CN109811748B - A kind of highway subgrade treatment method in permafrost area - Google Patents

Abstract

The invention discloses a method for treating a highway roadbed in a permafrost area, comprising the following steps: a. pre-thaw frozen soil roadbed within the deep-freezing line; b. excavate all thawed soil; c. lay a thick layer at the bottom of the excavation layer Grain soil and anti-filter layer, and lay lime-soil water-repellent layer and gravel dilatation layer on both sides at the same time; d. Fill layer by layer with activated magnesium oxide carbonized and solidify silt soil and compact it; e. A layer of coarse-grained soil layer containing XPS insulation board is set below; f. Waterproof foot guards are set on both sides of the embankment. The invention fully combines the subgrade pre-thaw, replacement treatment and soft soil carbonization and solidification technology in permafrost areas, effectively strengthens the frozen soil subgrade, well avoids engineering problems such as subgrade soil refreezing and frost heave, and further reduces the risk of subgrade failure. The uniform settlement greatly reduces the secondary disease problem of the expressway in the cold area. The method has the advantages of economy and environmental protection, safety and efficiency, strong controllability and easy operation.

Description

A kind of highway subgrade treatment method in permafrost area

technical field

The invention relates to the fields of geotechnical engineering and road engineering, in particular to a method for treating highway roadbeds in permafrost areas.

Background technique

China is the third largest permafrost country in the world. Its permafrost area accounts for about 22.3% of the country's land area, while the seasonally frozen soil area accounts for about 53.5%. It has a significant impact on my country's transportation infrastructure. In recent years, with the economic development of cold regions, the requirements for transportation and infrastructure construction in permafrost regions have gradually increased, and the railway and ordinary highway network can no longer carry the existing transportation volume; Fragile ecological circle, minimize human damage, closed highway is the best choice. However, the construction of highways in permafrost areas is a world problem. Compared with ordinary highways, the width of the road surface increases, the heat absorption increases significantly, the thermal resistance effect is seriously damaged, the technical content is doubled, and the stability of highway subgrades is greatly affected. challenges, exposing severe road transportation safety and later operation problems.

The secondary diseases such as frost heave, thaw, and pulping are common on highways. The fundamental reason is the fluctuation of the upper and lower limits of the frozen soil caused by the temperature change of the frozen soil subgrade caused by climate change or human interference. The existing design principles mainly adopt thermal insulation measures, and use the thermal insulation effect to limit or delay the downward movement of the upper limit of permafrost, thereby protecting the permafrost. However, this technology is still immature, and it cannot change the development trend of the heat budget of the permafrost under the subgrade, and it cannot eliminate the problem of freezing damage to the subgrade from the root. Therefore, some special subgrade structures are adopted, such as typical structures such as hot rods, ventilation pipes, flakes, and heat insulation layers. Most of these treatment methods are aimed at the rectification and disease control of existing second-level and lower roads in permafrost areas, mainly focusing on "road disease control" rather than "road disease prevention". This also ignores the interaction performance of the permafrost environment in the cold region of the national highway network, the later service performance and operational life issues. Therefore, the treatment technology that can effectively prevent the "permafrost disease problem in cold regions", solve the problem of subgrade freezing damage in cold regions from the root, and ensure the stability of highway subgrade performance in permafrost regions needs to be improved.

The replacement filling method is simple in construction and has a wide range of applications, but it is difficult to eliminate or reasonably control the frost heave deformation of the subgrade, and it needs to be replaced in all or part of the freezing depth, which requires higher fillers. Coarse particles are often used as permafrost subgrade fillers, but actual engineering shows that they can only reduce the frost heave of subgrade soil, and at the same time, moisture migration may occur; after repeated freezing and thawing, the water content of coarse particles fillers will increase, which will induce subgrade frost heave , pulping, cracking, subsidence and other diseases will pose a certain threat to the durability and stability of the highway. Therefore, it is an inevitable trend to improve roadbed fillers, that is, to improve common roadbed fillers in permafrost areas into materials with low moisture content and non-frost heave sensitivity. There are large areas of swamps in the northeastern region of my country. The reasons for their formation are the cold and wet climate, the development of permafrost, and the low and equal terrain. The swamps in permafrost areas are mainly composed of peat soil and silt soil, which are characterized by loose soil, extremely high moisture content, low strength and low hardness, so they cannot be used as roadbed fillers. How to effectively utilize peat soil and silt soil in swampy areas, fully realize resource utilization and "turn waste into treasure" is an engineering problem that geotechnical engineers need to solve urgently.

