To provide a rubber expansion tube, which can be used for a geological survey, and has a large expansion capacity in the radial direction and a large scratch resistance.

The rubber expansion tube 16 expands in the radial direction by the pressure of the fluid introduced therein. An inner reinforcing layer 34 and an outer reinforcing layer 36 are provided inside the region between an inner rubber layer 30 and an outer rubber layer 32. The outer reinforcing layer 36 is a longitudinal reinforcing string layer having reinforcing strings 38 which elongate substantially in parallel with the tube axis. The inner reinforcing layer 34 is a layer having reinforcing strings 40 which cross the longitudinal reinforcing strings of the outer reinforcing layer 36 making an acute angle of 10°. These inner reinforcing layer 34 and outer reinforcing layer 36 form a network structure.

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