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Expanded-Base Piles

Driven pile got a decent alternative

Currently, the construction industry is projected large number of bridges, precast buildings on stilts.The use of driven piles is considered to be a very cheap way of building foundations. However, the use of driven piles accompanied by a large number of complexities and difficulties in the device of pile foundations. You can highlight the main shortcomings of driven piles:

  • Low bearing capacity of pile body 60-100 tons.
  • The limited length of driven piles. Device deeper piles require joining two separate piles and creates a huge challenge for their high-quality piling into the ground.
  • Limited ability to driven piles device within the city limits.
  • Driven piles often crack or collapse when their device
  • Lack of factories producing piles driven in this region, which significantly increases the cost of the work adding transport costs.

For improvement of pile foundations and creating alternatives to knock the piles, specialists of Delta Drilling Company  was analyzed foreign and domestic experience devices bored piles. the main focus of development was selected technology devices piles with widened fifth. This technology was developed per mass unit of piles under complex geological conditions (weak clay or sand, including in saturated soils). The Technical result was to create a high-tech way to construction of piles with widening, providing significant bearing capacity of piles in the ground, in compliance with economic effect (Patent No. 201600052)

Widening at the base of the pile increases carrying capacity and a relatively small body diameter piles (375 mm, 475 mm and 600 mm) saves the concrete. Technical and economic feasibility of the device of foundations on stilts with widened fifth is unquestionable, as a result of a significant increase in their bearing capacity, reducing time and savings device spent material. In the world known to the various ways the device piles with ušireniem. This special razburivaemye piles uširitelem mechanical actions known ways to create reinforcement explosion (kamufletnoe widening), as well as blows. However, the wide dissemination of such piles not yet received in the absence of an effective technology to their devices and control the quality of the received reinforcement.

The essence of technology

Conditionally device expanded-base piles with technology can be divided into 2 stgages:

Stage 1: Device vibrating piles immersion of the liner:

1. Casing with loses tip plunges into the ground by vibration exposure generated by vibrator rigidly attached to the upper end of the casing, the piston. 2. Visual inspection of the tightness of the cavity of the pipe to the absence of the groundwater and the installation of the reinforcement cage-cylinder pipe. 3. Filling the casing with concrete through the top end of the tub by means of, using a concrete pump or if necessary betonolitnoy pipe; (learn more about technology devices piling vibration method)

Stage 2: Device has been widened with the use of piston-cylinder

4. Create the required size has been widened is due to move up-down liner-piston along the reinforcement cage-this allows cylinder push (pressed) concrete, fills the space around the cylinder when lifting the reinforcement cage liner to a height that provides education gap between a pair of piston-cylinder for receipt of concrete. The process occurs before the advent of the refusal that is controlled by the onboard computer readings. If concrete topping in the well seal is performed through measuring beaker by at the top of the casing, to create the desired amount has been widened.

5. Vibrating removing liner-piston with simultaneous sealing of concrete mixture in the trunk of a pile. Tip forming piles.

            When vibro compaction of soil is due to its displacement to the side in the amount of piles, which ultimately leads to an increase in the bearing capacity of bored pile. soil particle displacement zone with vibro slabovlazhnyh in soils is 2.5-3 radiuses of bored piles and saturated - 4-5 radiuses.

фото свай после раскопки

          When generating the additional reinforcement soil compaction due to the impact a pair of piston-cylinder, square bearing piles on the ground (diameter piles increases 1.8-3 times) and, consequently, increasing drag that ultimately leads to a significant improvement in the bearing capacity of piles. 

After holding dozens of tests can distinguish the main comparative advantages of bored piles with widening before:

  • Driven piles

1) Increased carrying capacity. Confirmed by the results of field tests of soils indentation static load: for bored piles with bearing capacity of 280 TC; for  driven pile  140 TC 

Graph of rainfall piles of load

2) Increased production speed works by reducing the number of piles, while maintaining design carrying capacity.

3) device piles up to 30 m (without connections with high quality assurance and validation capability concreting pile integrity tests).

4) there is no dependence on the range and availability of PRECAST plant, which often adds an extra rise in cost due to additional transport costs for delivery of piles.

5) quality control continuity and dimension widening stage.

6) Estimated economic effect when replacing driven piles on bored varies from 30% to 50%.

As can be seen from the report results (table 1) with the same geological conditions, as well as the length of the piles, borestuffing pile with widening has a considerable load on the ground. 

Project calculation load capacity of piles with ušireniem on both the body and the ground can reach 600 tons and replace up to six driven piles.

Bored piles of large diameters  (under construction protected by a casing). When using piles with broadening instead of piles of large diameters with the same load-carrying capacity takes place concrete significant savings as well as reducing the time piles device.

Quality control

The process of forming piles with widening are constantly in control by measuring the supply volume of concrete in the liner through the measuring beaker as a reinforcement. Thing dug out here confirms piles with subsequent reinforcement measurement indicates a direct dependence of flow volume concrete reinforcement created piles. Thus, this technology offers a high-tech way to construction of bored piles with ušireniem both horizontally and vertically which ensures considerable resistance of piles in the ground through the use of specific structural adaptations, as well as controlled by time and the flow of material in the process of its construction. 
For control of expanded-base pile technology of Delta Drilling Company  in conjunction with the American company PDI PileDynamicsInc. was introduced and adapted device TIP Thermal Integrity Profiler. The basic principle of this equipment is based on the termal integrity method of measurement of curing temperature (catching) concrete energy of hydration. (Read more)

 

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