Thermal insulation and thaw collapse prevention construction test method for roadbed in deep soil-containing heavy ice layer area

Abstract

The invention provides a deep soil-containing heavy ice layer area roadbed heat insulation and thaw collapse prevention construction test method which comprises the following steps: selecting a construction road section, and calculating the burying depth of a first heat insulation layer; determining the burying depth of the second thermal insulation layer; dividing a construction road section into three groups of test areas, and respectively finishing arrangement of grating optical cables and soil pressure gauges in the three groups of tests; two groups of test areas are excavated in sequence, a first heat preservation layer and a second heat preservation layer are laid at the corresponding depths in one group of test areas, a first heat preservation layer is laid in the other group of test areas, soil pressure meters and moisture content meters are arranged in the three groups of test areas, and data are obtained. According to the test method, the burying depth of the thermal insulation layer can be quickly determined, and the thermal insulation layer is buried in the direction close to the top surface of the roadbed as far as possible on the basis of meeting the requirements of the strength of the thermal insulation layer and the thickness of a roadbed structure layer, so that the effect of the thermal insulation layer is exerted to the greatest extent, the heat absorption of the roadbed is reduced, and the stability of the roadbed is protected.

Description

Technical Field

[0001] The invention relates to the technical field of roadbed thermal insulation, and in particular to a construction test method for thermal insulation and anti-melting settlement of roadbed in a deep soil-containing heavy ice layer area. Background Art

[0002] The new technology of heat insulation and anti-thaw settlement of roadbed in deep soil-containing heavy ice layer areas is mainly applicable to highway and railway roadbed projects in high-altitude and severe cold areas, such as the Qinghai-Tibet Plateau and Tianshan Mountains; it is also applicable to important traffic arteries in seasonal frozen soil areas to ensure the stability of the roadbed when the seasons change; it also includes the construction of airport runways in cold areas to ensure the quality and safety of the runways; and the dedicated roads of large industrial and mining enterprises, such as the transportation roads of mines, oil fields and other enterprises in cold mountainous areas; in addition, it can also play a role in the construction of border roads and infrastructure in remote areas. However, the specific scope of application needs to comprehensively consider the geology, climate, engineering requirements and economic and technical conditions of the project location.

[0003] The reasonable burial depth of the insulation layer is a major issue related to whether the construction quality can be guaranteed, the usage status after completion, and the thermal insulation and anti-melting settlement effect. The deeper the burial, the worse the thermal insulation and anti-melting settlement effect, and the smaller the impact of the insulation layer on driving; the shallower the burial, the better the thermal insulation and anti-melting settlement effect, and the greater the negative impact of the insulation layer on the overall strength of the roadbed and pavement after completion. Therefore, it is necessary to determine a reasonable burial depth so that the driving stress has little or no effect on the insulation layer, and its thermal insulation and anti-melting settlement effect can meet the design requirements.

[0004] Therefore, in view of this, a test method for the construction of thermal insulation and anti-melting settlement of roadbed in deep soil-containing heavy ice layer areas is proposed to solve the above-mentioned technical problem that it is currently inconvenient to quickly understand the changes in temperature and moisture, settlement displacement and soil pressure in the thermal insulation roadbed and natural roadbed in deep soil-containing heavy ice layer areas, and thus it is impossible to quickly determine the buried depth of the insulation layer. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention proposes a test method for the construction of thermal insulation and anti-melting settlement of roadbed in deep soil-containing heavy ice areas, so as to solve the technical problem raised in the above background technology that it is currently inconvenient to quickly understand the changes in temperature and moisture, settlement displacement and soil pressure in the thermal insulation roadbed and natural roadbed in deep soil-containing heavy ice areas, and thus it is impossible to quickly determine the buried depth of the insulation layer.

[0006] To achieve the above object, the present invention provides the following technical solution, a test method for heat insulation and anti-melting settlement construction of roadbed in a thick soil-containing heavy ice layer area, comprising the following steps:

[0007] Select the construction section and calculate the burial depth of the first insulation layer;

[0008] Determine the thickness of the insulation layer and determine the embedding depth of the second insulation layer, the second insulation layer is located below the first insulation layer;

[0009] The construction section was divided into three groups of test areas with equal spacing, and the grating cables and earth pressure gauges were arranged in the three groups of test areas respectively;

[0010] Excavate two of the test areas in sequence, and lay the first insulation layer and the second insulation layer at the corresponding depth in one of the test areas, lay the first insulation layer in the other test area, and arrange earth pressure gauges and moisture content meters in the three test areas; and

[0011] Obtain data and compare it to design standards.

