Dam safety is critical for protecting downstream lives, property, ecosystems, and socio-economic stability. Investigating dam breach mechanisms and establishing safety warning thresholds hold significant scientific and practical value. This study conducted dam breach model tests under diverse conditions and developed a monitoring and warning system using high-precision inclinometers to elucidate deformation characteristics and failure mechanisms. Experimental results revealed three distinct failure stages: tension cracking, localized soil flow/collapse, and catastrophic collapse/landsliding. Precursor phenomena such as seepage and cracking were observed prior to soil flow failure, suggesting that rapid infiltration line reduction during this phase could mitigate large-scale failures. Tilting deformation of the downstream slope was identified as a viable early warning indicator. An improved tangent angle method subdivided the rapid deformation stage into three substages (early, middle, and late) using thresholds of 45 degrees, 80 degrees, and 85 degrees, respectively, to establish tiered warning criteria. Additionally, a reciprocal velocity method was proposed to predict breach timing by characterizing the relationship between the inverse rate of slope angle change and time, demonstrating effective breach time prediction.

The investigation of river levees holds significant implications for mitigating flood damage. Sand boiling, backward erosion piping, and phenomena manifesting along the riverside of levees directly imperil the integrity of these structures. It is imperative to address these phenomena comprehensively to safeguard both lives and property amidst flood events. The principal aim of this research is to delineate the variances in geotechnical conditions between sand boils observed at slope toes on the landside and those occurring at a distance from this region along the levee. Therefore, this study conducted extensive boring investigations at sites where sand boils occurred. The soil samples sampled from the boring investigations were analysed for grain size. The results of a series of geotechnical investigations showed that in the cases where sand boils occurred near the toe of the slope, a series of sandy soils with grain size characteristics similar to those of the sand boils were deposited in the foundation of the levee. On the other hand, in the case where the sand boil occurred far from the toe of the slope, sandy soil with grain size characteristics similar to that of the sand boil was deposited only on the landside.

Many earth dams are damaged by shearing under seismic stresses effect. In Algeria, earthquake of 21 May 2003, of magnitude Mm = 6.9 on Richter scale, considered as the most violent for more than 20 years, occurred about 70 km east of Algiers's capital, where a large number of structures were damaged in this region. The aim of this article is to present a numerical analysis of an earth dam in the province of Oum-Elboughi. The objective is to show the influence of compressive seismic waves and the effect of foundation deph on dam behavior .The stady was carried out using a 2D finite difference method (FDM) using the FLAC 2D calculation code. In this analysis, a soil nonlinear behaviour is provided by a combined Hardin/Drnevich hysteretic damping behaviour model with Mohr-Coulomb elasto-plastic model. Results that are presented in terms of deformations and shear stresses developed at the dam and dam foundation show that the most critical area is located on the downstream side of the dam. Increasing the foundation depth decreases the value of horizontal stress, while decreasing it increases the dam instability risk.

Aging and heavy rainfall can cause earth dams to undergo failure, which involves large displacements. Due to mesh distortion, however, the finite element method (FEM) is unsuitable for analyzing such large displacements. As an alternative, the material point method (MPM) ensures accurate simulation of large displacements, without the need for remeshing. This study uses MPM to investigate the post-failure behaviors of earth dams with various geometries and under different rainfall intensities. The MPM results are validated by comparing the MPM-derived pore water pressure with FEM-derived values for the same model, and a close alignment is confirmed. Different failure patterns are observed depending on the geometry and rainfall intensity. Under high water levels and rainfall conditions, the distributions and evolutions of the displacements and deviatoric strain are initially concentrated at the dam toe and gradually propagated from the downstream slope toe to the dam crest. Conversely, the distribution of pore water pressure remains relatively constant under high water levels, while rapid changes are observed under rainfall conditions. The runout distance, crest settlement, and sliding volume increase with increasing dam height, decreasing slope ratio, and increasing rainfall intensity. Therefore, MPM can be used as a promising tool for evaluating the entire failure mechanisms and post-failure behaviors of unsaturated earth dams.

Seepage flow through complex foundations is one of the main factors causing dam failure. To foresee this problem, seepage modeling and analysis are usually performed. This study investigated seepage behavior as affected by complex, foliated, rock foundations in an earth dam. The PLAXIS 3-D LE software was used to analyze seepage problems for steady state flow. The normal high-water level (NHWL) with anisotropic permeability was considered in the models. The anisotropic permeability of foliated rocks was determined according to the angle of inclination. The flow characteristics along the dam axis could be divided into five zones, with three zones for the middle parts (MD1, MD2 and MD3) and one zones for each of the two abutments (LA and RA). The quantities of flow (water transmissibility) upstream to downstream (QX) on each zone highly depended on the geological structures. Although the average seepage transmissibility values of the residual soil and phyllite were almost equal for every zone. The values in the anticline areas were higher than for the syncline areas, especially for the middle zones. The flow tended to transfer from residual soil into phyllite rock in the anticline area. The transmissibility ratio of anticline to syncline was more than 2 times for both the residual soil and phyllite. The finger drain and river channel attracted substantial flow in the longitudinal (QY) and vertical (QZ) directions. However, the verification of the field piezometric versus the modeling heads showed the possibility of blockage of the finger drain.

