Techkart (TTK) for reinforcement with bored piles

Bored piles in unstable soils:

Construction of piles in unstable and watered soils, drilling of wells and their widening, as well as concreting are carried out under the protection of clay mortar or inventory casing pipes.

The clay thixotropic solution, having a density (greater than the density of water, creates an excess pressure at any depth and thereby retains soil particles on the surface of the walls of the well. In addition, the particles of the solution fix the walls, forming a small but stable crust (the phenomenon of so-called soil colmation). Grateful for these properties, the clay solution prevents the walls of the well from collapsing. During circulation, the solution carries loose rocks from the well to the surface.

Process diagram of drilling piles arrangement under clay solution protection includes operations of drilling and widening of wells, reinforcement and concreting of piles.

The clay farm consists of an clay stirrer for preparing a solution, a mud pump 11GR or 1EGR, sumps for pure and spent clay solution and a system of solution discharge trenches. To prepare the solution, mono- or two-shaft clay mixers with a volume of 0.75m3 are used. Sumpfs are placed behind the building spot until the work is completed. If it is impossible to take the sumpfs by the spot of the building, they are temporarily placed within its limits. To prevent contamination of the construction site, a trench must be dug up before work on the perimeter of the pit, in which wooden troughs with a size of 0.4x0.4 m are laid with a slope towards the sump 1:100. The same trough is fed from each pile bush to the main trough. When organizing a clay farm, it is necessary to have a transport with containers for the removal of spent solution, to identify transport routes and to determine the places of its discharge.

The clay solution is a stable physicochemical mixture of water and clay - suspension - with a density in the range of 1.181.22 g/cm3 and a daily sludge of 0-5%. Sand content in clay shall not exceed 10%. Clay solutions are prepared directly at the work site in the clay mixer MMZ0.75. One mixture is prepared during 1525 minutes. 0.250.35t of clay is consumed for preparation of 1m3 solution depending on the given density of the solution. To ensure normal operation, a clay solution must be prepared for at least two volumes of the well.

During drilling, the clay solution is contaminated with drilled soil (sludge). To reuse the solution, it must be cleaned. The most simple cleaning is carried out in a system of troughs with a sediment in the sump, which is periodically cleaned from settled sludge. Mechanical cleaning of the solution in a self-rotating separator, on vibration screens or in sitohydrocyclone plants is more effective.

Fine bentonite clays are used to prepare high-quality solutions. In some cases, when the soil thickness cut by piles is represented by clays or loams, you can do without a solution, replacing it with water. At the same time, in the process of drilling, the so-called "self-mixing" occurs.

In order to ensure a high rate of penetration of the well and to prevent the formation of a cushion from settled sludge under the fifth pile, which can significantly reduce its bearing capacity, it is necessary to provide a high rate of ascending flow of clay solution during drilling. Drilling rigs URBZAM, UGBH-150, CO2, SO-1200, BUK600, etc. are used to drill wells for piles and drill wideners.

CO1200 installation is intended for the device of bored piles with a diameter of 0,81,2 m. This installation consists of working body with an upsetting branch pipe and the conductor and the basic machine (the crane, the excavator). Cranes DEK251 and MHK25 or other grades can be used as basic machines in our case this is DEK50M, equal to or greater than the load carrying capacity and lifting height.

The working body of CO1200 installation includes the submersible electric drive with a ladle drill which is strictly strengthened to a bar the stabilizer on which the carriage is strengthened. Adapter engaged with casing branch pipe is movably secured on electric drive.

The dilator of cyclic action which top end is connected to an electric drive shaft, and lower to the ladle drill used as the soil receiver is included in the package of CO1200 installation. The electric drive of CO1200 installation provides well-drilling dry and wet in the ways.

Unlike other types of installations in the SO1200 unit, the working tool is freely suspended on the crane hook as a long-length load; it is installed on the ground at the wellhead with the help of a conductor (see those maps). Thanks to this solution, it is possible to easily disconnect the working tool from the crane and use it for concreting wells and in various auxiliary operations.

To provide connection of rod with conductor during immersion stabilizer is movably fixed on it. Casing pipe is made of pipe. The conductor designed to stabilize the nozzle is a box-shaped plate. The shell holds the branch pipe in vertical position during drilling. At the corners, the conductor has four sockets in which anchor pins are built.

