Li Gang, Zhang Yi-Jia, Hua Xue-Qing, Liu Jia, Liu Xing
Shaanxi Key Laboratory of Safety and Durability of Concrete Structures, Xijing University, Xi'an, 710123, Shaanxi, China.
Sci Rep. 2024 Sep 30;14(1):22745. doi: 10.1038/s41598-024-73986-5.
The cementation of desert aeolian sand is a key method to control land desertification and dust storms, so an economical, green and durable process to reach the binding between sand grains needs to be searched. The method based on the microbially induced calcite precipitation (MICP) appeared in recent years as a promising process that proved its efficiency. The feasibility of the MICP technique to treat aeolian sand composed by low clay content, fine particles, low water content and characterized by weak permeability was demonstrated in the present paper. The effects of initial dry density, cementation number and curing time on the permeability and strength of MICP-treated aeolian sand were investigated using permeability tests and unconfined compressive strength (UCS) tests. The microstructure of aeolian sand was observed by scanning electron microscopy (SEM) tests and X-ray diffraction (XRD), aiming to reveal the solidification principle of MICP. The tests result indicated that when the initial dry density and the cementation number rose, the hydraulic conductivity of aeolian sand decreased while the mechanical strength given by UCS values improved. When the initial dry density was 1.65 g/cm, the curing time was 3 h and the cementation number reached 20, the hydraulic conductivity and UCS reached 0.00151 cm/s and 1050.30 kPa, respectively. With increasing curing time, the hydraulic conductivity first decreased, followed by an increase, while the UCS exhibited an up and then a downtrend. Furthermore, the correlation between UCS values and the CaCO content reached a high R value equal to 0.912, which confirmed that the cementation occurred in sandy material and governed the soil strengthening. Indeed, the calcium carbonate crystals observed by SEM and XRD enhanced the friction between particles when they wrapped around the sand grains surface, while carbonates reduced the soil permeability when filling the pores and sticking the sand particles together. Finally, the theoretical and scientific knowledge brought by the present study should help in managing sand in desert areas.
沙漠风沙的胶结是控制土地沙漠化和沙尘暴的关键方法，因此需要探寻一种经济、绿色且持久的方法来实现沙粒之间的粘结。基于微生物诱导碳酸钙沉淀（MICP）的方法近年来作为一种行之有效的方法崭露头角。本文论证了MICP技术处理低粘土含量、细颗粒、低含水量且渗透性弱的风沙的可行性。通过渗透试验和无侧限抗压强度（UCS）试验，研究了初始干密度、胶结系数和养护时间对MICP处理风沙的渗透性和强度的影响。通过扫描电子显微镜（SEM）试验和X射线衍射（XRD）观察风沙的微观结构，旨在揭示MICP的固化原理。试验结果表明，随着初始干密度和胶结系数的增加，风沙的水力传导率降低，而UCS值给出的力学强度提高。当初始干密度为1.65 g/cm，养护时间为3 h且胶结系数达到20时，水力传导率和UCS分别达到0.00151 cm/s和1050.30 kPa。随着养护时间的增加，水力传导率先降低，随后升高，而UCS呈现先上升后下降的趋势。此外，UCS值与CaCO含量之间的相关性达到了高达0.912的R值，这证实了在砂质材料中发生了胶结并控制了土壤强化。实际上，通过SEM和XRD观察到的碳酸钙晶体在包裹砂粒表面时增强了颗粒之间的摩擦力，而碳酸盐在填充孔隙并将砂粒粘结在一起时降低了土壤渗透性。最后，本研究带来的理论和科学知识应有助于沙漠地区的沙地治理。
