海底防沉板—桩复合基础承载特性数值分析

为了研究桩长对海底防沉板—桩复合基础在水平、弯矩和扭转荷载作用下承载特性的影响,以我国南海水深200 m的某工程实例为研究对象,利用Flac3D有限差分仿真软件建立了计算模型。研究了桩长为4 m、6 m和8 m的防沉板—桩复合基础在水平、弯矩和扭转荷载作用下的极限承载力和荷载传递机理。结果表明,桩长超过6 m时复合基础的水平承载力显著增长,在水平加载过程中,防沉板总是先达到极限状态而破坏,桩基础的贡献在加载后期体现,且桩长为4 m、8 m时,桩基础与防沉板的连接处弯矩最大;随着桩长的增加,复合基础的抗弯承载力大幅提高,桩基础对复合基础的抗弯承载力贡献增大,当桩长超过8 m,桩长的增加对提高复合基础的抗弯承载力意义不大;在弯矩加载过程中,桩长对于防沉板、桩基础的荷载分配有显著影响,桩长为4 m时,外荷载主要由防沉板承担,当桩长超过4 m时,外荷载主要由桩基础承担;当扭转荷载不超过2 100 k N·m时,防沉板承担主要荷载,直至防沉板达到极限状态而发生旋转,随后桩基础的承载力逐渐发挥;对于桩长为6 m、8 m的复合基础,其极限状态根据防沉板适用性准则确定。

Numerical analysis of the bearing capacity characteristics of subsea mudmat-pile composite foundations

In order to study the influence of pile length on the bearing characteristics of submarine mudmat-pile composite foundation under horizontal, bending moment and torsion loads, a calculation model was established by using Flac^3D finite-difference simulation software, taking an engineering example in the South China Sea at a depth of 200 m as the research object. The ultimate bearing capacity and load transfer mechanism of mudmat-pile composite foundation with pile lengths of 4 m, 6 m and 8 m under horizontal, bending moment and torsional loads were studied. The results show that the horizontal bearing capacity of the composite foundation increases significantly when the pile length exceeds 6m. In the process of horizontal loading, the mudmat always reaches the limit state first and is destroyed. The contribution of the pile foundation is reflected in the late loading stage. With the increase of pile length, the flexural bearing capacity of composite foundation increases significantly, and the contribution of pile foundation to the flexural bearing capacity of composite foundation increases. When the pile length exceeds 8 m, the increase of pile length has little significance for improving the flexural bearing capacity of composite foundation. In the process of bending moment loading, pile length has a significant influence on load distribution of mudmat and pile foundation. When the pile length is 4 m, the external load is mainly borne by the mudmat. When the pile length exceeds 4 m, the external load is mainly borne by the pile foundation. When the torsional load does not exceed 2 100 kNm, the mudmat bears the main load until mudmat reaches its limit state and rotates, and then the bearing capacity of pile foundation is gradually exerted. For the composite foundation with pile lengths of 6 m and 8 m, its limit state is determined according to the applicability criterion of mudmat.