Study on the Elasto-plastic Behavior of Open or Closed end Pile

开端封闭桩弹塑性行为研究

• 批准号: 61550412
• 负责人: NAGAI Koushiro
• 金额: $ 1.34万
• 依托单位: Kyoto Kogeisen'i Daigaku(Kyoto Institute of Technology)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1986
• 资助国家: 日本
• 起止时间: 1986 至 1987
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-61550412/
• 关键词: Arching; Vertical load; Stress distribution; Pile; Load test; Sandy soil; Bearing capacity; ダイレイタンシー; 鋼; 地盤; 摩擦; 有限要素法

1. The bearing capacity of pipe piles is statically indeterminate on account of increasing in diameter. The force per unit area shows a tendancy to vary as the ratio of thicknes to diameter as the load is made larger and the mechanism, which transfers end resistance to the upper part of piles between the extent which is twice as long as diameter at the tip ,is formed, but it may vary as the diameter as long as the load is small.2. The behaviours of open or closed pile were simulated by the F.E.M analysis, and then it is presumed that the ground will be settled by the pile mainly under the cone formed by the principal stress direction due to the ultimate state of friction near the pile top.(1) The inner soil settles with the pile so that the inner friction is negligible except the pile tip At the pile tip, however, outer or inner friction is larger than other part owing to arching of sand particles.(2) In the case of the open pile, sand near the tip did not fail but near the top failed. … More (3) In the case of the closed pile, in which the rigid stratum at 5m under the tip which plugged by the concrete between the extent which is twice as long as pile diameter, the friction reached the ultimate value in order from the rip to the upper part and the sand near the tip was failed.(4) From the above mentioned ultimate state of friction and the failure of sand, the usual yielding load and 'the first ultimate load', named by Kishida and Takano, were observed in order.3. For improvement of friction element and unloading element of sand after failure in the method, the displacement control or flexibility method must be introduced. The stres values of sand near the tip reach the particle crushing range so that the constitutive law must be improved also. Errors of circumferential strain near the axis of symmetry or the precise definition of stress and strain must be investigated.4. For the above mentioned improvement, triaxial test method with end frictionless pieces was established and the test will be conducted by strain control. Less

1.由于管桩直径的增大，其承载能力具有静力不确定的特点。随着荷载的增大，单位面积内力呈现出随厚度与直径之比变化的趋势，形成了将端阻传递到桩端直径两倍于桩端直径的范围的机构，但只要荷载较小，它就会随着直径的变化而变化。通过有限元分析，模拟了开口桩和闭合桩的受力行为，并假定桩在桩顶附近的极限摩擦状态下，将主要由桩在主应力方向形成的锥体下沉：(1)桩内土体与桩共同沉降，除桩端的桩端外，其他部位的内摩阻力可忽略不计，但由于砂粒的拱化，外、内摩阻力较大。(2)对于开口桩，桩端附近的砂粒不会破坏，而是顶部附近的砂粒破坏。…(3)对于桩端以下5m处的刚性层被混凝土堵塞在桩径的两倍之间的情况下，摩擦力按从裂缝到上部的顺序达到极限值，端部附近的砂土破坏。(4)从上述极限摩阻状态和砂土的破坏情况来看，通常的屈服荷载和Kishida和Takano所称的第一极限荷载是依次出现的。对于砂土失效后的摩擦元件和卸荷元件的改进，必须引入位移控制或柔度法。尖端附近砂土的应力值达到颗粒破碎范围，本构关系也有待改进。必须研究对称轴附近的周向应变误差或应力和应变的精确定义。为进行上述改进，建立了端面无摩擦试件三轴试验方法，采用应变控制进行试验。较少

项目成果

永井興史郎: 第22回土質工学研究発表会. 1179-1180 (1987)

永井幸四郎：第 22 届土壤工程研究报告 1179-1180 (1987)。

NAGAI,Koushiro: "A Numerical Analysis of Open Pipe Piles considered of inner and outer soils" Proc. of 22th Annual Meeting of J.S.S.M.F.E.1179-1180 (1987)

NAGAI，Koushiro：“考虑内部和外部土壤的开管桩数值分析”Proc。

永井興史郎: 日本建築学会大会学術講演梗概集. 1035-1036 (1987)

永井幸四郎：日本建筑学会会议学术讲座摘要 1035-1036（1987 年）。

永井興史郎: 日本建築学会近畿支部研究報告集 第27号構造系. 27. (1987)

永井幸四郎：日本建筑学会近畿分会研究报告第27号结构体系。（1987）

NAGAI,Koushiro: "A Numerical Analysis of Open Steel Pipe Piles considered of Surrounding Soils" Proc. of Annual Meeting of Kinki Branch of A.I.J.27. 233-236 (1987)

NAGAI，Koushiro：“考虑周围土壤的开口钢管桩的数值分析”Proc。