Consolidation of resins or expansive concretes
The movement of the terrain may be of different types: immediate or long term, differentiated or rigid rotation-translation of the construction. In all cases we can intervene to strengthen the foundations acting directly or indirectly.
Minipalo GEOSYSTEM®: Use for seismic retrofit of buildings
The damage and fissures of the buildings and the structures in general, is usually due to the movement of the terrain even to the complexity of the terrain/construction system and the difficulty of doing researches of the condition of the existing foundations and it is not always possible to determine the cause.
The movement of the terrain may be of different types: immediate or long term, differentiated or rigid rotation-translation of the construction.
These differences can be due to the excessive charge on the structure (permanent or accidental), phenomena of subsidiarity, changes on the skirt, increased charges, vibrations or for seismic events.
In all cases we can intervene to strengthen the foundations acting directly or indirectly.
are the ones that are made directly in the foundation structure and involve strengthening and increased stiffness.
These are, for example, work under construction, extension of the base, the deep lowfoundations with drill poles of large diameter or with drilled minipoles or short diameter, etc.
These are the ones that don’t work directly in the foundation structures. They are used to reduce the differential landslides, working around the foundation. For example, the injection of cement mixtures or injections of expansion resins. To improve the stability of the terrain around the foundations, we can use a mixture of cement and water low depth or consolidate the terrain with vertical drainage.
The advantages of Minipalo GEOSYSTEM® technology
EDILSYSTEM srl, the last few years, have found and test an innovative and revolutionary solution with the patented new system “minipalo GEO-SYSTEM®”, that combine the consolidation systems of direct and indirect foundations, taking advantage of both technologies, with an intervention that combine the use of a mixture of expansive injections, minipoles with a smaller diameter, reaching the deeper soil layers.
The use of “minipalo GEO-SYSTEM®” is perfect for the consolidation of the foundations when we are talking about seismic adequacy thanks to the easy donning by using reduced-size machinery, that can be use inside of buildings and very small areas. The results reached with this method is almost impossible with others.
“Minipali GEO-SYSTEM®” are reinforced poles with small diameter, placed by direct drilling, using as drill guide hollow bars bonded together with sleeves with non-return valves, that stay in the construction site as armor and with perforating pile which is chosen depending on the type of terrain.
The injection is made with polyurethane resins of expansion and high resistance or with a mixture of expansion cements studied for it. (“Geo_Xp”).
With this system, we can take advantage of every technique using and intervention that combine polyurethane resins or expansion concrete with steel poles with reduce diameter, that allows to transfer the superficial charges to deeper soil layers and consolidate the ground under the existing foundations.
The injection with polyurethane resins can be replaced by injection of water/ expansion concrete “Geo-Xp” through the hollow bars and the holes of the piercing tip; or using a mixture of aggregative of double compound, without concrete, with inorganic mineral compound, specific for the consolidation of terrains with low permeability.
The product to inject varies depending on the type of terrain and the resistance that we want to reach.
Fixing bars, with different diameters (32/38/55 mm), can be of different length according to the necessity and it is jointed with sleeves with non-return valves studied for it.
The lateral adhesion values between the body of injection and the ground, with “minipali GEO-SYSTEM®”, thanks to its manufacture which is made in just one phase, are greater to the minipoles and poles that are not injected.
The assembly technique allows to:
– Improve the mechanical properties of the ground with the interface of minipole-terrain;
– Get higher resistance in the cutting of the injection body with the terrain;
Reduce the displacements around the minipole head and get an increased rigidity of the base structure;
– Increase execution speed;
– Avoid using coated tubes in case of drilling unstable grounds.
We can see in the picture the “minipalo GEO-SYSTEM®” injected with polyurethane foam, with drilling tip, centering device and sleeve joint. The use of the minipole head to the penetration of the foundations is reached with jet reoplastic microcement of accelerated hardening: MICROGROUND INJECTION ANCHOR, specific for the manufacture of minipoles.
“Minipalo GEO-SYSTEM®” has been tested with real load tests of the University of the studies of Water, Department of Civil Engineering. The tests carried out, of axial type, are performed to define curves of load/assignment on the minipole head and determined the higher load of the set pole-terrain.
1. Minipole axis
2. Field/ Sidewalk plane
4. Rotary percussive drilling with specific machinery.
5. Injection with expansion concrete and polyurethane resins.
The compaction of the foundations combining the steel drilling minipoles of reduced diametre with injections of polyurethane resins or expansive concrete of the surrounding terrain, reduces the causes of displacement and the deterioration of the buildings and the built structures.
Reducing the deficits of continuity/ joint of the existing foundations will improve the response to the seismic problems of the buildings.
The technology “minipole GEO-SYSTEM®” together with the horizontal structural elements (as steel profiles anchor to the walls and beams structurally joined with wall panels), allow to increase the foundation structure rigidity making it ideal to withstand tractions.
This technology, as we can see in the tests carried out, can be used both for consolidate foundations and under foundations and for making structure anchors for foundation supporting sloping, to ensure the terrain for the construction and replacement of galleries to make braces (passives instead of actives), in addition to use it combined with sismic insulation and sinks.
Important seismic adjustments have been done all over the national territory in buildings of different dimensions and with different structural characteristics.
The minipole-ground-structure interaction is a very important thing to take into account while doing the project, especially when there are seismic commitments; in fact, the acceleration transmitted to the structure, may induce inertial forces that can damage the minipole head.
Thanks to the manufacture technique, with “minipole GEO-SYSTEM®” important values of lateral adhesion are reached and, because of the completely filled of the perforated volume, we have an excellent connection minipole-terrain. This confers a high capacity of shock absorption to the minipole. It also contains fluctuation and deflection commitments with the anchor heads which tend to widen the gap between the body and the surrounding soil injection.
The head of the minipole is a critical zone that has to be evaluated carefully, depending on the upper loads and the foundation types.
Use of Minipalo GEOSYSTEM® over terrains subject to liquefaction
“Minipali GEO-SYSTEM®” can be also used for the seismic adjustments of buildings over terrains subject to liquefaction (as in the region of Emilia in an earthquake in 2012).
Over these type of terrains, “Minipali GEO-SYSTEM®” are a valuable fixing because they can improve the mechanical qualities so that the risk of liquefaction is reduced.
In fact, “Minipali GEO-SYSTEM®” technology, allows to consolidate that kind of terrain, increasing the cohesion and transferring loads to strata that are not susceptible to liquefaction, reducing the risk as advised in the normative NTC-2008.
In conclusion, we can assure that “Minipali GEO-SYSTEM®” are the best solution to seismic adjustments and to build new foundations.