Hydraulic properties calibration by high resolution monitoring data and 1D to 3D groundwater flow modeling of the Carozzo Landslide

<p>A reliable modeling of a landslide activation and reactivation requires a representative geological and engineering geological characterization of the affected materials. Beyond the material strength, landslide reactivation is sensitive to groundwater pressure distributions, that are generated by some external perturbation (recharge) and by the hydraulic properties of the materials. Drainage stabilization works generally involve drilling of a large number of drains and, therefore, minimize the total length is of primary concern to reduce the costs.</p><p>Aim of this work was the calibration of material properties for the optimization of drainage elements to be built for the slope stabilization and the construction of a shallow tunnel crossing a landslide. The case study is represented by the 4.0 · 10<sup>5</sup> m<sup>3</sup> Carozzo landslide (La Spezia, Liguria, Italy) which affects some marly and sandstone formation. During the tunnel excavation a monitoring network consisting of five DMS columns for displacements and piezometric head multilevel measurements was installed. The monitoring provided a series of piezometric head recession curves following some recharge events. The series of data generated in response of a unique perturbation (rainfall recharge event) were chosen to calibrate the material properties through a multi-step approach, starting from a 1D model and progressively approaching a complete 3D model.</p><p>The 1D simplified approach applies the solution by Troch et al. (2003) that considers a homogeneous landslide material, with constant slope and a progressive change in the slope width. In this model a storage function considers the amount of water stored in a slope section. By imposing the continuity equation and the Darcy law a second order of partial differential equation is solved by integration in space and time. By taking the initial conditions from piezometric measurements and assuming a constant rainfall recharge, the piezometric level and the outflow rate were computed and compared with the local piezometric level time history, by changing the hydraulic conductivity and the storage function value.</p><p>Successively, a groundwater flow FEM numerical model (in 2D and 3D) was developed considering the landslide geometry and internal zonation, including the presence of the excavated part of the tunnel. The model domain was divided into sub-zones according to the available geological surveys to account for internal variations of the material properties. The steady-state simulation of the water flow allowed to estimate the equivalent hydrogeological parameters of each subdomain. The hydraulic head distribution obtained under steady-state conditions was used as initial condition for the transient-state simulation. The recharge from precipitation was also included in the water balance by means of daily rainfall time-series. Finally, the model parameters were calibrated in transient state by comparing measured data and simulated results.</p><p>The minimum error between simulated and measured piezometric heads under transient conditions was obtained through the 3D configuration. Calibrated hydraulic conductivities in the 3D solution are up to an order of magnitude lower than the 1D solution because of the homogenous assumption of the model. The internal zonation of the landslide body and the modeling of a low-conductivity shear zone were essential to explain the pressure differences inside the body.</p>

Quantitative evaluation of soil functions: application to the data of the German Agricultural Soil Inventory

<p>The quantitative evaluation of the impact of agricultural management and climate change on soil functions is prerequisite for developing sustainable soil management. Soil functions are integral properties emerging from complex process interactions. They cannot be measured directly so that we need to rely on evaluation schemes based on indicators.</p><p>Vogel et al. (2019) developed a scheme to quantitatively evaluate soil functions which distinguishes between a soil’s potential and its actual state. They defined a soil’s potential to provide a soil function to be the maximum a soil can offer based on its inherent properties and site conditions while assuming that all soil properties that can be affected by soil management are in some optimum state within the limits of good agricultural practice. In contrast, a soil’s state is evaluated based on its manageable soil attributes. It can be applied to describe the room for improvement.</p><p>In this presentation, we apply the evaluation scheme by Vogel et al. (2019) at the scale of Germany using the data from the German Agricultural Soil Inventory (Jacobs et al., 2018; Poeplau et al., 2020). We use the data from more than 2200 soil profiles from arable sites and calculate indicators for potentials and actual states for the production function, the carbon storage function and the water storage function. For all functions, results show characteristic patterns which can be related to climatic and soil conditions but also provide evidence about the influence of agricultural management on soil functions. The results of this study may be used to analyze synergies and trade-offs between the various soil functions and to develop options for more sustainable soil management.</p><p> </p><p>References:</p><p>Jacobs, A., Flessa, H., Don, A., Heidkamp, A., Prietz, R., Dechow, R., et al. (2018). Landwirtschaftlich genutzte Böden in Deutschland - Ergebnisse der Bodenzustandserhebung. doi:10.3220/REP1542818391000.</p><p>Poeplau, C., Don, A., Flessa, H., Heidkamp, A., Jacobs, A., and Prietz, R. (2020). Erste Bodenzustandserhebung Landwirtschaft -- Kerndatensatz. doi:10.3220/DATA20200203151139.</p><p>Vogel, H.-J., Eberhardt, E., Franko, U., Lang, B., Ließ, M., Weller, U., et al. (2019). Quantitative Evaluation of Soil Functions: Potential and State. Front. Environ. Sci. 7, 164. doi:10.3389/fenvs.2019.00164.</p>