Design and construction of an anchored soldier pile wall for a large underground car park

Abstract

The geotechnical conditions of the soil and the construction conditions of a retaining wall for an underground twolevel car park project are described. The project is located in Concepcion’s downtown, south of Chile. The excavation support had to prevent any damage for the Courts of Justice historic building and surrounding buildings. These are buildings between four and nine floors and the Hites building is also classified as a historical building. Also, any cutoff of water, sewage, gas and electricity had to be avoided. The solution adopted was an anchored soldier pile wall of 8 m depth around the excavation, where the soldier piles (H section steel piles) were driven into semi dense silty sand. Two lines of anchors were designed vertically and horizontally separated by 3 m and 3.2 m respectively. The design loads for the anchors ranged between 300 and 560 kN respectively. The installation and placement of anchors was studied in order not to disturb the different stages of construction. The project included 3596 m2 of anchored soldier pile wall with 314 post-stressed anchors and 300 soldier piles totalling 3200 m. It is concluded that the temporary excavation support solution adopted performed properly to the high demands set, since no important deformations were noted in the building of Courts of Justice, in the surrounding buildings or in the services of drinking water, power, gas or electricity. The city of Concepcion was severely struck by an 8.8 moment magnitude earthquake on the 27th February 2010. The construction of the underground car park was just ready when the earthquake occurred. No damage was observed in the car park due to the seismic event. It is believed that the buried soldier pile wall reduced the seismic loads acting on the underground car park structure since no evidence of damage exists after the very big earthquake. Keywords: Anchored soldier pile wall, silty sandy soil, excavation support construction sequence.