CN114855519A

CN114855519A - Saline soil roadbed laying method and roadbed structure

Info

Publication number: CN114855519A
Application number: CN202210578103.0A
Authority: CN
Inventors: 周凤玺; 杨仕钊
Original assignee: Lanzhou University of Technology
Current assignee: Lanzhou University of Technology
Priority date: 2022-05-25
Filing date: 2022-05-25
Publication date: 2022-08-05

Abstract

The invention relates to a method for laying a salinized soil subgrade and a subgrade structure, which relate to the field of subgrade construction in salinized soil areas, and the method comprises the following steps: carrying out layered filling compaction and filling from the foundation to obtain an embankment; longitudinally laying a partition layer on the embankment along a route; and backfilling a base layer on the partition layer. The invention can solve the problem that gas in soil is gathered under the partition layer, and improve the safety of the saline soil subgrade.

Description

Saline soil roadbed laying method and roadbed structure

Technical Field

The invention relates to the field of roadbed construction in saline soil areas, in particular to a saline soil roadbed laying method and a roadbed structure.

Background

Under the influence of external environment, moisture and salt in the saline soil are both transferred, diseases of different degrees can be caused, and the diseases are expressed as salt expansion, frost heaving, slurry turning and the like, which can cause cracking, swelling and expansion of the roadbed, so that the stability and the strength of the roadbed are reduced. If the salt at the lower part of the roadbed can be effectively prevented from moving along with the rising of underground water or capillary water, the damage and the influence caused by the salt migration of the saline soil water can be effectively solved. The method for preventing the salt from rising by arranging the partition layer is a common method for treating the salinized soil subgrade at present. The partition layer can be divided into a sandstone material partition layer, a geotechnical material partition layer and the like according to the material of the partition layer.

Wherein, the partition layer filled by sandstone materials is called as a sandstone material partition layer, but has strict requirements on the selection and construction of sandstone materials; the partition layer made of geotextile materials is called as a geotechnical material partition layer and is generally arranged between a road embankment and a road bed or between a subbase layer and an upper base layer, and although the geomembrane partition layer has the characteristics of better water resistance and salt separation, simple and convenient construction and reduction of the height of a roadbed, the geomembrane partition layer is not beneficial to the escape of water vapor in the roadbed due to the watertightness and can form gas accumulation below the geomembrane partition layer to cause a weak interlayer.

Disclosure of Invention

The invention aims to provide a method for laying a saline soil subgrade and a subgrade structure, which can solve the problem that gas in soil is gathered under a partition layer and improve the safety of the saline soil subgrade.

In order to achieve the purpose, the invention provides the following scheme:

a method for laying a salinized soil subgrade comprises the following steps:

carrying out layered filling compaction and filling from the foundation to obtain an embankment;

longitudinally laying a partition layer on the embankment along a route;

and backfilling a base layer on the partition layer.

Optionally, the laying of a partition layer on the embankment along the route in the longitudinal direction specifically includes:

paving the geomembrane of the partition layer on the embankment along the full section of the route;

and laying the protective layer of the partition layer on the geomembrane.

Optionally, after the protective layer of the partition layer is laid on the geomembrane, the method further comprises the following steps:

paving coarse-grained soil on the protective layer and rolling; the sum of the thicknesses of the coarse-grained soil and the protective layer is less than or equal to 400 mm.

The utility model provides a salinized dirt road base structure, salinized dirt road base structure use above-mentioned salinized dirt road base method of laying, salinized dirt road base structure includes: pavement layer, base layer, partition layer and embankment;

the partition layer is arranged between the base layer and the embankment; the basic unit setting is in the pavement layer with cut off between the layer.

Optionally, the loose thickness of the embankment is less than or equal to 300 mm.

Optionally, the grade range of the road arch cross slope of the partition layer is 2% -5%.

Optionally, the partition layer comprises a geomembrane and a protective layer laid on the geomembrane; the geomembrane is laid on the embankment.

Optionally, the slope gradient of the road surface layer ranges from 1:1.5 to 1: 2.

Optionally, the geomembrane comprises an upper layer, a middle layer and a lower layer which are laid in sequence; the upper layer structure is a glass fiber net or a loose-handling glass fiber net; the middle layer is a polyethylene waterproof ventilated membrane with the pore diameter of 0.1-10 mu m; the lower layer is a loose disposal glass fiber net.

According to the specific embodiment provided by the invention, the invention discloses the following technical effects:

the invention carries out layered filling compaction and filling from the foundation to obtain the embankment; longitudinally laying a partition layer on the embankment along a route; and backfilling a base layer on the partition layer. By laying the partition layer on the embankment, the problem that gas in soil is gathered under the partition layer can be solved, and the safety of the salinized soil subgrade is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is a flow chart of a method for laying a saline soil roadbed provided by the invention;

fig. 2 is a schematic structural diagram of a salinized soil roadbed provided by the invention.

Description of the symbols:

4-geomembrane and foundation distance, 5-pavement layer, 6-base layer, 7-road arch cross slope of partition layer, 8-embankment, 12-geomembrane, 14-slope gradient and 15-protective layer.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

As shown in fig. 1, the method for laying a salinized soil subgrade provided by the invention comprises the following steps:

step 101: and carrying out layered filling compaction and filling from the foundation to obtain the embankment.

