Study On Meso-simulation Of Rolling Process And Compaction Mechanism Of Rock-fill Dam Material

The thin layer filling and layered rolling is usually used in rock-fill dam construction.And the key to ensure the dam safety is to control construction quality during of compaction,which is mainly controlled by compaction parameters.Because of the difference of rock-fill dam material properties(i.e.,gradation,moisture content),compaction parameters have to be determined by the field trial compaction test,which consumes labour,material and financial resources.Therefore,the Particle Flow Code(PFC)was used to simulate rock-fill dam rolling process from the mesoscopic point of view,and mesoscopic compaction mechanism of rock-fill material during rolling process was analyzed.Meanwhile,the influence of different compaction parameters on compaction quality was studied,which could provide a theoretical basis for real-time control of rock-fill dam construction quality.The major research achievements of this thesis are as follows:(1)A fine modeling method of 2D,3D rock-fill dam material was proposed,and the quantitative matching relationship of porosity between 2D and 3D models was established,and the formula for calculating the equivalent load of rigid roller was modified with the size effect.Firstly,2D and 3D dam material particles are created basing on the 3D laser scanning technology,which can reflect the real shape of aggregate.Then a compression plate loading model,which was same in 2D and 3D modeling process,was established to match the corresponding porosity between 2D and 3D models.Finally,a modified equivalent load formula was proposed using the vibrating simulation tests of the real and the small size rollers,respectively.(2)A discrete element modeling method of the whole construction process rock-fill material including dumping,paving and compaction phases,was proposed.And then the effect of compaction parameters on rock-fill material compaction quality was analyzed.First of all,material dumping progress was modeled based on particles falling.Then,the paving progress was achieved by deleting needless particles.Next,compaction progress was performanced by employing the related vibration load to the roller size.The research results indicate that lower velocity and larger force caused better compaction quality,while thicker lift of paved layer caused adverse consequences.Further,the lift thickness is the most sensitive parameter to rock-fill material compaction quality.(3)By monitoring particles in the dam material-roller system,the movement law of particles during compaction process was studied.It shows that the vertical acceleration of particles decreases exponentially along the particle-located depth,and the particle vertical velocity and vertical displacement decrease with the particle-laceted depth increasing.The vertical velocity of particles is decreasing as rolling passes increase at the same location,while the vertical displacement increases inversely.During compaction process,smaller particles have higher speed and greater displacement than the bigger ones.