All about compaction of sand
Why and how is sand compaction performed? What are the ways to accomplish this task? How can you tamp it without a vibrating plate?
In order to carry out preparatory work for construction, a sand cushion can be formed by various methods. Their choice directly depends on what kind of tool is in the equipment, how large the working surface area, and also what are the requirements for the density of the sand substrate.
There are several methods of performing work associated with compaction of sand.
- Applied machine on an independent move, which uses its wheels to tamp the sand. Sometimes trailed-type special equipment is used, equipped with rollers for rolling, with the help of which layer-by-layer compaction is performed in several passes.
- With help lifting crane slabs weighing up to 2 tons are dropped onto the working platform.
- Sand can be compacted with a vibrating plate – a special mechanical device.
- With the help of a channel or a wide bar sand can be tamped without a vibrating plate, that is, manually.
The selection of mechanized methods for ramming bulk material depends on the convenience for the operation of specialized equipment, the availability of access roads for it and the thickness of the sand substrate required by the project. On large areas, work is carried out using self-propelled tractors, and small areas are processed by self-propelled rollers. If you need to compact the sand in a very small, confined space, a manual compaction may well be suitable for this case.
In order to efficiently tamp sandy bulk material, several passes are made using a tool on the same working surface, and the tamping movements are performed in a spiral direction – so you can be sure that there will be no untreated areas of the substrate surface. If, after compaction, the material has subsided greatly, it is possible to add sand to those areas where it is clearly not enough. For a denser compaction of sand particles, it is regularly poured with water, which helps to push air between the grains of sand.
Tamping is carried out by dropping monolithic heavy slabs if the pad consists of clay and sand of a dusty fraction. Such substrates contain air in their multiple cavities, which comes out to the surface under the weight of the monolith. The slab with the help of special equipment rises to a height of up to 2 meters and is dropped onto the working surface flat. This method allows you to work out the clay-sand mixture to a depth of 1.5-2 meters. Usually, this method is resorted to when the foundation is being prepared for the foundation of a capital structure.
The manual method of forming a sand layer is resorted to when the treated area is small, and the thickness of the sand layer is small. To solve this problem, the tool is made from scrap materials. They take a bar of wood, a wide base in the form of a wooden or steel plate is attached perpendicularly to it. The attachment points of the two parts are securely fixed using hardware fasteners or a weld. The result of the work should be a solid construction for manual labor. It has a lot of weight, but a person is able to lift it and perform frequent blows on the sand. To work more efficiently and faster, the horizontal plate is specially weighted with the help of additional metal plates or pouring from cement.
What is it and what is it for?
When building a house for a foundation or screed, it is necessary to make a hard layer in the form of a lining of sand or gravel with fine dispersion. The tamping technique allows to provide the necessary density to such a base. To compact bulk materials, specialized equipment is used, and if the coverage area is small, a manual method of work is used. A dense sand cushion is necessary before starting construction work for the following reasons:
- For complete leveling and increasing the degree of rigidity of the surface of the base of the future erected structure;
- To prevent the destruction of the foundation structure under the influence of moisture or low temperatures, when the soil begins to swell from excess water;
- To prevent distortion of the structure from the action of bending and compressive loads on it during soil shrinkage processes;
- With the aim of elimination of hidden voids, filled with air;
- For the construction of an intermediate stable layer, formed between the soil and the foundation structure.
The compacted sand creates a dense and durable layer, which is a reliable base for laying asphalt pavement, paving slabs, and building foundations. A properly formed sand layer is not subject to deformation and does not collapse if you step on it. Compaction technology implies performing these works in multiple passes over the entire surface of the sand layer.
All about compaction of sand
Before installing the foundation structures or preparatory work under the screed, as well as for laying paving slabs, it is necessary to tamp the sand cushion in order to expel the excess air volume from it, squeeze the fine fractions of sand grains together as tightly as possible. After compaction is completed, the sand base becomes very dense, ready for further construction work. To cope with this task, mechanized and manual methods of compacting bulk material are used.
Making manual ramming
There are many options for making a rammer with your own hands. Someone makes massive structures entirely of iron, but in this case, welding will be required. Others prefer to make do with the materials at hand. Consider the best option for making a manual rammer for compaction of soil, sand and gravel.
Helpful! Some people use round logs, but with the help of such rammers it is impossible to fully compact the base in the corners.
You will also need to prepare:
- A steel plate with a minimum thickness of 2 mm.
- A round stick about 450 mm long (it will act as a handle for the future rammer). To do this, you can use an unnecessary shovel handle.
