CN-115758718-B - Asphalt mixture-moisture characteristic curve model and parameter calculation method

CN115758718BCN 115758718 BCN115758718 BCN 115758718BCN-115758718-B

Abstract

A method for calculating the characteristics curve model and parameters of asphalt mixture includes such steps as preparing core sample of asphalt mixture, measuring initial dry quality and porosity of core sample by vacuum water saturation method, checking parallelism of parallel core sample, measuring the matrix suction force psi m of core sample, measuring the data pair of water saturation S, substituting the matrix suction force psi m and water saturation S to the initial model of asphalt mixture-water characteristics curve, fitting to obtain the characteristics curve, introducing the determined effective parameters to initial model, deriving by effective model, calculating the slope of zero matrix suction point, and calculating residual matrix suction parameters. The mathematical model of the asphalt mixture-water characteristic curve provided by the invention is continuously and monotonically decreased in the range from zero to infinity of the matrix suction force, so that the unsaturated parameters can be conveniently calculated.

Inventors

XU HUINING
Bian Xinxing
JI WEIDONG
LI HENGZHEN
Wei Binhao

Assignees

哈尔滨工业大学

Dates

Publication Date: 20260512
Application Date: 20221115

Claims (10)

1. The asphalt mixture-moisture characteristic curve model and the parameter calculation method are characterized in that the asphalt mixture-moisture characteristic curve model and the parameter calculation method are realized according to the following steps: Firstly, forming a plurality of standard Marshall parallel samples of asphalt mixture by adopting a Marshall method, and obtaining core samples of the asphalt mixture by adopting a coring machine; Measuring initial drying mass m 0 and porosity V v of the asphalt mixture core sample in the first step by adopting a vacuum water saturation method, and checking parallelism of parallel core samples; Step three, using an unsaturated static triaxial test system to measure a series of actual measurement data pairs of matrix suction force psi m and corresponding water saturation S of an asphalt mixture parallel core sample, wherein the specific process of the test is as follows: Step 3a, immersing the asphalt mixture core sample in a normal-temperature degassing water tank, placing the water tank in a vacuum dryer, setting the vacuum degree to 97.3-98.7 kPa, immersing in water at normal pressure, and repeating for a plurality of times to obtain a saturated asphalt mixture core sample; Step 3b, performing a dehumidification experiment of gradually applying matrix suction to the saturated asphalt mixture core sample until the relative displacement is less than 5% under continuous 5-level suction, taking out the core sample, weighing the mass of the residual water content state, and calculating the residual water content volume according to a formula (1); (1) In the formula (1), V r is the residual water content of the asphalt mixture core sample, m r is the mass of the asphalt mixture core sample in the residual water content state, m 0 is the mass of the asphalt mixture core sample in the initial dry state, and ρ w is the density of the deaerated water; the water content volume value of each level of balance state is obtained through the back calculation of the drainage volume in sequence, and the calculation formula of the water content volume value of each level of balance state is as follows: (2) In the formula (2), V i is the water content volume of the asphalt mixture core sample in the ith level of balance state, d i is the total water drainage volume of the asphalt mixture core sample in the ith level of balance state, and d r is the total water drainage volume of the asphalt mixture core sample in the residual water content state; The saturation of each level of balance state is calculated according to the formula (3): (3) S i is the saturation of the asphalt mixture core sample in the ith level balance state in the formula (3); thus obtaining a plurality of groups of matrix suction-saturation discrete data points, drawing an asphalt mixture-moisture characteristic curve, wherein the abscissa of the curve is matrix suction psi m , and the ordinate is core sample moisture saturation S; Step 3c, sequentially repeating the step 3a and the step 3b, and testing asphalt mixture-moisture characteristic curves of a plurality of parallel core samples; Substituting a series of experimental data of the matrix suction force psi m and the water saturation S obtained in the step three into an initial model of an asphalt mixture-water characteristic curve, and fitting to obtain the asphalt mixture-water characteristic curve; wherein the asphalt mixture-moisture characteristic curve initial model has the following form: (4) in the formula (4), S is the water saturation of the asphalt mixture, S r is the residual water saturation of the asphalt mixture, ψ m is the matrix suction of the water asphalt mixture, a and b are fitting parameters of a model, and e is the base number of natural logarithm; Fifthly, setting a fitting goodness constraint condition, calculating fitting precision, judging whether the fitting precision meets the requirement, and if the fitting precision meets the fitting goodness constraint condition, obtaining fitting parameters a and b and residual water saturation S r of the asphalt mixture based on an initial model of the asphalt mixture-water characteristic curve; Step six, fitting a, b parameter values and residual water saturation S r values obtained by a plurality of parallel core samples in the step five, and respectively obtaining average values to obtain effective parameters a * 、b * and S r * of the asphalt mixture-water characteristic curve model; step seven, bringing the model effective parameters a * 、b * and S r * obtained in the step six into the asphalt mixture-moisture characteristic curve initial model obtained in the step four to obtain an asphalt mixture-moisture