| This paper deals with the problems of the low bonding force between hardened resin and soft surrounding rock,and the rapid attenuation of anchoring forces when conventional anchoring methods are used for cable bolts.This paper takes the soft surrounding rock roadway of Mindong No.1 Mine as the engineering background,using comprehensive research methods such as theoretical analysis,numerical simulation,laboratory test,field test have obtained the zonal characteristics of the roof separation layer failure.Through the support adaptability analysis,it is concluded that the cable bolt cannot exert high-strength support force under ordinary anchoring conditions.The main goal of paper is to develop methods that will take full advantage of the potentially great supporting force that can be provided by high-strength cable bolts installed in soft rock.The anchoring mechanism of the cuneiform reaming anchoring of the cable bolt hole is discussed based on theoretical analysis,and it is proposed that increasing the number of cuneiform structures with reasonable geometric dimensions is an effective method to prevent the anchoring failure of the cable bolt.Furthermore,the anchoring mechanism of cuneiform reaming anchoring was studied through numerical simulation,and the reasonable reaming angle corresponding to different surrounding rock strengths was determined.The anchoring technology has been successfully applied to the field,which is helpful to give full play to the supporting performance of the cable bolt and minimize the attenuation of the supporting force of the cable bolt.The specific conclusions are as follows:(1)Taking the high-strength supporting force of the cable bolt as the entry point,the anchoring characteristics of the cuneiform reaming anchoring of the cable bolt hole are discussed based on theoretical analysis,and it is proposed that increasing the number of cuneiform cavities in the boreholes(with each cavity having appropriate geometric dimensions)is an effective way to prevent cable bolt anchorage failure.Furthermore,the results of a comparative analysis of single cuneiform reamed anchors and double cuneiform reamed anchors using numerical simulations are described.And the anchoring mechanism of the cuneiform reaming anchorage is revealed.Compared with the single cuneiform reamed anchors,the double cuneiform reamed anchors provides more stability and is an effective way to access the great supporting forces that a high-strength cable bolt is potentially capable of providing.(2)Analyzing resin displacement in double cuneiform anchors stressed under different conditions allowed the appropriate reaming angles for different rock strengths to be determined.The reaming angle for rock with a uniaxial compressive strength(UCS)of 6 MPa or less should be from 18°–20°.For rocks like this,lower reaming angles are too low to achieve the expected anchoring effect.When the UCS of the surrounding rock is 9 MPa or greater,the reaming angle should be reduced;appropriate reaming angles for these stronger rocks are 14°–16°.Restricted by the small diameter of cable bolt boreholes,the DCRT for cable bolt borehole reaming was designed and developed.The DCRT’s main components are a drill rod connector,high-strength reaming blades,a blade restricted slot,and a blade adjustment mechanism.(3)The supporting force of the ordinary cable bolt is extremely ineffective,and the cable bolt will even lose the supporting effect completely,which will bring serious hidden danger to the roof safety.Compared with the anchoring force of the cable bolt under the ordinary anchoring condition,the double cuneiform reaming anchoring method can increase the anchoring force by more than 30%,indicating that the double cuneiform anchoring system can give full play to the high-strength supporting force of the cable bolt in the soft surrounding rock and minimize the attenuation of the cable bolt supporting force. |
