RU2500857C1 - Method to submerge piles by indentation - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method to submerge piles by indentation includes charging of a pile into a working organ of an indentation plant, and the pile is installed vertically and pressed in the clamping mechanism. The pile is submerged at the value of the indentation mechanism hydraulic jack piston travel (up to 1.0 m), the pile is released in the working organ of the plant, the stems of the indentation mechanism hydraulic jacks are raised into the upper position (idle run), the pile is again clamped, and the cycle is repeated from the start until the pile is submerged to the design depth. Indentation of the pile in case of dense soils in the geologic cross section is carried out with increase of the indentation force to the value equal to the sum of the front resistance of the pile in these layers of soils and side resistance within the limits of the entire depth of pile submersion in the section, and also the speed of pile indentation is reduced to the minimum value determined from the specified ratio.

EFFECT: increased efficiency of the method of pile indentation into layers of dense soils.

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Description

The method relates to the field of construction, the invention can be used when immersing piles by pressing them into layers of dense soils with soil resistance exceeding the maximum force of the pressing unit.

A known method of immersing piles by indentation, including applying static indentation force to a pile by various methods (V. Burov, Research of piling immersion by indentation method in order to substantiate the selection of optimal parameters of pile-pressing installations: abstract of dissertation of Candidate of Technical Sciences. - Omsk, 1969 .-20 s.).

The disadvantages of the method are technological limitations when immersing piles in layers of dense soils (deformation modulus E> 14 MPa, yield index I _L <0.3), due to the lack of a method for determining the parameters of indentation (force and speed) depending on the strength characteristics of soil layers, components of the geological section, including the bearing layer.

Closest to the proposed technical solution is a method of immersing piles by indentation, which involves loading piles into an operating unit of an impression installation, which is installed vertically and clamped in the clamping mechanism, pile is immersed by the piston stroke of the hydraulic jacks of the indentation mechanism (up to 1.0 m), the piles are expanded in the working body of the installation, raise the hydraulic ram jacks of the indentation mechanism to the upper position (idle), clamp the pile again and the cycle is repeated first until the pile is immersed in the design deep depth. When immersing piles in layers of dense soil with an immersion resistance exceeding the maximum force of 2 indentation provided by the installation, in which the immersion is stopped, the pile is removed and the special methods described below for reducing the soil resistance to immersion are used (Guiding technical material. RTM 36.44.12.2-90. Design and the installation of foundations from piles, immersed by the indentation method. - SPb .: VNIIGS, 1992. - 46 p.).

However, the considered method has the following disadvantages: extraction of piles from the soil and the subsequent use of special methods to reduce soil resistance to immersion in the form of drilling leader wells, loosening the soil with a screw, the use of antifriction coatings of the pile surface lead to a decrease in labor productivity by more than 2 times, an increase in the cost of work 40% and reduce the bearing capacity of piles on the ground to 20%. In addition, it is technically difficult to remove submerged piles from a depth of more than 10 m, which requires a change in design and the immersion of additional piles.

The objective of the solution to which the present invention is directed is to increase the efficiency of the method of pushing piles into layers of dense soils.

The method of immersing piles by pressing includes loading piles into the working body of the pressing installation, which is installed vertically and clamped in the clamping mechanism, pile is immersed by the size of the piston stroke of the hydraulic jacks of the pressing mechanism (up to 1.0 m), the piles are expanded in the working body of the installation, and the hydraulic jacks are raised pushing the mechanism into the upper position (idle), again clamp the pile and the cycle is repeated first until the pile sinks to the design depth. In this case, if there are layers of dense soils in the geological section, the indentation force is increased to a value equal to the sum of the frontal resistance of the piles in these soil layers and lateral resistance within the entire depth of immersion of the piles along the section, and they also reduce the indentation speed of the piles to the minimum value determined from the expression :

V = (F _vd -F _d ) / F _d n

where V is the pile-in speed, m / min;

F _vd - indentation force, kN;

F _d - bearing capacity of piles in the interval of immersion, kN.

n = 0.4-0.9 experimental coefficient, the average value of which is 0.6.

This action provides a reduction in the viscous resistance of the soil, which increases linearly with increasing speed of the pile. As a result, the reduction of additional soil resistance is achieved, which allows the piles to be immersed in layers of dense soil without increasing the indentation force and the weight of the installation.

In the process of pile immersion to the design elevation, the applied force and the indentation speed are set depending on specific engineering and geological conditions, including the occurrence of soils of different densities determining the resistance of the pile in the immersion interval.

