To investigate the influence of probe size on the miniature penetration strength (\({q}_{c}\)) of fluidized solidified soil, miniature penetration tests were conducted on fluidized solidified soil specimens with varying probe diameters (\({d}_{p}\)) and stabilizer contents (\({\omega}_{s}\)). The micro-mechanism of the size effect was subsequently revealed through DEM simulations, leading to the proposal of a \({q}_{c}\) prediction formula incorporating the size effect. Experimental results demonstrate that \({q}_{c}\) decreases rapidly at first and then more gradually as \({d}_{p}\) increases. This \({d}_{p}\)-dependency of \({q}_{c}\) is more significant in lower-strength specimens. For instance, the \({q}_{c}\) ratio between the 2mm and 5mm probes was 1.43 for specimens with \({\omega}_{s}\)=3% but only 1.28 for specimens with \({\omega}_{s}\)=18%. DEM simulations suggest that the normal stress acting on the probe tip is the primary component of \({q}_{c}\) and is nearly independent of \({d}_{p}\). Conversely, the frictional force on the probe lateral surface, which is proportional to \({d}_{p}\), is identified as the source of the size effect. Furthermore, the zones of stress disturbance and cementation breakage induced by probe penetration extend approximately 0.5 \({d}_{p}\) from the probe shaft. Regardless of the stabilizer contents, the penetration stress can be predicted using an inverse proportional function with respect to \({d}_{p}\).
