The Roof-Fall Mechanism and Support-While-Drilling Technology of the Rectangular Roadway with Layered Roofs and Weak Interlayers

Studies have confirmed the poor stability of layered roofs with weak interlayers, and it is necessary to study the roof-caving mechanism of such roadways. A model of a weak interlayer was established to study the influence of the layer position and horizontal stress of layered roofs with weak interlayers on the stability of roadway roofs. FLAC(3D) numerical simulation software was used to study the damage characteristics of weak interlayers and different horizontal stresses on roadway roofs. Based on Proctor's theory, a maximum caving arch model was proposed to obtain the maximum caving arch height and span range. The pressure measurement coefficient and the vertical displacement change of the roof strata conformed to corresponding linear functions by fitting the pressure measurement coefficient and the maximum vertical displacement. A bolt-while-drilling support method (BWD) was proposed based on team measurement-while-drilling (MWD) to accurately determine the location of weak rock layers and the development range of plastic zones. A maximum caving arch model was proposed to obtain the range of influence of the maximum caving arch and the range of the maximum slope collapse angle. Furthermore, a method of anchor rod support-while-drilling was proposed and tested on-site in Jingu Coal Industry, Guxian County, Shanxi Province, China. According to the site conditions, short anchor cables were used to pass through the weak interlayer of roofs, with a good support effect. The results provide a new method for layered roof support containing weak interlayers.