[0012] In a preferred embodiment, the thermal insulation layer is a polyurethane thermal insulation layer.

[0013] In a preferred embodiment, the specific steps of calculating the embedding depth of the first thermal insulation layer are:

[0014] By calculation Calculate the corresponding reasonable burial depth;

[0015] Where P is the tire pressure (MPa), d is the equivalent circular diameter of the pressure transmission surface of a single wheel (m), r is the weighted average value of the bulk density of each structural layer above the insulation layer (MN / m3), tan is the tangent function, Φ is the weighted average value of the stress diffusion angle above the insulation layer and the structural layer (°), h is the reasonable burial depth of the insulation layer (m), and б is the allowable compressive stress of the insulation layer (MPa).

[0016] In a preferred embodiment, the thickness of the thermal insulation layer is 3 to 5 cm.

[0017] In a preferred embodiment, determining the embedding depth of the second thermal insulation layer further comprises:

[0018] The second thermal insulation layer is spaced greater than 1 m from the first thermal insulation layer.

[0019] In a preferred embodiment, the specific steps of completing the arrangement of the grating optical cables and the earth pressure gauges in the three groups of test areas are:

[0020] Determine the depth of the ice surface by drilling;

[0021] Three monitoring holes were drilled at the center of each of the three test areas. Two groups of monitoring holes were drilled to a depth of 1m below the ice surface and multiple groups of grating optical cables were arranged at intervals in the detection holes. The other two groups of monitoring holes were drilled to the ice surface and water content meters and earth pressure gauges were arranged respectively.

[0022] Insert pipes of the same diameter into the drilled monitoring holes; and

[0023] The monitoring holes are backfilled with fine-grained soil.

[0024] In a preferred embodiment, the specific steps of laying the first insulation layer and the second insulation layer at corresponding depths in one group of test areas are:

[0025] The test area of ​​this group was excavated to a depth of 160 to 180 cm;

[0026] Spray the entire section of the second insulation layer and backfill to the buried depth of the first insulation layer. When backfilling, place a moisture content meter and an earth pressure gauge simultaneously; and

[0027] Carry out full-section spraying of the first insulation layer, arrange moisture content meter and soil pressure gauge, and then backfill to the roadbed.

[0028] In a preferred embodiment, the specific steps of laying the first insulation layer in another group of test areas are:

[0029] The test area of ​​this group was excavated with a depth of 30 to 50 cm;

[0030] Lay out a moisture content meter and an earth pressure gauge at the burial depth of the second insulation layer; and

[0031] Carry out full-section spraying of the first insulation layer, arrange moisture content meter and soil pressure gauge, and then backfill to the roadbed.

[0032] In a preferred embodiment, before spraying the first thermal insulation layer and the second thermal insulation layer, a geotextile is laid on the spraying surface.

[0033] In a preferred embodiment, moisture content meters are arranged on both the upper and lower sides of the first thermal insulation layer and the second thermal insulation layer, and earth pressure gauges are arranged on both the first thermal insulation layer and the second thermal insulation layer.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] Through this test method, the changes in temperature and moisture, settlement displacement, soil pressure, etc. in the insulation roadbed and the natural roadbed can be quickly understood. Through regular settlement observation, displacement monitoring and other means, the stability of the roadbed during construction and after completion can be evaluated. The temperature, moisture content and soil pressure data in multiple test areas can be compared to facilitate the rapid determination of different insulation layer burial depths for roadbeds in deep soil-containing heavy ice areas with different geological conditions and ice depths. On the basis of meeting the requirements of the insulation layer's own strength and the thickness of the roadbed structure layer, the insulation layer is buried as close to the top surface of the roadbed as possible to maximize its effectiveness, reduce the heat absorption of the roadbed, and protect the stability of the roadbed. This is convenient for the comprehensive effect of multiple means in the subsequent construction to achieve roadbed insulation and anti-melting settlement, thereby ensuring the durability of the roadbed and guaranteeing its stability and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the specific implementation of the present invention, the following will briefly introduce the drawings required for use in the specific implementation. In all the drawings, each element or part is not necessarily drawn according to the actual scale.

[0037] Figure 1 A schematic diagram of the structure of a monitoring hole, a moisture content meter, and an earth pressure gauge in a construction test method for heat insulation and anti-thaw settlement of a roadbed in a deep soil-containing heavy ice layer area provided by the present invention; DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Technicians in this field can make some non-essential improvements and adjustments to the present invention based on the above application content.

