DDA數值模擬級配的顆粒集合體

Abstract

由經驗得知當砂土中含有細顆粒時，其工程性質與均勻級配之砂土有很大 不同。在相等的相對密度下，均勻級配的砂土可能是膨脹性 (dilatant) ，如有細顆粒則可變成收縮性(contractive)。細顆粒對現場土壤試驗， 比如錐貫入試驗也有很大的影響。數值模擬顯示砂土中之細小的顆粒在受 圓錐貫入試驗的影響下所受的應力(stress)要比大顆粒高。我們對於細顆 粒如何影響砂土之工程性質所知有限。為了進一步了解細小顆粒對砂土性 質之影響，我們展開一系列的研究，包括用不連續變形法之數值模擬與實 驗室中之砂土實驗。本研究主要的目的是安裝並修改不連續變形分析方 法(DDA)程式來模擬級配的顆粒集合體。用來產生具有兩種尺寸之顆粒集 合體的程式已發展完成。為用DDA做顆粒集合體之模擬及結果的展示之程 式也已完成。本論文詳細的敘述這些數值方法發展的細節。 Experience has indicated that the engineering properties of a graded sand with fines are significantly different from those of a uniform sand. Under a given relative density , a uniform sand could be dilatant while a graded sand with fines could be contractive. Fines can influence the results of in-situ tests such as the cone penetration tests. Numerical simulations , show that finer particles tend to experience higher stress induced by the penetration of a cone. There is a lack of fundamental understanding as to how the fines affect the behavior of a granular material. A series of research activities were initiated to enhance our understanding related to the effects of fines on the behavior of sands. These activities include numerical simulations using Discontinuous Deformation Analysis (DDA) method ,and laboratory experiments on sands. The main objective of this research is to implement DDA, and to make necessary modifications so that the programs can be used to simulate a graded sand deposit as a particulate assembly. Numerical schemes to create assemblies consist of particulates with two different sizes have been developed. Modifications of DDA program have been implemented to facilitate the numerical simulations of particulate assemblies and to present the results. The thesis describes details of the numerical developments.