Study On Seismic Settlement Of Gravel Filled Steel Pipe Pile For Reinforcement Of Different Densuty Of Soil

Liquefied foundation reinforcement has been a difficult problem. In recent years, earthquakes have occurred, recently took place in Kumamoto, 7.1 earthquake has caused many people were killed, also caused the great loss of property.Due to the earthquake, groundwater level is very easy to rise, if this does not take effective prevention of the liquefied soil, the foundation is very likely to liquefaction, the caused by the disaster occurred immeasurable.light houses damaged caused, heavy personnel casualties.Therefore, to continue to increase research in this area is particularly important. gravel pile to eliminate the liquefaction has been a lot of research results. the study of composite pile foundation reinforcement of liquefied soil foundation has also been applied to the actual project.However, the research on the influence of the compaction degree and the pile number of the composite reinforced liquefied soil under the upper load of the gravel filled core pile is needed to be further studied. Therefore to explore the effect of different density and different number of piles in liquefied soil has certain practical significance.Relying on the National Natural Science Foundation of China(51408393) "Study on the vibration mechanism of PHC pipe pile in unsaturated soil under seismic wave", The main research in the upper 5kg load of four piles reinforcement model、Five pile reinforcement model、Nine pile reinforcement model. In three kinds of different density loose dense sand(ρd=1.5g?cm-3)、Medium dense sand(ρd=1.6g?cm-3)、Compacted sand(ρd=1.7g?cm-3).A total of nine groups of experiments,Collecting pore water pressure, soil settlement rate, soil pressure at different depths of three kinds of data drawing curves,Collate analysis found.The same compacting degree of filling core steel tube pile in loose sand foundation and pile number increases of soil liquefaction effects, but the impact strength is limited, which suggested that the sand compaction is the effect of foundation liquefaction main controlling factors; with the density increase of pile number of impact by gradually emerge, especially in medium dense sand has the most significant effect, at this time of the pile quantity and sand density together of foundation reinforcement effect; in dense sand influence is not very big, then pile number also plays certain reinforcement effect.(1)Pore water pressure: the change of pore water pressure is first increased and then decreased, and then gradually dissipated after reaching the peak value.The deeper the buried depth is, the greater of pore water pressure is.The peak value of pore water pressure decreases with the increase of density.With the same density, the peak value of pore water pressure decreases with the increase of the number of piles.(2)Soil pressure change:The value of soil pressure decreases with increasing depth of the buried depth.The greater density of the soil and more number of piles,the smaller the change of soil pressure.Vertical soil pressure increased along with the buried depth. Under the vibration load, the earth pressure is decreased in the same depth of the earth.(3)Settlement change: The larger the density, the smaller the settlement, the maximum surface subsidence.The amount of settlement is decreased gradually, and the settlement of the surface is almost two times of of 36 cm.The number of piles can also reduce the amount of settlement, but the density is too small or too large, the effect of increasing the number of piles is not obvious.When the dry density is 1.5g?cm-3 and 1.7g?cm-3 the amount of the pile increases not obvious with the increase of the quantity of the pile.The dry density of 1.6 g?cm-3 with the increase of the number of piles can effectively reduce the settlement of the foundation.Therefore, in the process of strengthening the soil, the relationship between the density and the quantity of the pile should be considered.In words: gravel filled core steel pipe pile reinforcement of liquefied soil foundation can not only reduce the pore water pressure can also improve the bearing capacity of the foundation, can play a good effect of reinforcement.