Establishing Empirical Relationships for the Effects of Water Content on the Mechanical Behavior of Gosford Sandstone

The presence of water strongly affects rock properties and would be related to a series of geological disasters. To understand water saturation effects on the mechanical behavior of different rock types and interpret the underlying mechanisms of differences in water sensitivity, three kinds of rocks, namely sandstone, granite and marble, were selected for tests. Uniaxial compression experiments were conducted on specimens under oven-dried and water-saturated conditions. Acoustic emission (AE) techniques were also applied to monitor and record AE signals during tests. Experimental results reveal that water weakens the mechanical parameters of the three tested rocks, such as uniaxial compressive strength (UCS), elastic modulus and critical strain. The sandstone undergoes the greatest weakening with the addition of pore water, the mechanical properties of the granite exhibit relatively minor reductions, while the marble is the least affected by water saturation. The water-weakening degree of rock properties depends on the porosity as well as the mineralogy, especially the proportion of quartz and swelling clays. Moreover, after water saturation, the failure pattern of the sandstone and the granite tends to transform into the shear-dominant mode from the tensile one in dry state, probably due to frictional reduction. However, the water presence does not change the failure mode of the marble.

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“…η for water is about 1 × 10 −3 Pa·s. B and α are assumed to be of the order of unity [64,65]. κ and K are listed in Table 3.…”

Section: The Increase Of Pore Pressurementioning

confidence: 99%

“…UCS reduction against quartz content (data from[4,6,25,[61][62][63][64]). S, sandstone; G, granite; M, marble; Sh, shale.…”

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confidence: 99%

Water-Weakening Effects on the Mechanical Behavior of Different Rock Types: Phenomena and Mechanisms

et al. 2019

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“…Water has a significant effect on the fracture and mechanical properties of rock materials [1][2][3][4]. And a host of geological hazards and engineering disasters are closely related to water, such as landslides, karst collapse, fault activation, water inrush in mine, instability of water-resisting layer, and so on [5,6].…”

Section: Introductionmentioning

confidence: 99%

Compression and Shear Fracture Analysis of Boundary Cracks Containing Water in Rock

Yang

2020

Advances in Materials Science and Engineering

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In order to conserve the water resource during underground mining, the fracture and mechanical properties of rock are important for the stability of water-resisting layers, especially for the fracture behavior of boundary cracks containing water in rock. Considering the swelling of rock under water environment and the influence of water on rock, the stress intensity factors of modes I and II are derived for boundary cracks in rock under compressive and shear stresses. The cracks are divided into the closed and open states. The effects of the crack inclination angle, friction coefficient between crack surfaces, and initial crack length on stress intensity factors are also taken into account. The stress intensity factors for closed and open boundary cracks are verified by numerical and physical experiments, respectively, and the deviation of the results is within 5%. It is shown that pore pressure has different effects on the relationship between stress intensity factor and friction coefficient under different lateral pressures. The effect of water on crack propagation is mainly due to the deterioration of the fracture toughness of the rock. It is found that the critical coefficient λc is a key parameter to determine whether the boundary crack propagates in rock under compression-shear stress. Further studies should be performed to apply the present fracture theory to rock mass or water-resisting layers.

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“…When subjected to tensile load, service failure of the bolts may occur via failure at the grout-rock interface, bolt-grout interface or in the grout medium, depending on which one is the weakest (Indraratna and Kaiser 1990a, b;Li et al 2016). Groundwater has been found to influence failure at the grout-rock interface, partly because saturated conditions alter geomechanical properties including rock strength (Masoumi et al 2017;Osouli and Bajestani 2016;Pan-feng et al 2004). Together with tensile load imparted on the bolt, the reduction in rock strength reduces the effectiveness of the bolt through the degradation of bond strength between grout and rock (Osouli and Bajestani 2016).…”

Section: Introductionmentioning

confidence: 99%

Analysis of the influence of groundwater and the stress regime on bolt behaviour in underground coal mines

Smith

Ramandi

Zhang

et al. 2019

Int J Coal Sci Technol

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The service failure of rock bolts and cable bolts are frequently reported issues in underground coal mines. Whilst numerous experimental investigations concerned with the service failure of bolts have been conducted, numerical modelling offers an alternative approach in evaluating the factors contributing to service failures of bolts in underground mines. In this study, analysis of the influence of groundwater and tensile stress on bolts in underground coal mines was studied through the numerical modelling of a grouted bolt in the immediate roadway roof. Bolt tensile stress and groundwater dripping rates in the immediate roadway roof were analysed using a package based on finite element method to assess the effect of coal roof thickness and claystone bands, as main contributors of known service failures of bolts in roadways of underground coal mines. Increasing coal roof thickness was found to increase bolt dripping rates. Probable location of stress corrosion cracking (SCC) occurrence was established through examining the shift and increase in maximum bolt tensile stress that was exhibited along the bolt length with increasing coal roof thickness. Claystone bands situated at the top and centre horizon of a grouted bolt produced lower bolt dripping rates compared with scenarios with no claystone bands. Intersecting claystone bands at the centre horizon of a bolt for a fully grouted bolt could increase the likelihood of SCC corrosion and bolt failure by contributing to microbial corrosion processes and grout fracturing by tensile stress. This study improves the understanding the bolt failure associated with the presence of groundwater and changing stress environments, which in turn is imperative in formulating strategies to mitigate support element failures and improve the ground support viability.

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Establishing Empirical Relationships for the Effects of Water Content on the Mechanical Behavior of Gosford Sandstone

Cited by 69 publications

References 30 publications

Water-Weakening Effects on the Mechanical Behavior of Different Rock Types: Phenomena and Mechanisms

Water-Weakening Effects on the Mechanical Behavior of Different Rock Types: Phenomena and Mechanisms

Compression and Shear Fracture Analysis of Boundary Cracks Containing Water in Rock

Analysis of the influence of groundwater and the stress regime on bolt behaviour in underground coal mines

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