Technical Specifications for Monitoring Ground Displacements at a National Highway Project K. Lakakis, P. Savvaidis and I. Ifadis Laboratory of Geodesy Dept. of Civil Engineering Aristotle University of Thessaloniki Greece

Highway construction and deformation problems Highway projects are very important national public works. The safety during construction and operation of such facilities is a prime concern for all agencies and companies involved. Large parts of a highway may pass from mountains and hills that locally appear to suffer from surface soil displacement problems. Highway projects are very important national public works. The safety during construction and operation of such facilities is a prime concern for all agencies and companies involved. Large parts of a highway may pass from mountains and hills that locally appear to suffer from surface soil displacement problems.

For tunnels: a geodetic methodology for the determination of the deformations in the interior of tunnels during and after the completion of the technical works. Technical specifications for the procedures that have to be followed by contractors for the measurement, processing of data and estimation of displacements must be derived. Highway construction and deformation problems The methodology for ground deformation measurement procedures: repeatedly observed local geodetic control networks (Reference stations – control points)

The EGNATIA ODOS Highway Egnatia Odos is a 700 Km highway extending from East to West in Northern Greece; it is also part of the European Transport Networks.

Monitoring ground displacements GPS control networks In each area, three trigonometric points of the National Geodetic Network are used as reference points. The number of the control points and the selection of their site are governed by the topography of the area and the specific requirements of the project. In each area, three trigonometric points of the National Geodetic Network are used as reference points. The number of the control points and the selection of their site are governed by the topography of the area and the specific requirements of the project. In the case of local deformation areas along the highway, a rather simple geometric scheme can be used for the local control networks:

A free network adjustment of the complete network (both reference and control stations included) is done for the epoch A similarity transformation is used to obtain a common reference system between the coordinates of the points of the specific epoch and the coordinates of the points of the zero measurement. The displacement of each point is computed as the difference between the zero measurement coordinates and the corresponding transformed last epoch coordinates. A free network adjustment of the complete network (both reference and control stations included) is done for the epoch A similarity transformation is used to obtain a common reference system between the coordinates of the points of the specific epoch and the coordinates of the points of the zero measurement. The displacement of each point is computed as the difference between the zero measurement coordinates and the corresponding transformed last epoch coordinates. Monitoring ground displacements Computation of deformation

 A very useful tool for monitoring of the displacements.  It consists of 3 basic parts: the Horizontal deformation, the Vertical derformation and the Table part.  A very useful tool for monitoring of the displacements.  It consists of 3 basic parts: the Horizontal deformation, the Vertical derformation and the Table part. Monitoring ground displacements Storing deformation data The Deformation History Point Card The Deformation History Point Card

Monitoring ground displacements The Deformation History Point Card – Basic parts

The deformation-monitoring project at Peristeri Monitoring ground displacements A deformation monitoring project - example

 29 stations (3 reference stations and 26 control points)  13 L1/L2 GPS receivers (5 GEOTRACER 3220, 2 LEICA 9500, 2 LEICA 520, and 4 TRIMBLE GPS)  267 vectors at each epoch.  29 stations (3 reference stations and 26 control points)  13 L1/L2 GPS receivers (5 GEOTRACER 3220, 2 LEICA 9500, 2 LEICA 520, and 4 TRIMBLE GPS)  267 vectors at each epoch. Monitoring ground displacements A deformation monitoring project - example Detail of deformation vectors

Monitoring tunnel deformation Surface control network A surface control network extending along and across the tunnel axis. It consists of reference stations located at geologically stable areas and monitoring or control stations that are located along the surface projection of the tunnel axis and in front of the tunnel entrances The surface control network can be used for monitoring surface ground deformation as well as for setting out the tunnel during construction. A surface control network extending along and across the tunnel axis. It consists of reference stations located at geologically stable areas and monitoring or control stations that are located along the surface projection of the tunnel axis and in front of the tunnel entrances The surface control network can be used for monitoring surface ground deformation as well as for setting out the tunnel during construction.

Monitoring tunnel deformation Monitoring deformation inside the tunnel Monitoring tunnel deformation Monitoring deformation inside the tunnel Control points at certain tunnel profile cross sections (e.g. every 20 m) (at least 5). Monitoring their movements with time can give information about the deformation along and across the tunnel and help the determination of abnormal behavior thus preventing possible damage. Control points at certain tunnel profile cross sections (e.g. every 20 m) (at least 5). Monitoring their movements with time can give information about the deformation along and across the tunnel and help the determination of abnormal behavior thus preventing possible damage.

Methods for tunnel cross-sections measurement: The conventional traverse measurement. The “free stationing” method. Laser profiling Photogrammetric Methods for tunnel cross-sections measurement: The conventional traverse measurement. The “free stationing” method. Laser profiling Photogrammetric The best procedure for the measurement of the underground control points is still under investigation Monitoring tunnel deformation Methods of measurement Monitoring tunnel deformation Methods of measurement

Deformation monitoring software evaluation According to the experience from projects of the Egnatia Odos S.A., the most suitable software must: Combine measurements of different geodetic instruments (e.g. GPS receivers, total stations, theodolites etc.) Give tools for outlier detection and statistical evaluation of raw measurements. Allow all kinds of least square adjustments of GPS, horizontal and vertical control networks. Give tools for transformation of coordinates. Use methods of deformation analysis with the capability of deformation modelling and prediction. Have an efficient and user-friendly interface and graphical view of results, specially adapted to tunnels (profiles and cross section displacements, comparison to theoretical values etc.). Allow the use of robotic total stations and real time presentation of deformations with alarm capability. According to the experience from projects of the Egnatia Odos S.A., the most suitable software must: Combine measurements of different geodetic instruments (e.g. GPS receivers, total stations, theodolites etc.) Give tools for outlier detection and statistical evaluation of raw measurements. Allow all kinds of least square adjustments of GPS, horizontal and vertical control networks. Give tools for transformation of coordinates. Use methods of deformation analysis with the capability of deformation modelling and prediction. Have an efficient and user-friendly interface and graphical view of results, specially adapted to tunnels (profiles and cross section displacements, comparison to theoretical values etc.). Allow the use of robotic total stations and real time presentation of deformations with alarm capability.

OBSERVER: Mainly an alarm software because it can understand changes in the geometry of the tunnel or the landslide. No significant statistical and adjustment tools. Arc-Tech: Presentation software of surveying data in the tunnel. No adjustment capabilities. DEDALOS: A software package for deformation monitoring inside a tunnel. It is based on the free stationing method and has some least squares adjustment capabilities. PANDA: A software package for deformation analysis of structures and landslides. It can combine measurements of different geodetic instruments; it has adjustment capabilities but no effective graphical presentation of tunnel deformation. APSWin: A software package for continuous monitoring of targets with the help of a robotic total station, real time computation of deformation and alarm capability. Deformation monitoring software evaluation Software packages Deformation monitoring software evaluation Software packages

The use of many local control networks at places suspected of movement along the highway can give valuable information for the safety of the construction. The measurement scheme adopted (three reference stations at each site and GPS observations) seems to provide quick and reliable results. Also, the electronic «point card» for each control point helps the interpretation of its behavior in a simple and effective way. The technical specifications applied help contractors to follow a common and compatible measurement and processing methodology that is simple enough but also effective. The procedures for underground tunnel deformation monitoring have not been decided yet. It is planned that a pilot project will give valuable information about the effectiveness, the speed and the reliability of each method. The decision about the global use of a deformation analysis software package is also still under question. There is a possibility for the creation of a new software package fitted to the needs of specific deformation projects. Comments and Conclusions