Life-Cycle and Sustainability of Civil Infrastructure Systems – Strauss, Frangopol & Bergmeister (Eds) © 2013 Taylor & Francis Group, London, ISBN 978-0-415-62126-7 Automated geomatic system for monitoring historical buildings during tunneling in Roma, Italy M. Crespi, F. Giannone & M. Marsella D.I.C.E.A. Geodesy and Geomatic Area of the Faculty of Engineering – Università di Roma La Sapienza, Roma, Italy A. Sonnessa Survey Lab srl – Università di Roma La Sapienza, Roma, Italy ABSTRACT: The present work is focused on the preliminary results obtained through the geomatic integrat- ed monitoring system currently running at the test site of the Basilica of Maxentius in the Roman Forum. The system is aimed at controlling a number of archaeological sites which can be potentially affected by the tun- neling works for a new metro line which is presently under construction. It includes different high precision geomatic sensors controlled by a centralized control station which continuously acquire data at high frequen- cy. In order to identify a reliable processing procedure and assess the quality of the collected data, we started to develop and experiment a preliminary analysis of the data collected in the first period of the system opera- tion (before the start of the excavation works). This activity allowed us to assess the performance of each sen- sor, focusing on the capability of the system to control also the stability of the monitoring stations. The ob- tained results will be adopted to better define an automated procedure for future massive data processing. 1 INTRODUCTION The effects of the underground construction works in urban areas represent a threat for the stability of the overlying buildings and structures. The problem is particularly relevant when the damages can affect archeological sites and historical buildings, such as those located in the historical centre of Rome which, for cultural and architectonic heritage is listed by UNESCO as a World Heritage Site. In view of the works which are planned to start for the construction of the third underground line in Rome (Metro C line), a monitoring system, integrating ground and satellite based geomatic sensors, was designed and Figure 1. Plan view of the Metro C Line between San Giovanni partially installed in a number of test site within the in Laterano and Piazza Venezia. archeological area. The final configuration of the monitoring systems is designed to control the inter- action of the tunneling works with a number of 2 SYSTEM CONFIGURATION monuments between San Giovanni in Laterano and Piazza Venezia (Fig. 1). The present configuration includes base station sites The monitoring system is presently operating in a equipped with three geomatic sensors characterized beta version in three test sites: the Basilica of by high precision and by the capability of automati- Maxentius and Constantine in the Roman Forum, cally collecting high frequency data (Dominici et al. Aurelian Walls near Porta Asinaria and the Monu- 2008) (Mat et al. 2010): automatic total stations, ment to Vittorio Emanuele (Vittoriano). GNSS geodetic receivers, bi-axial inclinometers In this work we focus on the procedure adopted to (Tab. 1). Each station sites is also fitted with an unit assess the stability condition of the base station sites for measuring main meteo parameters (tempera- and on the preliminary results obtained from the ture/pressure) useful to extrapolate a corrective analysis of the data collected in the test sites of the model for detrending the displacement time series. Basilica of Maxentius and Costantine in the Roman The total station is a classical topographic instru- Forum. ment used for the measurement of slope distance, 1110 horizontal direction and vertical angles to compute sensors and are used to check the stability of the sta- the coordinates of any unknown point, in our case tion site. They are aimed at complementing the mon- monitoring points, relatively to the total station posi- itoring of short-term (daily) and long-term (seasonal tion (coordinates in the instrument reference sys- and more) stability of the station sites. In addition, tem). In order to compute the coordinates of sur- the site stability check is routinely carried out by the veyed points in an external reference system, it is automatic total stations themselves through a num- necessary to link the measurements to a reference ber of external reference points. Finally, the meteor- point or, better, to a network of points outside the ological sensors are devoted to continuously meas- monitored area. This is carried out by fixing the co- ure pressure and temperature providing daily and ordinates of the total station and estimating an angle seasonal trends that can be compared and jointly an- (the