Proposal of Simplified Numerical Analysis to Simulate Plastic Grout Behavior during Pressurized Underground Cavity Filling

It is necessary to properly fill underground cavities encountered during construction works in order to eliminate the risks of subsidence and depression prior to building a sound foundation that supports structures. The most common method of filling treatment is to pour a highly fluid cement-based material over a wide area, but "plastic grout filling" is also often used, in which the grout that has been adjusted to have plasticity is pumped and supplied into flat cavities. The lateral reaches of plastic grout supplied from the inlet hole has a relative difference due to ease of spreading depending on the height of the filling space. It does not spread to concentric circles unless the condition is completely uniform height. In former studies, the author has clarified the factors that influence the progress of the filling area and the required inlet pressure through experimental studies as well as by computational fluid dynamics. In this paper, the author studied a simplified numerical analysis method that easily calculates the reaches of the grout that spreads laterally in a cavity with a height of less than about 500 mm. The focus is put on the practical utilization for the prediction and evaluation of the filling works. As an algorithm for simplified analysis, a convergence calculation was proposed on the filling experiment results that spread in two directions, left and right, while balancing the inlet pressure generated by the stepwise advancement of the filling area in both directions. The effectiveness of this method was confirmed through comparison with the results of four experiments in which the cavity filling heights were changed.