CN104462843A - Fatigue life prediction method for high-modulus asphalt mixture pavement - Google Patents

Abstract

The invention provides a fatigue life prediction method for a high-modulus asphalt mixture pavement. The method comprises the steps that structural temperature distribution, pavement material dynamic modulus and temperature axle load distribution of the high-modulus asphalt mixture pavement serve as basis parameters; a fatigue strain equation is fit according to an indirect tension fatigue test result; ANSYS software is adopted to construct a pavement structure finite element model, and maximum tension strain of a bottom layer at different axle load levels in different temperature regions is calculated; according to the Miner fatigue cumulative damage rule, fatigue cumulative damage results of a high-modulus asphalt mixture at different axle loads and different temperatures are calculated according to the formula: . The fatigue life prediction method for the high-modulus asphalt mixture pavement has the technical advantages that temperature gradients and axle load distribution of the asphalt mixture pavement are fully considered, an accurate prediction model is established, the process and law of fatigue attenuation of the asphalt mixture are accurately described, the application range is wide, and calculation results are reliable, so a more reliable method is provided for structural design of the asphalt pavement.

Description

A kind of High Modulus Asphalt Mixture fatigue life of pavement Forecasting Methodology

Invention field

The present invention relates to road project technical field, be related specifically to a kind of High Modulus Asphalt Mixture fatigue life of pavement Forecasting Methodology.

Background technology

High Modulus Asphalt Mixture is a kind of novel Load materials, has outstanding pavement performance.The design concept of High Modulus Asphalt Mixture is the modulus by improving bituminous concrete, thus improve road surface high temperature deformation resistance ability, the strain that under minimizing Vehicle Load, bituminous concrete produces, improve the fatigue behaviour of bituminous concrete, reach the serviceable life extending road surface, the effect of improving service quality.

High Modulus Asphalt Mixture (HMAM) comes across France the 1980s, is punished the name acquiring of gravel (GBTHP) Patents titled with road surface special asphalt.Definition according in French NF P-140 standard: only have when dynamic modulus E* 15 DEG C, the condition of 10Hz just can be called as High Modulus Asphalt Mixture when being issued to more than 14000MPa.

At present, the mode improving asphalt modulus in the world mainly contains two kinds, and a kind of is the label reducing asphalt from asphalt mixture, adopts the pitch that viscosity is larger; Another kind is then mix modifier outside adding in asphalt.The present invention is mainly for the Forecasting Methodology of High Modulus Asphalt Mixture fatigue lifetime of adding PR-module high-modulus modifier in matrix pitch.

The research of fatigue performance of asphalt mixture forecast model has the history in more than 40 years abroad, mainly contains Univ Nottingham UK, markon Fu Funiya university, Royal Dutch Group, Ohio, USA university etc.

As far back as 1971 and 1973, the Carl L.Monismith in Berkeley branch school, University of California and the P.S.Pell of Nottingham university establishes the classical forecast model by the fatigue behaviour under strain controlling and Stress Control torture test pattern respectively, is still adopting so far in the prediction of fatigue behaviour of single asphalt type.

Carl L.Monismith in 1985 sets up prediction of fatigue behaviour model and is taken in as the factor that affects fatigue lifetime by the initial stiffness modulus of asphalt, the initial stiffness modulus of asphalt is then the overall target of multiple factors vary such as reflection bitumen stiffness, mixture gradation, voidage, an asphalt content, can reflect the fatigue properties of dissimilar asphalt to a certain extent.This forecast model is learned to be used in the design specifications of (Asphalt Institute) at Royal Dutch Shell (Shell Bitumen) and pitch earth.

University of Nottingham also establishes the relation of stretching strain, Fatigue Load number of times, bitumen content and softening point.

Markon Fu Niya university of U.S. Berkeley has carried out a large amount of desk research, and is verified indoor Fatigue Regularity by outdoor full scale test.At " SHRP " in the works, University of California has analysed in depth again the various factors affecting fatigue performance of asphalt mixture, comprise: on the basis of the forming method of test specimen, load mode, compound variable (asphalt viscosity, asphalt content, aggregate grading, voidage, temperature) and torture test mode, after carrying out expanding test plan, summarize indoor torture test data, set up regression equation.

Ohio Univ goes out to send research fatigue behaviour from the propagation law of crackle.The definition of the fatigue lifetime of application Method of Fracture Mechanics is under certain stress state, and the damage of material, according to crack propagation law, rises to the time that is dangerous and critical conditions from original state.By the comparative analysis to existing PROPAGATION OF FATIGUE CRACK rule test findings, think that the crack propagation rule of P.C.Paris is best suited for the situation of asphalt.

