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Experimental Research on Mechanics and Constitutive Model of Artificially Cemented Sand

Author: ZhaoCan
Tutor: ZhuangXinShan;WangXuMin
School: Hubei University of Technology
Course: Geotechnical Engineering
Keywords: artificially cemented sand calcium oxide curing time mechanics chemicalindex constitutive model
CLC: TU41
Type: Master's thesis
Year: 2013
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Abstract


The cementation character of nature soil is not reversible. Once the cementationhas been damaged during sampling or sample preparation process, it will be difficult torecovery. When experimental research on mechanics of nature cemented soil in lab, themethod of artificial preparation soil sample is general used. Artificial cement sand is ahighly compacted mixture of sand, cementitious materials and water. The strength andengineering properties of cemented sand are improved with the generation of hydrate.The research of artificial cement sand not only can forecast the stress-strain laws of thenature sand ground base, but also has important significance for the research onmechanical properties of the artificial ground reinforced soil.For research the influence of chemical index on the mechanical properties ofartificially cemented sand, high purity quartz sand and calcium oxide AR, which havelittle chemical admixture, were used to prepare samples in this thesis. In order to speedup the carbonation reaction, samples were maintained in a humid room which full of dryice. In this thesis, a series of mechanical experiments in lab and calcium carbonatequantitative chemical tests have been carried out and the study of experimental resultshas been performed.The main research contents and achievements can be summarized as following:(1) Unconfined compressive strength tests are conducted on artificially cementedsand which has different cement ratio and curing time. The effects of cement ratio,curing time and void ratio on unconfined compressive strength have beencomprehensively analyzed and summarized. It is established the compressive strengthequation based on the variables of cement ratio, void ratio and curing time.(2) Consolidated drained triaxial tests are conducted on artificially cemented sandsamples, which have different cement ratio, confining pressure and have the samecuring time, and pure sand samples. On the basis of the comparative analysis ofstress-strain and stress-volumetric strain cures, the influence laws of cement ratio onshear strength index have been investigated.(3) Calcium carbonate quantitative chemical tests have been conducted onartificially cemented sand after triaxial tests. According to the test results, calciumcarbonate and calcium hydroxide content can be calculated. The calcium oxideconversion rate and chemical index were established. Through the analysis the inferenceof the calcium oxide conversion rate and chemical index on mechanical properties, therelationship of shear strength parameter and chemical index was established to modifyMohr-Coulomb strength theory.(4) The Duncan-Chang E-K model has been applied and the parameters of E-Kmodel have been determined.Based on the piecewise fitting method and modifiedMohr-Coulomb strength theory, the improved model has been established to improvethe ability of Duncan-Chang model. The improved model has take into account the problem of strain softening. The calculation curves of improve model and Duncan-Chang model have been drew. Through contrast of calculation curves based on the twomodels and test cures, the superiority of the improved model is verified.

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CLC: > Industrial Technology > Building Science > Soil mechanics,foundation engineering > Soil Test
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