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.
Highlights
The majority of human energy demands depend on the supply of fossil fuels
Under the cold impact of different and granites into different temperature gradients, on the one hand, we studied the temperature temperature wetostudied in detail the temperature changes andand cracking effects of granite changegradients, of granite due the cooling shock of different temperature gradients, on the other hand, at different temperatures
The granite was first heated to different temperatures, and the calcium chloride solution was cooled to a different temperature
Summary
The majority of human energy demands depend on the supply of fossil fuels. The use of carbon-based fuels for power generation affects the atmosphere and global climate [1,2]. There is increasing enthusiasm for finding new renewable energy sources to replace fossil fuels, thereby reducing dependence on fossil fuels and reducing or eliminating greenhouse gas emissions. Energies 2019, 12, 2097 energy) exhibit advantages such as high geothermal energy, stable and long-lasting energy, and low power generation costs. The proportion of geothermal energy in clean energy is increasing yearly [3,4], and geothermal energy, as a new clean energy, has become a focus of future development
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