A tubular sheath member is fitted over the pile surface, having a length longer than the thickness of an active or seasonally frozen soil layer of the terrain in which the pile is installed. At least a portion of this length is defined by a series of ribs extending transversely outwardly of the sheath member relative to a lengthwise axial line as an extensible section. The lower end of the sheath member is secured to the pile at or below a position corresponding to the bottom region of the active or seasonally frozen soil layer. The upper end of the sheath member is secured to the pile at a position above the ground surface and a fluid material is filled in a space defined between the pile and the sheath member.
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