Type-selection Of Cone Cylindrical Foundation In Permafrost Areas At High Altitudes And Finite Element Analysis

Based on the permafrost characteristics of Wudaoliang region and design principles of powertransmission line tower foundations in permafrost areas, two kinds of tower foundations includingcone cylindrical foundation and precast tubular pile foundation are selected to take a field test. Theexperiment is divided into two parts which are freezing period and thawing period, and both periodsare applied to two conditions which are uplift and horizontal load and pressure and horizontalload.Through the observation of the pile foundation displacements, internal forces and the earthpressure, Q～s curves and axial force diagrams of different section under the grading load were got.Research and analysis indicates that cone cylindrical foundation bearing performance is better due toits reasonable design and type-selection, which can be used as the Qinghai-Tibet direct-voltagetransmission lines foundation. While for the pipe pile foundation, its characteristics of regular sectionsand smooth sidewalls caused its poor pull-resistance performance, which cannot be used astransmission line foundations of larger uplift loading.Through the experiments and theoreticalcalculations, the formula of ultimate bearing capacity of pile foundations suitable for permafrostregions with large wind load was established.As frozen soil parameters are difficult to obtain from the experiment, BP neural network wasused for parameters inversion, which can get the parameters of constitutive mode of Mohr-Coulombfor the calculation of the finite element model. After three-dimensional finite element model of thecone cylindrical foundation in the frozen soil was established, we can get the vertical and horizontaldisplacement nephogram. With a contrastive analysis to the experiment conclusion, the accuracy andapplicability of the model was verified. The analysis of the finite element model indicates that whenthe thawed soil depth is2m, the effect on the uplift ultimate bearing capacity and ultimatedisplacement is much more than the pressure ultimate bearing capacity and ultimate displacement.