Crest Settlement Research Articles

Seismic intensity measures and predictive equations for the evaluation of earthquake—induced crest settlements of earth dams

AbstractIn this paper the results of 2D dynamic finite element analyses of a zoned earth dam are presented and discussed with the aim of detecting proper intensity measures able to describe the variation of the crest permanent settlement with the characteristics of the input ground motion. A large set of horizontal components of earthquake records has been selected and used as input motion considering both upstream and downstream directions. This allowed to explore the activation of plastic mechanisms in the dam embankment and the amplification of the horizontal accelerations. Starting from the analysis results, two original intensity measures, related to the amplitude, energy and frequency content of the input motion, have been detected and original empirical predictive formulas have also been derived to estimate the permanent crest settlement of the dam. The effectiveness of the proposed intensity measures and the reliability of the novel relationships between these intensity measures and earthquake‐induced permanent crest settlements have been checked against (i) numerical results of further dynamic analyses carried out for the same dam using additional sets of input motions, (ii) numerical results available in the literature for two other earth dams and (iii) field data relative to the crest settlements induced in four earth dams by two recent large earthquakes. The whole set of analysis results allowed defining an empirical equation that appears as a promising general predictive tool for the earthquake‐induced crest settlement of earth dams.

Analisa Perbandingan Penurunan Awal Bendungan Tipe Material Timbunan Urugan Batu dan Urugan Tanah (Studi Kasus Bendungan Digoel-Papua)

To create prosperity for the people of Papua Province. The government has made one of the programs, namely the construction of the Digoel Dam in Boven Digoel Regency – Papua. The successful construction and operation of a dam requires a comprehensive evaluation of the design prior to commencement of the construction process. This study aims to analyze the initial settlement that occurred in the Digoel dam type earth fill and rock fill. Initial settlement analysis was carried out using the modulus parameter obtained from the literature. SIGMA/W software has been used to estimate dam crest settlement due to static loading. From the results of the analysis of the initial settlement of the dam with the rock fill and earth fill types, it is accepted that the maximum permissible settlement is 1.59%.

Field research to ensure the safety of the earth dam

One of the ways to ensure the safe condition of earth dams during operation is to conduct field investigations on the structure. One of the factors leading to water spillage over the dam crest is the determination of settlement in the body of the earth dam. The assessment of excessive settlements in reservoir earth dams is based on observation data and project documentation. In practice, the settlement of earth dams during the operational period should not exceed the values specified in the project. Settlement measurements for the embankment body are carried out based on requirements specified in regulatory documents. The Langar Reservoir is located in the Langar River bed in the Kashkadarya region. The facility was built in 1971-1973. It was put into permanent operation in December 1973 with a design capacity of 4.0 million m3 as a mudflow storage facility. Repeat geodetic measurements (second cycle) were conducted to determine the settlement of the dam crest. According to the geodetic measurements, the settlement of the dam crest during the observation period was 15 mm in the first cycle and 18 mm in the second cycle.

Post-Earthquake Reconnaissance of a Dam with Stabilizing Fill using Drone Photogrammetry

Post-earthquake reconnaissance is an important process for assessing the safety of massive structures. Dams are critical structures that require evaluation following an earthquake, as dam failure can lead to significant damage to the surrounding area. This paper presents drone (unmanned aerial vehicle) photogrammetry-based reconnaissance of the Angat Dam (Philippines), which has stabilizing fill, following the M 6.1 Luzon earthquake in April 2019. The author presents the results of visual inspection, drone digital mapping, and seismically induced deformation monitoring, as well as a general interpretation of dam safety. Analysis of the instrumentation data did not indicate that any significant changes in crest settlement, piezometric head, or seepage rate resulted from the earthquake. However, seismically induced longitudinal cracking along the dam crest was observed in the drone photogrammetry. The digital surface model, orthoimage, and as-built GIS geometry characterizations generated using the drone photogrammetry facilitated the geospatial analysis of seismic cracking and deformation. It is found that the uplift deformation was caused by counteracting effects between the existing dam body and its stabilizing fill. It is concluded that the results obtained using drone digital mapping are a valuable reference for future deformation monitoring using regular mapping methods in a 3D geospatial digital model.

