CN-121558508-B - Cement stabilized macadam mechanical property analysis method based on maximum aggregate nominal particle size

CN121558508BCN 121558508 BCN121558508 BCN 121558508BCN-121558508-B

Abstract

The invention discloses a method for analyzing mechanical properties of cement stabilized macadam based on maximum aggregate nominal particle size, and relates to the technical field of analysis of mechanical properties of cement stabilized macadam; the method comprises the steps of carrying out a macroscopic mechanical test to obtain a stress-strain curve and a crushing value, establishing a three-dimensional discrete element numerical model of a corresponding test piece, carrying out uniaxial compression simulation, verifying through the model to ensure the reliability, and quantitatively analyzing the distribution of contact force, the characteristics of contact quantity and the evolution rule of microcracks from a microscopic level based on the verified model. According to the analysis method, a mechanism that the nominal maximum particle size improves the macroscopic performance of the material by regulating and controlling an internal force chain network and inhibiting damage accumulation is revealed through macro-micro combination means, and a scientific micro-mechanical basis and a quantitative analysis tool are provided for grading optimization and high-performance design of a cement stabilized macadam base.

Inventors

DENG CHANGQING
ZHANG YU
XIANG ZE
YANG QIZHU
YANG LINGMING
GUAN ZUBAO
ZOU HONG

Assignees

邵阳学院

Dates

Publication Date: 20260512
Application Date: 20260126

Claims (7)

1. The method for analyzing the mechanical properties of the cement stabilized macadam based on the maximum aggregate nominal particle size is characterized by comprising the following steps of: Step S1, preparing a test piece and testing macroscopic mechanics, namely preparing at least two framework compact type cement stabilized macadam test pieces with different nominal maximum grain diameters, carrying out a uniaxial compression test on the test piece, obtaining a macroscopic stress-strain curve, and carrying out a crushing value test; Step S2, constructing and verifying a discrete element numerical model, namely constructing a corresponding three-dimensional discrete element single-axis compression numerical model based on grading information of each test piece in the step S1, operating the numerical model for simulation, comparing a stress-strain curve obtained by simulation with a test curve of the corresponding test piece in the step S1, and verifying the reliability of the model; s3, analyzing macroscopic mechanical properties, namely extracting and quantifying macroscopic features reflecting mechanical essence based on the verified model; S4, extracting and analyzing the micro-mechanical characteristics of the model in the loading process, wherein the micro-mechanical characteristics comprise contact force distribution characteristics, contact quantity characteristics and microcrack evolution characteristics; in the step S4, analyzing the micro-crack evolution characteristics comprises monitoring and recording the development curve of the number of micro-cracks along with axial strain in the loading process, extracting crack initiation strain threshold, crack expansion rate and total number of cracks in macroscopic damage, and extracting crack space distribution and angle distribution characteristics at peak stress moment; Counting the projection angles of normal vectors of all micro-cracks on a horizontal plane, and drawing a crack counting rose diagram to analyze the directional initiation and expansion rules of the cracks; In the step S4, a crack evolution three-stage prediction model is constructed to predict the crack resistance, and the following prediction parameters are set in association with the microscopic structural parameters and macroscopic damage behaviors: (1) Threshold strain for initiation of injury I.e. strain point at which crack starts to grow significantly: ; Wherein, the For the equivalent interface strengthening coefficient, The larger the interface the stronger the crack resistance, Representing the entropy of a framework structure, wherein A is a coefficient, and epsilon 0 is a reference strain; (2) Stable rate of growth of lesions The method comprises the following steps: G d = B/λ + G 0 ; Wherein λ is the degree of tortuosity of the force chain, so G d is inversely proportional to λ, B is the coefficient, G 0 is the background growth rate; (3) Total microcrack number at final failure : N total = N max × C L (-k) ; Wherein, the For the load transfer concentration, N max is the theoretical microcrack maximum and k is the decay index.
2. The method according to claim 1, wherein in the step S1, the different nominal maximum particle sizes include at least a first particle size, a second particle size, and a third particle size, the third particle size being larger than the second particle size, and the second particle size being larger than the first particle size.
3. The method for analyzing mechanical properties of cement stabilized macadam based on the maximum aggregate nominal particle size according to claim 1, wherein in the step S2, constructing a three-dimensional discrete element uniaxial compression numerical model specifically comprises: S2-1, particle generation and initial balance, namely generating a discrete particle aggregate in a cylindrical modeling domain according to the number of particles calculated by actual grading, defining density and damping parameters of the particles, setting a loading plate and a lateral constraint boundary, and performing initial balance calculation; S2-2, coarse aggregate clustering modeling, namely replacing coarse aggregate particles with the particle size larger than a preset threshold value with a cluster structure formed by bonding a plurality of basic particles so as to simulate the real form of irregular aggregates; and S2-3, assigning a contact model, namely assigning a mechanical model for contact among different components.
4. The method for analyzing the mechanical properties of cement stabilized macadam based on the maximum aggregate nominal particle size according to claim 3, wherein the coarse aggregate clustering modeling is to define the shape of a cluster structure by importing a geometric file in an STL format and control the volume error before and after cluster replacement to be within +/-1%.
5. The method for analyzing the mechanical properties of the cement stabilized macadam based on the nominal particle size of the maximum aggregate according to claim 3, wherein a mechanical model is given to the contact between different components, a rolling resistance linear contact model is adopted for the contact between the coarse aggregate and the loading plate and between the coarse aggregates, and a parallel bonding model is adopted for the contact between cement mortar particles for simulating an aggregate matrix.
6. The method for analyzing the mechanical properties of cement stabilized macadam based on the nominal particle size of the maximum aggregate according to claim 1, wherein in the step S4, the analysis of the contact force distribution characteristics comprises the steps of counting the average contact force and the maximum contact force born by the aggregate particles in different particle size ranges, and analyzing the transmission level and the dominant skeleton of the load in the material.
7. The method for analyzing the mechanical properties of the cement stabilized macadam based on the maximum aggregate nominal particle size according to claim 1, wherein in the step S4, the analysis of the contact number features comprises the steps of defining strong contact higher than average contact force and weak contact lower than average contact force, and counting the number and proportion of the strong contact and the weak contact born by the aggregate particles in each particle size interval so as to quantify the mechanical roles of the particles with different particle sizes in a framework structure.

