Study On Uplift Bearing Capacity Of Cone-column Foundation And Pile Foundation Of Transmission Line In In Frozen Soil Region

In recent years,with the rapid economic development of permafrost regions in China,the country has also increased the construction of transmission lines in permafrost regions.Due to the differences in engineering properties and the particularity of power engineering,many key problems need to be solved urgently in the process of transmission engineering construction in permafrost region(especially large-scale transmission engineering construction).The bearing capacity of foundation in permafrost region is one of the most important problems.In this paper,the standard values of important mechanical parameters in frozen soil are studied,and the tensile bearing properties of conical pillar foundation and pile foundation in seasonal frozen soil and permafrost soil are studied,which provides methods and references for the design and construction of overhead transmission line foundation in frozen soil.The main contents of this paper are as follows.(1)The most significant factors of frozen soil mechanical parameters,such as unit tangential frost heave force,freezing strength between frozen soil and foundation,and shear strength of frozen soil,and the optimal fitting curve equation were obtained through multiple curve fitting.Through the statistical analysis and processing of the test data of mechanical parameters of frozen soil under the most significant factors,the logarithmic normal distribution was used to fit the distribution,and the standard values of mechanical parameters of frozen soil under the 95% guarantee rate were obtained.(2)By using FLAC3 D finite difference software cone column foundation has carried on the transmission line in permafrost area numerical simulation of the uplift bearing performance under various operating conditions to draw out the t-s curve of load displacement under various operating conditions is obtained on the top load and displacement relationship is pull,the change rule of "slowly" under various operating conditions and cone column based on the limit bearing capacity of pull;The morphological parameters and variation rules of actual uplift fracture surface of conical column foundation in different permafrost regions and different subsoil are obtained.The drawing Angle of fracture surface is calculated by using the method of internal cutting and force balance,and the range of drawing Angle is given by combining the two methods and engineering experience.(3)By FLAC3 D finite difference software transmission lines pile foundation in permafrost area are the numerical simulation of the uplift bearing performance under various operating conditions to draw out the t-s curve of load displacement,under various operating conditions has been on the top load and displacement relationship is pull,the change rule of "slowly" under various operating conditions and the pile foundation bearing capacity of the corresponding limit drawing;The influence of horizontal load on the uplift bearing capacity of pile foundation is analyzed.The influence of the thickness of soil active layer on the ultimate uplift bearing capacity of pile foundation is analyzed.(4)According to the specification and the paper recommended formula and parameters of theoretical foundation uplift bearing capacity and safety coefficient are calculated respectively,and compared with numerical simulation values and norms,comparing the design safety coefficient by numerical simulation value uplift bearing capacity are less than the theoretical value,the calculation model for the safety coefficient is higher than the standard design safety factor,to verify the numerical simulation results meet the specification,suggests that this article recommended the rationality of the formula and parameter calculation results.