The technology of indentation of the pile foundation supports is used if the construction is carried out close to other buildings. When driving or using the vibration method, vibrations propagate in the ground, which harm neighboring bases and lead to the appearance of microcracks. Pressing in the piles increases the bearing capacity of the soil, reduces the time it takes to build the foundation, and saves money.
Scope of pressed piles
Reinforced concrete and steel racks are pressed by applying static loads strictly vertically. The technology is superior to other methods in terms of productivity in circumstances where it is necessary to install piles in a densely populated area of the city.
On the longitudinal section, the piles are divided into types:
- prismatic rods are used in residential and industrial construction;
- pyramidal structures are rarely used due to their lower strength and reliability, they are intended for buildings with a small number of storeys;
- trapezoidal supports work well as a base under bridges and overpasses;
- diamond struts are placed in intumescent layers to effectively resist shear.
The pile pressure is used for large volumes of work, when large areas of fields from vertical elements are arranged. The installation is carried out quickly, which speeds up the construction work. Solid and hollow round elements, square and rectangular, are used, I-beams and T-sections are installed.
Unstable soil layers collapse and shift from the dynamic impact of hammers and vibrating units, therefore, crushing the piles with static force prevents such risks.
The power of the machines is sufficient to install a large number of rods without restrictions and the help of auxiliary mechanisms, while hammering methods are implemented only using preliminary drilling of the main pass, therefore the process of hammering in dense layers is expensive.
The main methods of pressing piles
The technology for mounting vertical supports is chosen depending on the physical and mechanical properties of the soil layers. Use equipment that has the characteristics of a point setting, linear or coordination machine. Specialized aggregates are not limited blocks with one function, so their use is convenient to work with.
The pile is fixed by mechanical devices on the support frame. Pumps based on hydraulics supply pressure, the stability of the unit is ensured by weights. Efficient work is ensured by moving the machine using a self-propelled pneumatic chassis.
Separate pile-pressing automatic installations are produced, aimed specifically at the organization of static force. The rack deepens under the influence of the weight of the unit, sometimes vibration is additionally applied if conditions permit.
Point
The method finds application during the period of restoration and renovation work of old buildings, when it is important not to damage existing communications. The point-pressed piles are installed carefully so as not to violate the integrity of the old foundations and adjacent foundations.Hydraulic installation helps to push in the elements.
Technological maps are developed so that the deviation of the central axis of the rack from the projected position does not exceed ± 5 mm horizontally. The place of deepening is marked on the site with pieces of reinforcement, which are hammered into the ground by 20 - 30 cm. For spot installation, the prepared elements are stored in a stack with a height of no more than 2 m, while the heads of the racks are in one side.
If there are several types of support rods, separate storage areas are organized for them. They are lifted and mounted with a construction crane. The piled-down units are positioned so that everyone can work at the maximum number of indentation points. The scheme for moving the machine is indicated in the work flow charts.
Linear
The method consists in the longitudinal movement of the equipment in the direction of the beam row. With the linear method, there is no need to control the center of the axis when deepening each rack, you need to correctly set the longitudinal straight line.
Preliminary work:
- digging of pits, arrangement of drainage and drainage;
- organization of short-term routes for the access of the units to the installation site;
- preparation of a marking plan of the pile space with a breakdown of axes and a mark of the location of elements;
- distribution of lighting and power electrical networks;
- delivery to the site and preparation for the process of mechanisms and units for at least 2 days of work.
The installation is carried out in a linear way by a team of four specialists, which includes the operator of the installation, the crane operator and two slingers-assemblers. The latter help to move the equipment and control the correctness of its location.
Coordinate
Modular schemes are developed, based on two guide beams. Longitudinal landmarks are chosen parallel to the line of the pile strip, along which the pile pressing machine moves. Gradually increase the length of the guide beams as the next section passes. A boom crane assists in the work, which feeds vertical elements and places weights on the installation.
Use an auxiliary metal pile if the head of the main element stops about 60 cm above the surface. The element is clamped in hydraulics and with its help is pressed against the head of the reinforced concrete rack until it is completely immersed in a solid layer.
Selection of pile driving machines
The main unit is a pile driver, which carries out the immersion of piles by the indentation method. The unit is mounted on a chassis for independent movement in the conditions of a construction site.
The following mechanisms are mounted on the unit frame:
- lifting device;
- pile indentation structure;
- moving chassis.
Additionally, a cargo area was installed for the location of anchor weights. The equipment is fixed using side and central fasteners. The machine is designed for a full range of works and does not need to involve additional units.
The stress is evenly distributed along the pile shaft thanks to the multi-point clamping method. The rack is supported by an eight-cylinder body mechanism with square and round seats.
Work technology
The installation of static indentation of piles is prepared for work according to the instructions, hydraulics are installed on the machine frame. They check the levelness of the site, the conformity and accuracy of the marking, remove foreign objects.
After rearranging the unit with a crane in the working area, it is slinged and the coincidence of the sight of the installation with the point of deepening of the pile rod is checked. The slings are removed, power is supplied to the installation, the hydraulic device is raised to a working position.
Place anchor weights on the platform evenly from both sides, check the unit's invariability. Mounting loops are cut from the top of the pile, slinged and lifted with an arrow to the mounting position. The stand is moved and lowered into the hydraulic device so that the tip of the element coincides with the marking point. The pile is lowered to the free tension of the lines, and the hydraulics presses it into the soil.
Advantages and disadvantages of the technology of driving piles by indentation
Advantages of the indentation method:
- the effect of compaction of the soil layer around the pile element;
- lack of complex equipment with dynamic loads;
- there is no loud noise and shock;
- use in any soil with some exceptions.
The disadvantage of this method is that the rocks do not lend themselves to indentation of the vertical struts. But it is possible to calculate the length of the elements in such a way that the solid layer will serve as a support for the tip of the rod.