Construction for the embankment 8:

1. and the soil pit at the side of the line is drained according to the design requirement and meets the environmental protection requirement.

2. The embankment 8 should be filled and compacted layer by layer, and the loose paving thickness should not exceed 300 mm. The optimal water content is controlled within +/-1% during rolling, and the water content of coarse-grained soil is not more than-2% to + 3% of the optimal water content. The compacted thickness of the coarse-grained soil is not more than 300mm, the compacted thickness of the aeolian sand is not more than 400mm, and the construction is not suitable in rainy days.

3. The embankment 8 is constructed by continuously constructing from the foundation treatment and continuously filling the embankment on top of the protective layer 15 of the barrier layer.

4. The viscous saline soil area with high underground water level is suitable for construction in summer; in sandy saline soil areas, the construction is suitable in spring and early summer; in areas with strongly saline soil, the construction is suitable for spring with low salt content on the surface layer.

5. The salt content of the filler is controlled in the process of embankment 8 filler reinforced construction, and the salt content is controlled to 10000m per embankment ³ A group of salt content tests should be carried out, and the tests should be carried out at any time when the material source changes. And (4) the filler with the test result not meeting the technical requirement of the corresponding layer is forbidden to use, and the filler is immediately cleaned and taken out of the field.

Step 102: longitudinally paving a partition layer on the embankment along a route; wherein, it vertically lays the layer of cutting off along the route on the embankment, specifically includes: paving the geomembrane of the partition layer on the embankment along the full section of the route; and laying the protective layer of the partition layer on the geomembrane. After the protective layer of the partition layer is laid on the geomembrane, the method further comprises the following steps: paving coarse-grained soil on the protective layer and rolling; the sum of the thicknesses of the coarse-grained soil and the protective layer is less than or equal to 400 mm.

And (3) construction of a partition layer:

1. the geomembrane 12 should be laid along the longitudinal full section of the route, and should be tightly attached to the lower bearing layer after being spread without folds. If there is a damage, the damaged area should be repaired with 2 times of the damaged area.

2. The geomembrane 12 is longitudinally lapped by an inner width and an outer width, the lapping width is not less than 200mm, and the lapping width of one outermost width is more than 300 mm; the transverse lap width should be greater than 500 mm.

3. After the geomembrane 12 is laid, the geomembrane should be covered by the material loading protective layer 15 in time so as to avoid long-time insolation.

4. The protective layer 15 arranged by matching the geomembrane 12 and the geomembrane 12 must not contain stones with edges and corners, and the maximum particle size of the aggregate within the distance of 80mm of the geomembrane 12 must be strictly controlled not to be larger than 50mm and manually removed when necessary.

5. The filler of the protective layer 15 on the geomembrane 12 is paved by a light bulldozer or manually, and the material transporting vehicle is used for discharging materials or manually transporting the materials.

6. The geomembrane 12 laid in the fine-grained soil is provided with a protective layer 15 with the thickness not less than 0.3m, and the geomembrane 12 laid in the coarse-grained soil can adopt the thickness of the protective layer 15 of 0.1 m. Medium grit or gravel can be used, the maximum particle size should not be greater than 50mm, and the content of particles with a particle size of less than 0.075mm should not be greater than 10%.

7. And rolling the protective layer 15 for 2-3 times after flattening, paving a layer of coarse-grained soil, and rolling the coarse-grained soil and the upper protective layer 15 together, wherein the thickness of the coarse-grained soil and the thickness of the upper protective layer should not exceed 400 mm.

Step 103: and backfilling a base layer on the partition layer.

In the construction of high-speed and first-level highways, the compaction degree of the top surface from the embankment 8 to the protective layer 15 is more than or equal to 96 percent; and other roads are more than or equal to 95 percent. In the construction of high-speed and first-level highways, the compactness of the partition layer (the geomembrane 12 and the protective layer 15) is more than or equal to 96 percent; the other roads are more than or equal to 94 percent. In the construction of high-speed and first-level highways, the compaction degree from the partition layer (the geomembrane 12 and the protective layer 15) to the top of the pavement layer 5 is more than or equal to 94 percent; and the other roads are more than or equal to 93 percent.

As shown in fig. 2, the invention provides a salinized soil roadbed structure, which applies the salinized soil roadbed paving method, and comprises the following steps: pavement layer 5, base layer 6, partition layer and embankment 8; the partition layer is arranged between the base layer 6 and the embankment 8; the base layer 6 is disposed between the pavement layer 5 and the partition layer. Pavement layer 5, basic unit 6 and embankment 8 are from the top down's distribution relation, and wherein, geomembrane 12 is laid with protective layer 15 between basic unit 6 and embankment 8, and need decide slope 14 according to soil property and salinization degree.

In an alternative embodiment, the loose thickness of the embankment 8 is less than or equal to 300 mm.

