A methodology to build a groutability formula via a heuristic algorithm

The goal of this study is to provide a methodology to develop a groutability (N) formula of sandy silt soils using microfine cement grouts in a permeation grouting. Because the Fines Content (FC) of the sandy silt soils studied is relatively high, and the size of the grouts used is significantly smaller than the Portland cement, the existing empirical formulas cannot deliver a promising prediction of N. Support Vector Machines (SVMs) is an alternative tool used to predict N. However, SVMs do not provide an explicit formula, which creates an obstacle for practical engineers. Thus, a heuristic algorithm (the Tabu search, TS) was used to build the prediction formula. A total of 240 in-situ data samples were analyzed to ensure the accuracy of the proposed formula. The format of the existing empirical formula was adopted in the proposed TS-based formula. Four parameters were considered in our TS models: the effective soil particle size (D (10)), the soil particle size (D (15)), the water-to-cement ratio (w/c) and the FC. The prediction accuracy of the TS-based formula was approximately 94.17%, indicating that the proposed formula is a suitable tool. Because the proposed formula has a similar format to that of formulas that are typically used, the proposed approach can be implemented readily in practical engineering settings. Note that the proposed formula was only verified by the collected data samples, the suitability of applying the built formula to other conditions needs more investigation.