CN112014242B - Three-dimensional strain failure criterion-based asphalt pavement load checking method - Google Patents

Three-dimensional strain failure criterion-based asphalt pavement load checking method Download PDF

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CN112014242B
CN112014242B CN202010922908.3A CN202010922908A CN112014242B CN 112014242 B CN112014242 B CN 112014242B CN 202010922908 A CN202010922908 A CN 202010922908A CN 112014242 B CN112014242 B CN 112014242B
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failure criterion
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CN112014242A (en
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黄拓
唐耀
郭攀
曹泽前
黄芯
吕松涛
钱国平
郑健龙
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Changsha University of Science and Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/24—Investigating strength properties of solid materials by application of mechanical stress by applying steady shearing forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
    • G01N3/12—Pressure testing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G01N2203/0017—Tensile
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G01N2203/0019—Compressive
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0025—Shearing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/003—Generation of the force
    • G01N2203/0042—Pneumatic or hydraulic means
    • G01N2203/0044—Pneumatic means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
    • G01N2203/0075—Strain-stress relations or elastic constants
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/025—Geometry of the test
    • G01N2203/0256—Triaxial, i.e. the forces being applied along three normal axes of the specimen
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/026—Specifications of the specimen
    • G01N2203/0262—Shape of the specimen
    • G01N2203/0266—Cylindrical specimens

Abstract

The invention relates to an asphalt pavement load checking method based on a three-dimensional strain failure criterion, which is characterized in that a hollow cylinder mixture test piece is subjected to plane isobaric/axial compression, plane isobaric/axial tension and plane tension/axial tension tests based on an asphalt mixture triaxial test system and an asphalt mixture triaxial test method to obtain an asphalt mixture multiaxial strength test result, converting the established three-dimensional stress failure criterion model into a three-dimensional strain failure criterion model by a generalized hooke's theorem, performing load check on a typical high-grade asphalt pavement under a complex stress state by using the three-dimensional strain failure criterion to accurately predict the specific position of a failure source, the method solves the problem that the existing asphalt pavement design adopts a one-dimensional failure criterion which is not corresponding to the actual stress-strain state, and provides support for designing the asphalt pavement structure according to the complex stress state.

Description

Three-dimensional strain failure criterion-based asphalt pavement load checking method
Technical Field
The application belongs to the field of road engineering and relates to a method for checking the load of an asphalt pavement based on a three-dimensional strain failure criterion.
Background
With the rapid development of economy and the continuous increase of traffic volume in China, the requirement on road performance is higher and higher, and the asphalt pavement is widely applied as a main form of a high-grade highway in China due to good driving comfort, short construction period and convenience in maintenance. However, part of asphalt pavements can not reach the service life and can be damaged in different degrees, and besides the reasons of construction quality, overload and heavy load, unreasonable asphalt mixture design and the like, the unreasonable pavement structure design has important influence. Under the combined action of the above factors, the load response of the road surface under the action of wheel load exceeds the structural resistance, and a series of damages are caused.
At present, the 2017 asphalt pavement design specification in China adopts the maximum tensile strain as a design index of an asphalt layer, and a real pavement structure is in a three-dimensional complex stress state. Therefore, joint failure between factors cannot be considered by adopting the one-dimensional maximum tensile strain failure criterion, and the road surface design misalignment may be caused. Obviously, the resistance of the asphalt pavement is analyzed by adopting a three-dimensional strain failure criterion, which corresponds to the complex stress-strain state of the pavement and is more beneficial to reflecting the essential characteristics of pavement failure; intensity checking and designing are carried out through a three-dimensional strain failure criterion, so that possible failure sources of the asphalt surface layer are judged, and the refinement level of the asphalt pavement design can be improved.
