A method for treating expansion cracks in asphalt pavement

Abstract

The present invention relates to a method for treating arch expansion cracks in an asphalt pavement. The asphalt pavement comprises an asphalt pavement structure and pre-cut cracks. The asphalt pavement structure comprises a structural layer and a base layer. The structural layer is divided into an upper layer and a lower layer. The upper layer is modified asphalt concrete, and the lower layer is asphalt concrete. The structural layer is arranged above the base layer. The pre-cut cracks are arranged in the base layer. The temperature drop allowable value and the temperature rise condition for the base layer to not crack are calculated by the influence of temperature and humidity parameters, and cracking of the asphalt pavement is prevented according to the temperature limit. The purpose of the present invention is to solve the technical problem in the prior art that pavement cracking occurs due to temperature difference.

Description

Technical Field

[0001] The invention relates to the field of pavement structure treatment, and in particular to a method for treating arch expansion cracks in asphalt pavement. Background Art

[0002] The desert regions of the Xinjiang Uyghur Autonomous Region experience a dry climate, exceptionally high daytime temperatures in summer, large temperature swings between day and night, and frigid winters, with extreme lows reaching -30.9°C. These unique climatic conditions lead to rapid evaporation of moisture from the base layer. Furthermore, the alternating effects of high and low temperatures have resulted in significantly more severe asphalt concrete pavement problems in the desert regions of the Xinjiang Uyghur Autonomous Region than in other regions. These problems primarily manifest as transverse cracks, which are present throughout the road at intervals of 10 to 20 meters. These cracks directly alter the stress conditions in the pavement structure, reducing its service life and negatively impacting vehicle comfort and safety. Based on previous experience, review and analysis of relevant data, and investigations, it has been determined that the majority of cracks in asphalt pavements are caused by cracks in the base layer; cracking in the asphalt surface layer is rare. In addition to uneven settlement caused by insufficient bearing capacity of the underlying stratum, base layer cracks are primarily due to the inherent compatibility of the base material with environmental conditions, as well as quality defects during construction.

[0003] Therefore, developing a method for treating arch expansion cracks that can address the technical problem of road cracking caused by temperature difference in the existing technology is an urgent problem to be solved. Summary of the Invention

[0004] In view of the fact that most of the arching cracks in desert areas in the existing technology are caused by the emission of cracks in the base layer, in order to solve this technical problem, the present invention provides a method for treating arching cracks in asphalt pavements. The asphalt pavement includes an asphalt pavement structure and a pre-cut joint, and is implemented by the following technical solution: the asphalt pavement structure includes a structural layer and a base layer, the structural layer is divided into an upper layer and a lower layer, the upper layer is modified asphalt concrete, and the lower layer is asphalt concrete, and the structural layer is arranged above the base layer; the pre-cut joint is arranged in the base layer, and the pre-cut joint is arranged in a manner that a 2 cm wide pre-cut joint is set every 100 m of the base layer, the pre-cut joint must pass through the base layer both horizontally and vertically, and the depth of the pre-cut joint is the overall thickness of the base layer, hot asphalt is poured into the pre-cut joint, and a fiberglass grid is provided at the position corresponding to the pre-cut joint at the contact surface between the pavement structure layer and the base layer.

[0005] Furthermore, the construction method of the pre-cut seam includes:

[0006] Step 1: After the base layer is constructed, first use a seam cutter to cut the seams on the base layer. After the seams are cut, clean the gaps and blow away the dust with compressed air.

[0007] Step 2: After cleaning, pour hot asphalt into the gap. To prevent the melting and loss of the asphalt filling during the hot asphalt paving, add 5-10mm crushed stone during the pouring process.

[0008] Step 3: Before the construction of the pavement structure layer, add glass fiber grids at the cut joints. The grid width is 2m, 1m on each side.