University of California Berkeley and other researchists think and there is a certain particular kind of relationship between total energy consumption in torture test and the repeat function number of times of cyclic load, by experimental study, a kind of tired response model newly is also proposed, i.e. energy consumption fatigue equation, carrys out the fatigue properties of Research on Asphalt Mixture by energy method.SHRP gives the computing method that accumulation dissipation can and be dissipated when can be accumulated to destruction in the standard test method (SHRP-M-009) of compacting asphalt repeated bending fatigue life-span determination.But it is pointed in " asphalt fatigue reaction summary " SHRP-A-312 mono-literary composition as people such as C.L.Monismith: up to now, in repeated bend test, only consider to use that dissipate can be theoretical, still need research further it can be used in other type torture test and bituminous pavement fatigue design.

Domestic research work starting relatively evening, but have also been made a large amount of research work.China's 97 years asphalt pavement design criterion consider the fatigue problem of brea bed, Maoming 60#, triumph 100#, Liaohe River 140# tri-kinds of road asphalts are selected in Ministry of Communications's scientific research project " research of Design Indexes of Asphalt Pavement and parameter ", the bituminous concrete test specimen of grain formula and coarse grain formula two kinds of gratings in preparation, with MTS testing machine in Stress Control mode, under 5 kinds of temperature conditions, (25 DEG C, 15 DEG C, 0 DEG C ,-5 DEG C ,-15 DEG C) carry out indirect tensile fatigue test, apply half-sine wave load, loading frequency is 10Hz.According to test result analysis, the fatigue equation of number of loading when recommending brea bed tension and fatigure failure.

Tongji University's employing Imported Asphalt is prepared three kinds of grating asphalts (AC25, AC20, AC12) and has been carried out the research of Chang Yingli repeated bend test, also according to load quiescent interval, load relieving system and unfavourable season number of days, on-the-spot correction is carried out to indoor Tiredness model, established the Tiredness model of brea bed tension and number of loading.

The four-point bending fatigue test results of the comprehensive domestic and international multiple research project of South China Science & Engineering University, the Tiredness model that to establish with single shaft dynamic compression modulus and pitch saturation degree be Con trolling index.

In sum, research has extensively and profoundly been carried out to fatigue performance of asphalt mixture both at home and abroad.Adopt different fatigue test method to have rated fatigue performance of asphalt mixture, different research institutions also establishes different Tiredness model.But these methods do not consider that High Modulus Asphalt Mixture actual temperature gradient and actual axle load distribution after being paved into road surface, on the impact of High Modulus Asphalt Mixture fatigue lifetime, make calculated value and actual value there is larger difference.

Summary of the invention

In order to the fatigue lifetime on monitor High Modulus Asphalt Mixture road surface more, take into full account bituminous pavement practical service environment and condition, the present invention proposes a kind of High Modulus Asphalt Mixture fatigue life of pavement Forecasting Methodology.High Modulus Asphalt Mixture fatigue life of pavement Forecasting Methodology of the present invention, carries with the distribution of the structure temperature on High Modulus Asphalt Mixture road surface, ground surface material dynamic modulus and temperature axis and is distributed as basic parameter; With indirect tensile fatigue test result matching repeated strain equation in formula, N _ffor number of loading during fatigure failure, α is parameter, ε _xfor horizontal strain, b is parameter; Adopt ANSYS software building Finite Element Model of Pavement Structure, calculate disalignment and carry maximum stretching strain at the bottom of the floor in grade and different temperatures district; According to the Cumulative Fatigue Damage rule of Miner, utilize formula calculate disalignment and carry the Cumulative Fatigue Damage result with the High Modulus Asphalt Mixture of different temperatures, in formula, D is damage factor, K is variable, and L is variable, and N is the calculating fatigue lifetime that respective shaft carries grade, n is that axle carries grade, and i is 1,2,3 ... K, j are 1,2,3 ... L; According to formula calculate α fatigue lifetime on High Modulus Asphalt Mixture road surface, in formula, N is the calculating fatigue lifetime that respective shaft carries grade, and n is that axle carries grade, and i is 1,2,3 ... K; Wherein, described structure temperature refers to the temperature value of annual pavement temperature distribution frequency road surfaces different from each humidity province degree of depth in the different temperatures district obtained according to statistics or actual measurement; Described ground surface material dynamic modulus refers to the dynamic modulus value of the ground surface material being in different temperatures district and the different road surfaces degree of depth; Described temperature axle load distribution refers to that disalignment carries grade, the equivalent axles of different temperatures district within design period.

