Grout Pumping and Injection Operations TR 003 Typical Ground Conditions ▪ If the grouting pressure is not building to >70 bar after the injection of 2000 – 3000 litres of grout, then change the grout mix to a W/B ratio of 1.5. ▪ The stop injection criteria for the hole will be when a maximum pressure of 90 bar is achieved and the flow rate is down to 1-2 litre/min. ▪ If the stop criterion is not achieved after 5000 litres of grout, reduce the W/B ratio to a “blocker” mix, i.e. next lowest W/B ratio of 1.5 or 1.2 or 1.0. Open Structured Ground ▪ If the grouting pressure is not building to >70 bar after the injection of 5,000 litres of grout, then change the grout mix to a W/B ratio of 1.5. ▪ The stop injection criteria for the hole will be when a maximum pressure of 90 bar is achieved and the flow rate is down to 1-2 litre/min. ▪ If the stop criterion is not achieved after 10,000 litres of grout, reduce the W/B ratio to the next lowest W/B ratio of 1.5 or 1.2 or 1.0. 4. RESPONDING TO PROBLEMS 4.1. Whilst Injecting the Grout ▪ As mentioned earlier you should be continuously monitoring the face conditions and the surrounding area for any grouting related disturbance or leakage, remembering if this happens to firstly slow down the pump or adjust the batches to a lower water binder ratio. ▪ Remember if you need to stop and use materials like timber wedges, rags, discarded cement bags etc to stem the grout leaks. ▪ Continually monitor face conditions and the surrounding area for any grouting related disturbance or leakage. If grout leakage occurs from the rock, slow down pump or adjust batches to a lower water binder ratio. Stop if necessary and use timber wedges, rags, discarded cement bags etc to stem the grout leaks and ensure grouting pressure is maintained. The method deemed to be most successful will depend on ground conditions. ▪ If grout flows from an adjacent hole that has not been grouted it must be monitored. Once pure grout flows, the packer valve on the leaking hole must be closed and all connected holes shall be grouted on rotation until each hole achieves stop pressure. ▪ If grout is continually leaking from faults and fractures in the face, the leaks need to be monitored and if able to do so, measure the amount of grout from the leak (e.g. use a bucket or suitable container to capture litres of spillage). If the volume of grout being delivered is exceeding the amount of leaked grout, pumping may continue, closely monitor When necessary to use “Blocker” grout, the grout plant and hoses MUST be washed thoroughly with water PRIOR to mixing Blocker and immediately after mixing. If new cracks begin to open up in the fibrecrete or rock mass, especially behind the injection area, immediately stop operations, barricade the area and notify your supervisor. Opening up of cracks may indicate imminent ground failure.
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