<p>This paper evaluates the long-term hydro-geotechnical behavior of the Dom Marco Ring Dam, with emphasis on seepage through its sedimentary rock foundation and on the effectiveness of the rehabilitation measures implemented after the 1973 accident. Design, construction, geological investigation, rehabilitation, and monitoring records were synthesized, including 43 boreholes, 70 foundation drains, 16 piezometers, and 136 deep anchors installed during the post-accident works. Two-dimensional finite-element seepage analyses were performed in SEEP/W (GeoStudio), using hydraulic parameters constrained by variable-head field permeability tests, historical technical reports, and literature ranges for the site materials. The models were calibrated against historical piezometric heads and drain discharges, mainly for 1975 and 1978, by adjusting section-dependent hydraulic conductivity, anisotropy ratio <InlineEquation ID="IEq1"> <EquationSource Format="TEX">${k}_{y}/{k}_{x}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>k</mi> <mi>y</mi> </msub> <mo stretchy="false">/</mo> <msub> <mi>k</mi> <mi>x</mi> </msub> </mrow> </math></EquationSource> </InlineEquation>, and drain performance. Results show that the drainage system is pivotal for foundation performance, reducing uplift pressures by roughly 60–70% when fully functional. The calibrated models also indicate section-dependent hydraulic anisotropy (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">${k}_{y}/{k}_{x}\hspace{0.17em}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>k</mi> <mi>y</mi> </msub> <mo stretchy="false">/</mo> <msub> <mi>k</mi> <mi>x</mi> </msub> <mspace width="1.69998pt" /> </mrow> </math></EquationSource> </InlineEquation>≈ 0.3–2.0) and heterogeneous flow paths governed by stratigraphic contrasts, fault/fracture zones, and dam-rock contact conditions. Long-term monitoring suggests progressive clogging of some drains, likely associated with fine-particle transport in the weathered sedimentary foundation, although piezometric levels remain acceptable where drainage remains functional. The study identifies the foundation zones controlling seepage, quantifies the hydraulic benefits provided by the drainage system, and provides practical guidance for monitoring, maintenance, and rehabilitation strategies in concrete dams founded on heterogeneous sedimentary soft rocks.</p>

Hydro Geotechnical Assessment and Seepage Analysis of the Dom Marco Ring Dam

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2026年7月9日

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Luigi Nascimento Pelizzoli,
William Fedrigo,
Luiz Antônio Bressani,
Diones Uiliam Barboza

摘要

This paper evaluates the long-term hydro-geotechnical behavior of the Dom Marco Ring Dam, with emphasis on seepage through its sedimentary rock foundation and on the effectiveness of the rehabilitation measures implemented after the 1973 accident. Design, construction, geological investigation, rehabilitation, and monitoring records were synthesized, including 43 boreholes, 70 foundation drains, 16 piezometers, and 136 deep anchors installed during the post-accident works. Two-dimensional finite-element seepage analyses were performed in SEEP/W (GeoStudio), using hydraulic parameters constrained by variable-head field permeability tests, historical technical reports, and literature ranges for the site materials. The models were calibrated against historical piezometric heads and drain discharges, mainly for 1975 and 1978, by adjusting section-dependent hydraulic conductivity, anisotropy ratio ${k}_{y}/{k}_{x}$ $k_{y} / k_{x}$ , and drain performance. Results show that the drainage system is pivotal for foundation performance, reducing uplift pressures by roughly 60–70% when fully functional. The calibrated models also indicate section-dependent hydraulic anisotropy ( ${k}_{y}/{k}_{x}\hspace{0.17em}$ $k_{y} / k_{x}$ ≈ 0.3–2.0) and heterogeneous flow paths governed by stratigraphic contrasts, fault/fracture zones, and dam-rock contact conditions. Long-term monitoring suggests progressive clogging of some drains, likely associated with fine-particle transport in the weathered sedimentary foundation, although piezometric levels remain acceptable where drainage remains functional. The study identifies the foundation zones controlling seepage, quantifies the hydraulic benefits provided by the drainage system, and provides practical guidance for monitoring, maintenance, and rehabilitation strategies in concrete dams founded on heterogeneous sedimentary soft rocks.