Dam Type Research Articles

Breach Progression Observation in Rockfill Dam Models Using Photogrammetry

Dam failures are examples of man-made disasters that have stimulated investigation into the processes related to the failure of different dam types. Embankment dam breaching during an overtopping event is one of the major modes of failure for this dam type, comprising both earthfill and rockfill dams. This paper presents the results of a series of laboratory tests on breach initiation and progression in rockfill dams. Especially eight breaching tests of 1 m-high 1:10 scale embankment dams constructed of scaled well-graded rockfill were conducted. Tests were performed with and without an impervious core and under different inflow discharges. Controlling instrumentation includes up to nine video cameras used for image analysis and photogrammetry. A previously little-used technique of dynamic 3D photogrammetry has been applied to prepare 3D models every 5 s throughout the breaching process, allowing us to track in detail breach development. These dynamic 3D models along with pressure sensor data, flow data, and side-view video are used to provide data on erosion rates throughout the breaching process. One important purpose of this research is to test methods of observing a rapidly changing morphology such as an embankment dam breach that can easily be scaled up to large-scale and prototype-scale tests. The resulting data sets are further intended for the verification of existing empirical and numerical models for slope stability and breach development as well as the development of new models.

The Effect and the Potential Use of Magnetic–Dam Barrier in Guided Bone Regeneration: A Laboratory Study

Guided bone regeneration (GBR) has been shown to be an optimal technique to accelerate the bone regeneration process thanks to the action of membrane barriers that promote tissue healing through the process of osteogenesis, inducing the repopulation with osteoprogenitor cells that prevent the invasion of non-osteogenic tissue. However, current membranes, such as expanded polytetrafluoroethylene or rubber dam, have some disadvantages that could potentially reduce the effectiveness of GBR. Recently, some scaffolds with magnetic properties have been tested to promote rapid osteogenesis. The aim of this laboratory study was to evaluate the intensity of the magnetic field generated by a custom-made rubber dam magnetised with neodymium-iron-boron (Nd2F14B) (three layers of latex filled with Nd2F14B powder on the inner surface) and to understand the effects of such a membrane on cell viability. A magnetic field of 750 G, 400 G, and 900 G was generated on the surface and on the long and wide sides of 3 and 2 cm in contact with the rubber dam. At a distance of 1 mm from the magnetic dam, a magnetic field of 300 G, 150 G, and 400 G was measured on the surface and on the long and wide sides of the rubber dam, respectively. After 72 h, the MG-63 osteoblast-like line showed a slight decrease in cell proliferation (85 ± 10) compared with the unmodified dam (95 ± 6) and the cell control population. According to our findings, this magnetic cofferdam is able to generate a static magnetic field and significantly affect cell proliferation in contrast to other nonabsorbable membranes. Further laboratory studies and subsequent clinical trials are needed to evaluate the significant improvements that can be achieved by using this type of magnetic rubber dam in GBR.

Phreatic seepage around a rectilinear cutoff wall: The Zhukovsky-Vedernikov-Polubarinova-Kochina dispute revisited

The problem of steady 2-D potential Darcian flow from a flat-bottomed reservoir of a coffer or other type of dam, separated from an empty tailwater by an impermeable vertical sheet piling, is one of the pillars in groundwater hydrology and soil mechanics. Analytical solutions to this problem are presented in the books by Forchheimer, Zhukovsky, Vedernikov, Polubarinova-Kochina, Harr, among others. For the case of seepage with a phreatic line, descending from the downstream face of the cutoff, the formulae presented in classical textbooks - despite the simplicity of conformal mappings of the complex potential quarter-plane onto the Zhukovsky half-strip - have lacunae and flaws. We discuss and clean the mismatch in the abovementioned formulae. The classical analytical solutions in the textbooks deal with the regime of no backwater, for which the magnitude of the specific discharge vector at infinity coincides with hydraulic conductivity of the soil. We obtain a general solution for most general flows with backwater, for which the specific discharge at infinity is zero and the free surface has an inflection point in the physical plane. The capillary fringe in the hodograph domain is imaged by a circular cut. The pressure head infinitely deep under the cutoff-wall is infinite. A circular tetragon in the hodograph domain is conformally mapped onto the quadrant in the complex potential plane via a reference plane. In the case with backwater, one extra condition is needed to fix a mathematical solution. For this purpose, the location of a point on the free surface is fixed. Mathematically, two affixes in the reference plane are found by solving a system of two nonlinear equations (in the no backwater case, only one affix is found and one equation is solved). We also examine flow with a phreatic line in a low-permeable layer (e.g. concrete apron of a dam) with an Λ-shaped topology of streamlines, bounded from the left by a cutoff. Seepage from a dam reservoir through a subjacent highly-permeable alluvium induces the pore water motion in the upper layer. A Hilbert boundary-value problem is solved for the complex potential in this cell. In the Kirkham-Brock type boundary condition along the interface between the two layers, the horizontal component of the specific discharge is constant. Phreatic surfaces rising on the downstream face of the cutoff caps Λ−shaped streamlines, which turn around a hinge point on the interface between two layers of contrasting permeability.