A significant advantage of this installation is the simplicity of the device. The free suspension of the working tool ensures the specified vertical strength of the well regardless of the distortions of the base crane on the ground, which improves the quality and simplifies the operation of the plant.

CO1200 installation provides the high performance of a driving owing to pressure of the ladle drill, stable on all depth of the well, upon a face reaching 10 t.

Additionally:

The method of drilling under clay mortar was first used in the early 30s when penetrating vertical shafts at the mines of the Moscow Region basin. This method is theoretically substantiated in the works of N. M. Gersevanov.

The process of drilling wells for piles under clay solution (see the map) includes the following operations:

1. - installation of drilling conductor;

2. - installation of casing pipe;

3. - landing of the latter into the well;

4. - start of well drilling within the limits of stable soils .

Wells can be drilled under clay mud by drilling head, URBZAM or UGBX150 unit, in which clay mud is supplied to drilling tool or expander along hollow rod. Subsequent activities include:

5. - pouring of clay solution into the well;

6. drilling;

7. - addition of clay solution to the well.

8. - installation of reinforcement frame;

9. - filling with concrete of the well;

10. - removal of conductor and casing pipe;

11. - mechanized cleaning of pit bottom;

12. - prepared pile field for pile pile arrangement.

In order to perform drilling operations on site, it is necessary to have a mud tank and settling tanks for spent pulp.

Well flushing. Drilled rock is removed using mud pumps of GR11 type with capacity of 15 m3/h. The clay solution simultaneously with the drilled rock removal cools the cutting tool of the bit. Upon completion of drilling, the clay solution is left in the well to avoid collapse and collapse of the walls. Well depth is controlled by means of special lot with load of 2-3 kgf; Besides, diameter of well and presence of casing branch pipe at well mouth are specified.

Based on the results of the inspection, permission is given to install an armocarcade.

General Concrete Care Recommendations:

When concreting piles in hot sunny weather, the freshly laid concrete mixture should be covered with moisture-intensive materials. In rainy weather, the concreted area shall be protected from water ingress into the concrete mixture. Accidentally eroded concrete should be removed and replaced with quality. The concrete mixture laid in the well must be compacted by vibration. Vibration compaction of concrete mix is performed by mass-produced electric or pneumatic vibrators. In order to ensure sufficient compaction of the concrete mixture, the criterion of which is the cessation of its subsidence, the appearance of cement milk on the surface and the cessation of the release of air bubbles, the duration of vibration is established experimentally.

To ensure normal concrete hardening conditions, it is necessary to constantly maintain the required temperature and humidity conditions and protect hardening concrete from impacts and other impacts that worsen its quality.

To protect concrete from the harmful effects of wind and direct sunlight, systematic watering of a moisture-intensive coating is necessary. Open surfaces shall be maintained in a wet state until the concrete reaches 70% design strength.

When in this area the average daily outside air temperature decreases to + 5 ° C, and during the day there is a temperature drop below 0 ° C, special methods of feeding and laying the concrete mixture, as well as special conditions for holding concrete are provided. In winter, concrete is maintained mainly by the method of "thermos," arranged as follows: a burrow of sand or soil is poured around the head of the pile, on which a wooden shield is laid, and all this is filled with sawdust and sand. To expand the scope of application of the "thermos" method, it is advisable to apply preliminary electric heating of the concrete mixture before laying it in the well. Electric heating of the heads of padded piles is also widely practiced, which is carried out with alternating current with a voltage of not more than 127V with simultaneous insulation of the heads of piles with sawdust, mineral wool and other heat-insulating materials. During electrical heating of concrete it is necessary to observe the following mode: exposure after molding - 1 h; rise of concrete mixture temperature to 7080 ° С -4-5h; heating at constant temperature 7080 ° С-12h; cooling - 4-5 h. Temperature rise shall not exceed 1015 ° C in 1h and cooling shall not exceed 10 ° C in 1h.

The temperature during electric heating and electric heating shall not exceed 70 ° C for concrete on Portland cement, and 80 ° C for concrete on slag Portland cement.