Numerical analyses of embankment dams containing plastic concrete cut-off walls using finite difference method (A case study: The Karkheh Embankment Dam)

In this paper, numerical analyses have been performed on the Karkheh embankment dam with a clayey core and plastic concrete cut-off wall during construction, impounding, and permanent seepage stages. The dam has 127 meters height and is located in a high seismic hazard zone in Iran. Different stages of construction, water impounding, and steady state seepage were modelled and analyzed using the hyperbolic and Mohr-Coulomb models with the two dimensional finite difference method (FDM). So, nonlinear analyses were performed using FLAC 2D to investigate the settlements and the pore water pressure changes in different zones of the dam during above-mentioned stages and the results were compared to those of the other studies. The results show that at the end of the construction stage, the maximum settlement equal to 1.45m occurs inside the clay core at the height of 65m. Then, after impounding of the reservoir and steady state stage, the maximum magnitude of the horizontal deformations occurs in the downstream of the dam equal to 0.55m; however, these magnitudes reach to 0.17m at the crest of the dam. Moreover, it was shown that the maximum horizontal displacement of the plastic concrete cut-off wall has happened at the top of the wall in the clay core which is in a good agreement with the other studies’ result.

Thermoluminescence Analysis of the Clay Core of Bronze Statues: A Re-Appraisal of the Case Studies of Lupa Capitolina and Other Masterpieces in Rome

In this work, we present some new results in applying thermoluminescence (TL) dating to the clay core of bronze statues. This is very important, due to the impossibility of directly dating a metal. Very few cases of indirect dating of clay cores by TL are reported in the literature. We re-considered three cases of dating of clay core from important bronzes in Rome. The parameters to be considered were not easy to calculate in the case of the Lupa Capitolina. However, its traditionally reported Etruscan origin is definitely ruled out, even if the accuracy in the dating is too low to precisely propose a date of the casting. The comparison with radiocarbon results shows good agreement for a Medieval dating. Two other bronze statues were analysed in order to date their casting by TL; a horse from Musei Capitolini resulted to have been cast in the Greek classical period, excluding its casting in the Rome imperial period. A third study shows that, in particularly favourable situations, TL dating of clay core can give rather precise results. This is the case where in the clay core are present materials that behave like good dosimeters, as generally happens in dating ceramics. Furthermore, the possibility of measuring all the parameters influencing the calculation of the dose rate is essential; both the external radiation sources and the radiation reduction by the water content must be taken into account. This was the case of Saint Peter in the Vatican that turned out to be a cast from the beginning of the XIV century.

Heat and water fluxmodeling in an earth dam

This study aims to identify the water flux in an earth dam using heat flux due to convection. Sixteen earth dams model was constructed in a hydraulic flume by varyinggeometrical and flow input parameters to identify heat and water flux.Homogeneous as well was earth dam with the clay core was built-in a hydraulic flume. Temperature measurements were doneto calculate heat flux in the experimental model. A finite element model of the earth dam using Seep/w was developed to obtain water flux,while temp/wwas to obtain heat flux. These results were used as input in Temp/w and Seep/w in Geostudio 2020. Significant reduction of the heat and water fluxwas seen while comparing the homogeneous models with central impervious core models. An increase in the heat and water flux was observed on increasing the downstream filter's length, longitudinal slope,and vice versa with the upstream slope and the thickness of the clay core. Comparing fluxesina homogeneous dam model (model 1) with the clay core model (model 9) with top width 2.4 m and bottom width 18 m in model 9, both water flux and heat flux were reduced78.46%. While comparing it with model 10, with bottom core width of 18 m and top core width of 1.9 m, both water flux and heat flux reduced by 77.72%. Heat flux measurements were found a valuable alternative to detecting water flux and seepage in an earth dam at a reduced cost.

Numerical Analysis of Rapid Drawdown of an Embankment Dam

Numerical analysis for the safe rate determination of lowering of an embankment dam was performed in this study with the use of the finite element method. Coupled deformation and consolidation analysis were carried out for staged construction and drawdown of a 59m embankment dam for varying undrained shear strength of the clay core. The lowering of the reservoir was performed at different depths between two extreme scenarios, i.e. rapid lowering rate (1m/day) and slow lowering rate (0.1m/day). The reservoir of the dam was lowered to a depth from 10m to 55m in gradual increments. The results indicated that the safety of the dam was satisfactory when the reservoir was lowered at the quick rate for a depth of 10m, 20m, 30m respectively when the undrained shear strength of the clay core was taken as 20, 25 and 30kN/m2. Regarding the case of slow drawdown rate of the reservoir, it was found that the reservoir could be lowered up to a depth of 55m at a rate of 0.1m/day when the undrained strength of clay core was 25kN/m2. The stability of the dam was also found satisfactory even though the reservoir was lowered at a rate of 0.25m/day for a depth of 55m when the undrained shear strength of clay core was 30kN/m2.

Characterization of the leakage problem in Salhab earthen dam using electrical resistivity tomography and SP measurements, Syria

The earthen dam of Salhab is located in the southern margins of Al-Ghab plain at 3–4km of Salhab town northern-west of Syria. The dam consists of two separated embankments: the main one extends east-west along a distance of 895 m with 14.5 m height, while the second embankment towards northwest-southeast over a distance of 510 m and 11 m of height. The dam crest has a constant topographic elevation of 220 m above sea level (a.s.l). Electrical Resistivity Tomography surveys (ERT) combined with a Self-Potential measurements (SP), were implemented at the upstream and at the top of the main and the secondary embankments of the dam in order to identify the possible leakage zones under the dam’s body. The interpretation of the ERT sections and the SP measurements, carried out at the upstream side, revealed a distinct zone of leakage extending along the beginning and the end parts under the main embankment. Moreover, many punctual anomalous spots of low resistivity values were recognized within the dam’s clay core. One of those spots was confirmed by the implementation of a detailed ERT profile and by a piezometric borehole drilled at the top of the dam. Whereas, the clay core of the secondary embankment seems relatively coherent and homogeneous as well as a trace of a tectonic fault was identified under the end part of the embankment body but no manifestations of leakage were observed under and behind the secondary dam body.