Experimental Study on Temperature Change and Crack Expansion of High Temperature Granite under Different Cooling Shock Treatments

Abstract

It is valuable to observe the influence of different cooling methods on the exploitation of geothermal energy and breaking hard rocks in deep geo-engineering. In this work, the effects of different cooling shock treatments on high temperature granite are discussed. First, perforated 100-mm-side cubic biotite adamellite samples were heated to four targeted temperatures (150 °C, 350 °C, 550 °C, and 750 °C). Then, anti-freeze solutions were compounded to produce the different cooling shock effects (20 °C, 0 °C, and −30 °C) by adjusting the calcium chloride solution concentration, and these anti-freeze solutions were injected rapidly into the holes to reflect the rapid cooling shock of high-temperature granite. Finally, the temperature variations and crack expansions of high-temperature granite under different cooling shock treatments were analyzed and the cooling shock cracking mechanism is discussed briefly. The main results can be summarized as: (1) The high temperature granite exposed to the cooling shock exhibited a "rapid cooling + rapid heating" change during the first 5 min. Due to the cooling shock, the total temperature was significantly lower than the natural cooling until 120 min later. (2) Below 350 °C, the macrocracking effect was not significant, and the sample reflected a certain range of uniform microcracks around the injection hole, while the macrocracks tended to be obvious above 550 °C. Moreover, as the refrigerant temperature decreased, the local distribution characteristics of the macrocracking became more obvious. (3) Based on the analysis of the dynamic heat balance, the undulation and width of the cracks around the heat balance zone were stable, but the numbers and widths of cracks near the hole wall and the side of the sample were visibly increased. This study extends our understanding of the influence of cooling shock on granite cracking.

Investigation of the effects of two different cooling treatments on the physico-mechanical and microstructural properties of granite after high temperatures

“…They found that cooling with water can reduce the mechanical properties of granite samples. Shen et al (2019) observed the influence of different cooling methods on granite after heat treatment. Their study showed that the effect of rapid cooling is much greater than the effect caused by slow cooling of heated granite.…”

Petrographic and petrophysical characterisation and structural function of the heritage stones in Fuwairit Archaeological Site (NE Qatar): implications for heritage conservation

“…High values of α, together with high temperatures that reach the surface stones of the hamada and the cooling due to rain will produce a rapid surface contraction that causes the fragmentation of the Umm Bab Member. Texture, grain size and thermal dilatation of stones are the main factors that determine the rate of thermal decay due to, among other causes, physical-chemical processes that act to break bonds at cracks tips (Rong et al, 2018;Al-Omari et al, 2019;Jin et al, 2019;Peng et al, 2019;Shen et al, 2019). Cracking proceeds even when only extremely low stresses are applied to the stone (akin to very small pulling forces).…”

Impact of cooling rate on mechanical properties and failure mechanism of sandstone under thermal–mechanical coupling effect

“…Zhang et al (2019) mainly studied the influence of temperature and prefabricated cracks on the failure mode of granite, and explained the formation mechanism of different failure modes of granite under the combined action of temperature effect and cracks. Shen et al (2019) prepared antifreeze by adjusting the concentration of calcium chloride solution, and conducted cooling shock (20 °C, 0 °C and − 30 °C) on granite samples with target temperatures of 150, 350, 550 and 750 °C. The results showed that with the decrease of refrigerant temperature, the local distribution characteristics of granite macro cracking became more obvious.…”