In the previous research, the maximum tensile stress or tensile strain criterion of a simple stress state is mostly adopted for checking the strength of the asphalt mixture and the asphalt pavement; and the method has less check on the road surface strength under a complex stress state. The Chinese patent CN109580360A discloses a method for checking the strength of an asphalt pavement in a simple stress state, which comprises the steps of carrying out fracture strength and fatigue tests on a test piece under different loading rate conditions by using a multifunctional material test system (MTS-Landmark), establishing a fracture fatigue performance prediction model of the asphalt mixture under different loading rate conditions based on a speed-related stress ratio, finding that the problems of strength failure and fatigue failure of the asphalt mixture can be unified by using a speed-related stress ratio idea, deducing a tensile strength structural coefficient of the asphalt pavement, and establishing a new method for checking the fatigue strength of the asphalt pavement considering the influence of the loading rate. The patent CN104749041 discloses a method for checking the strength of an asphalt pavement, which is based on a triaxial test system and a method for an asphalt mixture to perform plane isobaric/axial compression, plane isobaric/axial tension, plane compression/axial compression, plane tension/axial tension and plane non-isostatic/axial compression tests to obtain a multi-axial strength test result of the asphalt mixture, and a novel method for checking the strength of the asphalt pavement according to an asphalt mixture failure criterion in a complex stress state is provided. However, this method only uses stress for checking, does not consider the destructive effect of strain, and does not correspond to the current specification. Patent CN104462843 discloses a high modulus asphalt mixture pavement fatigue life prediction method, which takes the structural temperature distribution, pavement material dynamic modulus and temperature axle load distribution of a high modulus asphalt mixture pavement as basic parameters; fitting a fatigue strain equation according to the indirect tensile fatigue test result, constructing a pavement structure finite element model by adopting ANSYS software, and calculating the maximum tensile strain of the bottom of the layer in different axle load grades and different temperature regions; and according to the fatigue accumulated damage rule of Miner, calculating by using a formula to obtain the fatigue accumulated damage results of the high-modulus asphalt mixture with different axle loads and different temperatures. Patent CN106682255 discloses a cross-scale analysis method for structural design stress response of asphalt pavement, which includes the following steps: establishing a three-dimensional integral macroscopic model of the pavement according to the actual structure and the load parameters to obtain stress response of each layer and cutting boundary displacement; establishing a two-dimensional macroscopic and microscopic scale submodel of the pavement, and analyzing to obtain the stress response of the macroscopic and microscopic scale submodel; and finally, comparing the stress response of the three-dimensional integral macroscopic model with the two-dimensional macroscopic and microscopic scale submodels. Patent CN107764644 discloses an equivalent method for analyzing asphalt pavement structure based on a pavement material stress and strain dependence model, which determines the thickness, poisson ratio and pavement material modulus stress (strain) dependence model of each layer according to the asphalt pavement structure form and material type to be analyzed, adopts the pavement material modulus stress (strain) dependence model to represent the modulus of each layer of the asphalt pavement structure, establishes a calculation analysis system by combining calculation load and interlayer combination conditions, uses the most unfavorable point of each layer of the asphalt pavement structure in terms of stress as an equivalent calculation point, obtains the final modulus of each structure layer by iterative calculation, and calculates the stress, strain and displacement of any point in the asphalt pavement structure according to the elastic layer system theory on the basis.
However, although the above patent is directed to load checking of typical high-grade asphalt pavement structure, it does not systematically perform a triaxial test to use a strain model for strength checking to correspond to the maximum tensile strain failure criterion adopted by the current specifications.
Disclosure of Invention
The invention provides an asphalt pavement load checking method based on a three-dimensional strain failure criterion, which aims to predict the specific position of a failure source and overcome the problem of pavement load checking by adopting a one-dimensional failure criterion in the prior art. The three-dimensional strain failure test method disclosed by the invention has the advantages that the three-dimensional loading equipment which is independently researched and developed is utilized to carry out a three-axis test, and a three-dimensional strain failure criterion is provided through a conversion method. The independently developed air bag triaxial apparatus loading structure is shown in the attached drawing 1, and other triaxial test methods are also suitable for the strength checking calculation of the invention if the three-dimensional stress and axial strain data of the asphalt mixture test piece can be obtained. Then, the strain state of each point position in each structural layer of the asphalt pavement is calculated by utilizing a finite element program, so that the octahedral shear strain gamma' corresponding to each point position is obtainedoct. Finally, determining the octahedral shear-resistant strain capacity and the corresponding shear strain gamma 'based on the three-dimensional strain failure criterion model'octAnd the specific position of the damage source is predicted according to the ratio of the two, so that the refinement level of the asphalt pavement design is improved. The method is based on the information of the damage characteristic points obtained by the triaxial test system of the asphalt mixture, and the three-dimensional strain damage criterion model is established for load check, the method is simple and convenient to calculate, has high precision, is convenient for road practical application, and comprises the following steps:
step 1, carrying out indoor test on an asphalt pavement material, forming an asphalt mixture according to the gradation of the asphalt pavement or carrying out core drilling sampling on the asphalt pavement, and then testing the sample of the asphalt mixture or the core drilling sampling by adopting a triaxial test system so as to obtain the triaxial failure principal stress sigma of the sample under different stress states1，σ2，σ3And vertical strain epsilon1；
2. The principal strain values in the other two directions are calculated by:
Figure BDA0002667335020000031
in the formula, epsilon1、ε2、ε3The strain in the first, second and third principal stress directions respectively, mu is the Poisson's ratio, E is the compression static resilience modulus of the asphalt mixture, and the strain is measured according to the test method of the compression static resilience modulus of the asphalt mixture in road engineering asphalt and asphalt mixture test procedure (JTG E20-2011).
