Investigation on Failure Characteristics of Coal Seam Floor in Paste Filling Working Face

Water inrush disasters are extremely prone to occur if the coal seam floor contains a confined aquifer. To find out the failure behavior of coal seam floor of paste filling working face, a beam-based theoretical model for the floor aquifuge was built, and then, the water inrush risk was evaluated based on the thickness of floor aquifuge. Next, the floor failure characteristics of the paste filling face was numerically studied and the effects of the filling interval and long-term strength of the filling body on the floor failure depth, stress and displacement distributions, and plastic zone were explored. The results showed that the theoretical model for evaluating the safety of the floor of the paste filling face based on the empty roof distance is proved to be consistent with that of the empirical formula judged based on the assumption that the paste filling working face was regarded as a cut hole with a certain width. The filling interval has a significant effect on the stress concentration of the surrounding rock, failure depth of floor, and roof-floor convergence. The smaller the filling interval is, the smaller their values are. When the filling rate is 98%, the long-term strength of the filling body is 5 MPa, and the floor failure depth is not more than 4 m. In contrast, the strength of the filling body has no obvious influence on the floor failure depth, but it has a certain impact on the roof-floor convergence. From the perspective of reducing floor failure depth, there is no need to increase the long-term strength of backfill, but it is necessary to increase the early strength of backfill so as to reduce the width of the equivalent roadway.

Control of Water Inrush from Longwall Floor Aquifers Using a Division Paste Backfilling Method

Aiming at the problem of the safety mining problems of longwall paste filling working face under buildings on high confined water in the Daizhuang Coal Mine, the paste filling mining method was used. A series of theoretical analyses, numerical simulations, and field measurements were applied. The results showed that when the filling interval of the working face increases from 1.2 m to 3.6 m, no significant change is found in the depth of the perforated plastic zone of the floor strata. According to the types of water-conducting cracks in the floor strata of the working face 11607, the floor strata are divided into the floor intact area, the structure developed area, and the floor weak area. Based on that, the measures for preventing and controlling the floor failure in the paste filling working face are proposed. Furthermore, the failure depth of the floor of the test working face was detected by the on-site water injection method, and the results showed that the maximum failure depth of the floor of the test working face was about 3 m.

Research on Characteristic Recognition and Dangerous Prevention While Mining through Collapse Column of Pansan Minefield,China

In order to find out the characteristics of geological isomer exposed in the mining process of 12318 working face in Pansan Mine and grasp its influence law on subsequent coal seams mining, the isomer was firstly determined as the collapse column by means of 3D seismic, transient electromagnetic detection, SYT detection and other methods, and its development characteristics, conductivity and water enrichment were identified.Then FLAC3D numerical simulation software was used to analyze the characteristics of vertical stress and plastic failure zone in different coal seams during mining.Finally, by comparing the ultimate failure depth of floor and the thickness of waterproof layer in the process of each coal seam directly pushing through the collapse column, the risk of water inrush and the prevention are analyzed.The results show that the exposed geological isomer is characterized by weak water-rich collapse column.Under the influence of the mining of the previous coal seam and the activation of the collapse column, the subsequent coal seam is in the low stress area before mining, which increases the floor failure and causes the activation of the collapse column more easily during mining.Coal 5# and 4# can be directly pushed through the collapse column, and coal pillar of sufficient width should be left for coal 1# to prevent the collapse column from activating water inrush.