characteristic curve effective model; Step eight, deriving an effective model of the asphalt mixture-water characteristic curve in the step seven, and calculating to obtain a derivative parameter specific water capacity curve of the asphalt mixture-water characteristic curve; the specific water capacity curve model equation is as follows: (14) Step nine, acquiring a slope k 0 of an asphalt mixture-moisture characteristic curve at a position where matrix suction force phi m =0 kPa, namely substituting an effective parameter a * 、b * of an asphalt mixture-moisture characteristic curve model obtained in the step six and residual water saturation S r * of the asphalt mixture into a zero-water-absorption-ratio capacity formula; at the full saturation point, i.e. s=1, the specific water capacity value is calculated, yielding the zero absorption specific water capacity as follows: (15) step ten, substituting the slope k 0 of the zero matrix suction point into a calculation formula of residual matrix suction (16) In the process, a residual matrix suction parameter psi r of the asphalt mixture is obtained.
2. The asphalt mixture-moisture characteristic curve model and parameter calculation method according to claim 1, wherein the dimensions of the step one cylindrical core sample are phi 50mm x 63.5mm.
3. The asphalt mixture-moisture characteristic curve model and the parameter calculation method according to claim 1, wherein in the second step, the difference between the measured value of the porosity of the parallel core sample and the average value is less than 1.3 to 1.4 times of the standard deviation, and the parallelism meets the requirement.
4. The asphalt mixture-moisture characteristic curve model and parameter calculation method according to claim 1, wherein the water tank in step 3a is placed in a vacuum dryer for 15min.
5. The asphalt mixture-moisture characteristic curve model and parameter calculation method according to claim 1, wherein the immersion treatment time in the normal pressure state in step 3a is 0.5h.
6. The asphalt mixture-moisture characteristic model and parameter calculation method according to claim 1, wherein the matrix suction force application in step 3b is not less than 10 stages.
7. The asphalt mixture-moisture characteristic curve model and the parameter calculation method according to claim 1, wherein the dehumidifying experiment in step 3b adopts an unsaturated static triaxial test system, the pore water pressure is controlled to be 0kPa during the process of applying the matrix suction force, the pore gas pressure is applied step by step respectively, and the value of the applied matrix suction force ψ m is equal to the pore gas pressure.
8. The asphalt mixture-moisture characteristic curve model and parameter calculation method according to claim 1, wherein the asphalt mixture-moisture characteristic curve model in the fourth step is established by: Step 4a, calculating quasi-residual water saturation of the asphalt mixture through a formula (5); (5) Ŝ r is quasi-residual water saturation of the asphalt mixture, n is total number of stages of matrix suction force application, and S i is saturation of the asphalt mixture core sample in the ith stage balance state; step 4b, normalizing a series of saturation data of the actually measured asphalt mixture, and converting the data to obtain the quasi-effective saturation Ŝ e of the asphalt mixture; (6) Step 4c, obtaining a data pair and a scatter diagram of the quasi-effective saturation of the asphalt mixture and the matrix suction, and fitting by adopting a configuration of a McKee & Bumb equation according to the correlation between the data pair and the scatter diagram to obtain a McKee & Bumb model and parameters thereof; the configuration of the McKee & Bumb equation is as follows: (7) In the formula (7), y is an explained variable of the equation, x is an explained variable of the equation, and alpha and beta are equation parameters; Step 4d, bringing the initial matrix suction force psi m =ψ 0 =0 into the McKee & Bumb model in step 4c, and calculating an initial effective saturation predicted value S ec0 ; step 4e, calculating a compensation term epsilon 0 between the initial effective saturation predicted value S ec0 and the initial effective saturation actual value S e0 =1 of the asphalt mixture-moisture characteristic curve according to the formula (8): (8) step 4f, introducing the compensation term epsilon 0 calculated in the step 4e into the denominator term of the McKee & Bumb model to obtain an initial model equation: (9) step 4g, parameters a and b are introduced, and the McKee & Bumb model equation is simplified: (10) (11) Step 4h, taking S e = (S-S r )/(1-S r ), and bringing formulas (10) and (11) into an initial model equation (9), and converting into a display format in the form of S=f (ψ m ), thereby obtaining an asphalt mixture-moisture characteristic curve model 。
9. The asphalt mixture-moisture characteristic curve model and parameter calculation method according to claim 1, wherein the asphalt mixture-moisture characteristic curve is fitted by using matlab or 1st opt program in the fourth step.
10. The asphalt mixture-water characteristic curve model and parameter calculation method according to claim 1, wherein in the fifth step, a fitting goodness constraint condition is set, fitting accuracy is calculated, whether the fitting accuracy meets the requirement is judged, and if the fitting accuracy meets the fitting goodness constraint condition, a fitting accuracy calculation formula is: (13) In the formula (13), adj R 2 is a coefficient for adjusting and determining, which reflects the fitting result, n is the total amount of data to samples, y i is the ith measured data value of the suction force of the asphalt mixture matrix, ŷ i is the ith predicted value of the suction force of the asphalt mixture matrix, ӯ is the arithmetic average value of the measured data of the suction force of the asphalt mixture matrix, and k is the number of parameters of the asphalt mixture-moisture characteristic curve model.