High Modulus Asphalt Mixture fatigue life of pavement Forecasting Methodology of the present invention, comprises the following steps:

S1, determine pavement structure temperature field, obtain bituminous pavement temperature year distributed data according to statistics, by design temperature interval, bituminous pavement is divided into more than two humidity provinces, calculate the annual pavement temperature distribution frequency in different temperatures district; The change curve of each humidity province temperature with the pavement structure degree of depth is obtained according to actual measurement;

S2, determine ground surface material dynamic modulus, by the Dynamic Modulus of Asphalt Mixture data obtained in be 10Hz and Loaded contact analysis at loading frequency be sinusoidal wave situation, obtain the dynamic modulus distribution of the ground surface material of each different temperatures district and the different pavement degree of depth by least square fitting and linear interpolation;

S3, determine temperature axle load distribution, carry size division axle for vehicle according to highway practical operation situation by axle carry grade and calculate the axle load distribution frequency that disalignment carries grade, according to the accumulation equivalent axles on a track in design period, combining road Temperature Distribution frequency and axle load distribution frequency computation part obtain disalignment and carry grade, the equivalent axles of different temperatures district within design period, i.e. temperature axle load distribution;

S4, determine High Modulus Asphalt Mixture repeated strain equation, under different stress ratio, condition of different temperatures, indirect tensile fatigue test is carried out to selected High Modulus Asphalt Mixture, namely record test specimen by the displacement measurement apparatus of Indirect Tensile Tests instrument and be subject to the distortion Y of the vertical direction produced under effect of stress _t, by formula calculated level distortion X _t, and then according to formula calculate the horizontal repeated strain ε of asphalt _x, according to repeated strain model curve High Modulus Asphalt Mixture repeated strain equation; In formula, Y _tfor test specimen distortion in vertical direction, unit mm; X _tfor test specimen distortion in the horizontal direction, unit mm; μ is Poisson ratio; Δ H is horizontal distortion, and unit is mm; Ω is test specimen diameter, and unit is mm; ε _xfor horizontal strain; π is constant, and α is parameter, and b is parameter, N _ffor number of loading during fatigure failure;

S5, High Modulus Asphalt Mixture fatigue life of pavement are predicted, ANSYS software is adopted to set up pavement typiced structure finite element three-dimensional model, the parameter of input pavement structure temperature field, ground surface material dynamic modulus and axle load distribution, obtains maximum stretching strain at the bottom of the layer based on different load and different temperatures; According to the Cumulative Fatigue Damage rule of Miner, utilize formula calculate disalignment and carry the Cumulative Fatigue Damage result with the High Modulus Asphalt Mixture under condition of different temperatures; Last according to formula calculate α fatigue lifetime on High Modulus Asphalt Mixture road surface; In formula, D is the accumulation of fatigue damage factor, and K is variable, and L is variable, n ₁, n ₂..., n _ifor axle carries grade, N ₁, N ₂..., N _ifor respective shaft carries the calculating fatigue lifetime of grade, i is 1,2,3 ... K, j are 1,2,3 ... L.

The Advantageous Effects of High Modulus Asphalt Mixture fatigue life of pavement Forecasting Methodology of the present invention is the pavement temperature gradient and the axle load distribution that have taken into full account asphalt, and establish forecast model comparatively accurately, the process of accurate description asphalt fatigue decay and rule, there is widely applicable, the reliable advantage of result of calculation, for Asphalt Pavement Structure Design provides more reliable method.

Accompanying drawing explanation

Accompanying drawing 1 is the process schematic of High Modulus Asphalt Mixture fatigue life of pavement Forecasting Methodology of the present invention;

Accompanying drawing 2 is embodiment temperature range distribution histogram;

Accompanying drawing 3 is that embodiment temperature range is with pavement structure depth profile curve map;

Accompanying drawing 4 is that embodiment ground surface material dynamic modulus is with temperature-depth profile curve map;

Accompanying drawing 5 is that embodiment axle carries grade and carries number of times distribution plan with the axle of temperature range;

Accompanying drawing 6 is repeated strain matched curves of common dense bitumen compound AC-25;

Accompanying drawing 7 is asphalt concrete pavement structure schematic diagram;

Accompanying drawing 8 is asphalt concrete pavement structure finite element model figure;

Accompanying drawing 9 is maximum stretching strain curve maps at the bottom of bituminous concrete pavement layer;

Accompanying drawing 10 is asphaltic road-mix surface course Fatigue Life Curve figure;

Accompanying drawing 11 Fatigue Damage of Asphalt Mixture curve map.

Below in conjunction with drawings and the specific embodiments, High Modulus Asphalt Mixture fatigue life of pavement Forecasting Methodology of the present invention is further described.

