THE RIEM-ARCADE is a business and shopping centre with underground garage being built at the Riem exhibition centre in Munich, southern Germany.
Covering about 62,400m 2, the six-storey building will have three underground levels. The basement slab will lie about 12m below ground level and 8m below the groundwater level.
This meant a sheet pile wall had to be installed to allow basement construction. This is secured by two rows of anchors.
The 24m long Larssen 606 double sheet piles weigh 4.6t and had to be installed through very dense gravel, sand and silt.
After consulting with LiebherrWerk Nenzing and BVV Spezialtiefbautechnik Vertriebs, contractor Harald Gollwitzer decided to install the sheet piles using two LRB 250 Liebherr piling rigs.
Both are fitted with a high frequency PVE vibrator with variable static moment and a centrifugal force of 1750kN is being used to install the piles. The vibrator's 2002 static moment ensures maximum penetration of the sheet pile.
Low pressure jetting of water through pipes fixed on the sheet pile wall is also being used to aid installation.
Water, combined with vibration, causes fine soil particles to concentrate around the pile.
Jetting creates a channel along the pile which the fines are transported up, reducing friction and helping penetration. Each machine installed an average of 450m 2of sheet piles in one shift.
The LRB 250 rigs have adjustable leaders so piles can be adjusted vertically, even during vibration. They also have a rope crowd system with a maximum 30t pull force that ensures the pile and vibrator gear box are continuously in a harmonic sine wave which guarantees optimum penetration of the sheet pile.
The rigs are fitted with Liebherr's PDE process data recording system which documents the entire piling process.
The piling rig operator can access specific operation data including vibration time, penetration depth and vibration frequency.