3D FEM Analysis Of Differential Settlement Of Gravel Pile Foundation Under Large-scale Oil Tank

The characteristic of large storage tank are large in diameter, heavy load, prone to uneven settlement tank foundation.These can cause the local buckling of tank wall, and pose a serious threat to safety storage tank. Therefore we need to treatment the ground of the large storage tank. The vibroflotation gravel pile composite foundation method is widely used in the foundation treatment of large volume oil tank because of simple to the construction and good treatment effect. At the same time, by water filling preloading method to further reinforce after completion of the construction of composite foundation can accelerate the speed of the foundation treatment.In this paper, taking Jiangsu 150000 cubic meters of very large floating roof tank construction project as an example. Combined with the related monitoring data and using large-scale finite element software Plaxis, we establish the 2d and 3d finite element model, By elastic-plastic numerical simulation and the corresponding calculation, and compared with field test data, verify the availability of finite element model. The 2d model calculation data,3d model calculation data is compared with the measured values,3d model analysis computational advantage. Using the finite element model, and further discusses the gravel pile composite foundation under different load and foundation stiffness of long pile and short pile distribution range of the influence of differential settlement of composite foundation. The following conclusions:(l)Through the plaxis software can gravel pile composite foundation for large storage tanks for 2d and 3d finite element numerical simulation.The simulation results with the measured trend similar to the results of 3d simulation results more close to the measured values, show that the finite element simulation of parameter setting and simplified method is reasonable, advice in the practical engineering application by 3d numerical simulation; (2) Gravel pile composite foundation settlement of the three dimensional numerical simulation of oil tank bottom, ring wall subsidence value, tank outside the surface subsidence value meet the design requirements. Tank away topsoil subsidence value decreases gradually with the increase of from the center of tank, and 70 m from the center of tank (0.7 D) surface subsidence has been basically is 0, so can be ignored in actual engineering; (3) Adjust the distribution of the gravel pile can effectively reduce the differential settlement of composite foundation. For this case, the pile arrangement range of 0～ 23m long, pile layout in the range of 23-34m minimum differential settlement of composite foundation, through adjusting scope of gravel pile arrangement can effectively reduce the differential settlement.In the process of reality construction when the tank is usually composed of multiple storage tanks tank group was formed by a certain arrangement. As a result of the limitation of engineering site, the relatively close distance between the storage tanks. Each storage tank foundation superimposition, the pore water pressure and effective stress in the composite foundation sink further. Differential settlement is very easy to produce the oil tank, a serious threat to its safe use. For studying the effect of tank group on the influence of sedimentation tank, this paper combined with Yizheng large oil tank project corporation. By choosing the appropriate material models and the gravel pile were reasonably simplified, establish made up of two large oil tank finite element model of tank farm. Through the distribution of load simulation, get close to reality monitoring data comparison of calculation results, which prove that this model is valid. On this basis, the analysis under the different water filling load method, the composite foundation settlement and differential settlement tank affected, to determine a reasonable scheme of water filling and provide reference for similar projects for the future. The following conclusions:(1)Using software praxis finite element numerical simulation of the tank can be approximate model calculation results and the test result, this article points material parameter selection and gravel pile of the simplified method is reasonable. (2) In this paper, two storage tank foundation settlement tank group effect. Influence degree is inversely proportional to the oil tank foundation by load. Embodied in tank floor near the tank group inside edge to produce relatively large settlement, tilt tank to tank group inside (3) When two storage tanks water filling, water filling of deformation of tank bottom is greater than the early late filling water tanks. With water filling method, respectively, the settlement amount is more than use synchronous filling water tank settlement. Engineering in the future, in tank group composed of two oil tank for water filling preloading, can be used at the same time, water filling scheme, can be the most the earth to reduce differential settlement, to ensure the safe use of tank.