海洋井架结构非线性分析

根据海洋钻井井架实际结构特点,建立弹性基础上的三维有限元模型.按9种工况对某井架的有限元模型进行加载,并且在传统线弹性理论基础上加以改进,考虑非线性P-△效应的影响.应用有限元分析软件StruCAD进行分析计算,给出可靠的计算结果;并且系统分析结构的受力特点和影响因素,得出对于井架这类高耸结构应该考虑P-△效应的影响.

Mechanics analysis of offshore derrick

In this paper, macro- and micro- properties of natural marine clay in two different and representative regions of China are investigated in detail. In addition to in-situ tests, soil samples are collected by use of Shelby tubes for laboratory examination in Shanghai and Zhuhai respectively, two coastal cities in China. In the laboratory tests, macro-properties such as consolidation characteristics and undrained shear strength are measured. Moreover, X-ray diffraction test, scanning electron microscope test, and mercury intrusion test are carried out for the investigation of their micro-properties including clay minerals and microstructure. The study shows that: (1) both clays are Holocene series formations, classified as either normal or underconsolidated soils. The initial gradient of the stress strain curves shows their increase with increasing consolidation pressure; however, the Shanghai and the Zhuhai clays are both structural soils with the latter shown to be more structured than the former. As a result, the Zhuhai clay shows strain softening behavior at low confining pressures, but strain hardening at high pressures. In contrast, the Shanghai clay mainly manifests strain-hardening. (2) An activity ranges from 0. 75 to 1. 30 for the Shanghai marine clay and from 0. 5 to 0. 85 for the Zhuhai marine clay. The main clay mineral is illite in the Shanghai clay and kaolinite in the Zhuhai clay. The Zhuhai clay is mainly characterized by a flocculated structure, while the typical Shanghai clay shows a dispersed structure. The porous structure of the Shanghai clay is characterized mainly by large and medium-sized pores, while the Zhuhai clay porous structure is mainly featured by small and medium-sized pores. The differences in their macro- and micro- properties can be attributed to different sedimentation environments.