【作者】 梁通；

【导师】 金峰；

【作者基本信息】 清华大学 ， 水利工程， 2007， 硕士

【摘要】 水对坝体和坝基的作用力是进行坝体、地基的强度与稳定分析的重要荷载。而对坝区的水荷载要有一个较为清晰的认识,需要对坝区进行系统的渗流场分析。本文即是在分析坝区渗流场的基础上,基于更适用于岩石和混凝土的广义有效应力原理,建立了一套计算混凝土坝变形和应力的有限元分析方法。并结合二滩拱坝大量的工程资料和原型观测资料分析了二滩拱坝的渗流场和应力场。论文的主要工作和研究成果如下:一、从基本的渗流理论出发,借助有限单元法研究坝区渗流场问题。分析总结了渗流计算数值模拟中常遇的问题,如渗流自由面的确定方法,渗控措施的模拟方法等,并初步分析讨论了渗控措施对坝区渗流的影响。二、从宏观角度阐述饱和孔隙介质中水的基本力学效应,讨论了扬压力和渗透力的概念,着重回顾扬压力的发现、发展。在广义有效应力原理的基础上推导了扬压力和渗透力的表达式,并基于有限元格式得到了作用在重力坝建基面的水压力的表达式,阐述了重力坝坝底扬压力的真正物理含义及其主要影响因素。同时,讨论得出了计算时正确的水荷载组合,建立了一套更适于混凝土和岩石性质的计算方法。三、研究发现,水荷载的大小及施加方法与孔隙介质自身B值有关。B值对坝体应力和位移有着明显的影响。针对某典型重力坝算例发现,在B=0时水荷载作用下产生的应力状态对坝体最有利,而B=1.0时的应力状态对坝体最为不利。这是否具有普适性还需要进一步的研究。四、在分析整理二滩拱坝的地质资料与渗控措施情况的基础上,建立了精细有限元计算模型。分别对二滩拱坝的渗流和应力进行计算分析,渗压以及位移的计算结果与实测值吻合相对较好。对二滩拱坝渗控措施有限元分析研究表明,降低渗压主要以排水为主,防渗帷幕的作用不大。运用本文建立的计算应力的分析方法探讨了坝体的应力情况,结果表明,当B值增大时,坝体的拉应力变大,而压应力变小。这说明考虑渗流时,坝体的应力状态更为恶化。所以在工程设计中渗流的作用应给予足够的重视。更多还原

【Abstract】 During the strength and stability analysis of dam-foundation system, it is quite necessary to incorporate the action force by water on both the dam part and the foundation. Apparently, a seepage analysis of the whole system is required to obtain a more clear understanding of the water loads. A numerical approach by the finite element method is established in this thesis for calculation of internal deformation and stress field within the dam part, on the basis of a seepage analysis and the generalized effective stress law which is found to be more appropriate for rock and concrete materials. Moreover, a 3-D seepage and stress analysis of Ertan arch dam has been completed with some engineering data and field records as a basis. Main work and contributions of this thesis are presented as below:(1) Based on the fundamentals of seepage theory, some seepage analyses of the dam part have been conducted using the finite element method. Some typical problems during numerical modeling of seepage process are analyzed, such as methods for determination of the phreatic surface and techniques in simulating the seepage control measures. Some preliminary investigation into the effect of control measures on the water redistribution within the dam part is also presented.(2) The mechanical effects of water in saturated pore medium is represented from macroscopic view and concepts of uplift pressure and seepage force are discussed. And, the historical review of the development of uplift is revealed especially. Based on generalized effective stress law, the expression of uplift pressure and seepage force has been deduced and expression of water pressure on gravity dam base in FEM format also obtained; the real physical meaning and influencing factors of uplift pressure of gravity dam is represented; Simultaneously, the correct water-load combination forms is given, and a numerical method more suitable for rock and concrete materials is established.(3) It has been found that the magnitude and application method of water load are related to B value of the pore medium itself, and the choice of B value presents a notable effect on dam displacement and stress. Taking a gravity dam as an example, it is observed that most favorable stress distribution within the dam part is given when B=0, while contrarily a most dangerous stress field is mobilized when B=1. However,it still requires further study to make sure whether the phenomenon is universal.(4) A refined FEM modal is established based on analysis of the geological data and the complicated seepage prevention and drainage measures of ertan arch dam. Seepage and stress of the dam area have been performed sequentially, and the simulated pore pressure and displacement agree well with the monitoring data. It is indicated by the simulation results that the drainage system is comparatively more effective to reduce the pore water pressure than the cutoff wall measure. It is shown by the simulation results that larger tensile stress would be triggered while the compression stress is lowered within the dam part when the B value is increased, which indicates more dangerous stress distribution for the dam part when considering the seepage flow. Therefore, it is of great importance to appropriately consider the seepage behavior during the design of water dams.更多还原