Abstract
The flow of cement-based slurry within concentric annular geometry is a major problem of study in the field of engineering, especially regarding the prevention of water ingress in an annulus formed during shaft construction utilizing the artificial freezing technique in China. In this study, an analytical governing equation of motion for the axial flow of an incompressible Newtonian fluid in a long concentric annulus is derived under the condition of high groundwater pressure. A stepwise calculation method is proposed to describe the grouting process based on two injection modes, namely, flow rate control and pressure control. The injection time is divided into a series of time segments; correspondingly, the grouted zone is subdivided into infinitesimal elements. Some key parameters, such as the location, dimension, slurry viscosity, and pressure gradient of each element, can be obtained using the developed MATLAB program. On this basis, the distribution of pressure and slurry viscosity in the grouted zone and the variations in injection pressure at the grouting point and grouting flow rate are determined. Two injection mode cases are investigated to reveal the grout propagation in the concentric annulus. Finally, numerical simulations are conducted and employed to validate and calibrate the calculated results. The results obtained by the present stepwise calculation method show good agreement with the numerical results.
Highlights
Many water-burst hazards have occurred in coal mines in China during the past few decades, causing casualties and significant property losses [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]
In the Dongsheng area, the Ordos basin coal deposit developed in the late Jurassic and is covered by Cretaceous sandstones and fine sandstones [22, 23]. Due to their short period of diagenesis, these strata are characterized by low strengths, weak cementation, and water-rich rock, and full-depth artificial freezing technology is widely used to construct deep mine shafts in this area [24,25,26]
A stepwise calculation method is proposed to describe the grouting process according to pressure control and flow control conditions, and some crucial parameters, such as slurry viscosity, injection pressure, and pressure distribution in the grouted zone, are analyzed through case studies. en, the results of the developed calculation method are validated and compared with numerical simulations; the conclusions are drawn
Summary
Many water-burst hazards have occurred in coal mines in China during the past few decades, causing casualties and significant property losses [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]. In the Dongsheng area, the Ordos basin coal deposit developed in the late Jurassic and is covered by Cretaceous sandstones and fine sandstones [22, 23] Due to their short period of diagenesis, these strata are characterized by low strengths, weak cementation, and water-rich rock, and full-depth artificial freezing technology is widely used to construct deep mine shafts in this area [24,25,26]. In China, dozens of engineering cases of grouting annular channels around shafts have been implemented successfully [25, 26] Based on this rich engineering experience, researchers have proposed several effective grouting techniques, mainly including back wall grouting and perforation grouting. A stepwise calculation method is proposed to describe the grouting process according to pressure control and flow control conditions, and some crucial parameters, such as slurry viscosity, injection pressure, and pressure distribution in the grouted zone, are analyzed through case studies. en, the results of the developed calculation method are validated and compared with numerical simulations; the conclusions are drawn
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