3. Establishing a stress failure criterion model of various asphalt mixtures according to the test result, wherein the stress failure criterion model comprises the following steps:
pressing a meridian:
Figure BDA0002667335020000032
drawing a meridian:
Figure BDA0002667335020000033
breaking the envelope: tau isoct(θ)＝τot-(τot-τoc)sin71.5θ
In the formula, σoctOctahedral normal stress, tau, for bituminous mixturesoctIs the shear stress of octahedron, fcThe uniaxial compressive strength of the asphalt mixture is shown in the specification, theta is the Rode angle and tauot，τocIs tauoctValues when theta is 0 DEG and 60 DEG on the drawing and pressing meridians, K1，a1，b1，c1Are model regression parameters. The specific description of each parameter is as follows:
Figure BDA0002667335020000041
Figure BDA0002667335020000042
Figure BDA0002667335020000043
in the formula, σ1Is the first principal stress, σ2Is the second principal stress, σ3Is the third principal stress.
4. Establishing a relation between failure main stress and failure main strain through a generalized hooke's theorem, and converting the stress failure criterion model into a strain failure criterion model:
Figure BDA0002667335020000044
transformed strain failure criteria model:
pressing a meridian:
Figure BDA0002667335020000045
drawing a meridian:
Figure BDA0002667335020000046
γot，γocis gammaoctValues at roeder angles θ of 0 ° and 60 ° in the tension and compression meridians were substituted into the following formula to calculate shear strain γ 'corresponding to the octahedral shear strength'oct：
γoct′(θ)＝γot-(γot-γoc)sin7 1.5θ
The specific description of each parameter is as follows:
Figure BDA0002667335020000047
Figure BDA0002667335020000048
Figure BDA0002667335020000049
Figure BDA00026673350200000410
in the formula (I), the compound is shown in the specification,
Figure BDA0002667335020000051
equivalent strain value corresponding to the failure stress point in uniaxial compression; epsilonoctIs the positive strain on the strain space octahedron; gamma rayoctShear strain on strain space octahedron; k1，a2，b2，c2Are model regression parameters.
5. And calculating the main stress and the main strain value of each point of the pavement structure layer by adopting finite element software, wherein the standard axle load is a double-wheel single axle of 100KN, the wheel load and the tire pressure of each wheel are respectively 25KN and 0.7MPa, and the equivalent circle radius r of the single wheel track and the center distance between the double wheels are respectively 10.65cm and 3 r. In addition, A, B, C, D, E, F, G, H points are selected in the horizontal direction, 11 points are selected in the vertical direction with the top of the upper layer as the origin, and the point distribution of each structural layer is shown in the attached figure 4.
6. Calculating the shear strain gamma of octahedron at each point positionoctAnd shear strain gamma 'corresponding to octahedral shear strength of material'octOf γ'oct/γ″octThe ratio K is obtained respectively, and the smaller the value of K is, the more dangerous the calculation point is, thereby determining the damage source.
