Hydraulic-fill Dam Research Articles

Effect of geomaterial variability on seismic response analyses of earthen dams

In a recently completed research study, two-dimensional (2D) and three-dimensional (3D) seismic response analyses were performed on a hydraulic fill earthen dam located in north Texas, USA. Analysis results obtained from both methods were compared to study and address the influence of geomaterial variability on the seismic response of heterogeneous earthen dams such as hydraulic fill dams. For evaluating the material variability within the dam, twenty-eight piezocone penetration soundings (CPTu) were conducted along the crest of the dam. These CPTu soundings, along with the available laboratory test results, were utilized to represent various scenarios that depict geomaterial variability within the dam for numerical modeling and seismic response analysis. In the first scenario, limited subsurface investigation information obtained from six CPTu soundings distributed along the dam crest was considered to develop the numerical models. In the second scenario, all the twenty-eight CPTu soundings were utilized to model the same dam using extensive site characterization test results. The first natural frequency, earthquake-induced crest accelerations, and shear stresses of the dam segments were computed from 2D and 3D numerical analyses for both scenarios of site characterization results. Results indicated that a 3D analysis might be more appropriate than a 2D analysis for studying the seismic response of a heterogeneous earthen dam, especially when extensive site characterization information is available to model the dam for numerical analyses. Overall, the findings of this study emphasize the impact of geomaterial variability on seismic response analyses of heterogeneous earthen dams and will enable engineers to assess the conditions that warrant a comprehensive 3D analysis.

Geomaterial Characterization and Stability Assessment of Hydraulic Fill Dams

AbstractIn this research study, the stability of a hydraulic fill dam located in a newly declared seismically hazardous zone in north Texas was evaluated, incorporating the effect of geomaterial va...

Seismic Slope Stability Analysis of a Hydraulic Fill Dam

Abstract This paper presents a seismic slope stability assessment study of an inherently heterogeneous hydraulic fill dam in Texas. Extensive cone penetration soundings conducted at the dam site we...

Seismic response analysis of a hydraulic fill dam

The seismic response of a highly heterogeneous hydraulic fill dam was evaluated by studying the natural frequencies of the first and second modes of vibration and analyzing the crest accelerations of different two-dimensional or 2D sections of the dam when subjected to two different earthquake excitations. The existing methods for determination of the natural frequency of earthen embankment structures can only be used to analyze the structural response at small strain levels. However, during seismic events, the natural frequency of an earthen dam is significantly affected by the nonlinear material behavior exhibited by the geomaterials at high strain levels. Hence, a novel method was devised to evaluate the strain-dependent natural frequency for plane strain 2D dam sections, using a synthesized multi-sine base excitation. The degradation of first and second natural frequencies of transverse vibration for all the 2D sections followed a linear trend when plotted against the respective crest’s root mean square strain on a logarithmic scale. The slope of the degradation curve was found to depend on the constituent material properties prevalent in the individual sections. The observed variations in natural frequencies and crest accelerations of the 2D dam sections were also used to assess the suitability of using two-dimensional plane strain analyses for studying the response of a long earthen dam having variability in material properties. Results indicate that there is a considerable chance of erroneous estimation of the seismic response of such highly heterogeneous earthen dams that are conventionally analyzed using plane strain models. A 2D analysis was found to merely capture the seismic response of the individual sections of the dam as independent entities while ignoring the stiffening or weakening effect of the adjacent neighboring segments that may have different material properties.

Natural frequency of earthen dams at different induced strain levels

A method is proposed to estimate the degradation of the first natural frequency of vibration of earthen dams with increase in strain levels induced due to seismic events. A synthesised wave, referred to as the ‘sum of sines’, generated by the superposition of sinusoidal waves with frequencies ranging from 0.01 Hz to 25 Hz, is scaled to different peak accelerations and used to simulate seismic excitations at the base of the dam. The natural frequency is then determined by studying the response of the structure in the frequency domain. For this study, four dams with varying complexities of geometry, constituent material properties, and known natural frequencies were at first selected from previously published literature to establish the validity of the proposed method for determining natural frequencies of the dams at small strain levels. Plane strain models of these structures were constructed and analysed, using a commercially available finite element method-based software that is capable of performing time-history analyses. Results from the analyses indicate a good agreement between the natural frequencies predicted using the proposed method and the frequency values reported in the literature for the corresponding structures at small strain levels. The method was later used to determine the strain-dependent natural frequency of a hydraulic-fill dam in North Texas. Twenty-one different earthquake conditions, with different peak ground accelerations, frequency contents, and mean periods, were used to thoroughly validate the applicability of the developed methodology. Numerical analyses indicate that the strain-dependent variation of the first natural frequency follows a similar trend as that obtained using the ‘sum of sines’ excitation when the dam is subjected to widely different earthquake conditions.