Embodiment

Accompanying drawing 1 is the process schematic of High Modulus Asphalt Mixture fatigue life of pavement Forecasting Methodology of the present invention, as seen from the figure, High Modulus Asphalt Mixture fatigue life of pavement Forecasting Methodology of the present invention is carried with the distribution of the structure temperature on High Modulus Asphalt Mixture road surface, ground surface material dynamic modulus and temperature axis and is distributed as basic parameter; With indirect tensile fatigue test result matching repeated strain equation in formula, N _ffor number of loading during fatigure failure, a is parameter, ε _xfor horizontal strain, b is parameter; Adopt ANSYS software building Finite Element Model of Pavement Structure, calculate disalignment and carry maximum stretching strain at the bottom of the floor in grade and different temperatures district; According to the Cumulative Fatigue Damage rule of Miner, utilize formula calculate disalignment and carry the Cumulative Fatigue Damage result with the High Modulus Asphalt Mixture of different temperatures, in formula, D is the accumulation of fatigue damage factor, and K is variable, and L is variable, n ₁, n ₂..., n _ifor axle carries grade, N ₁, N ₂..., N _ifor respective shaft carries the calculating fatigue lifetime of grade, i is 1,2,3 ... K, j are 1,2,3 ... L.According to formula calculate α fatigue lifetime on High Modulus Asphalt Mixture road surface, in formula, n ₁, n ₂..., n _ifor axle carries grade, N ₁, N ₂..., N _ifor respective shaft carries the calculating fatigue lifetime of grade, i is 1,2,3 ... K.Wherein, described structure temperature refers to the temperature value of annual pavement temperature distribution frequency road surfaces different from each humidity province degree of depth in the different temperatures district obtained according to statistics or actual measurement; Described ground surface material dynamic modulus refers to the dynamic modulus value of the ground surface material being in different temperatures district and the different road surfaces degree of depth; Described temperature axle load distribution refers to that disalignment carries grade, the equivalent axles of different temperatures district within design period.

Below in conjunction with instantiation, the concrete steps included by High Modulus Asphalt Mixture fatigue life of pavement Forecasting Methodology of the present invention are described:

S1, determine pavement structure temperature field, obtain bituminous pavement temperature year distributed data according to statistics, by design temperature interval, bituminous pavement is divided into more than two humidity provinces, calculate the annual pavement temperature distribution frequency in different temperatures district; The change curve of each humidity province temperature with the pavement structure degree of depth is obtained according to actual measurement.

In this example, according to the annual statistics of section, somewhere, Jiangxi highway, with the temperature interval of 5 DEG C, bituminous pavement is divided into 7 humidity provinces, using the intermediate value of each temperature range as equivalent temperature, namely be divided into 10-15 DEG C, 15-20 DEG C, 20-25 DEG C, 25-30 DEG C, 30-35 DEG C, 7 humidity provinces such as 35-40 DEG C and 40-45 DEG C, and respectively using 12.5 DEG C, 17.5 DEG C, 22.5 DEG C, 27.5 DEG C, 32.5 DEG C, 37.5 DEG C and 42.5 DEG C as equivalent temperature.Then, the annual percent in different temperatures district is obtained, i.e. pavement temperature distribution frequency with each humidity province hour total hour sum (365 × 24) divided by a calendar year of shared time in a calendar year.Take temperature as transverse axis (unit for DEG C), distribution frequency is the longitudinal axis (unit is %) Ji get different temperatures of mapping district annual pavement temperature distribution frequency curve, as shown in Figure 2.

The temperature of asphalt pavement structure also occurs to change along with change in depth.Therefore, the temperature carrying out the general whole asphalt pavement structural layer of replacement by road crust temperature is very inaccurate, therefore, the inventive method adopts actual measurement to obtain the temperature value of different road surfaces, each humidity province degree of depth, namely lay sensor along the bituminous pavement degree of depth, collect, process the temperature value drawing different road surfaces, each humidity province degree of depth with analysis related data.Then, be the longitudinal axis (unit is for mm) apart from the degree of depth on road surface, temperature is that transverse axis (unit be DEG C) is mapped and obtains the change curve of each humidity province temperature with the pavement structure degree of depth, as shown in Figure 3.

S2, determine that ground surface material dynamic modulus distributes, High Modulus Asphalt Mixture selected by ground surface material is tested the Dynamic Modulus of Asphalt Mixture value obtained under loading frequency to be 10Hz and Loaded contact analysis be sinusoidal wave condition, obtains the dynamic modulus value of the ground surface material being in different temperatures district and the different road surfaces degree of depth by least square fitting and linear interpolation.

