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Cross Mine(M1977-410) Technical Revision No.5 <br /> The "Split Set" friction rock stabilizer consists of a hollow tube which has a slot along its entire <br /> length. One end is tapered to allow insertion into a drill hole which is drilled slightly smaller in <br /> diameter than the tube. When the tube is forced into the hole,the slot is squeezed closed and <br /> exerts an outward force against the rock. Friction between the steel tube and the walls of the <br /> borehole helps stabilize the rock mass. <br /> • Grouted rockbolts <br /> Grouted rockbolts refer to the use of reinforcement bars (rebar) or threadbars in combination with a <br /> grouting agent for creating a bond with the rock along the rebar's entire length or a selected length. Grout <br /> commonly consists of plain cement or a set of resins;fast acting at the toe,and slow acting along the bar. <br /> The required length of the grout bond is easily determined from strength factors of the bolt and diameter <br /> of the bolt. <br /> o Resin grouted rebar <br /> Resin grouted rebar is the most commonly used grouted support. When installed appropriately <br /> its full-length bond allows for efficient long-term support in static loading conditions. <br /> Furthermore, the resin used allows for corrosion protection as only the tip of the rockbolt is <br /> exposed. The manufactured resins come in various set times,from 15 seconds to 7 minutes,at a <br /> specified temperature. In order to create a quick bond at the end of the rockbolt a combination <br /> of fast set and the appropriate spin rate is used. <br /> o Hollow Bar Anchor <br /> Some types of groutable bolts are manufactured with a hole through the center for the entire <br /> long axis of the bolt. This hole allows for cement grout or resin to be pumped through the bolt <br /> and subsequently fill the annulus. The system has historically been known as a "self-drilling <br /> anchoring" because the hollow fully-threaded bar serves as both the drill string and the grouted <br /> anchor,thus installation is performed in a single operation and can be used in virtually any type <br /> of soil or decomposed rock. <br /> The sacrificial drill bit is screwed onto the end of the thread bar and left in place following drilling. <br /> The drilling fluid (air,water,or grout) is introduced through the hollow bar and allows the spoils <br /> to flush from the borehole. This type of system is particularly suitable for ground that does not <br /> allow for open-hole drilling. In such cases,drilling with a grout fluid serves the purpose of flushing <br /> spoils from the borehole and prevents looser, surrounding material from collapsing due to the <br /> higher relative density of the grout. <br /> 6.2. Collapse Repair <br /> The loss of material from the roof of the tunnel during the portal collapse created a remnant void which <br /> now exists above the tunnel opening. Figures 4 and 5 present longitudinal and transverse cross-sections <br /> through the maximum portion of the collapse void,respectively. The remaining void created by the portal <br /> collapse will be backfilled with pervious cellular concrete to provide permanent ground support that will <br /> stabilize the slope and allow drainage. It is estimated that the void will require approximately 65 cubic <br /> yards to fill. The backfill mix design includes the use of Aerix Industies AquaerixTM foaming agent to create <br /> a lightweight pervious flowable mixture(Attachment 2). <br /> a <br /> 13 <br />