The invention has the technical effects and advantages that:
the invention utilizes the three-way loading equipment which is independently researched and developed to carry out the three-axis test of the asphalt mixture, establishes the octahedron stress failure criterion in the three-dimensional stress state, and then provides the conversion relation between the stress failure criterion and the strain failure criterion. Calculating the shear strength of the octahedron of the material and the corresponding shear strain through the converted three-dimensional strain failure criterion, calculating the octahedron shear strain of each point position in each structural layer of the asphalt pavement by using a finite element program, and taking the ratio K of the failure criterion to the shear strain as a safety coefficient so as to judge a possible failure source of the asphalt surface layer. Therefore, the asphalt pavement load checking method based on the three-dimensional strain failure criterion is provided, the problem that joint failure effect among strain components cannot be considered in the maximum strain failure criterion of the existing asphalt pavement design specification is solved, the method corresponds to the three-dimensional complex stress state of the asphalt pavement structure, and technical support is provided for the fine design of the pavement structure.
Drawings
FIG. 1: the loading structure schematic diagram of the air bag triaxial apparatus;
FIG. 2: a stress schematic diagram of a hollow cylinder test piece;
FIG. 3: an intensity envelope on an isocline surface;
FIG. 4: and (4) a graphic representation of the position of each calculated point of the asphalt pavement structural layer.
Detailed Description
The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.
The road surface is in a three-dimensional complex stress state under the driving load and the natural environment and is damaged by the synergistic effect of three-dimensional stress and strain, and the stress condition of the road surface structure cannot be objectively reflected by the maximum tensile strain theory as the damage criterion in the asphalt road surface design in China. Therefore, the strain failure criterion of the asphalt mixture in a complex stress state needs to be researched through a triaxial test, the shear strain under the three-dimensional stress is calculated to check the strength of the asphalt pavement, and the design level of the asphalt pavement is improved. The method comprises the following specific steps:
step 1, carrying out indoor test on the asphalt pavement material: molding asphalt mixture according to each gradation of the asphalt pavement or sampling drill cores of the asphalt pavement, and then testing the asphalt mixture or the sample sampled by the drill cores by adopting a triaxial test system so as to obtain the triaxial failure principal stress sigma of the sample under different experimental conditions1，σ2，σ3And vertical strain epsilon1；
And 2, calculating main strain values in the other two directions according to the following formula:
Figure BDA0002667335020000061
and 3, establishing a stress failure criterion model of various asphalt mixtures according to the test result, wherein the stress failure criterion model comprises the following steps:
pressing a meridian:
Figure BDA0002667335020000062
drawing a meridian:
Figure BDA0002667335020000063
breaking the envelope: tau isoct(θ)＝τot-(τot-τoc)sin7 1.5θ
And 4, establishing a relation between failure main stress and failure main strain through a generalized hooke's theorem, and converting the stress failure criterion model into a strain failure criterion model:
Figure BDA0002667335020000064
Figure BDA0002667335020000065
Figure BDA0002667335020000066
substituting the above formula into the expression of octahedral stress and octahedral strain can obtain:
Figure BDA0002667335020000071
Figure BDA0002667335020000072
transformed strain failure criteria model:
pressing a meridian:
Figure BDA0002667335020000073
drawing a meridian:
Figure BDA0002667335020000074
in the above formula: the tensile meridian theta is 0 degree, and the press meridian theta is 60 degrees;
Figure BDA0002667335020000075
Figure BDA0002667335020000076
Figure BDA0002667335020000077
calculating the Luode angle of the asphalt mixture sample:
Figure BDA0002667335020000078
γot，γocis gammaoctValues at roeder angles θ of 0 ° and 60 ° in the tension and compression meridians were substituted into the following formula to calculate shear strain γ 'corresponding to the octahedral shear strength'oct：
γoct′(θ)＝γot-(γot-γoc)sin7 1.5θ
Step 5, calculating each main stress and main strain value of each point of the pavement structure layer by adopting finite element software, selecting A, B, C, D, E, F, G, H point positions in total in the horizontal direction, selecting 11 point positions in total in each layer from top to bottom by taking the top of the pavement layer as the original point in the vertical direction, and calculating the octahedral shear strain gamma' of the actual stress of the pavementoct；
Step 6. preparing from gamma'oct/γ″octThe resulting ratio K is used as the safety factor. The smaller the K value is, the calculation point is shownThe more dangerous, and thus the source of possible damage to the asphalt pavement.
