强夯碎石桩的发展及成桩机理分析

Development of DRM and Analysis of Column Formation Mechanism

强夯置换法是８０ 年代才开始应用的软土地基处理方法，在我国已成功应用于多个工程．介绍强夯置换法的发展概况，用波动理论定性阐述强夯置换法在成桩过程中桩土界面的变化，说明了夯击能量从第一击接近球状传播到形成柱状桩体后的接近一维传播变化过程；探讨了夯锤势能转换成使桩体向下延伸的动能、桩体压密的势能、通过桩体侧面和底面向桩外传播的动能比例．分析结果表明：强夯置换法特别适用于抗剪强度极低的饱和软粘土地基，置换深度一般不超过８ ｍ ；用强夯法将粗颗粒料（ 如碎石） 夯击到土层中能够形成柱状体；复合地基不仅置换部分强度大幅度提高，天然土部分由于排水固结作用和挤密作用也使强度有所提高．

Dynamic Replacement Method (DRM) is a foundation treatment method which began to be used in engineering in 1980's.The method has been successfully used in many engineering projects in our country.In the paper,the history of development is introduced first.Then the process of exchange of the surfaces of column and soil is discussed on the basis of the theory of wave transmission.The process of energy transmission from the spherical surface at the first hammering to one dimension at the shaping of the column.The ratio of the kinetic energy to the potential energy which densifies the column,and the ratio of the wave energy spreading from the side surface and the bottom surface of the column are discussed.The conclusion is that DRM especially suits the treatment of very soft foundations in which shear strength is very low.The depth of the column is usually less than 8m.The column of large size material (e.g.crushed stone) can be shaped by DRM.The strength of compound foundations can be improved not only the partial of the column but also the natural soil owing to the effect of consolidation and densification.