Methane hydrate in submarine sediment works as a cementing material that bonds solid grains

and makes the sediment stronger.Once the hydrate dissociates

it will cause the reduction of shear strength in sediment.If the pile foundation is laid in the hydrate layer or near it

the stability will be affected. In this paper

the stress release method is used to study the strain and stress properties of pile foundation caused by the hydrate dissociation when the pile is laid in differert layers.The results show that the horizontal and vertical displacements will increase with the modulus softening and strength reduction after hydrate dissociation.Because the ground is horizontal and there is no shearing strength

the horizontal displacement is small.There is mainly vertical displacement in the ground and pile foundation.As the pile bearing capacity changes differently

the vertial settlement of pile in the middle of the hydrate layer is larger than that through the hydrate layer.The stress increases greatly in the pile foundation and around the soil.