The Countermeasure for Press-in Method on Lengthy SPSPs and the Confirmation of the Bearing Capacity Obtained by Pile Loading Test

抄録

A Steel pile sheet pile (SPSP) foundation on a viaduct construction site was designed and constructed using the press-in method combined with inner excavation. After driving the pile, the press-in method combined with inner excavation was not able to drive the piles into the ground to the required depth, so the press-in with water jetting method was adopted after considering environmental impact, economy, and work schedule. With the press-in with water jetting method, the pile was driven to the required penetration depth while water was pumped under high pressure through pipes internally attached to the pile. The press-in with water jetting method was selected as a piling method for the steel pipe sheet pile foundation which is adjacent to a river, a highway, and houses in a confined space. There has been no recommended bearing capacity formula for press-in with water jetting method in Japanese design specifications for highway bridges, so the information of the vertical resistance characteristics (end-bearing capacity, skin friction) and lateral resistance characteristics (modulus of horizontal subgrade reaction) of the foundation was determined by a loading test to obtain the properties of foundation after changing the pile driving method. Using chemical grouting to increase the ultimate bearing capacity is also discussed. According to the results of vertical loading test and horizontal loading test after ground improvement, the ultimate bearing capacity was confirmed to be greater than the designed value for Level 2 earthquake. The stress in the piles was confirmed to be smaller than the allowable value both for Level 1 and Level 2 earthquake. The Ste el pipe sheet pile foundation using the press-in with water jetting method combined with the grouting method had full structural abilities for Pier structures.