Feasibility study on construction of RCC gravity dam under special climatic conditions in Tibet

According to the experience in the construction of water conservancy and hydropower projects in the Mainland, RCC dam construction has two main advantages: the rapid construction speed of roller compacted concrete can realize early power generation, and the price of fly ash is much lower than that of cement, which can reduce the project cost. Tibet has special geographical environment and climatic conditions, and generally has the characteristics of “high altitude, low pressure, low temperature, large temperature difference between day and night, and dry climate”. Taking the dam-building environment in central Tibet as an example, through investigation and research and analogy of similar projects, this paper analyzes the adaptability of construction of RCC gravity dams in Tibet from the aspects of geographical environment, climatic conditions, material properties, construction progress, and project cost. Adaptability to high altitudes. It provides a reference for choosing a safe, reliable, economical and reasonable dam type in the construction of water conservancy and hydropower projects. It provides reference for selecting safe, reliable, economical and reasonable dam types in water conservancy and hydropower engineering construction.

Low‐head dam removal increases functional diversity of stream fish assemblages

AbstractDespite the growing number of dam removals, few have been studied to understand their impacts on stream fish communities. An even smaller proportion of dam removal studies focus on the impacts of low‐head dam removals, although they are the most common type of dam. Instead, the majority of removal studies focus on the impacts of larger dams. In this study, two previously impounded Illinois Rivers were monitored to assess the impacts of low‐head dam removal on the functional assemblage of stream fishes. Study sites were sampled each fall from 2012–2015 (pre‐dam removal) and 2018–2020 (post‐dam removal) in three locations: the tailrace, impoundment, and river channel. Fishes were aggregated into habitat and reproductive guilds, relating community changes to habitat, environmental metrics, and stream quality. Prior to removal, the slackwater guild was the most prevalent habitat guild throughout both rivers, while nest builders and benthic spawners were the most abundant reproductive guilds. During the two years following removal, fish assemblage throughout both rivers shifted to a more evenly distributed representation of habitat and reproductive guilds, while restoration of lotic habitat conditions increased, as surface water temperatures decreased and QHEI, IBI, and dissolved oxygen increased. This shift in environmental metrics and increase in overall stream quality increased, particularly in the formerly impounded reaches, indicate diminished habitat homogeneity, and a shift towards natural habitat diversity. This habitat diversification likely led to the restoration of a range of potential niches, thereby increasing the array of guild types inhabiting these rivers, while simultaneously preventing single‐guild dominance.

Review of Seepage Behaviour on Concrete Facing Rockfill Dam Based on FEM Simulation and Chemical Aspect

Concrete Facing Rockfill Dam (CFRD) is a popular type of dam for hydropower plant due to its relatively good stability than others. However, CFRD have a potential technical issue concerning seepage and leakage as it has a thin impermeable layer. In this study, dam stability against seepage was evaluated by finite element simulation. Concrete facing layer and dam foundation were assumed to undergo permeability coefficient (K) increasing within 3 stages and would be simulated within 15 scenarios. Furthermore, seepage chemistry analysis was conducted to evaluate seepage water interaction with the dam foundation. FEM simulation shows that increasing of permeability coefficient on concrete facing < 10-5 m/second tends to cause the exceedance of allowable seepage discharge (q-simulation > q-allowable). On other hand, the increase of permeability coefficient on the dam foundation tends to cause the dam failure against seepage force. According to seepage chemistry analysis, calcium ion Ca2+ concentration increase 1.8 times from 13.6 meq/L on 2019 sampling to 24.8 meq/L on 2020 sampling. The seepage chemistry analysis shows the sign of carbonate rock interaction as dam foundation with seepage water.

