微生物诱导矿化风沙土的紫外侵蚀微观试验研究

Micro-experiment on MICP-treated Aeolian sandy soil under ultraviolet erosion environment

基于微生物诱导矿化(MICP)技术,以乌兰布和沙漠风沙土为岩土基质,对基于MICP技术诱导矿化风沙土的紫外侵蚀特性进行微观试验研究。模拟乌兰布和沙漠地区的冬季紫外线照射量,且将乌兰布和沙漠地区冬季室外紫外线照射总的有效时间等同于室内紫外线照射总有效时间,确定室内紫外侵蚀试验的紫外照射时间,并运用微观电镜扫描和核磁共振技术,在相同的紫外线照射强度下,研究矿化风沙土试件的孔隙特征随照射时间延长的变化规律。结果表明:经过紫外线照射后,微观电镜扫描显示MICP矿化试件在紫外线长时间照射下,碳酸钙晶体出现孔洞,此现象证明了紫外线的长期照射侵蚀弱化了碳酸钙的性能。当紫外侵蚀试验中照射时长为1046h时,MICP矿化风沙土材料孔隙度变化率为23.6%;在核磁共振试验中,照射前试件的T2图谱呈多峰型,孔隙分布不均匀;试件的孔隙度随照射时间的延长而增大;随照射时间的增加,孔隙不断发育扩展,大孔隙逐渐减少,中孔隙逐渐增多,而小孔隙逐渐发育并与中型孔隙连接,大孔隙虽有残留,但大部分都转化为中型孔隙,材料的抗紫外侵蚀能力逐渐降低;孔隙主要分布在0.1~8μm,以半径为1μm的小孔隙为主。微生物矿化风沙土的紫外侵蚀研究为该技术在沙漠原位微生物覆膜的应用推广提供了基础研究和试验依据。

Based on the MICP technology and the aeolian sandy soil of Ulan Buh desert as geotechnical substrate materials,the ultraviolet erosion characteristics of mineralization aeolian sandy soil induced by MICP are studied.In addition,the total effective time of outdoor ultraviolet irradiation in winter in Ulan Buh desert area is equal to the total effective time of indoor ultraviolet irradiation,and the ultraviolet irradiation time of indoor UV-erosion tests is determined.Through the scanning electron microscopyand nuclear magnetic resonance technology,the pore characteristics of the mineralization samples are analyzed with the irradiation period under the same ultraviolet radiation intensity.The results show that after UV-erosion,the microscopic electron microscope scanning indicates the that the MICP-mineralized specimen has pores in the calcium carbonate crystal under the ultraviolet erosion for a long time,which proves that the long-term irradiation erosion of ultraviolet weakens the property of calcium carbonate.When the ultraviolet erosion time is 1046 h,the porosity rate of MICP-mineralized aeolian sandy soil is 23.6%.In the nuclear magnetic resonance(NMR)tests,the T2 spectra of the specimens before ultraviolet erosion have multiple peaks and the pore distribution is uneven.The porosity of the specimen increases with the increase of irradiation time.With the increase of irradiation time,the pores are developed and expanded constantly,the large pores were decrease and the medium-sized pores increase.However,the small pores gradually develop and connect with the medium-sized ones,although there are residual macropores,most of them are converted into medium-sized ones,and the ultraviolet erosionresistance of mineralization materials gradually decreases.The pores of the three specimens are mostly distributed in the range of 0.1~8μm,and the radius of small pores is mainly 1μm.The study of ultraviolet erosionof bio-mineralization Aeolian sandy soil in the laboratorymay provide a basic researchand favorable experimental basis for the application of this technique in the in-situ microbial crust of desert.