The micropiles

are structural elements

, as the piles, which are able to transmit to the subsoil the forces and loads applied to the above structures. Thanks to the reduced dimensions of their diameters, and especially of the equipment which is necessary to their realization, they cover a wide range of applications.

The micropiles allow the under foundations of existing works, by making use of the possibility to carry out inclined drilling from the vertical plane.

It is basically about making a hole in the ground by means of a rotary drilling or a rotary percussion drilling, successively inserting tubular or profiled reinforcements within them and then filling the hole with cement mixture. This last penetrates in the surrounding strata creating sbulbatures which increase the cohesion of the ground and allow a considerable increase of the lateral friction.

The bored piles

result from

the prior removal of the soil and the subsequent casting of a cement conglomerate usually reinforced.
The excavation takes place through drilling, by using rotating equipment (bucket, propeller, etc.), or by excavation, using equipment provided with a clamshell bucket with circular section.

During the excavation the stability of the walls can be obtained, where necessary, by using a stabilizing fluid or by installing a temporary metal coating. Once the drilling is complete, the reinforcement cage will be installed, then the concrete will be poured with the "contractor" system and, upon completion of this, any temporary coating will be extracted.

In their general sense they can be considered among the most versatile and used works in the field of deep foundations also for the affordability of their realization.

Our company is able to perform bored piles with a diameter of 400 mm to a diameter of 2,000 mm and up to a depth of 50 m.

The use of

cfa piles

becomes more and more frequent having regard to the real benefits of their application.
This type of pole can be employed in almost all types of grounds, but it is especially useful in the urban areas, thanks to its low-noise and low level of vibrations.

The excavation is done by means of a continuous flight auger equipped with a closed hollow rod in the middle, which prevent soil and water from entering during the excavation. The rotation is continuous thanks to a specific rotary machine.

Once the excavation has been done, the concrete is pumped through the hollow rod of the auger, therefore the central pole is realized by the gradually extraction of the auger from the excavation.

Once the concrete has been pumped, the metal frame is placed, which can vary from 9 to 12 and consists of steel bars bigger than 20mm. If necessary, hard-wearing steel tubes can also be used.

The

anchor rods

are structural elements able to transmit a tensile force to the load bearing layers of soil or rock in depth.

The technique of anchoring by means of strands and steel bars in the field of foundation works has developed in parallel with that of reinforced concrete and prestress. It was applied for the first time to the great dam of Cheurfas in Algeria in 1935. Since that first application this technique has been ceaselessly improving along with the technological evolution of the structures and of the geotechnical engineering.

Some of the main functions of the tie rods are the following:

To anchor the containing structures as retaining walls, diaphragms, berliners deep to the soil; To transfer in depth the pulling forces acting on the foundation; To withstand the uplift hydraulic force which acts below structures that are realized under an aquifer; To ensure the stability of works on unstable slopes; To improve the stability of slopes and escarpments; To prestress rock masses or massive concrete structures.

The tie rods can be classified according to several criteria, which are:
Intended use: permanent tie rods, temporary tie rods (fixed or removable), preliminary sample tie rods;
Load application: passive or active tie rods;
Nature of the material in which the tie rod is anchored: in the soil or in the rock;
Filling executing way: by gravity, low-pressure injection in a single-stage procedure, repeated and selective injection;
Reinforcement type: bars, strands, profiled (micropiles).

The functional parts of a tie bar are:
The anchoring head, which consist of the anchor plate and of the locking device, the free, intermediate section, composed of the reinforcement elements which transmit the tensile force between the head and the active section, anchoring (or foundation), consisting of the reinforcement cemented to the ground or to the surrounding rock, to which it transmit the acting tensile force.
Among the several types of existing tie rods the type IRP or IRS is of particular interest, because of the possibility to perform a repeated and selective injections under pressure by means of specific check valves installed on an injection pipe along the whole length of the anchor rod. This particular performing technique uses the experience gained in the field of cement injections and allows these tie rods to reach a high load bearing capacity even in grounds with poor mechanical properties.


The main execution phases in the realization of an IRS anchoring tie bar are the following:
Drilling up to the project depth by means of the most suitable system and equipment for the ground to be crossed. Formation of the duct, consisting in the filling of the hole with cement mixture, by letting it flowing back starting from the bottom of the hole. Installation of the tie rod in the hole. The anchor rod is equipped on the underside with specific check valves, called “à machettes” valves. This stage could precede the formation of the duct; in this case the filling is carried out through the deepest valve of the injection pipe. Once the duct mixture has been completed, the injection under pressure can be performed by using all the available valves in sequence from the deepest one. The injection under pressure can be carried out into different and subsequent phases.

All tie rods are now subject to extremely strict regulations, in particular the definitive type of tie rods. These regulations, among other things, prescribe in detail the correct level of protection of the tie rods according to the project duration, specifying the number and types of anti-corrosive barriers to be provided, minimum characteristics of the materials to be used, control tests to be carried out, etc. .. to reach very high levels of bearing capacity in terms of durability, speed of execution and quality of the final product.

A

diaphragm

is a temporary or permanent cast in place structure which is used to support artificial excavations, preventing the soil inside the excavation from collapsing.

A diaphragm is realized by means of specific machines equipped with clamps or rectangular cutter, which are dug into the soil through curbs to excavate a vertical section: to prevent the material of the remaining wall from collapsing, where necessary, the excavation is realized by using bentonite slurry. Once the excavation has been completed a preassembled steel cage is placed and then the concrete is casted according to the “contractor” system.

The realization of the plastic diaphragms differs from the previous in that there is neither steel cage nor concrete to place, instead a specific mixture or other material, which limits or reduces the water flow.