RU2687211C1 - Method of increasing dynamic rigidity of a foundation under a vibration load and a device for its implementation - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: group of inventions relates to construction, specifically to methods of constructing foundations for installations with dynamic loads, and is intended to provide vibration reliability of both existing and newly erected foundations, mainly light-ventilated foundations (LVF), including in permafrost soils (PFS), under water and in earthquake-prone areas. Method to increase dynamic rigidity of foundation includes compensation of foundation vibrations with equipment placed on it as source of dynamic loads by connection of concrete plate of specified dimensions separately on surface of soil by means of connecting complex, ensuring tight fit of the slab to the ground at possible vertical displacements of the slab relative to the foundation due to the connecting complex. Preliminary calculated amplitude-frequency characteristics of foundation-equipment system with dynamic effects on this system from equipment. Directions are selected and dynamic force is determined in horizontal plane in each direction, number of plates is selected based on the condition of counteraction to each dynamic effect, using at least one concrete plate for each direction. Connection system is made of elongated rod-shaped connector and plate-like horizontal elements on both sides of connector.

EFFECT: technical result consists in improvement of vibration resistance of foundations, mainly LVF in a given frequency range.

13 cl, 10 dwg, 5 tbl

Description

The group of inventions relates to the construction, and in particular to methods of constructing foundations for installations with dynamic loads, and is intended to ensure the vibration reliability of both existing and newly constructed foundations, mainly light ventilated foundations (PSL), including in permafrost soils (VMG ), under water and in seismic zones.

There is a method of protecting foundations of buildings, structures from dynamic effects in the soil and a device for its implementation (see RF patent №2622279, IPC E02D 31/08, publ. 13.06.2017). The method includes making a trench into which protection devices are immersed, at a distance from a building, a structure along its structural elements subjected to dynamic effects. Protection devices are interconnected, and two extreme protection devices are connected to an external tank containing a damping fluid.

Known technical solutions are designed to reduce the intensity of external influences in the soil, and not from equipment placed on the foundation. In addition, they are not applicable in the conditions of the VMG, as well as on marshy soils.

The prior art known support structure and method of its construction in the construction of foundations on weak soils, on the supporting surface of which are anchor protrusions of complex shape, which in a certain way orient when building the foundation to ensure the reliability of the foundation when exposed to active loads (see RF patent № 2107768, IPC E01C 9/00, published on 03/27/1998).

A disadvantage of the known construction is the limited scope of application, which is due to the fact that the invention is applicable only to foundations in the form of a slab and does not apply to other types of foundation structures. In addition, the disadvantage of the invention is the increased complexity in the manufacture and placement on the support surface of the plate personalized elements.

There is a known foundation for equipment containing upper and lower plates, racks, with each rack equipped with upper and lower rods installed inside the racks, while the internal volume of the racks is filled with loose damping material, and a certain clearance of rods inside the racks is provided with counterweight cargo through cables, attached to the top plate (see the description of the utility model of the Russian Federation No. 99027, IPC E02D 27/44, publ. 10.11.2010).

The disadvantage of the known foundation is the increased complexity of the design, low reliability, limited ability to withstand the active load.

A device and method of strengthening the base of the mast against pulling it out of the ground is known. The proposed device and method of strengthening the base of the mast support against pulling, and the specified base contains at least one massive block, buried in the ground of the location of the base, which contains the plate with the largest cross-section in the horizontal plane. The slab should have greater density and / or greater resistance to shear deformation than the ground (or soil) of the base location. The effect is achieved by the involvement of additional mass from the soil lying above the plate and the opposing tearing force of the mast acting on the support (see RF Patent No. 2392387, IPC E02D 27/50, publ. 06.06.2010).

A disadvantage of the known device and method is the limited scope of application. The limited scope of application due to the fact that the effect of the invention manifests itself mainly in countering the vertical load.

There is a method of reducing vibrations and reducing their harmful effects on existing foundations (see the work Pavlyuk NP, Kondin AD On the redemption of vibrations of the foundations of machines. - Project and Standard, 1936, №11).

