吸力式沉箱底部土体循环特性及其等效循环蠕变模型研究  

Study on cyclic characteristics and equivalent cyclic creep model of the soft clay at the bottom of suction caisson foundation

作　　者：朱文波[1,2] 戴国亮[1,2] 王博臣[1,2] 龚维明 孙捷[3] 胡皓 ZHU Wen-bo;DAI Guo-liang;WANG Bo-chen;GONG Wei-ming;SUN Jie;HU Hao(Key Laboratory of Concrete and Prestressed Concrete Structure of Ministry of Education,Southeast University,Nanjing,Jiangsu 211189,China;School of Civil Engineering,Southeast University,Nanjing,Jiangsu 211189,China;Huaneng International Power Jiangsu Energy Development Co.,Ltd.Clean Energy Branch,Nanjing,Jiangsu 210003,China)

机构地区：[1]东南大学混凝土及预应力混凝土结构教育重点实验室,江苏南京211189 [2]东南大学土木工程学院,江苏南京211189 [3]华能国际电力江苏能源开发有限公司清洁能源分公司,江苏南京210003

出　　处：《岩土力学》2022年第2期466-478,共13页Rock and Soil Mechanics

基　　金：国家自然科学基金(No.52078128,No.51878160,No.51678145);中国华能集团有限公司科技项目(No.HNKJ19-H17)。

摘　　要：吸力式沉箱基础作为张力腿平台(TLP)的锚固基础,其底部土体不仅存在轴向卸荷作用,而且还存在循环荷载作用。现有研究很少涉及在卸荷条件下进行的软黏土循环累积变形研究。因此,通过循环三轴试验研究了轴向卸荷条件下软黏土的应变累积变形及应变软化特性。试验结果表明:在低静偏应力以及动偏应力条件下,土体应变累积及软化程度较低;随着动偏应力增加,循环累积变形逐渐变大且前期发展较快后期趋于稳定,同时应变软化程度逐渐增大;土体循环累积变形随动偏应力提高而增大,其循环累积应变曲线呈衰减-稳定的蠕变特性。在试验基础上,提出与静偏应力和动偏应力有关的软化系数公式。构建了考虑软化系数与静偏应力、动偏应力等条件下软黏土等效循环蠕变模型。将该模型推广至三维,并开发了有限元子程序。建立了循环荷载作用下吸力式沉箱基础循环抗拔承载力有限元分析法,将其用于吸力式沉箱基础循环累积变形分析中,并与沉箱模型循环试验结果进行了对比验证。As the anchoring foundation of the tension leg platform(TLP), suction caisson foundation is not only subjected to the vertical pullout load but also subjected to the cyclic load. However, there are few studies on the mechanism of the cyclic characteristics of soft clay under unloading condition. In this study, the cyclic triaxial tests under axial unloading were carried out to obtain the cyclic cumulative deformation and strain softening characteristics of soft clay. The results show that the degree of strain accumulation and softening coefficient were low under the condition of low static deviator stress and dynamic deviator stress. With the increase of dynamic deviator stress, the cumulative cyclic deformation gradually increased and rapidly developed in the early stage and tended to be stable in the late stage. Meanwhile, the softening of soil gradually increased. The cyclic cumulative deformation of soil increased with the increase of dynamic deviator stress, and the cyclic cumulative strain curve showed attenuation-stability creeping characteristics. Based on the tests, a formula for softening coefficient related to static deviator stress and dynamic deviator stress was introduced to describe the test results of soft clay under different stress levels. Considering the influence of static deviator stress, dynamic deviator stress and softening coefficient, an equivalent cyclic creep model of soft clay was established. On this basis, a three-dimensional equivalent cyclic creep model was built, and a finite element subroutine was developed.The finite element method for cyclic uplift capacity of caisson was established to analyze the cyclic cumulative deformation of soil. It was verified by comparing with the test results.

关 键 词：吸力式沉箱基础 软黏土 应变软化 累积变形 等效循环蠕变模型 有限元 

分 类 号：TU411[建筑科学—岩土工程]