선 굴착 PHC 말뚝의 시간경과에 따른 주면마찰력에 관한 고찰

Abstract

As pile foundation works are increasing in urban farm stalls and residential areas, the concerns about environmental issues are increasing. Pre-bored pile method which is a method with low noise and vibration has been applied a lot. To adapt to these changes in conditions, the method in which once we dig the ground, we inject cement milk and then insert the precast pile, is chosen. In case of general pre-bored pile, design and construction management is conducted by injecting cement milk to secure the skin friction and fix the central location of pile. However, sometimes cement milk is injected uniformly onto the full length of pile upon the decision of which injection of cement milk increases the skin friction regardless of soil condition of weathered soil and cohesive soil. The purpose of this study is to determine when the skin friction bearing of pile comes to the stabilization step, to present the most optimal time for superstructure construction over time, and to investigate the degree of influence of injected cement milk on actual skin friction according to soil condition and the necessity of injection of cement milk uniformly. It is examined what kinds of behavior does bearing power partition progress show over times under conditions of point bearing pile classified into weathered and cohesive soils, depth consistency and injection of cement milk through dynamic load test. Analysis showed that the optimal time for superstructure construction on ground of cohesive soil was 7 days. However, it’s shown that the effect of injection of cement milk on ground of cohesive soil was not big, since the changes in friction were similar regardless of injection of cement milk. In case of weather soil, age caused by milk injection was dominant. It would be economically feasible if skin friction is considered as bearing power on 21 days of the most optimal time for superstructure construction upon the design.