Tire crown for a heavy duty civil engineering vehicle

A tire for a heavy vehicle of construction plant type, comprising:

• a tread;
• and
• the tread, having a radial thickness HT at least equal to 60 mm, comprising:
• cuts having a radial depth HD and a width WD, and
• elements in relief separated by the cuts;
• at least some of the cuts, referred to as effective cuts, having a radial depth HD at least equal to 50% of the radial thickness HT and a width WD at most equal to 20% of the radial depth
• a crown reinforcement radially on the inside of the tread, the crown reinforcement comprising:
• a protective reinforcement:
• a working reinforcement;
• and
• a hoop reinforcement;
• the protective reinforcement, which is radially outermost, comprising:
• two protective layers, in contact with one another over a median axial width WC, wherein a radial spacing between the two protective layers, measured at a same axial position of each of two protective layers, is constant over the median axial width WC and increases beyond the median axial width WC,
• comprising elastic metallic reinforcers, that form an angle of between 15° and 45° with a circumferential direction,
• each said protective layer having a breaking strength R per unit of layer width, expressed in daN/m, Rmax being the maximum value of the breaking strengths R of the protective layers;
• the working reinforcement comprising at least two working layers, comprising inextensible metallic reinforcers that are crossed from one working layer to the next and form an angle of between 15° and 45° with the circumferential direction of the tire;
• and
• the hoop reinforcement comprising at least one hooping layer, comprising metallic reinforcers that form an angle at most equal to 15° with the circumferential direction,
• wherein the median degree of surface siping TLC of the tread, defined as the ratio between the cumulative length LDC of the effective cuts, present on a median portion of the tread having an axial width equal to WC, and a median area AC of the radially outer surface of the tread equal to 2ΠRE*WC, where RE is the external radius of the tire, is at least equal to 5 m/m2 and wherein the coupling ratio CC, defined as the ratio between the maximum value Rmax of the breaking strengths R of the protective layers and the median degree of surface siping TLC of the tread, is at least equal to 18 000 daN.