道路施工设备(英文材料)

Paving Equipment Stabilizers/Reclaimers A stabilizer/reclaimer is a vehicle with a dual purpose. These machines have a large rotor blade which may be used to cut and pulverize damaged or old pavement, but which also may be used to mix lime, fly ash, or cement into the subbase in order to stabilize poor soils. Milling Machines A top layer is milled off the existing pavement to provide a relatively smooth surface on which to pave. Milling is also commonly used to remove a distressed surface layer from an existing pavement. Milling machines are the primary method for removing old HMA pavement surface material prior to overlay. They can be fitted with automatic grade control to restore both longitudinal and transverse grade and can remove most existing pavement distortions. Milling also produces a rough, grooved surface, which will increase the existing pavement’s surface area when compared to an ungrooved surface. The surface area increase is dependent on the type, number, condition and spacing of cutting drum teeth but is typically in the range of 20 to 30 percent, which requires a corresponding increase in tack coat (20 to 30 percent more) when compared to an unmilled surface. Milling is advantageous because it: l Provides RAP for recycling operations. l Efficiently removes deteriorated pavement that is unsuitable for retention in the overlaid pavement. l Provides a highly skid resistant surface suitable for temporary use by traffic until the final surface can be placed. l Allows curb and gutter lines to be maintained or reestablished before HMA overlays. l Provides an efficient removal technique for material near overhead structures in order to maintain clearances for bridge structures, traffic signals and overhead utilities. Figure 1: Side view of milling machine. Figure 2: Cutting tips on rotary drum.     Graders Graders may be used in place of milling machines if the base course is dirt or gravel. They are vehicles with large blades that create a wide flat surface for asphalt to be placed on. Figure 3: A grader preparing the subgrade on a project on SR 528 in Marysville, WA. Sweepers Sweepers clean the surface of the road after it has been milled or graded. This is necessary because excessive dust and debris on the ground can prevent proper bonding between the asphalt and the base course. Large pieces of debris can also cause non-uniform compaction of the asphalt. Figure 4: Sweeping machine. Batch Plant Batch plants, which produce HMA in individual batches, are the older of the two types of HMA production facilities; it was not until the 1970s that drum plants became a popular HMA production option. Typical batch quantities range from 1.5 to 5 tons of HMA and each batch can take 15 – 45 seconds to make. Figure 5: Batch plant Drum Plant Drum plants, which produce HMA in a continuous manner, generally offer higher production rates than batch plants for comparable cost. Typical production rates for drum plants vary between about 100 tons/hr up to over 900 tons/hr depending upon drum design. Figure 6: A continuous or drum plant. Dump Trucks Dump trucks move the hot asphalt from the plant to the jobsite. There are many kinds of dump trucks: l End dump: unload their payload by raising the front end and letting the payload slide down the bottom of the bed and out the back through a tailgate. They are the most popular transport vehicle type because they are plentiful, maneuverable and versatile. l Bottom or belly dump: Bottom dump trucks unload their payload by opening gates on the bottom of the bed. Internal bed walls are sloped to direct the entire payload out through the opened gates. Discharge rates can be controlled by the degree of gate opening and the discharge is usually placed in an elongated pile, called a windrow, in front of the paver by driving the truck forward during discharge. Windrows require a special MTV (material transfer vehicle) to feed the HMA into the paver. l Live bottom or flo-boy: Live bottom dump trucks have a conveyor system at the bottom of their bed to unload their payload. HMA is discharged out the back of the bed without raising the bed. Live bottom trucks are more expensive to use and maintain because of the conveyor system but they also can reduce segregation problems and can eliminate some detrimental types of truck bed – paver contact (because the bed is not raised during discharge). Figure 7: End dump truck placing WMA into a skip. Material Transfer Vehicles Material transfer vehicles (MTVs) are used to assist the paver in accepting HMA. Most pavers are equipped to receive HMA directly from end dump or live bottom trucks, however in certain situations it can be necessary or advantageous to use an MTV. Paving using bottom dump trucks and windrows requires a windrow elevator MTV, while other MTVs are used to provide additional surge volume, which is advantageous because it allows the paver to operate continuously without stopping, minimizes truck waiting time at the paving site and may minimize aggregate segregation and temperature differentials.