[0039] Example:

[0040] like Figure 1 As shown, the present invention provides a test method for heat insulation and anti-melting settlement construction of roadbed in deep soil-containing heavy ice layer area, comprising the following steps:

[0041] First, the construction section is selected and the buried depth of the first insulation layer is calculated. The geological conditions of the test section are: 0-100m is an ice layer, which is not penetrated, white and free of impurities, and the ice contains suspended fine sand and dust. According to the design plan of the roadbed during construction, the test section over-excavates 150cm below the roadbed structure layer and fills it with block stones. Among them, the bottom 100cm is a gabion roadbed, and the block stones in the gabion are 25-40cm block stones. 50cm above the gabion roadbed is a stone-filled roadbed, and the stone specifications are 10-15cm block stones. The slope is stacked with 20cm block stones.

[0042] The specific steps for calculating the buried depth of the first insulation layer are:

[0043] By calculation Calculate the corresponding reasonable burial depth, where P represents the tire pressure (MPa), d represents the equivalent circular diameter of the single wheel pressure transmission surface (m), r represents the weighted average value of the bulk density of each structural layer above the insulation layer (MN / m3), tan is the tangent function, Φ represents the weighted average value of the stress diffusion angle above the insulation layer and the structural layer (°), h represents the reasonable burial depth of the insulation layer (m), and б represents the allowable compressive stress of the insulation layer (MPa).

[0044] Different thermal insulation and anti-melting materials have different allowable compressive stresses (б). Different fillers on the thermal insulation and anti-melting layer correspond to different weighted average values ​​of stress diffusion angle (Φ) and weighted average values ​​of bulk density of the structural layer (r). Different parameters can be used to calculate the corresponding reasonable burial depth. In some preferred embodiments, taking the burial depth of PU (polyurethane) material as an example, taking the standard axle load BZZ-100, Φ=36°, r=0.023MN / m3, б=0.68MPa (r, Φ values ​​may have deviations) as an example, it is calculated that: h≥0.16m, that is, when the PU layer depth is ≥0.16m, the driving action may have no adverse effect on the insulation layer after completion, that is, as a reasonable burial depth of the insulation layer. In design applications, considering the large vehicle load and the error of the above calculation, a safety factor of 1.4 is added to the above calculation result, and the burial depth of the insulation layer is 23cm below the design elevation of the roadbed. The optimal reasonable burial depth of the insulation layer is about 30 to 50cm.

[0045] like Figure 1 As shown, in this embodiment, the thickness of the insulation layer is determined, and the buried depth of the second insulation layer is determined. The second insulation layer is located below the first insulation layer. The thickness of the insulation layer is the main factor affecting the thermal insulation and anti-melting effect. From the perspective of reducing heat transfer, the thicker the insulation layer, the better. The thermal insulation and anti-melting effect is not proportional to the thickness of the insulation layer. As the thickness of the insulation layer increases, the degree of increase in the thermal insulation and anti-melting effect gradually decreases, and it is economically unreasonable to have too large a thickness of the insulation layer. Through experiments, it is known that when the thickness of the insulation layer made of PU material increases from 1cm to 3cm, the temperature difference on both sides increases rapidly. When it increases from 3cm to 5cm, the increase in temperature difference slows down. When it increases from 5cm to 7cm, the temperature difference remains basically unchanged. This shows that the reasonable thickness of the PU layer is 3 to 5cm.

[0046] Laying a double layer of PU in the frozen soil roadbed will improve the thermal insulation and anti-thaw settlement effect. When the position of the upper PU layer is determined at a depth of 30 to 50 cm, the reasonable laying depth of the lower PU layer also affects the thermal insulation and anti-thaw settlement effect. If the PU layers are too close, the interlayer temperature will rise, resulting in a melting depth below -1m. When the PU layer interval is 1.6m and 2m, the melting depth of the roadbed is basically the same. Comprehensive indoor tests and numerical simulations show that the interval between the two PU layers should be greater than 1m. According to the actual situation on site, the laying depth of the lower PU should be about 1.6 to 1.8m.

[0047] like Figure 1As shown, in this embodiment, the construction section is further divided into three groups of test areas with equal spacing, and the grating optical cables and earth pressure gauges are arranged in the three groups of test areas respectively, two of the test areas are excavated in turn, and the first insulation layer and the second insulation layer are laid at corresponding depths in one group of the test areas, the first insulation layer is laid in the other group of the test areas, and the earth pressure gauges and moisture content meters are arranged in all three groups of the test areas.