Description

Cement stabilized macadam mechanical property analysis method based on maximum aggregate nominal particle size Technical Field The invention relates to the technical field of analysis of mechanical properties of cement stabilized macadam, in particular to a method for analyzing the mechanical properties of cement stabilized macadam based on the nominal particle size of maximum aggregate. Background Cement Stabilized Macadam (CSM) is widely used in high grade highway and heavy load pavement construction due to its excellent mechanical properties and cost effectiveness. However, under the coupling action of long-term cyclic load and environmental factors, the problems of mechanical property degradation, reflection cracking, fatigue damage and the like still restrict the service life of the pavement. With the rapid development of traffic infrastructure and the increasing traffic load, the requirements for improving the performance of pavement materials are urgent, and the deep exploration of the mechanical behavior of CSM and the influencing factors thereof is very important. Among the many influencing factors, aggregate grading is a key factor in determining the mechanical properties of CSM. The prior researches have been widely explored in the aspects of grading type, design method, evaluation index, grading development aiming at different materials and the like. In the aspect of grading type, research shows that the skeleton compact structure can effectively form a stable skeleton, and the mechanical property and the crack resistance of the material are obviously improved. For example, tian found that the strong embedded extrusion backbone grading consisting of three types of coarse aggregates, 19-31.5 mm, 9.5-19 mm and 4.75-9.5 mm, at a mass ratio of 5:3:2 significantly improved the shrinkage deformation resistance of the material. The Ji research shows that the compact grading of the embedded and extruded framework can be realized by controlling the passing rate of key sieve pores, and the mechanical property and the crack resistance can be improved at the same time. Kong designs the dense grading of the embedded skeleton by using a discrete element method, and proves that the regenerated brick-concrete aggregate can also form an effective force chain transmission system. In the grading design method, liu adopts a uniform interpolation system to analyze five performance change rules of the grading type from coarse to fine, and the maximum dry density and the grading are found to be in a quadratic curve relationship. Kong gradually designs the optimal embedded skeleton compact grading based on a discrete element method. In the aspect of an evaluation system, li creatively provides microscopic evaluation indexes such as skeleton compactness, skeleton stability and the like, and verifies the strong correlation between the skeleton compactness, the skeleton stability and the like and macroscopic mechanical strength. Liang then uses CT scanning techniques to reveal the distribution characteristics of the different level internal voids. In the aspect of grading development of different materials, the research covers a plurality of special materials. For example, zeng's study on coral aggregate found that it only formed a strong suspended dense structure without establishing an effective framework, and determined that the maximum particle size was 53mm and the fine aggregate content was 45% of the optimum grading. Khamseh discusses the stabilization treatment of the iron tailings, and the cement doping amount of 5% -10% is found to be capable of remarkably improving the mechanical properties of the iron tailings. Li also compares the differences in the properties of the different drainage base gradations, compact and framework-void. In addition, it has been found that 4.75 mm is often used as a demarcation point for coarse and fine aggregates, while vibratory compaction is more capable of ensuring the realization of grading designs than hydrostatic compaction. Despite significant advances in CSM grading design research, current work has focused mainly on grading type and mix design methodology. The study of nominal maximum particle size (NMAS) as an independent key variable to elucidate its specific impact on CSM performance has remained blank, which hampers the fundamental understanding of framework structure formation and mechanism of action. Disclosure of Invention The invention provides a method for analyzing the mechanical properties of cement stabilized macadam based on the maximum aggregate nominal particle size, which reveals the mechanism that the nominal maximum particle size improves the macroscopic performance of materials by regulating and controlling an internal force chain network and inhibiting damage accumulation through macro-micro combination means, and provides scientific micro-mechanical basis and quantitative analysis tools for grading optimization and high-performance design of a cement st