Simulation of non-stationary ground motions and its applications in high concrete faced rockfill dams via direct probability integral method

Many high concrete face rockfill dams (CFRDs) have been constructed in earthquake-prone areas in recent years, and it is essential to evaluate the seismic safety performance of these dams considering the randomness of seismic excitation. In this paper, the relationship between the stochastic ground motion generation method and the direct probability integral method (DPIM) is established by using the number theory point selection method as the bridge. The DPIM is introduced into the field of stochastic dynamic analysis and multi-index reliability evaluation of high CFRD for the first time. First, a non-stationary stochastic excitation model at five sites is established based on the latest standard for the seismic design of hydraulic structures. Then, taking a practical project as an example, stochastic dynamic response analysis and reliability assessment based on dam crest settlement deformation and dam slope cumulative slippage are conducted by using DIPM. Finally, the influence of these two indexes on reliability is explored by drawing the equal failure probability curve. The results show that the stochastic dynamic analysis and reliability assessment framework established in this paper can provide probabilistic seismic safety assessments for high CFRDs. Sliding damage of the dam slope is more likely than the deformation damage of the rockfill from the perspective of probability.

Selection of efficient earthquake intensity measures for evaluating seismic fragility of concrete face rockfill dam

This study explores the crucial role of intensity measure (IM) selection for probabilistic seismic demand model development of concrete face rockfill dam (CFRD) subjected to earthquake ground motions. Nonlinear dynamic analyses are performed for CFRD with an advanced hysteretic soil model using a finite element analysis program to develop a database of earthquake-induced dam crest settlements. The numerical model is validated through centrifuge model test measurements. A selection process was carried out to evaluate the IMs based on the goodness of fit, as well as their efficiency, practicality, and proficiency. Eventually, a range of optimal IMs are selected. Conditional probability function is employed to develop fragility curves for CFRD employing both scalar and vector IMs. Five settlement ratio-based limit states are defined herein. The results show that vector fragility surfaces produce enhanced predictions of the dam damage compared with the scalar fragility curves that are most often employed.

Numerical Simulation of Piles in a Liquefied Slope Using a Modified Soil–Pile Interface Model

The liquefaction of soil surrounding a pile significantly affects the dynamic interaction between the soil and the pile. In particular, liquefaction of the sloping ground can induce permanent deformation and a bending moment on the pile due to the lateral displacement of the liquefied soil in the downslope direction. However, numerical analysis studies on piles installed in a liquefiable slope have been very limited and have not properly simulated the behavior of the pile. Therefore, a modified soil–pile interface model was proposed, which linearly decreases the interface friction angle with the increase in the excess pore pressure ratio. The proposed model was validated by comparing it with the centrifuge test results of Yoo et al. (2023). Simulation results on the slope crest settlement and the pile-bending moment showed good agreement with the centrifuge test results. A parametric study was conducted by applying the validated model to analyze the effect of slope inclinations and the amplitude of input motions on the slope displacement and the pile moment. The simulation results showed that the slope inclinations affected the area of the sliding mass, causing a larger pile-bending moment with a larger inclination. When the amplitude of the input motion was sufficiently large to trigger the failure of the liquefied slope, the slope displacement and the pile-bending moment did not increase any further.

Stability of Slopes under Dynamic Loading using FEM Software

Abstract: In this study, the dynamic stability of soil slopes was analysed using the finite element method (FEM). The analysis was performed using the Plaxis 2D software, which is a popular FEM software package. The study aimed to investigate the behaviour of soil slopes under dynamic loading conditions and to evaluate the accuracy and effectiveness of the FEM approach for predicting slope stability. A 2D slope model was created using Plaxis 2D, and dynamic analyses were performed under different loading conditions. A Shake Table was used for simulating the loading conditions at different frequencies and amplitude. The results of the analysis showed that the slope stability was highly dependent on the dynamic loading conditions and the soil properties. Under earthquake like ground motions which were simulated with the help of shake table under controlled environment, the slope experienced significant deformations and displacements. The deformations were calculated in the form of crest settlement and toe settlement. The study also evaluated the accuracy of the FEM approach by comparing the simulation results with the experimental data. The comparison showed that the FEM approach provided a good prediction of the slope behaviour under dynamic loading conditions and could be used as a reliable tool for analysing slope stability. Overall, the study demonstrated the effectiveness of the FEM approach for analysing the dynamic stability of soil slopes and highlighted the importance of considering dynamic loading conditions in slope stability analysis. The study also provided insights into the behaviour of soil slopes under different loading conditions and could be useful for designing safer and more stable slopes in practice.

