Softening Damage Analysis of Gypsum Rock With Water Immersion Time Based on Laboratory Experiment

Chun Zhu,Yun Lin,Xue Liu,Feng Xiong,Xiaoding Xu,Wanrong Liu,Chen Cao

doi:10.1109/access.2019.2939013

Abstract

In view of the effect of water on the physical and mechanical parameters of natural gypsum rock, in this study, gypsum rock in the goaf of a gypsum mine was selected as the research object, and gypsum rock samples were prepared with different immersion times. In addition, uniaxially tests were performed separately on the gypsum rock samples. Compression and scanning electron microscopy experiments were carried out to analyze the effects of immersion time on the uniaxial compressive strength, elastic modulus, Poisson’s ratio, and microstructure of gypsum. The results show that the uniaxial compressive strength and elastic modulus of gypsum are inversely proportional to the water content. However, the Poisson’s ratio is direly proportional to the water content, and the failure mode is destroyed by the brittle fracture of a single crack and is transformed into the shear ductile failure of the Y-shaped crack. Microscopically, with increasing immersion time, the bonds in the crystal of the microporous cracks and microcrack tips are weakened by hydrolysis, and the macroscopic structure is complicated by the internal structure of gypsum, and the end of the crack is expanded by the compressive action of water. Based on the damage mechanics, the evolution equation of gypsum soaking softening damage based on time factor was derived. The relationship between the brittleness coefficient and softening damage variable is revealed, providing a theoretical basis for the determination of the softening degree of gypsum in the goaf.

Highlights

With the advancement of urbanization, the construction and the decoration industry have developed rapidly, providing a broad space for the development of the gypsum industry, leading to continuous expansion of the market demand
The fitting equation of the water content and water immersion time is shown by Eq (2) with the correlation coefficient R2 = 0.8499
Through the experimental study on softening damage of gypsum rock caused by immersion time, some conclusions are drawn as follows: (1) The water absorption rate in the initial stage of gypsum immersion is high and gradually decreases with increasing immersion time; the uniaxial compressive strength and elastic modulus of gypsum are negatively correlated with the water content, and the uniaxial compressive strength and elastic modulus decrease with increasing water content; Poisson’s ratio of gypsum rock increases with immersion time; the failure characteristics of natural gypsum rock under uniaxial compression are mainly splitting and tensile failure

Summary

INTRODUCTION

With the advancement of urbanization, the construction and the decoration industry have developed rapidly, providing a broad space for the development of the gypsum industry, leading to continuous expansion of the market demand. C. Zhu et al.: Softening Damage Analysis of Gypsum Rock With Water Immersion Time Based on Laboratory Experiment weakening of rock. Zhu et al.: Softening Damage Analysis of Gypsum Rock With Water Immersion Time Based on Laboratory Experiment weakening of rock For soft rock such as mudstone and coal rock, the water content affects rock compression. Hongpu [7] examined the evolution equation of the rock water damage variable, indicating that the water content has a linear relationship with the elastic modulus and uniaxial compressive strength and is the main factor affecting rock expansion. The brittleness coefficient is used to visually judge the softening degree of the test piece and can be applied to the determination of the softening range and softening degree of the surrounding rock passing through the gypsum layer tunnel It can effectively remedy the vacancy of current research

SAMPLE PREPARATION AND INSTRUMENTATION

SEM ANALYSIS OF GYPSUM ROCK

GYPSUM ROCK SOFTENING DAMAGE AND BRITTLENESS COEFFICIENT

CONCLUSION