KPONE Independent Power Plant

Onshore Foundation Works

The KPONE Independent Power Plant (KIPP) is located in the Kpone neighborhood of the port city of Tema which is approximately 32 km east of Accra, the capital and largest city in Ghana. The new power plant is designed with a seawater cooling system which requires therefore an underground connection into the open sea. BAUER Spezialtiefbau GmbH was awarded to design and install retaining walls for two circular access shafts and one semi-circle intake recovery shaft for the micro tunnel boring machine (MTBM) and in addition foundation piles for a nearby fire tank structure. This contract includes for all onshore foundation works. The underground tunnels excavated by the MTBM connecting the onshore access shafts to the offshore exit shafts at approximately 6 m below the sea bed level. The two onshore access shafts have a diameter of 12 m and a maximum excavation depth of 16.5 m to ensure the tunnel connection. A BAUER BG 28 drill rig equipped for kelly drilling method was mobilized to Ghana to execute the specified works. All bored piles have a nominal diameter of 1,180 mm in overburden soil and had to be socketed into rock (drilling tool diameter 1,060 mm). The rock embedment length was varying depending on the actual design requirements and ground conditions. The secant piles for the two access shafts had a maximum length of 19 m with a rock embedment of up to 6 m. The secant pile walls were executed as “hard / hard” pile walls with sufficient pile overcut to ensure design compliance. In addition reinforcement had to be installed into the secondary piles due to the required MTBM shaft openings through the installed secant pile wall. In the break through areas the steel reinforcement was replaced by glass fibre reinforcement. The onshore foundation works were completed in July 2016.