RU141393U1 - HEAT-INSULATED FOUNDATION - Google Patents

Abstract

A heat-insulated foundation, including a wall and a sole, a pillow made of non-porous material, a gasket made of heat-insulating material, such as polystyrene foam, on the bottom of the pillow made of non-porous material, if necessary, an additional insulation around the foundation body, under the ceiling and blind area, characterized in that the thickness of the pillow is non-porous material between the heat-insulating gasket and the base of the foundation is taken equal to the thickness of the frozen soil layer below the foundation formed at the beginning of the construction work July of the foundation, and the thickness and dimensions in terms of heat-insulating laying under a pillow made of non-porous material are set according to the heat engineering calculation from the condition of preventing freezing of the soil below the laying.

Description

The invention relates to the construction of foundations of mainly low-rise buildings on seasonally freezing heaving soils.

A well-known foundation on freezing soil (analog foundation), including a sole and a foundation wall with a gasket on the sole side facing the ground, made of heat-insulating material, for example, polystyrene foam, an additional insulation placed outside the foundation and connected to the floor insulation and blind areas (Patent RU No. 2357044, IPC E02D 27/01, 27/35 “Thermally insulated foundation” [1]).

The disadvantage of the analog foundation is the impossibility of building it in the winter, when before the start of construction, partial freezing and swelling of soils below the lower surface of the laying has already occurred. The formed permafrost under the heat-insulated foundation-analogue remains for a long time. Subsequent thawing of frozen and swollen soils, which also takes a long time, leads to inevitable uneven precipitation of the foundation and the structure built on it.

The technical solution closest to the claimed object is a foundation on permafrost soils (prototype foundation), which includes filling a foundation pit of non-porous material below the foundation with the introduction of reinforcing elements in it in the form of rigid reinforced concrete, while the top layer of the plate is made of heat-insulating material with slopes from the center of the slab to the edges, and the stiffness of the slab is selected depending on the amount of deformation of thawing permafrost soils (RF Patent No. 2270295, IPC E02D 27/01, 27/35 “Method tvrascheniya deformations foundations constructed on permafrost "[2]).

The disadvantage of the prototype foundation is the impossibility of constructing it in seasonally freezing heaving soils in the winter, when partial soil freezing occurred at the time of foundation construction.

The purpose of the claimed invention is to enable the installation of thermally insulated foundations in seasonally freezing heaving soils in the winter, when partial freezing and swelling of the soil has already occurred before construction began.

The goal is achieved by the fact that in a thermally insulated foundation, including a wall and a sole, a pillow of non-porous material, a gasket of heat-insulating material, for example, polystyrene foam, at the bottom of a pillow of non-porous material, if necessary, an additional heater placed around the foundation body, under the ceiling and blind area , in the proposed heat-insulated foundation, the thickness of the cushion of non-porous material between the heat-insulating gasket and the sole of the foundation is taken equal to the thickness of the frozen layer the soil below the foundation, formed at the beginning of the construction of the foundation, and the thickness and dimensions in terms of heat-insulating gaskets under a pillow made of non-porous material are set according to the heat engineering calculation in order to prevent freezing of the soil below the gasket.

The totality of the proposals formulated above almost completely eliminates the freezing and swelling of the soil below the cushion of non-porous material and heat-insulating gaskets, which ensures the achievement of the goal - to increase the stability of heat-insulated foundations in seasonally freezing heaving soils in the winter, when partial freezing and swelling of the soil occurred before construction began.

In contrast to the prototype foundation [2], the proposed thermally insulated foundation does not require the introduction of reinforcing elements in the form of a rigid reinforced concrete slab into the cushion of non-porous material, as well as resizing the insulating gasket from the center to the edges.

An analysis of the prior art did not reveal an analogue characterized by features identical to all the essential features of the proposed solution, i.e. It meets the requirements of novelty.

Not detected are also signs that are distinctive in the claimed solution, i.e. It meets the requirement of inventive step.

The invention is illustrated by a drawing (Fig. 1), which shows a thermally insulated strip foundation for a two-story house.

