| In practical engineering,the bearing capacity of collapsible loess foundation decreases significantly after being soaked by water,causing ground deformation and destruction of upper structures.Therefore,it is necessary to reinforce the foundation to avoid engineering safety accidents.In this paper,the technology of remolding loess by 2.45 GHz microwave sintering is tentatively explored.The technology is a kind of thermal reinforcement method which uses microwave to heat the soil to high temperature to eliminate the collapsibility of soil,increase the strength of soil and improve the bearing capacity of foundation.The three microwave heating antennas are evaluated by numerical analysis and laboratory test;The temperature change law of soil under the action of microwave and the influence of density and moisture content on temperature are analyzed;The relationship between microwave field and temperature field is explored;The strength of soil after microwave sintering was tested.The main research contents and conclusions are as follows(1)Numerical analysis and indoor test are carried out on the existing rectangular waveguide antenna,circular waveguide slot antenna and monopole antenna.The performance and actual heating effect of the antenna are evaluated.The monopole antenna has the best comprehensive performance.(2)Through the indoor microwave heating test,the soil temperature change is divided into three stages: 0 ～ 95 ℃ preheating heating stage,95 ～ 100 ℃ stagnant drying stage and continuous rising stage after 100 ℃.The influence of soil density and moisture content on soil temperature in each stage is analyzed.(3)The correlation between microwave field and temperature field in soil is analyzed by numerical method.Combined with the indoor test results,the effective drying range of loess heated by microwave at this frequency is determined to be about 11.5cm,and the heated soil is divided into baking area,burning through area,drying area and non drying area.(4)Through the compressive strength test of the microwave sintered specimens,the relationship curve between the strength and density,moisture content of the sintered specimens heated at about 600 ℃ is obtained,and compared with the strength of the traditional sintered brick specimens,the reasons for the strength difference are analyzed,and the simple suggestions for the microwave sintering heating test are put forward.In this paper,through the combination of laboratory test and numerical analysis,the basic law of soil temperature change and the effective heating range of 2.45 GHz microwave heating in remolding loess are clarified.At the same time,a preferred heating antenna is recommended,which lays a certain foundation for the follow-up research. |
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