Earth-fill dams are the most common types of dam and the most economical choice. However, they are more vulnerable to internal erosion and piping due to seepage problems that are the main causes of dam failure. In this study, the seepage through earth-fill dams was investigated using physical, mathematical, and numerical models. Results from the three methods revealed that both mathematical calculations using L. Casagrande solutions and the SEEP/W numerical model have a plotted seepage line compatible with the observed seepage line in the physical model. However, when the seepage flow intersected the downstream slope and when piping took place, the use of SEEP/W to calculate the flow rate became useless as it was unable to calculate the volume of water flow in pipes. This was revealed by the big difference in results between physical and numerical models in the first physical model, while the results were compatible in the second physical model when the seepage line stayed within the body of the dam and low compacted soil was adopted. Seepage analysis for seven different configurations of an earth-fill dam was conducted using the SEEP/W model at normal and maximum water levels to find the most appropriate configuration among them. The seven dam configurations consisted of four homogenous dams and three zoned dams. Seepage analysis revealed that if sufficient quantity of silty sand soil is available around the proposed dam location, a homogenous earth-fill dam with a medium drain length of 0.5 m thickness is the best design configuration. Otherwise, a zoned earth-fill dam with a central core and 1:0.5 Horizontal to Vertical ratio (H:V) is preferred.

https://www.mdpi.com/2071-1050/12/6/2490/pdf

Experimental and Numerical Analysis for Earth-Fill Dam Seepage

Monitoring and characterizing the deformation of an earth dam in Guangxi Province, China

Plate anchors are embedded into the ocean floor to provide holding capacity for offshore structures. Anchor holding capacity is a function of both the anchor and soil properties. Although plate anchors have been widely studied experimentally and numerically, there is still no universally agreed-upon design approach, indicating that the problem physics remain elusive. In this work, discrete-element method (DEM) simulations were used to investigate the behavior of plate anchors during pullout in an effort to elucidate some of the microscale physical processes that influence overall system behavior. Macroscale assembly response was compared to published experimental results and empirical solutions. The influence of embedment ratio, anchor roughness, soil density, and anchor size on holding capacity was investigated, and system-scale results reasonably agreed with previously published work. Thus, observations of the simulated contact force network and particle velocity during uplift were used to provide insight into anchor failure mechanisms. Finally, the model was used to briefly explore the response of a cyclically loaded plate anchor embedded in a granular assembly. DOI: 10.1061/(ASCE)GM.1943-5622.0001367. © 2019 American Society of Civil Engineers. Author keywords: Plate anchor; Breakout factor; Pullout force; Failure mechanism; Contact force network.

Three-Dimensional Simulations of Plate Anchor Pullout in Granular Materials

Seismic fragility analysis of high concrete faced rockfill dams based on plastic failure with support vector machine

Reservoir dams have varying degrees of damage and hidden dangers under long-term and complex operating conditions, engineering problems mainly focus on the gradual decrease of seepage stability and guarantee rate of deformation and stability of dam foundation. However, due to the complexity of the dam foundation structure and the surrounding environment, the performance degradation of the dam foundation caused by the aging of the impervious structure lacks a systematic study of the process and its mechanism, In particular, the determination of relevant seepage parameters is complicated, moreover the simulation accuracy of its inversion model is not enough to meet the needs of long-term stability evaluation of the dam foundation. In order to study the seepage stability of the dam foundation of the reservoir during operation, a three-dimensional finite element model of complex geological bodies is combined with artificial neural network to establish a model of inversion of seepage field in the dam foundation, According to the 22 groups of predicted grouting schemes, five groups of representative grouting schemes were selected and the seepage characteristics of the same location were analyzed. The conclusions as below: (1) the inversion predicted that when the permeability coefficient was in the range of 3.0 × 10−6 cm/s to 5.0 × 10−6 cm/s, the change range was small, and the curtain's anti-seepage effect was more obvious. (2) The analysis of the dam base surface and the bottom of the grouting area shows that the difference between the water head and seepage gradient of the dam base surface and the bottom of the grouting area under the GZ7 and GZ3 schemes vary significantly with the grouting effect. Among them, especially in the GZ3 scheme, the key parts of the dam foundation surface F2 ~ F4: the seepage gradient value gradually increases, and all reach the maximum value in the GZ3 scheme; For G6 ~ G15 at the bottom of the grouting area, the water head value under the GZ3 scheme is gradually smaller than the three grouting schemes of GZ11, GD3 and GD7, as the water head value gradually decreases, the anti-seepage effect becomes more and more obvious. The above results show that the inversion prediction range is in good agreement with the actual law, when the permeability coefficient is within the predicted range, the anti-seepage effect is optimal. (3) The difference of the water head and seepage gradient difference between the dam foundation and the grouting area near the curtain changes significantly with the grouting effect. Characteristics of seepage field in key parts of the dam foundation under the six curtain grouting coefficients, the water head value F1-F2 decreased by 75%, F3-F13 decreased by 28%, the seepage gradient value F1-F2 decreased by 88%, and F3-F13 decreased by 29%, namely the grouting effect of the dam foundation and the grouting area gradually weakens as the distance between the characteristic part and the curtain increases. The research in this paper can provide a theoretical reference for the analysis and evaluation of dam seepage conditions.

