Abstract
The freeze-thaw duration is one of the important factors affecting the change of rock properties. However, this factor has not formed a unified standard in the freeze-thaw cycle test. This study uses saturated tuff samples taken from eastern Zhejiang, China, as research objects to explore the change law of the time required for the rock to reach a full freeze-thaw cycle. Measured results show that the total duration of the freeze-thaw cycle presents an increasing power function with the increase in the number of freeze-thaw cycles. The freezing process is divided into three phases: initial freezing, water-ice phase transition, and deep freezing. The melting process is also divided into three phases: initial melting, ice-water phase transition, and deep melting. The time required for the ice-water phase change stage of the melting process does not change with the increase in the number of freeze-thaw cycles, while the other stages increase as a power function. The proportion of duration of each stage in the freezing process does not change with the increase in the number of cycles. By contrast, the duration proportion of the initial melting phase in the melting process decreases, and the deep melting phase increases. Experimental results of the freeze-thaw cycles of tuff demonstrate that the freeze-thaw duration of the freeze-thaw cycles within 40 times can be set to 9 h. The freezing and melting processes are 6 and 3 h, respectively.
Highlights
Many scholars have carried out several studies on the freeze-thaw cycles of rocks and summarized the types of cycle duration adopted by various freeze-thaw cycle test institutes at present. ese types of cycle can be divided into the following four categories: (1) the cycle test temperature ranges from −20°C to 32°C. e cycle time of the freezing and melting processes is 12 h
Yu et al studied the effects of freeze-thaw cycles on the mechanical properties and permeability of red sandstone under triaxial compression [9]. (2) e same 4 h freezing and 4 h melting process cycle times are used at different freeze-thaw cycle test temperatures
Freeze-thaw damage of rock has always been the key content of frost heavy rock research
Summary
Received 2 June 2020; Revised 8 July 2020; Accepted 9 July 2020; Published 24 July 2020. Ese types of cycle can be divided into the following four categories: (1) the cycle test temperature ranges from −20°C to 32°C. e cycle time of the freezing and melting processes is 12 h. (2) e same 4 h freezing and 4 h melting process cycle times are used at different freeze-thaw cycle test temperatures. E international norms stipulate that the freeze-thaw cycle temperature range is −20°C (±2) to 20°C (±2), and the freezing and melting processes are 15 and 9 h, respectively [25]. The duration and temperature range are factors that must be considered in the freeze-thaw cycle test On this basis, this work measures the time required to reach a full freeze-thaw cycle for the tuff. This work measures the time required to reach a full freeze-thaw cycle for the tuff. e freeze-thaw cycle is divided into freezing and thawing processes. e time variation rules of each process are analyzed to provide the corresponding basis for the overall time of the freeze-thaw cycle test of tuff and the time required for different processes
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