| Nowadays, with the extending of highway construction to the mountainous and hilly area as well as the widening and reconstruction of the existing roads, slag has become a must-choice for embankment fill material. Slag is a general term for soil-stone mixtures, construction wastes, wastes of pavement and bed layer of the exiting roads and etc. Slag has many good features such as high strength and compaction density, small settlement, strong water permeability and scouring-resistance, and it is also easily available. However, since the stone content, grain diameter and the grain size distribution of the slag range greatly, it is hard to control the compaction quality of the roadbed.This thesis chooses the slag from a highway test section as the research object. The roller compaction technology is researched in detail and the on-site settlement observation during the roller compaction process is carried out. PFC2D is applied to simulate the roller compaction process of the slag and the result of the simulation is compared with the result observed in situ. Based on the comprehensive analysis of the compaction characteristic of the slag, a computing formula is proposed to calculate the maximum dry density of the slag. Combined with the on-site dynamic tests, the relationship between dry density and dynamic master frequency and between dry density and the velocity of Rayleigh wave are obtained. At last, the slag is sieved and scaled, and the GDS triaxial test is conducted with three different grading parameters. The model parameters of the Duncan-Chang model are obtained from the GDS triaxial test.The main contents of this thesis include:(1) On-site roller compaction test, sieving test and settlement observation during the roller compaction process have been conducted;(2) The PFC2D numerical simulation of the roller compaction process of the slag is carried out;(3) Compaction characteristics of the slag are analyzed and the maximum dry density is calculated, dry density test of the slag embankment is also conducted;(4) GDS triaxial test of the slag is carried out.The main achievements obtained from the research:(1) The best paving thickness of the slag embankment is 30cm. A heavy vibratory roller is used to roll the slag embankment: firstly, static press for one time, then dynamic press for three to six times, finally, static press again for 1 to 2 times until the rolling trace disappears. The result from the on-site settlement observation indicates that the slag settlement is basically stable after six times of roller compaction;(2) The roller compaction properties are simulated by PFC2D, the simulation results react to some extent the on-site roller compaction situation, and the displacement and load situation of the particles are observed from the simulation. The simulation results agree well with the on-site situation;(3) The maximum dry density formula proposed in this thesis has taken into account several factor which influence dry density including coarse fraction, the maximum diameter and the nonhomogeneity of the slag particles. Given the coarse fraction and the maximum diameter, the maximum dry density will be estimated;(4) The result of the GDS triaxial test shows that the stress-strain curve of the slag is not very smooth with some fluctuation in local areas. However, the overall trend is clear with no obvious strain softening. But the volume deformation rule is very complex.The innovative points of this thesis:(1) Simulate the roller compaction process of the slag with PFC2D;(2) Propose a formula to calculate the maximum density of the slag;(3) Provide the simulation parameters for Duncan-Chang model.
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