Continuously reinforced concrete pavement and its design and construction methods

Abstract

The present invention relates to the technical field of pavement structure, and specifically to a design and construction method of a continuous reinforced concrete pavement and a pavement, comprising a continuous reinforced base layer and an asphalt surface layer, wherein the asphalt surface layer comprises an asphalt functional layer and an asphalt anti-skid layer arranged from bottom to top; the continuous reinforced base layer comprises a concrete layer and a continuous steel mesh arranged in the concrete layer. Compared with the prior art, the design and construction method of the present invention improves the interlayer shear strength, reduces shear damage, maintains the overall performance of the structure, fills the gap in the current specification on the design of continuously reinforced concrete pavements, can improve the durability of the structure, and extend the service life of the pavement.

Description

Technical Field

[0001] The invention relates to the technical field of pavement structure, and in particular to a continuous reinforced concrete pavement and a design and construction method. Background Art

[0002] In the structure of continuously reinforced concrete asphalt pavement, the asphalt surface layer mainly plays the role of preventing or reducing rainwater infiltration, anti-fouling, anti-skid, etc. The continuously reinforced concrete base is the main load-bearing layer, and longitudinal continuous steel bars and transverse steel bars are configured. Due to the elimination of transverse shrinkage joints, various joint diseases during the operation period are greatly reduced. At the same time, the integrity and flatness are good, and the driving comfort is good. It is one of the main development directions of heavy-duty traffic long-life cement pavement. The reason why continuously reinforced concrete pavement can be set without transverse shrinkage joints is that a sufficient number of longitudinal steel bars are configured in the structure. Usually, the longitudinal reinforcement ratio is as high as 0.6% to 1.0%. The shrinkage cracking of concrete is limited by the bonding effect between the longitudinal steel bars and concrete, and the transverse shrinkage cracks are dispersed into many micro cracks with a certain spacing, thereby achieving the purpose of not cutting shrinkage joints. However, there are certain deficiencies in the current standard design method, resulting in low pavement strength, which is not enough to maintain long-term normal service under the background of increasing traffic volume. Summary of the invention

[0003] In order to solve the problems mentioned in the background technology, the purpose of the present invention is to provide a continuous reinforced concrete pavement and a design and construction method.

[0004] On the one hand, the present invention provides a design and construction method of a continuously reinforced concrete pavement, which mainly comprises the following steps:

[0005] S1. Determine the longitudinal reinforcement ratio of the continuously reinforced base;

[0006] S2. Determine the minimum oil ratio of the asphalt functional layer;

[0007] S3. Determine the thickness of the asphalt surface layer;

[0008] S4. Continuous steel mesh is arranged on the base layer, and 2-4 ground anchor beams are set at the connecting ends of the base layer and other structures. Concrete is poured on the continuous steel mesh beams and on the ground anchor beams to form a ground beam, thereby forming a continuous reinforced base layer; an asphalt functional layer and an asphalt anti-skid layer are laid in sequence on the continuous reinforced base layer.

[0009] Preferably, S1 specifically comprises: (1) preliminarily formulating the reinforcement ratio, calculating the transverse crack spacing L according to Formula 3, and when L < 1.0 m or L > 2.5 m, re-formulating the reinforcement ratio ρ until 1.0 m ≤ L ≤ 2.5 m;

[0010]

[0011] Where: ρ-reinforcement ratio; b-stress coefficient; Ks-bond stiffness coefficient; ds-steel diameter; Es-steel elastic modulus; Ec-concrete elastic modulus

[0012] (2) According to the reinforcement ratio determined in step (1), the crack width L is calculated according to formula 4: b , when L b >1mm, re-determine the reinforcement ratio until L b ≤1mm;

[0013] L b =(a c ΔT+ε h ) b L type 4

[0014] λ b -crack width coefficient; a c -concrete linear expansion coefficient; ΔT-temperature difference; ε h - Drying shrinkage strain of continuously reinforced concrete

[0015] (3) Based on the reinforcement ratio determined in step (2) and the steel stress δ calculated according to formula (5), when δ>335 MPa, the reinforcement ratio is re-determined until δ≤335 MPa;

[0016] δ=Es(a c ΔTλ a +a s ΔT) Formula 5

[0017] Es-elastic modulus of steel bar; a c -concrete linear expansion coefficient; ΔT-temperature difference; λ a -crack width coefficient; a s -Reinforcement linear expansion coefficient. The reinforcement ratio calculation formula determined by the present invention is used to guide the design, which can effectively solve the problems of unreasonable cracks often occurring in continuous reinforced concrete pavements and complex settings of reinforced concrete pavement force transmission rods and many cuts, and has great engineering practical value; the present invention has simple steps, clear formulas, fully considers various internal and external factors, and has high calculation accuracy.