Effect of Crack Propagation on Mining-Induced Delayer Water Inrush Hazard of Hidden Fault

Hidden faults in deep coal seam floor threaten the exploitation of coal resources. Under the influence of mining and water confined in the floor, the cemented filler in the hidden fault will be eroded by water flow, in order to investigate the fracture characteristics and water inrush risk of hidden faults in floors above confined aquifer. Using the 27305 working face as geological background, the influence of the seepage scouring filler on the mechanism of water inrush from hidden faults was assessed by developing a stress-seepage coupling model and employing the finite difference method to simulate the seepage process of hidden faults under the combined action of high ground stress and high confined water. The evolution of seepage, shear stress, and plastic zone was also assessed. The influence of the hydraulic pressure of the aquifer and the thickness of a waterproof rock floor on the formation of the water inrush pathway was analyzed. Results indicate that (1) under the influence of mining, the hidden fault experienced the change process of stress stability, stress concentration, and stress release. The shear stress increases first and then decreases. The compressive stress decreases gradually due to stress release. (2) Water inrush disaster will not occur immediately when the working face is above the hidden fault. The delayed water inrush occurs in the mined-out area when the working face advances to 160 m, the floor failure zone is connected with the hidden fault failure zone, and the delayed water inrush channel is formed. (3) With the mining advances, the water pressure of aquifer is the same. The larger-angle fault leads to the thinner thickness of floor aquifer. The greater the influence of hidden fault on coal seam mining, the higher the danger of water inrush.

Mechanical Analysis of the Failure Characteristics of Stope Floor Induced by Mining and Confined Aquifer

Mining above confined aquifer has become an important task for water inrush prevention in China. To study the failure characteristics of stope floor along the strike, a mechanical model under combined action of mining and confined aquifer was constructed, and the distribution of vertical stress, horizontal stress, and shear stress was obtained. Based on the Mohr–Coulomb criterion, the failure range of the floor is determined and verified by the in situ test. The results indicate the following. (1) Both vertical stress and horizontal stress in the stope floor take the junction of stress increasing area and stress decreasing area as the dividing line, forming two groups of “convex arches” at the solid coal side and the goaf side, respectively. (2) The vertical stress gradient in the solid coal side is significantly higher than that in the goaf side, while the horizontal stress gradient in the solid coal side is similar to that in the goaf side. The shear stress distribution is divided into three regions by the boundary between positive and negative shear stress, which makes the stope floor in this area to show compression shear or tension shear failure. (3) According to the in situ test, the maximum floor failure depth of 41503 working face is 11.38 m, which is quite close to the theoretical calculation result of 9.68 m. (4) Applying the mechanical model to five other coal mines with different mining conditions and stress states, the maximum absolute error between the measured and theoretical values of floor failure depth is 1.1 m, the average absolute error is 0.8 m, the maximum relative error is 8.2%, and the average relative error is 6.5%. The study provides a certain mechanical basis and reference for the floor failure mechanism induced by mining and confined aquifer.

Physical Modeling of Floor Failure Above Confined Water: A Case Study in China

Coal mining in areas with deep confined water is very dangerous; to ensure safety, it is necessary to clarify the damage characteristics of the working face floor. To directly reflect the failure characteristics of the working face floor under the coupled effects of mining stress and confined water pressure, this study takes the II633 working face of the Hengyuan coal mine in the Huaibei mining area as the engineering background. With the use of a self-designed monitoring system for confined water diversion and a similar material simulation experimental method, the mining stress distribution patterns, the deformation and failure characteristics of the overburden, and the diversion characteristics of the confined water in the working face floor are studied. The combined use of a confined water loading system and a confined water lifting system can directly reproduce the floor confined water lifting characteristics affected by floor failure during coal mining. The results show that the floor undergoes three stages of deformation in the horizontal direction: premining stress concentration compression (10-15 m ahead of the working face), postmining floor pressure relief expansion, and roof collapse stress recovery (the distance of the lagging working face is 15-20 m). In the vertical direction, a soft rock layer blocks the continuous transfer of mining stress to deeper layers and produces an important cushioning effect. In the process of coal mining, shear cracks easily develop in the coal wall in front of and behind the working face. After the coal seam is excavated, the length of the fractures that develop in the model is 27 cm. The confined water loading system can visually reproduce the hydraulic characteristics of the confined water during the mining process; that is, the confined water easily bursts at the front and back ends of the coal wall in the goaf. The error, as determined by comparison between the field measurement and the theoretical calculation results, is only 0.617 m, verifying the reliability of the similar simulation method.

