The Compaction Technique Of The Base Of A Road Roller
Road roller, also known as the compactor, is a kind of road repair equipment. Roller belongs to the category of road equipment in construction machinery, and is widely used in filling and compaction of large-scale engineering projects such as high-grade highways, railways, airport runways, DAMS and stadiums. Roller with the mechanical force of gravity, suitable for a variety of compaction operations, so that the rolled layer produces permanent deformation and compaction. So what are the compaction skills of road rollers?
(1) compaction of cement stabilized soil base
Cement stabilized soil refers to the mixture with certain compressive strength obtained after mixing, compacting and keeping in good health by adding a certain amount of cement and water into loose broken soil. For the road base with cement stabilized soil as paving material, the following matters should be paid attention to when rolling:
a.When the mixture is roughly paved on the road, it should be first rolled quickly with a tire roller or tractor, grader, and leveled.
b. After the shaping of the base, use the three-wheel smooth roller or heavy tire roller or vibratory roller with more than 12t to roll within the basic width. In the straight line segment, it should be rolled from the shoulders of both sides to the center of the road; In the curve segment, should be rolled from the medial shoulder to the lateral shoulder. When rolling, the overlapping width is 1/2 of the width of the rear wheel, and the side of the stable layer and the road shoulder should be pressed 2-3 times more. When the water content is more than 2%, it should be rolled more than 6 times, the first two times of rolling speed of 1.5-1.7km/h, the next several times of 2-2.5km/h. During the rolling process, it is not allowed to "turn around" or apply emergency braking on the section that has been completed or is being rolled, so as not to damage the base surface.
c. In the process of rolling to prevent the occurrence of "spring", loose and peeling phenomenon, when dry can be filled with a small amount of water.
d. In the later stage of rolling, should avoid excessive stress or rolling time, in order to prevent the reduction of the strength of cement stabilized soil. Finally, the "final pressure" should be used to improve the flatness of the base surface.
e. It is best to use a tyre roller for rolling, the machine weight is 10-20t, the tyre pressure is about 0.7mpa, the number of wheels is between 7-11.
f. When the stable soil is laid on the soft roadbed, it is better to choose the vibratory roller with medium and low linear pressure. When the compaction density increases, the paving material hardens and the roller produces a slight bounce, the amplitude should be reduced to avoid damage to the machine.
(2) the compacted lime stabilized soil of lime stabilized soil base refers to the mixture with certain compressive strength obtained after mixing, compacting and keeping in good health by adding an appropriate amount of lime and water into the loose crushed soil. For road base course or base course with lime stabilized soil as auxiliary material, the following matters should be paid attention to when rolling:
a. Check the water content of the mixture before rolling. The rolling effect is best when the water content is 1%-2%, when the water content is insufficient, water should be added with sprinkling, when the water content is too large, should be tanned.
b. After manual paving and shaping, first use a tractor, or 6-8t tandem roller, or tire roller rolling 1-2 times; Then, the static nimbus roller above 12t is used for rolling until the compactness of the mixture reaches 95-98%.
c. If lime stabilized soil is used as the base of advanced pavement, the content of water and lime should be accurate. When rolling, heavy static roller should not be used for many times, but should be used high efficiency vibratory roller, first disconnect the vibration source for static pressing, then step by step for vibratory compaction, and finally disconnect the vibratory source for static compaction.
(2) lime stabilized industrial waste slag base compacted lime stabilized industrial waste slag refers to the mixture obtained by mixing a certain amount of lime, fly ash (or cinder) with other aggregates (or no other aggregates), adding an appropriate amount of water and mixing, compaction and health maintenance. Because the compactness of the mixture has a great influence on the strength, it is advisable to use a heavy roller for rolling. Usually first with a medium roller initial pressure 3-4 times, then with a heavy roller continue rolling 6-8 times, until the required compactness.
(3) compacted gradation aggregate of grade-matched aggregate base refers to the mixture made of crushed stone, gravel or broken gravel according to particle size. For the base paved with this mixture, it is best to use a vibratory roller for compaction, can also be used more than 12t static light roller, or heavy tire roller, or vibratory roller and tire roller together.
(4) the compacted interstitial gravel base course refers to the road base course formed by stratified paving and stratified rolling of large, medium and small single-size gravel of different specifications. This kind of base should be laid in two steps: first lay large gravel and compaction; Small gravel is laid and finally compacted. For the first compaction, 8-10t static tandem roller or 5t vibrating roller should be used for fast rolling to vibrate all the filler materials into the pores of coarse gravel. The second time after laying small gravel, the vibratory roller continued to roll. When all the surface pores of gravel are filled up, the 12-15t static smooth roller is used for one to two times of final pressure until the surface is smooth and stable, no obvious wheel trace, and no rock creep phenomenon.