Grouting is an important process for stability control of unfavourable geology. A multi-parameter grouting monitoring device was designed to monitor pump pressure, inlet density, outlet density, outlet electrical resistance and osmotic pressure. On the basis of multi-source information, this paper presents an experimental study of the process of grouting colloidal nano-silica into an over-broken coal mass, which was verified by percolation mechanics theory and numerical simulation simultaneously. The porosity and permeability of the injected sample were 15.34% and 5.45 mD. The results showed that the variation of pump pressure generally showed an obvious three-stage regularity. The time-dependent curves of outlet density and outlet resistance were consistent with that of pump pressure, whereas the curve of inlet density was opposite to that of pump pressure. The law of the dominant penetration mechanism was as follows: miscible displacement mechanism in the first stage (0–46 min), Darcy flow in the second stage (46–200 min) and filtration flow in the third stage. This research can guide grouting theory study and design in an over-broken rock mass.
Taking the shield tunnel project of Guangzhou Metro Line 8 from Tongdewei Station to Shangbu Station as the research background, using the research method of finite element simulation and site monitoring, this paper analyses the influence rules of shield tunneling on ground subsidence under the condition of different hard rock height ratios. The research results show that in the process of crossing different hard rock height ratio composite stratum, as the hard rock height ratio decreases, the value of ground settlement decreases and settlement tank becomes shallow. The surface subsidence in different hard rock height ratio strata is obviously different, and the maximum difference is about 8.6 mm; The influence of the hard rock height ratio on the surface longitudinal settlement is mainly reflected in the position change of the beginning and the end of the settlement. With the increase of the hard rock height ratio, the shield construction reduces the amount of the surface longitudinal settlement and its influence range; Through the research, it is found that the hard rock height ratio in the 0-0.2 and 0.5-1 is the sensitive interval, and the settlement value in these two hard rock height ratio interval varies greatly. It is necessary to pay attention to the uneven settlement of the ground surface caused by shield construction in the sensitive hard rock height ratio interval. The research results of this paper can provide reference value for similar shield construction in upper soft and lower hard composite stratum.
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