Pit for Spillway Dam at the Bagaevsky Hydroelectric Complex

Pit for Spillway Dam

Stroytransgaz Group is building a facility strategically important for the whole country – the Bagaevsky hydroelectric complex – designed to solve the navigation problem on the lower Don River – in the Rostov Region. Pit excavation for a spillway dam is underway at the Arpachinsky Island construction site. 

The spillway dam with special gate mechanisms is designed to discharge flood water from a natural reservoir formed by blocking the Don River with the Bagaevsky hydroelectric complex. Excavation of a pit with an area of 427.5 thousand square meters for this spillway dam is currently underway. The pit depth mark will be 9.3 meters, and at the location of the apron* and safety bucket** – 13.5 meters. Water depression is required before excavation since the design mark of the pit bottom is below the usual water level of the Don River. Wellpoint systems are used to decrease the level of underground waters. These are pumping units consisting of wellpoint filters, water collector, and a pump. As the depth of the pit increases, the wellpoint filters are re-installed in tiers. By now, the wellpoint filters have already been reinstalled on the third tier. After the water depression, excavation will be carried out to a mark of minus 9.3 meters throughout the pit. Next, the water depression and, accordingly, excavation will be carried out at the apron location only. While works are in progress in the pit, water is pumped out continuously.

Wellpoint Filter Design

Wellpoint Device

“When the pit is ready, the arrangement of a concrete blinding will begin. A concrete blinding or, as they often say, a cushion is a thin layer of concrete used to cover a pit before laying the foundation. A concrete blinding not only creates a waterproofing layer, but also provides for a flat surface for the intermediate concrete base. This reduces the consumption of cement and sand mortar. Besides, a concrete blinding protects the foundation from groundwater and provides for better reinforcement,” explained Ivan Vakulenko, Head of the Construction and Erection Section at the Bagaevsky hydroelectric complex.

The construction state owner is the Federal State Unitary Enterprise Rostransmodernizatsiya.

Background:

*Apron is a platform in the downstream of a hydraulic structure strengthening the watercourse bottom, protecting it from erosion, balancing pulsations, and dampening the energy of water discharged into the waterway.

**Safety Bucket is an end device after the apron designed to prevent washing out of the main fastening elements in the downstream of spillway dams and acting as a cushioning pool to dampen the energy of waterflow.

Race is an area where the water surface adjoins the hydraulic structure. The head race is upstream the river, the tail race is downstream.

Project background:

The Bagayevsky hydroelectric complex is the most important infrastructure project not only for the Rostov Region, but also for the entire country. The hydroelectric complex under construction will be composed of a shipping lock with a central control room, upper and lower approach channels with mooring-guiding structures, a spillway and earth fill dam, a meandering fish bypass and spawning channel and a fish passage lock, industrial, service, engineering and auxiliary facilities, and housing for operating personnel. To ensure the navigation safety, channel-regulating dams are being constructed, as well as shore protection dams that will prevent the development of bank erosion processes (washout and collapse), protect from the impact of ship waves and reduce the negative impact of waters on the population living in these areas. In order to ensure guaranteed waterway dimensions (depth — 4 m, width — 80 m, bending radius — 500 m) in the section from the Kochetovsky hydroelectric complex site at the 3004.5 kilometre mark of the waterway of the Integrated Deep Water System (IDWS) to the Bagaevsky hydroelectric complex site at the 3089 kilometre mark of the IDWS waterway, dredging and river cut-off are envisaged.