DYNAMIC CHARACTERISTICS AND CONCEPT EXPRESSION OF SOIL STRUCTURE

With the development and construction of national major projects,a large number of foundation projects emerged as the times require. Some structures are particularly sensitive to the deformation of foundation soil,which requires special research to ensure the safety of related projects. However,the differences of the natural structure and consolidation state of soil can not only present an important impact on the compression characteristics and relevant mechanical indicators of soil,but also bring challenges to the analysis of deformation and settlement calculation. It would be of certain practical significance for engineering practice to clarify the combined manifestation of soil structure and consolidation state,and to discuss the dialectical relationship between them. Based on the previous studies of research group,as well as the confined compression characteristics of soil,this paper analyzes the mechanism of the abnormal 'over-consolidation' characteristics of soil,discusses the dynamic changes of the structure,and attemptes to give the concept pattern of soil structure. The following preliminary understandings are presented:(1)The essence of soil structure includes particle arrangement and structural connection. The compactness of particle arrangement reflects the spatial distribution of solid components,which is considered as the combined embodiment of multiple forces including consolidation pressure. The structural connection refers to the sum of the interaction forces between soil particles,which is characterized as the structural strength to resist deformation during confined compression. Generally speaking,all soils including undisturbed soil and remolded soil have different degrees of structure. (2)There is a dynamic coupling relationship between particle arrangement and structural connection of soil. The ′over-consolidation' property of soil,inconsistent with the stress history,results from the differential ′strengthening' derived by structural connection to soil skeleton. In addition,the compaction of soil derived by other forces except self-weight also plays an important role. (3)The concept expression of structural yield pressure σ_k,considering additional arrangement effect ΔP_a,is proposed,i. e. σ_k=P_c+ΔP_a+q. P_c and ΔP_a jointly reflect the particle arrangement characteristics,and q represents the structural strength. The related results may provide some reference for the evaluation and analysis of soil mechanical properties.