The different experimental conditions are respectively plane isobaric/axial compression, plane isobaric/axial stretching, plane compression/axial compression, plane tension/axial stretching and plane unequal compression/axial compression tests. In preferred embodiments, it is preferred to perform the plane iso-pressure/axial tension, plane iso-pressure/axial compression, and plane tension compression/axial tension tests. The three test conditions respectively correspond to the tensile meridian, the pressure meridian and the strength envelope curve on the equal inclination surface, and the stress condition of the plane tensile compression/axial tension test is relatively close to the actual stress condition of the road surface.
The triaxial test system is an asphalt mixture triaxial test system, and the asphalt mixture triaxial test system mainly comprises a material testing machine, an air bag assembly, an air pressure control system and a data acquisition system. The gasbag subassembly includes interior gasbag subassembly and outer gasbag subassembly, and gasbag triaxial apparatus loading structure sees figure 1, specifically includes, loading rod 1, ball twist shape peg 2, and hemisphere pressure (draw) head 3 presses (draw) board 4, outer gasbag clamp plate 5, outer gasbag 6, interior gasbag 7, test piece 8, trachea 9, outer gasbag tray 10.
The working principle of the triaxial test system is as follows: the air pressure control system regulates and controls the inner air bag (6) and the outer air bag (7), air pressure is respectively applied to the inner surface and the outer surface of the hollow cylindrical test piece, then an MTS loading plate applies axial tension/compression load to the test piece, so that complex stress states such as plane isobaric/axial tension, plane isobaric/axial compression, plane tension/axial tension and the like are formed, and three-way unequal stress fields are formed in the test piece. The structure is characterized in that: the outer air bag can completely wrap the outer surface of the test piece, the inner air bag is tightly contacted with the inner surface of the test piece, and the pressing (pulling) plate and the outer air bag pressing plate can prevent the outer air bag from escaping from the gap. The inner airbag, the outer airbag and the loading plate do not interfere with each other, so that the corner effect at the corner of the test piece is avoided.
The experimental conditions of the asphalt mixture triaxial test system are as follows: and (3) placing the aggregate in a constant-temperature oven at 110 ℃ for drying until the weight is constant for later use, and proportioning according to design gradation. Mixing the prepared asphaltThe modified asphalt and aggregate are respectively placed in the oven at 160 ℃ and 180 ℃ for more than 6 hours. Selecting the oil-stone ratio in the range of 4.0-6.0%, forming and manufacturing Marshall test pieces with different oil-stone ratios at intervals of 0.5%, and respectively carrying out Marshall test to determine the optimal oil-stone ratio of the asphalt mixture. Mixing the asphalt mixture by using an indoor stirrer under the condition of the optimal oilstone ratio, forming a test piece by adopting a rotary compaction method, performing end part throwing cutting on the test piece under the action of cooling water to obtain a test piece with the height of 100mm, and then performing core drilling to obtain a hollow cylindrical test piece for testing. And coating lubricating oil on the surface of the test piece, and filling a plastic film antifriction cushion layer to reduce friction, wherein the triaxial test method of the asphalt mixture is to respectively apply air pressure P to the inner cylindrical surface and the outer cylindrical surface of the hollow cylindrical test pieceaAnd PbApplying axial load to the upper and lower surfaces of the test piece to make the inner surface of the test piece in axial stress sigmazRadial stress σrAnd hoop stress sigmaθThe stress state of the test piece is shown in figure 2. r isaIs the inner diameter of a hollow cylinder; r isbIs the outer diameter of a hollow cylinder;
Figure BDA0002667335020000091
wherein r is the distance between the damage observation point of the mixture test piece and the center of the test piece. Sigmaz，σr，σθOrdered by stress magnitude as σ1，σ2，σ3。
The loading mode of the asphalt mixture triaxial test system is that constant air pressure is applied to the surface of a test piece through an air bag, and then an MTS (maximum temperature System) tester is used for applying axial load to the surface of the test piece until the test piece is damaged.
The finite element program is BISAR3.0 software, can calculate a stress-strain field in an elastic layered system, adopts a multilayer elastic continuous system theory under the action of double-circle vertical uniform load to perform mechanical response analysis on a pavement structure, and analyzes stress-strain states of different positions of different layers.
In the invention, the ratio of structural resistance to load response is taken as a safety coefficient K to judge the possible damage source of the asphalt surface layer, and the point position is more dangerous when the K value is smaller.
