Loosening the soil of the base due to the removal of its smallest particles with fluid or groundwater or with intense drainage. The removal of the smallest particles of the soil, which is especially intensively with a significant drainage of both directly from the pit and with the help of tubular wells with filters of insufficient frequency, weakens the bearing capacity of the base. If the ground is taken for a long period of time, then damage to other structures located nearby are possible.
At the end of the construction of a stone four -story building, erected near the gateway canal, cracks were found in the middle part of the building from the front facade and a number of hair cracks from the inside of the building. Even before starting construction work, with a pink and drilling, it was found that a powerful layer of bulk soil with a fall of sandy aquifers located under it lies to a depth of 5 – 6.5 m towards a depth of 5 – 6.5 m. According to the stories of the old -timers, at the site of the built -up site, there was a backwater, then turned into a pond, subsequently falling asleep. Given this, the foundation under the body made of a boot on a concrete pillow was laid at a depth of 4.5 – 5 m on the basis of river sand in places with an admixture of cartilage, allowing pressure and soil at 2.4. The first OIL case is almost completed when they began to Rytyo pits for the second building. The soil at the base of the latter was partially the same nature as under the first case, partially consisted of small sand with an admixture of silt, saturated with water, which passed into larger sand with an admixture of cartilage.
The foundation for the second case was laid at a depth of B – 6.5 m in the form of lamp pillars on a concrete pillow. Since groundwater stood above the design mark of the sole of the foundation of 1.5 m, the ducking of the pit was made with a drainage. In addition, for the sewage device, ditches were dug along both buildings. As a result of the described method of work, both in the first building and in two neighboring houses, cracks were discovered, the formation of which was caused by the following reasons:
1. The layout of the soil indicates the existence of an underground flow going towards the channel according to the old -river, which existed before backfilling, which contributed to the movement of soil particles at the base of the first building.
2. Digging a foundation pit for the second building, produced with drainage at a time when the first building was already erected almost to the full height, caused the flow of the smallest particles of the soil from the foundation of the first building and contributed to a further violation of equilibrium at its basis.
3. Leaching of soil particles from the base intensified even more when it was started to dig ditches for sewage, as they acted like drainage that sucks water from the base along with the smallest particles of soil.
4. The fact that during digging the pit under the foundation of the first case, the water in the channel was lowered, and at the beginning of the summer again, it contributed to the saturation of soil water at the base and a decrease in its bearing capacity.