The method consists in the fact that a simple concrete slab located on the top layer of the ground joins the oscillating foundation. The resistance of such a plate to horizontal oscillations is very significant. The dimensions of the slab in each case must be selected by calculation, however, the effect of redemption can always be increased even after the slab installation - by increasing it. One of the advantages of the method is the possibility of the removal of the plate beyond the perimeter of the foundation.

To eliminate the manifestation of the harmful effects of unequal sediment of the foundation and the slab, it is recommended to carry out the connection between them by installing an intermediate rigid pivotally attached link (see the description on pp. 190-191 in work - Savinov OA, Modern designs of foundations for machines and their calculation. Ed. 2nd, revised and extra, L .: Stroyizdat. Leningrad branch, 1979, - 200 p. Il.). This method and design for its implementation are the closest to the proposed solution.

However, the known method does not provide an effective vibration resistance of the foundation, since the place of joining the concrete slab is chosen arbitrarily without taking into account the location of the points of origin and the directions of dynamic loads. The use of articulated joints reduces the efficiency of the method, since vibrations with an amplitude less than the possible gaps of the hinge will not be extinguished, and the gaps themselves will only increase with time. The method itself is based on an increase in inertial mass and an increase in resistance due to friction on the ground, which in turn leads to an increase in material intensity. In addition, the method and device suggest the proximity of the plate, and therefore there is a difficulty with the dense arrangement of adjacent process equipment and piping, as well as when used on the VMG.

From the foregoing it follows that in the prior art there is a need to increase the dynamic vibration resistance of foundations, both existing and newly built, when this effect is difficult to achieve with known methods.

A technical problem is the development of a method and device that compensates for oscillations of the foundation from installed equipment as a source of dynamic loads (IDN) in the working frequency range.

The technical result is to increase the vibration resistance of the foundations, mainly PSL, in the operating frequency range of the IDN.

The technical result is achieved by the fact that in the method of increasing the dynamic rigidity of the foundation, which includes joining the foundation to the foundation with the equipment placed on it as a source of dynamic loads, at least one concrete slab located on the surface of the soil determine by calculation, according to the invention, to determine the number of plates to be attached, the amplitude-frequency characteristics of the foundation system are calculated equipment with dynamic effects on the system from IDN, allocate directions and determine the dynamic impact force in the horizontal plane for each direction, the number of plates is chosen from the condition of counteraction to each dynamic effect, using at least one concrete slab for each direction, and for each plate determine by calculating its geometrical parameters, location and joining the foundation, while the connecting complex for each plate consists of an elongated rod eobraznogo connector and plate-like horizontal elements on both sides of the connector. By means of a connecting complex, a dynamic impact is transmitted from the foundation to the slab and ensures that the slab is permanently located in a horizontal plane, correcting the vertical displacements of the slab relative to the foundation and its tight fit to the ground during the entire service life due to bending of plate-like elements.

The method provides for the possibility of weighting the concrete slab with an additional load, additional filling with a weighting mortar or by cooling the concrete slab to freeze environmental components.

The underside of the concrete slab may have triangular isosceles prismatic protrusions, the edges of which, protruding from the concrete slab, are oriented, in plan, perpendicular to the dynamic effect transmitted to the concrete slab.

The technical result is also achieved by the fact that in the device for implementing the method of increasing the dynamic stiffness of the foundation, containing at least one concrete slab and a connecting complex for connecting the slab and foundation, according to the invention, the connecting complex consists of an elongated rod-like connector and plate-like horizontal elements with both sides of the connector, while the bottom side of the concrete slab may have triangular isosceles prismatic protrusions, the edges of the sides of the Isms protruding from the concrete slab are oriented in plan perpendicular to the dynamic effect transmitted to the concrete slab.

Triangular prismatic protrusions can be located close to each other for self-consolidation of the soil under the slab during vibration.

The upper side of the concrete slab has limiting sides to hold the additional weight placed on top of the slab.

Concrete slab, in turn, may consist of separate blocks located on the soil surface and interconnected in series.

The volume of the concrete slab contains cavities for the refrigerant supplied from a separate device.

Applying the device on VMG, use a heater of a concrete plate for protection against external thawing influence.