Due to the adoption of the technical scheme, the invention has the following beneficial technical effects:
a novel method for checking the strength of the asphalt pavement is provided, a three-dimensional strain failure criterion model is used for checking, the synergistic effect among all failure factors is considered, the complex stress strain state of the pavement is corresponded, and the refinement level of pavement design is improved.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
Step 1, forming the asphalt mixtures of AC-13, AC-20 and AC-25 according to a standard test method of road engineering asphalt and asphalt mixture test regulations (JTG E20-2011), wherein the diameter and the height of a selected test piece are all 100 mm. Cylindrical test specimens with a diameter of 100mm and a height of 106mm were formed using a gyratory compactor. Then, the end of the test piece is subjected to end throwing cutting under the action of cooling water to obtain a test sample with the height of 100mm, and then core drilling is carried out to obtain a hollow cylindrical test piece for testing, as shown in fig. 2.
And (3) carrying out plane isobaric/axial compression, plane isobaric/axial tension and plane tension-compression/axial tension failure characteristic tests by adopting three-way loading equipment which is independently researched and developed, and acquiring three-way main stress and vertical strain data of failure characteristic points of the asphalt mixtures of AC-13, AC-20 and AC-25.
Step 2, establishing a stress failure criterion model of the asphalt mixture of AC-13, AC-20 and AC-25, wherein the formula is as follows:
pressing a meridian:
Figure BDA0002667335020000092
drawing a meridian:
Figure BDA0002667335020000101
breaking the envelope: tau isoct(θ)＝τot-(τot-τoc)sin7 1.5θ
Figure BDA0002667335020000102
Establishing a relation between failure main stress and failure main strain through a generalized hooke's theorem, and converting the stress failure criterion model into a strain failure criterion model:
Figure BDA0002667335020000103
substituting the above formula into the expression of octahedral stress and octahedral strain can obtain:
Figure BDA0002667335020000104
Figure BDA0002667335020000105
transformed strain failure criteria model:
pressing a meridian:
Figure BDA0002667335020000106
drawing a meridian:
Figure BDA0002667335020000107
calculating the Luode angle of the asphalt mixture sample:
Figure BDA0002667335020000108
γot，γocis gammaoctValues at roeder angles θ of 0 ° and 60 ° in the tension and compression meridians were substituted into the following formula to calculate shear strain γ 'corresponding to the octahedral shear strength'octThe shape of the envelope of the destruction is shown in FIG. 3.
γoct′(θ)＝γot-(γot-γoc)sin7 1.5θ
TABLE 1 Strength model parameters of various asphalt mixtures in stress and strain spaces
Figure BDA0002667335020000109
And 3, calculating each main stress and main strain value of each point position of the pavement structure layer by adopting finite element software, wherein the standard axle load is a double-wheel single axle of 100KN, the wheel load and the tire pressure of each wheel are respectively 25KN and 0.7MPa, and the equivalent circle radius r of the single wheel track and the center distance of the double wheels are respectively 10.65cm and 3 r. In addition, A, B, C, D, E, F, G, H points are selected in the horizontal direction, 11 points are selected in the vertical direction with the top of the upper layer as the origin, and the point distribution of each structural layer is shown in fig. 4.
Step 4. preparing from gamma'oct/γ″octThe resulting ratio K is used as the safety factor. A smaller value of K indicates that the calculation point is more dangerous, so that a possible damage source of the asphalt surface layer is judged.
TABLE 2 calculation of point-to-point horizontal position distribution for bituminous pavement structure
Figure BDA0002667335020000111
TABLE 3 calculation of point location distribution for each layer
Figure BDA0002667335020000112
Table 4 calculation of main stress value of each structural layer
Figure BDA0002667335020000113
Figure BDA0002667335020000121
Note: sigmaij(i＝1，2，3，4, … … 11; j 1, 2, 3) represents the j-th principal stress corresponding to the i-th layer.
TABLE 5 calculation of principal strain value of point for each structural layer
Figure BDA0002667335020000122
Figure BDA0002667335020000131
Note: epsilonij(i-1, 2, 3, 4, … … 11; j-1, 2, 3) represents the j-th principal strain for the i-th layer.
