Phreatic Surface Estimation In MSE Wall With Geocomposite Back Drainage

This study proposes a simple mathematic model for approximating the level of phreatic surface inside the protected zone in mechanical stabilized earth wall with back drain installation though the position of phreatic surface at the drainage interface (ho) which reflects the maximum level of phreatic surface in the protected zone. The proposed model was established based on dataset taken from 180 simulation cases caried out in Plaxis environment. Regression results present a combination of significant effects and major role to maximum water level in the protected zone (ho) of a ratio of length from upstream water to the drainage face to the wall height (L/H), a soil permeabilities coefficient (k) and a transmissivity of the drainage material (Tnet). The proposed model can facilitate design of drainage material to achieve desired level of phreatic surface in the protected zone.

Dewatering System Control by MATLAB Software

The aim was to design a MATLAB program to calculate the phreatic surface of the multi-well system and present the graphical shape of the water table drawdown induced by water extraction. Dupuit’s assumption is the base for representing the dewatering curve. The program will offer the volume of water to be extracted, the total number of wells, and the spacing between them as well as the expected settlement of soil surrounding the dewatering foundation pit. The dewatering well arrangement is required in execution works, and it needs more attention due to the settlement produced from increasing effective stress.

Dam Safety: Monitoring of Tailings Dams and Safety Reviews

The awareness to tailings dam safety monitoring and reviews has increased by the catastrophes resulting from failures of such dams worsened by increasing tailings waste and construction of larger dams. The losses born by the mining industry from high costs of compensations and environmental rehabilitation work have brought this matter into focus. In the present article the need for safety monitoring programs of tailings dam is highlighted and mode of failures and factors leading to them are described. Basic principles of such programs are investigated with all phenomena needing observation described and their impacts explained. As in conventional dams this work is carried out by visual inspections and use of similar methods and instruments. In similar manners in both types of dams’ observation and measurements are done for measuring seepage water quantity and quality, phreatic surface level and pore pressure and total earth pressure values in addition to deformation measurements; and all are done by similar devices and methods such as weirs, piezometers, inclinometers, settlement plates and geodetic surveying. Basic differences between safety monitoring systems of the two types of dam, however, are presented in a tabular form. The continuity of safety monitoring of tailings dams is emphasized not only during the long construction phase but also after that in the abandonment and closure phase which can last indefinitely in order to watch for possible adverse effects on the environment and ecosystem due to the winds eroding and carrying of poisonous tailings contents, in addition to contaminated seepage water entering surface water streams and ground water. Justifications for using real time monitoring systems for recording and transmitting all data to the control center are presented with emphasis given on savings in both labor and time and need for the discovery of warning signs enabling raising earlier the alarm of possible failure or incident and the early taking of preventive measures. In this article it is argued that, in spite of the large investment of installing and running cost of comprehensive dam safety monitoring systems in tailings dams, such costs are justified as they form only a small percentage of the total investment in the tailings facilities projects, and may save huge costs if failure does happen. Such systems may be considered as an additional insurance against such events.

Assessment of Groundwater Contamination by Terbuthylazine Using Vadose Zone Numerical Models. Case Study of Valencia Province (Spain)

Terbuthylazine is commonly used as an herbicide to control weeds and prevent non-desirable grow of algae, fungi and bacteria in many agricultural applications. Despite its highly negative effects on human health, environmental modeling of this kind of pesticide in the vadose zone till reaching groundwater is still not being done on a regular basis. This work shows results obtained by two mathematical models (PESTAN and PRZM-GW) to explain terbuthylazine behavior in the non-saturated zone of a vertical soil column. One of the models use a one-dimensional analytical formulation to simulate the movement of terbuthylazine through the non-saturated soil to the phreatic surface. The second and more complex model uses a whole set of parameters to solve a modified version of the mass transport equation considering the combined effect of advection, dispersion and reactive transport processes. Both models have been applied as a case-study on a particular location in South Valencia Aquifer (Spain). A whole set of simulation scenarios have been designed to perform a parameter sensitivity analysis. Despite both models leading to terbuthylazine’s concentration values, numerical simulations show that PRZM-GW is able to reproduce concentration observations leading to much more accurately results than those obtained using PESTAN.

