Foundation, Concrete and Earthquake Engineering

Requirements of Sheath for Micropile Encapsulation

We know sheath is used for encapsulation purposes; the encapsulation is required for aggressive exposure of micropile, especially when subjected to tension loading.

Sheath is essential part of corrosion protection process for unbounded length, later we will discuss about encapsulation of bond length. Sheath may be smooth or corrugated.

Sheath for Micropile Encapsulation

Smooth sheath can also be used as bond breaker as discussed in last post. When sleeves are used that may shrink with temperature change or sheaths of corrugated tube are used, separated bond breaker has to be used. We have discussed about requirements of bond breaker in last post.

Sheaths fabricated by following materials were found to have satisfactory performance:

  • A tube made of hot-melted extruded polyethylene comply ASTM D1248,Type III

  • A tube made of hot-melted extruded polyethylene comply PP210B55542-II,as per ASTM D4101

  •  A corrugated tube satisfy requirements of encapsulation of bond length

These are the specifications according to which sheathing material is selected. The required properties for sheathing material are as following:

• Should have resistance against chemical attack; the aggressive environment, corrosion inhibition or grout are considered to produce chemical attack.

• Should have resistance against aging from UV-light

• Not harmful to any type of reinforcement

• Should have ability to withstand

 Impact 
 Abrasion
 Bending while handling & installation

• Allow reinforcement enclosed by sheathing to elongate under stressing and testing.

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