CN104805748A - Additional paving method for rigid road surface - Google Patents

Abstract

The invention discloses an additional paving method for a rigid road surface, aims to solve the problem that shear failure appears easily because a control effect cannot be played by taking deflection as a design index for additionally paving an asphalt layer for the rigid road surface and provides an additional paving method for the rigid road surface by taking maximum shearing stress of an additionally-paved layer as a control index, so that the additionally-paved layer is effectively prevented from shear failure. Besides, a rigid road surface additional paving design is equivalent to elastic half-space + rigid interlayer + asphalt layer, so a composite road surface structure additional paving design is simplified; the invention discloses the additional paving method for the rigid road surface based on the shear fatigue properties to improve a rigid road surface additional paving design system. Engineering practices show that a road surface structure obtained according to the additional paving method for the rigid road surface is good in service level, long in service life and wide in application prospect.

Description

A kind of rigid pavement add laying method

Technical field

The invention belongs to field of road, particularly a kind of rigid pavement add laying method.

Technical background

Since reform and opening-up, speedway is the major fields in China's infrastructure construction always; To the end of the year 2014, China will build the speedway be open to traffic and will breach 100,000 kilometers.Wherein, early stage speedway is based on cement concrete pavement.Road work person, in the Construction Practice of Lift of Cement on High-type rigid pavement, have accumulated rich experience, solves a large amount of technical problems.But from the speedway cement pavement behavior in service put into effect in recent years, part does not reach and has namely occurred more serious function decay and structural failure projected life, many design periods are the cement pavement of 15 years, namely occur in 5 ~ 8 years destroying on a large scale after open to traffic, cause huge economic loss and bad social influence.

Although China's cement pavement structure has the developing history of decades, but its method for designing be substantially the 1970s and 1980s in last century and the early 1990s a series of achievement in research basis on set up, be subject to the restriction of scientific and technological level at that time, the category of roads relied on is low, vehicular traffic load is little, the speed of service is slow, construction technology is backward.In recent years, along with the raising of expanding economy and technical level, road traffic condition there occurs great changes, and the capacity and level-of-service of part speedway can not satisfy the demands, and is badly in need of carrying out upgrading.

In the process of road surface upgrading, if cement concrete pavement in freeway well damage, usually need to process original road structure, then repaving asphalt coat.The deflection value of this composite pavement structure is less, and the existing design objective using flexure as repaving asphalt coat on cement concrete pavement, be difficult to play control action.There are some researches show, composite pavement structure is based on bitumen layer shear failure.Therefore, the rigid pavement construction design method that to propose with bitumen layer maximum shear stress be Con trolling index, can solve the problem that road surface deflection index cannot play control action.The generation that road structure based on rigid pavement Overlay design method design can effectively prevent shear failure and shear fatigue from destroying, thus improve service ability and the application life of road structure, have broad application prospects.

Summary of the invention

Based on above technical problem, what the invention provides a kind of rigid pavement adds laying method, and described method is Con trolling index based on bitumen layer maximum shear stress, solves the problem that road surface deflection cannot play control action; And rigid pavement Overlay design is equivalent to elastic half-space+rigid interlayer+bitumen layer, simplify composite pavement structure Overlay design.Engineering practice shows, adds that the road structure service level that laying method obtains is good, long service life according to rigid pavement, has broad application prospects.

The present invention is achieved through the following technical solutions above-mentioned purpose:

Rigid pavement add a laying method, concrete steps are as follows:

1) original road structure is equivalent to elastic half-space+rigid interlayer+bitumen layer, by modulus adjustment, the shearing stress distribution of former road structure and equivalent structure is consistent substantially;

2) under the totally continuous condition of interlayer, maximum shear stress τ in the bitumen layer being obtained said structure by mechanical analysis _max, E between overlay thickness h and concrete moduli ₀' between corresponding data; Return above-mentioned data, obtain maximum shear stress in bitumen layer, relation between overlay thickness and concrete moduli;

${\mathrm{\τ}}_{\max }=a-\frac{b}{\ln \left({E_0}^{\′}\right)}+\frac{c}{h^d}$

In formula: a, b, c, d are regression coefficient.

