José Muralha, António Batista, Luís Lamas, Juan Mata & Carlos Serra • anchor load cell readings remained largely stable throughout the monitoring period;


• no anomalies were identified during visual inspections conducted during the construction period and throughout the reservoir’s first filling.


5. Final Remarks The Alto Tâmega dam, a double-curvature concrete arch structure on the Tâmega River in northern Portugal, went through design adaptations, mitigation measures and adaptive engineering solutions to ensure structural stability, operational safety, and compliance with international standards, following a major rockslide on the right bank slope during excavation. In fact, in the first semester of 2019, the excavations exposed unforeseen, complex rock mass characteristics, namely changes in fault and discontinuity orientations, that led to the sliding of a large rock wedge on the right bank slope. The adaptations introduced in the dam’s design, to face the consequences of the rockslide that occurred on the slope of the right bank, considered five main components:


• resurfacing of the insertion surface of blocks B8, B10, B12 and B14 to ensure better conditions for supporting and transmitting stress to the rock mass foundation;


• construction of a new concrete structure, to partially restore the geometry and the loading conditions of the rock mass existing before the rockslide;


• extension of the rock mass foundation gallery in the right bank, at elevation 237.5 m, to survey the foundation in depth and promote waterproofing and drainage under the affected area;


• updating of the monitoring plan, including the definition of additional instrumentation to be installed in the new concrete structure, as well as adjustments to monitor the foundation area on the right bank;


• moving the location of the dam’s bottom discharge to the left bank.


These measures were implemented on site without major difficulties. Construction works took place normally, following well-defined planning and strict safety control. The first filling of the reservoir occurred as planned. The phases of construction and of the first filling of the reservoir showed the robustness of the design adjustments. Monitoring data revealed adequate behavior of the dam structure and of the rock mass foundation, namely concerned with small absolute and relative displacements, stable seepage and uplift pressures, and consistent anchor loads, all of which align with the safety requirements established during design and construction phases. The dam has been in operation since February 2024, with very good performance. The comprehensive safety monitoring plan, supported by continuous data analysis, has proven critical in verifying the dam’s behaviour during construction and under reservoir filling conditions. The numerical models developed by Iberdrola and LNEC provided valuable contributions to evaluate the effectiveness of the implemented measures. In summary, the Alto Tâmega dam may be seen as a successful collaboration between designers, contractors, authorities, and monitoring teams in overcoming complex geotechnical and structural challenges. This collaborative approach, reinforced by rigorous monitoring and advanced modelling,


138 | Dam Engineering | Vol XXXIII Issue 3


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100