There is a wide distribution of weakly cemented argillaceous rock masses in areas where there are many coal mines, and their complex characteristics make them more difficult to support. This paper researches this type of rock and studies the slurry diffusion mechanism and grouting reinforcement characteristics of injected rock mass and their relationship with compaction and splitting grouting. The grouting mode is dominated by compaction and splitting. The rheological behavior of cement slurries with different concentrations used in split grouting was studied. The existing grouting equipment was improved, and grouting tests were performed on loose aggregates of weakly cemented primary rock in a certain size range. Subsequently, basic physical parameter determination tests, microscopic tests, and uniaxial tests were performed on grout, and the effects of grouting pressure, moisture content of standard samples, slurry water/cement ratio, and curing time on grouting reinforcement were analyzed. During the grouting process, the pattern of plasma pulse diffusion and reinforcement was summarized as three types: compaction, splitting, and microcracking. The failure modes of rock were summarized as shear failure, shear failure along the interface of the plasma, and splitting damage.
1 November 2021 in KSCE Journal of Civil Engineering
To study the mechanisms and potential control measures for coal mine engineering safety hazards caused by swelling rock, water absorption experiments were performed under different temperature by using an independently developed rock water absorption test system. The swelling pressure, expansion amount and water absorption amount of specimens were monitored in real time. Nuclear magnetic resonance and uniaxial compression experiments were performed. The water absorption rate of the swelling rock specimens increases significantly with increasing water absorption time. The water absorption capacity of the specimens differs considerably under different temperatures. The water absorption curve can be divided into three stages: the severe stage, deceleration stage and equilibrium stage. The water absorption amount and water absorption rate are linearly related to temperature. The curve of the swelling pressure depicts a double peak shape. The expansion curve can also be divided into three stages. With increasing temperature, the expansion rate increases, and the time needed to achieve expansion stability is prolonged. There is a negative linear correlation between the uniaxial compressive strength and the moisture content. The higher the temperature is, the higher the moisture content. The increase in the rock porosity after water absorption is one of the important factors driving the strength attenuation.
The argillaceous weakly consolidated rock is a kind of soft rock that will bring great difficulties in the construction process. Specimens of such rock under different moisture contents are taken as the research object. By the Hopkinson pressure bar test (SHPB), the structural and mechanical characteristics of the rock under dynamic impact are analysed. With increasing moisture content, the transmitted wave amplitude decreases gradually, which indicates that the higher the moisture content of the rock is, the easier it is to deform under dynamic impact and the greater its plasticity. The boundary between plastic failure and brittle failure is 10% moisture content. Through a mercury injection test, the porosity variation is analysed. The porosity of the rock decreases with increasing moisture content after the same dynamic impact. The porosity curve can be roughly divided into two sections with a moisture content of 15% as the boundary. Based on a uniaxial compression test, the elastic modulus, peak strength, and residual strength of specimens after dynamic impact are analysed, and the mechanical properties of the rock are revealed. Its mechanical properties can be divided into three sections with a moisture content of 9.18% and 15.19%, and each section has obvious differences.