Investigation of Reciprocal Cross Effects in F2 Nellore–Angus Calves

The objectives of this study were to analyze calf performance traits and sex ratio frequencies in reciprocal Bos indicus–Bos taurus F2 Nellore–Angus calves (n = 539). The F2 calves were produced using reciprocal Angus-sired (AN) and Nellore-sired (NA) F1 sires and F1 dams, resulting in four F2 cross types. Calf weight traits were analyzed using mixed models. Deviations from 50% calf sex ratios were tested against expected binomial thresholds. Dam type influenced Julian birth date (p &lt; 0.05) with calves from AN cows born 5 to 6 days earlier than calves from NA cows. Sire type and dam type affected birth weight (p &lt; 0.05) with calves from NA parents approximately 2.5 kg heavier than those from AN parents; weaning weight did not differ for parent F1 type. However, an interaction between sire and dam types affected weaning weight (p = 0.038) where AN x AN calves were 5 to 8 kg lighter than other crosses. Sire type influenced calf sex distribution at birth (p = 0.036) and at weaning (p = 0.026) with NA sires producing over 66% male calves. These results suggest birth weight reciprocal differences due to parental line of descent typically observed among F1 Bos indicus–Bos taurus crosses can persist in subsequent generations.

​Impact of Non-genetic Factors on Kleiber Ratio in Field Flocks of Marwari Goat

Background: The Kleiber ratio in a goat is an important parameter related to feeding and health care. The present study was undertaken to assess the kleiber ratio of 3079 Marwari goats (born from 2016 to 2021) of registered farmers under the All India Coordinated Research Project on goats (Marwari goat field unit) in semi-arid region of Rajasthan. Methods: The linear mixed model used for kleiber ratio estimation included: year of birth, sex, cluster, birth type and age of dam as fixed factors. Result: Overall least-squares means (LSM) for Kleiber ratio (KR) from birth to 3 months (KR1), 3 to 6 months (KR2) and 6 to 12 months (KR3) were 12.89±0.03, 9.69±0.05 and 4.59±0.06, respectively. Year of birth and cluster had highly significant effect on all KR. The birth type had significant on all KR except KR1. The non-significant effect of sex and age of dam were observed on all KR except KR1. The study revealed that the KR was affected by different non-genetic factors. The heritability estimates for KR1, KR2 and KR2 were 0.66±0.28, 0.07±0.07 and 0.54±0.26, respectively.

Geophysical and geological considerations for characterizing the dam foundation during the Memve’ele dam construction (southern Cameroon): influence on the dam type retained

Geophysical and geological considerations for characterizing the dam foundation during the Memve’ele dam construction (southern Cameroon): influence on the dam type retained

Comparison and Selection of Dam Type and Analysis of Structural Stress Calculation for Yangzhongyan Reservoir

Comparison and Selection of Dam Type and Analysis of Structural Stress Calculation for Yangzhongyan Reservoir

Research on profile design criteria of 100 m CSG dams

Cemented sand gravel (CSG) dams, as a newly-developing dam type, has attracted great attention in dam construction industry around the world due to its environmental friendliness and economic efficiency. However, there has been no uniform design specification for its construction yet due to insufficient application research. Based on the design theories of concrete dam and earth-rock dam, this paper quantified the impact and control factors of the foundation with reference to the sluice design theory, proposed the structural failure mode and optimal profile of four 100 m CSG dams with different cementing material content under different foundation conditions, and analyzed the profile design criteria of 100 m CSG dams. Results showed that: (1) the failure modes of CSG dams may include overall instable failure along the dam foundation plane, instable failure of dam slope and local stress failure of dam or dam foundation, etc.; (2) if CSG materials were used in rock foundation, the dam body stress should be used as the control criterion; while on extremely soft rock foundation, the control criterion should be based on the amount of CSG materials; (3) if CSG materials were used on rock-soil foundation, bearing capacity and anti-sliding stability of the foundation should be used as the control criterion; while on gravelly soil foundation, the control criterion should be based on the amount of CSG materials. These results may be used as a reference for designers, laying a foundation for the extension and application of CSG dams.

