RU2256032C1 - Road embankment built on permafrost ground - Google Patents

Abstract

FIELD: building, particularly for constructing road embankments on permafrost ground bases.

SUBSTANCE: road embankment comprises embankment body, ballast section formed on the main embankment area and heat insulation layer. Road embankment has side auxiliary ground bodies having h_b heights and B_b widths located from ballast section sides within the boundaries of the main embankment area on natural ground surface at embankment slope base. Embankment body includes three layers, namely lower layer having h_l height, medium layer having h_m height and upper one having h_u height. Upper layer is made of drainage soil. Heat insulation layer having R_h thermal resistance is located on leveling layer of dry frozen sand immediately under side auxiliary ground body. Heat insulation layer extends from its bottom to medium layer top surface and then over the top surface to vertical plane passing through the edge of main embankment area. Auxiliary ground body h_b height is defined to increase convenience of mechanized embankment forming and is equal to 0.3 - 0.7 m in separate areas thereof. Main embankment dimensions are determined from predetermined conditions.

EFFECT: increased embankment stability and durability.

2 cl, 1 dwg

Description

The invention relates to the field of construction, namely the construction of road embankments on permafrost soils of the bases.

The transverse profiles of embankments constructed under ordinary conditions outside the permafrost distribution zone are known (M.A. Frishman, I.N. Khokhlov, V.P. Titov. Subgrade of railways. Publishing House Transport, 1972, p.15 , fig. 1).

A drawback of such embankment profiles when applied to permafrost distribution is that frozen soils of the embankment base are thawed in the warm season, which entails deformation of the road structure itself.

Closest to the proposed one is an embankment with the use of special measures to stabilize the soil in its body using foam insulation and thermal diodes, intended for use in construction on permafrost soils (G.N. Zhinkin, I.A. Grachev “Features of the construction of railways in areas of permafrost and marshes ”, M., UMK MPS of Russia, 2000, p.31, Fig. 1.6).

The disadvantage of this design is that it requires the use of imported drainage soils in the embankment body and does not guarantee against deformation of the subgrade due to thawing or thawing of the frozen base, especially during road construction in the warm season.

The present invention solves the problem of ensuring the stability and durability of the embankments constructed from local frozen ice-saturated soils constructed in the cold season.

To achieve the specified technical result in a road embankment on permafrost soils containing the embankment body, a ballast prism located on the main embankment site and a heat-insulating layer, auxiliary auxiliary ground arrays of height h _b and width _b located on the sides of the ballast prism within the main platform are arranged mound, it slopes and on the horizontal section on the natural ground surface adjacent to the base of the embankment slopes, embankments and the body is made of three levels: a lower height h _nJ, the average height that h _cp and made of the draining of the upper tier of lot h _ext height, wherein the insulating layer thermal resistance R _T is located on the alignment layer of suhomerzlogo sand directly under the lateral auxiliary array from the bottom to the level of the top of the middle body tier embankment, then along the upper surface of the middle layer embankment body to the vertical plane passing through the main site curb mound, the height h _b of the auxiliary side determined array convenience mechanized dumping it and can be s different at its individual portions, wherein the main dimensions of the mound define conditions

in _calculation ≤ in _b = in _n + in _open + in _g , m,

h _nzh ≥ h _b , m,

h _int ≥ h _t -h _bp , m,

_cf. h = h _n -h _{nJ corolla} -h, m,

where in _calculation is the width of the lateral auxiliary soil mass, determined by thermophysical calculation from the conditions for ensuring the required soil temperature under the ballast body, m;

in _b - the width of the lateral auxiliary soil mass, m;

in _p - the distance between the edges of the ballast and the main platform of the embankment, m;

in _open - the length of the slope of the embankment, m;

in _g - the length of the horizontal section of the auxiliary array at the bottom of the slope of the embankment, m;

h _nzh - the height of the lower tier of the body of the embankment, m;

h _b - the height of the lateral auxiliary soil mass, m;

h _int - the height of the upper tier of the body of the embankment, m;

h _t - the depth of the maximum possible seasonal thawing of the soil, m;

h _BP - the height of the ballast, m;

h _cp is the height of the middle tier of the body of the embankment, m;

h _n - the body height of the embankment (without ballast), m

The essence of the invention is illustrated by the drawing, which shows a cross section of the embankment.

