Abstract:
This research aims to study the deflection behavior of sheet pile in the Aquarium construction of Siam Paragon project for excavation of 10.55 m depth with 4 layers of bracings. The sheet piles was 18.0 m long Type IV. The construction consists of two parts as single row of sheet pile wall double row of sheet pile walls or cofferdam. This research also studies the deflection behavior of diaphragm wall for construction of waste water treatment of 12.15 m depth by using 1.00 m thick and 28.2 m long diaphragm wall 3 bracing layers. The results of the measured horizontal displacement of steel sheet pile wall by Inclinometer indicated that the horizontal displacement cofferdam was about 50% less than the single row sheet pile wall. The shear strain levels of cofferdam in the soft clay and medium clay were about 0.22 0.30% and 0.21 0.39%, respectively while the shear strain of the single row sheet pile wall in the soft clay and medium clay were about 0.26 0.34% and 0.28 0.46%, respectively. The diaphragm wall was moved more than 50 mm, because of the lost of pressure on the first strutting system. The deflection behavior of diaphragm wall was significantly affected by the stiffness of bracing system. According to the strut force measured by pressure gauge, it found that force in the strut depended on the temperature changes by induce the axial stress of 57 ksc and 151 ksc for the sheet pile cofferdam and diaphragm wall, respectively. The results of back analysis by Finite Element Method (FEM) for determination of horizontal displacement of the sheet pile wall systems to compare with the measurement showed that at the final stage of excavation at -10.0 m to -12.5 m, the ratio of Youngs modulus (Eᵤ) to undrained shear strength (Sᵤ) of soft clay, medium clay and stiff clay were in the order of 150, 250, 1000 and 125, 200, 1000 for the cofferdam and the single row of sheet pile systems, respectively. The value of Youngs modulus for the diaphragm wall was in the order of 350 Sᵤ , 500 Sᵤ , 1000 Sᵤ for soft clay, medium stiff clay and stiff clay, respectively. For initial stage shallow excavation, the shear strain of the wall was less than at the final excavation stage. The Youngs Modulus of soil increases with non linear behavior depended on the shear strain of the wall.