High Modulus Asphalt Mixture fatigue life of pavement Forecasting Methodology of the present invention is mainly for the High Modulus Asphalt Mixture adding PR-module high-modulus modifier in matrix pitch, adopt PR-module addition to be respectively four kinds of asphalts of 0%, 0.3%, 0.5% and 0.7% as instantiation in the present embodiment, and be designated HMAM-0, HMAM-0.3, HMAM-0.5 and HMAM-0.7 respectively.First, under loading frequency to be 10Hz and Loaded contact analysis be sinusoidal wave condition, test obtains respective dynamic modulus value, the dynamic modulus value of the ground surface material being in different temperatures district and the different road surfaces degree of depth is obtained by least square fitting and linear interpolation with the change curve of the pavement structure degree of depth, as shown in Figure 4 in conjunction with each humidity province temperature.

S3, determine temperature axle load distribution, carry size division axle for vehicle according to highway practical operation situation by axle carry grade and calculate the axle load distribution frequency that disalignment carries grade, according to the accumulation equivalent axles on a track in design period, combining road Temperature Distribution frequency and axle load distribution frequency computation part obtain disalignment and carry grade, the equivalent axles of different temperatures district within design period, i.e. temperature axle load distribution.

The present embodiment is according to the practical operation situation of section, somewhere, Jiangxi highway, 10 axles are divided into by the volume of traffic to carry grade, be respectively 0 ~ 2,2 ~ 4,4 ~ 8,8 ~ 10,10 ~ 12,12 ~ 14,14 ~ 16,16 ~ 18, > 18, unit is T.Its distribution frequency is as shown in table 1.

Table 1 axle load distribution frequency at different levels

The accumulation equivalent axles of this highway within design period on a track is 1.88 × 10 ⁸secondary, integrating step S1 obtains the pavement temperature distribution frequency of 7 humidity provinces and the axle load distribution frequency computation part shown in table 4 and obtains disalignment and carry grade, the equivalent axles of different temperatures district within design period.Carry grade with axle to be transverse axis, to be that the longitudinal axis is mapped and obtained temperature axis and carries distribution plan with equivalent axles, as shown in Figure 5.

S4, determine High Modulus Asphalt Mixture repeated strain equation, under different stress ratio, condition of different temperatures, indirect tensile fatigue test is carried out to selected High Modulus Asphalt Mixture, namely record test specimen by the displacement measurement apparatus of Indirect Tensile Tests instrument and be subject to the distortion Y of the vertical direction produced under effect of stress _t, by formula calculated level distortion X _t, and then according to formula calculate the horizontal repeated strain ε of asphalt _x, according to repeated strain model curve High Modulus Asphalt Mixture repeated strain equation; In formula, Y _tfor test specimen distortion in vertical direction, unit mm; X _tfor test specimen distortion in the horizontal direction, unit mm; μ is Poisson ratio; Δ H is horizontal distortion, and unit is mm; Ω is test specimen diameter, and unit is mm; ε _x-horizontal strain, α is parameter, and b is parameter, N _ffor number of loading during fatigure failure.

In this example, 0.3,0.4 and 0.5 is respectively in stress ratio, temperature carries out indirect tensile fatigue test to HMAM-0, HMAM-0.3, HMAM-0.5 and HMAM-0.7 tetra-kinds of High Modulus Asphalt Mixtures under being respectively 20 DEG C, 25 DEG C and 30 DEG C of conditions, and result is as shown in table 2.

Table 2 High Modulus Asphalt Mixture fatigue test results

In process of the test, record test specimen by the displacement measurement apparatus of Indirect Tensile Tests instrument be subject to the distortion Y of the vertical direction produced under effect of stress _t, the distortion in required horizontal direction can be obtained by vertical deformation according to formula (1),

$X_T=\frac{Y_T\×(0.135+0.5\mathrm{\μ})}{1.794-0.0314\mathrm{\μ}}$ Formula (1)

In formula: Y _t---be test specimen distortion mm in vertical direction;

X _t---test specimen distortion mm in the horizontal direction;

μ-Poisson ratio.

According to the distortion in horizontal direction, obtain the horizontal repeated strain of asphalt according to formula (2),

${\mathrm{\ϵ}}_X=\left(\frac{2\mathrm{\ΔH}}{\mathrm{\Ω}}\right)\×\left[\frac{1+3\mathrm{\μ}}{4+\mathrm{\π\μ}-\mathrm{\π}}\right]$ Formula (2)

In formula: Δ H-horizontal distortion mm;

Ω-test specimen diameter mm;

ε _x-horizontal strain.