The heat-insulated strip foundation includes a sole 1 and a wall 2 made of hard material (reinforced concrete). From the outside of the foundation there is a blind area 3; the ceiling 4 is supported on the wall 2. On the side of the base of the foundation 1, facing the ground, a pillow of non-porous material 5 is placed, and below it, a gasket 6 of extruded polystyrene foam. On the outer and inner surfaces of the sole 1 and wall 2 there is an additional insulation (pos. 7 and 8, respectively), which in the general case can be connected to the floor insulation 4 (pos. 9) and the blind area 3 (pos. 10).

On the wall of the foundation 2 rests on the wall of the aboveground structure 11 with external and internal insulation. The composition of the insulated foundation also includes concrete preparation 12 and backfill 13. Position 14 shows the lower boundary of the freezing of the soil d _f formed at the beginning of the construction of the insulated foundation, and position 15 indicates the standard depth of freezing d _{f, n} . The contours of the trench for constructing a thermally insulated foundation are shown in FIG. 1 by 16.

For the installation of a thermally insulated foundation in the winter, frozen soil is excavated to the lower freezing boundary d _f (pos. 14) in the form of a trench; a gasket 6 is laid on its level bottom and a pillow filling of non-porous material 5 is made with the necessary seal. Next, concrete preparation and foundation with the necessary electrical heating are done.

For an example illustrating the essence of the invention, it is assumed that the construction of a thermally insulated foundation is carried out in Yekaterinburg in early December at an outdoor temperature of -15 ° C; standard freezing depth 15 d _{f, n} = 1.9 m; the freezing depth of 14 soil at the time of the beginning of work on the construction of the foundation d _f = 0.7 m

The depth of laying the bottom of the foundation 1 is taken equal to d = 0.3 m, and the thickness of the cushion 5 of non-porous material h _p is equal to the thickness of the frozen ground layer below the sole 2 of the foundation formed at the beginning of the construction of the foundation h _p = d _f -d = 0.7-0.3 = 0.4 m, i.e. the difference between the freezing depth 15 d _f and the depth of laying d of the sole 2 of the insulated foundation.

The soil at the base of the heat-insulated foundation is represented by a highly heaving deluvial loam, the heaving properties of which are characterized by the relative deformation of frost heaving ε _fh = 0.075. Estimated soil resistance R _gr = 220 kPa, deformation modulus E _gr. = 10 MPa, thermal conductivity of loam in the thawed state λ _th = 1.57 W / (m · ° C), volumetric heat capacity C _th = 3.17 J / (m ³ · ° C) 10 ^-6 . The temperature of the soil at the bottom of the pit is 16 + 1.5 ° C.

For the device of the cushion 5, non-porous material is used - granite crushed stone, which during the installation of the heat-insulated foundation has an outdoor temperature of -15 ° C; specific gravity 21 kN / m ³ ; rated resistance R _under. = 500 kPa, deformation modulus E _under. = 40 MPa, thermal conductivity in the frozen state λ _f = 2.90 W / (m · ° C), volumetric heat capacity C _f = 2.26 J / (m ³ · ° C) 10 ^-6 .

For the heat-insulating strip 6, “Penoplex” extruded polystyrene foam was used, which has a calculated compressive resistance R _{sr pr} = 150 kPa, a deformation modulus E _sr = 1.0 MPa, and thermal conductivity λ _ave = 0.042 W / (m ° C).

In the calculations of the thickness of the strip 6 adopted the following additional source data:

- load per 1 m of length (l = 1.0 m) of the sole 1 of the foundation: n = 250 kN / m;

- the width of the sole of the foundation 2: b = 2.0 m;

- the area of the sole 1 of the foundation 1: A = lb = 1.0 · 2.0 = 2.0 m ² / m;

- the weight of the foundation and soil on its ledges G = 40 kN / m;

- the depth of the sole 2 of the foundation: d = 0.30 m

The calculation of the heat-insulated foundation is carried out in accordance with the requirements of chapter SP22.13330.2011 “Foundations of buildings and structures”, and the parameters for laying 6 of extruded polystyrene foam are determined according to the heat engineering calculation using the NEAT-PTF ₂ program (two-dimensional).

