Model Test On Bearing Capacity Of Single Pile Under Cyclic Load In Saturated Loess

The pile foundation of the monolayer industrial workshop with large bridge cranesshould not only bear the weight of the static loading of the upper stucture, but also bear thecyclic loading of the cranes at work. The characteristics of this kind of loading are that it hashuge cyclic loading and no fixed-frequency. According to earth’s dynamic constitutive modeland pile-soil interaction mechanism, we know that there are obvious differences between pilesunder the cyclic loading and static loading. The cyclic loading can greatly affect thecharactristics of the single pile and the pile can decline obviously in this condition. There aremany elements which will affect the characteristics of the pile under the cyclic loading, e.g.cyclic loading frequency, The amplitude of cyclic load, cyclic load ratio, material’scharacteristics of the pile, the characteristics of the soil around the pile, The dynamic stiffnessof the soil, The stiffness ratio of the soil and the construction technology of single pile and soon, which will have an effection on Settlement of single pile and the stress transfer. Thepurpose of this piece of thesis is to analyse the charactristics of stress transfer under the cyclicloading and static loading and study the affection of different amplitudes of cyclic load anddifferent soil filling on the pile with the method of model experiment.Taking a monolayer industrial workshop along the Yellow River as an example, Icaculated the structural load of the workshop, the Maximum cyclic load ratio of the piles andthe cranes’ cyclic load ratio in frequent using according to its rank of using. We alsoinvestigated the characteristics of the using of the cranes and the stress characteristics of thepiles.An experimental system of cyclic loading was deceloped to assist my study, which usespneumatic way to press and signal generator to control the pressure by adjustingelectro-pneumatic proportion pressure valve. In the meantime, I measure the displacement ofthe pile’s top by using electromechanical indicator and the strains of piles by using resistancestrain gage. I found through the simulation testing that this system of cyclic loading can meetthe requirement of model test and provide valid and accurate data. So it can be used in thestudy.Different experiments were made during the study, for instance, the test of static bearingcapacity of the soil around pile under different conditions, the test of cyclic loading indifferent cyclic load amplitude and the test of displacement and the strains of piles underdifferent conditions and so on. After analysing the data, I found that the higher thedisplacement ratio of the pile is, the larger the the amplitude of cyclic load will be. And thedisplacement of the piles in sandy clay is the most affected one by cyclic loading. So is thedisplacement of the piles in saturated loess. Besides, the pile side resistance reduces greatly under the action of cyclic loading, while the counterforce of in the bottom of the pilesincreases.At last, some reasonable suggestions and references are proposed about the designingand construction of the piles of the buildings under the cyclic loading according to theresearch conclusion in the thesis.