# Repairing Damage Caused by Burrowing Animals in Embarnkments: A Sustainable Proposal
## 4 Discussion  
Data reported in this work show that the increment of stiffness under one-dimensional loading for samples treated with lime is probably affected by the formation of hydrated secondary phases (e.g., [12]). Even if this influence is more evident in clayey soils, this research has demonstrated that this is observable also for the coarser silty sand or sandy silts, that are affected by animal burrowing as detected so far by the AlPo monitoring along the Po River embankment net. Hence, this research is a preliminary study on lime treatment as a possible solution for repairing embankments made of soils within the typical grading range of the Po River and within its geological environment. The compression behaviour of raw and lime treated samples of the three soils of Po River embankments showed a clear trend: lime treatment determines a new fabric and a different mechanical behaviour which results in an increment of stiffness, even for coarser soils. The initial new structure [24] formed with lime treatment (i.e., lime bonds), can be considered as an internal state variable in addition to specific volume in controlling the mechanical response. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Soil** & **CF\%** & **Tests** & **e\({}_{0}\) **\(\bullet\)** & **\(\Delta\)e/e\({}_{0}\) **\(\bullet\)** \\ \hline Casale M. & 2.5 & O3-OL12/7 & 0.862 & 0.11 \\ [PERSON] & 27.5 & O7-OL15/9 & 1.263 & 0.29 \\ [PERSON]. & 29 & O10-OL16/24 & 1.318 & 0.21 \\ \hline \hline \end{tabular}  
* * Measures were corrected assuming the same e\({}_{0}\) for each couple of tests with similar e\({}_{0}\).  
\end{table} 
Table 4: Effect of lime treatment on compressibility according to the amount of fines. Figure 10: Coefficient of consolidation Cv as a function of clay fraction CF(%). This work has also demonstrated that, if the compression path of a line treated sample with higher porosity is compared to the one of a denser raw sample, stiffness can reach a similar value. This circumstance makes it possible to suppose that a looser mixture of treated soil that is pushed into a burrow would have a similar stiffness (and strength and/or permeability) to that of a soil compacted in situ. Interface problems occurring with high stiffness injections of the commonly used bentonite-cement mixtures can be then prevented. Similarly, the weakening of the embankments due to the destruction/construction of a part of them and the uncertainty of the continuity of the levee body caused by the excavation of the area around the hole and the backfill compaction in situ adjacent to the pre-existing embankment can be overcome. Then, the possibility of a further solution that can be a good compromise among the two more frequent interventions adopted by AIPo, can be taken into account in order to avoid discontinuity problems and interface erosion preserving the continuity of mechanical and hydraulic characteristics and, at the same time, avoiding the weakening of embankments. In other words, lime treatment can improve the mechanical behaviour so that the backfilled soil can be similar, in terms of hydraulic and mechanical behaviour, to the pre-existing compacted soil and, hence, stronger and stiffer than the loose soil normally inserted to \"plug\" the hole left from an animal burrow in the destruction/construction solution. Future research is mandatory to assess a quantification of the benefit of lime treatment on the formation of the hydrated secondary phases for soils from the Po River earthworks. In detail, the influence of lime percentage, time of curing, long-term response, particle size distribution, featuring mineralogy, and water content need to be investigated for these embankment soils to be aware of their effects not only on compressibility but also on saturated permeability and drained and undrained strengths. Being that the injected treated soil mixtures feature low viscosity, an analysis of shrinkage side effects needs to be undertaken so that this sustainable technical procedure in situ can be adopted.