No abstract

The necessity of constructing structures beneath ground level, increases the need of performing deep excavations in urban areas. It is essential to have a reliable estimation about the performance of deep excavation systems. This approach is not accessible via common deterministic analysis methods, since the uncertainty of soil parameters are not considered in these methods. Thus, various probabilistic and non-probabilistic reliability analysis methods are proposed to overcome this shortcoming. Due to the complicated mathematical procedure and lack of thorough database available for soil properties in real projects, which are both required to perform most of the reliability analysis methods, these methods are not welcomed by the engineers in practical projects. Since, it is common to apply deterministic analysis methods, the disadvantage of ignoring the effects of uncertainty on system response still exists in operation. According to the results of researches done in the field of reliability analysis, there are simple proposed methods which can be utilized in practical projects; however, they are not known to the engineers. In the present study a recently developed and simple reliability analysis method called Expert selected set method is applied for the analysis of an urban deep excavation project in Iran. For verification purposes, the results are compared with field measurement values and the reliability analysis results which were obtained using a well-known method called Point estimate method. The comparisons approve the feasibility of investigated method to predict the system performance and providing a reliable estimate of the system response, during the design stage.

Deep excavations in urban areas impose deformation to adjacent structures; hence the reliability of deformation analysis for the real deep excavation projects is very important to be assessed. In this study a framework is presented for the use of reliability methods in deformation analysis of deep urban excavations. The suggested framework is applied for 5 real deep excavation projects implemented during last 10 years. All studied cases were recognized as projects of high importance in urban areas, and were monitored during the excavation process. A non-probabilistic reliability analysis procedure, Random set method, in combination with finite element numerical modeling is applied to obtain the probability of unsatisfactory performance for each case. The reliability analysis results are confirmed by field observations and measurements. Typical results for the probability of analytical deformations exceeding the acceptable values along with the site observations and measured displacements for 5 real deep excavation projects show that the reliability analysis could be a beneficial tool for designer. It is concluded that applying the suggested framework in the design stage of deep excavation projects may lead to design more appropriate systems compared to common deterministic design methods.