Effect of engineering geological properties on dam type selection of the Qadis Khordak Dam, Afghanistan

This paper deals with engineering geological properties of Qadis Khordak dam site in Northwest Afghanistan. This study is based on on-site and laboratory tests, surface discontinuity surveying, drilled borehole and permeability test of dam foundation. The engineering geological properties at the dam site were studied in order to evaluate geotechnical characteristics of rock masses at dam foundation, geotechnical properties of alluvium at dam axis, reservoir and borrow materials. The structural geological studies also carried out due to stability and safety of dam on their abutments reservoir and seismicity. Existence of a fault, high permeable zone at dam foundation and the thickness of alluvium at dam axis, are the most engineering geological issues that cause change on dam type selection. In the feasibility phase, the dam type was chosen as the concrete face rock-fill dam, because of state of engineering geological properties of dam site. However, in the design phase dam type has been changed as a rock-fill with a clay core.

Evaluation Indices and Design Method to Determine the Rolling Density of Dam Shell Sandy Gravel Material

AbstractSandy gravel dams with clay core walls are a widely used dam type, and the rolling density of sandy gravel material is evaluated by the relative density Dr. Consequently, designing the opti...

Dam type and lake location characterize ice-marginal lake area change in Alaska and NW Canada between 1984 and 2019

Abstract. Ice-marginal lakes impact glacier mass balance, water resources, and ecosystem dynamics and can produce catastrophic glacial lake outburst floods (GLOFs) via sudden drainage. Multitemporal inventories of ice-marginal lakes are a critical first step in understanding the drivers of historic change, predicting future lake evolution, and assessing GLOF hazards. Here, we use Landsat-era satellite imagery and supervised classification to semi-automatically delineate lake outlines for four ∼5-year time periods between 1984 and 2019 in Alaska and northwest Canada. Overall, ice-marginal lakes in the region have grown in total number (+183 lakes, 38 % increase) and area (+483 km2, 59 % increase) between the time periods of 1984–1988 and 2016–2019. However, changes in lake numbers and area were notably unsteady and nonuniform. We demonstrate that lake area changes are connected to dam type (moraine, bedrock, ice, or supraglacial) and topological position (proglacial, detached, unconnected, ice, or supraglacial), with important differences in lake behavior between the sub-groups. In strong contrast to all other dam types, ice-dammed lakes decreased in number (six fewer, 9 % decrease) and area (−51 km2, 40 % decrease), while moraine-dammed lakes increased (56 more, 26 % and +479 km2, 87 % increase for number and area, respectively) at a faster rate than the average when considering all dam types together. Proglacial lakes experienced the largest area changes and rate of change out of any lake position throughout the period of study and moraine-dammed lakes which experienced the largest increases are associated with clean-ice glaciers (&lt;19 % debris cover). By tracking individual lakes through time and categorizing lakes by dam type, subregion, and topological position, we are able to parse trends that would otherwise be aliased if these characteristics were not considered. This work highlights the importance of such lake characterization when performing ice-marginal lake inventories and provides insight into the physical processes driving recent ice-marginal lake evolution.

Исследование амплитудно-частотных характеристик вязкоупругого тела типа плотины при установившихся вынужденных гармонических колебаниях

The article discusses the amplitude-frequency response of a viscoelastic body of the dam type, under steady-state forced harmonic vibrations. An important factor is the determination of the number of frequencies and resonance peaks that arise in the process of harmonic effect of the water body on the dam. The use of the finite element method (FEM) for the numerical solution of dynamic problems allows, by expanding the solution in terms of eigenmodes and frequencies, to reduce the original problem to a system of separated linear integro-differential equations with respect to the sought parameters of generalized functions. The process of the influence of viscoelastic properties of the dam material on the resonance curves that arise under harmonic loads of different frequencies at different dimensions of the foot of the dam is investigated. The analysis of the curves of the amplitude-frequency responses of a dam-type viscoelastic body, under steady-state forced harmonic oscillations, showed that the occurrence of resonance peaks depends on the viscoelastic properties of the dam body and the dimensions of the foot of the dam. The main resonance peaks occur at frequencies less than the sixth eigenfrequency, as a result of which a further increase in the number of eigenmodes in the expansion does not introduce any significant changes in the amplitude of the distribution of resonance curves of the amplitude-frequency response of the dam.

