Install Water Control Devices 2.3. Standpipe Installation and Testing Stand pipes are used for high pressure water cover drilling. The stand pipes are used for the same purpose as mechanical packers, to control water. However having a water control device already installed prior to drilling allows faster reaction times, if high pressure water is intersected whilst drilling. The drill string can immediately be retrieved from the hole and the ball valve shut off. Stand pipes are a steel pipe varying in length generally from 2m to 4m, sometimes longer (depending on the application) and may vary in diameter typically from 60mm to 100mm. The pipes may come with a breast plate attached or collar a short distance from one end, to push the breast plate against. The breast plates are then anchored to the face by resin anchored rock bolts. The pipe is fitted with an appropriate sized ball valve after it is secured in the hole and before drilling through the stand pipe commences. There are two methods for installing standpipes at EHM; these are grouted standpipes and chemical resin anchored stand pipes. The chemical resin anchored standpipes are predominately used on site. 2.3.1. Face Preparation and Standpipe Hole Preparation It is extremely important to scale the face prior to installing standpipes, to remove as much broken ground as possible and ensure the integrity of the face for a secure standpipe installation. The following steps must be adhered to before standpipe hole drilling can commence: ▪ Scale the face with the Jumbo removing all loose rock. De-rig Jumbo and pull it out so that a face prep can occur, following the Face Preparation Procedure, to remove any further loose rock and inspect for and mark up any misfires and butts. If a misfire is found contact your supervisor and barricade the area. ▪ Mark up intended collaring positions for water cover holes following the issued plan obtained from the shift supervisor. ▪ Set up jumbo back in job and proceed to bore pilot holes using a 45mm bit and 3.7m drill steel. Follow the issued plan for the required angles for each hole and bore pilot holes to 3m. Ensure all holes are collared slowly and drilled straight and true. ▪ Once pilot holes are completed, ream out with new 102mm pilot reamer ensuring full 3m depth is achieved. Ream holes from top of face to bottom and blow/wash out to remove fines from holes. ▪ If required, the collar of the hole can be reamed to 152mm for no more than 300mm, to allow for easier installation of the stand pipe. 2.3.2. Grouted Standpipe Installation The process of installing grouted standpipes is as follows: 1. Install the stand pipe by hand into the hole. Insert a 12mm X 600mm poly breather tube at the top of the hole and pack the collar of the hole with cotton wadding, rags or used wet cement bags. The breast plated pipe is then bolted into place by means of resin anchored bolts through the breastplate (see diagram below). 2. The pipe is then grouted in place by pumping grout through a packer installed in the pipe. A grout of W/C 0.7 (see Grout Pumping and Injection Training Package) or less is pumped in down the pipe and returns around the annulus of the pipe until it flows from the breather hose. The breather hose is closed and low pressure (5 bar or less) placed on the grout to ensure it has fully encapsulated the pipe and any open cracks around the pipe. Stem off any grout leaks until a good seal is obtained.
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