Inner Doha Re-sewerage Implementation Strategy (IDRIS)
The Qatar Public Works Authority (Ashghal) initiated a significant infrastructure programme called the Inner Doha Resewerage Implementation Strategy (IDRIS), with aim to modernise and improvise the sanitation system in the southern part of Doha, the capital city of Qatar. The project will upgrade the existing sewerage system, which consists of shallow sewers, and numerous pumping stations through the development of major deep tunnel sewer network and advanced sewage treatment works.
A main trunk sewer is 45 km in length, internal diameters between 3 m and 4.5 m and depths between 20 m to 55 m. The first contract, which includes construction of the three northern segments of the main trunk sewer in central Doha, was awarded to Bouygues Travaux Publics-Urbacon Trading & Contracting WLL and Bessac SAS JV. Tunneling length of this project is approximately 16 km x 3 m diameter with 3 branches (Northern, Eastern & Western branches) including total 11 shafts (7 no. Work Shafts & 4 no. Access Shafts).
Bouygues Construction Qatar and UrbaCon Trading and Contracting won the third contract that includes the construction of the southern segment of the main trunk sewer, which will terminate at the new Doha South sewage treatment works. But unfortunately the project was hold due to some issues. Tunneling length of this project was approximately 14 km including total 8 shafts (3 no. Work Shafts & 5 no. Access Shafts).
Encardio-rite’s sister concern Encardio-rite Geosystems WLL in Qatar was entrusted with the monitoring instrumentation works for shafts and tunnels during excavations and TBM drive for civil construction; underpass road tunnel and underground metro subway stations. Scope of works included:
- Supply & Installations of geotechnical instruments and geodetic targets through subcontractors
- Supply, installation & automatic online monitoring of strain gauges through our web based data monitoring services.
- Supply, installation & automatic online monitoring of optical prism through our web based data monitoring services.
- Supply, installation & manual monitoring of crack meters
- Vibration monitoring during TBM drive
- Dilapidation survey (Pre-Post construction Survey) of all nearby structures, utilities, landscape and Road infrastructure.
Instrumentation used included:
- Inclinometers were used around shafts to monitor sub-surface lateral movements
- Standpipe piezometers were used to monitor groundwater levels during deep excavations
- Strain gages were used on lifting beam (slings for a spreader beam) and TBM thrust frame to measure load and to monitor the stress / strain of several elements of this thrust frame, during the start of the tunnel boring.
- Crack meters were used on subway tunnel walls to monitor existing cracks.
- Optical prism targets were used on retaining walls and columns of underpass to monitor 3D deformation during passing of TBM and settlement monitoring of metro underpass.
- Surface settlement points were fixed on surface, curbs, pavements, structures, utilities to monitor vertical movements during constructions.
- Vibration sensors were used along the tunnel to check whether the vibration caused with excavation equipments were within permitted limits.