torstai 24. maaliskuuta 2016

Tien kunnostus höylällä - Road repair to grader

Tiehöylä eli tiekarhu, joskus myös maantiekarhu, on maanteiden hoitoon ja rakentamiseen tarkoitettu järeä työkone, jolla on tarkoitus ensisijaisesti tasoittaa ja muotoilla tien rakennekerrosten pintoja tai sorateiden pintaa. 
                            Veekmas FG 2428 / Engine Cummins QSL8.9 / 216 kW

Tiehöylässä voidaan käyttää yhdestä kolmeen terää. Mahdolliset terien paikat ovat etupyörien edessä, etu- ja takapyörien välissä ja takapyörien takana. Useimmin höylässä käytetään vain yhtä, etu- ja takapyörien välissä olevaa terää, jonka korkeustasoa ja kaltevuutta voidaan säädellä hydrauliikan avulla.


Tiehöylän terän säätelyä on helpotettu 3D-koneohjausta kehittämällä. Tällaiset 3D-ohjatut tiehöylät ovat yleistyneet varsinkin Ruotsissa ja Norjassa 2000-luvulla. Perusperiaatteena 3D-koneohjauksessa on se, että joko robottitakymetrillä tai RTK-GPS:llä paikannetaan tiehöylä ja tiehöylän on-board tietokoneeseen kytketyt kallistusantureiden avulla paikannetaan terän asento. On-Board-tietokoneeseen on syötetty rakennettavan tierakenteen koneohjausmalli, jolloin tietokone tietää missä asennossa terän pitäisi olla kullakin hetkellä. Ohjaajan työksi jää periaatteessa vain tiehöylän ohjaaminen ja kaasun painaminen.
Gravel roads require much more frequent maintenance than paved roads, especially after wet periods and when accommodating increased traffic. Wheel motion shoves material to the outside (as well as in-between travelled lanes), leading to rutting, reduced water-runoff, and eventual road destruction if unchecked. As long as the process is interrupted early enough, simple re-grading is sufficient, with material being pushed back into shape.
Segments of gravel roads on grades also rut easily as a result of flowing water. When grading or building the road, waterbars are used to direct water off the road. As an alternative method, humps can be formed in the gravel along the road to impede water flow, thereby reducing rutting.

Another problem with gravel roads is washboarding — the formation of corrugations across the surface at right angles to the direction of travel. They can become severe enough to cause vibration in vehicles so that bolts loosen or cracks form in components. Grading removes the corrugations, and reconstruction with careful choice of good quality gravel can help prevent them reforming. Additionally, installing a cellular confinement system will prevent the washboard-like corrugations from occurring.

Gravel roads are often found in cold climates because they are less vulnerable to freeze / thaw damage than asphalt roads. The inferior surface of gravel is not an issue if the road is covered by snow and ice for extended periods.

Although well-constructed and graded gravel roads are suitable for speeds of 100 km/h (60 mph), driving on them requires far more attention to variations of the surface and it is easier to lose control than on a paved road. In addition to potholes, ruts and loose stony or sandy ridges at the edges or in the middle of the road, problems associated with driving on gravel roads include:

- sharper and larger stones cutting and puncturing tires, or being thrown up by 
  the wheels and damaging the underside, especially puncturing the fuel tank 
  of unmodified cars
- stones skipping up hitting the car body, lights or windshields 
  when two vehicles pass at high speed
- dust thrown up from a passing vehicle reducing visibility
- washboard' corrugations cause loss of control or damage to vehicles 
   due to excessive vibration
- skidding on mud after rain
- vehicle fishtailing as a result of ruts in the surface of the gravel
- In higher rainfall areas, the increased camber required to drain water, 
  and open drainage ditches at the sides of the road, often cause vehicles 
  with a high centre of gravity, such as trucks and off-road vehicles, to overturn 
  if they do not keep close to the crown of the road
- Tire wear increases by 40–50% on gravel roads
- Excess dust permeates door-opening rubber moulding breaking the seal
- Lost binder in the form of road dust, when mixed with rain, 
  will wear away the painted surfaces of vehicles
- Many gravel roads are only one lane wide or slightly larger, 
  thus requiring special attention when driving at higher speeds

                            Grader Vammas RG6V + Kubota 5700 tractor

                                                  Gehl MG 747 

                                                Laser Grader 106DW-P

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