The invention is illustrated by drawings, where:

in fig. 1 shows a device illustrating the principle of operation of a method for increasing the vibration resistance of a foundation;

in fig. 2 shows the connection of a concrete slab to the foundation with a connecting complex;

in fig. 3, 4 shows options for weighting the slab with additional weight;

in fig. 5 shows the option of weighting the plate due to the freezing of environmental components and protection from thawing effects;

in fig. 6 shows a device of a concrete slab with prismatic protrusions on the bottom surface;

in fig. 7 shows the use of an additional element of rigidity in the transmission of vibration effects from IDN located on high foundations;

in fig. 8 shows a light ventilated foundation based on the proposed method (hereinafter - PSL-S) with IDN;

in fig. 9 shows a graph of the amplitudes of the oscillations of the basement at the calculated points of vibration loads for various types of foundations;

in fig. 10 shows the graphical form of the results of the calculated comparison of the amplitude-frequency characteristics at the calculated points of vibration loads for different types of foundations.

In the drawings, the positions indicated:

1. Foundation (PSL);

2. Installed equipment - a source of dynamic loads (IDN);

3. Place of connection of the concrete slab to the foundation;

4. Concrete slab;

5. Force (vector) of impact of IDN;

6. Soil - the base of the foundation and concrete slab;

7. Rod-like connector;

8. Plate-like element;

9. The existing building around the location of the foundation;

10. Additional cargo;

11. Building mixture;

12. Limiting boards;

13. Cavities for refrigerant;

14. Insulation;

15. Triangular prismatic protrusions;

16. Triangle stiffness that transmits vibration.

The invention is also illustrated in the tables, where:

table 1 - the source data to determine the dynamic loads;

table 2 - a comparative table of material intensity of pile foundations;

table 3 - a comparison of the general material consumption of foundations;

table 4 - comparison of labor costs for the production of concrete work;

table 5 - comparison of electricity costs for heating the concrete mix.

The method of increasing the dynamic stiffness of the foundation under vibration load is implemented as follows.

Geometric and amplitude-frequency characteristics of the foundation 1 are measured or determined. Further, based on the analysis of the amplitude values of vibration at different operating modes of the equipment installed on foundation 1 (IDN) 2 and certain resonant frequencies of the foundation equipment system, they determine the points (points) of the 3 connections and parameters joining concrete slab 4 to counter the force 5 dynamic effects on the system foundation-equipment in the horizontal plane. To compensate for each force 5, use the corresponding concrete slab 4 or a group of several concrete slabs 4 (Fig. 1). At the same time, depending on the characteristics of the foundation-equipment system, soil geology 6, vibration load 5 from IDN and other conditions, the parameters and the number of concrete slabs 4, points 3 of their connection to the corresponding side of foundation 1, the direction of force compensation 5 and t .d The calculation can be based on the finite element method using well-known software products, for example, SCAD Office (version 21.1.7.1). To the foundation 1, the concrete slab 4 is attached using a connecting complex consisting of a rod-like connector 7 and two plate-like horizontal elements 8 on both sides (Fig. 2). Concrete slab 4 plays the role of an additional anchor, which, without increasing the vertical load on the soil 6 of the main foundation 1, counteracts its horizontal oscillations, including by changing the resonant frequency of the foundation equipment system. For the constrained conditions of the existing building 9, it is permissible to divide one concrete slab 4 into a group of slabs in the direction of compensation of forces 5.

To increase the weight of the concrete slab 4, it can be weighted by means of an additional load 10 (Fig. 3) or various building mixtures 11 (Fig. 4). To keep the weight on the plate above, the limiting sides 12 are intended. The weight of the plate 4 can be increased by freezing the soil 6 and the environmental components to the base of the plate 4, which is especially effective on the VMG. For freezing it is possible to use external refrigerant supplied from a separate device through special cavities 13 of plate 4. The plate 4 is protected from thawing with a layer of insulation 14 (Fig. 5), geometrical dimensions, thickness, material and other parameters, which are selected based on the results of a separate thermal calculation.

The bottom side of the concrete slab 4 has triangular prismatic protrusions 15, which are located close to each other and are oriented with the long side perpendicular to the forces 5 to provide maximum resistance to dynamic effects. The location of the projections 15 close to each other contributes to the self-consolidation of the soil 6 under the slab 4 (Fig. 6).

