Application Research On Huaibei Water-washed Coal Gangue In Road Base

With the rapid development of transportation infrastructure construction industry in China in recent decades,the government has increased investment in road construction and maintenance,which results in the expansible demand for road materials.Owing to the fact that the existing stone resources are very limited,if the waste materials are used,not only the practical value will be completed but also the construction cost can be saved as well as protecting the environment.In this paper,the special water-washed coal gangue in Huaibei area was taken as the research object,and the application of coal gangue in road base has been studied.Firstly,through the application research of coal gangue and its mixture at home and abroad,the feasibility of applying coal gangue in road base was verified.The representative Huaibei washed coal gangue samples were selected on site to conduct raw material performance test research.The results showed that it belonged to the carbon shale washing obsidian and had compact structure,great gradation,and larger crushing value.Its natural water content was much larger than the gravel,the water absorption rate was similar to that of the gravel,and the resistance to disintegration was high,which belonged to non-expansion soil.The content of silicon and aluminum was high.Its mineral and chemical components were mainly quartz,feldspar and SiO₂ and Al₂O₃,and the active components of volcanic ash were higher.There was no sulfur content,the residual coal and organic matter were less,and the durability and volume stability were better.Secondly,combined with the previous research,the material composition design idea was summarized,and the strength mechanism of the mixture was explained from the microscopic perspective.The mixing ratio of 8 groups of materials were prepared,and the cement dosage was 5.5%.The 7d unconfined compressive strength test of cement stabilized macadam-gangue was carried out,and the mechanical performance of 6#,7#and 8#were studied.The results showed that provided that the amount of crushed stone No.1 was26%³0%,the 7-day unconfined compressive strength of the mixture could reach 5.0MPa or more,the maximum value can reach 5.49MPa,and the amount of coal gangue reached35%⁴7%.The proportion of reasonable design materials not only made the mixture strength meet the design requirements,but also improved the utilization rate of coal gangue.Both the strength and rebound modulus of the mixture increased with the growth of the health cycle,the growth rate in the early stage was faster,and the later stage reduced.The performance of8#mixture was relatively superior,and its strength and rebound modulus met the requirements of the base material in the specification,and can be applied in road base.Then,the cement stabilized macadam-gangue was regarded as a composite material composed of gravel,coal gangue,cement mortar and contact interface.The two-dimensional test piece generation program and cohesive force unit embedding program were optimized based on MATLAB,and a mesoscopic model of materials was established in ABAQUS.The rationality of the material parameters was verified by the compressive rebound modulus and the local loading failure test.Finally,the numerical simulations of compression,bending and temperature shrinkage tests were carried out.The simulation results were analyzed from the aspects of macroscopic cracking and system energy.The effects of six factors related to coal gangue characteristics on the temperature shrinkage and crack resistance of the mixture were studied.And a significant comprehensive analysis was conducted.The study showed that increasing the amount of crushed stone No.1 was beneficial to improve the compressive performance of the mixture.Under the appropriate amount of crushed stone,the amount of coal gangue had little effect on the compressive performance of the mixture.The three properties of 8#mixture were better than the other groups.The significance of the impact from the primary to the secondary was:coal gangue-mortar interface fracture parameters>coal gangue content>coal gangue maximum particle size>coal gangue gradation>coal gangue and mortar modulus ratio.Combined with the results of laboratory tests and simulation analysis,it provided some guiding suggestions for the mixture design and engineering application of materials.