Structural Monitoring of the Palacio de Tribunales de Justicia – Santiago Metro Line 3

Project objective

Within the framework of the construction of Line 3 of the Santiago Metro – Stage 1: Shafts and Tunnels, and in compliance with the requirements approved by the Consejo de Monumentos Nacionales de Chile, a structural monitoring system was implemented for heritage buildings located within the area of influence of the tunnel excavation works, from the construction phase through to the commencement of metro operations.
Among the buildings subject to monitoring was the Palacio de Tribunales de Justicia, located at 1140 Compañía Street, Santiago, Chile.
The Corporación Administrativa del Poder Judicial commissioned our company to perform independent third-party monitoring in order to verify and validate the periodic monitoring data provided by Metro de Santiago.

Monitoring System

The monitoring system consisted of:

• Automated Total Station
• Control (reference) prisms
• Monitoring (measurement) prisms

The Total Station was configured to automatically acquire data every two hours, recording the three-dimensional coordinates of:

• its own position
• the reference prisms
• the prisms installed on the monitored structure

The system enabled continuous tracking of the predicted deformations established during the design phase, both at structural level and at ground surface level.

Monitoring Objectives

The monitoring system fulfilled a dual purpose:

• Verification of predicted deformations, in accordance with the engineering design models.
• Early warning function, allowing timely intervention in the event that deformation trends exhibited abnormal convergent or divergent behavior relative to established design thresholds.

During the monitoring period, a seismic event of magnitude 8.4 (September 16, 2015) occurred. No permanent structural variations attributable to this event were detected by the monitoring system.

Results and Data Analysis

Analysis of the data obtained from the control prisms indicates that:

• The millimetric variations recorded between measurement cycles were primarily associated with environmental factors, including temperature fluctuations, atmospheric pressure changes, and cloud cover.
• The recorded oscillations exhibited a sinusoidal pattern around the reference baseline (zero line), with no progressive displacement trends.
• Minor horizontal displacements observed were consistent with thermal expansion effects inherent to structural materials.

Based on the comprehensive evaluation of the monitoring records over a two-year period, it can be concluded that the structure of the Palacio de Tribunales de Justicia remained stable and was not adversely affected by the construction activities associated with Santiago Metro Line 3.