The S-wave velocity (Vs) is a valuable parameter for assessing the mechanical properties of subsurface materials for geotechnical purposes. Seismic surface wave methods have become prominent for estimating near-surface Vs models. Researchers have proposed methods based on passive seismic signals as efficient alternatives to enhance depth of investigation, lateral resolution and reduce field effort. This study presents the Multichannel Analysis of Surface Waves (MASW) utilizing Common Virtual Source Gathers (CVSGs) derived from seismic ambient noise cross-correlations, based on Ambient Noise Seismic Interferometry concepts. The method is applied to passive data acquired with an array of receivers at the Paranoa earth dam in Brasilia, Brazil, to construct a pseudo-2D Vs image of the massif for interpretation. Our findings showcase the adopted processing flow and combination of methods as an effective approach for near-surface Vs estimation, demonstrating its usability also for large earth dam embankments.

In highly seismic countries, the maintenance and restoration of existing earth dams involve assessing their seismic performance to design effective rehabilitation strategies. This is a complex issue, particularly in the case of zoned earth dams, where materials with different hydraulic and mechanical properties interact during both normal operation and extreme conditions. Therefore, understanding the response of zoned earth dams under severe seismic loading is crucial to ensure their safety and resilience. Given the limited availability of well-documented case histories, conducting small-scale physical modelling in a geotechnical centrifuge is essential to highlight the most significant aspects of the behaviour of such complex structures. This paper presents the results of two dynamic centrifuge tests carried out to investigate the seismic response of a zoned earth dam, 13 meters in height and 39 meters in width, at the prototype scale. The upstream and downstream slopes consist of compacted sand, while the core is made of compacted clayey sandy silt. Extensive laboratory testing was performed to determine the geotechnical properties of the soils used in the experiments. During the tests, the model was densely instrumented with pore pressure transducers, tensiometers, accelerometers, and linear and rotational sensors to monitor the displacement field of the dam. Under operational conditions in terms of water level, the dam was subjected to a sequence of dynamic excitations of increasing intensity, while recording the dynamic response of the model by the accelerometers installed in the embankment. The research findings contribute to a broader understanding of the behaviour of this category of earth structures under severe seismic conditions and provide valuable experimental data for the calibration of numerical tools to be used for parametric analyses.

Fluctuations in reservoir water levels have a significant impact on the seepage and slope stability of earth dams. The varying rate of the water level and soil-water characteristic curve (SWCC) hysteresis are the main factors affecting the seepage and the stability of dam slopes; however, they are not adequately considered in engineering practices. In this study, the SEEP/W module and the SLOPE/W module of Geo-studio were employed to analyze the seepage features and the stability of downstream slopes, taking into account the water level fluctuation rate and the SWCC hysteresis. The results reveal that the pore water pressure of the representative point forms a hysteresis loop when the water level fluctuates, which becomes smaller as the water level variation rate increases. Within the loop, the pore water pressure with a rising water level is greater than the value when the water level is dropping, and the desorption SWCC derives greater pore water pressures than the adsorption SWCC. Similarly, the safety factor (Fs) curves under the condition of water level fluctuations also form a hysteresis loop, which becomes smaller as the variation rate of the water level increases. When the water level fluctuation rate increases to 4 m/d, the two curves are tangent, meaning that the Fs with a rising water level is always greater than the value when the water level is dropping. The desorption SWCC derives a lower Fs value than the adsorption SWCC as the water level draws up, but this initiates no evident difference in the Fs value when the water level draws down. These findings can be used to inform the design and operation of earth dams under fluctuating water levels.

Featured Application This work is intended to provide additional approaches for analyzing and interpreting dam monitoring data.Abstract Pore water pressure (PWP) response is significant for evaluating the earth dams' stability, and PWPs are, therefore, generally monitored. However, due to the soil heterogeneity and its non-linear behavior within earths, the PWP is usually difficult to estimate and predict accurately in order to detect a pathology or anomaly in the behavior of an embankment dam. This study endeavors to tackle this challenge through the application of diverse machine learning (ML) techniques in estimating the PWP within an existing earth dam. The methods employed include random forest (RF) combined with simulated annealing (SA), multilayer perceptron (MLP), standard recurrent neural networks (RNNs), and gated recurrent unit (GRU). The prediction capability of these techniques was gauged using metrics such as the coefficient of determination (R2), mean square error (MSE), and CPU training time. It was found that all the considered ML methods could give satisfactory results for the PWP estimation. Upon comparing these methods within the case study, the findings suggest that, in this study, multilayer perceptron (MLP) gives the most accurate PWP prediction, achieving the highest coefficient of determination (R2 = 0.99) and the lowest mean square error (MSE = 0.0087) metrics. A sensitivity analysis is then presented to evaluate the models' robustness and the hyperparameter's influence on the performance of the prediction model.

Climate change with extreme hydrological conditions, such as extreme rainfall, poses new challenges to earth dam safety. Reliability analysis helps to reduce the uncertainty of the real behavior of a dam, and provides one more tool to improve dam safety control. Reliability analysis is very important for unsaturated soil dams under rainfall conditions. This paper investigates the safety of an earth dam over time, considering different initial conditions, rainfall intensities, and normal operating conditions (NOC). A direct coupling (DC) method is used to integrate different software. Coupling enables us to use the deterministic software packages Seepage/W and Slope/W with the StRAnD reliability software to perform the numerical investigation. The reliability analyses are performed employing the first-order reliability method (FORM) using the improved Hasofer-Lind Rackwitz-Fiesler (iHLRF) algorithm of optimization. The contribution to failure probabilities of random parameters was analyzed with sensitivity analysis. The saturated hydraulic conductivity (ks) contribution increases when the rainfall intensity increases and when NOC increases or decreases the reservoir. Finally, a critical deterministic slip surface is shown to be very close to the probabilistic one, but a high difference in terms of pore water pressures is reported.