In an optional embodiment, the grade of the road arch transverse slope 7 of the partition layer is in a range of 2% -5%. The slope of the road arch transverse slope 7 of the partition layer is not less than 2%, and the maximum transverse slope is not more than 5%. Grade percent is elevation increment/horizontal increment (tangent) 100%, usually expressed in percentage in engineering.

As an alternative embodiment, the partition layer comprises a geomembrane 12 and a protective layer 15 laid on the geomembrane 12; the geomembrane 12 is laid on the embankment 8. The isolating layer is arranged below the base layer 6 and is higher than the original ground by more than 0.5m and not less than the maximum freezing depth of the local area. The geomembrane 12 of the present invention is a water-and air-permeable membrane. The distance between the geomembrane and the foundation is more than or equal to 0.5 m.

As an alternative embodiment, the slope gradient 14 of the pavement layer 5 ranges from 1:1.5 to 1: 2. The slope gradient is also a tangent value, and the elevation is set as unit 1, that is, the slope gradient is equal to the slope elevation/horizontal increment, and the slope gradient is generally set as 1: indicates, for example, 1:1.5 converted into an angular unit of about 33 °

As an alternative embodiment, the geomembrane 12 comprises an upper layer, an intermediate layer and a lower layer laid in this order; the upper layer structure is a glass fiber net or a loose-handling glass fiber net; the middle layer is a polyethylene waterproof ventilated membrane with the pore diameter of 0.1-10 mu m; the lower layer is a loose disposal glass fiber net. The geomembrane 12 is a composite film, and can realize water resistance and air permeability.

The invention solves the problems of the diseases in the roadbed construction of the saline soil area under the condition that the quality of the sandstone material is not easy to control or the underground water level is higher, and improves the economy and the safety of the construction of the saline soil roadbed. The water-proof and breathable film is utilized to form a partition layer, the principle is that gas in pores of a soil body is gas, water particles are very fine usually in a state of water vapor with certain humidity, and the gas can smoothly permeate to the other side of a capillary tube according to the principle of capillary motion, so that the gas permeation phenomenon is generated. When liquid water is in the pores, the particles become large, and water molecules cannot smoothly permeate to the other side due to the action of the surface tension of the water, so that the permeation of the water is prevented, and the breathable film has a waterproof function. In specific application, the material of the water-proof and breathable film is selected according to the requirements of aging resistance, corrosion resistance, freezing resistance and the like. Can do benefit to the loss of separation layer lower part gas when cutting off the soil normal water salt migration and rise, have better water proof, separate salt, characteristics such as construction are simple and convenient, can effectively solve that sandstone class material separation layer cost is high and the more troublesome not enough of construction and traditional geomembrane separation layer are unfavorable for the shortcoming of gas loss in the ground to reach the purpose of dealing with saline soil foundation disease better.

The partition layer of the invention adopts a water-proof and air-permeable geomembrane, the water-proof and air-permeable geomembrane is laid according to the processing width of the roadbed, the water-proof and air-permeable geomembrane is laid to be flat and tightly attached to the foundation, a base layer is backfilled on the geomembrane, and the water-proof and air-permeable geomembrane is filled and rolled in layers; and coating the area to be treated by using a water-proof and air-permeable geomembrane. The invention can effectively prevent diseases such as foundation salt expansion, corrosion and the like caused by the migration of water salt in the saline soil, avoid the accumulation of gas in the soil under a partition layer, and has convenient construction and low construction cost.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.

The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.

Claims

1. A method for laying a salinized soil roadbed is characterized by comprising the following steps:

longitudinally laying a partition layer on the embankment along a route;

and backfilling a base layer on the partition layer.

2. The method for laying a salinized soil roadbed according to claim 1, wherein the step of longitudinally laying a partition layer on the embankment along the route comprises the following steps:

and laying the protective layer of the partition layer on the geomembrane.

3. The method for laying a salinized soil subgrade as claimed in claim 2, wherein after the protective layer of the partition layer is laid on the geomembrane, the method further comprises the following steps:

4. A saline soil roadbed structure, which is characterized in that the saline soil roadbed structure applies the saline soil roadbed laying method of any one of claims 1 to 3, and the saline soil roadbed structure comprises: pavement layer, base layer, partition layer and embankment;

5. The salinized soil roadbed structure of claim 4, wherein the loose thickness of the embankment is less than or equal to 300 mm.

6. The salinized soil roadbed structure of claim 4, wherein the grade of the road arch transverse slope of the partition layer is in the range of 2% -5%.

7. The salinized soil roadbed structure of claim 4, wherein the partition layer comprises a geomembrane and a protective layer laid on the geomembrane; the geomembrane is laid on the embankment.

8. The salinized soil roadbed structure of claim 4, wherein the slope gradient of the pavement layer is in a range of 1:1.5-1: 2.

9. The salinized soil roadbed structure of claim 7, wherein the geomembrane comprises an upper layer, a middle layer and a lower layer which are laid in sequence; the upper layer structure is a glass fiber net or a loose-handling glass fiber net; the middle layer is a polyethylene waterproof ventilated membrane with the pore diameter of 0.1-10 mu m; the lower layer is a loose disposal glass fiber net.