Study on Microstructure of Cemented Organic Soil in Dianchi Lake, China

Abstract

The organic soil in the Dianchi Lake area contains much humic acid (HA), and the impact of HA on cemented soil has attracted much attention. In this study, test soil is prepared based on the actual HA content of the soil in Dianchi Lake, and cement is added to prepare samples. Unconfined compressive strength (UCS), scanning electron microscopy (SEM), energy-dispersive analysis (EDS), and X-ray diffraction (XRD) tests are conducted on the samples. The strength development and microstructure changes of cemented organic soil are studied. The results show that (1) cemented soil strength decreases with the increase in HA content and increases with the cement mixing ratio; (2) SEM and EDS tests show that with the increase in HA content, the connection between soil particles gradually changed from surface–surface to point–surface, point–edge, or point–point connection. A large overhead structure is inside the cemented soil, and its integrity weakens with increased HA content. However, elements such as Ca, Si, and Al exist in the pores of cemented soil, indicating that cement hydration products are cemented between soil particles. XRD testing shows that with the increase in HA content, the intensity of the diffraction peaks of hydration products in cemented soil gradually decrease. (3) In general, HA will gradually deteriorate the integrity of cemented soil and reduce its strength. When the HA content is more than 15%, the effect of HA on strength is more prominent. However, increasing the cement mixing ratio can effectively weaken HA’s negative effect on cemented soil’s strength. When the cement mixing ratio is between 15% and 25%, the strength of cemented soil with high HA content can be effectively increased. However, this approach is not conducive to the protection of the environment.