| Summary: | 碩士 === 中華大學 === 土木工程學系碩士班 === 88 === There’re lots of traffic construction situated at the Toukoshan Formation in the north part and middle part of the western Taiwan. To take the retaining wall of highway for example, the backfill material are mostly from the extremely weak sandstone and shale of that stratum, after ponder on economical problem and environment protection. For this reason, to understand and to master the property and other connected information of the reconsititutive material that mix of the sandstone and shale from this stratum is the emphasis of this article.
In this study, we take the extremely weak sandstone and shale from the Toukoshan Formation in Hsinchu as the materials. In the condition of the optimum moisture water content, we make six samples after reconstituting and compacting the materials. We proceed a series of triaxial test including hydrostatic compression tests, isotropical consolidated axial compression drained tests and unloading-reloading test. In these experiments, the clay content and the initial cell pressure will be concerned and the result will be used in the study for the triaxial mechanics of the reconstitute materials. The next step, we integrate the finite element program and the Nova model which can simulate the strain harding and the volumetric dilation, we can simulate the stress-strain relation of the reconstitutive material. At last, we use the reconstitutive material as the backfill material in a case of a fictitious embankment to simulate and analyze.
First, from the HC test we know that as the content of clay increase, the volumetric strain of the reconstitutive material will increase and the bulk modulus will reduce; and also the bulk modulus is in proportion to the cell pressure. And then, in the CID test, as the content of clay increase, the cohesion will increase (between 0.31~0.15 kgf/cm2); but on the other hand, the effective friction angle will reduce (between the degrees of 28.75 ~35). Moreover, the ultimate deviator stress, secant elastic modulus and initial tangent elastic modulus will reduce as the content of clay increase and will raise as the cell pressure increase.
About the numerical simulation for the triaxial test, first of all, we will proceed the parametric studies for the 8 parameters (Lo、Bo、L、M、m、、D and Pco ) of Nova model and verify the simulation. And then, according the result from HC and CID test, we make the simulation and analysis. From the whole, according the qualitative analysis and quantity analysis, Nova model can get rational prediction. And also master volumetric dilation for reconstitutive material of low clay content. Consider the case of a fictitious embankment, when lateral stress ratio increase to two or increased or clay content decrease to fifty percentage, vertical displacement of embankment will reduce obviously.
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