[0009] Furthermore, the asphalt pavement structure construction includes the following steps:

[0010] (1) Construction preparation:

[0011] Design the base mix ratio and select a cement-stabilized base mix ratio with low temperature and moisture sensitivity; select mixing equipment appropriately. The shrinkage of the base mix is ​​related to the moisture content, gradation, and cement dosage of the mix, with the moisture content and cement dosage having a relatively greater impact; select a reasonable construction temperature;

[0012] (2) Pavement structure paving: The paving equipment should match the gradation of the base layer to control the segregation of materials during the paving process. When the paver spreads materials to both sides, the longer the spreading distance, the more serious the material segregation. To control the segregation of materials, the paving width is required to be controlled within 6.0m. After the base layer is paved, pre-cut joints are constructed. The control basis of pre-cut joints is: Design the expansion cracks according to the spacing of the predictable shrinkage cracks: Under the action of temperature load, the spacing of the predictable shrinkage cracks is:

[0013] σ=ρghLf

[0014] L=σ / ρghf

[0015] Where: σ is the tensile strength of the base material, MPa, ρ is the specific gravity of the base, h is the thickness of the base, and f is the friction coefficient between the base and the subbase;

[0016] (3) Pavement structure layer maintenance: Moisturizing and curing the cement stabilized base layer is the key to controlling the shrinkage of the base layer. The base layer must be maintained by moisturizing maintenance, and after the 7-day curing period, base layer moisturizing measures must still be taken to prevent excessive evaporation of water.

[0017] Furthermore, in the step (1) of selecting a reasonable construction temperature, the method for preventing thermal shrinkage cracks is to first calculate the temperature that causes thermal shrinkage cracking of the base layer, and then select a local temperature range to organize the construction of the base layer. The calculation method of the allowable temperature is:

[0018] The stress generated by the material shrinkage is [σ], the tensile strength of the material is σ, the thermal shrinkage coefficient of the material is α, the elastic modulus is E, the compressive strength is R, and the base layer does not crack. The following conditions should be met:

[0019]

[0020] That is, when the strain of the base layer is greater than ε, shrinkage cracks will occur, and the allowable temperature drop ΔT can be calculated as:

[0021] ΔT=ε / α.

[0022] Furthermore, in the selection of a reasonable construction temperature in step (1), the influence of temperature on arch expansion and cracking is considered, and the calculation method for judging whether the temperature stress can cause the cement stabilized base to form compressive failure under the constraint conditions is:

[0023] ① First calculate the temperature stress of the uniformly heated base during expansion:

[0024] The temperature stress when the temperature changes by 25℃ is:

[0025] The temperature stress when the temperature changes by 50℃ is:

[0026] Determine the design compressive strength σ of cement stabilized base S and the magnitude of the temperature stress at 25°C and 50°C mentioned above;

[0027] ② Although under the action of unidirectional expansion stress, there will be no crushing along a certain section due to insufficient compressive strength, but because the shear strength of concrete is much smaller than its compressive strength, it may be damaged due to shear along a certain inclined surface. Through stress state analysis, it can be seen that along the inclined surface in the direction of angle θ, the shear stress and normal stress are:

[0028]

[0029] σ θ =σcos 2 θ

[0030] On the inclined surface at an angle of 45°, the shear stress is the largest, and the maximum shear stress is: τ max =σ / 2;

[0031] The maximum shear stresses when the temperature rise is 25℃ and 50℃ are τ 25 , τ 50 ;

[0032] The temperature rise that cement stabilized base materials can withstand is:

[0033]

[0034] ③ The temperature stress of the base layer is verified according to the instability theory of the compression rod. The slenderness ratio of the compression rod is λ = μl / h, the length coefficient μ, and the bearing capacity reduction factor The critical stress for the stability of the compression rod can be calculated as

[0035]

[0036] The temperature rise condition for the base layer to not crack and fail can be calculated as follows:

[0037] σ=EαΔT / (1-μ)≤σ er

[0038] ΔT≤σ er (1-μ) / (Eα).

[0039] After adopting the above technical solution, the beneficial effects of the present invention are:

[0040] 1. Pre-cut seam treatment technology is adopted to reserve space for free expansion of the base layer, release the temperature stress of the base layer, and reduce the cracking of the base layer. According to existing construction experience, the use of pre-cut seam treatment technology can control the arching phenomenon of the base layer under high temperature conditions.

[0041] 2. By calculating the allowable temperature, the occurrence of various thermal shrinkage cracks, dry shrinkage cracks, and arch expansion cracks in the base layer during construction is reduced. By estimating the spacing between cracks, the position of the pre-cut joints is reasonably arranged, reducing the impact of the pre-cut joints on the bearing capacity of the road structure base layer.

