循环荷载作用下吸力锚基础变形的数值分析方法研究  

Numerical method for the deformation of suction anchor under cyclic loading

作　　者：李书兆[1,2] 王建华[3] 

机构地区：[1]中海油研究总院,北京100028 [2]中国科学院力学研究所,北京100190 [3]天津大学岩土工程研究所,天津300072

出　　处：《岩土工程学报》2016年第12期2203-2211,共9页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金项目(51179120)

摘　　要：张紧式吸力锚是一种重要的深水海洋浮式平台锚固基础。静荷载与循环荷载共同作用下地基土体产生较大变形,严重影响吸力锚基础的稳定性。介绍了一种能够描述饱和软黏土不排水循环应力应变响应的拟动力黏弹塑性本构模型。该模型将等效黏弹性理论和蠕变理论相结合,利用等效黏弹性模型描述土单元循环应力应变关系中的非线性和滞回性,依据蠕变关系描述土单元的循环累积性。基于拟动力黏弹塑性本构模型,提出了一种分析静荷载与循环荷载共同作用下软土中张紧式吸力锚基础变形过程的拟动力黏弹塑性有限元方法。该方法并不详细追踪土单元的循环应力应变响应,而是将循环次数视为时间,通过等效黏弹性分析确定吸力锚基础的循环变形;根据土单元静应力和循环累积应变势,采用初应变法确定吸力锚基础的累积变形。结合循环变形和累积变形,确定吸力锚基础变形随时间的变化关系,即位移时程曲线。最后,将有限元计算结果与1g条件下吸力锚模型试验结果进行比较,结果显示两者基本一致。The suction anchor with taut mooring system is an important floating platform foundation in deep water. Large deformation of soil occurs under the combination of static and cyclic loadings, which impacts the stability of the suction anchor foundation severely. A pseudo-dynamic visco-elastic plastic constitutive model which describes the undrained cyclic stress-strain response of saturated soft clay is introduced. The model combines the equivalent visco-clastic theory with the creep theory, describing the nonlinearity and hysteresis of the cyclic stress-strain relationship through the equivalent visco-elastic model and the cyclic accumulative characteristic through the creep theory. Based on the pseudo-dynamic visco-elastic plastic constitutive model, a pseudo-dynamic visco-elastic plastic finite element method is developed for the assessment of the deformation process of the suction anchor foundation subjected to the combination of the static and cyclic loadings. The method does not track the cyclic stress-strain response, but treats the number of cycles as the time. The cyclic deformation of anchor foundation is determined by the equivalent visco-elastic calculation. The accumulative deformation is determined using the initial strain method on the basis of the static stress and cyclic accumulative strain potential. The relationship between the deformation and the time of anchor foundation that is the displacement-time history curve can be obtained according to the cyclic and accumulative deformations. The comparison between the calculated results by the finite element method and the anchor model test results under lg conditions shows that the both arc basically in agreement.

关 键 词：拟动力本构模型 吸力锚 模型试验 循环变形 循环累积变形 

分 类 号：TU411[建筑科学—岩土工程]