Abstract
To investigate the strength characteristics of mudstone in deep-buried coal-measure formation, four types of experiments have been conducted: (i) the X-ray diffraction (XRD) test; (ii) the scanning electron microscope (SEM) scanning test; (iii) the point load strength index test; and (iv) the uniaxial compressive strength test. It was concluded that the mudstone of the deep-buried coal measures in the Longtan Formation is dominated by chlorite, quartz, and albite using the XRD test, of which chlorite is primary, accounting for 74.3%. It was found that the three minerals in the mudstone are unevenly distributed using the SEM scanning test, albite is irregularly distributed in chlorite, and quartz is present in the albite and chlorite. Sixty-five specimens were tested for the point load strength index. After processing the data using the method suggested by the International Society for Rock Mechanics and Rock Engineering(ISRM), it was found that the maximum value of Is(50) was 6.10 MPa, the minimum is 0.14 MPa, and 53% of the specimens’ Is(50) values are below 2.0 MPa. The RMT-150C rock mechanics testing machine was used to conduct uniaxial compression tests on six specimens. The maximum uniaxial compressive strength (UCS) value is 59.26 MPa, the minimum value is 31.77 MPa, and the average is 45.64 MPa. Linear fitting and logarithmic fitting are carried out for the correlation between UCS and Is(50). The goodness of fit R2 of the linear fitting is 0.863, and that of the logarithmic fitting is 0.919, indicating a strong correlation between them. When it is challenging to make standard specimens, Is (50) can be used to estimate UCS.
Highlights
uniaxial compressive strength (UCS) of deep-buried coal-measure formation is an important index to evaluate its stability and an essential reference basis for arranging roadway system and selecting mining technology [1,2,3]
According to the suggested method of ISRM, there are strict requirements for the specimen when testing UCS. e most basic requirement is that the length/diameter ratio of the specimen is greater than 2 [7, 8]
Ulusay and Tureli [12] considered that the point load test is most importantly employed in estimating the compressive strength of rock materials
Summary
UCS of deep-buried coal-measure formation is an important index to evaluate its stability and an essential reference basis for arranging roadway system and selecting mining technology [1,2,3]. Andrea and Fisher [9] first used the point load test to estimate the uniaxial compressive strength of rock and considered a linear relationship between them. Shock and Vibration whatever the shape of the specimen is, and the point load strength results correlated closely with those from uniaxial (unconfined) compressive strength testing. Ulusay and Tureli [12] considered that the point load test is most importantly employed in estimating the compressive strength of rock materials. Sahin et al [16] studied the point load strength index of half-cut core specimens and its correlation with uniaxial compressive strength. Eir strength characteristics were analyzed, and the possibility of replacing the uniaxial compression test with point load test was studied, to provide references for scientific decisions such as arranging roadways, selecting support methods, and selecting mining engineering Is study conducted XRD test, SEM scanning test, point load test, and uniaxial compression test in the laboratory to study the strength characteristics of mudstone in deepburied coal-measure strata in detail. eir strength characteristics were analyzed, and the possibility of replacing the uniaxial compression test with point load test was studied, to provide references for scientific decisions such as arranging roadways, selecting support methods, and selecting mining engineering
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