Thach Nham Weir Project

Project location: Tra Khuc river - Quang Ngai province
Construction time:
- Commencement: 1/1/1986
- Completion: 1995
Project tasks:
- Irrigating 50,000 ha (of which, creating source for 5,000 ha)
- Supplying water for industrial and domestic uses
- Small hydropower stations on canals
Major technical parameters:
- Catchment area: 2836 km²
- Work grade: I
- Irrigation frequency P = 75%
- Design flood frequency: P = 1%
- Maximum flood discharge Qmax 1%: 17,400 m³/s
Scale and structure of project works:
- Headworks: gravity concrete weir on Tra Khuc river with length L=200m (13 spans), Hmax: 26.6m.
- Bucket type energy dissipator, connection to downstream with submerged flow regime
- Intake and sand sluice in north bank: two floors, the sand sluice is located in the lower floor, the intake is located in upper floor, constructed of reinforced concrete with steel plain gate, reinforced concrete stoplog is electrically operated, dimensions are as follows:
+ Turnout: n(b x h) = 2 x (2.5 x 2.5)m
+ Sand sluice: n(b x h) = 2 x (2.0 x 2.5)m
+ Design discharge of turnout: 23.5 m³/s
- Intake and sand sluice in south bank, constructed of reinforced concrete, separately located, steel plain gate is electrically operated, dimensions are as follows:
- Turnout: n(b x h) = 2 x (2.5 x2.5)m
- Sand sluice: n(b x h) = 3 x (2.5 x 3) m
- Design discharge of turnout: 31.5 m³/s
- Canal system:
. North main canal: 30.3 km long
. South main canal: 57 km long
. 28 primary canals (of North and South canals): 235 km long
. 1200 related structures
. 14 electrical pumping stations
. Branch canals (smaller than primary canal): 950 km long
- In the canal system, there are many huge structure such as Ve river siphon with design discharge of 12.5 m³/s. Beside, there are many related structures which have been applied first time such as overchute, submersible aqueduct, suspended siphon. Two structures were awarded high quality consultancy certificate.
- Construction of dam foundation was very complicated as there was a deep alley in the river bed, the problem was well treated.