Basis for selection of computational relationship for determination of drift transport during development of break-out channel in bodies of homogeneous hydraulic-fill dams

Approaches adopted in the modern literature for determination of the dynamics of development of break-out-channels in the bodies of earthen dams are examined as a result of emergency situations. Relationships for calculation of drift transport, which are used in channel hydraulics and pressure hydrotransport are compared. Recommendations are suggested for determination of the transporting capacity of a flow for development of break-out channels in the bodies of homogeneous hydraulic-fill earthen dams.

Procedure for analysis of break-out channels within bodies of homogeneous hydraulic-fill dams in emergency situations

A model is proposed for the carry-off of soil from the body of a break-out channel with consideration of its collapse. A procedure is developed for analysis of the formation of a break-out channel within the bodies of homogeneous hydraulic-fill dams with allowance for the grain-size distribution of the particles serving as component parts of their bodies. The dynamics of the change in width of the break-out channel over time, and the rate of the outflow from the channel is determined in an example of an actual project. Results of the numerical experiment are compared with data acquired by other authors.

Liquefaction assessments by field-based methodologies: foundation soils at a dam site in Northeast Turkey

Recent examples show that strong earthquakes can cause damage to dams, notably tailings or hydraulic fill dams or relatively small earth fill embankments. Liquefaction is known to be one of the most dangerous consequences of the dynamic loading of an embankment dam and hence must be considered during the dam site selection and construction stages. This paper presents the liquefaction analyses undertaken for the Demirozu dam site in Northeast Turkey. The liquefaction assessments are mainly based on field-performance data using SPT- and CPT-based methods in conjunction with the results of the available cyclic triaxial tests. The presence of a very shallow groundwater table, loose sandy layers and the seismic features of the region result in a high susceptibility to liquefaction. The results obtained from the SPT- and CPT-based criteria for evaluating the liquefaction potential are generally consistent and show that the thickness of the liquefiable layers increases in the area between the left bank and the central part of the proposed dam. Further studies are required to evaluate the suitability and efficiency of measures which could be taken to avoid liquefaction-induced problems at the dam site.

Seismic upgrade of hydraulic fill dam by buttressing

The vulnerability of hydraulic fill dams under strong earthquake shaking has long been recognized. When located in areas of high seismic hazard, seismic upgrading of these types of dams is often required to meet current dam safety standards. Selection of an appropriate design concept for seismic upgrading of such dams requires careful consideration of seismically induced deformations when the hydraulic fill is to remain as part of the dam. This paper presents a case history of the seismic upgrade of Butt Valley Dam, a hydraulic fill dam located in Northern California. The dam was strengthened to withstand the Maximum Credible Earthquake (MCE) by buttressing of its upstream and downstream slopes. The paper discusses the evaluation of alternatives to upgrade the dam, the design criteria, and the design and analysis of the seismic upgrade. It is shown that a conservative and robust design was developed based on well-established engineering principles and multiple lines of defense, and sound use of analysis procedures including finite-difference non-linear dynamic deformation analyses.

Analytical methods of calculating seepage in inhomogeneous hydraulic-fill dams on an impermeable foundation

Analytical methods of calculating seepage in inhomogeneous hydraulic-fill dams on an impermeable foundation

Delineation of shallow stratigraphy using ground penetrating radar

Ground penetrating radar surveys were conducted at four sites to investigate the shallow stratigraphy and to determine the applicability and performance of the radar technique. A basic analog-recording radar system with a single 80 MHz antenna was used for all of the surveys. Good stratigraphic control existed at all of the sites so that the effectiveness of the radar could be evaluated. The four sites were distinctly different in composition and extent. At an upland farm site in the glaciated region of southwestern Ohio a clay-rich soil covers shallow bedrock. Some soil horizons were identifiable on the radar profiles, but only to a depth of 1.4 m. At a sand and gravel quarry in southwestern Ohio the depositional patterns of the unsaturated deposits were clearly imaged to a depth greater than 4 m. At a hydraulic fill dam in western Ohio the changes in the internal composition of the earthen fill were observed on the radar records to depths of 4 m. On San Salvador in the Bahamas radar profiles over partially consolidated carbonate sand revealed an extensive series of buried beach ridges to depths of 4 m. These data were useful in understanding the depositional history of the area, which could not be determined from surface and pit sampling alone. These studies show that ground penetrating radar is an important tool for studying shallow stratigraphy where the ground conductivity is low enough to permit radar reflections from depths of interest.