Dynamic Behaviour of Small-Scale Soil Slope Model

bstract: The shaking table test is an experimental method used to determine the dynamic behaviors of the structure in a laboratory environment to obtain the realistic results which are required to check the stability of the structure before the construction process. In this study, under earthquake-like ground motions which were simulated with the help of a shake table under a controlled environment, the slope experienced significant deformations and displacements. The deformations were calculated in the form of crest settlement and toe settlement. The study also provides insights into the behaviour of soil slopes under different loading conditions and could be useful for designing safer and more stable slopes. The crest and toe displacement of a small-scale model of soil slope at various inclinations to study the behaviour under dynamic loading. The soil slope model behaviour under dynamic loading is observed for the amplitude is ±20mm, ±25mm, and ±30mm for the frequencies varying from 1.2Hz to 1.8Hz for each inclination of 30°, 35°, and 40° keeping the height constant. The displacement was measured in the form of crest and toe settlement every 10 cycles.

Empirical relationships for estimating the crest settlement of earth-core rockfill dams subjected to earthquakes

In this study, new empirical predictive relationships for earthquake-induced crest settlement of earth-core rockfill dams (ECRDs) were developed. A case history database of 19 dams that had been subjected to earthquakes was utilized. The presented relationships correlate the intensity measure (IM) of the earthquake records with the observed settlements, and thus, employing IMs that appropriately describe the severity of ground motion is of vital importance. It is well known that the dynamic properties of an ECRD can change significantly depending on the severity of an earthquake, and that this phenomenon can substantially impact the dynamic responses of dams. Accordingly, two IMs were suggested, taking into account the essential characteristics of ground motions affecting the nonlinear behaviour of ECRDs. The results indicate that the proposed relationships effectively address the limitations of the existing ones, and that they are practical tools that efficiently predict the seismic settlements of ECRDs.

Результаты натурных исследований осадок в теле земляной плотины

The purpose: to conduct field studies to determine the vertical settlement in the body and assess the safety of the earthfill dam of the Lyangar reservoir. One of the ways to ensure the safe condition of earthfill dams during operation is to conduct field studies in the facility. One of the factors leading to the overflow over the structure crest is the settlement of the earthfill dam body. Excessive settlement of the earthfill dams of reservoirs are assessed on the basis of observational data and design documentation. In practice, the settlement of earthfill dams during the operational period should not exceed the values specified in the project. The quantitative determination of the settlement of the earthfill dam body was carried out on the basis of the requirements specified in the regulatory documents. Materials and methods. In the process of research, theoretical and generally accepted detection methods of vertical deformations on the crest of an earthfill dam using geometric leveling were used. The research and verification of tools was carried out in accordance with regulatory documents before carrying out the work. Results. Geodetic measurements were carried out on the example of the earthfill dam of the Lyangar reservoir. Repeated geodetic measurements (the second cycle) for determining the settlement of the earth dam crest were carried out. The longitudinal profile of the crest of the object under consideration was constructed on the results of geodetic measurements. During the observation period, the settlement of the earthfill dam crest was 15 mm in the first cycle and 18 mm in the second cycle. Conclusions. The indicators obtained as a result of geodetic measurements, when compared with the indicators given in the regulatory documents, testify that the safe state of the structure is ensured, which does not lead to water overflowing over the earthfill dam crest.

