RU131389U1 - PILOT-MILLING FOUNDATION WITH REGULATED WORK OF MILLING ON THE GROUND BASIS - Google Patents

Abstract

1. Pile-grillage foundation with adjustable grillage operation on a soil foundation, including piles, grillage and damping pads made of a material of uniform compressibility, characterized in that there is a leveling layer between the pile and damping pad, and the damping pad has a protective casing. 2. Pile-grillage foundation with adjustable grillage operation on a soil foundation according to claim 1, characterized in that a sand-cement mortar is used as a leveling layer. Pile-grillage foundation with adjustable grillage operation on a soil foundation according to claim 1, characterized in that the protective casing is made of sheet metal.

Description

Pile-grillage foundation with regulated work of grillage on a ground foundation refers to construction, in particular, to foundation-building, and is intended for use in the design and construction of pile foundations of industrial and civil buildings. The utility model is designed both for bush and strip pile-grill foundations, and for pile-plate foundations.

Currently, pile foundations are very widely used in the construction industry. Bush pile foundations, strip pile foundations, which are also called pile-grillage foundations, combined pile-plate foundations are being carried out. Existing designs of pile foundations often provide for the operation of the foundation only due to the bearing capacity of the piles. In this case, grillages or plates combining the heads of piles serve only for the distribution of forces in piles and are not taken into account when determining the bearing capacity of foundations.

Known pile foundation, including piles and reinforced concrete grillage, which unites the heads of the piles and provides redistribution of the load on them from higher structures (SP 24.13330.2011. Pile foundations. Updated version of SNiP 2.02.03-85, appendix A). However, in the design and construction of this foundation, the grillage work on the ground is not taken into account, i.e. load perception is provided only due to the bearing capacity of piles. As a result, the bearing capacity of the foundation is not fully used due to the neglect of the transfer of loads to the base through the sole of the grillage.

The closest analogue of the proposed utility model “Pile-grillage foundation with adjustable grillage work on a soil foundation” is the construction of a slab-pile foundation (RF, C2 No. 2301303, IPC E02D 27/12, author Lushnikov VV, etc.), including piles and reinforced concrete slab or grillage, damping gaskets between the heads of piles and reinforced concrete slab or grillage of easily deformable material. Damping pads of uniform compressibility material in a known construction are provided in extruded polystyrene foam. The estimated thickness of the damping pads is accepted in the range from 10 mm to 60 mm with an increase in the direction from the central and middle rows of piles to the extreme rows of piles and corner piles with a ratio of 1: 2: 3, or have the same thickness in the range from 10 to 60 mm, moreover, the ratio of the deformation modulus of the gasket material above the heads of the middle rows of piles, the extreme rows of piles and above the corner piles is taken as 3: 2: 1. The thickness of the damping pad 6 is determined from the ratio:

δ≥ [S _St. + S _sp.max -L (ΔS / L) _u ] E ₀ / p, m,

where s _{St. f} - settlement of the pile foundation without taking into account the compression of gaskets, m;

S _pr.max - maximum draft from compression of gaskets over piles, m;

p is the average pressure on the soil at the bottom of the plate in the place of bearing on incompressible soil, MPa;

L is the size of the reinforced concrete slab in plan, m;

(ΔS / L) _u is the limiting value of the relative difference of sediments.

In a known design, it is indicated that the use of a relatively strong extruded polystyrene foam allows you to completely save the specified initial height of the gaskets δ ₀ at relatively small loads that occur when concreting a reinforced concrete slab or grill. In addition, the manufacture of gaskets with strictly parallel surfaces ensures reliable contact quality of the pile heads with a reinforced concrete slab or grillage after the formation of a complete draft of the slab or grillage.

The disadvantages of the known design include:

- Lack of leveling layer between the pile head and the damping pad. The quality of the joint between the pile and the grillage through the damping gasket should be ensured not only by the smooth edges of the gasket itself, since the pile during the manufacturing process may have various defects and damage. In addition, during the driving of piles, the piles get damaged, which leads to a violation of the contact area between the damping pad and the pile.

- Insecurity of the gasket from damage during concreting. Indeed, polystyrene foam during concreting is able to maintain its original height with slight deformation from the mass of freshly laid concrete. However, when laying heavy grillage concrete, elements of a large aggregate of concrete mixture - pieces of crushed stone with unprocessed faces - fall on unprotected laying material, the concrete mixture hardens, and after curing, the following negative points occur:

- gasket material in local areas is pressed through and receives local damage from crushed stone;

- when hardening concrete, the grillage forms an uneven surface, which does not allow the complete "closure" of the gasket provided in the known design.