3) by laboratory test, determine the shear strength of the bituminous mixture that preparation overlays, shear fatigue life-span, returned out corresponding shear fatigue equation, determined shear strength structural coefficient K _twith allowable shearing stress [τ];

4) according to the maximum shear stress τ overlaying road structure _maxallowable shearing stress [τ] should be less than, obtain the overlay thickness of rigid pavement, thus overlay.

In one embodiment of the invention, step 1) in modulus adjustment be according to the regulation in bituminous pavement design for highway specification, the theoretical road pavement structure of multilayer elastic continuous system under the effect of two circle vertical uniform load is adopted to carry out mechanical response calculating, maximum shear stress numerical value in the bitumen layer obtaining equivalent structure, and in the bitumen layer that itself and original road structure are overlayed maximum shear stress and the regularity of distribution close.

In another embodiment of the invention, step 3) concrete steps for carry out lab shear strength test under 60 DEG C of conditions, measure the shear strength τ of bituminous mixture _f; Then shear fatigue test is carried out, respectively with shear strength τ _f0.2,0.3,0.4,0.5,0.6,0.7,0.8 times of stress ratio τ load, loading speed is 10HZ, and load mode is that proof stress loads, and measures shear fatigue life-span N _f, return out corresponding shear fatigue equation, determine shear strength structural coefficient K _t; Allowable shearing stress [τ] is by the shear strength τ measured _fwith shear strength structural coefficient K _tdetermine.

Detailed process is: by Orthogonal Rotational Regressive Tests data, obtains corresponding shear fatigue equation to be:

N _f＝mτ ^t

In formula: m, t are regression parameter;

N _ffor the shear fatigue life-span;

τ is the shear stress applied in shear fatigue test, MPa.

Can be obtained fom the above equation: $\mathrm{\τ}={\left(\frac{m}{N_f}\right)}^{-1/t}=m^{-1/t}{N_f}^{1/t}$

Work as N _fwhen=1, the shear strength regressand value τ under a load action _fc=m ^-1/t.K _tfor shear strength structural coefficient, by the method for this area routine, its value can be expressed as:

Then: $K_T=\frac{{\mathrm{\τ}}_{\mathrm{fc}}}{\mathrm{\τ}}=\frac{m^{-1/t}}{m^{-1/t}{N_f}^{1/t}}={N_f}^{-1/t}$

There are some researches show both at home and abroad, the not free interval of load pulse of indoor fatigue test, compared with the actual load action be subject to of road structure, Non-intermittent disadvantage in time, in the fatigue recovery of bituminous material, can cause fatigue Life to reduce 1/5.In addition, the stressed of road structure is 3 D complex stress, and in test, the stressed of test specimen is one dimension simple stress, causes be road surface actual life 1/7 ~ 1/3 fatigue life of test specimen, gets empirical value 1/6 in the present invention.Vehicle wheelmark breadth coefficient is generally 0.5.For shear failure, summer high temperature is unfavourable season, and generally in annual 60d, then the axle that laboratory test number of loading and traffic load produce carries the accumulative pass acting on number of times and is:

$N_f=\frac{1}{5}\×\frac{1}{6}\×0.5\×\frac{60}{365}{N}_e=0.00274N_e$

Inter-layer shearing strength structural coefficient can be modified to:

K _T＝N _f ^-1/t＝(0.00274N _e) ^-1/t＝0.00274 ^-1/tN _e ^-1/t

In formula: Ne is the accumulation equivalent axles of design;

Allowable shearing stress [τ] is by the shear strength τ measured _fwith shear strength structural coefficient K _tdetermine, as shown in Equation 6.

$[\mathrm{\τ}]=\frac{{\mathrm{\τ}}_f}{K_T}=\frac{{\mathrm{\τ}}_f}{{0.00274}^{-1/t}{N_e}^{-1/t}}=p{N_e}^{1/t}$

In formula: for regression parameter;

Owing to adopting above technical scheme, the present invention has following useful technique effect:

(1) rigid pavement Overlay design is equivalent to elastic half-space+rigid interlayer+bitumen layer, simplifies composite pavement structure Overlay design.

(2) to propose with bitumen layer maximum shear stress be Con trolling index, and rigid pavement structure adds laying method, solves the problem that road surface deflection is difficult to play control action.

(3) generation that the road structure overlaying method design based on rigid pavement can effectively prevent shearing and shear fatigue from destroying, improves service ability and the application life of road structure, has broad application prospects.