[0042] 3. The impact of construction equipment and construction control on base cracks was analyzed, and equipment selection requirements were proposed. Pre-cutting was used to eliminate thermal expansion stress in the base layer, effectively preventing the formation of thermal expansion cracks in the base layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0044] Figure 1 A longitudinal section layout diagram of expansion joints in a cement-stabilized gravel base layer for a method of treating arch expansion cracks in an asphalt pavement provided in an embodiment of the present application.

[0045] Figure 2 A plan view of expansion joints in a cement-stabilized gravel base layer for a method of treating arch expansion cracks in an asphalt pavement provided in an embodiment of the present application.

[0046] Figure 3 This is a stress state analysis diagram of a cement-stabilized base layer when it expands due to heat, according to a method for treating expansion cracks in an asphalt pavement provided in an embodiment of the present application.

[0047] Figure 4 A simplified diagram for calculating thermal shrinkage cracks in the base layer of a method for treating expansion cracks in an asphalt pavement provided in an embodiment of the present application.

[0048] Figure 5 A schematic diagram of thermal expansion and arching damage of the base layer at the inclined joint of a method for treating arching cracks in an asphalt pavement provided in an embodiment of the present application.

[0049] Description of reference numerals:

[0050] 101 - upper layer, 102 - lower layer, 103 - pre-cut slits, 104 - hot asphalt, 105 - fiberglass grating. DETAILED DESCRIPTION

[0051] The following description of the embodiments will help the public better understand the present invention, but the specific embodiments given by the applicant cannot and should not be regarded as limitations on the technical solutions of the present invention. Any changes to the definitions of components or technical features, or formal rather than substantive changes to the overall structure should be regarded as the scope of protection defined by the technical solutions of the present invention.

[0052] In this application, unless otherwise expressly specified or limited, terms such as "mounted," "connected," and "fixed" should be interpreted broadly. For example, these terms may refer to fixed, removable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; internal communication between two components; surface contact only; or surface contact through an intermediary. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0053] The present invention is implemented by the following technical solutions:

[0054] like Figure 1 and Figure 2 A method for treating arch cracks in an asphalt pavement is implemented using the following technical solution: it includes an asphalt pavement structure and a pre-cut slit 103; the asphalt pavement structure includes a structural layer and a base layer, the structural layer is divided into an upper layer 101 and a lower layer 102, the upper layer 101 is modified asphalt concrete, the lower layer 102 is asphalt concrete, and the structural layer is arranged above the base layer; the pre-cut slit 103 is arranged in the base layer, and the pre-cut slit 103 is arranged in a manner that a 2 cm wide pre-cut slit 103 is provided every 100 m of the base layer, the pre-cut slit 103 needs to penetrate the base layer both horizontally and vertically, the depth of the pre-cut slit 103 is the overall thickness of the base layer, hot asphalt 104 is poured into the pre-cut slit 103, and a fiberglass grid 105 is provided at a position corresponding to the pre-cut slit 103 at the contact surface between the pavement structural layer and the base layer.

[0055] The construction method of the pre-cut seam 103 includes:

[0056] Step 1: First, use a seam cutter to cut the seams. After cutting, clean the seams and blow away the dust with compressed air.

[0057] Step 2: After cleaning, pour hot asphalt 104 into the gap. To prevent the melting and loss of the filling asphalt during the paving of the hot asphalt 104, add an appropriate amount of 5-10mm crushed stone during the pouring process.

[0058] Step 3: Before the construction of the pavement structure layer, add glass fiber grid 105 at the cut joint. The grid width is 2m, 1m on each side.

[0059] Furthermore, the asphalt pavement structure construction includes the following steps:

[0060] (1) Construction preparation:

[0061] Design the base mix ratio and select a cement-stabilized base mix ratio with low temperature and moisture sensitivity; select mixing equipment appropriately. The shrinkage of the base mix is ​​related to the moisture content, gradation, and cement dosage of the mix, with the moisture content and cement dosage having a relatively greater impact; select a reasonable construction temperature;

[0062] (2) Pavement structure paving: The paving equipment should match the gradation of the base layer to control the segregation of materials during the paving process. When the paver spreads materials to both sides, the longer the spreading distance, the more serious the material segregation. To control the segregation of materials, the paving width is required to be controlled within 6.0m. After the base layer is paved, pre-cut joints are constructed. The control basis of pre-cut joints is: Design the expansion cracks according to the spacing of the predictable shrinkage cracks: Under the action of temperature load, the spacing of the predictable shrinkage cracks is:

[0063] σ=ρghLf

[0064] L=σ / ρghf

[0065] Where: σ is the tensile strength of the base material, MPa, ρ is the specific gravity of the base, h is the thickness of the base, and f is the friction coefficient between the base and the subbase.