orientation angle) adjusting redundant observa- alyzed with the displacement time series in order to tions with the least square method. In our case the highlight the presence of correlated signals that orientation of the total station, is carried out using a should be not confused with the real structural set of point with known coordinates. movements. Table 1: technical features for the total station and the bi-axial 2.1 The Basilica of Maxentius Test site ______________________________________________inclinometer ______________________________________________Total Station The Basilica of Maxentius constitutes a monumental ______________________________________________Observable Accuracy complex among the more imposing in the archeolog- Horizontal direction and vertical angles 0,5” ical zone of Rome. The construction, begun by ______________________________________________Distance 1mm+1ppm Maxentius in 303 A. D., was interrupted by his death in 312, during the Battle "ad Saxa Rubra". In 313, ______________________________________________Bi-axial inclinometer Measuring range Accuracy Constantine completed the Basilica of which only ______________________________________________ one entire side and the main apse of the shorter side From To ______________________________________________ presently remains. Today, with part of the bold [mrad] [mrad] [mrad] vaults rising more than 35 metres from the ground. -1,5100 1,5100 +/-0,0047 -2,5100 2,5100 +/-0,0141 The monitoring system installed in the site of the Basilica of Maxentius is designed in order to ob- ______________________________________________-3,0000 3,0000 +/-0,0471 serve the remains of the monument by means of Automatic total station measures the monitoring three “monitoring towers/stations: ”Moncone”, posi- points every four hours. The GNSS receivers pro- tioned inside the Basilica and monitoring the south- vide 3D coordinates in a global reference frame west side, “Villino Rivaldi”, positioned outside the (Fastellini et al. 2011), while inclinometer measures Basilica and monitoring the north-east side, and two inclination angles along two perpendicular di- “Corrado Ricci”, positioned in Via dei Fori Imperiali rections (X and Y direction) respect to the vertical and monitoring the north-west part of the building position. Every measurement is acquired in the sen- (Fig. 2). sor own reference frame and subsequently trans- formed in a common reference frame named MetroC reference system. Presently, a daily solution is calcu- lated for the GNSS position, while inclinometer pro- vides its measurements every 20 minutes. Since at the present stage of construction, the tunneling has not yet reached the monitored monu- ments, the main objective of the monitoring system is to observe the behavior of the building in unper- turbed conditions. Thus, the data analysis can permit to evaluate the standard daily/seasonal displacement patterns which the structures undergo. This aim is obviously of crucial importance since it will allow to detect and quantify the movements which are not in- duced by the tunneling itself. Such movements can be filtered out enabling to highlight only critical Figure 2. Monitoring stations controlling the Basilica of structural deformations which can be used for early Maxentius warnings when given thresholds will be exceeded. The geomatic sensors are installed in suitable Figure 3 shows a tower instrumented with an au- sites and utilized for different aims: the main sensors tomatic total station, a GNSS geodetic receivers and are the automatic total stations devoted to the direct a bi-axial inclinometers. control of the structures, while the bi-axial incli- The whole monitoring system is totally automat- nometers and GNSS receivers behave as auxiliary ed following the user setting for acquisition rate, 1111 number of points to measure, measuring method, has been configured to acquire the coordinates of the etc.. Warning messages can be also set by the user if complete set of prisms every four hours. measurements exceed a given threshold, highlight- For each monitoring station, a set of reference points ing risks for the stability of the Basilica. (hereafter PR) of known coordinates, positioned on surrounding buildings which are not overlying the excavation area are provided in order to calculate the orientation of the total station. Figure 5 Position of the reference points 2.2 Analysis of the stability of the Monitoring Figure 3. Geomatic sensor installed on the monitoring towers towers The GNSS receivers and the bi-axial inclinometers The total stations are devoted to measure the co- are adopted to collect data useful to monitor the sta- ordinates of over 300 high precision micro-prisms bility of the towers. In case of manifest variations