ◽  
Dynamic Parameters ◽  
Coal Rock

Analysis the characteristic of energy and damage of coal-rock composite structure under cycle loading

2021 ◽  
Author(s):  
Tan Li ◽  
Guangbo Chen ◽  
Zhongcheng Qin ◽  
Qinghai Li
Keyword(s):  
Cyclic Loading ◽  
Elastic Energy ◽  
Composite Structure ◽  
Calculation Method ◽  
Composite Structures ◽  
Damage Variable ◽  
Dissipated Energy ◽  
Height Ratio ◽  
Coal Rock ◽  
The Stability

Abstract The stability of coal-rock composite structures is of great significance to coal mine safety production. To study the stability and deformation failure characteristics of the coal-rock composite structure, the uniaxial cyclic loading tests of the coal-rock composite structures with different coal-rock height ratios were carried out. Lithology and coal-rock height ratio play an important role in the energy dissipation of coal-rock composite structures. The higher the coal-rock height ratio, the greater the average elastic energy and dissipated energy produced per cycle of coal-rock composite structures, the smaller the total elastic energy and dissipated energy produced in the process of cyclic loading. Based on the difference of damage variables calculated by dissipative energy method and acoustic emission method, a more sensitive joint calculation method for calculating damage variable was proposed. The joint damage variable calculation method can more accurately and sensitively reflect the damage of coal-rock composite structure under cyclic loading. The macroscopic crack first appears in the coal specimen in the coal-rock composite structure, the degree of broken coal specimens in the composite structure is inversely proportional to the coal-rock height ratio. The strength and deformation characteristics of the coal-rock composite structure are mainly affected by coal sample in the composite structure.

scholarly journals Soil-Root System Withholding Strength for River Bank Stability

2016 ◽  
Vol 77 (1) ◽  
Author(s):  
IR. PROF. DR RUSLAN HASSAN HASSAN ◽  
Ding Ibau
Keyword(s):  
Relative Strength ◽  
Shear Stresses ◽  
Strength Increase ◽  
Maximum Displacement ◽  
River Bank ◽  
Slope Stabilisation ◽  
Shearing Resistance ◽  
The Stability ◽  
Direct Shear Apparatus ◽  
Riverbank Restoration

The ability of vegetation to stabilise soils is frequently employed in slope stabilisation projects including riverbank restoration activity. Soil block samples permeated with roots of Bermuda Grass commonly used for remediation and riverbank restoration were tested in a direct shear apparatus. Shear stress results of rooted soils were compared with results of un-vegetated soil bloc—s with similar soil types. The increase of shear strength was determined by comparing shear stresses at speciic horizontal displacements. The relative strength increase at the same displacement was 27.3 kPa compared to 19.1 kPa for un-vegetated soil at a displacement of 13.3cm (Location 3). The relative strength increase at the same displacement of 13.3cm was 43.5% for Location 1 and 42.4% for Location 2. The shear stresses in most of the blocks with roots were still increasing at the end of the test (maximum displacement of about 15cm). These conservative root biomass values and the shearing resistance obtained can be used in the assessment of the stability of the existing vegetated slopes and in the design of vegetated riverbanks.

scholarly journals Surrounding Rock Movement of Steeply Dipping Coal Seam Using Backfill Mining

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Wenyu Lv ◽  
Kai Guo ◽  
Jianhao Yu ◽  
Xufeng Du ◽  
Kun Feng
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Surrounding Rock ◽  
Maximum Deflection ◽  
Coal Seams ◽  
Physical Similarity ◽  
Working Face ◽  
Rock Structure ◽  
Backfill Mining ◽  
The Stability

The movement of the overlying strata in steeply dipping coal seams is complex, and the deformation of roof rock beam is obvious. In general, the backfill mining method can improve the stability of the surrounding rock effectively. In this study, the 645 working face of the tested mine is used as a prototype to establish the mechanical model of the inclined roof beam using the sloping flexible shield support backfilling method in a steeply dipping coal seam, and the deflection equation is derived to obtain the roof damage structure and the maximum deflection position of the roof beam. Finally, numerical simulation and physical similarity simulation experiments are carried out to study the stability of the surrounding rock structure under backfilling mining in steeply dipping coal seams. The results show the following: (1) With the support of the gangue filling body, the inclined roof beam has smaller roof subsidence, and the maximum deflection position moves to the upper part of working face. (2) With the increase of the stope height, the stress and displacement field of the surrounding rock using the backfilling method show an asymmetrical distribution, the movement, deformation, and failure increase slowly, and the increase of the strain is relatively stable. Compared with the caving method, the range and degree of the surrounding rock disturbed by the mining stress are lower. The results of numerical simulation and physical similarity simulation experiment are generally consistent with the theoretically derived results. Overall, this study can provide theoretical basis for the safe and efficient production of steeply dipping coal seams.

Stability of Flexibly Supported Oil Journal Bearings Using Non-Newtonian Lubricants: Linear Perturbation Analysis

2000 ◽  
Vol 123 (3) ◽  
pp. 651-654 ◽  
Author(s):  
K. Raghunandana ◽  
B. C. Majumdar, and ◽  
R. Maiti
Keyword(s):  
Power Law ◽  
Perturbation Analysis ◽  
Perturbation Technique ◽  
Stability Margin ◽  
Journal Bearings ◽  
Diameter Ratio ◽  
Linear Perturbation ◽  
Flexible Support ◽  
The Stability ◽  
Power Law Index

The purpose of this paper is to study the effect of non-Newtonian lubricant on the stability of oil film journal bearings mounted on flexible support using linear perturbation technique. The model of non-Newtonian lubricant developed by Dien and Elrod is taken into consideration. The dynamic co-coefficients are calculated for different values of power law index and length to diameter ratio. These are then used to find stability margin for different support parameters to study the effect of the non-Newtonian lubricant.

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