[0066] In step (3), the method for preventing thermal shrinkage cracks in selecting a reasonable construction temperature is to first calculate the temperature that causes thermal shrinkage cracking of the base layer, and then select a local temperature range to organize the construction of the base layer. The calculation method of the allowable temperature is:

[0067] The stress generated by the material shrinkage is [σ], the tensile strength of the material is σ, the thermal shrinkage coefficient of the material is ɑ, the elastic modulus is E, the compressive strength is R, and the base layer does not crack. The following conditions should be met:

[0068]

[0069] That is, when the strain of the base layer is greater than ε, shrinkage cracks will occur, and the allowable temperature drop ΔT can be calculated as:

[0070] ΔT=ε / α.

[0071] In step (3), when selecting a reasonable construction temperature, the influence of temperature on arch expansion and cracking is considered, and the calculation method for judging whether the temperature stress can cause the cement stabilized base to form compressive failure under the constraint conditions is:

[0072] ① First calculate the temperature stress of the uniformly heated base during expansion:

[0073] The temperature stress when the temperature changes by 25℃ is:

[0074] The temperature stress when the temperature changes by 50℃ is:

[0075] Determine the design compressive strength σ of cement stabilized base S and the magnitude of the temperature stress at 25°C and 50°C mentioned above;

[0076] ② If Figure 3 、 Figure 4 and Figure 5 As shown in the figure, although under the action of unidirectional expansion stress, there will be no crushing along a certain section due to insufficient compressive strength, but because the shear strength of concrete is much smaller than its compressive strength, it may be damaged due to shear along a certain inclined surface. Through stress state analysis, it can be seen that along the inclined surface in the direction of angle θ, the shear stress and normal stress are:

[0077]

[0078] σ θ =σcos 2 θ

[0079] On the inclined surface at an angle of 45°, the shear stress is the largest, and the maximum shear stress is: τ max =σ / 2;

[0080] The maximum shear stresses when the temperature rise is 25℃ and 50℃ are τ 25 , τ 50 ;

[0081] The temperature rise that cement stabilized base materials can withstand is:

[0082]

[0083] ③ The temperature stress of the base layer is verified according to the instability theory of the compression rod. The slenderness ratio of the compression rod is λ = μl / h, the length coefficient μ, and the bearing capacity reduction factor The critical stress for the stability of the compression rod can be calculated as

[0084]

[0085] The temperature rise condition for the base layer to not crack and fail can be calculated as follows:

[0086] σ=EαΔT / (1-μ)≤σ er

[0087] ΔT≤σ er (1-μ) / (Eα).

[0088] Those skilled in the art should understand that they can implement variations by combining the prior art with the above embodiments, which will not be described in detail here. Such variations do not affect the essence of the present invention and will not be described in detail here.

[0089] The above describes the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and the devices and structures that are not described in detail should be understood to be implemented in a common manner in the art; any technician familiar with the art can use the above-mentioned disclosed methods and technical contents to make many possible changes and modifications to the technical solutions of the present invention without departing from the scope of the technical solutions of the present invention, or modify them into equivalent embodiments of equivalent changes, which does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention that do not depart from the content of the technical solutions of the present invention are still within the scope of protection of the technical solutions of the present invention.

