Shaanxi Province

Shaanxi is considered one of the cradles of Chinese civilization. Thirteen feudal dynasties established their capitals in the province during a span of more than 1,100 years, from the Zhou Dynasty to the Tang Dynasty. The province's principal city and current capital, Xi'an, is one of the four great ancient capitals of China and is the eastern terminus of the Silk Road, which leads to Europe, Arabia and Africa. Xi’an is also known the world over as the home of the famous Terracotta Army of Qin Shi Huang, the First Emperor of China. The terracotta figures, dating from 210 BCE, were discovered in 1974 by several local farmers near Xi'an. Current estimates are that in the three pits containing the Terracotta Army there were over 8,000 soldiers, 130 chariots with 520 horses and 150 cavalry horses, the majority of which are still buried in the pits. The Army is often called the Eighth Wonder of the World and has been included by UNESCO in its World Heritage List.

A total area of 2,000 sqm had to be milled. Each single spot is not larger than approximately 72 sqm.

Fine milling is a modification of the standard cold milling method, the difference being that the cutting tools on the drum are arranged at much narrower intervals. One speaks of fine milling when the tool spacing is 8 mm or less. These special milling drums are fitted with a much larger number of cutting tools than standard milling drums. This method is very often used for the rehabilitation of asphalt surfaces. The goal of fine milling is to produce a new, precisely defined surface texture. Even though fine milling drums are not capable of eliminating damages that are located deep within the pavement structure, they can produce an even pavement surface with excellent grip. After installing a fine milling drum in the milling drum housing, the cold milling machine cuts grooves into the pavement at intervals of between 8 mm and 3 mm and at a maximum depth of 50mm, producing a fine surface texture in just one machine pass. Additional work steps, such as paving a new surface layer, are usually not required but if fine milling is used on a binder course to eliminate bumps, the wearing course can be paved to a high-class evenness.

The evenes

After milling: the typical fine-milled profile is skid-resistant, with rough valleys ensuring optimum interlocking of the next layer. Result: a strong and even bond between layers as proof of quality.

The reclaimed asphalt

The reclaimed asphalt material comes in sizes of up to 12 mm.

The Wirtgen FB 2000, 6x2 mm fine milling drum equipped with 672 pcs. cutting tools type W 5 EH.

The machine

It goes without saying that a high-quality result also requires machinery which fits the bill for the job in hand. The cold milling machines of type W 2000 used in the three projects outlined above were equipped with fine milling drums which produced a profile with optimum intermeshing structure for placement of the new pavement. The special milling drums are produced in this precise version and high quality by the market leader Wirtgen in a unique manufacturing process at its plant in Windhagen. The optimum tool system with high-grade point attack tools and tool holders for equipping the milling drums are a important factor for the final result. The Wirtgen W 2000 is a powerful, compact cold milling machine mounted on crawler tracks for the removal of individual pavement layers or complete carriageway structures at depths of up to 32 cm in one single pass on a width of 2 m. The machine's powerful engine, large tracks and generously dimensioned conveyor system ensure high daily production rates.

LEVEL PRO

Wirtgen has also developed a highly accurate, proprietary leveling system including software that has been designed specifically for cold milling machines: LEVEL PRO. The overall system includes an operating panel, a controller unit and several sensors. The graphics-enabled LEVEL PRO screen shows key parameters in a clearly legible fashion. For example, target and actual values for the left and right milling depth and slope parameters are clearly shown on the displays. In addition, the memory feature isvery useful to program, store and invoke target values.

As the milling areas lie diagonally to the lanes, a high degree of maneuverability is a must. This is when the operator can rely on the excellent driving properties of the compact W 2000. This is ensured by the smooth, hydraulic all-track steering system including a manually selectable, hydraulic flow divider which acts as a differential lock and guarantees a uniform tractive force even under adverse conditions. The high-lift, individually height-adjustable track units result in a remarkably high ground clearance. In addition, all four units provide large steering angles, which allow the W 2000 to perform an amazinglysmall turning circle.

The team

Mr. Wang Meng and Mr. Zhao Bin and Mr. Du Guihai from BCHD
Mr. Yu and Mr. Li from CRCC 2nd Bureau 3rd Branch