Characterization of heterogeneous landfill: seismic waveform inversion and wavefield retrieval to integrated quantitative inversion of high-resolution seismic-electrical datasets

<p>A landfill body is typically highly heterogeneous. The scale of these heterogeneities - which are relevant for the purpose of assessment of preferential flow paths, the degradation processes, and the spatio-temporally varying aging and settlements - is quite often small considering the limiting resolution and confidence of the prevalent near-surface geophysical methods. High-density areas act as obstruction to fluid flow and are important for understanding the degradation processes. These areas manifest as scatterers in the recorded seismic wavefield. Strong presence of scattered energy is typical of seismic datasets acquired on landfills. Our research has been concentrated on resolving and monitoring density and porosity variations, as well as distribution of water saturation, phreatic surface, matric suction and stress. Dedicated schemes of early-arrival waveform tomography, full-waveform inversion and interferometric seismic wavefield retrieval complemented by electrical resistivity tomography show promise in high-resolution delineation and monitoring of these properties in a heterogeneous landfill. We will discuss the results of a novel inversion scheme which allows quantitative estimation of spatio-temporally heterogeneous matric suction, stress and porosity.</p>

National scale climate change impact assessment – investigating long-term variations in the climate change signal for groundwater levels across geologies and aquifers

<p>The effect of climate change on groundwater system is still not extensively understood. Studies often focuses on changes in recharge to the groundwater system but rarely investigate the resulting impacts on hydraulic head levels especially the spatial distribution of the change across larger domains.</p><p>Only few countries in the world have access to a detailed national hydrological model, and fewer still have done nationwide climate change assessments. This study applies a combination of the newest updated national hydrological model for the entire Denmark (the DK-model 2019, http://dk.vandmodel.dk/in-english/) and 20 climate model projections from the Euro-Cordex project (Jacob et al., 2014) for the RCP4.5 and the RCP8.5 emission scenario (4 and 16 runs respectively). The climate dataset are bias-corrected for the Danish area using double Gamma distribution-based scaling for temperature and precipitation (Pasten-Zapata et al., 2019).</p><p>This large dataset is used to evaluate the distribution of the magnitude and direction of changes with special focus on the phreatic surface and the main water-bearing groundwater layers for drinking water consumption in Denmark. The spatial variations in the near-surface impact signal across the entire country is also analyzed, as different Quaternary geology is represented from sandy layers in the west to moraine clay tills in the east and marine sand and clay to the north. The climate dataset is a successive time series from 1970ties to the end of the century and thus also enables an analysis of long-term changes in the state of the groundwater system and aquifers. </p><p> </p><p> </p><p>Jacob, D., Petersen, J., Eggert, B., Alias, A., Christensen, O. B., Bouwer, L. M., Braun, A., Colette, A., Déqué, M., Georgievski, G., Georgopoulou, E., Gobiet, A., Menut, L., Nikulin, G., Haensler, A., Hempelmann, N., Jones, C., Keuler, K., Kovats, S., Kröner, N., Kotlarski, S., Kriegsmann, A., Martin, E., van Meijgaard, E., Moseley, C., Pfeifer, S., Preuschmann, S., Radermacher, C., Radtke, K., Rechid, D., Rounsevell, M., Samuelsson, P., Somot, S., Soussana, J.-F., Teichmann, C., Valentini, R., Vautard, R., Weber, B., and Yiou, P.: EURO-CORDEX: new high-resolution climate change projections for European impact research, Regional Environmental Change, 14, 563-578, 10.1007/s10113-013-0499-2, 2014.</p><p>Pasten-Zapata, E., Sonnenborg, T. O., and Refsgaard, J. C.: Climate change: Sources of uncertainty in precipitation and temperature projections for Denmark, Geological Survey of Denmark and Greenland Bulletin 43, e2019430102-2019430101-e2019430102-2019430106, https://doi.org/10.34194/GEUSB-201943-01-02 2019.</p><p> </p>

The Application of the Seismic Cone Penetration Test (SCPTU) in Tailings Water Conditions Monitoring

The safe operation of the large, outflow Tailings Storage Facilities (TSF) requires comprehensive and continuous threat monitoring. One of the basic kinds of threat monitoring is to monitor the water conditions in deposited tailings, which is usually carried out using a conventional piezometric observation method from a network of installed piezometers. In complex tailings storage conditions, the reliability of the piezometric method may be questioned. The Seismic Cone Penetration Test (SCPTU) can meet high test standards. The results of the penetration tests closely identify conditions of sediments that determine the tailings water regime verified locally on the basis of pore water pressure dissipation tests. On the other hand, seismic measurements perfectly complement the characteristics of sediments in terms of their saturation. The analysis of the results of SCPTU implemented in the tailings massif also showed that below the phreatic surface, a zone of not fully saturated tailings can be found. Its presence improves the stability conditions of the tailings massif and dams, but also limits the possibility of the static liquefaction of tailings.