Description

Asphalt mixture-moisture characteristic curve model and parameter calculation method Technical Field The invention belongs to the technical field of unsaturated hydraulic characteristic research of asphalt pavement materials, and particularly relates to an asphalt mixture-water characteristic curve model and a parameter calculation method. Background Asphalt pavement is an artificial structure paved in natural environment, and is frequently subjected to the effects of atmospheric precipitation, capillary water replenishing, evaporation effect and other water circulation. This effect also tends to result in the ubiquitous liquid, gas two-phase and unsaturated percolation in the pore structure of the asphalt mixture. Many scientific researches and engineering practices show that long-term unsaturated occurrence and flow of moisture weakens the strength of an asphalt-aggregate interface, crack expansion is induced after external conditions such as vehicle load are added, the moisture damage of an asphalt pavement, water-heat-force coupling damage and the like are aggravated, and finally the service life and economical efficiency of the asphalt pavement are reduced. The key to solving the problems is to define the unsaturated hydraulic characteristics of the asphalt pavement material. The characteristic curve of asphalt mixture-moisture is a constitutive relation which is important in describing unsaturated hydraulic characteristics of asphalt pavement materials and reflects the change rule of potential energy of a material matrix along with humidity state. As a key parameter of the unsaturated seepage control equation, an asphalt mixture-moisture characteristic curve is often used for theoretical and simulation calculation of the hydrodynamic behavior of an unsaturated asphalt pavement. More and more research conclusions show that the research on unsaturated water holding property, permeability property, stress property, strength and deformation property and the mutual coupling problem of the asphalt pavement material can be guided by means of the asphalt mixture-water characteristic curve. At present, in terms of an asphalt mixture-moisture characteristic curve model, a great deal of researches assume that the pore characteristics of a porous medium are similar on a macroscopic scale, and an unsaturated soil-moisture characteristic curve model or a matrix suction force is adopted to replace the asphalt mixture-moisture characteristic curve model according to a saturation reduction model, so that the seepage response and the dynamic response of an unsaturated asphalt pavement are calculated. However, the analysis results thus obtained often do not accurately reflect the actual condition of the unsaturated asphalt pavement. This shows that the existing approximation model is still not very applicable to asphalt mixtures, and the model for describing the asphalt mixture-moisture characteristic curve is relatively lacking. Therefore, it is necessary to provide a model and a parameter calculation method reflecting the characteristics of the asphalt mixture-moisture characteristic curve. Disclosure of Invention Aiming at the problem that a model for describing an asphalt mixture-water characteristic curve is lack in the prior art, the invention provides the asphalt mixture-water characteristic curve model which is globally continuous and has good describing effect according to the monotone decreasing distribution characteristic of the actual measurement result of the asphalt mixture-water characteristic curve and the specific water capacity curve, and a calculation method of each parameter of the model is provided on the basis, so that an important constitutive relation is constructed for the unsaturated hydraulic characteristic of an asphalt pavement material, and the estimation precision of the service performance of the unsaturated state of the asphalt pavement is improved. The asphalt mixture-moisture characteristic curve model and the parameter calculation method are realized according to the following steps: Firstly, forming a plurality of standard Marshall parallel samples of asphalt mixture by adopting a Marshall method, and obtaining core samples of the asphalt mixture by adopting a coring machine; Measuring initial drying mass m 0 and porosity V v of the asphalt mixture core sample in the first step by adopting a vacuum water saturation method, and checking parallelism of parallel core samples; Step three, using an unsaturated static triaxial test system (an unsaturated pressure chamber system) to measure a series of actual measurement data pairs of matrix suction force psi m and corresponding water saturation S of the asphalt mixture parallel core sample, wherein the specific process of the test is as follows: Step 3a, immersing the asphalt mixture core sample in a normal-temperature degassing water tank, placing the water tank in a vacuum dryer, setting the vacuum degree to 97.3-98.7 kPa, immersing in w