The road embankment on the permafrost soils of the proposed design contains the body 1 of the embankment laid on the natural surface 2 of the soil, a ballast prism 3 located on the main platform 4 of the embankment, side auxiliary arrays 5 located on the sides of the ballast prism within the main platform 4, its slopes 6 and on a horizontal section on the natural surface of the soil at the bottom of the slopes of the embankment. The slope of the slopes of the embankment provide 1: 3 and more. This is explained by the nature of the snowfall in conditions of heavy snow transfer: the more the slope, the less snow tolerance. The thickness h _{b of the} side auxiliary arrays is determined by the convenience of mechanized styling, it can be variable in width in _b and is 0.3-0.7 m. In this case, when sloping, for example, 1: 4, the width of the horizontal section of the side auxiliary array will be 1, 2-2.8 m, which allows the use of sealing equipment. The body of the embankment contains three tiers: the lower one with a height of h _nzh , the middle one with a height of h _cp and the upper one with a height of h _int . The height h _{int of the} upper tier is determined by the depth of seasonal thawing: h _int ≥ h _t - h _bp , where h _t is the depth of the maximum possible seasonal thawing, m; h _BP - the height of the ballast, m. This tier is poured from dry frozen sand. The lower and middle tiers are sprinkled from local hard-frozen soil and should not thaw during operation to avoid subsidence. The total height of the lower and middle tiers is determined by the difference in the total height of the embankment and the height of the upper tier and tends to decrease the height of the embankment to the height of the lower tier if the horizontal part at the base of the embankment of the lateral auxiliary massif is made of non-draining material, and to zero, if it is made of drainage. In the latter case, the height of the embankment is equal to the height of the upper tier, and the entire heat-insulating layer is horizontal.

A road embankment on permafrost soils also contains a heat-insulating layer 7, for example, “penoplex”, with thermal resistance R _t located on the leveling layer 8 of dry frozen sand directly below the lateral auxiliary massif from below to the top of the middle tier of the embankment body, then along the upper surface of the middle tier of the body embankments to a vertical plane passing through the edge of the main platform of the embankment. The total length in _calculation and the power R _{t of the} heat-insulating layer are determined by thermophysical calculation and is calculated from point A, which is half the width of the main platform of the embankment from the axis of the embankment, i.e. on in _op / 2. The heat-insulating layer together with the lateral auxiliary massif extends beyond the bottom of the slopes of the embankment to a width of at least two depths of seasonal soil thawing.

Positions 9 and 10 show the position of the upper boundary of permafrost soils at the end of the warm season, respectively, before and after the construction of the embankment. To remove atmospheric precipitation from the ballast prism and the upper tier of the embankment body, a geotextile filter layer 11 is laid at the bottom of the upper tier with a slope of 0.01-0.02 slope and is discharged 20-30 cm beyond the lateral auxiliary array. The geotextile layer can be also laid under the ballast and on the surface of the slope 6 within the upper tier of the embankment with a height of h _ext . Moreover, the upper part of the lateral auxiliary massif, located above the upper surface of the middle tier, is constructed either from draining soil, such as sand, or from any soil, but with slots from draining soil to drain rainwater from the upper tier of the embankment. The part of the lateral auxiliary array located below the upper surface of the middle tier is sprinkled from any soil. The horizontal boundaries of the thermal insulation 7 and the leveling layer 8 are shown at 12.

The construction of the road embankment on permafrost is carried out in the winter. First, the lower and middle tiers of body 1 of the embankment are sprinkled with hard-frozen local soil. In this case, it is possible to use icy soil, since it is assumed to be frozen during the entire period of operation. After soil compaction, a leveling layer 8 is poured and a heat-insulating layer 7 is laid. Next, auxiliary auxiliary arrays 5 are poured out by successively laying horizontal layers and mechanizing their compaction. After filling in the lower and middle tiers of the body of the embankment, along with the thermal insulation and the lower part of the side auxiliary arrays, first the upper tier of the body of the embankment is poured in the same sequence, and then the ballast prism along with the remaining part of the side auxiliary array.