Research on seepage field of concrete dam foundation based on artificial neural network

https://cyberleninka.org/article/n/236773.pdf

Seepage and Stability Analyses of Earth Dam Using Finite Element Method

This letter investigates the uplift capacity of plate anchors in granular soils. Simulations based on a discrete-element method are used to measure the uplift capacity of anchors of differing widths to embedment B/H and width to grain-size B/d ratios. Results confirm that the uplift capacity of anchors with a large B/d ratio is well described by existing models developed from continuum mechanics, with no grain-size effect. In contrast, results reveal a strong deviation from these models for anchors with relatively small B/d ratios. A semi-empirical model is introduced that captures this strong grain-size effect. This model is further supported by a micro-mechanical analysis, indicating that anchor uplift capacities are not only governed by a frustum mechanism predicted by continuum mechanics but also involve the mobilisation of grains surrounding this frustum. These results and model are particularly important to rationalise uplift capacities measured in small-scale experiments, typically involving small ...

Grain-size effect on uplift capacity of plate anchors in coarse granular soils

We investigate the ability to move of large objects—referred to as intruders—embedded in a granular material and subjected to cyclic loadings A discrete element method is used to simulate the dynamics response of intruders subjected to a vertical uplift cyclic force, exploring a wide range of loading magnitudes and frequencies The analysis of the intruder and grains displacements over many cycles reveals three mobility regimes In the first two regimes, called confined and failure the intruder either do not significantly move or consistently moves upward after each cycles We introduce a physically based model considering an inertial drag force to rationalise the existence of these regimes depending on the loading frequency and magnitude We further evidence a third intermediate regime of creep, where intruder trajectories exhibit long periods of confinement punctuated by shorter periods of sustained uplift motion Finally, we observe unexpected failures at low loading magnitudes and specific frequencies, which we attribute to a process of elasto-inertial resonance These results highlight the important differences in the mobility of intruders upon constant and cyclic loadings

Mobility in granular materials upon cyclic loading

We find evidence that the granular drag force on an object moving through a granular material is strongly enhanced when the object is accelerating. This effect can be explained by showing that the accelerating object accelerates the grains nearby, inducing an inertial resistance.

Inertial drag in granular media

Like in liquids, objects moving in granular materials experience a drag force. We investigate here whether and how the object acceleration affect this drag force. The study is based on simulations of a canonical drag test, which involves vertically uplifting a plate through a granular packing with a prescribed acceleration pattern. Depending on the plate size, plate depth and acceleration pattern, results evidence a rate-independent regime and an inertial regime where the object acceleration strongly enhances the drag force. We introduce an elasto-inertial drag force model that captures the measured drag forces in these two regimes. The model is based on observed physical processes including a gradual, elasto-inertial mobilisation of grains located above the plate. These results and analysis point out fundamental differences between mobility in granular materials upon steady and unsteady loadings.

Shivakumar Athani

Papers

Seepage and Stability Analyses of Earth Dam Using Finite Element Method

Grain-size effect on uplift capacity of plate anchors in coarse granular soils

Mobility in granular materials upon cyclic loading

Inertial drag in granular media

Inertial drag in granular media.