SUMMARY OF THE INVENTION

Technical problem: The purpose of the present invention is to provide a method for treating highway subgrades in permafrost areas, in order to overcome the deficiencies and defects of the method for treating highway subgrades in permafrost areas, and at the same time, in order to effectively solve the problem of resource utilization of swampy land in permafrost areas, comprehensive This paper proposes a treatment method for highway subgrade in permafrost areas, which can significantly improve subgrade fillers, achieve road disease prevention, limit subgrade soil frost heave from the root cause, improve subgrade stability and durability, and enhance the service of frozen soil highways in cold regions. performance.

Technical scheme: a method for treating highway roadbeds in permafrost areas of the present invention, the treatment method comprises the following steps:

a. According to the subgrade survey report, determine the freezing depth line of the subgrade in cold regions; select the pre-thaw method according to the freezing depth and site conditions, and pre-thaw the subgrade frozen soil above the freezing depth line, that is, within the excavation area from the coarse-grained layer to the surface. all permafrost;

b. Excavate all frozen soil in the thawing zone and transport it to the storage place;

c. Lay a layer of bottom coarse-grained soil at the bottom of the excavation layer, and then lay a layer of reverse filter layer; at the same time, lay a water-insulating layer and a dilatation layer on both sides of the excavation area;

d. Fill layer-by-layer silt soil or peat soil that has been carbonized and solidified by activated magnesium oxide, and tamp it for reinforcement;

e. Densely fill the embankment and set up a layer of coarse-grained soil filling containing XPS insulation layer below the pavement structure;

f. Set up water-proof foot guards on both sides of the embankment.

in,

The subgrade frozen soil in the pre-thawed deep line shall be constructed in winter.

The excavation of all the permafrost in the thawing area is to continuously excavate the thawed soil day and night after the permafrost has thawed, and the slope ratio of the corresponding excavation area is 1:0.5-1.

A layer of bottom coarse-grained soil is laid at the bottom of the excavation layer, and the filling height is not less than 50cm.

The anti-filter layer is made of pebbles, crushed stones and sand fillers, and is laid in three layers in descending order of particle size.

The water-repellent layer is laid on both sides of the excavation area, and the water-repellent foot protection on both sides of the embankment soil is made of lime and clay, the corresponding volume ratio is controlled at 3-4:6-7, and the laying thickness is 30-50cm; The slope toe ratio of the water-proof foot protection on both sides of the soil is 1:3 to 5.

The dilatation layer is filled with sand and gravel, and the laying thickness is 30-50 cm.

The particle size of the carbonized and solidified silt soil or peat soil is controlled within the range of 1 cm to 5 cm, and particles with small particle size and high packing density are suitable.

The silt soil or peat soil that has been carbonized and solidified by activated magnesium oxide is filled layer by layer, and the height of one filling is 50-100 cm, and the next filling is carried out after ensuring sufficient compaction.

The XPS thermal insulation layer is staggered and spliced with a single-layer thermal insulation board, and the size of the thermal insulation board is uniformly 200cm × 100cm × 5cm; A coarse-grained soil filling layer shall be built, and the filling height shall not be less than 50cm, and a layer of XPS insulation layer shall be laid in the middle of the coarse-grained soil filling layer.

Beneficial effects: The present invention fully combines the traditional, simple and easy pre-thaw method, replacement method and new activated magnesium oxide carbonization and solidification technology, and comprehensively solves the problem of swampy land resource utilization in permafrost regions and cold regions by improving roadbed fillers. Problems such as difficult to deal with highway subgrade. Because carbon dioxide is continuously consumed in the carbonization process, it has important environmental protection significance. In addition, the use of carbonized and solidified silt soil or peat soil filler and auxiliary setting of water-proof layer, dilatation layer and thermal insulation board can effectively avoid the frost heave and thawing of subgrade soil, realize the prevention of road diseases, and limit the frost heave of subgrade soil from the root cause. problems, improve the stability and durability of the roadbed, and directly enhance the service performance of the permafrost expressway in cold regions.

Description of drawings

Fig. 1 is a schematic diagram of a method for treating highway subgrades in permafrost areas;

In the figure, carbonized and solidified silt soil or peat soil 1, water-proof layer 2, dilatation layer 3, reverse filter layer 4, bottom coarse-grained soil 5, water-proof foot protection 6, coarse-grained soil filling layer 7, XPS insulation layer Thermal layer 8, pavement structure 9, embankment fill 10, freezing depth line 11.

Detailed ways

The technical solutions of the present invention are described in detail below, but the protection scope of the present invention is not limited to the embodiments.