Simplified assessment of the seismic vulnerability of small earth dams

The seismic performance of earth dams is usually assessed based on the expected crest displacements induced by the soil densification and the triggering of sliding mechanisms. Nevertheless, a proper evaluation of the seismic response of the dams generally involves the use of advanced constitutive models able to reproduce the dynamic soil response. The calibration of the constitutive parameters is however a nontrivial task, as it requires a deep understanding of the mechanical response of the materials. When dealing with small earth dams, budget constraints often prevent a reliable geotechnical characterization of the soils, limiting in the common practice the applicability of dynamic numerical simulations. The performance of the dams is therefore assessed, at least at a preliminary level, by employing simplified empirical relationships that link a seismic intensity measure to the expected crest settlement. This study fits within this framework, presenting the results of the ReSba European project for the French-Italian Alps area. Two small earth dams, object of extensive geophysical and geotechnical surveys, are selected based on a first-level screening methodology. Advanced fully-coupled numerical simulations are performed to investigate the seismic response of the dams. The results of the analyses are then compared to predictions obtained by employing empirical relationships to show the abilities, and the potential drawbacks, of the simplified relationships.

Performance efficiency of data-based hybrid intelligent approaches to predict crest settlement in rockfill dams

Performance efficiency of data-based hybrid intelligent approaches to predict crest settlement in rockfill dams

Study on collapse settlement and cracks of core wall rockfill dams under wetting deformation

AbstractThe safety and stability of core wall rockfill dams during impoundment are threatened by the wetting deformation of up‐stream shell materials. The serious wetting deformation not only aggravates the collapse settlement of upstream rockfill but also intensifies differential settlement of the dam crest during impoundment, and then causes cracks on the dam crest. On the basis of the proposed wetting deformation model and its simulation method of wetting deformation, this paper simulated the impoundment process of Guanyinyan core wall rockfill dam and studied the deformation characteristic of the dam during impoundment. In addition, the smeared cracking model was used to simulate the crack propagation on the dam crest, and the crack develop and spread mechanism was analysed. The results show that the simulated deformation can fit the in‐situ data well, and the simulated crack propagation is in good agreement with the actual situation. Once watered, the upstream rockfill and core wall have significant settlement, and the whole dam crest has obvious horizontal displacement towards the upstream. It is on the same order of magnitude that the increment of horizontal displacement and settlement at the top of the dam during impoundment. In the process of impoundment, the upper part of the dam tends to deform towards the reservoir area, which will lead to tensile cracks appearing in the rockfill areas on both upstream and downstream sides of the core wall of the dam crest, and the propagation direction of the cracks is basically parallel to the adjacent core wall surface. With the water level rising, the cracks on the downstream side of the dam crest mainly extend vertically, and the cracks on the upstream side of the dam crest not only extend vertically, but also extend horizontally.

Investigation of the Performance of Artificial Intelligence Methods in Estimating the Crest Settlement of Rockfill Dam with a Central Core

Investigation of the Performance of Artificial Intelligence Methods in Estimating the Crest Settlement of Rockfill Dam with a Central Core

Two-dimensional DEM-FEM coupling analysis of seismic failure and anti-seismic measures for concrete faced rockfill dam

The concrete faced rockfill dam is composed of granular materials and the failure pathways typically exhibits multi-scale mechanical behavior. In this paper, a 2D polygonal DEM-FEM interface coupling analysis program is developed and introduced to the failure analysis of a 100 m high CFRD under strong earthquake. The polygonal DEM is developed to describe the strong-nonlinearity, large deformation and discontinuous of dam. The FEM and seismic wave input method is combined to simulate the dam-foundation interaction. A boned model is proposed to describe the deformation characteristics of face slab and anti-seismic measure. The results indicate that the initial seismic failure of CFRD occurs at the crest zone, and is characterized by the loosening, sliding and even rolling away of the shallow rockfill on the slope. Other initial failure modes include settlement of the dam crest, separation between the face slab and rockfill, downstream sliding of the wave wall and separation between wave wall and face slab. The installation of a nailed protective slab at the upper part of the downstream slope reduces the seismic damage by 27–41 %. The analysis method can intuitively reproduce the seismic failure mode and failure evolution of the CFRD and quantify the effect of the anti-seismic measure.

