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Building construction impacting on existing underground structure

Updated: Apr 30

Underground structure

During the construction of a new residential building, SAALG Geomechanics was commissioned to analyze the impact on two tunnels located below the works, within the framework of the monitoring of the building construction works.

For that purpose, a numerical simulation was carried out by using a three-dimensional finite element model. A three-dimensional model was chosen due to the variable geometry of the tunnels with respect to the tunnel’s lobby slab and the variation of the acting loads, thus it was possible to represent the whole geometry. This three-dimensional model considered both the behavior of the ground and the behavior of the structures and their interaction with the ground itself.

Prior to the construction phase of the new residential building, the construction phases of the excavation of the tunnels and the construction of the lobby were simulated. This succession of predicted calculations allowed to find a tensional state of the ground and the structure representative of the current state.

The covered slab (foundation of the new building) rested on a perimeter system of diaphragm walls and two alignments of central piles. The central piles were based on micro-piles caps that were composed of a non-adherent section and an adherent section in the subjacent ground. In addition, a lobby slab was built over the tunnel (6.9 m above sea level).

Regarding the monitoring data, three control sections were defined in the tunnels in which prisms were installed to control the convergence of the tunnels. In addition, the settlement was controlled by measuring leveling points on the pillars between the lobby and the building structure.

Afterwards, as more monitoring data were obtained over the construction progress and they were hence uploaded to DAARWIN, the results of the model (also introduced into DAARWIN) were validated by comparing them with the values from the instrumentation, during the construction of the residential building. This comparison allowed the client to control the work in real time and to validate the design hypotheses.

In summary, being able to compare a predictive numerical model - that reproduces the stress-strain state of the ground – with the real observations (monitoring) allowed a better risk management to safeguard the assets underground. geotechnical, software engineer, geotechnical engineering software, construction AI, civil engineering software

civil engineering, geotechnical, software engineer, geotechnical engineering, borehole

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