A mathematical dependence is known, which determines the force of indentation of piles by a static load F _in [Bakhdin B.V. Investigation of the process of immersion of piles by indentation / Bakholdin B.V., Perley EM, Svetinsky EV // - M. Foundations of foundations and soil mechanics, 1997. -№3. p.25-27]:

$$F_{\mathrm{at}d}=\left(R+VnR\right)A+\left(f+Vnf\right)\Omega ,\mathrm{to}N\begin{array}{ccc}& & \end{array}\left(\mathrm{one}\right)$$

where R, f is the specific static soil resistance under the lower end and along the side surface of the pile, respectively, kN / m ² ;

V - pile indentation speed, m / min;

n = 0.4-0.9 experimental coefficient (average value is 0.6), which determines the dependence of viscous resistance on the specific static soil resistance under the lower end and along the side surface of the pile;

A is the cross-sectional area of the pile, m ² ;

Ω is the surface area of the pile, m ² .

Expression 1 is written as:

$$F_{\mathrm{at}d}=F_d+F_{d}nV,\mathrm{to}N\begin{array}{ccc}& & \end{array}\left(2\right)$$

where F _d - the bearing capacity of the piles in the immersion interval, because

F _d = RA + fΩ.

From expression 2, the indentation speed is determined by the formula:

$$V=\left(F_{\mathrm{at}d}-F_d\right)/F_{d}n\begin{array}{ccc}& & \end{array}\left(3\right)$$

Equation 3 allows you to adjust and adjust the force of the indentation and the speed of immersion of the piles depending on the presence in the geological section of soil layers of different densities.

When indenting piles in dense soil layers, the indentation force is increased to a value equal to the bearing capacity of the piles in the immersion interval, and the indentation speed is reduced to a minimum value. In soft soils, the force is reduced and the indentation speed is increased to a maximum value.

The effectiveness of the proposed method is confirmed by the authors on the basis of statistical processing of experimental data obtained in a production environment on a significant number of real construction projects. In the course of experiments in various engineering and geological conditions, the dependences of the changes in the depth and time of immersion of the piles on the changes in effort and speed of indentation were investigated. So, it was established that when pressing piles into the bearing layer of dense soils to ensure the piles are immersed to the required depth, the pushing force is set to a value of _Fd = 1.0-1.2, the pile pushing speed is reduced to zero, and thus the pile is kept under load until the beginning process of “forcing” the layer.

The method of immersion piles by indentation is illustrated in the drawing, where Fig. 1 shows a fragment of a technological map with graphical dependencies that determine the change in technological parameters along the depth of indentation of a pile;

on figa - presents a General view of the installation of the indentation of piles and the location of the piles in a geological section, including, including bedding dense soils;

on figb - presents a graph of changes in the force of indentation (F _VD ) along the immersion depth of the pile (D);

on figv - presents a graph of the change in the speed of indentation (V) along the immersion depth of the piles (N).

The method is implemented as follows.

Piles are pressed in from piles 1 from the soil surface by pressing in piles 1. When piling in piles of dense soils 3, the pressing force is increased to a value equal to the sum of the frontal resistance of piles in these soil layers and lateral resistance within the entire depth of the pile immersion along the section, and reduce the speed of pressing piles to a minimum value.

Indentation in this mode is performed, it is so necessary to immerse piles through the encountered layers of dense soil or to the design level.

To determine the technological parameters of the indentation, the calculation of changes in the values of the bearing capacity of the pile F _d in the immersion interval for each element constituting a geological section, including layers of dense soils, is initially performed. Then determine the required indentation force values (F _vd = 1,0-1,2F _d) and construct a corresponding graph of the parameter on the immersion depth H (1b).

Next, according to dependence 3, the values of the indentation velocity V are calculated according to the depth of immersion and a corresponding graph of the parameter changes along the immersion depth H is constructed (Fig. 1c).

When immersing piles, the driver of the indentation installation on the basis of the graphs presented in the technological map, taking into account the formation of weak and dense soils as part of the geological section, adjusts the operating parameters of immersion in the pile proportionally changing the force and speed of indentation according to the method described above.

The result is an increase in the efficiency of the method of pressing piles in layers of dense soils.

Claims (1)

The method of immersing piles by pressing includes loading piles into the working body of the pressing installation, which is installed vertically and clamped in the clamping mechanism, pile is immersed by the piston stroke of the hydraulic jacks of the indentation mechanism (up to 1.0 m), the piles are expanded in the working body of the installation, and the hydraulic jacks are raised pushing the mechanism into the upper position (idle), again clamp the pile and the cycle is repeated first until the pile is submerged to the design depth, characterized in that the pile is pressed in if there are geologists cross-section of layers of dense soils increase the force of indentation to a value equal to the sum of the frontal resistance of piles in these soil layers and lateral resistance within the entire depth of immersion of the piles along the section, and also reduce the speed of indentation of piles to the minimum value determined from the expression:
V- (F _vd -F _d ) / F _d n,
where V is the speed of indentation of piles, m / min;
F _vd - indentation force, kN;
F _d - bearing capacity of piles in the interval of immersion, kN;
n = 0.4-0.9 experimental coefficient, the average value of which is 0.6.

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