CN104264560A - Method for discriminating application range of flexible surface under overload condition - Google Patents

Abstract

The invention discloses a method for discriminating the application range of a flexible surface under the overload condition. According to the method, the flexible surface is introduced, and the traditional method that only a semi-rigid surface is adopted, and the thickness of a base layer is increased to avoid overloads is changed. Under the same traffic flow, overload rate and overload limit, the fatigue service life period of the semi-rigid surface is compared with that of the flexible surface, and therefore when the flexible surface or the semi-rigid surface is adopted is discriminated. According to the method, the traditional method that only the semi-rigid surface is adopted, and the thickness of the base layer is increased to avoid the overloads is changed, and the flexible surface is introduced. Under the same traffic flow, overload rate and overload limit, the fatigue service life period of the semi-rigid surface is compared with that of the flexible surface, and therefore the application range of the flexible surface and the semi-rigid surface is provided. Under the same condition, for the urban road with the large overload rate and overload limit, a flexible surface structure should be adopted by a surface structure, and therefore early damage caused by the overloads is avoided; meanwhile, the cost of later maintenance is reduced, and the fatigue service life period is prolonged.

Description

The method of discrimination of the flexible pavement scope of application under a kind of overload condition

Technical field

The present invention relates to highways and urban roads field of engineering technology, particularly relate to the method for discrimination of the flexible pavement scope of application under a kind of overload condition.

Background technology

In recent years, in order to solve by this problem become increasingly conspicuous of semi-rigid asphalt pavement early damage brought that overloads, China starts the correlative study that Foreign Experience starts to carry out flexible pavement, and built up some Experiment Roads, but because China's Overload Traffic actual conditions are with different abroad, mostly attach most importance to, overload compound traffic, therefore Pavement on Semi-rigid Type Base can be replaced to overload this problem to tackle China for Flexible Pavement Structure, need by theoretical and actual dual demonstration.

In current China urban road and highway transportation, overload condition is serious, in order to tackle overload, the measure that traffic is generally taked is that the axle of restriction vehicle carries, the measure that designing unit generally takes increases groundwork thickness on the basis of traditional semi-rigid pavement, cause construction costs to increase on the one hand, then effectively can not delay the generation of early damage on the other hand.

The external research having carried out long-life flexible pavement, segment path builds up flexible pavement, but Chinese practice adopts the road of flexible pavement less, especially under overload condition; For the road structure form under overload condition, China generally adopts rigid pavement or semi-rigid pavement at present, does not adopt flexible pavement.

For the scope of application of semi-rigid pavement and flexible pavement, under different overloading ratio and overload volume situation, not yet systematic research at present, also not systematic method of discrimination, cause flexible pavement superior function under undesirably heavy loads to can not get due accreditation.Therefore, under research overload condition, the method for discrimination of the flexible pavement scope of application, instructs current designs, has very important significance.

Summary of the invention

In view of this, the object of this invention is to provide the method for discrimination of the flexible pavement scope of application under a kind of overload condition, to solve deficiency of the prior art.

In order to achieve the above object, the object of the invention is to be achieved through the following technical solutions:

A method of discrimination for the flexible pavement scope of application under overload condition, wherein, comprises the following steps:

A. collect representative vehicle, traffic data, calculate accumulated standard axle time Ne under non-overload condition; Determine overload volume and overloading ratio, and representative vehicle conversion factor equvalent axle load under calculating overload condition;

B. carry out Pavement Structure Design according to category of roads, surface layer substrate type, Rebound Modulus of Subgrade, accumulated standard axle time Ne, draft Semi-Rigid Pavement Structure and Flexible Pavement Structure;