- Insecurity of the damping pad from the displacement in the plan. When concreting works, the gasket may shift from the initial position. In this case, a lateral concrete tongue (influx of concrete) is formed in the displacement zone, which is equal in thickness to the gasket. The presence of a concrete key will cause the damping pad to not compress or contract unevenly, which will entail the transfer of force from the grillage to the pile through the side concrete key (in addition to the gasket) and will not provide the intended operation of the interface between the piles and the grillage.

- The provided laying in combination with a plate on a natural basis significantly complicate the calculation of the foundation. In a known design provides the use of gaskets of different thicknesses for different piles. This solution leads to calculation inaccuracies due to an increase in the number of uneven stiffness bonds between piles and slab.

- The pile-pile foundation is a foundation with a large number of piles and a well-developed slab. Since the soil stratum, as a rule, is variable in composition and composition in terms of and in the height of the engineering-geological section, pile trunks and the base of the foundation can be in soils with different characteristics. This will entail the need to calculate the settlement of each individual pile in the pile bush and the individual selection of the thickness of the laying, as a result - the need for additional calculation of the slab and verification of reinforcement.

- The use in a known design of damping pads made of extruded polystyrene foam, for which the values of deformations under a load of 80 ... 90% are indicated. With these values of the deformation of the gaskets, in our opinion, the load transfer to the pile in full and the maximum inclusion of piles in the foundation are not ensured.

The challenges in creating a utility model are:

- development of the construction of the pile foundation with the provision of the adjustable inclusion of grillage in the work of the foundation;

- providing reliable guaranteed transfer of a part of the vertical design forces to the foundation soil through the sole of the grillage;

- an increase in the bearing capacity of the pile foundation due to the work of the grillage as a foundation on a natural basis and more complete inclusion of piles in the work.

The technical result that allows to solve these problems is:

- ensuring the adjustable inclusion of grillage in the work of the foundation;

- ensuring guaranteed transfer of a part of the vertical design forces to the ground through the sole of the grillage,

- increase the bearing capacity of the foundation.

To achieve the specified technical result, “Pile-grillage foundation with adjustable grillage operation on a soil foundation”, as well as the closest analogue, includes piles, grillage and damping pads made of a material with a uniform compressibility (expanded polystyrene). Pile-grillage foundation with adjustable grillage operation on a soil foundation involves the use of gaskets of the same thickness to ensure uniform deformation of the foundation. The thickness of the damping pad Δ _{dp is} fixed and is assigned from the condition:

,

,

where [S _P ] - sediment grillage at a pressure equal to the calculated resistance of the soil base;

[S _St ] - pile upset at a load equal to the permissible design load on the pile;

A _St - the cross-sectional area of the pile;

E _DP - the deformation module of the material of the damping pad;

[N _St ] - permissible design load on the pile;

k ₁ - coefficient taking into account the compression ratio of the damping pad;

k ₂ - coefficient taking into account the range of typical damping gaskets.

To ensure guaranteed transfer of load to the soil through the sole of the grillage and thereby increase the bearing capacity of the pile foundation, a leveling layer and a protective casing for the damping pad are provided between the pile and the damping pad.

New significant features:

leveling layer

safety cover.

These new significant features allow you to get a technical result in all cases, to which the requested amount of legal protection. Due to the leveling layer, the top face of the pile is parallelized, and the section of the pile head damaged during driving is restored, as well as a snug fit of the damping pad, i.e. uniform contact for reliable transmission of forces. This layer is made of cement-sand mortar with a strength grade of at least M100 to ensure the required strength of the assembly. The thickness of the leveling layer depends on the degree of roughness of the pile surface and is Δ _{vs =} 20 ... 30 mm. Immediately after laying the cement-sand mortar on the upper plane of the pile, it is leveled. The alignment can be done in various ways, for example, as follows: the safety cover can be put on to the level of the top of the leveling layer and a small uniform compression is made over the area of the safety cover, then remove the cover. This ensures parallelism of the upper plane of the leveling layer and the contact plane of the grillage. The safety casing ensures the deformation of the damping pad made of polystyrene foam only in the vertical plane, ensures the position of the pad on the piles during the grill installation and protects the pad from mechanical damage, and also ensures reliable operation of the damping pad without the formation of side concrete dowels (concrete influx) . Thanks to this design, the design work of the damping gaskets and the reliable inclusion of the grillage in the work of the foundation take place.

