Chairat Supachawarote creator Miura, Kinya Chairperson Balasubramaniam, A.S. Examination Committee Noppadol Phien-Wej Examination Committee Guey, Lin Der Examination committee Asian Institute of Technology Partial Scholarship Scholarship donor text series technical report th Bangkok Asian Institute of Technology 2000 continuing eng 154 leaves This study aims to investigate the cause of boiling type of failure in cofferdam and to propose a rational method for the safety design of cofferdam regarding the threedimensional effect of seepage on the occurrence of boiling type of failure. An actual failure of cofferdam due to the boiling induced by seepage force during renovation of the Daiichi-Shinkawa Bridge is introduced. The cofferdam was designed in accordance with the "Directions for Road and Earthworks" of the Japanese Road Association (JRA). Two dimensional seepage considerations were assumed in the analysis and the stipulated minimum factor of safety is 1.5. The cause of the failure is investigated with a series of parametric study using finite element analysis with 2-D plane condition as well as axisymmetric and 3-D conditions. In addition, the parametric study is extended in 3-D condition to investigate the effect of three-dimensional shape of the cofferdam, excavation depth, depth of impermeable base layer, excavation area, anisotropic permeability. From these series of calculation, some features of the relationships of seepage force with the influencing factors and some charts are presented for a simple estimation of the seepage force regarding the three-dimensional effect of seepage force on the stability of cofferdam. A thesis submitted in partial fulfillment of the requirement for the degree of Master of Engineering, School of Civil Engineering Thesis (M.Eng.) - Asian Institute of Technology Coffer-dams Bridges Foundations and piers Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B06564 http://203.159.5.9/ait-thesis/detail.php?q=B06564 181100 20260817171632.0