육각형 이음부를 갖는 회전관입말뚝의 지지력 특성

Abstract

Helical pile is a pile foundation made of hollow axial pipe with one or more helical plates attached. It is inserted into the ground rotating to obtain required bearing capacity and no noise construction is available since it does not requires hammering and drilling process. Helical pile can be constructed only by a rotary penetrator which leads rotating penetration up to the depth required and has following advantages: 1) relatively small equipment is needed, 2) easy to control, 3) can be constructed at site with limited area including commercial area or historic site. Also, helical pile is advantageous to the existing steel pipe pile in bearing capacity per material cost since each helical plate whose diameter is bigger than hollow axial pipe where it is attached can generate end bearing capacity. Until 19th century, bearing capacity of pile was usually estimated empirically, while ultimate bearing capacity theories were introduced by Prandtl, Terzaghi and esc after the Rankine’ searth pressure theory presented in 19th century. In this study, a model of hollow shaft was improved to have a hexagonal form, which has a unique joint, so that it was improved to be a type that does not require welding or bolts during the compression load. In addition, two fields consisting of the most common ground were selected to perform field tests for applying it to domestic ground. Then, this author examined whether a method of predicting bearing capacity is appropriate by comparing the results of dynamic load test, static load tests and pull-out tests at field loading tests with the bearing capacity predicted by measuring torque force at the field test construction. According to the results of field loading tests, the bearing capacity of a pile grouted was more than 600kN during the dynamic load test and static load tests by AC 358 Code, and the bearing capacity of a non grouted pile was less than 600kN. It shows that grouting should be performed for the rotary penetration pile. Moreover, the bearing capacity was predicted by considering the field load tests and the rotational torque (T) during construction. It is considered that this should be improved by securing data through continuous field loading tests and field test construction.