在前人复合地基研究的基础上，进一步明确了复合地基的基本概念、分类及其基本特点，并提出了CM三维复合地基的原理、形式以及工作机理，用柔性短桩处理浅层软弱土、刚性长桩控制沉降、褥垫层调整和改善桩土应力分担比。给出了CM三维复合地基承载力和沉降的设计计算思路。

On basis of the results of the previous researches on composite foundations, the authors present the basic concepts, types and features of composite foundations. The authors also present the principles, forms and mechanisms of CM threedimension composite foundations. In composite foundations, Mpiles are used to strengthen the soft subsoil, Cpiles are used to control the settlement and cushions are used to modify and improve the shares of the stress taken by the piles and subsoil. The authors also provide the design and calculation procedures for the bearing capacity and settlement of CM threedimension composite foundations.