Study On Mechanical Simulation And Mesoscopic Failure Mechanism Of Cement Stabilized Recycled Aggregate Based On The DEM

The use of recycled aggregates for road base and subbase construction can not only solve the problem of shortage of natural sand and gravel,but also consume a large amount of construction waste,meeting the strategy of sustainable development and the construction of ecological civilization.However,the source of recycled aggregates is complex,and the performance of recycled aggregates is highly variable from the same source,so laboratory tests with limited samples cannot represent the various recycled aggregates.The incorporation of recycled aggregates also increases the weak interface transition zones of the mixture,which can change the destruction mechanism of recycled aggregate mixture from the mesoscopic and microcosmic scale.Discrete element method can be used to characterize different sources of recycled aggregates by changing the types and parameters of contact model between different material particle model,and study the effect of recycled aggregates properties on the macro-mechanical properties of the mixture on the microscopic scale,so it is very suitable for researching the study of cement stabilized recycled aggregate.Therefore,the study is based on the discrete element method to establish a two-dimensional discrete element model of cement stabilized recycled aggregate,and explore the influence of the weak interface transition zones of recycled aggregate on the indirect tensile strength and failure mechanism of cement stabilized recycled aggregate.First,the study proposes a binary discrete element model of recycled aggregates based on the characteristics and failure modes of recycled aggregates,which is divided into non-breakable stone parts and breakable weak areas: the outline of the stone is randomly generated based on the Voronoi diagram,and the unbreakable stone is filled with the clump by the Bubble Pack algorithm,and the breakable weak area is generated through the self-compiled FISH language program.Then,according to the five particles of new stone,old stone,new cement mortar,old cement mortar and brick particles existing in the recycled aggregate mixture model,it is determined that there are 15 types of main contacts inside the model.The linear contacts and the linear parallel bonding model are selected to represent various types of contact according to the contact characteristics.The study propose a “step-by-step calibration method” to determine the microscopic parameters of the contact model.The results are verified by laboratory experiments.The results show that the deviation of each step is less than 2%,and the deviation under different recycled coarse aggregate content Less than 10%,which verifies the feasibility of the discrete element method.Finally,the single-factor analysis and orthogonal experiments were carried out on the developed discrete element test model,and the influence of weak interface transition zones on the indirect tensile strength of cement stabilized recycled aggregates was analyzed.The failure mechanism analysis were carried out based on the crack development comparison of natural aggregate mixture and recycled coarse aggregate mixture,and the failure mechanism analysis shows that the weak area has a two-sided effect on the strength of the mixture.