Experimental study on the failure mechanism of layer‐crack structure

Abstract

Field investigations have proven that layer‐crack structures make an essential contribution to rock burst occurrence in brittle coal or rock mass. This paper first studies the mechanical behavior of layer‐crack red sandstone specimens with different geometric configurations of vertical fissures (ie, fissure width, fissure length, and fissure number) through uniaxial compression and Brazilian tests. Then, the digital speckle correlation method (DSCM) and acoustic emission (AE) technique are used to record the deformation and failure processes. Finally, the failure mechanisms of the layer‐crack structure are presented and discussed. Under compressive conditions, the failure process can be divided into compatible support, incompatible support, and postpeak unstable failure stages. An increase in fissure width, as well as fissure length or number, causes an increase in the inner damage accumulation and a decrease in the stiffness coefficient by decreasing the strain of the compatible support stage. Thus, the bearing capacity of the layer‐crack structure is weakened. Under tensile conditions, the tensile ability decreases linearly as the fissure length increases, but the vertical pressure acting on the fissure increases linearly as the fissure width increases. Thus, the tensile strength of the layer‐crack structure decreases as the fissure length (or width) increases.

Monitoring and correction of the stress in an anchor bolt based on Pulse Pre‐Pumped Brillouin Optical Time Domain Analysis

“…In particular, strain information along the rock bolts should be collected to reveal long‐term movements of the rock mass and to allow an operator to take necessary precautions . With the development of optical fiber technology and its use in sensing and measurement, this technology is increasingly used in monitoring stress, overburden deformation, temperature, humidity, and moisture . Lately, optical fibers have been used in monitoring the stress of bolts .…”

Field and simulation study of the rational coal pillar width in extra‐thick coal seams

“…The simulation and field measurement results for the roof subsidence at a monitoring point 6 m from the roof surface are 126 and 134 mm, respectively (Figure B). Because FLAC3D software takes rock masses as the continuum medium, in actually, the deformation of surrounding rock could produce fissures and separations, so the deformations of surrounding rock measured in field are larger than those of numerical simulation. However, the numerical results are very close to the field measurement results, and the error between numerical results and in situ measurements is less than 2%.…”

Deformation and failure laws of roadway surrounding rock and support optimization during shallow-buried multi-seam mining

“…When excavating the roadway in the lower coal seam, it is easy to cause problems such as fragile roof, large subsidence, and serious rib spalling, which makes it difficult to maintain the roadways (Zhang et al 2008;Yu et al 2016b). It is well known that the stability of roadways is very significant for the control of roadway surrounding rock and the safety production of coal mines (Liu et al 2018;Ning et al 2018;Guo et al 2019aGuo et al , 2019bWang J, et al, 2019). Therefore, it is essential to conduct the study on the deformation and failure laws of the surrounding rock of roadways and the support optimization in shallow-buried multi-seam mining.…”