For HMAM-0 asphalt, through type (1) and formula (2) calculate the repeated strain of High Modulus Asphalt Mixture of different temperatures, different stress ratio.According to repeated strain model matching, N in formula _frepresent asphalt fatigue lifetime, ε _xrepresent the strain in horizontal direction, the matched curve that use EXCEL obtains as shown in Figure 6.

According to the repeated strain equation that Fig. 6 curve draws, shown in (3).Fitting correlation coefficient R ²=0.885, good relationship.

$N=0.00003{\left(\frac{1}{\mathrm{\ϵ}}\right)}^{2.40}$ Formula (3)

In the repeated strain curve computation process of asphalt, find that four kinds of compound repeated strain equations are roughly similar, its small difference may be due to experimental apparatus and test temperature is non-constant etc. that factor causes.In like manner can obtain, the repeated strain curvilinear equation of HMAM-0.3, HMAM-0.5, HMAM-0.7 is such as formula shown in (4) ~ formula (6).

HMAM-0.3 $N=0.000023{\left(\frac{1}{\mathrm{\ϵ}}\right)}^{2.42}$ Formula (4)

HMAM-0.5 $N=0.000005{\left(\frac{1}{\mathrm{\ϵ}}\right)}^{2.58}$ Formula (5)

HMAM-0.7 $N=0.000002{\left(\frac{1}{\mathrm{\ϵ}}\right)}^{2.67}$ Formula (6)

S5, High Modulus Asphalt Mixture fatigue life of pavement are predicted, ANSYS software is adopted to set up pavement typiced structure finite element three-dimensional model, the parameter of input pavement structure temperature field, ground surface material dynamic modulus and axle load distribution, obtains maximum stretching strain at the bottom of the layer based on different load and different temperatures;

According to the Cumulative Fatigue Damage rule of Miner, utilize formula

$D=\underset{i=1}{\overset{K}{\mathrm{\Σ}}}\underset{j=1}{\overset{L}{\mathrm{\Σ}}}\frac{n_{\mathrm{ij}}}{N_{\mathrm{ij}}}=1$ Formula (7)

Calculate disalignment and carry the Cumulative Fatigue Damage result with the High Modulus Asphalt Mixture under condition of different temperatures; Last according to formula

$\mathrm{\α}(\frac{n_1}{N_1}+\frac{n_2}{N_2}...\frac{n_i}{N_i})\≤1$ Formula (8)

Calculate α fatigue lifetime on High Modulus Asphalt Mixture road surface;

In formula, D is accumulation of fatigue damage, and K is variable, and L is variable, n ₁, n ₂..., n _ifor axle carries grade, N ₁, N ₂..., N _ifor respective shaft carries the calculating fatigue lifetime of grade, i is 1,2,3 ..., K, j be 1,2,3 ..., L.

In this example, the pavement structure of section, somewhere highway adopts upper layer SMA-13, middle surface layer AC-20, cutting optimal HMAM-0 (or HMAM-0.5, HMAM-0.6, HMAM-0.7), as shown in Figure 7.The Finite Element Model of Pavement Structure that ANSYS software is set up is consistent with Fig. 7, and is Elastic Layered System, needs to do following hypothesis simultaneously:

(1) Crack failure face is made up of the point do not contacted, and other each layers are combined by linear elastic materials, and Poisson ratio is μ, elastic modulus is E;

(2) suppose roadbed downwards and level to being do not retrain, wireless extension, and on it, each layer is constrained, direction of traffic is unlimited;

(3) pavement structure acts on vehicular load, effect that is unlimited and horizontal unlimited distance generation is negligible below;

(4) be semi-continuous between surface layer and following layer, and other each layer is totally continuous.

During the present embodiment ANSYS pavement structure three-dimensional modeling, what adopt is the road surface model of 6m × 6m × 6m, for surface layer carry out thickness divide time, employing be every two centimetres be the division methods of one deck, altogether be divided into 8 layers, its ANSYS model sets up result as shown in Figure 8.

Need the modulus inputting each layering when analytical calculation, the impact of temperature road pavement shows in the middle of model by the present invention, makes model can the situation of simulated roadway structure under dynamic actual environment better, refers to as accompanying drawing 3.The value of Poisson ratio is as shown in table 3.

Table 3 Poisson ratio value

Carry grade by axle to load finite element model, through node calculate, obtain four kinds of asphalts and carry maximum stretching strain at the bottom of the floor in grade and different temperatures district based on disalignment, as shown in Figure 9.