[0018] Preferably, the stress coefficient b is calculated by the steel bar stiffness contribution rate Φ and the concrete thermal shrinkage stress coefficient λ. c Sure;

[0019]

[0020] ρ-reinforcement ratio; Es-elastic modulus of steel bars; Ec-elastic modulus of concrete; ft-standard value of concrete tensile strength; a c -concrete linear expansion coefficient; ΔT-temperature difference; ε h- Drying shrinkage strain of continuously reinforced concrete.

[0021] Preferably, the crack width coefficient λ a Determined by the steel bar stiffness contribution rate Φ and the stress coefficient b.

[0022] Preferably, S3 specifically comprises: (1) preliminarily determining the reasonable thickness of the asphalt surface layer, and using BISAR software to calculate the interlayer shear stress f between the asphalt surface layer and the continuous reinforcement base layer; (2) calculating the interlayer allowable shear stress [f] between the asphalt surface layer and the continuous reinforcement base layer according to Formula 6;

[0023]

[0024] k v - shear velocity correction factor; σ- vertical load; φ- internal friction angle of bonding material; C- bonding material cohesion; k- interlayer shear strength coefficient

[0025] (3) Verify the shear stress, f≤[f]. Since the modulus of the asphalt surface layer and the continuous reinforced base layer differ greatly, the deformation coordination is poor when the expansion is mentioned, so the asphalt surface layer and the continuous reinforced base layer are prone to slippage. When the horizontal thrust of the asphalt surface layer is large, it is easy to cause slippage, hugging and other phenomena. However, the shear stress can be reduced by reducing the interlayer bonding state, but at the same time, the shear strength will decrease faster, which will reduce the service life of the road surface. Therefore, this application introduces the interlayer allowable shear stress parameter to determine the reasonable asphalt surface layer thickness within the designed service life, so as to improve the interlayer shear strength, reduce shear damage, maintain the overall performance of the structure, and provide good performance for the road surface.

[0026] Preferably, the interlayer shear structure strength coefficient k=1.5 / A, where A is the road grade coefficient. In actual design, the coefficients of expressway, first-class highway and second-class highway are 1.0, 1.1 and 1.2 respectively.

[0027] Preferably, S2 is specifically: (1) obtaining the best oil ratio of asphalt according to the Marshall test, and preparing asphalt mixture specimens with different oil ratios based on the best oil ratio ±1%; (2) calculating the anti-reflective crack factor J of each asphalt mixture specimen according to Formula 7;

[0028] J=ηU T B(da) Formula 7

[0029] U T - total strain energy at failure; B- beam width; d- beam height; a- notch depth

[0030] (3) Calculate the change rate of each asphalt mixture specimen and the specimen with the best oil ratio, so as to determine the minimum oil ratio of the asphalt functional layer. By setting up the asphalt functional layer, the strong restriction of the interface between the asphalt surface layer and the continuous reinforced base layer is transformed into a weak restriction, which significantly improves the flexural strength of the concrete and reduces the fracture damage of the road surface. In addition, the anti-reflective cracking factor J is introduced to determine the optimal oil ratio, so that the asphalt functional layer has excellent anti-scouring and anti-reflective cracking performance, avoids water erosion of the base layer, and improves the service life of the road surface.

[0031] Preferably, the ground beam in S4 is specifically as follows: a fixed steel cage is installed in the foundation, steel support brackets are tied on both sides and the upper end of the steel cage, the steel cage is first cast in layers, and the height of the concrete in the foundation is roughly flush with the top surface of the base layer to form a whole.

[0032] On the other hand, the present invention provides a continuous reinforced concrete pavement, which is constructed by the above method.

[0033] Preferably, it comprises a continuous reinforced base layer and an asphalt surface layer, wherein the asphalt surface layer comprises an asphalt functional layer and an asphalt anti-skid layer arranged from bottom to top; the continuous reinforced base layer comprises a concrete layer and a continuous steel mesh arranged in the concrete layer.

