Mechanical Characteristics and Failure Mechanism of Siltstone with Different Joint Thickness

Li, Huigui; Yang, Zhengkai; Hua-min, LI

doi:10.1155/2020/3824538

“…Broken rock cracks vary from subtle cracks to wide cracks, and these repaired cracks of various widths may have diverse infuences on the mechanical properties of a rock mass [46]. Terefore, investigating the efect on the strength recovery of a ruptured rock mass with diverse crack widths flled with repair grout is signifcant.…”

Section: Introductionmentioning

confidence: 99%

Strength Recovery Effect of Bisphenol A Epoxy Resin E44 on Rock Masses with Various Crack Widths

Zhou

¹

,

Zhang

²

,

Zhang

³

et al. 2023

Advances in Civil Engineering

0

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As a desirable bonding and repair material, epoxy resin combined with other materials is widely used in civil engineering, but its application in underground rock engineering is still limited compared with the wide use of cement grout. To explore and optimize the effect of room temperature-cured bisphenol A epoxy resin E44 on the strength recovery of rock samples with cracks of various widths, the uniaxial compressive strength (UCS) of epoxy resin was studied and the mass ratio of the curing agent to epoxy resin ( k C E ) was adjusted and optimized. On this basis, the UCS of the selected epoxy resin was investigated by adding diverse amounts of ethanol so that the ratio corresponding to the repair material with better mechanical properties could be selected. Artificial cracks of various widths were filled with the optimized materials, and then, a UCS test was conducted on the repaired rock samples to evaluate the effect on strength recovery and compare it with that of ultrafine Portland cement (UPC). The results show that the UCS of epoxy resin stones increases when k C E ≤ 0.25 and decreases when k C E > 0.25, reaching a peak of 92.41 MPa. Furthermore, as the mass ratio of ethanol to curing agent and epoxy resin ( k A ) increases, the UCS increases to 94.65 MPa for k C E = 0.25 and k A = 0.01. The crack width influences the UCS of the repaired rock mass. With increasing crack width, the effect of epoxy resin on recovery continuously improves, whereas that of UPC shows the opposite trend. Compared with UPC, epoxy resin has an overwhelmingly greater effect on strength recovery. For instance, for a 3 mm-wide crack, the recovered UCS for 28 d epoxy resin is 83.48 MPa, with much larger peak strains, and the strength recovery rate ( k r ) is 77.55%; however, the k r of UPC is only 15.12%.

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“…As early as 1967, Wager [2] put forward the concept of layered rock mass in the study of igneous rock, which had an important influence on geological research. Subsequently, many scholars [3][4][5][6][7][8] have conducted a lot of studies on the properties of single-layered rock mass such as shale and sandstone. However, in deep engineering, more and more problems of layered rock masses, which are different from general rock mechanics, have been found.…”

Section: Introductionmentioning

confidence: 99%

An Experimental Investigation on Mechanical Properties and Failure Characteristics of Layered Rock Mass

Zheng

¹

,

Zhang

²

,

Huang

³

et al. 2023

Applied Sciences

3

0

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Layered rock mass is a common rock mass structure with diverse forms and complex mechanical properties. Three types of composite layered rock mass prepared using sandstone and shale can be divided into sandwiched type, interbedded type and superimposed type. The total height of the combined rock mass is 50 mm, which is a cylinder composed of sandstone and shale with a diameter of 25 mm and different thickness. Uniaxial compression tests on sandstone, shale and combined rock mass were performed. The results show that, with the increase in the content of soft components, the compressive strength and elastic modulus of the combined rock mass tend to decrease. The mechanical properties of the superimposed rock mass will be between the two components and close to the soft component in numerical value. The mechanical properties of sandwiched rock mass are obviously affected by the properties of the sandwiched rock. When the content of the components is consistent, interbedded rock mass often shows higher strength and elastic modulus. Compared with other rock mass, interbedded rock mass has more stable mechanical properties. The stress–strain curve can be divided into the compaction stage, elastic stage, plastic development stage and post-fracture stage. The composition content of the rock mass plays a decisive role in the compaction stage. The failure modes are mainly shear failure and tensile failure. With the increase in soft rock content, the failure degree of soft rock is gradually weakened, and the failure modes show a trend from tensile failure to shear failure. The experimental results provide theorical guidance for underground engineering construction.

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“…Liu et al (2016) studied non-penetrating jointed rock mass and developed a dynamic damage constitutive model under uniaxial compression. Li H. G. et al, (2020), Li et al (2021), Li et al (2020b) use siltstone, medium grained sandstone, coarse-grained sandstone and coal in the strata of Bulianta coal mine and Buertai coal mine in Shendong mining area as the research object, and analyzed the influence of interlayer thickness on the mechanical properties of jointed rock. They found that the thickness of the interlayer has a significant effect on the mechanical properties of the jointed coal rock and the interlayer thickness has a significant influence on the mechanical properties of the jointed coal rock.…”

Section: Introductionmentioning

confidence: 99%

Influence of Water Saturation Time on Microstructure and Mechanical Properties of Jointed Limestone

Li

¹

,

Wang

²

,

Wang

³

et al. 2022

Front. Earth Sci.

1

0

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In order to study the influence of water saturation time on the mechanical properties of jointed limestone, the joint limestone samples with a crack length of 20 mm and a crack angle of 30° are saturated with water for 0, 1, 3, 5 and 7 days and tested with the RMT-150C mechanical test machine. The results show that the water saturation time has a significant effect on the stress-strain curve, peak strength, elastic modulus, crack development and failure characteristics of the jointed limestone. There is a step rise or fall phenomenon near the peak stress. The peak strength and elastic modulus of the joint limestone are significantly negatively correlated with the saturated time. Compared with that of the saturated 0-day sample, the peak compressive strength of the saturated 1-day, 3-day, 5-day and 7-day samples was decreased by 16.5%, 24.7%, 43.6%, and 47.7%, respectively, and the elastic modulus decreased by 11.0%, 32.0%, 45.0%, and 67.9%, respectively. Saturated water cracks the skeleton particles of the limestone samples, and the length of the microscopic pores and fissures increased gradually. The phenomenon that the number and length of cracks increase with the increase of the water saturation time will weaken the mechanical properties of the jointed limestone. The physical and chemical reactions, lubrication, and pore water pressure produced by water-saturated water-rock interactions make it easier for the Mohr stress circle to reach the limit equilibrium state. Saturated water reduces the degree of fragmentation of the sample, and the integrity of the fracture surface is higher after failure. The findings in this paper are helpful to further reveal the mechanism of the crushing of supports and the frequent occurrence of water gushing accidents at the working face in the Xinhua region of northwestern Guizhou.

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Mechanical Characteristics and Failure Mechanism of Siltstone with Different Joint Thickness

Cited by 4 publications

References 8 publications

Strength Recovery Effect of Bisphenol A Epoxy Resin E44 on Rock Masses with Various Crack Widths

Strength Recovery Effect of Bisphenol A Epoxy Resin E44 on Rock Masses with Various Crack Widths

An Experimental Investigation on Mechanical Properties and Failure Characteristics of Layered Rock Mass

Influence of Water Saturation Time on Microstructure and Mechanical Properties of Jointed Limestone

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