scholarly journals Analysis and Application on Inverted Arch Support of Cross-cut Floor Heave

2021 ◽  
Vol 2002 (1) ◽  
pp. 012069
Author(s):  
Chao Wang ◽  
Yongping Wu ◽  
Shijiang Chen ◽  
Wenxiang Zheng ◽  
Xiaoyi Chen ◽  
...  
Keyword(s):  
Floor Heave ◽  
Arch Support

scholarly journals Stress and deformation analysis of gob-side pre-backfill driving procedure of longwall mining: a case study

2021 ◽  
Author(s):  
Rui Wu ◽  
Penghui Zhang ◽  
Pinnaduwa H. S. W. Kulatilake ◽  
Hao Luo ◽  
Qingyuan He
Keyword(s):  
Rock Mass ◽  
Stress Distribution ◽  
Coal Seam ◽  
Abutment Pressure ◽  
Longwall Mining ◽  
Vertical Stress ◽  
Floor Level ◽  
Working Face ◽  
Floor Heave ◽  
Stress And Deformation

AbstractAt present, non-pillar entry protection in longwall mining is mainly achieved through either the gob-side entry retaining (GER) procedure or the gob-side entry driving (GED) procedure. The GER procedure leads to difficulties in maintaining the roadway in mining both the previous and current panels. A narrow coal pillar about 5–7 m must be left in the GED procedure; therefore, it causes permanent loss of some coal. The gob-side pre-backfill driving (GPD) procedure effectively removes the wasting of coal resources that exists in the GED procedure and finds an alternative way to handle the roadway maintenance problem that exists in the GER procedure. The FLAC3D software was used to numerically investigate the stress and deformation distributions and failure of the rock mass surrounding the previous and current panel roadways during each stage of the GPD procedure which requires "twice excavation and mining". The results show that the stress distribution is slightly asymmetric around the previous panel roadway after the “primary excavation”. The stronger and stiffer backfill compared to the coal turned out to be the main bearing body of the previous panel roadway during the "primary mining". The highest vertical stresses of 32.6 and 23.1 MPa, compared to the in-situ stress of 10.5 MPa, appeared in the backfill wall and coal seam, respectively. After the "primary mining", the peak vertical stress under the coal seam at the floor level was slightly higher (18.1 MPa) than that under the backfill (17.8 MPa). After the "secondary excavation", the peak vertical stress under the coal seam at the floor level was slightly lower (18.7 MPa) than that under the backfill (19.8 MPa); the maximum floor heave and maximum roof sag of the current panel roadway were 252.9 and 322.1 mm, respectively. During the "secondary mining", the stress distribution in the rock mass surrounding the current panel roadway was mainly affected by the superposition of the front abutment pressure from the current panel and the side abutment pressure from the previous panel. The floor heave of the current panel roadway reached a maximum of 321.8 mm at 5 m ahead of the working face; the roof sag increased to 828.4 mm at the working face. The peak abutment pressure appeared alternately in the backfill and the coal seam during the whole procedure of "twice excavation and mining" of the GPD procedure. The backfill provided strong bearing capacity during all stages of the GPD procedure and exhibited reliable support for the roadway. The results provide scientific insight for engineering practice of the GPD procedure.

scholarly journals Floor Heave Mechanism and Anti-Slide Piles Control Technology in Deep and Large-Span Chamber

2021 ◽  
Vol 11 (10) ◽  
pp. 4576
Author(s):  
Jian Shi ◽  
Desen Kong
Keyword(s):  
Model Test ◽  
Shear Failure ◽  
Deformation Mode ◽  
Control Technology ◽  
Plastic Limit ◽  
Large Span ◽  
Similarity Model ◽  
Floor Heave ◽  
Plastic Limit Analysis ◽  
Local Shear

Based on plastic limit analysis, the deformation and fracture mechanism of the floor in the large-span chambers of deep mines are discussed and a similarity model test is carried out to verify the reliability of the theoretical analysis. The results show that the local shear failure first appears below the loading area and develops to the middle part of the test model with the increase in load; when the local shear failure develops to form a continuous sliding surface, continuous plastic flow deformation occurs; the distribution of the plastic zone and the deformation mode obtained from the similarity model test are basically consistent with the Hill-like deformation mode derived from plastic limit analysis. A control technology with anti-slide piles is proposed in order to deal with floor heave in large-span chambers on the basis of previous work. An approach for determining the supporting parameters of anti-slide piles is deduced. To deal with the floor heave in the −1100 level gangue winch room of the Huafeng Coal Mine, a comprehensive reinforcement scheme with anti-slide piles composed of discarded rails and anti-floating anchors is introduced for the floor heave control of the chambers. Site monitoring results show that the scheme not only effectively restrains the development of floor heave, but also ensures the long-term stability of the chamber floor.

scholarly journals A Three-Dimensional Printed Foot Orthosis for Flexible Flatfoot: An Exploratory Biomechanical Study on Arch Support Reinforcement and Undercut

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5297
Author(s):  
Ka-Wing Cheng ◽  
Yinghu Peng ◽  
Tony Lin-Wei Chen ◽  
Guoxin Zhang ◽  
James Chung-Wai Cheung ◽  
...  
Keyword(s):  
Peak Pressure ◽  
Reaction Force ◽  
Three Dimensional ◽  
Biomechanical Study ◽  
Rank Test ◽  
Arch Height ◽  
Vertical Ground Reaction Force ◽  
Flexible Flatfoot ◽  
Arch Support ◽  
Foot Orthosis

The advancement of 3D printing and scanning technology enables the digitalization and customization of foot orthosis with better accuracy. However, customized insoles require rectification to direct control and/or correct foot deformity, particularly flatfoot. In this exploratory study, we aimed at two design rectification features (arch stiffness and arch height) using three sets of customized 3D-printed arch support insoles (R+U+, R+U−, and R−U+). The arch support stiffness could be with or without reinforcement (R+/−) and the arch height may or may not have an additional elevation, undercutting (U+/−), which were compared to the control (no insole). Ten collegiate participants (four males and six females) with flexible flatfoot were recruited for gait analysis on foot kinematics, vertical ground reaction force, and plantar pressure parameters. A randomized crossover trial was conducted on the four conditions and analyzed using the Friedman test with pairwise Wilcoxon signed-rank test. Compared to the control, there were significant increases in peak ankle dorsiflexion and peak pressure at the medial midfoot region, accompanied by a significant reduction in peak pressure at the hindfoot region for the insole conditions. In addition, the insoles tended to control hindfoot eversion and forefoot abduction though the effects were not significant. An insole with stronger support features (R+U+) did not necessarily produce more favorable outcomes, probably due to over-cutting or impingement. The outcome of this study provides additional data to assist the design rectification process. Future studies should consider a larger sample size with stratified flatfoot features and covariating ankle flexibility while incorporating more design features, particularly medial insole postings.

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