Abstract: Based on the settlement control of the immersed tube tunnel in Hong Kong-Zhuhai-Macao Bridge, eight groups of labortary model tests on length and diameter of piles, pile spacing and distance S₁ between isolation piles and settlement reducing piles are performed to study the isolation effects of isolation piles under large side loading in the island edge. The results show that the maximum axial force and bending moment of settlement-reducing piles decrease with the increasing length of isolation piles, meanwhile a sufficient length of isolation piles plays a significant role in diminishing the bending moment. The increasing diameter of isolation piles or the decreasing spacing of isolated piles can enhance the obstructing ability of vertical deformation and strengthen the soil arching effect. The maximum axial force and bending moment of settlement-reducing piles decrease with the increasing diameter or the decreasing pile spacing. At the same time, the isolation effects for the axial force and moment can be ignored when the pile spacing reaches 8D. The isolation effects for the axial force become better as distance S₁ decreases, however those for the moment are not significant due to the variation of distance S₁. The research achievements may provide a better reference for the application of isolation piles.