| The New Austrian Tunnelling Method (NATM) was used in the construction of a short segment of tunnels in the underground section of the Tren Urbano, at Río Piedras. The section consists of four tunnels that crossed under two historic buildings. The tunnels were constructed through sandy clays, silty clays and sands. A geotechnical monitoring program was implemented in order to monitor the surface and subsurface ground movements. Compensation grouting was used between the tunnels and the overlying structures to reduce settlements and distortions.; The data of the instruments was analyzed and related to the construction process. Some cross-sections were made to illustrate the geometry of the system, the tunnels location, the geology of the area and the maximum settlement profile. The soil movements experienced during the construction were compared with the settlement predictions.; The predicted settlements were higher than the actual, especially for the historic buildings. The movements were higher in the entrance of the tunnels, an area that was outside the grouting zone. The NATM proved to be successful in the preservation of the buildings, and this could not be achieved without the grouting injection plan. |
