Model tests and numerical simulation were conducted to study the effects of spandcan penetration and extraction on the motion behavior and lateral bearing capacity of adjacent suction caissons. Results indicate that during spudcan penetration

the suction caisson experiences a combination of rotational

horizontal

and vertical movements. The suction caisson moves horizontally away from the spandcan and vertically upwards during penetration

while it experiences horizontal movement away from the spandcan and vertical settlement during extraction. The maximum horizontal and vertical displacements of the suction caisson increase with increasing the spudcan penetration depth and spacing. In addition

the lateral bearing capacity of the suction caisson exhibits significant directional characteristics influenced by spandcan penetration and extraction. The lateral bearing capacity of the suction caisson after spandcan extraction varies in different directions as follows: along the direction of the line connecting the spandcan and the center of the suction caisson

toward the spandcan < away from the spandcan < perpendicular to the line connecting the spandcan and the suction caisson center. When the spacing between the spudcan and the suction caisson is 2.5 times the diameter of the suction caisson

the lateral bearing capacity in all directions remains unaffected. When the spandcan penetration and extraction area is behind the suction caisson loading direction

the soil deformation around suction caisson distributes symmetrically along the loading direction. When the spandcan penetration and extraction area is on both sides of the suction caisson loading direction

the soil deformation range no longer distributes symmetrically along the loading direction. The penetration and extraction of the spandcan reduces the range of the deformation of the soil under horizontal loading. Based on model tests and three-dimensional large deformation numerical simulation results

the impact of spudcan penetration and extraction on the lateral bearing capacity of suction caisson in different scales was studied. The correlation between model tests and prototype reality was established

enabling the test results to better guide engineering practice.