Evaluation of two hydraulic fill dams in Alberta : Proc Conference on Hydraulic Fill Structures, Fort Collins, 15–18 April 1988 P511–528. Publ New York: ASCE, 1988 (Geotechnical Special Publication No 21)

Evaluation of two hydraulic fill dams in Alberta : Proc Conference on Hydraulic Fill Structures, Fort Collins, 15–18 April 1988 P511–528. Publ New York: ASCE, 1988 (Geotechnical Special Publication No 21)

Seismic stability of the hydraulic-fill dam of the Kairakkum hydroelectric station

Seismic stability of the hydraulic-fill dam of the Kairakkum hydroelectric station

Hydraulic fill dam made earthquake resistant : Civ Engng, N Y V55, N6, June 1985, P56–59

Hydraulic fill dam made earthquake resistant : Civ Engng, N Y V55, N6, June 1985, P56–59

Substantiation of the selection of the designs of a hydraulic-fill dam for the upper reservoirs of pumped-storage stations

On the basis of the foregoing conditions about the design of hydraulic-fill dams and technology of their construction and also with consideration of the results of comparative calculations of the permeability of these dams, for the upper reservoirs of pumped-storage stations we can recommend dams which have reliable impervious elements, namely, a diaphragm, facing, or placed clay core.

Assessment of liquefaction of soils in saturated sand dams under seismic loads

1. Calculation of the seismic stress-strain state of dams of noncohesive soils for the purpose of analyzing liquefaction is an important and urgent problem, since they are being constructed in seismically active regions. 2. The proposed method of assessing liquefaction of a homogeneous dam can be extended also to inhomogeneous hydraulic-fill dams. 3. The results of the calculations show that the danger of the start of liquefaction increases from the base ot the crest. Therefore the upper layers require a greater relative density.

Seepage regime of the hydraulic-fill dam of the mingechaur hydropower development

1. The anomalies of the seepage regime of the Mingechaur hydraulic-fill dam established during on-site observations are not related to intensification of the seepage flow and at present do not pose a danger for operation of the structure within the normal pool level of the reservoir, 83.0 m, which is also indicated by the temporal constancy of the seepage discharge being intercepted by the toe drain. The static calculations of slope stability under various most unfavorable operating conditions and an investigation of its earthquake resistance show a safe condition of the dam. 2. To judge from the results of investigating the soils of the core zone in the upper part, the Mingechaur hydraulic-fill dam in its current condition should be regarded not as a core-wall dam but as a gravel-sand dam with a lean central zone. About 10 such hydraulicfill dams, although of smaller height, have been constructed in the Soviet Union (Plyavinyas, Dubossary, Kaunas, etc.). 3. The presence of layers of increased permeability in the upper part of the core zone and the very high values of the permeability coefficient (up to 50 m/day) within the coreless “cap” of the dam (above elevation 84.0 m) give rise to the probability of a substantial increase of seepage discharge in the case of raising the level above the normal at reservoir elevations within 83.00–85.50, which can cause overfilling of the drainage system. At the same time we cannot preclude the possibility of the occurrence of contact erosion on the crest of the core zone under these operating conditions. With consideration of the aforesaid, it is recommended to take the elevation of the maximum water level with some margin equal to 83.50 m (the design specified 85.50 m). 4. To ensure safe operating conditions of the Mingechaur hydropower development at the designed maximum operating level above the elevation of the normal reservoir level of 83.0 m, it is required to strengthen the upper part of the core zone and “cap” by creating a watertight barrier. The design of the barrier should be selected on the basis of a technical and economic comparison of possible variants.

Seismic stability of the Mingechaur dam

The Mingechaur hydraulic-fill gravel-pebble dam with a loamy sand--loam core (Hma x = 80 m) on the Kura River was designed in 1948-1950. Its foundation is composed of alternating beds of clays, siltstones, and sandstones of the Apsheronian stage of the Tertiary having almost a vertical dip [1-5]. The right-bank part of the dam intersects beds at a right angle, and the angle between them decreases toward the left bank. The soils of the foundation belong to category II with respect to seismic properties[6].

Calculation of the temperature regime of hydraulic-fill dams during their construction

Calculation of the temperature regime of hydraulic-fill dams during their construction

Development of hydraulic-fill dam construction in the Soviet Union

1. Hydromechanization is characterized by continuity of all the excavation, transportation, and soil placement operations, which ensures high outputs and rates of construction of the structures. 2. Under conditions of floodplains rivers and water-covered pits, or for underwater pits, the only possible type of mechanization of earthwork for dam and dike construction is hydromechanization. 3. In the Soviet Union, new types of hydraulic-fill structures have been worked out and introduced, and improved hydraulic filling techniques have been developed. This has given rise to wide possibilities of use of hydromechanization in hydraulic construction.