| Nowadays,with rapid economic development and population expansion,land desertification is increasingly severe.All countries are taking effective measures to prevent and control it.Traditional controlling methods for desertification however,cannot meet today's epoch topic of green environmental protection.As a new type of environment-friendly technology,microbial induced mineralization technology has the characteristics likeswift response and controllable process,and is being increasingly applied to soil reinforcement and improvement and introduced into geotechnical engineering.The solidification of microorganism to sandy soil is applied in desert,which was taken as the engineering background of this paper to study the freeze-thaw and ultraviolet characteristics of microbial solidified materials in the complex environment of desert.Mineralization technology for inducing the formation of calcium carbonate during the metabolism of Bacillus bacillus itself,mineralizing desert sandy soil,improving the integrity and strength of the material.In this paper,Bacillus pasteurii,which widely exists in soil,was used to hydrolyze urea with urease produced by its own metabolism to generate calcium carbonate to mineralize Aeolian sandy soil,thus improving the integrity and strength of the test piece.In this paper,the quality,appearance,saturated moisture content,strength and microscopic changes of the two MICP technologies cured by traditional MICP technology and improved MICP technology were studied under freeze-thaw cycle test.Nuclear magnetic resonance and SEM were used to study the pore changes,pore size distribution and microscopic changes of the three specimens under UV irradiation and UV freeze-thaw combined erosion.The test results showed that the unconfined compression strength of the Aeolian sandy soil specimen mineralized by traditional MICP technology is 775 kPa,and the failure mode is obvious brittle failure.In order to improve this phenomenon,polymer materials A and xanthan gum(B)were added in the test.The strength of the two specimens cured by the improved MICP technology is higher than that of traditional specimens.The strength value of the MICP-B specimen is 1.59 times that of traditional specimen,and the strength value of the MICP+A specimen is 2.10 times that of traditional specimen.The cohesion of the conventional MICP specimen is 46.84 kPa,and the cohesion of the improved MICP-B specimen is 122.16 kPa.After freeze-thaw cycle tests,the unconfined compression strength values of the two MICP cured specimens decreased with the increase of freeze-thaw cycle,while the mass loss rate and moisture content increased.After 3 freeze-thaw cycles,the freeze-thaw resistance of the traditional MICP specimen decreased to 50%,the strength of the improved MICP-B specimen decreased to50% after 7 cycles,and the strength of the MICP+A specimen decreased to 51% after 10 cycles.Therefore,the specimens cured by improved MICP technology with strong freeze-thaw resistance.After UV irradiation,the porosity of the cured specimens by the two MICP technologies increased with the increase of irradiation period.After 15 irradiation periods,the porosity of the traditional MICP specimens increased by 23.66%,and becomes 1.24 times that of the original.The porosity of the improved MICP-B specimen is 1.77 times that of the original,and the porosity of the MICP+A specimen is 1.33 times that of the original.After UV freeze-thaw combined erosion,the porosity of MICP specimen is 1.307 times that of the original,the porosity of MICP-B specimen is 1.853 times that of the original,and the porosity of MICP+A specimen is 1.348 times that of the original.The specimen mineralized by the traditional MICP technology has the least increase in porosity and good ultraviolet resistance after being irradiated by ultraviolet rays.Through the freeze-thaw test and the UV-erosion test,it is known that the cured materials of the two curing technologies can better adapt to the cold regions.The traditional MICP technology has better UV resistance and better application.In areas with high UV radiation intensity.Through the freeze-thaw test and the UV-erosion test,it is known that the cured materials of the two curing technologies can better adapt to the cold regions.The traditional MICP technology has better UV resistance and better application.In areas with high UV radiation intensity. |
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