A method and apparatus for subgrade deformation control in permafrost regions

Abstract

The application relates to a method and device for inhibiting subgrade deformation in a frozen soil area, and the method comprises the following steps: performing geological exploration on the frozen soil area to obtain exploration data; determining a thawing scheme according to the exploration data; blocking water and heat transfer between a road area and other areas of the frozen soil area according to the thawing scheme; heating an ice layer of the road area of the frozen soil area to thaw the ice layer; discharging water generated by thawing the ice layer through a drainage mechanism; and using a gravel cushion layer in combination with impact rolling on the road area of the frozen soil area to obtain a dense soil layer subgrade. Compared with the prior art, the application has the advantages of high stability and high construction quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of road engineering, in particular to a method and device for subgrade deformation inhibition in permafrost regions. BACKGROUND

[0002] Under the influence of extreme climate, the melting of frozen soil layer (including ice-rich soil layer and soil-ice layer) in permafrost regions leads to subgrade settlement, which greatly affects the driving safety of highways in permafrost regions. Existing permafrost subgrade treatment technologies mainly focus on protecting frozen soil, and can be divided into radiation control, convection control and heat conduction control according to engineering mechanism. These methods mainly reduce or maintain the temperature to achieve the protection of frozen soil.

[0003] With the intensification of high-temperature weather, permafrost is continuously degrading, and the permafrost prevention and treatment technology with the core idea of protecting frozen soil is relatively passive. The pre-melting settlement technology of high-ice-content frozen soil subgrade is an effective means to prevent frozen soil subgrade, which is based on the core idea of changing the protection of frozen soil to the treatment of frozen soil to achieve active protection of frozen soil diseases.

[0004] The current common means is to directly melt the ice in the frozen soil subgrade, and after drainage, grouting is used to fill the cavities or cracks formed after the ice in the frozen soil subgrade melts. However, the ice layer melting effect of this technology is difficult to guarantee, and the grouting is difficult to compact the cavities and cracks in the later stage, which affects the stability of the subgrade. SUMMARY

[0005] The purpose of the present application is to overcome the defects of unstable ice melting effect in the prior art and provide a method and device for subgrade deformation inhibition in permafrost regions.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] A method for subgrade deformation inhibition in permafrost regions, comprising the following steps:

[0008] S1: conducting geological exploration on the permafrost region to obtain exploration data;

[0009] S2: determining an ice melting scheme according to the exploration data;

[0010] S3: blocking the water and heat transfer between the road area and other areas of the permafrost region according to the ice melting scheme;

[0011] S4: heating the ice layer of the road area of the permafrost region to melt the ice layer;

[0012] S5: draining the water generated by melting the ice layer in step S4 through a drainage mechanism;

[0013] S6: using a gravel cushion layer in combination with impact rolling in the road area of the permafrost region to obtain a compacted soil layer subgrade.

[0014] Further, the method further comprises the following steps:

[0015] S7: verifying the deformation suppression degree of the roadbed by checking the compactness, water content and ice layer distribution of the compacted soil layer of the roadbed.

[0016] Further, the survey data comprises climate conditions, geological exploration results, underground ice distribution in permafrost regions in different seasons, and the ice melting scheme comprises a heat source, ice melting depth and ice melting speed.

[0017] In the second aspect of the present application, a device for suppressing the deformation of a roadbed in a permafrost region is used to implement any one of the above methods for suppressing the deformation of a roadbed in a permafrost region. The device comprises a continuous wall, an electrically heated drain board and a drainage mechanism. The permafrost region comprises, from top to bottom, an overlying soil layer, an ice-rich soil layer, a soil-ice-containing layer and a permafrost layer. The continuous wall is arranged around the permafrost region, completely separating the overlying soil layer, the ice-rich soil layer and the soil-ice-containing layer, and is inserted into the permafrost layer. The electrically heated drain board is inserted and passes through the overlying soil layer and the ice-rich soil layer, and stops in the soil-ice-containing layer while being exposed from the overlying soil layer. The electrically heated drain board is uniformly distributed in the permafrost region. The drainage mechanism is arranged on the surface of the overlying soil layer and is used to drain water generated when the electrically heated drain board is working.

[0018] Further, the continuous wall comprises a composite geomembrane and a foamed lightweight soil, and the foamed lightweight soil is filled in the composite geomembrane to form the continuous wall body.

