Heavy goods vehicle tyre , comprising beads designed to make contact with a mounting rim, these beads being prolonged radially outwards by sidewalls which are themselves joined to either side of a crown portion, this crown portion being covered radially on the outside by a tread having a total thickness of material to be worn which determines a wear limit, and having a tread surface for making contact with a roadway, this tread comprising at least two cut-outs of generally circumferential orientation, the two circumferential cut-outs which are spaced farthest from one another axially delimiting in the tread a central region and two edge regions , the central portion having a width Lc of between 35% and 70% of the total width W of the tread , this tyre comprising a carcass reinforcement anchored in the beads and extending into the sidewalls and into the crown portion, the crown portion of the tyre comprising a crown reinforcement radially outside the carcass reinforcement, the crown reinforcement comprising at least two working layers having reinforcing elements orientated parallel to one another in the same layer, these reinforcing elements being cords consisting of UHT-grade threads, that is to say threads having a mechanical breaking strength R satisfying the following relation: R ≥ 4180 - 2130xD, where R is expressed in megaPascals (MPa) and D is the diameter of the thread expressed in millimetres, this tread being formed of at least two layers of material superimposed in the radial direction, namely a first layer and a second layer , the first layer being radially nearer to the crown reinforcement than the second layer , this tread being characterized in that : - the material forming the first layer is chosen to have a breaking elongation of more than 600% at a temperature of 60°C, - in the central portion of the tread radially surmounting the crown reinforcement and delimited axially by the axially outermost cut-outs , a cavity ratio per unit volume as new is defined between the tread surface and a surface parallel to the tread surface and passing through the innermost points of the cut-outs, this cavity ratio per unit volume being not more than 10%, and in that - in this central portion of the tread , the surface cavity ratio as new and over any surface to a depth equal to at least 50% of the thickness to be worn is not more than 10%. - the material forming the first layer is chosen to have a breaking elongation of more than 600% at a temperature of 60°C, - in the central portion of the tread radially surmounting the crown reinforcement and delimited axially by the axially outermost cut-outs , a cavity ratio per unit volume as new is defined between the tread surface and a surface parallel to the tread surface and passing through the innermost points of the cut-outs, this cavity ratio per unit volume being not more than 10%, and in that - in this central portion of the tread , the surface cavity ratio as new and over any surface to a depth equal to at least 50% of the thickness to be worn is not more than 10%. - in this central portion of the tread , the surface cavity ratio as new and over any surface to a depth equal to at least 50% of the thickness to be worn is not more than 10%. <EOS>