From the above calculations and fig. 4, the possible hazard points inside the facing are: the point of maximum tensile strain B, which is the position 1/4R from the center of the load of the two wheels at the top of the asphalt pavement, has a main strain value of (0.299 x 10)-3,0.134×10-3,0.012×10-3) (ii) a The central point A of the double-circle uniformly-distributed load wheel gap at the top of the upper layer has a main strain value of (0.093 multiplied by 10)-3，-0.125×10-3，0.011×10-3) (ii) a The single round load outside 1/4R position H point on the top of the upper layer has the main strain value of (0.061 multiplied by 10)-3，-0.125×10-3，0.011×10-3) (ii) a The strain value of the E point position at the single circle load center at the bottom of the middle layer is (0.046 multiplied by 10)-3，0.055×10-3，-0.248×10-3) (ii) a The strain value of the bottom of the middle layer from the position of the F point of the single-circle load center outside 1/4R is (0.033 multiplied by 10)-3，0.048×10-3，-0.214×10-3). Obviously, the real asphalt pavement structure is a typical complex stress-strain state, and the three-dimensional strain failure criterion is adopted for strength checking and designing.
The method is characterized in that the maximum tensile strain failure criterion designed by the Chinese asphalt pavement and the three-dimensional strain failure criterion established by the method are adopted to carry out load check on the asphalt surface course, and the failure source of the obtained asphalt surface course is located at a point B, namely 1/4R from the load center of the double wheels at the top of the asphalt surface course. Under the action of load, the Top surface of the asphalt pavement structure is most prone to Top-down cracks due to the maximum tensile strain, and the Top-down cracks are matched with the typical failure characteristics of the asphalt pavement. Compared with a three-dimensional strain failure criterion, the traditional maximum tensile strain criterion only considers the failure effect of the maximum tensile strain component, but does not consider the joint failure effect between tensile load and compressive load, overestimates the resistance of the material, and is easy to cause early failure. Therefore, the design is carried out by adopting the failure criterion under the complex stress state, and the refinement level of the asphalt pavement design can be improved.
While this summary includes specific embodiments, it will be apparent to those skilled in the art that: various substitutions or changes in form and detail may be made to the embodiments without departing from the spirit and scope of the invention as defined by the claims and their equivalents. The embodiments described herein are to be considered in all respects only as illustrative and not restrictive. The description of features and aspects in each embodiment is believed to apply to similar features and aspects in other embodiments. Therefore, the scope of the invention should be defined not by the detailed description but by the claims, and all changes within the scope of the claims and equivalents thereof should be construed as being included in the technical solution of the present invention.

Claims (6)

1. A three-dimensional strain failure criterion-based asphalt pavement load checking method is based on an asphalt mixture triaxial test system and is characterized by comprising the following specific steps:
(1) the asphalt pavement material was subjected to an indoor test:
molding asphalt mixture according to each gradation of the asphalt pavement or sampling drill cores of the asphalt pavement, and then testing the asphalt mixture or the sample sampled by the drill cores by adopting a triaxial test system so as to obtain the triaxial failure principal stress sigma of the sample under different experimental conditions1，σ2，σ3And vertical strain epsilon1；
(2) The principal strain values in the other two directions are calculated by:
Figure FDA0003194525050000011
mu is Poisson's ratio, E is compression static resilience modulus of the asphalt mixture;
(3) establishing stress failure criterion models of various asphalt mixtures, converting the stress failure criterion models into strain failure criterion models through generalized Hooke's law, and calculating shear strain gamma ' corresponding to the shearing strength of the octahedron of the material 'oct；
The step (3) specifically comprises;
(1.1) to σ1，σ2，σ3The test results of (2) are regressed to calculate the octahedral stress failure criterion on the tensile and compressive meridians as follows:
pressing a meridian:
Figure FDA0003194525050000012
drawing a meridian:
Figure FDA0003194525050000013
breaking the envelope: tau isoct(θ)＝τot-(τot-τoc)sin71.5θ
σoctOctahedral normal stress, tau, for bituminous mixturesoctIs the shear stress of octahedron, fcThe uniaxial compressive strength of the asphalt mixture is shown in the specification, theta is the Rode angle and tauot，τocIs tauoctValues when theta is 0 DEG and 60 DEG on the drawing and pressing meridians, K1，a1，b1，c1Is a model regression parameter;