For high foundations there is a danger of a leverage of forces between the upper face of the foundation on which the IDN is installed and the plane of the concrete slab. For this, a stiffening element is provided, for example, in the form of a rigidly bound rectangular triangle 16 (FIG. 7), one leg of which is parallel to the ground surface, the second leg is attached to the vertical face of the basement, and the hypotenuse connects the upper point of the basement and the connecting complex.

The method and device based on it allows to reduce the weight of the main foundation due to the separation of the vibration load into two horizontal and vertical components. Then, the main foundation compensates for the weight of the equipment and the vertical dynamic load, and the horizontal component of the vibration load is compensated, including using plates. The method and device for its implementation allows to obtain a technical result in which, through the use of relatively small additional concrete slabs, it is possible to increase the dynamic rigidity of the main foundation in a given frequency range. The method is versatile, which allows it to be used when compensating for vibration effects, both for existing foundations and for newly designed ones. The method allows to reduce the time of reconstruction of the existing foundation and the cost of reconstruction. The method is applicable for foundations located in the cramped conditions of the built-up area, on the VMG, underwater location and in seismic zones.

An example of a specific implementation of the method can be a comparative calculation of the amplitude-frequency characteristics of the three foundations for a gas-turbine gas pumping unit with a capacity of 16 MW (HPA): a massive foundation (MP), PSL and a foundation based on the proposed method — PSL-S (Fig. 8). Baseline data for determining the dynamic loads of the HPA for the calculation are shown in Table 1.

The calculation for the three foundations was carried out by the finite element method using SCAD Office (version 21.1.7.1). The main indicators of the material consumption of the MF, PSL and PSF-S structures are shown in Table 2. At the same time, steel pipes (Ф426х9) for piles are immersed in wells 100 mm in diameter larger than the pile diameter, and then the annulus and the internal cavity of the pile are filled with M150 solution.

The foundations of MF, PSF and LPF-S are based on a soil base, represented by: a) from the level of planning to a depth of 2 m - with medium-sized bulk sand with compaction coefficient k = 0.95; b) from a depth of 2 m to a depth of 10 m from the level of planning - semi-solid loam with a turnover index IL = 0.15; c) below the depth of 10 m - with coarse, medium density sand.

For the VMG and the conditions according to the type of conditions of Eastern Siberia, PSF has several advantages over the MF, which consist in reducing the material intensity and providing ventilation, which reduces the thawing effect on the VMG. The disadvantage of PSL compared to the MF is that its low mass is insufficient to dampen the vibrations of the equipment.

The parameters of the attached device is determined by calculation, for this:

- determine the frequency and direction of the maximum oscillations of the foundation-equipment system when operating IDN, for comparative calculation we get - λ = 43.96 1 / s;

- calculate the amplitudes of oscillations (along the X and Y axes) corresponding to the dynamic impacts on the foundation at the points of application;

- build the oscillation curve of the basement at the points of application of dynamic effects on the foundation.

After the oscillation curve of the foundation, which corresponds to the maximum amplitudes of oscillations, is determined, the number and parameters of the concrete slabs to be attached, their parameters, places and directions of attachment are determined so that the device for implementing the method (concrete slab) counteracts each dynamic effect on the foundation coaxially with this impact (in the horizontal plane). Next, the oscillation amplitudes of the foundation with the attached device are determined. FIG. 9 shows a graphical comparison of the amplitudes of oscillations of MP, PSL and PSL-S.

FIG. 10 shows the graphical form of the calculated comparison of the amplitude-frequency characteristics of the MP, PSL and PSL-S. According to the results of the comparison, the maximum amplitude of the PSL-C oscillations is 48.8% less and 49.6%, respectively, of the maximum amplitudes of the MP and PSL oscillations.

Table 3 compares the general material consumption of foundations. Table 4 shows a comparison of labor costs for the production of concrete work. Table 5 shows a comparison of the cost of electricity for heating a concrete mix at negative temperatures.

