Deformation And Bearing Behavior Of Piles With Different Tip Angle In Sandy Soils

With the advantage of low-noise, no-pollution and small vibration,jacked piles have been widely used in coastal cities. While penetration,jacked piles will cause the deformation of soil layer. With the deformationof soil layer, additional stress and other damages will happen to theunderground structures nearby. Specially to piles with tip angle, there’slittle research. This research is on jacked piles with different tip angles,and combines laboratory test and numerical simulation together toanalyze deformation and bearing behavior induced by jacked piles withdifferent tip angles while penetrating in sand soils. The gist and primarynew findings of this dissertation includes:(1) Penetration mechanism of piles with different angles by modeltests. The tests are conducted in model chamber by CPT instrument withdifferent angle piles. It shows that the influence area is small at thebeginning, and it grows while the penetration depth increases. In the samepenetration depth, the bigger pile-angle is, the larger influence area anduplift will become. While piles with angles90degree,120degree and150degree penetrate, a deformation flat exists in the tip soil layer.Generally in sandy soils, end resistance increases linearly with thepenetration depth in a certain depth. In the same depth, the bigger theangle is, the bigger end resistance is.(2) PFC discrete element numerical simulation. Analyse thechanging rules of soil displacement field, end resistance and stress fieldwhile the pile angle is different by using discrete element numericalsimulation software. And analyse the influence of model factors in simulation. It concludes that the lateral displacement presents symmetricdistribution with two semicircle parts in each side of piles. Its value isinversely proportional to the distance from pile side. When the tip angleis small, subsidence of soil layer occurs mainly beside the pile tip. As theangle increases, subsidence of soil layer occurs mainly under the pile tipand near the lower part of pile.The distribution of soil stress is different as the tip angle of piles isdifferent. To pile with one certain angle, the end resistance increases asthe penetration depth increases. At the same depth, the end resistance isproportional to the tip angle of piles. Both tip angle and diameterinfluence the distribution of soil stress. In general, when tip angle is smalland diameter of pile is big, there are two stress concentration regionlocated at each side of pile tip. When tip angle is big and diameter of pileis small, there is only one stress concentration region located under piletip. The diameter of piles has little relationship with end resistance. In thesame depth, end resistance increases as diameter of piles increases. Whendiameter and angle keeps constant, the penetration velocity has littlerelationship with the distribution of stress. In the same depth, endresistance increases as the penetration velocity increases.