Roof stability evaluation of large section open-off cut in lower slice of slicing mining

In order to study the roof stability of large-section open-off cut in lower slice of slicing mining, the 14 boreholes in the top coal of the 203 open-off cut in the lower slice of 1−2 coal seam in Huojitu Mine of Daliuta Mine is taken as the research background. The influence of the upper slice mining and the lower slice open-off cut driving on the plastic zone of the top coal of the open-off cut is analyzed by theoretical analysis, numerical simulation and field borehole peep technology. And the stability of the roof structure is evaluated by the rock mass integrity index. From the perspective of the top coal structure form, the top coal of the open-off cut is partially over-excavated or under-excavated due to the upper slicing mining. The maximum over-excavation of the open-off cut is 1.2 m, the maximum under-excavation is 0.8 m, and top-coal uneven rate is 27.7%. The result of theoretical analysis show that due to the influence of upper slice mining of the top coal of the open-off cut, the depth of plastic zone in the floor is 2.02 m. Due to the disturbance of the lower slice mining of the open-off cut, the depth of the plastic zone in the top coal is 1.50 m. Borehole peep results show that the plastic zone of the open-off cut top coal is divided into the theoretical plastic zone and the measured plastic zone according to the theoretical calculation and borehole peep respectively. Due to the influence of upper slice mining, the depth of the measured plastic zone in the floor is 1.06-2.04 m. Due to the disturbance of the lower slice mining of the open-off cut, the depth of the measured plastic zone in the top coal is 0.34-1.50 m. The measured plastic zone caused by the influence of upper slice mining on floor is 17.63% smaller than the theoretical plastic zone. The measured plastic zone of the top coal caused by the disturbance of lower slice mining of the open-off cut is 25.82% smaller than the theoretical plastic zone. The result of numerical simulation analysis shows that due to the influence of upper slice mining, the depth of plastic zone in the floor is 1-2 m. Due to the disturbance of the lower slice mining of the open-off cut, the depth of plastic zone in the top coal is 1 m. The results obtained by the above three methods are highly consistent. The stability evaluation results of the top coal in the open-off cut show that the top coal integrity index ranges from 42.9% to 87.9%. The top coal thickness is positively correlated with the integrity index and negatively correlated with the fracture development. The proportion of top coal integrity evaluation as good or above is more than 1/2, indicating that the overall structure of top coal is basically complete. The research results can provide reference for the design of top coal thickness retention standard and support scheme of large section open-off cut in lower slice of slicing mining under similar mining conditions

Research on the application of fiber bragg grating monitoring for deformation of coal pillar in sections

When the coal mine passes through the overlying coal pillars in close proximity to the coal seam, the superposition of dynamic and static loads induces strong mining pressure, leading to deformation and instability of the coal pillars in the section, resulting in casualties and equipment damage. In order to explore the real-time monitoring of deformation and development characteristics of coal pillars in sections based on fiber Bragg grating, and analyze the mechanism of rock pressure manifestation in the stage of entering and exiting residual coal pillars, the optical measurement methods of FBG and grating stress meters are combined with on-site measurement to study the spatial distribution law of coal pillar strain and the time-domain response characteristics of internal strain of coal pillars in front of the working face during the mining process, Feasibility study on verifying the optical measurement method for observing the strain level of coal bodies. The results indicate that during the process of mining the overlying coal pillars, the roof of the section coal pillars is affected by concentrated stress, and the upper rock block is broken and rotated, resulting in an increase in the load on the coal pillars. As the working face advances, the overlying rock fracture further propagates upwards, and the key layer fracture recurs, causing pressure on the working face. The overlying rock rotates downward, ultimately leading to deformation and instability of the section coal pillars. Based on the amplitude of on-site grating strain increment, the severity of local deformation inside the coal pillar is determined. Under the influence of concentrated stress, the maximum strength that occurs during the deformation of the section coal pillar is 650 με on the left and right sides, the concentrated stress in the overlying strata causes the peak horizontal strain of the coal pillar to be located at the 11.5 m position of the coal pillar width. The strain along the width direction of the coal pillar shows a trend of first increasing, then decreasing, and then stabilizing. The internal strain field has an impact range of about 5 m during the mining process. A comprehensive study is conducted on the characteristics and laws of deformation and instability of coal pillars in the section caused by strain when the mining face passes through the overlying coal pillars. Combined with changes in strain level and physical and mechanical properties of the coal pillars, the precursor characteristics of coal pillar failure are obtained. Before reaching the peak deformation under external force, safety measures are taken to relieve pressure and protect the coal pillars before lifting them

Reproductive concerns and associated factors among female chronic kidney diseases patients: a Multi‐Center Cross‐Sectional Study

AimThe study aimed to investigate the current status of reproductive concerns and explore the associated factors among young female chronic kidney disease (CKD) patients.DesignA multi‐center cross‐sectional study was designed.MethodsThe study was conducted in six representative tertiary hospitals across southwest China. A total of 295 female Chronic kidney disease patients between 18–45 years of age completed a 20 min, web‐based survey, which included demographics and disease‐related information questionnaire, Reproductive Concerns Scale, Generalized Anxiety Disorder 7 (GAD‐7) instrument and Patient Health Questionnaire 9 (PHQ‐9) instrument.ResultThe survey total collected 270 valid questionnaires. The mean reproductive concern score was 54.39 ± 10.90 (out of a maximum of 90), with the mean scores for sub‐scales ranging from 7.80 ± 1.69 to 10.44 ± 1.85. Multiple regression analysis showed that those with higher reproductive concerns were more likely to have pregnancy intentions, to be in Chronic kidney disease stages 1–3, and to have a higher GAD‐7 score. This study offered further evidence of the need for improved education and emotional support surrounding reproductive concerns among young Chinese women with Chronic kidney disease.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/169312/1/nop2850.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/169312/2/nop2850_am.pd

Status and factors related to post‐traumatic growth in continuous ambulatory peritoneal dialysis: A multi‐centre study

AimTo investigate the extent of post‐traumatic growth, and the correlation between post‐traumatic growth and self‐perceived stress, post‐traumatic growth and self‐perceived burden among CAPD patients.DesignA cross‐sectional study.MethodsThis was a multi‐centre study including 752 patients from 44 hospitals. Self‐perceived stress, self‐perceived burden and post‐traumatic growth were measured using the post‐traumatic growth inventory (PTGI), the Chinese version of the perceived stress questionnaire (CPSQ) and the self‐perceived burden scale (SPBS). A multiple stepwise regression analysis was fit with the total PTGI score as the outcome of interest.ResultsPatients concurrently experienced post‐traumatic growth and stress following peritoneal dialysis. The initiation of patients’ education level, employment status and self‐perceived stress were all found to relate to growth among Chinese CAPD patients. There was not sufficient evidence to suggest that self‐perceived burden was related to experiencing growth.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/171193/1/nop21096.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/171193/2/nop21096_am.pd