Abstract: It is of the unbonded type and comprises, from the inside outwards, an internal leakproof assembly comprising a pressure vault, a first inner group of tensile armor (5), a second outer group of tensile armor (7) and an external sealing sheath (8), the tensile armor of the said inner and outer groups being wound at a lay angle of less than 55.degree., characterized in that an intermediate sealing sheath (6) is inserted between the two inner (5) and outer (7), groups of tensile armor, the inner group of tensile armor (5) being wound with a short pitch and at a lay angle of greater than 35.degree. and less than 55.degree., and the outer group of tensile armor (7) being wound with a long pitch and with a lay angle of less than 30.degree..