Example 1:

A method for treating frozen soil highway subgrade in cold regions is shown in Figure 1. It is characterized in that, comprises the following steps:

a. First, according to the subgrade survey report, determine the freezing depth line of the subgrade in cold areas; select the appropriate method according to the freezing depth, site conditions, etc., choose winter construction, and preferentially use the electric heating method or the steam method to pre-thaw the subgrade frozen soil above the freezing depth line 11 , that is, all frozen soils in the excavation area from the coarse-grained soil 5 to the surface.

b. Use an excavator to excavate all the frozen soil in the thawing area, and transport the thawed soil to the storage site with a truck, and the corresponding excavation slope is 1:0.5; Melt the soil to avoid freezing again.

c. Lay the bottom coarse-grained soil 5 at the bottom of the excavation layer, and its filling height is 50cm, and then use pebble, gravel and sand filler, and lay the anti-filter layer 4 in three layers according to the order of particle size from large to small; On both sides of the excavation area, lay lime-soil water-insulating layer 2 and gravel expansion layer 3 along the excavation surface, wherein the volume ratio of lime and clay in the lime-soil mixture is 3:7; Both are 30cm.

d. Fill the silt or peat soil 1 after carbonization and solidification layer by layer. The carbonization raw material is taken from the swamp area of the frozen land. The particle size of the carbonized and solidified particles is controlled at about 1cm-5cm. The filling height is 50cm each time, and the next filling will be carried out after sufficient compaction, and the cycle operation will be carried out until the end of the subgrade filling.

e. Densely fill the embankment and fill the soil 10, and start to level the road surface and fill the coarse-grained soil filling layer 7 at 100cm below the road structure 9. The filling height is 70cm, and set in the middle of the coarse-grained soil filling layer 7. A layer of XPS heat insulation layer 8; the XPS heat insulation layer 8 is formed by staggered splicing of insulation boards with a size of 200×100×5cm.

f. Set up lime-soil water-proofing feet 6 on both sides of the embankment respectively, and the volume ratio of lime-soil mixture lime to clay is also 3.5:6.5; the slope ratio of lime-soil water-proofing feet 6 is 1:3.

Example 2:

A method for treating frozen soil highway subgrade in cold regions is shown in Figure 1. It is characterized in that, comprises the following steps:

a. First, according to the subgrade survey report, determine the freezing depth line of the subgrade in cold areas; select the appropriate method according to the freezing depth, site conditions, etc., choose winter construction, and preferentially use the electric heating method or the steam method to pre-thaw the subgrade frozen soil above the freezing depth line 11 , that is, all frozen soils in the excavation area from the coarse-grained soil 5 to the surface.

b. Use an excavator to excavate all the frozen soil in the thawing area, and transport the thawed soil to the storage site with a truck, and the corresponding excavation slope is 1:0.75; Melt the soil to avoid freezing again.

c. Lay the bottom coarse-grained soil 5 at the bottom of the excavation layer, and its filling height is 75cm, and then use pebble, crushed stone and sand filler, and lay the anti-filter layer 4 in three layers according to the order of particle size from large to small; On both sides of the excavation area, lay lime-soil water-insulating layer 2 and gravel expansion layer 3 along the excavation surface, in which the volume ratio of lime and clay in the lime-soil mixture is 3.5:6.5; Both are 40cm.

d. Fill the silt or peat soil 1 after carbonization and solidification layer by layer. The carbonization raw material is taken from the swamp area of the frozen land. The particle size of the carbonized and solidified particles is controlled at about 1cm-5cm. The filling height is 75cm each time, and the next filling will be carried out after sufficient compaction, and the cycle operation will be carried out until the end of the subgrade filling.

e. Densely fill the embankment and fill the soil 10, and start to level the road at 90cm below the road structure 9 and fill the coarse-grained soil filling layer 7, the filling height is 60cm, and set in the middle of the coarse-grained soil filling layer 7 A layer of XPS heat insulation layer 8; the XPS heat insulation layer 8 is formed by staggered splicing of insulation boards with a size of 200×100×5cm.

f. Set up lime-soil water-proof feet 6 on both sides of the embankment respectively, and the volume ratio of lime-soil mixed with lime to clay is also 3:7; the slope ratio of lime-soil water-proof feet 6 is 1:4.

Example 3:

A method for treating frozen soil highway subgrade in cold regions is shown in Figure 1. It is characterized in that, comprises the following steps:

a. First, according to the subgrade survey report, determine the freezing depth line of the subgrade in cold areas; select the appropriate method according to the freezing depth, site conditions, etc., choose winter construction, and preferentially use the electric heating method or the steam method to pre-thaw the subgrade frozen soil above the freezing depth line 11 , that is, all frozen soils in the excavation area from the coarse-grained soil 5 to the surface.

b. Use an excavator to excavate all the frozen soil in the thawing area, and transport the thawed soil to the storage site with a truck, the corresponding excavation slope is 1:1; the excavation work should be continuously excavated day and night after the frozen soil thaws Melt the soil to avoid freezing again.

