Abstract: Natural cementation is a typical characteristic of marine calcareous sediments, such as calcareous rock and soil, and the degree of cementation has an important influence on its mechanical properties. Due to the great heterogeneity and low cement strength of cemented calcareous sediments, it is difficult and expensive to obtain natural cemented calcareous sediments from the oceangoing island, limiting research on their physical and mechanical properties. To effectively solve the above problems, this paper attempted using physical, and biological dominate method in the laboratory. It was found that microbially induced carbonate precipitation (MICP) and enzyme induced carbonate precipitation (EICP) can promote the production of calcium carbonate crystals, generating artificially cemented specimens similar to the natural ones. The mineral composition, porosity and unconfined compressive strength of the biological artificially cemented specimens were analyzed by scanning electron microscopy (SEM), computed tomography scanned by X-ray (X-CT) and unconfined compressive strength test. The mineral composition and crystal morphology of the artificial cementation were the same with the natural cemented calcareous sediments. The peak unconfined compressive strength of the artificially cemented sample could reach to the level of the natural weakly cemented calcareous sediments. The relationship between cemented time, porosity, degree of cementation and unconfined compressive strength was quantitatively determined. Therefore, the biological dominate method can shorten the natural cementation process from tens of millions of years to a period that can be reproduced in the laboratory, providing scientific value for exploring the formation mechanism of naturally cemented calcareous sand and reef limestone. However, it should be noted that there are some limitations in artificially cemented specimens, such as the degree of cementation is not fully uniform and dolomitized calcareous rock cannot be simulated.

Key words: natural cementation of calcareous sediments, artificial cementation, crystal morphology, degree of cementation, stress-strain curve