Multi-criteria evaluation for soft soil improvement decision making case study: Padang - Sicincin Toll Road project Available to Purchase

Padang – Sicincin Toll Road is part of the main priority for the construction of the Pekanbaru - Bangkinang - Payakumbuh - Bukittinggi - Padang Panjang - Lubuk Alung - Padang Toll Road. Based on soil investigations results on Padang - Sicincin Toll Road route which had been carried out by planning consultant, including field work results in the form of sondir and drills in the SPT as well as laboratory tests. The subgrade NSPT value was below 4. Therefore, it is needed to improve the subgrade to meet the stability of the embankment. In this study, the researcher evaluated the multi- criteria selection of soft soil improvement methods on the Padang – Sicincin Toll Road Project, by using the Analytical Hierarchy Process (AHP) method. The multi criteria used in the selection of soft soil improvements were technical design, work method (construction safety risk assessment), time and cost implementation. While the alternative for soil improvement used the mini piles load transfer method, PVD Preloading, vibro stone column (VSC) and Modular Grout Column (KGM). This research used questionnaires and collecting documentation from the respondents who work on the Sicincin – Padang Toll Road Project as data-collecting method. The results of the questionnaire are the comparisons between criteria those mentioned before and then the data is analyzed using the AHP method. The results show that the highest priority scores between criterias are [1] technical design with score of 58.9% and [2] Cost with score of 21%. The next step is to determine the priority score between the soil improvement alternatives i.e. Mini Piles, PVD-Preloading, Vibro Stone Column and Modular Grout Columns. The priority score for each soil improvement alternative is obtained from soil improvement planning analysis for technical design criteria, risk assessment for work methods criteria, comparison of site-construction’s time for time criteria, and comparison of work costs for cost criteria. The results show that the highest priority scores for soil improvement alternative is [1] technical design with score of 25% for every alternative, [2] work method with score of 28.1% for the PVD-Preloading alternative, [3] Implementation time with score of 57.4% for the Vibro Stone Column alternative, and Cost with score of 52.4% for PVD-Preloading alternative. The results of the scoring between criteria and alternatives for each criteria were combined to obtain the final priority score to determine the most optimum soil improvement alternatives on Sicincin – Padang Toll Road project. The most optimum soil improvement alternatives used on Sicincin – Padang Toll Road project is PVD Preloading with score of 29.4%.