Abstract: Aiming at the reduction of the under groundwater buoyancy of underground structure,a theoretical basis was established.Firstly, two kinds of visualized soil accumulation models were proposed,which represented the real sand and clay respectively. Next,the similarities and differences of the two models were compared and it was pointed out that they had the characteristics of interconnection between pores. Then,in view of the statics concept and method, the accumulation model of contact flange soil abstracted from visual-particle accumulation models of soil was obtained, and the interaction between the size of groundwater buoyancy and the contact between soil particles was analyzed.The research results show that a new concept of soil mechanics can be established, that is contact-area ratio of solid particles, which represents the contact relationship between solid particles in soil layer. It is further concluded that there is always a reduction in the buoyancy of the groundwater water of the underground structure, and the reduction coefficient is directly proportional to the contact-area ratio of the solid soil particles. Besides,the buoyancy of underground structure under the condition of multi-soil foundation was analyzed. The results show that the water buoyancy of underground structures may be affected by the soil layers in a certain depth range of the basement,and the specific theoretical algorithm is given.

Key words: geotechnical engineering, pore, reduction of groundwater buoyancy, accumulation model, contact-area ratio of solid particle

摘要： 针对地下结构所受地下水浮力的折减建立一种理论依据。提出了两种形象化的土粒堆积模型，以分别代表现实中的砂土、黏土；对比两种模型的同异情况，指出它们均具有孔隙间相互连通的特性；从静力学角度，借助土粒堆积模型及进一步抽象得出的接触凸缘土粒堆积模型(力学模型)；分析了地下水浮力大小与土粒间接触关系的相互影响。研究结果表明：可建立一种新的土力学概念—固体土粒接触面积比，以表征土层中固体土粒之间的接触关系，进而得出了地下结构基底水浮力总存在折减，且折减系数与固体土粒接触面积比成正比的结论。并进一步分析了多土层地基情况下地下结构所受水浮力，结果表明：基底一定深度范围内土层均可能影响地下结构所受水浮力，并给出了具体理论算法。

关键词: 岩土工程, 孔隙, 地下水浮力折减, 堆积模型, 固体土粒接触面积比