Optimal design of prefabricated vertical drain-improved soft ground considering uncertainties of soil parameters

Prefabricated vertical drains (PVDs) are widely used to accelerate the consolidation process within soft ground. The overall degree of consolidation (DOC) of soft ground is highly dependent on the arrangement of PVDs, such as their length and spacing. Nevertheless, only the ranges of spacing and length are recommended in codes and standards, which renders it difficult for designers to determine the appropriate arrangement of PVDs. A method is proposed in this paper to determine the appropriate arrangement of PVDs based upon multiple objectives, such as cost, safety, and design robustness. In this method, the design robustness is evaluated by the signal-to-noise ratio of the overall DOC, which is determined using Monte-Carlo simulation based on the statistics of uncertain soil parameters. A framework is proposed based on the optimal procedure and illustrated with an example. The results indicate that the proposed method can determine the most preferred arrangement of PVDs. Additionally, compared with the traditional deterministic method, it can suggest a series or a unique optimal design when the uncertainties of soil parameters are considered. Furthermore, factors affecting the most preferred arrangement are discussed.