Effects of chloride on the early mechanical properties and microstructure of gangue-cemented paste backfill

Chen, Shaojie; Du, Zeyu; Zhang, Zhen; Zhang, Huawei; Xia, Zhiguo; Fan, Feng

doi:10.1016/j.conbuildmat.2019.117504

Cited by 92 publications

(42 citation statements)

References 46 publications

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“…In order to observe the microscopic morphology and cracks of the fracture, scanning electron microscopy (SEM) was used to observe and compare the changes of the fracture morphology of the rock before and after heating, such as steps and river patterns [30], as well as the clay minerals of sandstone (e.g., kaolinite or green mudstone) [31]. At the same time, in order to understand the effects of temperature on the sandstone minerals, microdomain chemical analysis was performed using Energy Dispersive X-ray Spectroscopy (EDS).…”

Section: Sem Observation Of Microfracturesmentioning

confidence: 99%

Effect of High Temperature (600°C) on Mechanical Properties, Mineral Composition, and Microfracture Characteristics of Sandstone

Zhang

2020

Advances in Materials Science and Engineering

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Rock destruction under high-temperature conditions is a key issue for nuclear waste treatment projects, underground coal gasification, and improvement of the use of geothermal energy for heating. Therefore, in this study, various methods and techniques were integrated to study the changes in mechanical properties, mineral composition, and microscopic fracture characteristics of Sichuan sandstone treated at 600°C. First, the fracture toughness and indirect tensile strength of untreated sandstones and high-temperature treated sandstones were tested by the MTS testing machine, and the double-K model (DKFM) was used to estimate the unstable fracture toughness. Then, the diffraction spectra of sandstone were analyzed with an X-ray diffractometer to determine the mineral composition change after heat treatment. Finally, the microscopic features of sandstone were observed through a scanning electron microscope (SEM) and optical microscope. The results show the following. (1) There is no significant change in the tensile strength and fracture toughness of Sichuan sandstone treated at 600°C. (2) The brittleness of Sichuan sandstone decreases and the ductility increases after high-temperature treatment. (3) The unstable fracture toughness value Kun obtained by the double-K model (DKFM) is significantly larger than the apparent fracture toughness value Kif. (4) After treatment at 600°C, the clay minerals in the sandstone changed significantly. Kaolinite is dehydroxylated to metakaolinite, which may increase the ductility of the rock.

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Section: Sem Observation Of Microfracturesmentioning

confidence: 99%

Effect of High Temperature (600°C) on Mechanical Properties, Mineral Composition, and Microfracture Characteristics of Sandstone

Zhang

2020

Advances in Materials Science and Engineering

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“…The stability of underground structures is closely related to the type and properties of rock . Rocks have complex mechanical properties, laboratory experiments alone are not adequate to study their properties and some in situ measurements are necessary . In particular, strain information along the rock bolts should be collected to reveal long‐term movements of the rock mass and to allow an operator to take necessary precautions .…”

Section: Introductionmentioning

confidence: 99%

Monitoring and correction of the stress in an anchor bolt based on Pulse Pre‐Pumped Brillouin Optical Time Domain Analysis

Liu

Chai

Chen

et al. 2020

Energy Science & Engineering

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Bolt is an important connection in underground construction and monitoring its stress characteristics is essential to evaluate the effectiveness of bolt. The strain information collected along a rock bolt reveals the long-term movement characteristics of rock mass, which greatly helps toward disaster prevention and risk warning.Grooving on the surface of a bolt and embedding an optical fiber is one of the main methods for monitoring the anchorage performance and stress distribution around the bolt in underground engineering. In this study, Pulse Pre-Pumped Brillouin Optical Time Domain Analysis (PPP-BOTDA) technology is used to evaluate the stress, axial force, and shear stress distribution of the bolt under tensile load for different types (grooved and nongrooved) of bolts embedded in concrete with resin as anchoring agent. The results show that the PPP-BOTDA sensor can be used to monitor the stress state of the bolt embedded in concrete with resin as anchoring agent when the bolt is subjected to a tensile force. However, the apparent stress value measured in this way is not the actual stress value of the bolt, but is an increased value caused due to the groove. The closer to the exposed end of the bolt, the greater is the deviation between the apparent stress value and the actual stress value of the bolt. Based on the monitoring results from this experimental study, a stress reduction calculation method is proposed, which can change the measured value into the actual stress of the bolt. K E Y W O R D Saxial force, bolt, PPP-BOTDA technology, pullout test, shear stress 2012 |

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“…Strip mining areas also have hidden dangers of overburden disasters due to long-term creep of coal pillars [3]. Backfill mining, as a trend in modern mining, can effectively alleviate the above problems [4][5][6][7]. We have proposed a strip backfill mining method of "mining 7 m to retain 8 m" for a Shanghe coal mine, that is mining a 7 m wide strip and leaving an 8 m wide strip pillar [1].…”

Section: Introductionmentioning

confidence: 99%

Study on Rheological and Mechanical Properties of Aeolian Sand-Fly Ash-Based Filling Slurry

Shao

Wang

et al. 2020

Energies

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Backfill mining is the most environmentally friendly mining method at present, which can effectively control the surface subsidence, improve the recovery rate, and has good social and economic benefits. The purpose of this study is to solve the environmental problems caused by solid waste, combined with the rich geographical advantages of aeolian sand in the Yushenfu mining area of China. The rheological properties of the aeolian sand-fly ash-based filling slurry with different fly ash content are studied by experiments, and the strength development law of the filling body under different age and fly ash content are studied from the macroscopic and microscopic points of view. The rheological experiments showed that the increase of the amount of fly ash has a significant effect on the thixotropy, plastic viscosity, and yield stress of the filling slurry. Additionally, rheological properties of aeolian sand-fly ash-based filling slurry conform to the Bingham model. With the increase of the amount of fly ash, the performance of the filling slurry has been significantly improved. Uniaxial test and scanning electron microscope observation showed that the influence of fly ash on the strength of the filling body was mainly reflected in the late stage of maintenance, but was not obvious in the middle stage. Fly ash particles mainly bear the role of “water reduction” and a physical filling effect, which makes the filling slurry thicker and the internal structure more closely spaced. The volcanic ash reaction of fly ash is lagging behind the hydration reaction of cement; the secondary product of the delayed reaction is filled in the pores of cement hydrates, which can greatly reduce the porosity of the backfill body and increase the later strength of the backfill body. It provides a guarantee for the safe replacement of coal pillars in the working face.

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Effects of chloride on the early mechanical properties and microstructure of gangue-cemented paste backfill

Cited by 92 publications

References 46 publications

Effect of High Temperature (600°C) on Mechanical Properties, Mineral Composition, and Microfracture Characteristics of Sandstone

Effect of High Temperature (600°C) on Mechanical Properties, Mineral Composition, and Microfracture Characteristics of Sandstone

Monitoring and correction of the stress in an anchor bolt based on Pulse Pre‐Pumped Brillouin Optical Time Domain Analysis

Study on Rheological and Mechanical Properties of Aeolian Sand-Fly Ash-Based Filling Slurry

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