[0048] The specific steps to complete the layout of grating cables and earth pressure gauges in the three test areas are as follows:

[0049] First, the depth of the ice surface was determined by drilling, and then three monitoring holes were drilled in the center of each of the three test areas. Two groups of monitoring holes were drilled to a depth of 1m below the ice surface, and multiple groups of grating optical cables were arranged at intervals in the detection holes. The other two groups of monitoring holes were drilled to the ice surface, and moisture meters and soil pressure gauges were arranged respectively. Then, pipes with the same aperture were inserted into the drilled monitoring holes, and finally the monitoring holes were backfilled with fine-grained soil.

[0050] Among them, the moisture meter can detect the moisture content and temperature of the soil, the soil pressure meter is used to detect the soil pressure, and the grating cable uses the fiber grating technology to convert the optical signal in the optical fiber into an electrical signal, thereby realizing the detection and processing of the optical signal. When the external physical quantity acts on the optical fiber of the grating cable, due to the presence of the grating in the optical fiber, the light field will interfere, thereby introducing a grating signal in the optical fiber. As the physical quantity changes, the grating signal introduced into the grating is also constantly changing. By detecting and processing this grating signal, the value and change of the physical quantity can be obtained, thereby detecting the soil displacement. In addition, it can be understood that in some preferred embodiments, four groups of grating cables are selected and arranged in each test area, and the arrangement depths are 0-0.4m, 0.4-1.7m, 1.7-3.8m and 3.8-5m respectively.

[0051] In a specific implementation, the three test areas are divided into test area No. 1, test area No. 2 and test area No. 3, each test area is 5m long and the roadbed design width is 7.5m. Test area No. 1 is a two-layer insulation roadbed test section, and the PU layer is sprayed at a depth of 30 to 50cm and 160 to 180cm below the design elevation of the roadbed top surface, respectively. Test area No. 2 is a single-layer insulation roadbed test section, and the PU layer is sprayed at a depth of 30 to 50cm below the design elevation of the roadbed top surface. Test area No. 3 is a normal roadbed control section, and the PU layer is not sprayed.

[0052] like Figure 1 As shown, in this embodiment, the specific steps of laying the first insulation layer and the second insulation layer at corresponding depths in one group of test areas are:

[0053] First, excavate the No. 1 test area with an excavation depth of 160 to 180 cm, then spray the entire section of the second insulation layer, and backfill to the burial depth of the first insulation layer. When backfilling, moisture meters and soil pressure gauges are arranged simultaneously. Finally, spray the entire section of the first insulation layer, arrange moisture meters and soil pressure gauges, and then backfill to the roadbed.

[0054] The specific steps for laying the first insulation layer in another group of test areas are:

[0055] Excavation was carried out in the No. 2 test area with a depth of 30 to 50 cm. Then, a moisture meter and an earth pressure gauge were arranged at the burial depth of the second insulation layer. Finally, the entire section of the first insulation layer was sprayed, and the moisture meter and earth pressure gauge were arranged before backfilling to the roadbed.

[0056] During the construction process, it is necessary to ensure that the No. 1 test area is excavated first, so that the placement depth of the moisture content meter and the earth pressure gauge can be determined, and the remaining test areas are placed at the same depth.

[0057] like Figure 1 As shown, in this embodiment, before spraying the first insulation layer and the second insulation layer, a geotextile is laid on the spraying surface to increase the integrity of the PU layer. The PU layer is sprayed with a thickness of 3 to 5 cm. A thin layer is sprayed first to form an insulation layer to prevent subsequent heat transfer, and then subsequent spraying is performed. Moisture content meters are arranged on both the upper and lower sides of the first insulation layer and the second insulation layer, and soil pressure gauges are arranged on the first insulation layer and the second insulation layer.

[0058] Finally, data are acquired from the moisture content meter, earth pressure gauge, and grating cable and compared with the design standards.

[0059] Specific usage and beneficial effects of the present invention:

[0060] Through this test method, the changes in temperature and moisture, settlement displacement, soil pressure, etc. in the insulation roadbed and the natural roadbed can be quickly understood. Through regular settlement observation, displacement monitoring and other means, the stability of the roadbed during construction and after completion can be evaluated. The temperature, moisture content and soil pressure data in multiple test areas can be compared to facilitate the rapid determination of different insulation layer burial depths for roadbeds in deep soil-containing heavy ice areas with different geological conditions and ice depths. On the basis of meeting the requirements of the insulation layer's own strength and the thickness of the roadbed structure layer, the insulation layer is buried as close to the top surface of the roadbed as possible to maximize its effectiveness, reduce the heat absorption of the roadbed, and protect the stability of the roadbed. This is convenient for the comprehensive effect of multiple means in the subsequent construction to achieve roadbed insulation and anti-melting settlement, thereby ensuring the durability of the roadbed and guaranteeing its stability and safety.

