Field characterization of problematic earthfills, by DMT. A case history Nuno Cruz - MOTA-ENGIL; Universidade de Aveiro, Portugal Isabel Caspurro - Estradas de Portugal, Portugal Sofia Guimarães & Cristina Cunha Gomes - COBA, Portugal António Viana da Fonseca - Universidade do Porto, Portugal

General Conditions  Some weeks after its opening - signs of movement around the hydraulic cross, settlements on the platform and sidewalks and tension cracks along the slopes, showing a general instability of the earthfill  Earthfill of 150m long with 6,0m and 4,5m high on the right and left sides  Cross a water line, where a hydraulic cross ensures its drainage  Located in ring surrounding Oliveira do Bairro at the Centre- North of Portugal

Mechanical Caracterization 0,0 – 3,0m – Very loose (qd < 2MPa)0,0 – 3,0m – Very loose (qd < 2MPa) 3,0 – 5,5 – Loose (2 – 4MPa)3,0 – 5,5 – Loose (2 – 4MPa) 5,5 – 6,0 (foundation) – Loose to very loose (1 – 3MPa)5,5 – 6,0 (foundation) – Loose to very loose (1 – 3MPa) > 6,0 – Medium compact (> 7,5 MPa)> 6,0 – Medium compact (> 7,5 MPa)  8 DPL (homogeneity quick testing )

Mechanical Caracterization  5 DMT Table 1 – Results of DMT tests * - Earthfill; ** - Foundation DMT Depth (m) Type of soil IDID  (kN/m 3 ) M (MPa) >5.5 Silt-Silty sand* Silt sand-Sand** >5.2 Silt-Silty sand* Silty sand* Sand* Silt sand-Sand** > 4.5 Silt sand-Sand** Sand** Sand** >4.5 Silty sand* Silt-Silty sand* Silt-silt sand** >3.5 Silty sand-Sand** Sand**

Background (Cruz et al. 2006) Table 1 – Results of DMT tests * - Earthfill; ** - Foundation

Table 1 – Results of DMT tests * - Earthfill; ** - Foundation Background (Cruz et al. 2006) Moduli

Table 1 – Results of DMT tests * - Earthfill; ** - Foundation Density

RESULTS ID – Material Index Table 1 – Results of DMT tests * - Earthfill; ** - Foundation SOME IMPORTANT TRENDS (Cruz et al., 2006): a) ID > 4 Poorly graded sandy soils b) ID=[ ] Adequate soils (SM-SC), c) ID=[ ] Soils with fine content higher than 20% and low plasticity d) ID < 1.0 Soils with high fine content and plasticity

Table 1 – Results of DMT tests * - Earthfill; ** - Foundation SOME IMPORTANT TRENDS (Cruz et al., 2006): a) Unit weight (+ 1 kN/m3) has no sensitivity to be used as a quantitative control parameter b) Can be used qualitatively to check other parameters, by its order of magnitude c) In the present situation results are within 16 and 18 kN/m3, much lower than the usually accepted for this type of works RESULTS Unit Weight

RESULTS Constrained Modulus Table 1 – Results of DMT tests * - Earthfill; ** - Foundation SOME IMPORTANT TRENDS (Briaud & Miran, 1992; Marchetti, 2001; Cruz et al., 2006) a)Good adaptability of M as a design modulus, since pavement engineering rely on a sub-grade deformability modulus b)Higher execution rates, comparing to the most common testing procedures (ex. plate load tests) c)Much higher sensitivity when using M and OCR than with ED and KD. d)Typically M profiles show a peak value below the top of the layer. The distance between peaks give indication of compaction thickness

RESULTS Table 1 – Results of DMT tests * - Earthfill; ** - Foundation Globally CBR < 5% Upper level DMT 5 – 10 < CBR < 15%

Stability Analysis Table 1 – Results of DMT tests * - Earthfill; ** - Foundation

SOLUTIONS  Rockfill cover of, at least, 3.5m width over the main slope  Indented interface of the rockfill with the main earthfill  Rockfill embedment of 1.5m into the foundation ground  Soil substitution of the first layer in one meter, by more adequate soils, followed by compaction in 0,30cm layers with tight control.

SOLUTIONS Table 1 – Results of DMT tests * - Earthfill; ** - Foundation

CONCLUSIONS  Very useful for “post-execution” control  Good alternative to control selected earthfill materials and respective mechanical behaviour  Qualitative control of compaction levels by deriving unit weight values through depth;  Definition of a rigidity modulus of the earthfill (layer by layer), very important for design considerations  Control of thickness of compaction layers

Thank you for your attention. I hope to have been useful