Investigation On Performance Of Cement-Stabilized Filled Large Aggregates Base Materials In Alpine And High Altitude Regions

Semi-rigid base materials are widely used in road structures due to their high strength and stiffness.However,the cracking problem of semi-rigid base materials affects the performance of roads,and the cracking problem is more serious in alpine and high altitude regions.In this paper,cement-stabilized filled large aggregates base material was used.The skeleton structure is formed by the interlocking of large aggregates.cement-stabilized filled fine aggregates is used to fill the gap to support and reinforce the skeleton,reduce the material plate and cement dose,and improve the cracking-resisting performance of the base material.First,the mix ratio of cement-stabilized filled large aggregates base material was determined to be 0～4.75 mm: 4.75～9.5 mm: 37.5 mm = 0.21: 0.28: 0.51 by the main skeleton void volume filling method.The unconfined compressive strength,compressive rebound modulus,flexural strength,drying shrinkage and temperature shrinkage of the materials were tested by forming cylindrical specimens and beam specimens.With the help of ABAQUS finite element software,a numerical model of cement-stabilized filled large aggregates base material was constructed to simulate local compression and compressive resilient modulus tests.The correctness and rationality of the model parameters were verified by comparing with the corresponding indoor test results.The local loading test and temperature shrinkage performance test were carried out by numerical simulation.The cracking-resisting performance of cementstabilized filled large aggregates base material was evaluated by macroscopic crack propagation morphology and system strain energy.Sensitivity analysis was carried out on the influence of size of large aggregates,content,stiffness ratio and interface parameters of large aggregates on crack resistance.Finally,the numerical model of the pavement was constructed,and the fatigue life of the pavement under the action of temperature load alone,vehicle load alone and the coupling of the two was compared and analyzed.The influence of surface layer thickness,base modulus and heavy load conditions on the fatigue life of the pavement was studied,and the effect of improving the fatigue life of the pavement when cement-stabilized filled large aggregates was applied to the base was summarized.The results show that: 1)The mechanical properties of cement-stabilized filled large aggregates base material are weaker than those of the conventional water-stabilized gravel material,but its shrinkage deformation is smaller,and it is not easy to crack due to excessive shrinkage.2)The order of the influence on the anti-cracking performance of cement-stabilized filled large aggregates base material is : the bond strength between the large aggregates and the cement-stabilized filled fine aggregates > size of the large aggregates > content of the large aggregates > the fracture energy > the stiffness ratio.3)The system energy of the numerical model of cement-stabilized filled large aggregates base material is lower than that of conventional cement-stabilized aggregates base material.The former can absorb stress,slow down the cracking trend and enhance cracking-resisting performance.4)Increasing the thickness of the surface layer,reducing the modulus of the base layer and limiting the heavy load traffic can increase the number of load cycles.The fatigue life under the temperature load alone is 27649 times,while the fatigue life under the coupling effect is 26116 times.The difference between the two is 5.8 %.The temperature load plays a key role in the damage evolution process of the pavement structure.5)Under the coupling effect of temperature load and vehicle load,the fatigue life of the pavement with cement-stabilized filled large aggregates as the base is 26116 times,while the fatigue life of the pavement with conventional cementstabilized aggregates as the base is 23952 times,with a difference of 9.0 %.The application of cement-stabilized filled large aggregates to the base can better improve the fatigue life of the pavement.