Abstract
Using the freeze-thaw cycle test chamber, the red sandstone samples are subjected to cyclic freeze-thaw tests. The physical properties, static mechanical properties of freeze-thaw damage rocks, and the compressional wave velocity at specific axial pressure are measured using conventional physical tests and uniaxial compression tests. The mechanical properties of freeze-thaw damage rocks under dynamic and static loading were studied using Hopkinson pressure bar which can exert axial pressure. The studies show that, with the increase of freeze-thaw cycles, the surface layer of the rock sample undergoes spalling phenomenon, the weight gradually decreases, the sample compactness becomes worse, there are microcracks between the cemented particles, and the compressive strength and elastic modulus decrease. Under the static loading, the longitudinal wave velocity of freeze-thaw damaged samples change significantly compared with that of samples without freeze-thaw. The freeze-thaw damage degree, axial pressure, and strain rate are coupled with each other, which together affect the dynamic mechanical properties of samples, and make the variation of mechanical parameters, such as dynamic peak strength and dynamic elastic modulus of rock. The combined action of freeze-thaw damage and axial pressure weakens the strain rate effect of samples, but when the incident wave of SHPB test is same, the dynamic strength and elastic modulus of freeze-thaw damaged samples are reduced compared with those without freeze-thaw. Combining with strain equivalence principle, the constitutive relation of freeze-thaw damage of red sandstone under dynamic and static combined loading can reflect the influence of coupling damage of axial pressure and freeze-thaw, dynamic impact parameters, and other factors, which are in good agreement with the test results.
Highlights
Static Mechanical Properties of Freeze-Thaw Damaged Red SandstoneE freeze-thaw cycles, static tests, and split Hopkinson pressure bar (SHPB) tests of the sample were carried out in accordance with relevant specifications [16, 17]
Combining with strain equivalence principle, the constitutive relation of freeze-thaw damage of red sandstone under dynamic and static combined loading can reflect the influence of coupling damage of axial pressure and freeze-thaw, dynamic impact parameters, and other factors, which are in good agreement with the test results
Cyclic Freeze- aw Test of Samples. e second, third, and fourth groups of rock samples are put into the automatic freeze-thaw box for 10, 20, and 30 freeze-thaw cycles, respectively, in which the temperature range is −20°C∼20°C, and both the freeze and thaw times are 4 hours as a cycle. e mass, volume, and compressional wave velocity of the samples are measured after every 10 freeze-thaw cycles
Summary
E freeze-thaw cycles, static tests, and SHPB tests of the sample were carried out in accordance with relevant specifications [16, 17]. E mass, volume, and compressional wave velocity of the samples are measured after every 10 freeze-thaw cycles. E samples after the freeze-thaw cycles (the freeze-thaw times of samples for group 1–4 are 0, 10, 20, and 30, respectively) are scanned by electron microscope and carried out uniaxial compression test. Uniaxial compression, the longitudinal wave velocity of a sample is collected when the axial pressure reached 5 MPa. 2.1.4. Dynamic and Static Combined Loading Experiment of Freeze- aw Damaged Samples. E SHPB equipment which could apply axial pressure is used to carry out dynamic and static combined loading tests on samples with different freeze-thaw cycles. Dynamic and Static Combined Loading Experiment of Freeze- aw Damaged Samples. e SHPB equipment which could apply axial pressure is used to carry out dynamic and static combined loading tests on samples with different freeze-thaw cycles. e axial pressure values are 0 MPa and 5 MPa, respectively, and the peak values of incident stress waves are 68.9 MPa, 83.6 MPa, and 116.3 MPa, respectively (the air gun pressures are finely adjusted around 0.07 MPa, 0.1 MPa, and 0.14 MPa). e shapes of incident wave, reflected wave, and transmitted wave are obtained, and the stress-strain relationship under the combined load of dynamic and static could be obtained
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
