【作者】 蒋敏敏；

【导师】 蔡正银；

【作者基本信息】 南京水利科学研究院 ， 岩土工程， 2010， 博士

【摘要】 随着深水防波堤的大规模兴建,对于波浪-防波堤-地基相互作用问题的研究显得越来越重要。箱筒型基础防波堤是一种适用于深水、大波浪荷载和软弱地基等条件的新型防波堤。它与离岸工程中常用的重力式结构和板桩结构等的工作机理有较大的区别,不仅依靠结构基础的挡土作用维持稳定性,还依靠复杂的土与机构相互作用来维持稳定。本文以天津港新型的箱筒型基础防波堤为背景,通过土工离心模拟技术、土体静动三轴试验和有限元数值模拟等手段对波浪荷载作用下复杂防波堤结构与软土地基相互作用的问题进行了研究,主要工作包括如下几个方面:(1)在离心试验中,通过对防波堤施加静荷载以初步模拟波浪荷载的作用,研究在模拟波浪的静荷载作用下新型箱筒型基础防波堤与地基相互作用的问题,探讨防波堤的静力位移特性、稳定性和地基中孔压发展,以及地基土体强度对其影响。(2)通过研制在离心机中施加非接触式周期性循环荷载的加载设备,实现在离心试验中对防波堤结构施加周期性循环荷载,以模拟波浪荷载的作用,研究在循环荷载作用下箱筒型基础防波堤与地基相互作用的问题,探讨在循环荷载作用下的动态位移、动态孔压响应、防波堤位移模式以及循环荷载的作用对箱筒型结构周围地基土体强度的影响等问题。(3)利用循环三轴试验研究波浪荷载作用下软土的动力性质,通过对土样施加循环荷载的作用,探讨累积轴向应变、平均孔压、弱化指数的发展规律,分析循环荷载后各物理量的关系以及循环周期对各物理量的影响。(4)通过循环荷载后静三轴试验研究波浪循环荷载对土体静力性质的影响,分析循环荷载的作用对土体有效应力路径、孔压的影响,以及循环荷载后静模量的弱化性质,并探讨了循环荷载对不排水静强度的影响。(5)利用ABAQUS有限元软件模拟箱筒型基础防波堤与地基的相互作用问题,分析了不同基础筒高度、压重下,箱筒型基础防波堤与地基土体在静荷载作用下的应力应变、位移和土压力等的变化。更多还原

【Abstract】 With the construction of breakwater into deep water area, the researches on interaction of wave-breakwater-foundation become more and more important. Bucket foundation breakwater is a new type of breakwater that is suitable for deep water area, large wave load and soft ground foundation conditions. The working mechanism of bucket foundation structure is different from common offshore structures such as gravity structure and sheet-pile structure, and the stability of this new structure is not only depend on earth pressure on foundation wall but also intensely depend on interaction between soil and structure. Taking the project of bucket foundation breakwater in Tianjin port as a background, the topic of interaction between complicated breakwater structure and soft ground foundation under wave load is studied through geotechnical centrifuge modeling technique, static and cyclic triaxial test and FEM simulation method in this dissertation, the main works carried out are as follow:(1) A static load which simulates the wave load is applied on breakwater in centrifuge test, and interaction between breakwater structure and soft ground foundation is studied, the displacement, stability of breakwater and pore pressure developed in foundation under static load are discussed, and undrained strength of foundation soil on work mechanism of the breakwater are also studied.(2) A new equipment which can apply non-contact cyclic load on structure in centrifuge test is developed, by using this equipment the interaction between breakwater structure and soft ground foundation under wave load is simulated, cyclic displacement, cyclic pore pressure response, displacement mode under different working conditions are analised, and the effect of wave load on undrained strength of foundation soil that adjacent to the breakwater is studied.(3) The effect of cyclic wave load on dynamic properties of soft clay is studied with cyclic triaxial test, a low frequency cyclic load is applied on the specimen, the effect of cyclic stress amplitude, consolidated stress and period on cyclic strain, cyclic pore pressure response and modulus degradation are studied. The development of accumulative axial strain, average pore pressure and degradation index are studied, the relationship between these index after cyclic load and influence of period on them are also discussed.(4) The effect of wave load on static behavior of soft clay is studied with post-cyclic static triaxial test, the influence of cyclic load on static effective stress path and pore pressure development are studied, static modulus degradation and influence of cyclic load on undrained strength are also discussed.(5) The interaction between breakwater and soft ground foundation is simulated through the ABAQUS finite element software, stress strain, displacement in foundation and earth pressure on foundation bucket are analyzed under different foundation height and overburden pressure conditions.更多还原