Column foundation technology:
- After the site is cleared, its layout is produced. Mark the site with the help of pegs and twine, pulling it around the perimeter of the walls of the building. The foundation pillars are installed in the corners of the building, at the intersection of the bearing walls, with additional length of the building, additional posts along the external walls are also installed.
The process of marking the area with pegs and threads
- The column foundation is made of concrete blocks or bricks. Deepen the trench under the pillars of the foundation for 30-40 cm, perform a pouring of crushed stone to exclude capillary suction of moisture from the ground. On the rubble roll coiled waterproofing: ruberoid, polymer films.
- The laying of foundation pillars is performed with a bandage of rows, the number of blocks or bricks in a row depends on the size of the posts and the thickness of the walls. The methods of laying are shown in the figure.
Methods of laying foundation pillars
- After laying the pillars of the foundation are waterproofed with bitumen or polymer mastic, a roll of waterproofing is laid on top of them, after which you can start building the walls.
Foundation bottom process
Foundation on fine silty sand
Fine silty sands are difficult to construct, especially if they are built in wet areas with closely spaced groundwater. Before the beginning of construction on such a soil, it is necessary to conduct a geodetic survey of the site, as well as to calculate the foundation of small deposits.
When constructing a shallow belt foundation on dusty sand and sandy loam, it is necessary to take measures that reduce the load of frost heave forces on the base. The forces of frost heaving act on the foundation from below, exerting pressure on the sole, and on the tangent to its walls. To reduce the impact of ejection forces, it is necessary to increase the footprint of the basement, that is, to make it trapezoid or with an extension downwards. To avoid deformations from the impact of the tangential load, roll-up waterproofing of the foundation walls is used - the roll materials prevent the adhering of the frozen ground on the foundation, ensure its slip. In addition, a good measure of combating frost gum is the warming of the foundation.
If, as a result of a geodetic survey, closely located weak soils, for example, quicksand, are found, then the strip foundation must be reinforced with piles buried to a stable soil, and for the resistance of the foundation, the pushing forces at the bottom of the piles should be expanded.
Technique for making a pile foundation on fine-grained sands:
- Site preparation includes clearing, removal of the fertile layer, marking and preparation of the excavation. The pit on the sandy soil often falls, so it is permissible to dig it with a slope of the walls of the foundation pit at 45 degrees, and build a timbering in its entire height. Formwork is made of boards or shields, reinforced with screeds and struts. In the corners, at the intersection of the foundation tape, and also every 2 meters of the wall, bore holes under the piles to the depth of occurrence of stable soils.
Drilling process for
- pouring In case of detection of a floating pile, it is necessary to perform using asbestos-cement pipes. Pipes are inserted into the well and leveled to the level, fixed by spacers. The height of the pipes should be such that they are exposed above the bottom of the trench. If the soil is not very wet, and it is possible to make a well without filling it with water, the pile can be made concrete with reinforcement.
Foundation reinforcement process
- Pouring piles. Filling the pipe with concrete for 1/3, slightly lift it in the well, allowing the concrete to fill the bottom of the well. This results in a thickening in the lower part of the pile. Align the pipe, insert the prepared reinforcement and allow the concrete to solidify. The reinforcement for the piles is three to four bars, connected together by wire or cross-bars. The height of the reinforcement should allow it to be connected to the horizontal reinforcement belts of the foundation ribbon. After installing the reinforcement, pour the pipe with concrete to the upper level.
Internal view of the well after casting concrete
- The bottom of the trench is covered with coarse sand or small gravel and covered with a layer of roll waterproofing. The reinforcement for the pile-and-tape foundation is made from a corrugated rod in two horizontal belts located at the top and bottom of the belt. The binding of horizontal reinforcing bars with vertical wires is produced. Welding them is undesirable, because corrosion-unstable areas are formed in the welding places.
Create formwork under before filling
- Pour the concrete with either one-time or layer-by-layer filling. Vertical joints on the tape should not be, they reduce the bearing capacity. Concrete after pouring is leveled, covered with a film from atmospheric precipitation and left for three to four weeks to mature the concrete.
- After the foundation is dried, it is necessary to make a vertical waterproofing of the foundation using roll materials - this will save the foundation from tangential loads. On wet soils, drainage is mandatory, and in regions with severe winters - foundation warming using plate materials or polyurethane foam. Reverse the backfill, then perform a blind.
If quicksand located at the level of ground water is found in the area with sandy fine-grained soil, it is also possible to use the technology of erecting a foundation on quicksand using metal screw piles.
To determine which foundation is suitable for sandy soil, it is necessary to carefully examine the soil itself. Sand, as you know, can have a different particle size: from large, to a millimeter, to very small, more like dust.
Coarse-grained sand is an excellent base for any type of foundation, it perfectly discharges water, practically does not subject to frost whipping, is resistant to seasonal movements. Sand with a small particle size is a dry dust, and when moist it does not let water pass like a large one, but absorbs and retains it. Dirt forms, which when frozen due to the high water content greatly increases in size. Therefore, fine-grained silty sands are very susceptible to frost heaving, and when calculating the foundation, this must be taken into account.
Foundation of the foundation on sandy ground
The second factor complicating construction on fine-grained sands and sandy loams is their propensity to form quicksand in areas with a close location of groundwater. Before the beginning of construction it is necessary to order a geodesic survey of the ground from specialists specializing in this company, otherwise the costs of correcting mistakes may exceed the cost of the foundation itself.
Foundation on coarse-grained sand
Tape and columnar foundations on coarse-grained sand with a groundwater level deeper than 2 meters are usually not particularly difficult.
It is necessary to level the pad and clean it of debris and remove the top fertile soil layer. After that it is possible to erect on fine coarse sand fine-grained ribbon foundation from monolithic concrete or concrete blocks for brick buildings or buildings with a basement floor. If the building without a basement, light and small - a wooden house, bathhouse, frame structure - it is enough to put a columnar foundation of blocks or bricks.