Together, all the features made it possible to create a new technical solution that surpasses the closest analogue in technical result. An indicator of the technical result is the technical effect, which consists in a guaranteed improvement in the transfer of part of the calculated load to the soil through the sole of the grillage, an increase in the bearing capacity of the pile foundation.

Materials explaining the essence of the “Pile-grillage foundation with adjustable grillage operation on a soil foundation”:

Figure 1 presents the "Plate-pile foundation" - an analogue.

Figure 2 presents the "Pile-grillage foundation with adjustable work grillage on a soil base",

Figure 3 on the photo shows the moment of testing the damping pads in the laboratory,

Figure 4 in the photo shows the moment of testing the damping pad at maximum load.

Figure 5 presents the test results of samples of expanded polystyrene in the load interval 0 ... 100 kN.

Figure 6 presents the test results of expanded polystyrene samples in the load interval of 100 ... 700 kN.

Position in figure 1 denote:

1. Pile

2. extruded polystyrene damping pad

3. plate (or grillage).

Position in figure 2 denote:

1. Pile

2. polystyrene foam damping pad,

3. grillage,

4. leveling layer,

5. safety cover.

“Pile-grillage foundation with adjustable grillage operation on a soil foundation” consists of piles 1, a damping pad made of polystyrene foam 2, grillage 3, a leveling layer 4, a protective casing 5.

"Pile-grillage foundation with adjustable work grillage on a soil base" is carried out in the following sequence.

At the very beginning of the work, piles 1 are driven in accordance with the developed project documentation. Piles are immersed to the design level in depth. After driving along the upper planes of the piles, a leveling layer 4 is arranged. This layer can be made of cement-sand mortar with a strength grade of at least M100 to ensure the required site strength. The thickness of the leveling layer depends on the degree of damage and roughness of the pile surface and is Δ _vs = 20 ... 30 mm. Immediately after laying the mortar on the upper plane of the pile, it is leveled, thereby ensuring parallelism of the upper plane of the leveling layer. Next, they lay a damping pad made of polystyrene foam 2, and then a protective casing 5. The protective casing is made of sheet metal. The safety casing ensures the deformation of the damping pad made of polystyrene foam only in the vertical plane, ensures the position of the pad on the piles during the grill installation and protects the pad from mechanical damage, and also ensures reliable operation of the damping pad without the formation of side concrete dowels (concrete influx) . After the final installation of the safety casing, the grillage 3 is concreted.

The authors of the utility model for evaluating the characteristics of damping gaskets tested various types of expanded polystyrene in density. As a result of tests and analysis, it was found that polystyrene foam of the M40 brand has the best characteristics for use in the construction of the foundation.

The wall height of the safety casing h _{k is} assigned from the condition: h _k = Δ _dp + Δ _sun +20 mm, where Δ _dp is the thickness of the damping pad, Δ _sun is the thickness of the leveling layer. The dimensions of the safety casing must be 2 mm larger than the cross section of the pile. After forming the leveling layer, the safety cover is removed. Then they wait several hours to set the initial strength of the leveling layer. After leveling layer

gained initial strength, a damping pad of expanded polystyrene is laid on the upper plane of the leveling layer. The edges of the damping pad should be strictly parallel to the plane of the leveling layer. The dimensions of the damping pad in the plan are taken equal to the size of the cross section of the pile.

When implementing a utility model, the required technical result was achieved:

- ensuring the adjustable inclusion of grillage in the work of the foundation;

- ensuring guaranteed transfer of the estimated load on the soil through the sole of the grillage,

- increase the bearing capacity of the pile foundation.

The positive thing is that it became possible to regulate the work of the grillage and piles on a soil foundation, as well as eliminate the negative factors affecting the work of damping pads when concreting the foundation, thereby ensuring the design work of the damping pads and the guaranteed inclusion of the grill in the work of the foundation.

“Pile-grillage foundation with adjustable grillage operation on a soil foundation” corresponds to the condition “industrial applicability”, because refers to devices widely used in construction for use in the design and construction of pile foundations of industrial and civil buildings.

Claims (3)

1. Pile-grillage foundation with adjustable grillage operation on a soil foundation, including piles, grillage and damping pads made of a material of uniform compressibility, characterized in that there is a leveling layer between the pile and the damping pad, and the damping pad has a protective casing. 2. Pile-grillage foundation with adjustable grillage operation on a soil foundation according to claim 1, characterized in that a sand-cement mortar is used as a leveling layer. 3. Pile-grillage foundation with adjustable grillage operation on a soil foundation according to claim 1, characterized in that the protective casing is made of sheet metal.

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