[0034] Beneficial effects: Compared with the prior art, the design and construction method of the present invention improves the interlayer shear strength, reduces shear damage, maintains the overall performance of the structure by introducing interlayer allowable shear stress parameters, setting asphalt functional layers and optimizing reinforcement ratio calculations, thereby filling the gap in the current specifications for the design of continuously reinforced concrete pavements, improving structural durability and extending the service life of the pavement. DETAILED DESCRIPTION

[0035] The present invention is described in detail below through specific embodiments. It is pointed out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above invention content. In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper surface", "lower surface", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "forward", "reverse", "axial", "radial", "circumferential" and the like indicate the orientation or position relationship based on the orientation or position relationship shown, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. Unless otherwise specified, the parts described in the present invention are all weight parts, the percentages are all mass percentages, and the concentrations are mass percentage concentrations.

[0036] Example 1 Reinforcement design of continuous reinforced base

[0037] (1) The proposed reinforcement ratio ρ is 0.4%. The reinforcement contribution rate is calculated according to formula 1: The concrete thermal shrinkage stress coefficient is calculated by formula 2: By c = 0.205, Φ = 0.0258, b = 9.0; According to formula 3, the horizontal crack spacing is calculated: It can be seen that L meets the requirement of 1-2.5m;

[0038] (2) By λ c = 0.205, b = 9.0, the crack width coefficient λ is obtained a =0.8, and the crack width is calculated according to formula 4, L b =(a c ΔT+ε h ) b L = (1 × 10 -5 ×35+0.0002)×0.8×2.45×10 3 =0.94; we can see that L b Meet the requirement of ≤1mm;

[0039] (3) From Φ = 0.0258, b = 9.0, we can find the steel bar temperature stress coefficient λ b =6.4, calculate the steel bar stress according to formula 5, δ = Es (a c ΔTλ a +a s ΔT)=200×10 3 (1×10 -5 ×35×6.4+9×10 -5 ×35)=318MPa≤335Mpa;

[0040] The above calculations meet the requirements, and it can be seen that the proposed reinforcement ratio ρ meets the requirements.

[0041] Example 2 Design of asphalt surface thickness

[0042] (1) The thickness of the asphalt surface layer was preliminarily determined to be 4-10, and the interlayer shear stress f between the asphalt surface layer and the continuous reinforcement base layer was calculated using BISAR software to be 0.302-0.169;

[0043] (2) The interlayer allowable shear stress between the asphalt surface layer and the continuous reinforced base layer is calculated according to Equation 6, where k is the maximum allowable shear stress between the asphalt surface layer and the continuous reinforced base layer at different vehicle speeds. v The value range is shown in the following table

[0044] Vehicle speed, km / h 120 100 80 60 No binder 5.01 4.79 4.51 3.96 With binder 5.51 5.25 4.96 4.29

[0045] Taking into account temperature, vertical load, shear rate, vehicle speed and other factors, the allowable shear stress between different interlayer binders is as follows:

[0046] No binder Hot Asphalt Emulsified asphalt [f] 0.621-0.683 0.697-0.811 0.781-0.864

[0047] It can be seen that when the thickness of the asphalt surface layer is in the range of 4-10cm, the interlayer shear stress is low and does not exceed the allowable interlayer shear stress, which meets the design requirements.

[0048] Example 3 Design of oil ratio of asphalt functional layer

[0049] (1) The asphalt mixture uses base asphalt 70# and the mineral material is limestone. According to the Marshall test, the optimal oil ratio of the asphalt mixture is 4.9%;

[0050] (2) Three oil ratios of asphalt mixture were selected to make specimens: 4.9%, 4.6%, and 4.3%, respectively. The total strain energy U at failure under the three oil ratios was obtained through experiments. T , and then calculate the anti-reflection crack factor of the specimen according to formula 7, J = ηU T B(da), specimen size is 40mm*40mm*250mm, incision width is 3mm, incision depth is 21.5mm, when a / d=0.54, η=2.