[0061] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments. On the basis of the present invention, some modifications or improvements can be made thereto, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A test method for heat insulation and anti-melting settlement construction of roadbed in thick soil-containing heavy ice layer areas, characterized in that: The following steps are included: Select the construction section and calculate the burial depth of the first insulation layer; Determine the thickness of the insulation layer and determine the embedding depth of the second insulation layer, the second insulation layer is located below the first insulation layer; The construction section was divided into three groups of test areas with equal spacing, and the grating cables and earth pressure gauges were arranged in the three groups of test areas respectively; Excavate two of the test areas in sequence, and lay the first insulation layer and the second insulation layer at the corresponding depth in one of the test areas, lay the first insulation layer in the other test area, and arrange earth pressure gauges and moisture content meters in the three test areas; and Obtain data and compare it to design standards.

2. The test method for heat insulation and anti-melting settlement construction of roadbed in thick soil-containing heavy ice layer area according to claim 1 is characterized by: The thermal insulation layer is a polyurethane thermal insulation layer.

3. The test method for heat insulation and anti-melting settlement construction of roadbed in thick soil-containing heavy ice layer area according to claim 1 is characterized in that: The specific steps of calculating the embedding depth of the first thermal insulation layer are: By calculation Calculate the corresponding reasonable burial depth; Where P is the tire pressure (MPa), d is the equivalent circular diameter of the pressure transmission surface of a single wheel (m), r is the weighted average value of the bulk density of each structural layer above the insulation layer (MN / m3), tan is the tangent function, Φ is the weighted average value of the stress diffusion angle above the insulation layer and the structural layer (°), h is the reasonable burial depth of the insulation layer (m), and б is the allowable compressive stress of the insulation layer (MPa).

4. The test method for heat insulation and anti-melting settlement construction of roadbed in thick soil-containing heavy ice layer area according to claim 1 is characterized by: The thickness of the thermal insulation layer is 3 to 5 cm.

5. The test method for heat insulation and anti-melting settlement construction of roadbed in thick soil-containing heavy ice layer area according to claim 1 is characterized in that: Determining the embedding depth of the second thermal insulation layer also includes: The second thermal insulation layer is spaced greater than 1 m from the first thermal insulation layer.

6. The test method for heat insulation and anti-melting settlement construction of roadbed in thick soil-containing heavy ice layer area according to claim 1 is characterized in that: The specific steps of completing the arrangement of the grating optical cable and the earth pressure gauge in the three test areas are as follows: Determine the depth of the ice surface by drilling; Three monitoring holes were drilled at the center of each of the three test areas. Two groups of monitoring holes were drilled to a depth of 1m below the ice surface and multiple groups of grating optical cables were arranged at intervals in the detection holes. The other two groups of monitoring holes were drilled to the ice surface and water content meters and earth pressure gauges were arranged respectively. Insert pipes of the same diameter into the drilled monitoring holes; and The monitoring holes are backfilled with fine-grained soil.

7. The test method for heat insulation and anti-melting settlement construction of roadbed in thick soil-containing heavy ice layer area according to claim 1 is characterized in that: The specific steps of laying the first insulation layer and the second insulation layer at corresponding depths in one group of test areas are: The test area of ​​this group was excavated to a depth of 160 to 180 cm; Spray the entire section of the second insulation layer and backfill to the buried depth of the first insulation layer. When backfilling, place a moisture content meter and soil pressure gauge simultaneously. and Carry out full-section spraying of the first insulation layer, arrange moisture content meter and soil pressure gauge, and then backfill to the roadbed.

8. The test method for heat insulation and anti-melting settlement construction of roadbed in thick soil-containing heavy ice layer area according to claim 7 is characterized in that: The specific steps of laying the first insulation layer in another group of test areas are: The test area of ​​this group was excavated with a depth of 30 to 50 cm; Lay out a moisture content meter and an earth pressure gauge at the burial depth of the second insulation layer; and Carry out full-section spraying of the first insulation layer, arrange moisture content meter and soil pressure gauge, and then backfill to the roadbed.

9. The test method for heat insulation and anti-melting settlement construction of roadbed in thick soil-containing heavy ice layer area according to claim 8 is characterized by: Before spraying the first insulation layer and the second insulation layer, lay geotextile on the spraying surface.

10. The test method for heat insulation and anti-melting settlement construction of roadbed in thick soil-containing heavy ice layer area according to claim 8 The method is characterized by: Moisture content meters are arranged on both the upper and lower sides of the first insulation layer and the second insulation layer. Earth pressure gauges are arranged on both the first insulation layer and the second insulation layer.

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