[0019] Further, the foamed lightweight soil has a density of 800 kg / m 3 ~ 1200 kg / m 3 , a compressive strength of 0.3 MPa ~ 20 MPa, a thermal conductivity of 0.08 W / m·K ~ 0.3 W / m·K, and a bubble volume content of greater than 70%; and the composite geomembrane has a density of greater than 900 g / m 2 , a bursting strength of greater than 2.6 kN, a permeability coefficient of less than 2×10 -12 cm / s, a longitudinal and transverse tensile strength of greater than 800 N, and a corresponding elongation of less than 100%.

[0020] Further, the electrically heated drain board comprises a drain board, an electric heating wire and a filter cloth, the drain board is wrapped by at least two layers of filter cloth, and the electric heating wire is arranged between the filter cloths.

[0021] Further, the drain board has a high-temperature tensile strength of greater than 1.6 kN / 10 cm, a longitudinal water permeability of greater than 30 cm 3 / s at 100℃, and a normal-temperature longitudinal water permeability of greater than or equal to 40 cm 3 / s; the filter cloth has a permeability coefficient k 20 > 5.0×10 -3 cm / s; and the electric heating wire can continuously work under a power of 150 kW.

[0022] Furthermore, the drainage mechanism includes a sealing ditch, a drainage cushion, a sealing membrane and a vacuum pump. The sealing ditch is arranged above the continuous wall to fill the space between the top of the continuous wall and the surface of the overlying soil layer. The drainage cushion covers all the electric heating drainage boards. The sealing membrane covers the sealing ditch and the drainage cushion and is connected to the vacuum pump to form a sealed environment. When the vacuum pump and the electric heating drainage board are working, the water generated in the heated frozen soil area is pumped into the sealing ditch and the drainage cushion through the electric heating drainage board, and then discharged through the vacuum pump.

[0023] Furthermore, the drainage cushion layer is made of medium-coarse sand, has a thickness of 50 cm, and a permeability coefficient greater than or equal to 10. -2 cm / s, mud content is less than or equal to 3%, and particle size is 0cm~5cm; three layers of sealing membrane are set, and the vacuum degree under the membrane is maintained at above 650mmHg. The sealing membrane includes vacuum filter tubes under the membrane, and the spacing between the vacuum filter tubes under the membrane is 5m, the filter tube diameter is 50mm, and it is buried in the middle of the drainage cushion layer.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) The present invention controls the thawing and settling of frozen soil by measuring and planning the frozen soil area, thereby protecting the quality of the roadbed while avoiding affecting the frozen soil in the surrounding areas of the road. Through the pre-thawing, drainage, and compaction deformation processes, the moisture in the frozen soil area of ​​the road is removed, reducing the impact of subsequent water vapor exchange on the roadbed, avoiding the re-infiltration of water vapor, and making the roadbed have a longer stable period, making it easier to control the construction quality.

[0026] 2) The present invention uses the physical isolation and penetration barrier effect of the composite geomembrane to block the lateral water seepage and reduce the infiltration of water vapor. It uses foam lightweight soil backfill to form a closed continuous wall, effectively preventing heat conduction, eliminating the influence of heat exchange, and ensuring the deformation stability of the roadbed area. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of a method flow in an embodiment of the present invention.

[0028] Figure 2 This is a schematic structural diagram of the electric heating drainage board of the present invention.

[0029] Figure 3 It is a top view of the layout of the device of the present invention.

[0030] Figure 4 Detailed layout diagram of the device of the present invention.

[0031] Figure 5 Schematic diagram of the structure of the continuous wall.

[0032] Figure 6A flow chart of details for method practice.

[0033] Figure Marked Description: 1, continuous wall, 11, composite geomembrane, 12, foam light soil, 2, electric heating drainage plate, 21, drainage plate, 22, heating wire, 23, filter cloth, 31, overburden, 32, ice-rich soil layer, 33, ice-containing soil layer, 34, permafrost layer, 41, sealing ditch, 42, drainage cushion, 43, sealing membrane, 44, vacuum pump. DETAILED DESCRIPTION

[0034] The present application will be described in detail below with reference to the accompanying drawings and specific examples. The present embodiment is implemented on the premise of the technical solution of the present application, and gives a detailed implementation and specific operation process, but the protection scope of the present application is not limited to the following examples.