C. the design road day stoichiometric standard axle calculated based on different designs index under overload condition carries effect number of times: for Semi-Rigid Pavement Structure, and calculating with road surface deflection is that the bicycle road of index adds up equivalent axle load effect times N _1w, to calculate with tensile stress at the bottom of semi-rigid type base be index, and bicycle road adds up equivalent axle load effect times N _1c; For Flexible Pavement Structure, calculating with road surface deflection is that the bicycle road of index adds up equivalent axle load effect times N _2w, to calculate with tensile stress at the bottom of flexbile base be index, and bicycle road adds up equivalent axle load effect times N _2c;

D. according to the effect of carrying of day stoichiometric standard axle number of times, N _1w, N _1c, determine that Semi-Rigid Pavement Structure take road surface deflection as the Y tired service life of index _1w, with the Y to be index tired service life of tensile stress at the bottom of semi-rigid type base _1c; According to the effect of carrying of day stoichiometric standard axle number of times, N _2w, N _2c, determine that Flexible Pavement Structure take road surface deflection as the Y tired service life of index _2w, with the Y to be index tired service life of tensile stress at the bottom of semi-rigid type base _2c;

E. for Semi-Rigid Pavement Structure, Y is compared _1wand Y _1csize, get the tired service life Y1 of the little person of its intermediate value as Semi-Rigid Pavement Structure; For Flexible Pavement Structure, compare Y _2wand Y _2csize, get the tired service life Y2 of the little person of its intermediate value as Flexible Pavement Structure;

F. compare Semi-Rigid Pavement Structure tired service life Y1 and Flexible Pavement Structure tired service life Y2 size, if Y1 > Y2, under determining overload condition, adopt Semi-Rigid Pavement Structure; If Y2 > is Y1, under determining overload condition, adopt Flexible Pavement Structure.

The method of discrimination of the flexible pavement scope of application under above-mentioned overload condition, wherein, under overload condition, the computational process of representative vehicle conversion factor equvalent axle load is as follows:

If overload volume is γ, conversion factor equvalent axle load N is calculated as follows:

1) with when at the bottom of flexure or flexbile base, tensile stress is for index, when overload volume is γ, conversion factor equvalent axle load N:

$N=\underset{i=1}{\overset{K}{\mathrm{\Σ}}}{C}_1{C}_2{\left(\frac{\mathrm{\γ}{P}_i}{P}\right)}^a---\left(1\right)$

In formula: N---conversion factor equvalent axle load;

P---single shaft two-wheel group 100kN;

P _i---carried (kN) by the axle of the single shaft i of conversion representative vehicle;

C ₁---wheels coefficient;

C ₂---axle-number coefficient.

a——γP _i<130KN，a＝4.35；γP _i>130KN，a＝5；

2) with tensile stress at the bottom of semi-rigid type base for index time, the conversion factor equvalent axle load N of representative vehicle when overload volume is γ:

$N=\underset{i=1}{\overset{K}{\mathrm{\&Sigma;}}}{C}_1{C}_2{\left(\frac{\mathrm{\&gamma;}{P}_i}{P}\right)}^b---\left(2\right)$

In formula: N---conversion factor equvalent axle load;

P---single shaft two-wheel group 100kN;

P _i---carried (kN) by the axle of the single shaft i of conversion representative vehicle;

C ₁---wheels coefficient;

C ₂---axle-number coefficient;

b——γP _i<130KN，b＝8；γP _i>130KN，b＝9。

Compared with the prior art, beneficial effect of the present invention is:

--change traditional only adopting semi-rigid pavement and increase the method that groundwork thickness tackles overload, introduce flexible pavement; In the identical magnitude of traffic flow, overloading ratio, overload volume situation, by the contrast of semi-rigid pavement and flexible pavement length tired service life, the scope of application of flexible pavement and semi-rigid pavement is proposed;

--under the same conditions, for overloading ratio, the larger urban road of overload volume, road structure should adopt Flexible Pavement Structure, to avoid the early damage caused that overloads, reduces the cost of late maintaining simultaneously, extends tired service life.

