# Dynamic Properties of Calcareous Sands from Urban Areas of Abu Dhabi
## 5 Conclusions  
ABD has developed its own national building code that requires a dynamic analysis of structures for seismic loadings. Although low-strain dynamic properties of in situ sand deposits that are rich in carbonate minerals are available, no study has presented the degradation models of the dynamic properties for in situ undisturbed soil samples for ABD. This study presented the results of dynamic testing on undisturbed soil samples taken from different sites of urban ABD. Bender element (BE) and cyclic triaxial (CT) tests were performed for low-strain and large-strain characterization of calcareous sand deposits within urban ABD. The results were curve-fitted with power and hyperbolic models and then compared with studies on selected calcareous and silica sands from the literature. The main conclusions from the present study are presented in the following.  
* The rate of increase in Vs with confinement for carbonate sands varied significantly and strongly depended on the sand matrix and its inclusions. The presence of cementation, seashells, and other minerals such as gypsum caused large variability among the samples. Low-strain values of Vs and its variation with confinement must be evaluated on a case-by-case basis.
* The large strain behavior (degradation of dynamic properties) was similar for all tested sand samples at equivalent confinements, irrespective of their spatial distribution in ABD. The degradation models presented in this study can therefore be used for dynamic analysis of the structures under seismic loading or site response analysis. The rate of degradation for calcareous sands tested in the present study was larger than for silica-based sands.
* The rate of degradation of dynamic properties in undisturbed samples of calcareous sands was smaller in comparison to previous studies on calcareous sands. A larger degradation in previous studies, especially at mid-strains, was mainly attributed to the remolding of samples, which can disturb the cementation at inter-particle contacts. At very large strains however, the comparisons converged.  
Figure 8: Comparison of proposed degradation models from the study by [PERSON] et al. [9] on calcareous sand at Confinement (o) = 40 kPa from resonant column (RC) testing.  
* The damping ratios of the tested samples were larger for the smaller strains in comparison to the previous studies due to a different testing device (RC), larger localized strains, and the presence of gypsum. At larger strains however, the tested samples in the present study indicate damping ratios that are smaller than other studies on similar sands.  
Conceptualization, Z.H.K., A.K. and M.A.; methodology, Z.H.K., A.K. and K.F.; software, A.K.; validation, Z.H.K., M.A. and K.F.; formal analysis, A.K. and Z.H.K.; investigation, Z.H.K. and A.K.; resources, M.A., Z.H.K., M.E.E. and K.F.; data curation, Z.H.K., A.K. and M.A.; writing--original draft preparation, A.K. and Z.H.K.; writing--review and editing, Z.H.K., M.A. and K.F.; visualization, A.K., Z.H.K. and M.A.; supervision, Z.H.K., M.A., M.E.E. and K.F.; project administration, Z.H.K.; funding acquisition, Z.H.K., M.A. and M.E.E. All authors have read and agreed to the published version of the manuscript.  
This research was funded by The American University of Sharjah, grant number FRG19-M-E08. The work in this paper was supported, in part, by the Open Access Program from the American University of Sharjah.  
Not applicable.  
The authors would like to acknowledge the support of machine shop at the American University of Sharjah for the manufacturing of extraction tools for the samples.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. This paper represents the opinions of the author(s) and does not mean to represent the position or opinions of the American University of Sharjah.