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

摘要

The geotechnical conditions of the soil and the construction conditions of a retained wall for an underground car park project of two levels are described. The project is located in the centre of the city of Concepción, south of Chile. The excavation support had to avoid any damage of the Tribunals of Justice historic building and the surrounding buildings. Other buildings have between four and nine floors and the Hites building is also classified as a historical building. Also, it has to be included the avoidance of any interference with facilities and services such as water, sewage, gas and electricity. The solution adopted was an anchored soldier pile wall of 8 m of 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 separated vertically and horizontally 3 m and 3.2 m respectively. The design loads for the anchors were calculated between 300 and 560 kN. In particular, the anchors installation and placement were studied in order to not disturb the different stages of construction. The project included 3596 m 2 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 adequately to the intricate conditions, since no observable deformation in the Tribunals nor in the surrounding buildings nor in the services occurred during construction. Concepción city was severely struck by an 8.8 moment magnitude earthquake on the 27 th 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 may reduce seismic loadings acting on the underground car park structure since no evidence of damage exists after the very big earthquake.