[0035] The present application is a method and device for inhibiting subgrade deformation in permafrost regions, as shown in the figure, comprising the following steps: Figure 1

[0036] S1: geological exploration is carried out on the permafrost region to obtain survey data;

[0037] S2: determining the ice melting scheme according to the survey data;

[0038] S3: blocking the water and heat transfer between the road area and other areas of the permafrost region according to the ice melting scheme;

[0039] S4: heating the ice layer of the road area of the permafrost region to melt the ice layer;

[0040] S5: draining the water produced by melting the ice layer in step S4 through the drainage mechanism;

[0041] S6: using gravel cushion combined with impact rolling on the road area of the permafrost region to obtain a dense soil subgrade.

[0042] In order to test the inhibitory effect of the inhibitory method of the present application, the following steps can be used for verification:

[0043] S7: verifying the degree of subgrade deformation by testing the compactness, water content and ice layer distribution of the dense soil subgrade.

[0044] At the same time, as shown in the figure, Figure 4 ​As shown, the present invention proposes a device for suppressing roadbed deformation in frozen soil areas, including a continuous wall 1, an electric heating drainage board 2 and a drainage mechanism. The frozen soil area includes an overlying soil layer 31, an ice-rich soil layer 32, an ice layer containing soil 33, and a permafrost layer 34 from the surface downward. The continuous wall 1 is arranged around the frozen soil area, completely separating the overlying soil layer 31, the ice-rich soil layer 32 and the ice layer containing soil 33, and inserted into the permafrost layer 34. The electric heating drainage board 2 is inserted into and passes through the overlying soil layer 31 and the ice-rich soil layer 32, and stops in the ice layer containing soil 33, while being exposed from the overlying soil layer 31. The electric heating drainage board 2 is evenly distributed in the frozen soil area. The drainage mechanism is arranged on the surface of the overlying soil layer 31, and is used to discharge water generated by heating the frozen soil area when the electric heating drainage board 2 is working.

[0045] like Figure 6 As shown, the specific implementation process of the present invention is:

[0046] Combined with local meteorological conditions and geological exploration results, determine the distribution of ground ice in different seasonal frozen ground layers, including the ice-rich soil layer 32, the ice-bearing soil layer 33, and the permafrost layer 34. Meteorological conditions can be referenced to local weather station data, and geological exploration can be conducted using geophysical methods such as high-density electrical methods and transient Rayleigh wave methods to explore the geological conditions of the area to be reinforced.

[0047] Based on the distribution of underground ice in the frozen ground layers in different regions in step S1, the heat source, ice melting depth, and ice melting rate for the thawing process are determined. The ice melting depth is set to a certain distance below the permafrost layer 34, and the ice melting rate is adjusted by adjusting the power of the heat source resistance wire 12, the spacing between the electric heating drain plates 1, and the number of turns of the resistance wire 12.

[0048] The diaphragm wall 1 is designed to block the water and heat exchange between the roadbed reinforcement area and other areas, and provide a closed boundary for the vacuum preloading consolidation drainage S5. Figure 5 As shown, the composite geomembrane-foam lightweight soil continuous wall 1 includes a continuous wall 1 formed by a composite geomembrane 11 and foam lightweight soil backfill; the composite geomembrane 1 blocks lateral water penetration by physically isolating water penetration; the continuous wall 1 formed by the foam lightweight soil backfill is formed by foam lightweight soil backfill. The foam lightweight soil has the characteristics of self-leveling, density and thermal insulation. The foam lightweight soil is used to backfill the trench to form a closed continuous wall. The construction is simple and can effectively prevent heat conduction. During the construction process of the composite geomembrane-foam lightweight soil continuous wall 1, the parameters of S1 and S2 are set to determine the boundary and depth of the area to be reinforced. After excavation, the composite geomembrane 11 is laid, and then the foam lightweight soil is backfilled to form the continuous wall 1 formed by the foam lightweight soil backfill. The material of the composite geomembrane-foam lightweight soil continuous wall 1 should meet the following requirements: the density of the foam lightweight soil should be between 800kg / m 3 ~1200kg / m 3, the compressive strength is between 0.3MPa and 20MPa, the thermal conductivity is between 0.08W / m·K and 0.3W / m·K, and the bubble volume content is greater than 70%; the density of the composite geomembrane is greater than 900g / m 2 , the top breaking strength (CBR) is greater than 2.6kN, the permeability coefficient is less than 2×10 -12 cm / s, the longitudinal and transverse tensile strength is greater than 800N, and the corresponding elongation is less than 100%.

