Proceedings of the 37th Annual Conference on Deep Foundations, 2012, Houston, TX, USA, (DFI)
Preliminary Assessment of Reliability and Sampling Requirements for Deep Mixing Method (DMM) Foundations for LNG Processing Facility and Storage Tank
Edward C. Clukey, Attasit Korchaiyapruk, Paul J. Sabatini, Paul Summers, Willem (Billy) Villet, Kevin Richardson
A deep mixing method (DMM) foundation was selected by the Project Team for a very large LNG facility in West Africa. As described in a companion paper, this foundation consists of a large number of columns installed by mixing cement with in-situ soils. The foundations are arrayed as a variety of honeycombed type configurations which, if installed to desired specifications, can provide a robust foundation alternative. The foundation is capable of distributing loads and limiting settlements even if some of the soil in the columns is not fully mixed during installation. An important part of the overall quality assessment program, therefore, involved developing a testing program to verify the methodology. In addition the impact of potential defects in columns on the overall foundation integrity had to be assessed. This paper describes some of the preliminary work done to establish the requirements for the quality assurance program. A key component of this program involved the sampling frequency used to assess potential defects in the columns. To verify the column integrity 104- mm samples were taken continuously at a selected frequency through the 23 m long columns. The preliminary work described in this paper demonstrated that the appropriate sampling frequency depends on both the desired reliability level as well as the number of defective columns encountered during testing. Initial finite element analyses were performed to assess the extent that defects could occur in columns within the honeycombed structure without adversely affecting the overall foundation integrity. The results from this work demonstrated that the spatial location of the defects was critical to properly assessing the foundation integrity. In addition to column sampling a load test was performed as part of the foundation verification process. The methods used to apply appropriate loads so that loads at the bottom of the columns approached design values are discussed in the paper. The results obtained from this preliminary study were then used to help develop a more comprehensive assessment program, described in a companion paper, to determine the robustness of the DMM foundations for both the LNG processing facilities and a condensate tank.
|article #1855; publication #99 (AM-2012)|