- Wood screws and wood glue.
We make a "shoe"
The next step in creating a tamping tool with your own hands is making a metal "shoe" from a sheet of steel. We use the following template to cut the plate.
Or, you can simply install the timber with its lower end on a sheet of metal and circle it with a pencil.
After that it is necessary:
- Cut the workpiece, as in the picture, using special metal scissors or using an angle grinder.
- Remove metal burrs from the "shoe". To do this, it is most convenient to clamp the workpiece in a vice and remove the excess with a file.
- Without removing the "shoe" from the vice, drill holes for the screws at the previously marked points.
- Sand the surface with sandpaper.
- Bend the "wings" of the workpiece and install the bar in the "shoe". If the workpiece turned out to be a little wider, it is necessary to knock out the “wings” with a hammer.
- Place the drill bit in the screw holes and drill the wood with a slight slope.
- Fix screws on all sides.
When preparing the base for foundations and backfilling the sinuses, the soil must be compacted. Without compaction, the soil in the sinuses of the foundation will settle by itself over time, and a void forms under the blind area, or the blind area will also sag. And under the foundations of the foundation, soil compaction is necessary in order to increase the provision of a high bearing capacity of the soil and also avoid shrinkage.
The criterion for assessing the quality of compaction is the coefficient of compaction of the soil or directly the density of the soil. The mobility of soil particles depends on its moisture content, therefore the quality and speed of compaction depends on the moisture content of the soil. The optimum moisture content for each soil is shown in the table:
|Priming|| Optimum humidity,%|
If the soil is too dry, then it needs to be moistened for faster compaction: moisture allows particles to more easily change their position in the soil. If this is not possible, then it is necessary to reduce the layer thickness during layer-by-layer compaction in order to achieve the same quality. Waterlogged soil must be dried: most of the pores in it are occupied not by air but by water, and this will interfere with compaction.
When preparing a sand cushion for a foundation or backfilling the sinuses, the soil must be covered with small layers, compacted layer by layer and the next layer must be covered. The thickness of one layer depends on the soil and the compaction method. When using heavy rollers, the layer can be 50-70 cm, but for self-construction, when a manual rammer or vibrating plate is used, the layer should be no more than 10-15 cm.
Soil compaction methods
There are three main methods of soil compaction: rolling, vibrating and compaction. Some devices. Vibratory rollers. Combine rolling and vibration.
Compaction of soil with a hand roller.
The rolling method consists in the fact that a roller with a large mass repeatedly passes over the surface of the soil and compaction occurs under its pressure. The thickness of the compacted layer depends on the mass of the roller, when using a hand roller it is a maximum of 10-15 cm for sand and 8-10 cm for clay. A conventional roller has a smooth surface and can roll any soil. The cam roller has compact cams on the surface, which can be of various shapes. These rollers are used to compact clayey soils. In order to roll the soil well enough, you need to drive it with a roller from 8 to 16 times.
Vibration method. It is a good method for sandy soils and is based on creating vibration that is transmitted from one grain of sand to another, thereby setting them in motion. If you pour a full jar of sugar, and then shake it, then space becomes free in it, because the sugar particles have settled down, more densely settled in space. In the same way, sand is compacted by vibration. In clay, vibration is poorly transmitted, so it is difficult to compact it by vibration. For compaction by this method, vibratory plates, vibratory rammers are used, and vibratory rollers combine the methods of rolling and tamping, due to this, they accelerate the compaction. The vibrating plate spontaneously moves forward during operation; to compact the soil, you need to walk it 6-8 times.
Soil compaction with a vibrating plate.
The tamping method consists in throwing a tamping plate onto the surface of the soil. Its weight can reach several tons, and its dimensions. Several meters. For self-construction, this is the most technologically simple and affordable method: you can use a manual rammer, including homemade ones. From logs or boards.
Soil compaction coefficient. It is a dimensionless indicator calculated as the ratio of the density of the soil to its maximum density and shows how well the soil is compacted.
Density meters. These are special construction devices, with the help of which it is possible to measure the density of the soil and estimate its bearing capacity right on the construction site.
This article will focus on backfilling the foundation and the main questions: what kind of soil can be used for backfilling. Clay or sand?
The bearing capacity of soils is its basic characteristic, which you need to know when building a house, it shows how much load a unit of soil area can withstand. The bearing capacity determines what the supporting area of the foundation of the house should be: the worse the ability of the soil to withstand the load, the larger the area of the foundation should be.