Conclusions on the basis of calculations for the foundations for GPA-16MW:

- the maximum amplitude of the PSL-C oscillations is 48.8% less and 49.6%, respectively, of the maximum amplitudes of the MP and PSL oscillations;

- the maximum compressive load on the pile foundation of LPS-S is less by 187% and 29.4%, respectively, of the loads from the MF and LFT;

- The total material consumption of LPF-S is 8 times less than that of the MF and 28.4% less than that of the BLF;

- the cost of transporting building materials to the construction site of PSF-S is 8 times less than that of the MoF and 28.4% less than that of the PSF;

- given that the maximum compressive load on the pile foundation with the device is less by 29.4% - it is possible to reduce the depth of laying the pile foundations by 20%;

- For the MF and the PSF, concrete works with a volume of 372 m ³ and 12 m ^{3 are} required.

The construction of gas facilities is a year-round process, and, in order to avoid major losses, should not depend on weather conditions. The main criterion for high-quality concreting in winter is the heating of concrete, since according to SP 70.13330.2012, the technological heating of concrete is regulated if the minimum daily air temperature falls below 0 ° C. In addition, for the laying of the concrete mix in the winter, it is provided for its electrical heating to a temperature of 50 ° C for 5-10 minutes. For preheating, the site requires an electrical power of 250 kWh per cubic meter of concrete. In addition, additional equipment is used for heating the concrete mixture: a formwork-thermos that heats the cable in the body of the foundation and hot rooms with heating by heat guns. The area of the heating formwork for one MF is 740 m ² , at the PSF is 190 m ² , at the PSL-C is 12 m ² . Then, the total costs of heating the concrete mix MF are 155500 kWh, for PSL costs are 3000 kWh, for LPF-S are 300 kWh.

Thus, the advantage of LPF-S compared to the MF and PSF is in reduced costs for material consumption, for transportation of building materials to the construction site, for labor costs of concrete work, as well as for the costs of electrical energy for heating the concrete mixture at negative temperatures, besides , method and device allow to reduce the dependence of the course of construction of the foundations on the season and the temperature state of the external environment.

Claims (13)

1. A method of increasing the dynamic stiffness of the foundation, including compensation of foundation vibrations with equipment placed on it as a source of dynamic loads by attaching a concrete slab of a given size separately on the soil surface using a connecting complex, ensuring that the plate fits snugly to the ground with possible vertical displacement of the plate relative to foundation due to the connecting complex, characterized in that the amplitude-frequency Characteristics of the foundation-equipment system with dynamic impacts on this system from equipment, highlight directions and determine the dynamic impact force in the horizontal plane in each direction, the number of plates is chosen from the condition of counteraction to each dynamic effect using at least one concrete slab for each direction, at the same time the connecting complex is made of an elongated rod-like connector and plate-like horizontal elements are connected on both sides body. 2. The method according to p. 1, characterized in that the weight of at least one concrete slab with an additional weight. 3. The method according to p. 2, characterized in that the weighting of the concrete slab is carried out by additional filling with a weighting mortar. 4. The method according to p. 1, characterized in that they cool at least one concrete slab to freeze environmental components. 5. A device for implementing the method of increasing the dynamic rigidity of the foundation according to claim 1, comprising at least one concrete slab and a connecting complex for connecting with the foundation, characterized in that the connecting complex consists of an elongated rod-like connector and plate-like horizontal elements on both sides of the connector. 6. The device according to claim 5, characterized in that the underside of the concrete slab has triangular isosceles prismatic protrusions, the faces of the lateral sides of the prismatic protrusions are oriented, in plan, perpendicular to the dynamic effect transmitted to the concrete slab. 7. The device according to claim 5, characterized in that the triangular prismatic protrusions are located close to each other. 8. The device according to claim 5, characterized in that the upper side of the concrete slab has limiting sides to hold the additional weight placed on top of the slab. 9. The device according to p. 5, characterized in that the concrete slab consists, in turn, of separate blocks located on the ground surface and interconnected in series. 10. The device according to claim 5, characterized in that the volume of the concrete slab contains cavities for the refrigerant. 11. The device according to claim 5, characterized in that the concrete slab contains insulation to protect against external thawing effects. 12. The device according to claim 5, characterized in that the connecting complex from the side of the plate attached to the foundation is provided with a stiffening element. 13. The device according to p. 12, characterized in that the stiffening element is made in the form of a triangle, with one leg of the triangle parallel to the ground surface and connected to the plate, the second leg is designed to be attached to the vertical base of the basement, while the hypotenuse connects the upper point of the basement and connecting complex.

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