Anchor rods

Anchor rods are structural elements capable of transmitting a tensile force to the soil or rock at depth through the installation, inside the drilled hole, of harmonic steel strands consisting of 7 diam. wires. 5mm or improved adhesion steel bars. The drilling method is the same as that of micropiles (see Micropiles item) except that the drilling diameter can be up to 200 mm. and the drilling is always done at a variable angle to the horizontal. Once the drilling has been carried out, the tie rod is inserted and the cement mixture is poured under pressure, through the special PVC tubes starting from the bottom upward, with possible use of fluidizing additives to improve the mechanical characteristics of the injection mixture. When the casting is cured, the tie rod is tested and stretched at the design load.

The tie-rod can be of the temporary type, when its use is planned for the temporary period of the construction of the work (e.g., support of a bulkhead for the construction of a basement) of the permanent type when its use must guarantee a duration equal to that of the work itself, and valved, with repeated injections of cement mixture under pressure and with the use of double plugs to be placed inside the tube, at each individual valve. With this methodology, high bearing capacities can be achieved even in soils with poor mechanical properties.

The functional parts of an anchor tie rod in place are:

• The tie rod armature subdivided in turn into anchor bulb fully saturated with cement mixture and free section, where the strands or bar protected by the cementitious mixture can slide freely without transmitting transverse tension to the surrounding soil.
• The anchor head, consisting of a clamping plate that anchored to the work to be supported using hydraulic jacks, transmits the tensile force.
• PVC injection nozzles for proper pressure casting of cement mixtures along the entire length of the hole. The tubes are fitted in some cases with valves for repeated injection.

Tie rods are used in conjunction with micropiles, CA. diaphragms, large-diameter piles to anchor retaining walls to the ground, to ensure the stability of works placed on unstable slopes, to consolidate tunnel vaults subjected to high hydrostatic pressure, to stabilize rock walls, slopes and embankments, and in all areas of engineering where the ground offers the possibility of absorbing the stresses involved, providing the constraints necessary for the statics of the work.