The Analysis Of Dynamic Property Of Embankment Reinforced With H-V Inclusions By Laboratory Test And PFC^2D Simulation

Horizontal-vertical inclusion （H-V inclusion） is a new type reinforcementwhich consists of conventional horizontal inclusion and vertical elementsinstalled on the horizontal inclusion at spacing. Besides the friction betweenhorizontal inclusion and soil, the vertical inclusions provide passive resistancesagainst shearing and form enhanced areas （the soil enclosed within two verticalreinforcing elements） to increase the strength and stability of reinforced soil.The former researches on the static property of soil reinforced with H-Vinclusions have proved that H-V inclusions can improve the soil strength andrestrict the soil deformation more effectively than conventional horizontalinclusions. In order to enrich the researching system of H-V inclusions so as tofacilitate the application of H-V inclusions, preliminary researches wereperformed on the dynamic properties of soil reinforced with H-V inclusions andthe dynamic response of reinforced embankment through three main methodsincluding dynamic triaxial tests, model tests under cyclic loadings and PFCsimulation. The main works in this dissertation were as follows:Through dynamic triaxial tests, the dynamic modulus and damping ratio ofreconstituted clay reinforced with H-V inclusions were analyzed under theisotropic confining pressure, which were unconsolidated-undrained dynamictriaxial tests. And that, the dynamic modulus and damping ratio of saturatedsand reinforced with H-V inclusions were studied through anisotropicconsolidated-undrained dynamic triaxial tests. It is shown that not only in thecase of reconstituted clay, but also in the saturated sand, the H-V inclusionsimprove the soil dynamic modulus more effectively compared to the horizontalinclusions and in the varied height of vertical inclusions （5,10,15,20mm）, thedynamic modulus increases with the height of vertical inclusions increasing,despite the case of20mm high vertical inclusion. The damping ratio is insensitive to the height of vertical inclusions, however, it should be noted thatthe damping ratio of some soil reinforced with H-V inclusions was smaller thanthat of soil reinforced with H inclusions.The dynamic triaxial tests of saturated sand reinforced with H-V inclusionswere simulated through the particle flow code software (PFC^2D). It is found thatthe inherent contact model （Hertz-Mindlin contact model） can reflect thenonlinear and hysteretic property of soil well. As the amplitude of dynamicstress increases, the porosities of unreinforced sand and reinforced sandincreases and the coordination number （average number of contacts per ball）decreases; it means the degradation of stiffness of saturated sand. Meanwhile,the excess pore pressure of saturated sand increases with the amplitude ofdynamic stress increasing; it shows the decrease of effective stress of saturatedsand. In the same amplitude of dynamic stress, the H-V inclusions moreeffectively restrict the increase of excess pore pressure compared to the Hinclusions.By the scale-down model tests, the accumulated settlements and lateraldisplacement of embankment reinforced with H-V inclusions were studied underthe cyclic loading acting on a strip foundation. The accumulated settlements ofboth unreinforced and reinforced embankment increase with the number ofvibration increases. The bigger the amplitude of dynamic stress, the greater isthe settlement. In the same condition, the H inclusions restrict the accumulatedsettlements and lateral displacements of embankment, the H-V inclusionsperform better than the H inclusions. Moreover, the tests of continuously appliedloadings with increasing amplitudes were performed to prove that theembankment reinforced with H-V inclusions can bear greater amplitude ofdynamic loading. In addition, the bearing capacity of the embankment undermonotonic loading after some periodical vibrations was studied. The resultsshow that: when the amplitude of dynamic stress is smaller than the threshold dynamic stress the unreinforced embankment can bear, the bearing capacitiesunder monotonic loading of both unreinforced and reinforced embankment wereimproved after periodical vibrations, it is obviously observed in the reinforcedcases. In the same number of vibration, the bigger the amplitude of initialapplied cyclic loading, the greater is the bearing capacity under monotonicloading; the bearing capacity of the embankment increases with the number ofvibration increasing under the same amplitude of cyclic loading.The simulation results based on PFC^2Dverified the conclusions obtained fromthe dynamic model tests and the reinforcing mechanism of H-V inclusions wasanalyzed through the distributions of displacement vectors and contact forces ina microscopic view. The analysis shows that the H-V inclusions can improve thesoil compactness and uniformly transmit the upper loading so as to minimize thesettlement and lateral deformation of the embankment reinforced with H-Vinclusions. What is more, the effect of the frequency of cyclic loading on thesettlements of the embankments was discussed in the simulation results. In thefour frequencies of1,2,5and10Hz, the settlements of unreinforced andreinforce embankments decrease as the frequency increases, and the settlementsof the embankment under the greater frequencies have small differences. Underthe same frequency of cyclic loading, the restriction effect of H-V inclusions onthe settlement is better than that of H inclusions, however, as the frequencyincreases, the advantage of restriction effect of H-V inclusions over H inclusionsweakens.