Accompanying drawing explanation

Fig. 1 equivalent structure and former road structure repaving asphalt coat maximum shear stress are along width of roadway Regularity Changes, and figure center line 1,3,5 represents the upper, middle and lower surface layer of former road structure respectively; Line 2,4,6 represents the upper, middle and lower surface layer of equivalent structure respectively;

Under Fig. 2 different-thickness in bitumen layer maximum shear stress with the Changing Pattern of concrete moduli;

The shear fatigue life-span of bituminous mixture under the different shear stress of Fig. 3;

Fig. 4 repaving asphalt coat road surface deflection is with the Changing Pattern of rigid interlayer modulus.

Embodiment 1

(1) the original cement concrete pavement structure of certain speedway is: soil matrix+18cm4% cement stabilized macadam subbase+18cm6% cement stabilized macadam base+1cm pitch table place waterproofing course+28cmC35 Portland Cement Concrete Surface Course.Be open to traffic over more than 10 year, the far super expection of the traffic volume, occurred the multiple damage-form comprising shear failure, pavement disease is serious, repaiies and is difficult to Deterministic service level with the maintenance measure such as light maintenance, therefore need repaving asphalt coat on original road structure in only leaning on.

(2) existing research and engineering practice show, in the totally continuous situation of interlayer, composite asphalt pavement structure is based on bitumen layer shear failure.The bitumen layer of original road structure and upper overlay thereof is equivalent to the equivalent structure of elastic half-space+rigid interlayer+asphalt surface course.As shown in Figure 1, original road structure repaving asphalt coat and equivalent structure make maximum shear stress and the regularity of distribution thereof in bitumen layer substantially be consistent by the adjustment of each pavement layer modulus and thickness.The method of modulus adjustment is according to the regulation in bituminous pavement design for highway specification, the theoretical road pavement structure of multilayer elastic continuous system under the effect of two circle vertical uniform load is adopted to carry out mechanical response calculating, maximum shear stress numerical value in the bitumen layer obtaining equivalent structure, and in the bitumen layer that itself and original road structure are overlayed maximum shear stress and the regularity of distribution close.

(3) under the totally continuous condition of interlayer, maximum shear stress τ in the bitumen layer that can be obtained different structure by above-mentioned mechanical analysis _max, E between overlay thickness h and concrete moduli ₀' between corresponding relation.As shown in Figure 2, adopt the data regression statistical method that this area is conventional, return above-mentioned data, set up maximum shear stress in bitumen layer, relation between overlay thickness and concrete moduli, see formula 1.

${\mathrm{\τ}}_{\max }=0.3-\frac{0.9}{\ln \left({E_0}^{\′}\right)}+\frac{0.071}{h^{0.5}}---\left(1\right)$

In formula: τ _maxfor bitumen layer maximum shear stress, MPa;

E ₀' be elastic half-space concrete moduli, MPa;

H is overlay thickness, cm

(4) shear strength structural coefficient K is determined _twith allowable shearing stress [τ].Under 60 DEG C of conditions, carry out lab shear strength test, measure the shear strength τ of the bituminous mixture that preparation overlays _f; Then shear fatigue test is carried out, respectively with shear strength τ _f0.2,0.3,0.4,0.5,0.6,0.7,0.8 times of stress ratio τ load, loading speed is 10HZ, and load mode is that proof stress loads, and measures shear fatigue life-span N _f, return out corresponding shear fatigue equation, derivation shear strength structural coefficient K _t.

For AC-20C+SBS bituminous mixture, measure shear strength τ _ffor 1.065MPa, the shear fatigue life-span obtained under 0.2,0.3,0.4,0.5,0.6,0.7,0.8 times of stress ratio by shear fatigue test.The shear fatigue life-span under different shear stress as shown in Figure 3, Orthogonal Rotational Regressive Tests data, obtaining corresponding shear fatigue equation is:

N _f＝21.3398τ ^-6.89(2)

In formula: N _ffor the shear fatigue life-span;

τ is the shear stress applied in shear fatigue test, MPa.Can be obtained fom the above equation:

$\mathrm{\τ}={\left(\frac{21.3398}{N_f}\right)}^{\frac{1}{6.89}}=1.559{N_f}^{-0.145}---\left(3\right)$