establishing a relation between failure principal stress and failure principal strain through a generalized Huke theorem, converting a stress failure criterion model into a strain failure criterion model, and calculating the octahedral shear strain gamma 'of the material'oct：
Figure FDA0003194525050000021
Transformed strain failure criteria model:
pressing a meridian:
Figure FDA0003194525050000022
drawing a meridian:
Figure FDA0003194525050000023
Figure FDA0003194525050000024
in the above formula: theta is 0 degree for the tensile meridian, theta is 60 degrees for the pressure meridian, fcIs the uniaxial compressive strength of the asphalt mixture,
Figure FDA0003194525050000025
equivalent strain value corresponding to the failure stress point in uniaxial compression;
Figure FDA0003194525050000026
the strain value corresponding to the failure stress point during uniaxial compression;
Figure FDA0003194525050000027
Figure FDA0003194525050000028
εoctis the positive strain on the strain space octahedron; gamma rayoctShear strain on strain space octahedron; k1，a2，b2，c2Is a model regression parameter;
(1.2) calculating the Luode angle of the asphalt mixture sample:
Figure FDA0003194525050000029
(1.3)γot，γocis gammaoctValues at the radial rod angle θ of 0 ° and 60 ° were obtained, and the shear strain γ 'corresponding to the octahedral shear strength was calculated by substituting the values into the following equation'oct：
γoct′(θ)＝γot-(γot-γoc)sin71.5θ；
(4) Calculating the stress and strain values of each point of the pavement structure layer by using a finite element method, and calculating the octahedral shear strain gamma of the actual stress of the pavementoct；
(5) From gamma'oct/γ″octAnd respectively checking the obtained ratio K as a safety coefficient, wherein the smaller the K value is, the more dangerous the calculation point is, and thus, the possible damage source of the asphalt surface layer is judged.
2. The method for checking the load of the asphalt pavement based on the three-dimensional strain failure criterion according to claim 1, wherein the different experimental conditions in the step (1) are plane isostatic pressing/axial compression, plane isostatic pressing/axial stretching, plane compression/axial compression, plane tension/axial stretching and plane inequality compression/axial compression tests respectively.
3. The method for checking the load of the asphalt pavement based on the three-dimensional strain failure criterion according to claim 2, wherein the different experimental conditions are preferably plane isostatic/axial tension, plane isostatic/axial compression and plane tensile compression/axial tension tests.
4. The three-dimensional strain failure criterion-based asphalt pavement load checking method according to claim 1, wherein the asphalt mixture triaxial test system comprises a material testing machine, an air bag assembly, an air pressure control system and a data acquisition system, and the air bag assembly comprises an inner air bag assembly and an outer air bag assembly.
5. The method for checking the load of the asphalt pavement based on the three-dimensional strain failure criterion according to any one of claims 3 to 4, wherein the experimental conditions of the three-axis test system for the asphalt mixture are as follows:
placing the aggregate in a constant-temperature oven at 110 ℃ to dry the aggregate to constant weight for later use, and proportioning according to design gradation; respectively placing the modified asphalt and the aggregate of the prepared asphalt mixture in drying ovens at 160 ℃ and 180 ℃ for more than 6 hours; selecting the oil-stone ratio within the range of 4.0-6.0%, forming and manufacturing Marshall test pieces with different oil-stone ratios at intervals of 0.5%, and respectively carrying out Marshall test to determine the optimal oil-stone ratio of the asphalt mixture; mixing the asphalt mixture by using an indoor stirrer under the condition of the optimal oilstone ratio, forming a test piece by adopting a rotary compaction method, performing end part throwing cutting on the test piece under the action of cooling water to obtain a test piece with the height of 100mm, and then performing core drilling to obtain a hollow cylindrical test piece for testing; the triaxial test method of the asphalt mixture is a test method which applies air pressure to the inner cylindrical surface and the outer cylindrical surface of a hollow cylindrical test piece respectively and applies axial loads to the upper surface and the lower surface of the test piece so that the inner surface of the test piece is firstly damaged under the combined action of axial stress, radial stress and hoop stress.
6. The method for checking the load of the asphalt pavement based on the three-dimensional strain failure criterion according to claim 5, wherein the loading mode of the three-axis test system for the asphalt mixture is that constant air pressure is applied to the surface of the test piece through an air bag, and then an MTS (maximum temperature stress) tester is used for applying axial load to the surface of the test piece until the test piece is broken.
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