Post-construction safety assessment of a high concrete face rockfill dam

The most important issue regarding the safety and performance of concrete face rockfill dams (CFRDs) is to determine stresses and deformations. However, predictions of crest settlements of CFRDs are usually performed using empirical relationships. In recent years, CFRDs have been constructed much higher and at more complicated topographical and geological dam sites, so numerical analysis is required to evaluate the stress and deformations in the entire dam body. Also, assessing long-term rockfill behaviour and the concrete face membrane crack potential are important for post-construction dam safety. This study evaluates post-construction deformations and crest settlements of a high CFRD under two different loading cases, considering the non-linear elasto-plastic behaviour of the rockfill structure. As a constitutive model, the Duncan–Chang hyperbolic stress–strain model was applied in finite-element simulations considering the failure criterion is isotropic and hardening. Calibration of the rockfill's hyperbolic parameters was performed by comparing the calculated displacements with actual settlement measurements. Computed crest settlements were also compared with those of some CFRDs given in the literature. Calculated crest settlement and other deformations are in good agreement with the rockfill settlement measurements and in acceptable ranges, and do not threaten the dam's safety.

Predicting the Crest Settlement of Concrete Face Rockfill Dams by Combining Threshold Regression and Support Vector Machine

Predicting the Crest Settlement of Concrete Face Rockfill Dams by Combining Threshold Regression and Support Vector Machine

Seismic Performance Screening and Evaluation for Embankments on Liquefiable Foundation Soils

This paper proposes a framework for screening and evaluating seismic performance of river earth embankments on liquefiable foundation soils. The framework is executed in the order of simplest screening by soil liquefaction potential map to preliminary and detailed evaluation of seismic performance of embankment according to the sufficiency of data and the complexity and accuracy of the methods. The seismic performances of embankments are classified into four levels based on the seismic-induced crest settlement. The method used for preliminary evaluation is based only on the factors of safety of foundation soils against liquefaction and the embankment slope against sliding. The static softening method (SSM) and dynamic effective stress method (DESM) are suggested for detailed evaluation of seismic performance. SSM is a static FDM or FEM analysis for estimating liquefaction-induced settlement by weakening the strength of the liquefied foundation soil under the action of the self-weight of the embankment. However, DESM is a dynamic history analysis for estimating liquefaction-induced settlement by simulating the generation and dissipation of pore water pressure in the liquefaction process of foundation soils under the action of the self-weight of the soil embankment and its seismic inertial force. The damaged embankment of the Maoluo River in the 1999 Chi-Chi earthquake was used as a case to demonstrate the feasibility of this framework. The results showed that the simpler the adopted method is, the more conservative the estimated settlement.

Study on Deformation Characteristics of Loess Ultrahigh-Fill Slope Based on Large-Scale Undisturbed Soil Centrifugal Model Tests

Taking the loess high-fill project of Lv Liang airport in China as the research object, large-scale centrifugal tests were carried out to investigate the deformation characteristics of the collapsible loess ultrahigh-fill slope under natural moisture content and saturated state by using a joint model of undisturbed loess and remolded loess. The results show that the consolidation deformation of the collapsible loess ultrahigh-fill slope is the main factor causing its deformation. The post-construction deformation amount and deformation rate are large in the early stage, and the relationship between the post-construction deformation and thickness of filling body is linear. When the water content of soil increases due to infiltration, the consolidation of the filling body and the collapse of the undisturbed foundation loess will cause settlement and deformation of the slope. The slope may crack along the soft zone formed when the water infiltrates. When failure occurs, the sliding surface will pass through the collapsible soil layer. The contact surface between the collapsible loess layer and the adjacent soil layer is part of the sliding surface, and the contact surface with a relatively low strength will be damaged first. When the strength difference between adjacent soil layers is large, the upper soil layer on the slip surface shows a typical translational sliding mode. The slip surface is approximately arc-shaped, and there is a transition layer with a specific thickness between the slip surface and contact surface. The water content of the high-fill slope has a great influence on the post-construction settlement of the slope crest and slope stability. The post-construction settlement of the slope crest increases with the increase in the water content of the filling body, and the stability coefficient of the slope decreases with the increase in the water content of the filling body. In the saturated state, the sliding force of soil increases, the shear strength decreases, and the stability of high fill slope decreases. Therefore, it is necessary to strengthen the inspection of the rationality of drainage system design in slope construction to ensure slope safety.