Work as N _fwhen=1, according to the shear strength regressand value τ under a load action _fc=m ^-1/tdraw 1.559.K _tfor shear strength structural coefficient, by the method for this area routine, its value can be expressed as:

Then: $K_T=\frac{{\mathrm{\τ}}_{\mathrm{fc}}}{\mathrm{\τ}}=\frac{1.559}{1.559{N_f}^{-0.145}}={N_f}^{0.145}---\left(4\right)$

K _tfor shear strength structural coefficient.There are some researches show both at home and abroad, the not free interval of load pulse of indoor fatigue test, compared with the actual load action be subject to of road structure, Non-intermittent disadvantage in time, in the fatigue recovery of bituminous material, can cause fatigue Life to reduce 1/5.In addition, the stressed of road structure is 3 D complex stress, and in test, the stressed of test specimen is one dimension simple stress, causes be road surface actual life 1/7 ~ 1/3 fatigue life of test specimen, gets 1/6 in the present invention.Vehicle wheelmark breadth coefficient gets 0.5.For shear failure, summer high temperature is unfavourable season, and generally in annual 60d, then the axle that laboratory test number of loading and traffic load produce carries the accumulative pass acting on number of times and is:

$N_f=\frac{1}{5}\×\frac{1}{6}\×0.5\×\frac{60}{365}{N}_e=0.00274N_e---\left(5\right)$

Inter-layer shearing strength structural coefficient can be modified to: K _t=N _f ^0.145=0.419N _e ^0.145

In formula: Ne is the accumulation equivalent axles of design

Allowable shearing stress [τ] is by the shear strength τ measured _fwith shear strength structural coefficient K _tdetermine, as shown in Equation 6.

$\left[\mathrm{\τ}\right]=\frac{{\mathrm{\τ}}_f}{K_T}=2.54{N_e}^{-0.145}---\left(6\right)$

(5) determination of overlay thickness.The relation τ of allowable shearing stress should be less than according to overlay maximum shear stress _max≤ [τ], the above-mentioned equation of simultaneous, and determine whether the overlay thickness designed meets the requirement of design.Such as the modulus E of elastic half-space ₀' value for accumulation equivalent axles that 7000MPa designs be 2,500 ten thousand times time, consider the actual conditions that China is current, 19cm is got in the thickness suggestion of bitumen layer.

Engineering practice shows, effectively can prevent the generation of overlay shear failure, improve application life and the service level of road structure, have broad application prospects according to the road structure of rigid pavement Overlay design method design.

In sum, the invention solves the problem that road surface deflection index in the Overlay design method of conventional rigid road surface is difficult to play control action.The present invention much larger than the bitumen layer modulus overlayed and the modulus of semi-rigid type base under it, is seen as rigid interlayer according to the modulus of cement concrete layer.And rigid pavement Overlay design is equivalent to elastic half-space+rigid interlayer+bitumen layer, simplify rigid pavement structure Overlay design, the rigid pavement Overlay design method that to propose with bitumen layer maximum shear stress be Con trolling index.Engineering practice shows, the road structure based on rigid pavement Overlay design method design effectively can prevent the generation of shear failure, improves service ability and the application life of road structure, has broad application prospects.

Embodiment 2

Because the modulus of cement concrete layer is much larger than the bitumen layer modulus overlayed and the modulus of semi-rigid type base under it, can be regarded as rigid interlayer.Adopt the computational methods that this area is conventional, get different rigid interlayer modulus values, according to the regulation in bituminous pavement design for highway specification, adopt the road surface deflection of the multilayer elastic continuous system theory calculate road structure under the effect of two circle vertical uniform load, obtain cement pavement structure repaving asphalt coat layer table deflection value with rigid interlayer modulus value Changing Pattern, see Fig. 4.Mechanical calculation and theory analysis show, the deflection value of bitumen layer is less, and increase along with rigid interlayer modulus and reduce, and tend towards stability gradually, are difficult to play control action using flexure as the design objective of asphalt pavement structure on rigid interlayer.

Content of the present invention merely illustrates some claimed specific embodiments; one of them or more described technical characteristic can be combined with arbitrary one or more technical scheme in technical scheme; these technical schemes obtained through combination also in the application's protection domain, just as these technical schemes obtained through combination in the disclosure of invention concrete record.