Accompanying drawing explanation

The accompanying drawing forming a part of the present invention is used to provide a further understanding of the present invention, and schematic description and description of the present invention, for explaining the present invention, does not form inappropriate limitation of the present invention.In the accompanying drawings:

Fig. 1 is the logic flow schematic diagram of the method for discrimination of the flexible pavement scope of application under overload condition of the present invention.

Detailed description of the invention

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.

It should be noted that, when not conflicting, the embodiment in the present invention and the feature in embodiment can combine mutually.

Under overload condition of the present invention, the method for discrimination of the flexible pavement scope of application introduces flexible pavement, changes traditional only adopting semi-rigid pavement and increase the method that groundwork thickness tackles overload.In the identical magnitude of traffic flow, overloading ratio, overload volume situation, by the contrast of semi-rigid pavement and flexible pavement size tired service life, judge when adopt flexible pavement or semi-rigid pavement.Wherein, the major control factors of overload adopts overload volume and overloading ratio, and semi-rigid pavement and flexible pavement contrast index tired service life: tensile stress at the bottom of layer, flexure.Overloading ratio is the percentage that overloaded vehicle number accounts for all vehicle numbers, and rebuilt pavement can obtain according to site road axial Load investigation, and newly-built road can obtain according to present situation periphery road network axial Load investigation conclusion.Overload volume rebuilt pavement is that overload axletree that site road axial Load investigation obtains carries gross weight and exceedes the percentage that its corresponding representative vehicle axle carries, and newly-built road can obtain according to present situation periphery road network axial Load investigation conclusion.

For reply overload condition, introduce flexible pavement, contrast semi-rigid pavement.In the identical traffic volume, overloading ratio, overload volume situation, number of times is carried by calculating stoichiometric standard axle, semi-rigid pavement and tired service life corresponding to flexible pavement, differentiate the length tired service life of two kinds of road structures, determine to adopt flexible pavement or semi-rigid pavement.

With reference to Fig. 1, under overload condition of the present invention, the method for discrimination of the flexible pavement scope of application, comprises the following steps:

G. collect representative vehicle, traffic data, calculate accumulated standard axle time Ne under non-overload condition; Determine overload volume and overloading ratio, and representative vehicle conversion factor equvalent axle load under calculating overload condition;

H. carry out Pavement Structure Design according to category of roads, surface layer substrate type, Rebound Modulus of Subgrade, accumulated standard axle time Ne, draft Semi-Rigid Pavement Structure and Flexible Pavement Structure;

Specific design flow process is carried out according to " town road pavement design specification " (CJJ 169-2012) and " bituminous pavement design for highway specification " (JTG D50-2006) completely, this part content belong to those skilled in the art be familiar with, specifically describe as follows:

(1) according to designing requirement, a car accumulated standard axle time Ne in design period is calculated respectively by flexure or tensile stress at the bottom of layer index, determine category of roads, corresponding Semi-Rigid Pavement Structure and Flexible Pavement Structure two kinds of structures calculate corresponding design deflection value and allowable tensile stress respectively; (2) according to category of roads determination roadbase backfill modulus design load; (3) according to regional experience, corresponding Semi-Rigid Pavement Structure and Flexible Pavement Structure two kinds of structures draft several feasible Pavement Structure Combination and thickness schemes separately respectively, the material selected according to engineering determines the compression rebound modulu, cleavage strength etc. of each structural material, determines each deck design parameters; (4) multilayer elastic system Theoretical Design program computation or checking computations road surface thickness is adopted according to parameter.

