Seismic Response Analysis Of Lime Soil Pile Composite Foundation

As a flexible pile, the lime soil pile is widely used in foundation treatment. This papersummarizes the current status quo of researches about the lime soil pile composite foundationand the dynamic characteristics of composite foundation. On the dynamic characteristics,there are researches about the rigid pile composite foundation such as CFG piles, cementmixing piles and gravel piles, but there are little researches about flexible pile compositefoundation such as lime soil piles on dynamic characteristics. On this basis, the purpose andsignificance of this paper are proposed.In static analysis, the static load test of composite foundation is simulated. The pile-soilstress ratio, the pile settlement and the soil settlement are analyzed, and the general shearfailure of composite foundation is discussed. The results show that: the cushion caneffectively regulate the pile-soil stress ratio and makes the bearing capacity of the lime soilpiles and the soil between piles giving full play to at the same time. The cushion has a distinctrole in reducing the settlement of the lime soil pile; however, has little effect in reducing thesettlement of the soil between piles. The reasonable thickness of the cushion is about300mm.The composite foundation will emerge general shear failure when it reaches the ultimatebearing capacity. Reducing the pile spacing can increase the ultimate bearing capacity ofcomposite foundation.In dynamic analysis, the pile groups model is established. It respectively analyses thenatural foundation and the composite foundation of using different reinforcement schemes. Itstudies the natural vibration frequency, the rules of the acceleration, the velocity, and thedisplacement on the reinforcement area center, the reinforcement area edge and the modeledge, the rules of shear stress and displacement of enter pile, side pile and corner pile.Compared with the natural foundation, the first three natural vibration frequencies ofcomposite foundation are increased, but the size of the increase is not obvious. Thereinforcement does not change the natural vibration frequency of the site, so it will notincrease the seismic response of the site. The composite foundation with differentreinforcement schemes have different natural vibration frequencies. The first order naturalvibration frequency difference is very small, and the second-order and the third-order naturalvibration frequencies have bigger differences. It shows that the composite foundation hasstable first order natural vibration frequency. The effect of replacement rate for naturalvibration frequency is larger, with the increase of replacement rate, natural vibrationfrequency increases gradually. When the reinforcement depth increase, the natural vibrationfrequency also increases, but slightly. On the site surface of reinforcement area center, reinforcement area edge or model edge,compared to the natural foundation, the acceleration, the velocity and the displacement ofcomposite foundation have obvious decreased. It shows that the reinforcement has a greatimprovement on seismic resistance. Replacement rate has great effect on the acceleration, thevelocity and the displacemen, but the change of reinforcement depth has little effect on them.The displacement of center pile is the maximum, followed by the side pile displacement,and the displacement of corner pile is the minimal. The pile displacement decreases with theincreasing replacement rate, the reinforcement depth has no effect on the pile displacement.For the shear stress, the shear stress of center pile is the minimal, followed by the side pileshear stress, and the shear stress of corner pile is the maximum. The larger value of the shearstress appear at the top and the bottom, the maximum shear stress appears at the bottom of thepile. With the increasing of the replacement rate, the pile shear stress decreases. Changing thereinforcement depth has little effect on the pile shear stress.