はじめに

ニュージーランド北島の東海岸に位置するネイピア港は、同国中部地域の主要な輸出港です。24時間体制で稼働しています。同港のインフラ維持管理マネージャーであるClarke Curtis氏によると、2000年代の最初の10年間で、同港の貨物取扱量はおよそ2倍に増加しました。

挑戦

The growth of the port’s throughputs was accompanied by an increase in heavy forklift and shipping container operations (front-axle loads of 100 tones/110 US short tons), causing severe pavement ruts of up to 85 mm (3.3 in) in the wheel paths. These ruts required constant maintenance as the forklifts would shake when passing over them.

決議

In 2010, New Zealand-based road infrastructure contractor Higgins proposed the use of HiMA to solve the problem. The new 20-year design life solution called for 10 cm (4 in) of HiMA-modified SP28 asphalt concrete on top of cement-stabilized, 75 cm of crushed river gravel; followed by 5 cm (2 in) of SP12.5 asphalt concrete wearing course using PG64E-22 SBS bitumen. That same year, the solution was applied to 420 m2 (4,521 ft2) of the heavily rutted section. Later that year, an additional 2,700 m2 (29,062 ft2) was paved with HiMA at the port.

Nine years and an estimated 700,000 20-ft equivalent units later, the trial section shows no signs of structural distress. “Deformation is estimated at less than 5 mm (0.2 in), and no cracking has been observed,” says Sean Bearsley, Technical Innovation and Implementation Manager, Higgins.

Following its experience at the port, Higgins constructed additional HiMA pavements in New Zealand. They include state highways, municipal streets, and additional port facilities totaling approximately 110,000 m2 (1.2 million ft2) of pavement.