Maximum stretching strain at the bottom of the layer of four kinds of asphalts of being derived by ANSYS software, substitutes into the repeated strain equation of formula (7) ~ formula (10), can obtain the fatigue lifetime of four kinds of asphalts, as shown in Figure 10.

According to the Cumulative Fatigue Damage rule of Miner, assuming that the applying order of variety classes load is simple overlaying relation (linear superposition) for the fatigue damage of material, can show that Fatigue Damage Calculation formula (9) is as follows:

$D=\frac{n_1}{N_1}+\frac{n_2}{N_2}...\frac{n_i}{N_i}=\underset{i=1}{\overset{K}{\mathrm{\Σ}}}\frac{n_i}{N_i}$ Formula (9)

In formula: n ₁, n ₂..., n _ifor axle carries grade;

N ₁, N ₂..., N _ifor respective shaft carries the calculating fatigue lifetime of grade;

K is variable.

As can be seen from formula (9), as accumulation of fatigue damage D=1, asphalt just will reach the limit of destruction, thus fatigue breakdown occurs.

It is strong and calculate easy advantage that Cumulative Fatigue Damage rule due to Miner has intuitive, in the middle of the research being widely used in asphalt fatigue properties aspect.Asphalt material is a kind of viscoelastic material, its aspect of performance and residing temperature environment and loading frequency (time) have close contact, the material behavior fatigue behaviour of asphalt simply being regarded as CYCLIC LOADING is inaccurate, need to consider the fatigue behaviour of asphalt under multiple test condition simultaneously, therefore, formula (10) fatigue damage to asphalt is usually adopted to calculate.

$D=\underset{i=1}{\overset{K}{\mathrm{\Σ}}}\underset{j=1}{\overset{L}{\mathrm{\Σ}}}\frac{n_{\mathrm{ij}}}{N_{\mathrm{ij}}}=1$ Formula (10)

In formula: n _iji-th kind of axle that test for jth kind tests condition corresponding carries grade;

N _ijthe calculating fatigue lifetime that i-th kind of axle corresponding to condition carries grade is tested in test for jth kind;

I be i-th kind of axle carry grade to compound repeat load;

J is the test condition of jth kind, comprises the time of test temperature and loading;

K is variable;

L is variable.

Can consider thus axle for vehicle carry with the Fatigue Damage Calculation result of the High Modulus Asphalt Mixture of pavement temperature as shown in figure 11.

According to Miner rule, calculate four kinds of different High Modulus Asphalt Mixture service life of road surface α, computing formula such as formula (11), that is:

$\mathrm{\α}(\frac{n_1}{N_1}+\frac{n_2}{N_2}...\frac{n_{80}}{N_{80}})\≤1$ Formula (11)

In formula (13): represent that disalignment carries the injury tolerance of grade generation under the effect of different temperatures district.

The fatigue lifetime on High Modulus Asphalt Mixture road surface can be obtained thus:

HMAM-0

HMAM-0.3

HMAM-0.5

HMAM-0.7

Can find out that the fatigue lifetime of the HMAM-0 bituminous pavement not adding adjuvant is minimum from the fatigue life prediction result of the bituminous pavement of four kinds of different PR-Module adjuvant additions above, it is 11.52, and the bituminous pavement that with the addition of PR-Module adjuvant is obviously better than HMAM-0 bituminous pavement fatigue lifetime, the fatigue lifetime of HMAM-0.3, HMAM-0.5, HMAM-0.7 reaches 12.75,14.21 and 15.57 years respectively.PR-Module adjuvant has obvious help to the fatigue lifetime of improving bituminous pavement, and along with additive capacity the increase life-span increase more, the pavement life being respectively 0.3%, 0.5% and 0.7% when adjuvant volume adds 10.7%, 23.4%, 35.2% relative to un-added plain asphalt road surface.Therefore, can think that PR-Module adjuvant increases the service life to bituminous pavement and to save maintenance fund helpful.

The foregoing is only preferred embodiment of the present invention, be not limited to the present invention.For a person skilled in the art, the present invention can have change and conversion.All any change, change or equivalent to replace etc. of making within the scope of spiritual principles of the present invention all should be included in protection scope of the present invention.

