Research On Vertical Bearing Capacity Of Cyclically Change Diameter Pile

In recent years, because of high single pile bearing capacity, the cheapprice,convenient construction,prestressed concrete pipe pile has been used widely infoundation engineering, but its prone to brittle failure, the tensile strength is low, thebearing capacity is difficult to give full play in the soft soil, the compaction effect isserious.In response to above problems, the profiled pile which is gradually developedand applied in the practice showing great value in engineering,such as high bearingcapacity, small settlement, save material, suitable for a variety of soil type, etc.Previous studies have focused on soft soil foundation, and the main research is thebearing capacity of single pile, this paper proposes a new pile type,the cyclicallychange diameter pile (PHB pile), that set annular convex rib which is500mm longevery2meters in the ordinary high strength prestressed concrete pipe pile(PHCpile),carry out test under the condition of powder geological in Xinzheng, Henan andanalyze the load-bearing characteristics of variable diameter section pile, in order topromote the technological innovation and development of variable diameter sectionpile.This paper theoretically comparative analys is the work mechanism of PHB pileand PHC pile in vertical compressive and pull strength, and composite foundation,adopts the method of field static load experiment, respectively test the bearingcapacity of PHB and PHC pile in vertical compressive, pulling resistance andcomposite foundation, then, get the following results:(1) By analyzing PHC pile that outer diameter is the same to PHB sectiondiameter single pile test results, we found that the bearing capacity horizontal of PHBoverall was lower than PHC pile, but under the same load, the top settlement of PHBpile is large than the PHC pile; PHB pile end resistance play earlier than the PHC pile,compared with the PHC pile, end resistance bear more vertical load, show thecharacteristics of the end bearing friction pile; the lower level of PHB pile upliftbearing capacity is less than the lower level of compressive bearing capacity. (2)By analyzing PHC and PHB pile single uplift pile load test, we found that thebearing capacity horizontal of PHB overall was lower than PHC pile, but PHBtension coefficient is high than PHC.(3)Through the analysis of PHC and PHB reinforcing pile composite static loadtest results in which PHC pile outer diameter is the same to PHB section diameterPHB and PHC pile,we found that PHB limit bearing capacity is similar to PHC pile,under this soil condition, PHB will save certain dosage of concrete pile, therefore ithas very good application prospect when used in composite foundation.(4) By comparing the PHB single pile static load test and single pile compositefoundation static load test results, we get that, in the composite foundation,the sidefriction resistance of the upper part of the pile play degree of composite pile is weaker,but in the lower part of the pile, the play degree is higher than PHB free single pile.