Road embankment on permafrost soils works as follows. In winter, the upper part of the embankment is exposed to snow, so there is an intensive flow of cold into the ground, especially in the OA section. And although in the summer period there is also an intensive supply of heat, due to the negative average annual air temperature, the overall balance is negative. Snow accumulates in the slope zone and at the bottom of the embankment in winter, so the overall heat balance can be close to zero or even positive, so laying a heat-insulating layer is advisable here. Lateral auxiliary array serves to protect the thermal insulation from damage. In its upper part, it also serves to eliminate the “sailing” of the ballast. The cold entering through the OA section into the body of the embankment spreads over the entire width of the embankment and is difficult to exit into the air in summer due to the presence of thermal insulation over most of the width of the embankment. As a result, stable negative soil temperatures are formed in the body and base of the embankment.

The main technical contradiction was as follows. To save permafrost in the body of the embankment as much as possible, it is advisable to install a device under the main thermal insulation pad, as was done in the prototype. However, in this case, the influx of cold through the main site, bare in the winter from snow, slows down. Thus, on the one hand, thermal insulation is needed, on the other - no. The way out of the contradiction was found as follows: on the width of the main site, the thermal insulation was eliminated, which ensured the “entrance” of the cold, and the “exit” of the cold was complicated by the device on the side of the embankment of thermal insulation. At the same time, so that the height of the active layer, which increases in summer as a result of the elimination of thermal insulation, does not lead to subsidence, the upper tier of the embankment body, dumped from non-subsidence when thawing soils, is formed to the height of the active layer.

The effective use of the proposed technical solution:

- regions with strong snow transport;

- embankments higher than the height of the active layer for the exposed surface.

The proposed design allows the use of local frozen ice-saturated soils subsiding during thawing.

Claims (2)

1. Road embankment on permafrost soils, containing the body of the embankment, a ballast prism located on the main site of the embankment, and a heat-insulating layer, characterized in that it contains lateral auxiliary arrays of soil of height h _b and width _b , located on the sides of the ballast prism within the main site of the embankment, its slopes and on a horizontal section on the natural surface of the soil at the bottom of the slopes of the embankment, while the body of the embankment is made up of three tiers: the lower height h _nzh , the average height h _cp and the upper height h _{in n} , and the upper tier is made of drainage soil, and the thermal insulation layer with thermal resistance R _t is located on the leveling layer of dry frozen sand directly under the side auxiliary massif, from the bottom to the top of the middle tier of the embankment body, then along the upper surface of the middle tier of the embankment to a vertical plane passing through the primary site curb mound, wherein the height h _b of the auxiliary side determined array mechanized dumping its convenience and amounts to 0.3-0.7 at its individual portions, with the major dimensions of the conditions defined by the mound in _b = in _n + in _open + in _g , m h _nzh ≥ h _b , m h _int ≥ h _t -h _bp , m _cf. h = h _n -h _nJ -h _corolla, m where in _b is the width of the lateral auxiliary soil mass, m; in _p - the distance between the edges of the ballast and the main platform of the embankment, m; in _open - the length of the slope of the embankment, m; in _g - the length of the horizontal section of the auxiliary array at the bottom of the slope of the embankment, m; h _nzh - the height of the lower tier of the body of the embankment, m; h _b - the height of the lateral auxiliary soil mass, m; h _int - the height of the upper tier of the body of the embankment, m; h _t - the depth of the maximum possible seasonal thawing of the soil, m; h _BP - the height of the ballast, m; h _cp is the height of the middle tier of the body of the embankment, m; h _n - the body height of the embankment (without ballast), m 2. The road embankment on permafrost soils according to claim 1, characterized in that a filter layer of geotextile with a slope of 0.01-0.02 towards the slope of the embankment is laid in the sole of the upper tier of the embankment body, while the geotextile layer is released outside the lateral auxiliary massif by 20-30 cm, and the geotextile layer can also be laid under the ballast and on the slope surface within the upper tier of the embankment with a height of h _ext .