[0051] Oil Ratio 4.9％ 4.6％ 4.3％ J 500 485 454

[0052] It can be seen that when the minimum oil-to-stone ratio is 0.3% lower than the optimal oil-to-stone ratio, the anti-reflective crack factor J does not change much, and the specimens with oil-to-stone ratios of 4.6% and 4.9% were subjected to water immersion Marshall test, freeze-thaw splitting test machine water immersion and dispersion test, low-temperature bending test and anti-scouring test respectively. The experimental results can determine that the minimum oil-to-stone ratio can meet the anti-scouring and anti-reflective cracking performance of the asphalt functional layer.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A design and construction method for a continuously reinforced concrete pavement, characterized in that The following steps are involved: S1. Determine the longitudinal reinforcement ratio of the continuously reinforced base; specifically: (1) Preliminarily formulate the reinforcement ratio, calculate the transverse crack spacing L according to Formula 3, and when L < 1.0 m or L > 2.5 m, re-formulate the reinforcement ratio ρ until 1.0 m ≤ L ≤ 2.5 m. Where: ρ-reinforcement ratio; b-stress coefficient; Ks-bond stiffness coefficient; ds-steel diameter; Es-steel elastic modulus; Ec-concrete elastic modulus; The stress coefficient b is obtained by the steel reinforcement contribution rate Φ and the concrete thermal shrinkage stress coefficient λ c Sure: ρ-reinforcement ratio; Es-elastic modulus of steel bars; Ec-elastic modulus of concrete; ft-standard value of concrete tensile strength; a c -Concrete linear expansion coefficient; ΔT-temperature difference; ε h - Drying shrinkage strain of continuously reinforced concrete; (2) According to the reinforcement ratio determined in step (1), the crack width L is calculated according to formula 4: b , When L b >1mm, re-determine the reinforcement ratio until L b ≤1mm, L b =(a c ΔT+ε h )l b L-shaped4 λ b -crack width coefficient; a c -Concrete linear expansion coefficient; ΔT-temperature difference; ε h - Drying shrinkage strain of continuously reinforced concrete; (3) Based on the reinforcement ratio determined in step (2) and the steel stress δ calculated according to formula (5), when δ>335 MPa, the reinforcement ratio is re-determined until δ≤335 MPa; δ=Es(a c ΔTλ a +a s ΔT) formula5 Es-elastic modulus of steel bar; a c -concrete linear expansion coefficient; ΔT-temperature difference; λ a -Rebar temperature stress coefficient; a s - Coefficient of linear expansion of steel bars; S2. Determine the minimum oil ratio of the asphalt functional layer; specifically: (1) obtain the optimal oil ratio of the asphalt material according to the Marshall test, and prepare asphalt mixture specimens with different oil ratios based on the optimal oil ratio ±1%; (2) Calculate the anti-reflective crack factor J of each asphalt mixture specimen according to Formula 7; J=ηU T B(da) Formula 7 U T - total strain energy at failure; B- beam width; d- beam height; a- notch depth; when a / d = 0.54, η = 2; (3) Calculate the change rate of the anti-reflective cracking factor J of each asphalt mixture specimen and the specimen with the best oil ratio, so as to determine the minimum oil ratio of the asphalt functional layer; S3. Determine the thickness of the asphalt surface layer; S4. Arrange a continuous steel mesh on the base layer, set 2-4 anchor beams at the connecting ends of the base layer and other structures, pour concrete into the continuous steel mesh until a continuous reinforced base layer is formed with the ground beams cast with the anchor beams; lay an asphalt functional layer and an asphalt anti-skid layer in sequence on the continuous reinforced base layer.

2. The design and construction method of continuous reinforced concrete pavement according to claim 1 is characterized in that The crack width coefficient λ b , steel bar temperature stress coefficient λ a They are determined by the steel bar stiffness contribution rate Φ and the stress coefficient b respectively.

3. The design and construction method of the continuous reinforced concrete pavement according to claim 1 is characterized in that The S3 specifically includes: (1) preliminarily determining the reasonable thickness of the asphalt surface layer, and using BISAR software to calculate the interlayer shear stress f between the asphalt surface layer and the continuous reinforcement base layer; (2) Calculate the interlayer allowable shear stress [f] between the asphalt surface layer and the continuous reinforcement base layer according to Formula 6; k v - shear velocity correction factor; σ-vertical load; φ-internal friction angle of bonding material; C-cohesion of bonding material; k-interlayer shear strength coefficient (3) Check the shear stress, f≤[f].

4. The design and construction method of the continuous reinforced concrete pavement according to claim 3 is characterized in that The interlayer shear structure strength coefficient k=1.2 / A, where A is the road grade coefficient.

5. The design and construction method of the continuous reinforced concrete pavement according to claim 4 is characterized in that The ground beam in S4 is specifically as follows: a fixed steel cage is installed in the foundation, steel support brackets are tied on both sides and the upper end of the steel cage, and the steel cage is first cast in layers, and the height of the concrete in the foundation is roughly flush with the top surface of the base layer to form a whole.

6. A continuously reinforced concrete pavement, characterized in that: The method according to any one of claims 1 to 5 is used for construction.

7. A continuously reinforced concrete pavement according to claim 6, characterized in that: It includes a continuous reinforced base layer and an asphalt surface layer, wherein the asphalt surface layer includes an asphalt functional layer and an asphalt anti-skid layer arranged from bottom to top; the continuous reinforced base layer includes a concrete layer and a continuous steel mesh arranged in the concrete layer.

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