해상풍력발전기 암반매입 강관말뚝기초의 주면지지 거동

Abstract

This study have been researched on the shaft resistance behavior of drilled-in steel tubular pile in rock. Also, t-z curve which is a load-displacement relation on pile shaft was suggested by compressive strength and mixing ratio of filling materials. The behavior was not covered by the current design standards, in case of constructing drilled-in steel tubular pile in rock, it is expected to be useful for the more accurate evaluation of shaft resistance and for the more economic design. Mechanism of shaft resistance is expected to be determined by the smallest among the shear strength of the rock, the filling material themselves, between the rock and the filling material, or the strength between the pile and the filling material. Therefore, it has been carried about quantitative assessments on the expected failure modes by indoor testing. Among the volcanic rocks, those in Jeju have irregularly distributed pores which are generated during the formation process, and their effects on physical and mechanical characteristics were assessed and correlation was performed through indoor tests. Also, the change of the compressive strength was confirmed by the material test according to the composition of fine aggregate and water/cement ratio. The shear strength between the filling material and the rock is evaluated according to the compressive strength of the filling material and the presence of pores in rock. Rock without pores was affected by the compressive strength of the filling material, but in the rock with largely distributed pores, it showed similar values regardless of the compressive strength of filling material. The shaft resistance behaviors between drilled-in pile and filling material were tested according to the mixing ratio of filling material. As a result, it was advantageous to use mortars rather than cement paste. If mortar is used, bearing capacity decreased with increasing water/cement ratio, and the bearing capacity increased with increasing fine aggregate, but decreased at a certain value or higher. As a result of examining the failure mode of the pile shaft based on the previous test data, the shaft resistance was occurred between the filling material and the steel tubular pile because the shear strength between the steel tubular pile and the filling material was the lowest and the support area was the smallest. Based on the shaft resistance behavior between steel tubular pile and filling material, shaft resistance model was proposed, and the results of the validation were generally well simulated. By applying the proposed model, the numerical analysis of pullout behavior of the drilled-in steel tubular pile in rock was carried out. As a result, the characteristics of behavior depending on the diameter, thickness, and embedded depth of the pile is analyzed.