The pillow for the base performs two functions: strengthens and levels soil at the bottom of trench (or ditch) and will amortize soil motions. If when dredging at the necessary depth there is binding gravel, the device of pillow is not required. In all other cases it is necessary.
It is required to you
- - pit sand
- - gravel of average fraction
- - M400 cement
- - water
Instruction
1. There are several types of pillows: sandy, gravel (crushed-stone), sand-gravel, concrete. The first often call "floating" as the big layer of sand allows the base to remain motionless at influence of forces of rebound of soil. Thickness of sandy pillow for the melkozaglublenny base is 5-10 cm, "floating" - 40-50 cm.
2. Dumping of sand is made as follows: at first the bottom of trench or ditch level by means of hydrolevel, then stamp. For this purpose use vibrating plates or self-made devices in the form of bar with the wooden bar strengthened in its lower part forming site for consolidation of the soil. Sand is filled up layer-by-layer, on 5-7 cm. Then it is leveled, spilled water from hose and carefully stamped watching that the horizontal was maintained. Only the pit sand is suitable for the device of sandy pillow. Optimum granularity – average.
3. Gravel pillow – often used option. For its forming use stones of average fraction: 20/40 mm. The pillow consists of 5-10 cm of compacted sand and 20-25 cm of gravel or crushed stone. Total height of dumping has to be 30 cm. Crushed stone, as well as sand, put in ditch layer-by-layer. Stones stamp the vibrating plate. It is not required to spill them water. After consolidation of each layer by means of hydrolevel check correctness of forming of pillow.
4. It is a little more difficult to build concrete pad (otherwise it is called concrete preparation under the base). Its main objective is not to allow drawdown of soil and to provide to the basis stability. Begin work, as well as in the previous cases, with alignment of bottom of trench or ditch. Then make dumping of gravel or crushed stone. Layer thickness - 5-10 cm. Further, stones need to be stamped carefully.
5. Further, start preparation of lean concrete. It represents cement and sand solution and has M75 brand. Thickness of concreting has to be such that completely covered binding gravel. The following components will be necessary for preparation of lean concrete: 25 kg of cement, 344 kg of the sifted pit sand, 10-11 l of water. Solution is filled in on gravel pillow.
6. For the melkozaglublenny bases it is possible to make such concrete preparation: to fill thin layer sand, then – cement layer. These components need to be mixed rake before receiving homogeneous mass. Then on it pour out small amount of water, again mix and level. Upon completion of works the concrete pad is covered with dense polyethylene which will prevent its drying.