Claims

1. A method for treating arch cracks in an asphalt pavement, wherein the asphalt pavement comprises an asphalt pavement structure and pre-cut cracks, characterized in that: The asphalt pavement structure includes a structural layer and a base layer, the structural layer is divided into an upper layer and a lower layer, the upper layer is modified asphalt concrete, the lower layer is asphalt concrete, and the structural layer is arranged above the base layer; The pre-cut slits are provided in the base layer. The pre-cut slits are arranged in such a manner that a 2 cm wide pre-cut slit is provided every 100 m of the base layer. The pre-cut slits need to penetrate the base layer in both the horizontal and vertical directions. The depth of the pre-cut slits is equal to the overall thickness of the base layer. Hot asphalt is poured into the pre-cut slits. A fiberglass grid is provided at the position corresponding to the pre-cut slits at the contact surface between the pavement structure layer and the base layer. The construction method of the pre-cut slits includes: Step 1: After constructing the base layer, first use a seam cutter to cut the seams on the base layer. After the seams are cut, clean the gaps and blow away the dust with compressed air. Step 2: After cleaning, pour hot asphalt into the gap. To prevent the melting and loss of the asphalt filling during the hot asphalt paving, add 5-10mm crushed stone during the pouring process. Step 3: Before the construction of the pavement structure layer, add glass fiber grids at the cut joints. The grid width is 2m, 1m on each side; The following asphalt pavement structure construction methods are included: (1) Construction preparation: Design the base mix ratio and select a cement-stabilized base mix ratio with low temperature and moisture sensitivity; select mixing equipment appropriately. The shrinkage of the base mix is ​​related to the moisture content, gradation, and cement dosage of the mix, with the moisture content and cement dosage having a relatively greater impact; select a reasonable construction temperature; (2) Pavement structure paving: The paving equipment should match the gradation of the base layer to control the segregation of materials during the paving process. When the paver spreads materials to both sides, the longer the spreading distance, the more serious the material segregation. To control the segregation of materials, the paving width is required to be controlled within 6.0m. After the base layer is paved, pre-cut joints are constructed. The control basis of pre-cut joints is: Design the expansion cracks according to the spacing of the predictable shrinkage cracks: Under the action of temperature load, the spacing of the predictable shrinkage cracks is: σ=ρghLf L=σ / ρghf Where: σ is the tensile strength of the base material, MPa, ρ is the specific gravity of the base, h is the thickness of the base, and f is the friction coefficient between the base and the subbase; (3) Pavement structure layer maintenance: Moisturizing and curing the cement stabilized base layer is the key to controlling the shrinkage of the base layer. The base layer must be maintained by moisturizing maintenance, and after the 7-day curing period, base layer moisturizing measures must still be taken to prevent excessive evaporation of water.

2. The method for treating asphalt pavement expansion cracks according to claim 1, characterized in that: In step (1), the method for preventing thermal shrinkage cracks in selecting a reasonable construction temperature is to first calculate the temperature that causes thermal shrinkage cracking of the base layer, and then select a local temperature range to organize the construction of the base layer. The calculation method of the allowable temperature is: The stress generated by the material shrinkage is [σ], the tensile strength of the material is σ, the thermal shrinkage coefficient of the material is α, the elastic modulus is E, the compressive strength is R, and the base layer does not crack. The following conditions should be met: That is, when the strain of the base layer is greater than ε, shrinkage cracks will occur, and the allowable temperature drop ΔT can be calculated as: ΔT=ε / α.

3. The method for treating asphalt pavement expansion cracks according to claim 2, characterized in that: In the selection of a reasonable construction temperature in step (1), the influence of temperature on arch expansion and cracking is considered, and the calculation method for judging whether the temperature stress can cause the cement stabilized base to form compressive failure under the constraint conditions is: ① First calculate the temperature stress of the uniformly heated base during expansion: The temperature stress when the temperature changes by 25℃ is: The temperature stress when the temperature changes by 50℃ is: Determine the design compressive strength σ of cement stabilized base S and the magnitude of the temperature stress at 25°C and 50°C mentioned above; ② Although under the action of unidirectional expansion stress, there will be no crushing along a certain section due to insufficient compressive strength, but because the shear strength of concrete is much smaller than its compressive strength, it may be damaged due to shear along a certain inclined surface. Through stress state analysis, it can be seen that along the inclined surface in the direction of angle θ, the shear stress and normal stress are: s θ =σcos 2 i On the inclined surface at an angle of 45°, the shear stress is the largest, and the maximum shear stress is: τ max =σ / 2; The maximum shear stresses when the temperature rise is 25℃ and 50℃ are τ 25 , τ 50 ; The temperature rise that cement stabilized base materials can withstand is: ③ The temperature stress of the base layer is verified according to the instability theory of the compression rod. The slenderness ratio of the compression rod is λ = μl / h, the length coefficient μ, and the bearing capacity reduction factor The critical stress for the stability of the compression rod can be calculated as The temperature rise condition for the base layer to not crack and fail can be calculated as follows: σ=EαΔT / (1-μ)≤σ er ΔT≤σ er (1-μ) / (Eα).

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