This paper presents an experimental investigation on the propagation
of chemical grouting in a two-dimensional permeated fracture network
with various aperture widths. As grouting engineering is often concealed
in most experiments, the propagation of grout in fractures is not
fully understood. The anisotropic permeability of geological masses
with different aperture widths was found and has been investigated
since 1960. The deflection flow effect was first found by Tian for
groundwater flow in two groups of fractures with different aperture
widths. Field grouting indicated that the grout propagates along a
group of fractures with larger apertures that are longer while propagating
a shorter distance along fractures with small apertures. This phenomenon
implies a deflection for grout propagation in fractures with different
aperture widths. The results of our study confirm this and indicate
that there would be an anisotropy of grout propagation when the two
groups of aperture widths are different. The water flow conditions
also cause the difference in grout propagation length. When the aperture
widths of the two groups of fractures are the same, the propagation
shows symmetrical ellipse propagation. The results show the anisotropy
of the grout increases as the aperture width ratio increases. This
study helps in understanding the mechanism of chemical grouting in
fractures with different apertures and flowing water and outlines
some implications for grouting design in a fractured rock mass.
This paper presents an experimental and field investigation on the efficiency of plugging by pouring aggregate in different sequences through multiple boreholes in a tunnel with flowing water. There have been controversies surrounding the selection of the pouring order for different particle sizes of aggregates and the order in different boreholes. A visualized experimental setup is used to investigate the influence of the pouring orders on the efficiency of plugging through multiple boreholes under the flowing-water condition. A case study of the salvage of a flooded mine using ground directional boreholes was investigated and compared with the experimental results. The water-pressure difference at the aggregate-capping moment, when fine aggregate was poured first and coarse aggregate later, was relatively small, compared to that when fine aggregate was poured upstream and coarse aggregate, downstream. The result implies that the efficiency of plugging with the order of pouring fine aggregate first and coarse aggregate later in different boreholes is better than that with the order of pouring fine aggregate upstream and coarse aggregate downstream. When the poured aggregate is about to be capped, increasing the pouring intensity with the same or a larger particle size is more conducive to capping. The case study shows that pouring fine materials in the early stage reduced the cross-sectional area; in the later stage, the aggregate particle size was gradually increased, which can be helpful in forming an effective water-barrier section in the tunnel. The pouring of aggregate provided a base for cement grouting to form a water-plug section with a length of 106 m, resulting in a sealing efficiency of 100% for the case.
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