| Plastic concrete has the characteristics of low elasticity,low strength and good anti-seepage performance.At the same time,it can adapt to the deformation of the foundation and can be combined with the foundation.However,most of the researches on plastic concrete at present focus on uniaxial mechanical properties and impermeability,and are limited by testing instru-menlts and methods,so there is little research on its dynamic mechanical properties.However,deepening the research on the triaxial mechanical properties of plastic concrete has certain effects on improving the safety of plastic concrete structures,and can also save construction costs.Therefore,it is necessary to simulate the stress state of plastic concrete in practical engineering application,that is carrying out triaxial loading tests of plastic concrete and to study the effects of different loading rates and different confining pressures on the dynamic performance of plastic concrete.First of all,following the design principle of the assumed bulk density method of concrete,the mixture ratio used in the test is determined through repeated tests.Then,through testing slump and diffusivity,the prepared plastic concrete is ensured to have good working performance.Through the study of stress-strain characteristics of plastic concrete,the influence law of mix proportion parameters on its compressive strength and stress-strain characteristics is revealed.Through dynamic model test,the influence law of mix proportion parameters on dynamic model of plastic concrete is analyzed.Finally,the dynamic strength,peak strain and stress-strain char-acteristics of plastic concrete under different loading rates and different confining pressures are studied by using a large-scale coarse-grained soil dynamic and static triaxial tester.The results show that:(1)The dynamic modulus first decreases and then increases with the increase of sand ratio.The increase of water-binder ratio and bentonite content will lead to the decrease of dynamic modulus.(2)When the confining pressure is 0.4MPa,the strength and peak strain of plastic concrete with strength less than 5.OMPa are more sensitive to small loading rate;For plastic concrete with strength above 6.0MPa,its strength is more sensitive to large loading rate,and the loading rate has basically the same effect on peak strain in the range of 400 n/s-1200 n/s.The slope of the stress-strain curve also increases slightly with the increase of the loading rate,and the descending section of the curve decreases more with the increase of the loading rate,i.e.the damage is more rapid.(3)There is a positive correlation between the dynamic strength of plastic concrete and confining pressure.The influence of confining pressure on the dynamic strength is more obvious than that of loading rate.At the same mixture ratio,the relative strength growth rate ? ?a/0.4 of plastic concrete shows a decreasing trend with the increasing confining pressure,and the de-creasing range decreases with the increasing confining pressure.Under the same confining pressure,the relative strength growth rate of high strength plastic concrete will decrease with the increase of uniaxial compressive strength.Whether the mix proportion is the same or not,the peak strain increases with the increase of confining pressure,but when the mix proportion is different,the increase of peak strain decreases with the decrease of water-binder ratio.In this paper,the dynamic strength and stress-strain characteristics of plastic concrete are studied by means of tests.The stress state during the tests is consistent with the stress state of plastic concrete in practical engineering,which has certain reference significance for the appli-cation of plastic concrete in practical engineering. |
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