船舶与海洋工程
船舶與海洋工程
선박여해양공정
Shanghai Shipbuilding
2015年
3期
16-21
,共6页
自升式平台%地基承载%罚函数法%速度逆差%动力接触
自升式平檯%地基承載%罰函數法%速度逆差%動力接觸
자승식평태%지기승재%벌함수법%속도역차%동력접촉
Jack-up platform%foundation bearing capacity%penalty function method%velocity gradient deficit%dynamic contact
现有自升式平台强度设计中地基承载力采用静态设计法，将地基作为一种不变的边界条件，将桩土作用简化为泥面下简支约束，从而忽略了地基土的非线性及低强度特性。桩土贯入过程属于动态高度非线性、大变形问题，土体流动特性对桩端承载影响很大。建立桩土有限元模型，采用任意拉格朗日-欧拉法（ALE）模拟桩土贯入，利用罚函数法求解桩土面-面动力接触效应。分析结果表明：桩靴上部空腔破坏，土体回流冲击桩靴上端面，并在桩靴上下端面形成速度逆差，造成桩靴下部形成瞬态吸力，使桩端承载骤增。因此采用静态设计法得到地基承载能力低于实际贯桩桩端承载，由此提出了这样的问题：按照现行规范进行地基承载能力设计，会导致地基承载能力不足。
現有自升式平檯彊度設計中地基承載力採用靜態設計法，將地基作為一種不變的邊界條件，將樁土作用簡化為泥麵下簡支約束，從而忽略瞭地基土的非線性及低彊度特性。樁土貫入過程屬于動態高度非線性、大變形問題，土體流動特性對樁耑承載影響很大。建立樁土有限元模型，採用任意拉格朗日-歐拉法（ALE）模擬樁土貫入，利用罰函數法求解樁土麵-麵動力接觸效應。分析結果錶明：樁靴上部空腔破壞，土體迴流遲擊樁靴上耑麵，併在樁靴上下耑麵形成速度逆差，造成樁靴下部形成瞬態吸力，使樁耑承載驟增。因此採用靜態設計法得到地基承載能力低于實際貫樁樁耑承載，由此提齣瞭這樣的問題：按照現行規範進行地基承載能力設計，會導緻地基承載能力不足。
현유자승식평태강도설계중지기승재력채용정태설계법，장지기작위일충불변적변계조건，장장토작용간화위니면하간지약속，종이홀략료지기토적비선성급저강도특성。장토관입과정속우동태고도비선성、대변형문제，토체류동특성대장단승재영향흔대。건립장토유한원모형，채용임의랍격랑일-구랍법（ALE）모의장토관입，이용벌함수법구해장토면-면동력접촉효응。분석결과표명：장화상부공강파배，토체회류충격장화상단면，병재장화상하단면형성속도역차，조성장화하부형성순태흡력，사장단승재취증。인차채용정태설계법득도지기승재능력저우실제관장장단승재，유차제출료저양적문제：안조현행규범진행지기승재능력설계，회도치지기승재능력불족。
In the existing jack-up platform strength design the static design method has been adopted for foundation bearing capacity, which takes the foundation as a fixed boundary condition while the spud can boundary condition is simplified to be a simple support under mud, thus neglecting the nonlinearity and low strength characteristic of the foundation soil. The pile-soil penetration process is dynamic, highly nonlinear and with large deformation, so the influence of mud flow characteristics on the spud can bearing capacity is very large. This paper establishes the foundation finite element model, uses the arbitrary Lagrange Euler method (ALE) to simulate the pile-soil penetration, and adopts the penalty function method to solve the face-to-face dynamic contact effect. The analysis result demonstrates that the spud can upper vacuum is damaged, back-flow of mud impacts the upper spud can surface and creates a velocity gradient deficit between the upper and lower ends of the spud can, leading to a transient suction at the lower part of the spud can, increasing the spud can bearing capacity abruptly. Therefore, in accordance with the current design regulation the foundation bearing capacity obtained by static design method would be lower than the actual value, demonstrating a deficient foundation bearing.
