Elastic modulus evolution of rocks under heating\u2013cooling cycles

Weidong Liu,Liangchi Zhang,Ning Luo

doi:10.1038/s41598-020-70920-3

Weidong Liu, Liangchi Zhang + Show 1 more

Open Access

https://doi.org/10.1038/s41598-020-70920-3

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Abstract

Rocks decay significantly during or after heating–cooling cycles, which can in turn lead to hazards such as landslide and stone building collapse. Nevertheless, the deterioration mechanisms are unclear. This paper presents a simple and reliable method to explore the mechanical property evolutions of representative sandstones during heating–cooling cycles. It was found that rock decay takes place in both heating and cooling processes, and dramatic modulus changes occurred near the α − β phase transition temperature of quartz. Our analysis also revealed that the rock decay is mainly attributed to the internal cracking. The underlying mechanism is the heterogeneous thermal deformation of mineral grains and the α – β phase transition of quartz.

Highlights

Rocks decay significantly during or after heating–cooling cycles, which can in turn lead to hazards such as landslide and stone building collapse
The mechanical properties of rocks are significantly affected by heating–cooling cycles 1–7, which in turn can dramatically increase the risk of landslide8, rockfall[2] and stone building c ollapse[9] during or after fire-related accidents
It was found that when the heat treatment temperature Tht is below 250 °C, the physical and mechanical property changes are very s mall[4,5,6,15,16,17,18]

Summary

Introduction

Rocks decay significantly during or after heating–cooling cycles, which can in turn lead to hazards such as landslide and stone building collapse. It was suggested that the α − β phase transformation of quartz would have contributed to the deterioration of quartz-rich rocks[20,21] In these studies, most of the property and structure characterizations were conducted either before or after a heat treatment. Quantitative characterization of the deterioration process and the effects of thermal expansion/shrinkage and the α – β transition of quartz are not available It is unclear how an individual factor influences the mechanical properties of a rock—the key knowledge-base for developing fire rescue schemes and for establishing reliable criteria of post-fire hazard assessment. This paper aims to reveal the decay mechanisms of representative sandstones during cyclic heating–cooling treatments To this end, the Young’s modulus evolutions of the sandstones with temperature will be characterized with the aid of the HTIET (see Fig. 1). The underlying deterioration mechanisms will be revealed via a mean-field model linking the modulus evolution with the crack density change in rocks

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