[0049] After the construction of the continuous wall 1 is completed, the ice in the frozen soil layer is melted by using the electric heating drainage plate 2; the electric heating drainage plate 2 can provide a heat source for the melting of the frozen soil layer and a drainage channel for the vacuum preloading. As shown in Figure 2 , the electric heating drainage plate 2 includes a drainage plate 21, an electric heating wire 22 and a filter cloth 23; the drainage plate 21 is wrapped by two layers of filter cloth 23, and the electric heating wire 22 is arranged between the filter cloths 23; the drainage plate 21 should be made of high-temperature resistant material, the high-temperature tensile strength requirement is greater than 1.6kN / 10cm, the longitudinal water permeability at 100℃ should be greater than 30cm 3 / s, the longitudinal water permeability at normal temperature is not less than 40cm 3 / s, and it does not break after being repeatedly folded for 5 times; the permeability coefficient k 20 of the filter cloth 13 is greater than 5.0×10 -3 cm / s; the electric heating wire 22 should meet the continuous working condition under the power of 150kW. As shown in Figure 3 , the electric heating drainage plate 2 is uniformly arranged in the road area to achieve the effect of uniform heating and fully melt the ice layer.

[0050] The drainage mechanism includes a sealing ditch 41, a drainage cushion layer 42, a sealing film 43 and a vacuum pump 44; the sealing ditch 41 is arranged above the continuous wall 1 to fill the space between the top of the continuous wall 1 and the surface of the overlying soil layer 31; the drainage cushion layer 42 covers all the electric heating drainage plates 2; the sealing film 43 covers the sealing ditch 41 and the drainage cushion layer 42 and is connected with the vacuum pump 44 to form a sealed environment; when the vacuum pump 44 and the electric heating drainage plate 2 work, the water generated by heating the frozen soil area is extracted to the sealing ditch 41 and the drainage cushion layer 42 through the electric heating drainage plate 2 and then is discharged through the vacuum pump 44. The material of the drainage cushion layer 42 is medium-coarse sand, and the thickness of the cushion layer is 50cm; the medium-coarse sand cushion layer is required to have good permeability, the permeability coefficient is greater than or equal to 10 -2 cm / s, the silt content is less than or equal to 3%, and the particle size is 0cm-5cm; the sealing film 43 is arranged in three layers, the under-film vacuum degree is maintained above 650mmHg, and the sealing film 43 includes an under-film vacuum filter pipe; the spacing of the under-film vacuum filter pipe is 5m, the diameter of the filter pipe is 50mm, and the filter pipe is buried in the middle of the drainage cushion layer 42. Before the drainage mechanism works, the vacuum degree needs to be tested; after the vacuum degree meets the construction requirements, the drainage mechanism is started to discharge the water generated by the melting of the ice layer.

[0051] Further, the gravel cushion is used to cooperate with the impact roller to reinforce and compact the drainage cushion 42. Under the action of the mechanical impact force, the soil particles are rearranged, which can significantly improve the bearing capacity and stability of the soil.

[0052] The earth exploration method, such as the high-density electrical method and the transient Rayleigh wave method, can be used for large-scale detection, and the drilling results are combined for comprehensive evaluation, and the construction quality of the continuous wall 1 is tested.

[0053] The above describes the preferred embodiments of the present application in detail. It should be understood that those skilled in the art can make many modifications and changes without creative labor according to the concept of the present application. Therefore, any technical solution obtained by logical analysis, reasoning or limited experiment on the basis of the prior art according to the concept of the present application should be within the protection scope determined by the claims.

Claims

1. A method for subgrade deformation inhibition in permafrost regions, characterized by, The method comprises the following steps: S1: geological exploration is conducted on the frozen soil area to obtain survey data; S2: an ice melting scheme is determined according to the survey data; S3: water and heat transfer between the road area of the frozen soil area and other areas is blocked according to the ice melting scheme; S4: the ice layer of the road area of the frozen soil area is heated to melt the ice layer; S5: water generated in the melting of the ice layer in step S4 is discharged through a drainage mechanism; S6: a dense soil layer subgrade is obtained by using a gravel cushion in combination with impact rolling on the road area of the frozen soil area.

2. A method for subgrade deformation control in permafrost regions according to claim 1, characterized in that, The method further comprises the following steps: S7: the degree of deformation suppression of the subgrade is verified by checking the compactness, water content and ice layer distribution of the dense soil layer subgrade.

3. The method for subgrade deformation control in permafrost regions according to claim 1, characterized in that, The survey data includes climate conditions, geological exploration results and underground ice distribution in different seasons of the frozen soil area, and the ice melting scheme includes heat source, ice melting depth and ice melting speed.

