Assessment of pipe powder in soil improvement applications: an optimization by response surface methodology

Experimental design methods have become very popular approaches in engineering studies thanks to providing some advantages to reduce time period of experiments. In this study, shear strength characteristics of sandy soils were investigated by using central composite design (CCD) approach which is one of the response surface methods. Shear box test results performed at different time intervals were used to design CCD. In model application, the effect of time period under constant load (TPUL) and pipe powder (PP) content (8–12–16%) were used as independent factors to observe shear strength characteristics. Regression equations, variance analysis results, and factor interactions of response variables were used as statistical parameters to analyze CCD performance. Experimental results showed that TPUL is a significant parameter. CCD analysis also determined the importance of TPUL and suggested 14 days as the best time period. CCD results also showed that the optimum PP content can be selected as 12%.