c. Lay the bottom coarse-grained soil 5 at the bottom of the excavation layer, and its filling height is 100cm, and then use pebble, crushed stone and sand filler, and lay the anti-filter layer 4 in three layers according to the order of particle size from large to small; On both sides of the excavation area, lay lime-soil water-insulating layer 2 and gravel expansion layer 3 along the excavation surface, wherein the volume ratio of lime and clay in the lime-soil mixture is 4:6; Both are 50cm.

d. Fill the silt or peat soil 1 after carbonization and solidification layer by layer. The carbonization raw material is taken from the swamp area of the frozen land. The particle size of the carbonized and solidified particles is controlled at about 1cm-5cm. The filling height is 100cm each time, and the next filling will be carried out after sufficient compaction, and the cycle operation will be carried out until the end of the subgrade filling.

e. Densely fill the embankment and fill the soil 10, and start to level the road at 80cm below the pavement structure 9 and fill the coarse-grained soil filling layer 7 with a filling height of 50cm, and set it in the middle of the coarse-grained soil filling layer 7 A layer of XPS heat insulation layer 8; the XPS heat insulation layer 8 is formed by staggered splicing of insulation boards with a size of 200×100×5cm.

f. Set up lime-soil water-proof feet 6 on both sides of the embankment respectively, and the volume ratio of lime-soil mixed with lime to clay is also 4:6; the slope ratio of lime-soil water-proof feet 6 is 1:5.

It should be pointed out that the above are only the preferred embodiments of the present invention; for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can also be made, and these improvements and modifications can also be It should be regarded as the protection scope of the present invention.

Claims (8)

1. a method for treating highway roadbed in permafrost regions, is characterized in that, this processing method comprises the following steps: a. According to the subgrade survey report, determine the freezing depth line of the subgrade in cold regions; select the pre-thaw method according to the freezing depth and site conditions, and pre-thaw the subgrade frozen soil above the freezing depth line (11), that is, the coarse-grained soil (5) to the surface All permafrost within the excavation area of the range; b. Excavate all frozen soil in the thaw zone and transport it to the storage area; c. Lay a layer of bottom coarse-grained soil (5) at the bottom of the excavation layer, and then lay a layer of reverse filter layer (4); at the same time, lay a water-insulating layer (2) and an expansion layer (3) on both sides of the excavation area ; d. Fill the silt soil or peat soil (1) which has been carbonized and solidified by activated magnesium oxide layer by layer, and ram it for reinforcement; e. Dense embankment filling (10) and a coarse-grained soil filling layer (7) containing an XPS thermal insulation layer (8) below the pavement structure (9); f. Set water-proof feet (6) on both sides of the embankment; The XPS thermal insulation layer (8) is staggered and spliced with single-layer thermal insulation boards, and the size of the thermal insulation boards is uniform; Level the road surface, fill with a coarse-grained soil filling layer (7), the filling height is not less than 50cm, and lay a layer of XPS insulation layer (8) in the middle of the coarse-grained soil filling layer (7). 2 . The method for treating highway subgrades in permafrost areas according to claim 1 , wherein the subgrade frozen soil in the pre-thaw deep line is selected for winter construction. 3 . 3. a kind of permafrost area highway subgrade treatment method according to claim 1, is characterized in that, described excavating all frozen soil in the thawing zone, is to continuously excavate the thawing soil day and night after the permafrost thaws, corresponding to thawed soil. The slope ratio of the excavation area is 1:0.5~1. 4 . The method for treating highway subgrades in permafrost areas according to claim 1 , wherein a layer of bottom coarse-grained soil ( 5 ) is laid at the bottom of the excavation layer, and the filling height is not less than 50 cm. 5 . 5 . The method for treating highway roadbeds in permafrost areas according to claim 1 , wherein the filter layer ( 4 ) is made of pebbles, crushed stones and sand fillers, and the particle size ranges from large to small. 6 . The sequence is laid in three layers. 6. A method for treating highway subgrades in permafrost areas according to claim 1, characterized in that the water barrier (2) is laid on both sides of the excavation area, and the water barrier feet (6) are arranged on both sides of the embankment. ), the mixture of lime and clay is used, the corresponding volume ratio is controlled at 3~4:6~7, the thickness of the water barrier layer is 30~50cm; the water barrier foot protection (6) on both sides of the embankment has a slope toe ratio of 1:1: 3~5. 7 . The method for treating highway subgrades in permafrost regions according to claim 1 , wherein the dilatation layer ( 3 ) is filled with sand and gravel, and the laying thickness is 30-50 cm. 8 . 8 . The method for treating highway roadbeds in permafrost regions according to claim 1 , wherein the carbonized and solidified silt soil or peat soil (1) has a particle size controlled within a range of 1 cm to 5 cm, and a Particles with small particle size and high packing density are suitable.

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