Research On Buoyancy Reduction Of Underground Granary Based On Terzaghi Effective Stress

Grain is the life of the people,the treasure of the country,and the food problem has been a major event to maintain social stability since ancient times.Underground granary has become the development trend of future granary because of its high degree of mechanization,high concealment,land saving,energy saving,constant low temperature and other advantages.Nowadays,the anti floating design of underground structures,including underground granary,mainly relies on Archimedes law to calculate the buoyancy of underground structures,and then carries out anti floating design,without considering the influence of favorable factors such as lateral friction and adsorption of surrounding soil.Based on Terzaghi’s effective stress and considering the working condition of backfilling 28 lime soil on the side wall of underground granary,this project takes the actual underground granary as the research background.Through the scale model of underground granary,the vertical diameter of underground granary is 400mm,500mm and 600mm respectively,and each group is divided into three types:10cm,20cm and30cm Nine groups of water injection buoyancy tests were carried out.The research analyzes the following contents(1)Based on the effective stress of Terzaghi,the calculation method of the side friction and the adsorption force of the soil on the side wall of the underground granary to the underground granary is proposed,and the calculation model of the actual buoyancy is constructed,and the test scheme of the underground granary water injection test is designed.(2)Through the density test and geotechnical test of 28 lime soil,the dry density,saturated density,internal friction angle,cohesion and other physical parameters of side wall backfill 28 lime soil during water injection test were collected.(3)Based on the effective stress of Terzaghi,the adsorption force and side friction of the soil on the side wall of the underground granary are calculated,and then the actual buoyancy of the underground granary is calculated.(4)ABAQUS finite element simulation software was used to verify the test results.Through the research of the research content and the analysis of the test results,the following conclusions are obtained(1)The starting water level of the force analysis of the movement state of the underground granary is earlier than the starting water level of the displacement of the underground granary observed in the experiment,which shows that the starting water level of the underground granary has a certain lag compared with the movement state of the force angle,and it also proves that the underground granary is affected by the side friction and adsorption force of the side wall backfill soil,which are conducive to its floating force.(2)When the diameter of the underground granary is 400mm,the buoyancy reduction coefficients are 0.98,0.95 and 0.92 when the height of the backfill is 10cm,20cm and30cm respectively;when the diameter of the underground granary is 500mm,the buoyancy reduction coefficients are 0.96,0.94 and 0.90 when the height of the backfill is 10cm,20cm and 30cm respectively;When the diameter of the underground granary is 600mm,the buoyancy reduction coefficients are 0.94,0.91 and 0.88 when the height of the backfill 28 lime soil on the side wall of the underground granary is10cm,20cm and 30cm respectively.The test results show that the increase of the backfill height of the side wall of the underground granary will improve the anti floating ability of the underground granary,specifically for every 10 cm increase in the backfill height of the side wall of the underground granary,it can resist 3%more buoyancy.(3)The finite element software ABAQUS is used to simulate the water injection buoyancy test of underground granary.The results show that the simulation results of the water level and buoyancy reduction factor of the water injection buoyancy test of underground granary are basically consistent with the experimental results.The absolute value of the maximum deviation rate of the buoyancy level is 3.6%,and the absolute value of the maximum deviation rate of the buoyancy reduction coefficient is2.2%.It shows that it is reliable to simulate the influence of underground water level on the underground Granary Based on Terzaghi by constructing the finite element model,which provides a reference for the future anti floating design.(4)Taking the contact area of underground granary and its side wall backfilled with 28 lime soil as an independent variable,it is found that with the increase of contact area,the water level of underground granary rises gradually,and the anti floating ability of underground granary increases.Specifically,for every 1 m~2increase in the contact area between the underground granary and its side wall backfill,the floating water level of the underground granary increases by 0.257 M.(5)Through MATLAB software,the least square method is used to deduce the calculation formula of the buoyancy level and buoyancy reduction coefficient of the underground Granary under the backfill condition,so as to provide theoretical guidance for the future anti floating design.