Predictors of genitourinary syndrome in women of elderly reproductive age after hysterectomy

The article presents an analytical assessment of risk factors for distant postoperative urogenital disorders in women of older reproductive age after radical surgical treatment for uterine fibroids. The aim of the study was to optimize the diagnostic algorithm of genitourinary syndrome in women of older reproductive age after hysterectomy for uterine fibroids. Materials and methods – 80 women aged 40 to 50 years were examined: 40 patients after vaginal and laparoscopically assisted vaginal hysterectomy, 40 patients with abdominal hysterectomy, control – 30 relatively healthy women with asymptomatic fibroids. The examination was performed at the stage of preoperative observation and for 3 years after surgery. Research methods: data on the assessment of pelvic floor and urogenital dysfunction using a standardized POP-Q system, physical examination, the ICS classification was used to assess the severity of urinary incontinence; quality of life assessment using the MOS SF-36 questionnaire; standard methods of variation statistics. Research results and their discussion. The most important risk factors for genitourinary syndrome have been identified. These included obstetric and gynecological history (birth of large fetuses, episiotomies, birth trauma, high birth parity, ovarian surgery, the use of gonadotropin-releasing hormone agonists), chronic diseases accompanied by increased intramuscularly; the presence of stigmas of undifferentiated connective tissue dysplasia; clinical manifestations of pelvic floor failure and functional disorders of the urethral sphincter. Conclusions. In the case of surgical treatment of uterine fibroids, it is advisable to take into account not only the presence of vaginal prolapse and initial dysuric manifestations, but also their predictors in the preoperative stage of the examination, as this may affect the choice of method and access in the case of surgical treatment of uterine fibroids. rehabilitation program and will obtain the expected effect of surgical recovery.

Urogenital disorders in women of reproductive age after radical surgeries about uterine myoma – optimization of diagnostic algorithm

The article presents an assessment and analysis of the most important medical and social risk factors for long-term postoperative urogenital disorders in women of reproductive age after radical surgical treatment for uterine fibroids. Radical operations for uterine fibroids cause an increase in the proportion of urogenital disorders, the clinical manifestations of which have a negative impact on the physical, psycho-emotional form and social significance of women in society. A survey of 80 women aged 40 to 50 years, the main group included 40 patients who underwent vaginal hysterectomy, the comparison group consisted of 40 patients with hysterectomy performed by abdominal access. Data on the assessment of pelvic floor condition and urogenital dysfunction using a standardized POP-Q system, both at the stage of preoperative observation and for 3 and 5 years after surgery. Сonducted surveys, filling diaries of pain, urination, physical examination and bimanual examination, determination of the pH of the vaginal contents, colposcopy, evaluated the index of the vaginal condition, the state of the microbiota of the mucous membranes, a comprehensive urodynamic examination, cystometry, ultrasound examination of the pelvic organs and assessment of ovarian structure.The most important risk factors are identified, which would allow to form groups of patients that require individualized approaches in the choice of surgical techniques and rehabilitation program. These included obstetric and gynecological history (birth of large fetuses, episiotomies, birth injuries, high birth parity); ovarian surgery, the use of gonadotropin-releasing hormone agonists. chronic diseases of the respiratory system and gastrointestinal tract, accompanied by increased intra-abdominal pressure; the presence of stigmas of undifferentiated connective tissue dysplasia; clinical manifestations of pelvic floor failure and functional disorders of the urethral sphincter. When choosing a method and access in case of surgical treatment for uterine fibroids, it is advisable to take into account the presence of pelvic prolapse and initial dysuric manifestations in women, the functional state of the sphincter apparatus and urethral hypermobility, obstetric and gynecological pathology and previous surgery on the organs of the uterus. the patient, her awareness of possible complications, the surgeon’s experience and his choice of surgical techniques.