Effect of properties of tailings and binder on the short-and long-term strength and stability of cemented paste backfill

Cemented paste backfill containing coal gangue and fly ash (CGFACPB) is an emerging backfill technique for coal mines that allows environmentally hazardous coal gangue and fly ash to be reused in the underground goaf. Meanwhile, CGFACPB can provide an efficient ground support and reduce the surface subsidence. Due to the difference of consolidation environment between the laboratory and the field, the mechanical properties of the cemented paste backfill vary significantly. In this paper, the core specimens were collected from an underground coal mine where the CGFACPB was used for coal mining, and the mechanical properties of the collected specimens were investigated. The cores were obtained from the underground coal mine, and then the standard cylinders or discs were prepared in laboratory. The uniaxial compressive strength (UCS), Young’s modulus, and Poisson’s ratio were determined by the compression tests, and the tensile strength was achieved by the Brazilian test. Then the internal friction angle and cohesion were calculated using the improved Mohr–Coulomb strength criterion. The results showed the development of UCS can be divided into four stages, and the final long-term stable value was about 5.1 MPa. The development of Young’s modulus had similar trend. Young’s modulus had a range from 550 MPa to 750 MPa and the mean value of 675 MPa. Poisson’s ratio gradually increased with the underground curing duration and eventually approached the stable value of 0.18. The failure type of compression samples was mainly single-sided shear failure. The development of tensile strength can be divided into two stages, and the stable value of the tensile strength was about 1.05 MPa. The development of cohesion can be divided into four stages, and the stable value was about 1.75 MPa. The stable value of the internal friction angle was about 25°. This study can provide significant references for not only the long-term stability evaluation of CGFACPB in the field but also the design of optimal recipe of the cemented paste backfill (CPB).

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Relevance of SEM to Long-Term Mechanical Properties of Cemented Paste Backfill

Geotechnical and Geological Engineering ◽

10.1007/s10706-018-0455-5 ◽

2018 ◽

Vol 36 (4) ◽

pp. 2171-2187 ◽

Cited By ~ 10

Author(s):

Naguleswaran Niroshan ◽

Ling Yin ◽

Nagaratnam Sivakugan ◽

Ryan Llewellyn Veenstra

Keyword(s):

Mechanical Properties ◽

Cemented Paste Backfill ◽

Paste Backfill

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Long-term coupled behaviour of cemented paste backfill in load cell experiments

Geomechanics and Geoengineering ◽

10.1080/17486025.2016.1145256 ◽

2016 ◽

Vol 11 (4) ◽

pp. 237-251 ◽

Cited By ~ 6

Author(s):

Alireza Ghirian ◽

Mamadou Fall

Keyword(s):

Load Cell ◽

Cemented Paste Backfill ◽

Paste Backfill

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Potential Effect of Porosity Evolution of Cemented Paste Backfill on Selective Solidification of Heavy Metal Ions

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph17030814 ◽

2020 ◽

Vol 17 (3) ◽

pp. 814 ◽

Cited By ~ 6

Author(s):

Yixuan Yang ◽

Tongqian Zhao ◽

Huazhe Jiao ◽

Yunfei Wang ◽

Haiyan Li

Keyword(s):

Mine Water ◽

Pollution Assessment ◽

Potential Effect ◽

Water Tank ◽

Cemented Paste Backfill ◽

Porosity Evolution ◽

Mining Depth ◽

Paste Backfill

Cemented paste backfill (CPB) is a common environmentally friendly mining approach. However, it remains undetermined whether CPB pollutes underground mine water. Tank leaching analysis of a CPB mass in distilled water was performed for 120 d, and water quality was tested in situ for a long-term pollution assessment. Computerized tomography was also used to determine the CPB micro-pore structure and ion-leaching mechanism. The dissolved Zn2+, Pb2+ and As5+ concentrations in the leachate peaked at 0.56, 0.11 and 0.066 mg/L, respectively, whereas the Co2+ and Cd2+ concentrations were lower than the detection limit. The CPB porosity decreased from 46.07% to 40.88% by soaking, and 80% of the pore diameters were less than 13.81 μm. The permeability decreased from 0.8 to 0.5 cm/s, and the quantity, length, and diameter of the permeate channels decreased with soaking. An in-situ survey showed novel selective solidification. The Zn2+ concentration in the mine water was 10–20 times that of the background water, and the Pb2+ concentration was 2–4 times the regulated value. Although the Pb2+ content decreased significantly with mining depth, there remains a serious environmental risk. Mine water pollution can be reduced by adding a solidifying agent for Pb2+ and Zn2+, during CPB preparation.

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