Bedford Dam, situated on the mountains above Ladysmith, Kwa-Zulu Natal, South Africa is a 49m high Concrete Face Rock-Fill Dam (CFRD) with an 810m crest length. This dam structure forms the upper reservoir of the Ingula Pumped Storage Scheme. During construction the river diversion works consisted of channels, a cofferdam and a training wall where the Main Contractor Bedford/Bramhoek Dams Joint Venture (BDJV) trained their personnel and honed their dam building skills.
The Main Embankment (480m) has a 170m Long clay core extension and 42m dry well single-level intake tower.
The Dam capacity is 22.4 million m³ with an active water storage volume of 19.2-million m³.
Bedford Dam Instrumentation consists of the following:
- Convergence points in the Outlet-Tunnel measuring expansion/contraction.
- Vibrating Wire Strain Gauges in and around the Outlet-Tunnel, measuring concrete and re-enforcing strain.
- Vibrating Wire Load Cells and Vibrating Wire Pressure cells around and on top of the Outlet-Tunnel, measuring total load and pressure.
- Vibrating Wire Piezometers in the Clay Core of the coffer wall/embankment, measuring pore pressure.
- Five sets of Vibrating Wire Perimetric Joint Meters are installed on crucial structural points on the plinth and the concrete face slab, measuring three-dimensional movement between the plinth and the starter slab.
- Eighteen Vibrating Wire Embedment Jointmeters are installed in the top parts of the various vertical joints of the concrete face slab measuring movement between the joints.
- Two Horizontal Inclinometer casings on the face slab measuring deflection of the face slab as such.
- Vibrating Wire Settlement Cells in the rock-fill for measuring settlement.
- Standpipe Piezometers for measuring water table.
- Vibrating Wire Transducer measuring seepage.
Instruments installed in and around the Dam Embankment are intended to monitor:
Installed Instruments Specification:
- Settlement of the Embankment;
- Opening of the concrete face slab joints;
- Stresses and deflection in the face slab concrete;
- Stresses, strains and convergence of the Conduit;
- Pore pressure build-up around the Conduit and Main Embankment.
Designers: Steward Scott Incorporated (SSI)
- Seepage (Dam, Conduit and Spillway)
- • Geokon Vibrating Wire Transducers Vented Model 4580
- Piezometers (Clay Core against Retaining Wall)
- • Geokon Vibrating Wire Model 4500S
- Joint Meter (Concrete face and plinth)
- • Geokon Vibrating Wire Model 4400
- Strain Gages (Face and Conduit)
- • Geokon Vibrating Wire Model 4210/4200/4202
- Pressure Cells (Conduit and Main Embankment)
- • Geokon Vibrating Wire Model 4800
- Settlement Cells (Fill)
- • Geokon Vibrating Wire Model 4650
- Convergence Meters (Conduit)
- • Geokon Model 1610 Tape Extensometer
- Data Acquisition System CR800/1000 (Valve House)
- • Geokon Micro-1000 Data logger Model 8021
- • Geokon Multiplexer (MUX) Model 8032
, Arcus Gibb
and Knight Piésold
Braamhoek Consultants Joint Venture (BCJV) comprises three of the country's mayor consulting firms namely Steward Scott Incorporated (SSI)
, Arcus Gibb
and Knight Piésold
Contractors: Concor Roads & Earthworks
, Wilson Bayly Holmes-Ovcon (WBHO)
, Edwin Construction and Silver Rock (BDJV)