为了研究相邻基础对地基刚度的影响，提出了地基刚度影响系数的概念，并运用三维弹性半空间内明德林解，推导出地基刚度影响系数的计算表达式，进而通过计算地基刚度影响系数分析了相邻基础存在时，两个基础之间净距、基础边长比值以及地基土特性对地基刚度的影响规律，并根据净距和边长比值划分了可不考虑相邻基础相互作用的范围。结果表明：（1）基础周围有相邻基础存在时，其地基刚度较不存在相邻基础的地基刚度有所提高；（2）相邻基础对地基刚度的影响随着两个基础之间净距的增加而减弱，随着边长比值的增加而增强，以及随着地基土泊松比的增加而增强；（3）黏土地基中相邻基础对地基刚度的影响较其他（如粉土地基）地基更显著；（4）当净距不小于基础边长15倍时，或者基础边长比值小于0.1时，可以不考虑相邻基础对地基刚度的影响，其他情况需根据净距和边长比值分析是否考虑相邻基础对地基刚度的影响。

To analyze the influence of an adjacent foundation on ground stiffness, a new concept of ground stiffness influence coefficient is introduced, which is defined as the ratio of the ground stiffness with the adjacent foundation to that without. Based on the Mindlin solution, an analytical expression of the influence coefficient is derived from a system of two rigid, surface, rectangular foundations under three-dimensional elastic half space. Through calculating the influence coefficient, we analyze the influences of clear distance, side-length ratio of foundations and Poisson’s ratio of the ground soil on ground stiffness when the adjacent foundation exists. It is shown that: (1) The ground stiffness can be improved when the effect of the adjacent foundation is taken into account. (2) The influence of the adjacent foundation on ground stiffness shows a positive correlation with the side-length ratio and the Poisson’s ratio, and a negative correlation with the clear distance. (3) The influence is more significant in clay ground than in other kinds of ground, such as silt ground. (4) It is not necessary to consider the influence of adjacent foundation when the clear distance is larger than 15 times the side length of the foundation or the side-length ratio is less than 0.1. In other cases, however, we should decide whether or not it is necessary to consider the influence of both the clear distance and the side-length ratio.