Potensi Erosi Buluh Akibat Mata Air Pada Bendungan (Studi Kasus : Bendungan Titab)

The dam is one of the water infrastructures that can function as conservation, utilization, and control of thedestructive power of water. Titab Dam is one of the dams in Indonesia that has multifunction as irrigationwater, raw water and hydropower. This dam is a type of rock fill dam with an upright core which has a peaklength of 210 m, a width of 12 m, and a height of 78 m from the deepest foundation. This dam was built withrelatively complex geological conditions and landslides occurred on the spillway walls and springs were foundin the landslides so it was necessary to analyze the potential for piping due to the presence of springs. Thisstudy examines the potential for piping due to the influence of springs near the dam. The study was conductedbased on instrument observations during the inundation period from 2016 to 2019. The analysis was carriedout by calculating the acceptance criteria (KP) for seepage and seepage index (Qi) to determine seepagebehavior in the dam body and a safety factor analysis (FK) for piping hazards was carried out by comparingthe hydraulic gradient based on piezometer instrumentation readings and the hydraulic gradient of the dambody core material. Based on the calculation of the seepage acceptance criteria and the seepage index, theseepage that occurs in the Titab Dam is not safe because it exceeds the requirements, the average seepageoccurs is 6.350 &gt; 0.56 liter/minute/m and Qi &gt; 1. However, the analysis of the safety factor of piping hazardis still safe that is equal to 8,390 &gt; 4.

Nonlinear Behaviour of Concrete Buttress Dams under High-Frequency Excitations Taking into Account Topographical Amplifications

Concrete buttress dams could potentially be susceptible to high-frequency vibrations, especially in the cross-stream direction, due to their slender design. Previous studies have mainly focused on low-frequency vibrations in stream direction using a simplified foundation model with the massless method, which does not consider topographic amplifications. This paper therefore investigates the nonlinear behaviour of concrete buttress dams subjected to high-frequency excitations, considering cross-stream vibrations. For comparison, the effect of low-frequency excitations is also investigated. The influence of the irregular topography of the foundation surface on the amplification of seismic waves at the foundation surface and thus in the dam is considered by a rigorous method based on the domain-reduction method using the direct finite element method. The sensitivity of the calculated response of the dam to the free-field modelling approach is investigated by comparing the result with analyses using an analytical method based on one-dimensional wave propagation theory and a massless approach. Available deconvolution software is based on the one-dimensional shear wave propagation to transform the earthquake motion from the foundation surface to the corresponding input motion at depth. Here, a new deconvolution method for both shear and pressure wave propagation is developed based on an iterative time-domain procedure using a one-dimensional finite element column. The examples presented showed that topographic amplifications of high-frequency excitations have a significant impact on the response of this type of dam. Cross-stream vibrations reduced the safety of the dam due to the opening of the joints and the increasing stresses. The foundation modelling approach had a significant impact on the calculated response of the dam. The massless method produced unreliable results, especially for high-frequency excitations. The free-field modelling with the analytical method led to unreliable joint openings. It is therefore recommended to use an accurate approach for foundation modelling, especially in cases where nonlinearity is considered.

3D analysis of the 174-m high Quxue asphalt-core rockfill dam in a narrow canyon

The site for the high Quxue Dam has a narrow canyon with very steep abutments and complex geology in Sichuan Province, China. Various types of embankment and concrete dams were considered and an asphalt-core embankment dam (ACED), 174 m high, was selected. The asphalt core is a slender impervious element in an embankment dam and some concerns have been raised about the reliability and safety of the asphalt-core type of dams (ACEDs). This paper presents the case study of the highest asphalt core dam ever built and presents measured and numerical analyses of the core deformations. A 3D non-linear FE analysis has been performed for the Quxue Dam, and the results have been compared with those computed by a 2D analysis to study the effects of the narrow canyon. The computed results are compared with the monitoring data from dam construction and first impoundment. The maximum settlement measured inside the embankment during construction was only about 0.7 m due to the good basaltic rockfill used and the heavy compaction in layers of only 1.0 – 1.2 m thickness. The results of the 3D analysis agree well with the measured downstream displacements and the deflected shape of the thin asphalt core during impoundment, while the 2D analysis overpredicted the maximum displacement by a factor of about two. At a reservoir level 3 m below full supply level, the maximum measured downstream core displacement was only about 80 mm due to the stiff rockfill and the restraining effects of the abutments in the narrow valley.The rockfill behaviour was modelled by the constitutive relationship proposed by Duncan and Chang (1970). The rockfill parameters were determined by laboratory tests prior to construction and were adjusted to better match field observations of vertical settlements during construction. As asphalt concrete exhibits pronounced visco-elastoplastic behaviour, the material modelling was based on long-term triaxial creep tests on samples drilled out of the dam core. The performance monitoring and numerical analysis results for the record-high Quxue ACED document that the concerns expressed about the asphalt core safety and behaviour is not warranted. The asphalt core type of dam is suitable even for high ACEDs in narrow valleys with steep abutments.