I. the design road day stoichiometric standard axle calculated based on different designs index under overload condition carries effect number of times: for Semi-Rigid Pavement Structure, and calculating with road surface deflection is that the bicycle road of index adds up equivalent axle load effect times N _1w, to calculate with tensile stress at the bottom of semi-rigid type base be index, and bicycle road adds up equivalent axle load effect times N _1c; For Flexible Pavement Structure, calculating with road surface deflection is that the bicycle road of index adds up equivalent axle load effect times N _2w, to calculate with tensile stress at the bottom of flexbile base be index, and bicycle road adds up equivalent axle load effect times N _2c;

J. according to the effect of carrying of day stoichiometric standard axle number of times, N _1w, N _1c, determine that Semi-Rigid Pavement Structure take road surface deflection as the Y tired service life of index _1w, with the Y to be index tired service life of tensile stress at the bottom of semi-rigid type base _1c; According to the effect of carrying of day stoichiometric standard axle number of times, N _2w, N _2c, determine that Flexible Pavement Structure take road surface deflection as the Y tired service life of index _2w, with the Y to be index tired service life of tensile stress at the bottom of semi-rigid type base _2c;

K. for Semi-Rigid Pavement Structure, Y is compared _1wand Y _1csize, get the tired service life Y1 of the little person of its intermediate value as Semi-Rigid Pavement Structure; For Flexible Pavement Structure, compare Y _2wand Y _2csize, get the tired service life Y2 of the little person of its intermediate value as Flexible Pavement Structure;

L. compare Semi-Rigid Pavement Structure tired service life Y1 and Flexible Pavement Structure tired service life Y2 size, if Y1 > Y2, under determining overload condition, adopt Semi-Rigid Pavement Structure; If Y2 > is Y1, under determining overload condition, adopt Flexible Pavement Structure.

Wherein, under overload condition, the computational process of representative vehicle conversion factor equvalent axle load is as follows:

If the overload volume of certain representative vehicle is γ, conversion factor equvalent axle load N is calculated as follows:

1) with when at the bottom of flexure or flexbile base, tensile stress is for index, when overload volume is γ, conversion factor equvalent axle load N:

$N=\underset{i=1}{\overset{K}{\mathrm{\&Sigma;}}}{C}_1{C}_2{\left(\frac{\mathrm{\&gamma;}{P}_i}{P}\right)}^a---\left(1\right)$

In formula: N---conversion factor equvalent axle load;

P---single shaft two-wheel group 100kN;

P _i---carried (kN) by the axle of the single shaft i of conversion representative vehicle;

C ₁---wheels coefficient;

C ₂---axle-number coefficient.

a——γP _i<130KN，a＝4.35；γP _i>130KN，a＝5；

2) with tensile stress at the bottom of semi-rigid type base for index time, the conversion factor equvalent axle load N of representative vehicle when overload volume is γ:

$N=\underset{i=1}{\overset{K}{\mathrm{\&Sigma;}}}{C}_1{C}_2{\left(\frac{\mathrm{\&gamma;}{P}_i}{P}\right)}^b---\left(2\right)$

In formula: N---conversion factor equvalent axle load;

P---single shaft two-wheel group 100kN;

P _i---carried (kN) by the axle of the single shaft i of conversion representative vehicle;

C ₁---wheels coefficient;

C ₂---axle-number coefficient;

b——γP _i<130KN，b＝8；γP _i>130KN，b＝9。

The present invention changes traditional only adopting semi-rigid pavement and increase the method that groundwork thickness tackles overload, introduces flexible pavement; In the identical magnitude of traffic flow, overloading ratio, overload volume situation, by the contrast of semi-rigid pavement and flexible pavement length tired service life, the scope of application of flexible pavement and semi-rigid pavement is proposed.In addition, under the same conditions, for overloading ratio, the larger urban road of overload volume, road structure should adopt Flexible Pavement Structure, to avoid the early damage caused that overloads, reduces the cost of late maintaining simultaneously, extends tired service life.

Be described in detail specific embodiments of the invention above, but the present invention is not restricted to specific embodiment described above, it is just as example.To those skilled in the art, any equivalent modifications and substitute also all among category of the present invention.Therefore, equalization conversion done without departing from the spirit and scope of the invention and amendment, all should contain within the scope of the invention.