Claims (2)

1. a High Modulus Asphalt Mixture fatigue life of pavement Forecasting Methodology, is characterized in that, carries be distributed as basic parameter with the distribution of the structure temperature on High Modulus Asphalt Mixture road surface, ground surface material dynamic modulus and temperature axis; With indirect tensile fatigue test result matching repeated strain equation in formula, N _ffor number of loading during fatigure failure, α is parameter, ε _xfor horizontal strain, b is parameter; Adopt ANSYS software building Finite Element Model of Pavement Structure, calculate disalignment and carry maximum stretching strain at the bottom of the floor in grade and different temperatures district; According to the Cumulative Fatigue Damage rule of Miner, utilize formula calculate disalignment and carry the Cumulative Fatigue Damage result with the High Modulus Asphalt Mixture of different temperatures, in formula, D is damage factor, K is variable, and L is variable, and N is the calculating fatigue lifetime that respective shaft carries grade, n is that axle carries grade, and i is 1,2,3 ... K, j are 1,2,3 ... L; According to formula calculate α fatigue lifetime on High Modulus Asphalt Mixture road surface, in formula, N is the calculating fatigue lifetime that respective shaft carries grade, and n is that axle carries grade, and i is 1,2,3 ... K; Wherein, described structure temperature refers to the temperature value of annual pavement temperature distribution frequency road surfaces different from each humidity province degree of depth in the different temperatures district obtained according to statistics or actual measurement; Described ground surface material dynamic modulus refers to the dynamic modulus value of the ground surface material being in different temperatures district and the different road surfaces degree of depth; Described temperature axle load distribution refers to that disalignment carries grade, the equivalent axles of different temperatures district within design period.

2. High Modulus Asphalt Mixture fatigue life of pavement Forecasting Methodology according to claim 1, it is characterized in that, the method comprises the following steps:

S1, determine pavement structure temperature field, obtain bituminous pavement temperature year distributed data according to statistics, by design temperature interval, bituminous pavement is divided into more than two humidity provinces, calculate the annual pavement temperature distribution frequency in different temperatures district; The change curve of each humidity province temperature with the pavement structure degree of depth is obtained according to actual measurement;

S2, determine ground surface material dynamic modulus, by the Dynamic Modulus of Asphalt Mixture data obtained in be 10Hz and Loaded contact analysis at loading frequency be sinusoidal wave situation, obtain the dynamic modulus distribution of the ground surface material of each different temperatures district and the different pavement degree of depth by least square fitting and linear interpolation;

S3, determine temperature axle load distribution, carry size division axle for vehicle according to highway practical operation situation by axle carry grade and calculate the axle load distribution frequency that disalignment carries grade, according to the accumulation equivalent axles on a track in design period, combining road Temperature Distribution frequency and axle load distribution frequency computation part obtain disalignment and carry grade, the equivalent axles of different temperatures district within design period, i.e. temperature axle load distribution;

S4, determine High Modulus Asphalt Mixture repeated strain equation, under different stress ratio, condition of different temperatures, indirect tensile fatigue test is carried out to selected High Modulus Asphalt Mixture, namely record test specimen by the displacement measurement apparatus of Indirect Tensile Tests instrument and be subject to the distortion Y of the vertical direction produced under effect of stress _t, by formula $X_T=\frac{Y_T\×(0.135+0.5\mathrm{\μ})}{1.794-0.0314\mathrm{\μ}}$ Calculated level distortion XT, and then according to formula ${\mathrm{\ϵ}}_X=\left(\frac{2\mathrm{\ΔH}}{\mathrm{\Ω}}\right)\×\left[\frac{1+3\mathrm{\μ}}{4+\mathrm{\π\μ}-\mathrm{\π}}\right]$ Calculate the horizontal repeated strain ε of asphalt _x, according to repeated strain model curve High Modulus Asphalt Mixture repeated strain equation; In formula, Y _tfor test specimen distortion in vertical direction, unit mm; X _tfor test specimen distortion in the horizontal direction, unit mm; μ is Poisson ratio; Δ H is horizontal distortion, and unit is mm; Ω is test specimen diameter, and unit is mm; ε _xfor horizontal strain; π is constant, and α is parameter, and b is parameter, N _ffor number of loading during fatigure failure;

S5, High Modulus Asphalt Mixture fatigue life of pavement are predicted, ANSYS software is adopted to set up pavement typiced structure finite element three-dimensional model, the parameter of input pavement structure temperature field, ground surface material dynamic modulus and axle load distribution, obtains maximum stretching strain at the bottom of the layer based on different load and different temperatures; According to the Cumulative Fatigue Damage rule of Miner, utilize formula calculate disalignment and carry the Cumulative Fatigue Damage result with the High Modulus Asphalt Mixture under condition of different temperatures; Last according to formula calculate α fatigue lifetime on High Modulus Asphalt Mixture road surface; In formula, D is the accumulation of fatigue damage factor, and K is variable, and L is variable, n ₁, n ₂..., n _ifor axle carries grade, N ₁, N ₂..., N _ifor respective shaft carries the calculating fatigue lifetime of grade, i is 1,2,3 ... K, j are 1,2,3 ... L.