# Repairing Damage Caused by Burrowing Animals in Embarnkments: A Sustainable Proposal
## 2 Materials and Methods  
Animal burrowing concerns often a specific particle size distribution range (see typical grading of soils involved in burrowing phenomena on Figure 3 [7]) and, for this study, three soils within that range were investigated. Their particle size distributions are shown in Figure 3. Soils were taken from the Po River embankments in Casale Monferrato (AL), in Monticelli d'Ongina (PC) and from a Po River tributary in Remedello (BS). The collected soils were then crushed in a mortar until passing the sieve 850 \(\mu\)m and over-dried for 24 h at 105 \({}^{\circ}\)C. Gradings of the three soils tested were measured using wet sieving and sedimentation, but with a deflocculant in this case. Afterberg limits were measured according to standard procedures: the Casagrande method for the liquid limit and the thread rolling until crumbs occur for the plastic limit. Classification of soils was determined according to the British Standard for site investigation (BS 5930) and the AASHTO-CNR_UNI 10006. Figure 2: Proposal (**a**) compressibility for raw and treated soil vs dry unit weight; (**b**) compaction curves according to different energies for raw and treated samples. Treated specimens were obtained by adding dry powder of hydrated lime (calcium hydroxide Ca(OH)2) supplied by GROTECH-Kalkwasser company that was mixed to the raw material in a proportion of the ideal percentage of lime by dry weight of soil. The percentage of lime was chosen on the basis of ICL measurements (Initial Consumption of Lime [22]) carried out on soil-lime-water mixtures created using 5 different soils from the Po River embankments within the typical grading range shown in Figure 3.  
Clay fraction percentages CF%, for the three gradings are given in Table 1, along with Atterberg limits, plasticity index and soil classification. Note that if gradings were estimated on soil passing 850 \(\upmu\)m, Atterberg limit tests were carried out on soil passing 425 \(\upmu\)m. The mean value of specific gravity, Gs, equal to 2.70, was based on an average of the values reported on similar soils [23] while for hydrated lime the value of Gs equal to 2.3 was considered. According to the plasticity classification for the three soils passing the 425 \(\upmu\)m and the representation of the British System (BS1377-2 1990) Casale Monferrato 425 \(\upmu\)m passing soil is a silt of low plasticity (ML), Remedello's is a silt of medium plasticity (MI) and Monticelli d'Ongina's is a silt of high plasticity (MH). Obtained values are shown in Table 1 and Figure 4.  
In order to quantify the best percentage of lime for the treatment, the standard ICL test was carried out, varying the percentage of lime. The pH was measured after one hour of curing by means of the 826 pH Mobile, featured by a measuring resolution of 0.001 pH. Furthermore, for the Remedello samples, the pH values were monitored over 14 days. In the measurements, values of pH equal (or higher) to 12,4 correspond to the pH of a lime saturated solution in which lime is still available for pozzolanic reactions. To perform the ICL test, according to the procedure [22], mixtures were prepared by taking 100 mL of water, 25 g of dry soil added with dry hydrated lime at the considered percentages (2%, 3%, 4%, 5%, 6% of the dry weight of soil). \begin{table}
\begin{tabular}{c c c c c c} \hline
**Soil** & **CF \%** & \(\mathbf{w_{L}}\) & \(\mathbf{w_{P}}\) & \(\mathbf{I_{p}}\) & **BS 5930** & **AASHTO** \\ \hline Casale M. & 2.5 & 24.16 & 22.86 & 1.30 & Slightly clayey, very silty sand & A-2-4 \\ Remedello & 27.5 & 40.81 & 26.59 & 14.22 & Very clayey and very sandy silt & A-7-6 \\ Monticelli D. & 29.5 & 47.78 & 31.55 & 16.23 & Very clayey and sandy silt & A-7-5 \\ \hline \end{tabular}
\end{table} 
Table 1: Properties of soils and classification. Figure 3: Particle size distribution and typical grading range for Po river embankments damaged by animal burrowing [7].