Claims (5)

1. a rigid pavement add laying method, it is characterized in that, described method is Con trolling index based on bitumen layer maximum shear stress, and rigid pavement Overlay design is equivalent to elastic half-space+rigid interlayer+bitumen layer, thus obtain the thickness of overlay, overlay.

2. road surface according to claim 1 adds laying method, it is characterized in that, preferably, it is as follows that described road surface adds laying method concrete steps:

1) original road structure is equivalent to elastic half-space+rigid interlayer+bitumen layer, by modulus adjustment, the shearing stress distribution of former road structure and equivalent structure is consistent substantially;

2) under the totally continuous condition of interlayer, maximum shear stress τ in the bitumen layer being obtained said structure by mechanical analysis _max, E between overlay thickness h and concrete moduli ₀' between corresponding data; Return above-mentioned data, obtain maximum shear stress in bitumen layer, relation between overlay thickness and concrete moduli;

${\mathrm{\τ}}_{\max }=a-\frac{b}{\ln \left({E_0}^{\′}\right)}+\frac{c}{h^d}$

In formula: a, b, c, d are regression coefficient;

3) by laboratory test, determine the shear strength of the bituminous mixture that preparation overlays, shear fatigue life-span, returned out corresponding shear fatigue equation, determined shear strength structural coefficient K _twith allowable shearing stress [τ];

4) according to the maximum shear stress τ overlaying road structure _maxallowable shearing stress [τ] should be less than, obtain the overlay thickness of rigid pavement, thus overlay.

3. road surface according to claim 2 adds laying method, it is characterized in that, step 1) in modulus adjustment be according to the regulation in bituminous pavement design for highway specification, the theoretical road pavement structure of multilayer elastic continuous system under the effect of two circle vertical uniform load is adopted to carry out mechanical response calculating, maximum shear stress numerical value in the bitumen layer obtaining equivalent structure, and in the bitumen layer that itself and original road structure are overlayed maximum shear stress and the regularity of distribution close.

4. road surface according to claim 2 adds laying method, it is characterized in that, step 3) concrete steps for carry out lab shear strength test under 60 DEG C of conditions, measure the shear strength τ of bituminous mixture _f; Then shear fatigue test is carried out, respectively with shear strength τ _f0.2,0.3,0.4,0.5,0.6,0.7,0.8 times of stress ratio τ load, loading speed is 10HZ, and load mode is that proof stress loads, and measures shear fatigue life-span N _f, return out corresponding shear fatigue equation, determine shear strength structural coefficient K _t; Allowable shearing stress [τ] is by the shear strength τ measured _fwith shear strength structural coefficient K _tdetermine.

5. road surface according to claim 4 adds laying method, it is characterized in that, the procurement process of described [τ] is:

A) by Orthogonal Rotational Regressive Tests data, obtaining corresponding shear fatigue equation is:

N _f＝mτ ^t

In formula: m, t are regression parameter;

N _ffor the shear fatigue life-span;

τ is the shear stress applied in shear fatigue test, MPa

Can be obtained fom the above equation: $\mathrm{\τ}={\left(\frac{m}{N_f}\right)}^{-1/t}=m^{-1/t}{N_f}^{1/t};$

B) N is worked as _fwhen=1, the shear strength regressand value τ under a load action _fc=m ^-1/t, K _tfor shear strength structural coefficient, by the method for this area routine, its value can be expressed as:

Then: $K_T=\frac{{\mathrm{\τ}}_{\mathrm{fc}}}{\mathrm{\τ}}=\frac{m^{-1/t}}{m^{-1/t}{N_f}^{1/t}}={N_f}^{-1/t};$

C) according to the difference between actual surface conditions and specimen test, to N _fcorrect, specific as follows:

Thus can by K _tbe corrected to:

K _T＝N _f ^-1/t＝(0.00274N _e) ^-1/t＝0.00274 ^-1/tN _e ^-1/t；

D) allowable shearing stress [τ] is by the shear strength τ measured _fwith shear strength structural coefficient K _tdetermine, be shown below:

$\left[\mathrm{\τ}\right]=\frac{{\mathrm{\τ}}_f}{K_T}=\frac{{\mathrm{\τ}}_f}{{0.00274}^{-1/t}{N_e}^{-1/t}}={{\mathrm{pN}}_e}^{1/t}$

In formula: $p=\frac{{\mathrm{\τ}}_f}{{0.00274}^{-1/t}},$ For regression parameter.