Assessing the Vertical Displacement of the Grand Ethiopian Renaissance Dam during Its Filling Using DInSAR Technology and Its Potential Acute Consequences on the Downstream Countries

The Grand Ethiopian Renaissance Dam (GERD), formerly known as the Millennium Dam, is currently under construction and has been filling at a fast rate without sufficient known analysis on possible impacts on the body of the structure. The filling of GERD not only has an impact on the Blue Nile Basin hydrology, water storage and flow but also poses massive risks in case of collapse. Rosaries Dam located in Sudan at only 116 km downstream of GERD, along with the 20 million Sudanese benefiting from that dam, would be seriously threatened in case of the collapse of GERD. In this study, through the analysis of Sentinal-1 satellite imagery, we show concerning deformation patterns associated with different sections of the GERD’s Main Dam (structure RCC Dam type) and the Saddle Dam (Embankment Dam type). We processed 109 descending mode scenes from Sentinel-1 SAR imagery, from December 2016 to July 2021, using the Differential Synthetic Aperture Radar Interferometry technique to demonstrate the deformation trends of both—the GERD’s Main and Saddle Dams. The time series generated from the analysis clearly indicates different displacement trends at various sections of the GERD as well as the Saddle Dam. Results of the multi-temporal data analysis on and around the project area show inconsistent subsidence at the extremities of the GERD Main Dam, especially the west side of the dam where we recorded varying displacements in the range of 10 mm to 90 mm at the crest of the dam. We conducted the current analysis after masking the images with a coherence value of 0.9 and hence, the subsequent results are extremely reliable and accurate. Further decomposition of the subsiding rate has revealed higher vertical displacement over the west side of the GERD’s Main Dam as compared to the east side. The local geological structures consisting of weak zones under the GERD’s accompanying Saddle Dam adds further instability to its structure. We identified seven critical nodes on the Saddle Dam that match the tectonic faults lying underneath it, and which display a varying degree of vertical displacements. In fact, the nodes located next to each other displayed varying displacement trends: one or more nodes displayed subsidence since 2017 while the other node in the same section displayed uplift. The geological weak zones underneath and the weight of the Saddle Dam itself may somewhat explain this inconsistency and the non-uniform vertical displacements. For the most affected cells, we observed a total displacement value of ~90 mm during the whole study period (~20 mm/year) for the Main Dam while the value of the total displacement for the Saddle dam is ~380 mm during the same period (~85 mm/year). Analysis through CoastSat tool also suggested a non-uniformity in trends of surface water-edge at the two extremities of the Main Dam.

30 Calf Performance and Sex Ratios in Second Generation Reciprocal Nellore-angus Crosses

Abstract The objectives of this study were to analyze calf weight and sex distribution differences in reciprocal F2 Nellore-Angus calves (n = 559) born 2010–2015 and calves out of these F2 females through 4 yr age (n = 469) born 2012–2018. The F2 animals were produced by 4 F1 parent type combinations from Nellore-sired (NA) vs. Angus-sired (AN) sires and dams. Weight traits were analyzed using mixed models, and sex distribution was analyzed through PROC GLIMMIX in SAS. Sire type and dam type affected birth weight (P &amp;lt; 0.05) but not weaning weight of the F2 calves. However, the interaction between sire type and dam type accounted for weaning weight differences (P = 0.038). Birth weight averaged 3.5 kg heavier from NA vs. AN sires, and 2.4 kg heavier from NA vs. AN dams. Weaning weight displayed a different pattern than observed in birth weight with the heaviest calves being NAAN (224.5 ± 3.7 kg) and lightest being ANAN (215.9 ± 3.9 kg). Sire type accounted for important variation (P = 0.036) in the calf sex distribution at birth among F2 calves. Percentage males at birth exceeded the expected ratio for NA-sired calves (66.6%, n = 168) but not for AN-sired calves (49.9%, n = 105). The sire and dam type main effects in the F2 females did not influence weight traits or sex distribution in their calves (from predominantly Angus sires). However, the interaction of sire type x dam type x sex showed a trend in birth weight (P = 0.080) and importance for weaning weight (P = 0.010) where only from ANNA and NANA dams were males heavier than females. These results suggest that some of the calf weight reciprocal differences typically observed among F1 Bos indicus-Bos taurus crosses can persist in later generations.