# Repairing Damage Caused by Burrowing Animals in Embarnkments: A Sustainable Proposal
## 1 Introduction  
The presence of badgers, porcupines, and foxes in the proximity of earthen embankments causes the dig of tunnels and holes inside these structures (see Figure 0(a)) and result in altering external and internal geometry with different impact on their hydraulic performance and structural integrity. Landslide disaster risk might accordingly increase. Animal burrowing and possible interventions have not been sufficiently under the attention of the scientific literature for a long time. The relatively recent trend of wildlife and parks regulations, which aim to safeguard the huge natural heritage, might have allowed the spread of animal life close to human settlements, such as embankments, and the consequent damage to earthen structures with the concern about interventions. Indeed, if ignored, animal burrowing can be a cause of a flood defence breaching and consequences can be disastrous, as shown in Figure 0(b) for the leveee failure that occurred along the Secchia Riverin Italy [1]. Attention among levee management boards and maintenance agencies, such as the AIPo (Italian acronym for the Interregional Agency for the Po River embankments), has then increased because of the alarming concern on the hydraulic performance and on the structural integrity of levees and earthen dams along the river and its tributaries. Possible types of levee deterioration due to wildlife activities can be categorized into three main categories: structural damage, surface erosion and hydraulic alterations [2; 3]. From the management point of view, the damage requires subsequent and quick repair to avoid adverse consequences to earthen structures, which would be then vulnerable and no longer characterised by homogeneous permeability, mechanical and volume stability, internal and external erosion resistance [4]. Hence, when animal macro-pores result from the monitoring activities, sustainable interventions need to be taken as soon as possible to prevent any damage to the earthen structure [5; 6]. A census study [7] that was carried out by the AIPo and the University of Brescia highlighted that the most adopted engineering interventions refer to two engineering activities: the excavation of the area around the hole with the following backfill and/or the injection of a low pressure flowable group, such as cement and bentonite mixes or polyurethane foam. As suggested by the International Levee Handbook [8], the first solution, although economically advantageous and sustainable, involves the weakening of the embankment because of the different compaction of the new material--compared to the in situ compacted one--and the uncertainty of the complete filling because of the length and complexity of the animal burrow net. As for the second intervention, this consists of injections at low pressure of grouts, which more likely go upward to fill all voids. However, grouting mixture shrinkage and the interface between the grout and the existing soil may create an additional seepage path and piping may be encouraged. Therefore, the different characteristics of permeability, strength, and stiffness of the two materials (existing soil and injected mixture) is a concern for the levee body continuity and for the sustainability requirements. Soil stabilization with lime is a technique commonly used in earthworks, considered as a sustainable solution (e.g., [9]). It is mainly used for soils that contain high clay minerals (e.g., [10]) determining flocculation, a consequent change in grain size distribution and an increase of the soil strength and stiffness (e.g., [11; 12]). Due to lime, chemical reactions able to form compounds with cementitious properties can also occur in pyroclastic soils such as natural pozzolanas (e.g., [13]). They can improve erosion and mechanical characteristics in the embankment and hydraulic structures made of coarse soil such as sand (e.g., [14]), clayey sand (e.g., [15; 16]), silty soil (e.g., [17]), or silts [18].