دانلود رایگان مقاله انگلیسی خواص مکانیکی و معادلات ساختاری ملات خرده لاستیک - الزویر 2018

abstract

There will be a lot of pollution in the process of production and degradation of rubber. It is imperative to recycle rubber in order to build a green and saving environment. A new kind of mortar with rubber particles is an effective way to reuse the used rubber products. The crumb rubber mortar effectively resist external stress through its own deformation. Therefore, it is of practical significance to study the strength behavior of crumb rubber mortar. The stress-strain curves of crumb rubber mortars with 5 different rubber contents under a triaxial stress condition are obtained through laboratory testing. The internal variation law of the elastic modulus, Poisson’s ratio and damage variable are analyzed, and the necessity of incorporating the influence of the damage threshold into the damage evolution model is discussed. According to a rock damage model based on Lemaitre’s strain equivalence theory and the introduction of the damage threshold based on the traditional Weibull random distribution, the damage constitutive model of crumb rubber mortars under the influence of the damage threshold is established by considering two factors. The method of determining the model parameters is presented. The model can describe the entire process of strain softening and deformation of crumb rubber mortars for various levels of rubber content or confining pressure. The model can also fully reflect the linear elastic deformation characteristics of rock under small deformations and the nonlinear mechanical behavior after the peak strength is exceeded. The model is particularly suitable for describing the complex stress states in the field of underground engineering, and it provides a reference for the design of supporting structures. Finally, by comparing the measured results of three-axis compression tests of crumb rubber mortars with various rubber contents, the rationality of the model is verified.

5. Conclusions

In this study, crumb rubber mortars with different rubber particle contents are prepared, and physical and mechanical experiments are conducted. Based on the Lemaitre equivalent strain theory of rock damage, by incorporating the influence of the damage threshold of crumb rubber mortars, the damage evolution model of crumb rubber mortars and the damage constitutive model of crumb rubber mortars are discussed for the entire process of simulating the strain softening deformation. The following conclusions can be drawn.

(1) The stress-strain curves of crumb rubber mortars obtained from experiments show that the peak strength of the rubber particles decreases as the rubber particle content increases. After the peak strength is reached, the strain softening property decreases gradually, and the elastic modulus decreases exponentially. The Poisson’s ratio shows dynamic variation. Before the peak strain, this parameter increases linearly. After the peak strain, it increases logarithmically.

(2) A damage constitutive model of crumb rubber mortars considering the effect of damage threshold is established that can accurately describe the stress-strain relationship of crumb rubber mortars with various rubber contents under triaxial compression state. Relative to the experimental results, the model in this paper can accurately describe the entire process of the strain softening deformation of crumb rubber mortars under a complex stress state.

(3) The range of the value of damage threshold, k, is discussed. The damage threshold, k, of CRC is generally between 0.1 and 0.9. The lower the rubber particle content, the lower the confining pressure and the greater the damage threshold. When the confining pressure increases from 0 MPa to 5 MPa, the damage threshold decreases sharply. When the confining pressure increases from 5 MPa to 10 MPa, the damage threshold exhibits a smaller variation relative to the former response, indicating that the damage threshold is more sensitive in the initial stage of the confining pressure.