Execution process

The implementation of the anchors can begin once the land of the excavation has been accurately staked out. The system used for this job is based on the type of terrain where the brace is to be implemented. Generally it is drilled by rotopercussion with the hammer at the base or head driving the rod, through which circulates the drilling fluid where necessary. This fluid cools the crown of the drill casing and the interior rod, dragging the detritus to the exterior. It can also be drilled with air.

This is followed by the placement of the reinforcement of the anchor (which could be rail or wire) made in the workshop with the guards and dividers necessary and duly approved. At this point we can proceed with the injection of the grout (at the dose specified in the plans) in one or various phases:

• In global single injection (IU anchors) the injection is realised in one phase, bottom up and at pressure.
• In repetitive injection (IR anchors) it’s completed in two phases via one way valves at medium pressure.
• In repetitive selective injection (IRS anchors) a larger number of re-injections are completed via hoses and at high pressure.
• After the required time has passed (normally 7 days without the use of accelerators) the load of tension is placed, following the positioning of the head of the anchor, made up of the plate and wedges. The stretch is performed with a single thread (cable to cable) or multi thread (pulling on all cables at once) this operation is carried out by qualified professionals, who whilst maintaining the tension by means of a jack, proceed to block it using wedges or special nuts. In case of rod anchors, the stretch is completed using a perforated piston jack.

The implementation of anchors requires rigorous control, carried out by CIMENTATEC from the receipt of the raw material for the anchors, through to the placement in the hole and ending with the stretching process. For which each anchor is accompanied by protocol containing the following information:

• Name and location of the works..
• Plan of work and numbering of anchors.
• Project characteristics of each one of the anchors: free length, length of bulb, incline, diameter of bulb and diameter of excavation.
• Characteristics of the anchor components: number of cables, diameter of rod, quality of steel and type of protection to be used.
• Drilling system.
• Theoretical details of the injection.
• Properties of the grout.
• Forecasting of tests that will be completed on the grout.

Once the anchors have been implemented, the project manager of CIMENTATEC completes and installation work which includes:

• Name and location of the works.
• Number of anchors referenced in the plans.
• Implementation date.
• Characteristics of implemented anchorage: free length, length of bulb, incline diameter of bulb and diameter of excavation.
• Incidents of any type that have occurred during the completion of the anchoring.
• Details of the grouting: type of concrete used, additives used, dosage of grout, dates of injections and re-injections, pressures of injection, quantities injected.
• Dates of tests completed on the grout (if that was the case).