Study On Uplift Mechanism Of Transmission Line Cone Column Foundation In Permafrost Regions

Frozen soil is lower than 0 ? temperature of the soil or rock,more accurate expression of soil mixture is a kind of ice ice soil or rock and soil.Its unique properties,especially for temperature and water,are high sensitivity.The construction of permafrost regions is largely restricted by the characteristics of frozen soil,which leads to damage caused by frost heave or thawing precipitation in the frozen soil area.With the rapid development of the west to East power transmission project,the transmission line involves a lot of projects in frozen soil area.The special working condition of the transmission line base makes it carry horizontal thrust and uplift force besides self weight,which will lead to the frost heave and thawing damage of the transmission line foundation in the permafrost region.Therefore,in this paper,the combination of field test and numerical simulation is used to investigate the stress characteristics of the transmission line foundation in permafrost regions,especially a special form of the foundation “cone column foundation” as the research object,and the field test is used to study its level.The load-bearing performance of the foundation under loading and updraft loads;anti-frost heave simulation of the cone foundation using finite difference simulation software,establishing a cone-post foundation model with different pile-side inclination angles,obtaining the effect of different inclination angles against freezing,and deriving inclination angles Pulling out the prediction formula of displacement,and put forward the optimal inclination angle of cone-pillar foundation in permafrost transmission line.The test results show that the melting period is slightly larger than that of the uplifting test during the freezing period,and the horizontal displacement of the cone foundation subjected to the horizontal limit load is relatively large;the backfill quality of the excavation and backfill surrounding the foundation is to affect the pullout resistance.For the key factors of bearing performance and horizontal anti-sway performance,the horizontal displacement and uplift displacement increase as the degree of looseness of the backfilling soil increases;when the pullout load is low,the axial force decreases with depth,and the upper side of the foundation sidewall resistance Play;As the load increases,the axial force decreases with decreasing depth,the lower sidewall resistance is excited,and the axial force at the ultimate load changes little;numerical simulation results show that: the amount of frozen extraction decreases with the increase of pile side angle Theoretically,the amount of freeze-pumping tends to be 0 as the pile side angle increases indefinitely;considering the actual project cost,construction and other factors,it is recommended that the transmission line foundation in the permafrost region be able to overcome the tangential frost heave force with an optimal inclination of 10°.