Abstract
Moisture content (MC) and freeze-thaw (F-T) process have an important influence on the mechanical properties of rock and its rockburst tendency in the cold region. In addition, uniaxial compressive strength (UCS) of rock is of great importance in evaluating weathering durability, frost resistance, and bursting liability of rock. In this study, the UCS of rock and bursting liability index of rock including elastic energy index (WET), impact energy index (WCF), elastic strain energy index (ES), and modified values of brittleness index (BIM) were measured by laboratory tests. These tests were implemented in six different MC (0, 0.58, 1.06, 1.82, 2.43, and 2.80%) and 20 F-T cycles. The relationship between rock mechanical properties, bursting liability of rock, and MC after freeze-thaw damage was established, and the control mechanism of moisture content on mechanical properties and rockburst tendency of rocks in cold regions was revealed. Uniaxial compressive test results showed that the UCS of rock decreases significantly with the increase of MC. Under the action of F-T cycles, WET, WCF, and ES decrease with the increase of MC, and BIM of rock increases gradually. This indicates that the rockburst tendency of sandstone decreases with the increase of MC. To calculate WET, WCF, ES, and BIM of sandstone samples, new empirical equations were established and put forward under different MC after 20 F-T cycles.
Highlights
In the special natural environment of cold regions, one of the hot topics in the field of geotechnical engineering is the influence of freeze-thaw (F-T) cycles on the physical and mechanical properties and bursting liability of rocks [1,2,3]
It can be seen that the Uniaxial compressive strength (UCS) of sandstone decreases from 82.39 MPa to 51.65 MPa with the increase of moisture content under F-T action. e deterioration of UCS is due to the accumulation of long-term fatigue damage under freezethaw action
Under the action of F-T cycles, the stress-strain curve of sandstone under uniaxial compression can be roughly divided into four stages: compaction stage, linear elastic stage, weakening stage, and failure stage. e loading and unloading curves of sandstone with different moisture content under F-T cycles action are shown in Figure 6(b). ese curves can be used to calculate all kinds of rockburst tendency indexes and make a comparative analysis
Summary
In the special natural environment of cold regions, one of the hot topics in the field of geotechnical engineering is the influence of freeze-thaw (F-T) cycles on the physical and mechanical properties and bursting liability of rocks [1,2,3]. Uniaxial compressive strength (UCS) is an engineering index to evaluate the durability and bursting liability of rock under freeze-thaw cycles. Mousavi et al [17] studied the influence of freeze-thaw cycles on the uniaxial compressive strength of schists. Zhao et al [20] investigated the effect of freeze-thaw cycles on the uniaxial compressive strength and microstructure of oil shale. Ey found that the increase of F-T cycles had a significant impact on the uniaxial compressive strength.
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