4. An apparatus for subgrade deformation inhibition in permafrost regions, characterized by, The device is used to implement the method for suppressing deformation of a subgrade in a frozen soil area according to any one of claims 1-3, and the device comprises a continuous wall (1), an electrically heated drainage plate (2) and a drainage mechanism, the frozen soil area comprises, from top to bottom, an overlying soil layer (31), an ice-rich soil layer (32), a soil-ice-containing layer (33), a permafrost layer (34), the continuous wall (1) is arranged around the frozen soil area, completely separates the overlying soil layer (31), the ice-rich soil layer (32) and the soil-ice-containing layer (33), and is inserted into the permafrost layer (34), the electrically heated drainage plate (2) is inserted into and passes through the overlying soil layer (31) and the ice-rich soil layer (32), and stops in the soil-ice-containing layer (33) while being exposed from the overlying soil layer (31), the electrically heated drainage plate (2) is uniformly distributed in the frozen soil area, and the drainage mechanism is arranged on the surface of the overlying soil layer (31) and is used to discharge water generated when the electrically heated drainage plate (2) heats the frozen soil area.

5. A device for subgrade deformation control in permafrost regions according to claim 4, characterized in that, The continuous wall (1) comprises a composite geomembrane (11) and a foamed lightweight soil (12), and the foamed lightweight soil (12) is filled in the composite geomembrane (11) to form a continuous wall body.

6. A device for subgrade deformation control in permafrost regions according to claim 5, characterized in that, The density of the foamed lightweight soil (12) is 800 kg / m 3 ~ 1200 kg / m 3 , the compressive strength is 0.3 MPa ~ 20 MPa, the thermal conductivity is 0.08 W / m·K ~ 0.3 W / m·K, and the bubble volume content is greater than 70%; the density of the composite geomembrane (11) is greater than 900 g / m 2 , the bursting strength is greater than 2.6 kN, the permeability coefficient is less than 2 x 10 -12 cm / s, the tensile strength in the longitudinal and transverse directions is greater than 800 N, and the corresponding elongation at break is less than 100%.

7. A device for subgrade deformation control in permafrost regions according to claim 4, characterized in that, The electrically heated drainage plate (2) comprises a drainage plate (21), an electric heating wire (22) and filter cloth (23), the drainage plate (21) is wrapped by at least two layers of filter cloth (23), and the electric heating wire (22) is arranged between the filter cloth (23).

8. A device for subgrade deformation control in permafrost regions according to claim 7, characterized in that, The high temperature tensile strength of the drainage plate (21) is greater than 1.6 kN / 10 cm, the longitudinal water flow at 100 ℃ is greater than 30 cm 3 / s, the normal temperature longitudinal water flow is greater than or equal to 40 cm 3 / s; the permeability coefficient k 20 of the filter cloth (23) is greater than 5.0×10 -3 cm / s; and the electric heating wire (22) can continuously work under the condition of 150 kW power.

9. A device for subgrade deformation control in permafrost regions according to claim 4, characterized in that, The drainage mechanism comprises a sealed trench (41), a drainage cushion (42), a sealing membrane (43) and a vacuum pump (44), the sealed trench (41) is arranged above the continuous wall (1) and fills the space between the top of the continuous wall (1) and the surface of the overlying soil layer (31), the drainage cushion (42) covers all the electrically heated drainage plates (2), the sealing membrane (43) covers the sealed trench (41) and the drainage cushion (42) and is connected with the vacuum pump (44) to form a sealed environment, and when the electrically heated drainage plate (2) and the vacuum pump (44) work, water generated by heating the frozen soil area is extracted to the sealed trench (41) and the drainage cushion (42) through the electrically heated drainage plate (2) and is then discharged through the vacuum pump (44).

10. A device for subgrade deformation control in permafrost regions according to claim 9, characterized in that, The drainage cushion layer (42) is made of medium-coarse sand, has a thickness of 50 cm, and a permeability coefficient greater than or equal to 10. -2 cm / s, mud content is less than or equal to 3%, and particle size is 0cm to 5cm; the sealing membrane (43) is provided with three layers, and the vacuum degree under the membrane is maintained at above 650mmHg. The sealing membrane (43) includes a vacuum filter tube under the membrane, and the spacing between the vacuum filter tubes under the membrane is 5m, the filter tube diameter is 50mm, and the filter tube is buried in the middle of the drainage cushion layer (42).

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