Systematic decision support system to select methods of grouted base plug construction: comparative study between TaM versus multi-sleeve injection

In underground projects, the construction managers engineers’ teams experience/confront great challenges to choose a grouting method for the construction of grouted base plug for the all underground station projects constructed in Egypt. It is worth mentioning that there were numerous and diverse conditions in the underground station projects and hence criteria can vary for every single project. Our study successfully incorporated and compiled all these projects criteria to mimic/and match all projects conditions. To combat these challenges, it is crucial to distinctly identify the influencing criteria for the selection of each method and their weights. The importance of obtaining these weights is to evaluate the injection methods before proceeding with the construction works and compare them with other injection alternatives. This study presents an application of multiple-criteria decision-making method based on ranking the influencing criteria. More in particular, a comparative study is carried out among well-known and widely applied methods in injection grout for grouted base plug. Along with data from underground construction experts, two grouting methods are studied, in order to determine the best alternative among the available options, assessed against selected criteria with a view toward assigning weighting levels to each option. Following an overview of the literature around the injection methods, the weighting of each criterion of each method is presented in order to assist the decision-makers to support decisions in the selections in between the grouting applications, where many and often conflicting criteria are present within the underground construction environments such as time, cost, constructability…,etc. Questionnaire surveys are conducted to identify the most important criteria that affect the selection of grouted base plug method, and the interviews with specialized experts have been conducted during our investigation. The results of this study highlighted that the labors and experts, equipment and logistics, construction materials, availability of suppliers and efficiency are the most important criteria that should be considered during the selection of soil improvement methods in underground construction.