From the calculation in accordance with the instructions of the chapter SP22.13330.2011 follows:

- the average pressure on the sole 1 of the foundation: p _cf = (n + G) / A = (125 + 40) /2.0=82.5 kPa <R _gr = 220 kPa;

- the average pressure on the gasket 6: p _cf = (n + G) / A + γ _under. · H _under. = (125 + 40) /2.0+21·0.7=94.5 kPa <R _{sb, pr} = 150 kPa;

- foundation sediment 1 (taking into account the compressibility of cushion 5, gasket 6 and natural soil S = 0.7 cm <[S] _u = 10 cm.

The requirements of the chapter SP22.13330.2011 are fulfilled.

In the heat engineering calculations using the NEAT-PTF ₂ program, the thickness of the gasket 6 was successively taken equal to 50, 70, and 100 mm, and its thickness was taken as the final result of the calculation at which the soil does not freeze below the gasket 6 for several months, up to endings of natural thawing of soil.

With the above thicknesses and thermal characteristics of the anti-cushion pad 5, gasket 6 and natural loam, the initial temperatures of the pad material 5 and loam, and also taking into account the average monthly outdoor temperatures for the period from December to May for the city of Yekaterinburg (SNiP 23-01- 99 “Construction climatology”), the values of the soil temperature and the depth of the freezing zone below strip 6 were obtained (which corresponds to the temperature of the onset of loam freezing equal to -0.2 ° C (see chapter SNiP 2.02.04-88 “Basic foundations and foundations on permafrost soils ”).

Table 1 Soil temperature and freezing depth below gasket 6 Gasket Thickness 6 Monitored parameters Months 2010 January February March April May fifty temperature T, ° C -0.2 -0.4 -0.5 -0.5 -0.2 depth Δd _f , m 0.2 0.4 0.6 0.5 0.3 70 temperature T, ° C -0.1 -0.2 -0.2 -0.1 0 depth Δd _f , m 0.1 0.2 0.2 0.1 0 one hundred temperature T, ° C 0 -0.1 -0.1 0 +0.2 depth Δd _f , m 0 0 0 0 0

The thickness of the gasket 6, equal to 70 mm (see Fig. 1), which protects the loam from freezing, is recognized as safe: the maximum freezing depth 14 below the sole of the gasket 6 in February - March was Δd _f = 0.2 m, and the corresponding possible soil swelling was ΔS = ε _fh · Δd _f = 0.075 · 0.2 = 0.015 m = 1.5 cm, safe for the foundation and the two-story house in the built form, since the total settlement of the foundation S + ΔS = 0.7 + 1.5 = 2.2 cm will not exceed the allowable according to the instructions of chapter SP22.13330.2011 value of [S] _u = 10 cm. When the thickness of gasket 6 of 100 mm freezing polnost excluded, but in this example this thickness of gasket 6 may be considered excessive.

The advantages of the proposed solution of a thermally insulated foundation on freezing heaving soils compared to the prototype foundation are in providing effective protection of heaving soils from freezing during construction work in the winter.

List of materials used

1 Patent RU No. 2357044, IPC E02D 27/01, 27/35. The heat-insulated foundation / V.V. Fluffers. - Publ. 05/27/2009.

2 RU patent No. 2270295, IPC E02D 27/01, 27/35. A method for preventing deformation of foundations erected on permafrost soils / V.A. Babello, A.P. Krivorotov and D.S. Mari. - Publ. 02/20/2006.

Claims (1)

A heat-insulated foundation, including a wall and a sole, a pillow made of non-porous material, a gasket made of heat-insulating material, such as polystyrene foam, on the bottom of the pillow made of non-porous material, if necessary, an additional insulation around the foundation body, under the ceiling and blind area, characterized in that the thickness of the pillow is non-porous material between the heat-insulating gasket and the base of the foundation is taken equal to the thickness of the frozen soil layer below the foundation formed at the beginning of the construction work July of the foundation, and the thickness and dimensions in terms of heat-insulating laying under a pillow made of non-porous material are set according to the heat engineering calculation from the condition of preventing freezing of the soil below the laying.

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