http://repositorio.lnec.pt:8080/jspui/handle/123456789/47 Sat, 04 Apr 2026 20:59:30 GMT 2026-04-04T20:59:30Z http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018736 Yielding of Rockfill under Relative Humidity Control Manso, J.; Marcelino, J.; Caldeira, L. This paper presents a fundamental study on the evolution of particle breakage during triaxial compression tests, focusing on the effect of total suction. This analysis was based on triaxial compression tests, performed with RH control. The tested material comes from the sta- bilizing shoulders of Montesinho CFRD and three RHs were stud- ied: 50%, 75%, and 100%. Experimental procedures are presented, with details of the prep- aration of specimens, and stress–suction paths are given. Special at- tention is given to the compaction and the application of different suctions. First, the influence of confining stress is analyzed. Results show that the confining stress led to a contractive behavior, de- creasing dilatancy. For a confining stress of 0.75 MPa, the dilatancy almost disappears. Considering the analyzed values of total suction, the maximum difference of deviatoric stress between specimens with different values of total suction was obtained when the mate- rial reached the peak condition, and was attenuated for larger values of axial strain. By determining the volumetric and axial strains, as well as the shear strains, it is possible to plot the stress paths and the plastic strain increment vectors. It is also possible to separate the elastic and plastic components. This allows for confirmation that speci- mens compress volumetrically during the initial part of the loading curve, up to a certain level of stress. Near the peak deviatoric stress, the material exhibits dilatancy, probably because of particles fitting together intricately, as a result of particle breakage and rearrangement. Another aspect analyzed was particle breakage; this tends to in- crease with the confining stress and the decrease in total suction. To assess the amount of breakage during triaxial loading, the Einav breakage factor was determined. The results corroborate the con- clusion that the values of the breakage factor increase with confin- ing stress and with the decrease of total suction. A 10% increase was observed in the breakage factor when the total suction was de- creased from 93.86 to 0 MPa. Dilatancy is described in terms of stress ratio, particle breakage, and average confining stress, and the experimental results show thatthe major effect of the decrease of total suction is contraction of the peak failure envelopes in the p–q plane by about 5.5% (for mean stresses up to 2.5 MPa). At the end of the tests, dilatancy was prac- tically independent of suction, decreasing only with confining stress to 1/3 (for the studied confining stresses: 0.20, 0.40, and 0.75 MPa). The research findings indicate that suction has a limited effect on the measurement of dilatancy. In any case, its effects, al- though noticeable and broadly consistent with observations in other tests with controlled suction on weak soils and gravels, are substan- tially smaller than the rest of the variables mentioned. Sat, 01 Feb 2025 00:00:00 GMT http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018736 2025-02-01T00:00:00Z http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018548 Southern Expansion of the Cerro do Lobo Waste Facility. Mechanical Characterization of Soil-rockfill Mixtures Brito, A.; Manso, J.; Marcelino, J.; Galrão, R.; Oliveira, M. Carlos Pina, Eliane Portela e Laura Caldeira The Southern Expansion of the Cerro do Lobo Waste Facility, inserted in the Neves-Corvo Copper and Zinc Mining Concession, is located in Baixo Alentejo, district of Beja, covering the municipalities of Castro Verde and Almodôvar, Portugal. During the operational phase, the mining waste will be deposited vertically, in stages. At the same time, the deposition area will expand approximately 10%. This enlargement includes the southern expansion of the tailings dam. This dam will contain waste up to level 8 (at elevation 272 m), has a maximum height of 17 m, and its walls have slopes of 1(V):2.5(H) upstream, to allow the application of geosynthetics, and 1(V):2(H) downstream. The body of the dam consists of materials resulting from excavation inside the reservoir (rockfill and soil-rockfill mixtures) and a transition layer (0.30 m thick) to support the materials that constitute the waterproofing system. Soil-rockfill mixtures (SRM) represent an environmentally friendly material that capitalises on the reuse of the material excavated. Recently, it has been giving particular attention to SRM by the fact that many embankments, constructed with such materials, have presented a poor performance and required, in many cases, the implementation of corrective measures. To improve the knowledge about the mechanical behaviour of soil-rockfill mixtures applied in tailings dams and also to prevent the use of a less capable material behaviour, LNEC, in cooperation with the Dam Owner, carried out an experimental study. This paper presents the results of the performed experimental program, which involved undrained triaxial tests among others. Tue, 01 Apr 2025 00:00:00 GMT http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018548 2025-04-01T00:00:00Z http://repositorio.lnec.pt:8080/jspui/handle/123456789/1017580 Designing a pre-load embankment for the construction of a stage over a sanitary landfill founded in soft soils Brito, A.; Carreto, J. Nuno Guerra; Manuel Matos Fernandes; Cristiana Ferreira; António Gomes Correia; Alexandre Pinto; Pedro Sêco e Pinto For World Youth Day event in 2023 (JMJ), the organizing committee selected an area in Parque das Nações that met the imposed requirements, notably in terms of area (for 1 million spectators) and proximity to the Lisbon center. This area, on the other hand, has the distinction of being a sanitary landfill, which was sealed in 1997 as part of the EXPO98 interventions, and which previously, in 1995, experienced a large-scale landslide in the direction of the river, with a front of 300 m of extension, enveloping the foundation up to significant depths. The fundamental cause of the landslide, according to studies undertaken at the time, was the low undrained strength of the foundation's soft soils that were still in the subconsolidation phase, particularly at the deepest levels. Considering this scenario, LNEC performed limit equilibrium stability analyses as well as three-dimensional stress and strain finite-element analyses to estimate the magnitude and evolution of the settlements of the JMJ stage to be built in the southern area. The analyses carried out, the results of which are presented in the article, revealed the need of a pre-load embankment and were used to define criteria for the constructive phasing of the work, which was inherently dynamic and based on the outcomes of the monitoring system installed on site. Finally, values obtained from the monitoring system installed during the construction phase are compared to the values estimated during the design phase. Thu, 01 Aug 2024 00:00:00 GMT http://repositorio.lnec.pt:8080/jspui/handle/123456789/1017580 2024-08-01T00:00:00Z http://repositorio.lnec.pt:8080/jspui/handle/123456789/1015789 Compaction Control of Soil-Rock Mixtures at Odelouca Dam Brito, A.; Caldeira, L. Recently, soil-rock mixtures are being used in the construction of embankment dam shoulders. This situation represents new challenges to compaction techniques and their control as well as to the determination of the characteristics of the fill that results from the compaction method, as those characteristics suffer important changes according to the relative percentage of the existing fractions. For the execution control of the soil-rock mixtures from the Odelouca dam borrow areas, presently being constructed at South of Portugal, a series of vibratory compaction tests and rammer compaction tests were performed to estimate reference values for the maximum dry density and optimum water content of these materials. Odelouca dam is a zoned earth fill dam, with 76 m height with clayey soil at the core and weathered schist with a significant fraction of oversized particles at the slopes. This paper presents the results of these tests. Following the methodology, developed in 1994, by Torrey & Donaghe, a set of correction equations of the Proctor reference values (obtained on a partial finer fraction passing in the ¾” sieve) for the extrapolation of the control properties of integral material for schistose material is presented. Additionally a new methodology based in different parameters is proposed. Mon, 01 Sep 2008 00:00:00 GMT http://repositorio.lnec.pt:8080/jspui/handle/123456789/1015789 2008-09-01T00:00:00Z