Claims (2)

1. the method for discrimination of the flexible pavement scope of application under overload condition, is characterized in that, comprise the following steps:

A. collect representative vehicle, traffic data, calculate accumulated standard axle time Ne under non-overload condition; Determine overload volume and overloading ratio, and representative vehicle conversion factor equvalent axle load under calculating overload condition;

B. carry out Pavement Structure Design according to category of roads, surface layer substrate type, Rebound Modulus of Subgrade, accumulated standard axle time Ne, draft Semi-Rigid Pavement Structure and Flexible Pavement Structure;

C. the design road day stoichiometric standard axle calculated based on different designs index under overload condition carries effect number of times: for Semi-Rigid Pavement Structure, and calculating with road surface deflection is that the bicycle road of index adds up equivalent axle load effect times N _1w, to calculate with tensile stress at the bottom of semi-rigid type base be index, and bicycle road adds up equivalent axle load effect times N _1c; For Flexible Pavement Structure, calculating with road surface deflection is that the bicycle road of index adds up equivalent axle load effect times N _2w, to calculate with tensile stress at the bottom of flexbile base be index, and bicycle road adds up equivalent axle load effect times N _2c;

D. according to the effect of carrying of day stoichiometric standard axle number of times, N _1w, N _1c, determine that Semi-Rigid Pavement Structure take road surface deflection as the Y tired service life of index _1w, with the Y to be index tired service life of tensile stress at the bottom of semi-rigid type base _1c; According to the effect of carrying of day stoichiometric standard axle number of times, N _2w, N _2c, determine that Flexible Pavement Structure take road surface deflection as the Y tired service life of index _2w, with the Y to be index tired service life of tensile stress at the bottom of semi-rigid type base _2c;

E. for Semi-Rigid Pavement Structure, Y is compared _1wand Y _1csize, get the tired service life Y1 of the little person of its intermediate value as Semi-Rigid Pavement Structure; For Flexible Pavement Structure, compare Y _2wand Y _2csize, get the tired service life Y2 of the little person of its intermediate value as Flexible Pavement Structure;

F. compare Semi-Rigid Pavement Structure tired service life Y1 and Flexible Pavement Structure tired service life Y2 size, if Y1 > Y2, under determining overload condition, adopt Semi-Rigid Pavement Structure; If Y2 > is Y1, under determining overload condition, adopt Flexible Pavement Structure.

2. the method for discrimination of the flexible pavement scope of application under overload condition according to claim 1, it is characterized in that, under overload condition, the computational process of representative vehicle conversion factor equvalent axle load is as follows:

If overload volume is γ, conversion factor equvalent axle load N is calculated as follows:

1) with when at the bottom of flexure or flexbile base, tensile stress is for index, when overload volume is γ, conversion factor equvalent axle load N:

$N=\underset{i=1}{\overset{K}{\mathrm{\&Sigma;}}}{C}_1{C}_2{\left(\frac{\mathrm{\&gamma;}{P}_i}{P}\right)}^a---\left(1\right)$

In formula: N---conversion factor equvalent axle load;

P---single shaft two-wheel group 100kN;

P _i---carried (kN) by the axle of the single shaft i of conversion representative vehicle;

C ₁---wheels coefficient;

C ₂---axle-number coefficient.

a——γP _i<130KN，a＝4.35；γP _i>130KN，a＝5；

2) with tensile stress at the bottom of semi-rigid type base for index time, the conversion factor equvalent axle load N of representative vehicle when overload volume is γ:

$N=\underset{i=1}{\overset{K}{\mathrm{\&Sigma;}}}{C}_1{C}_2{\left(\frac{\mathrm{\&gamma;}{P}_i}{P}\right)}^b---\left(2\right)$

In formula: N---conversion factor equvalent axle load;

P---single shaft two-wheel group 100kN;

P _i---carried (kN) by the axle of the single shaft i of conversion representative vehicle;

C ₁---wheels coefficient;

C ₂---axle-number coefficient;

b——γP _i<130KN，b＝8；γP _i>130KN，b＝9。