**3.4 Reinforced piled embankment as a Foundation of Roads on soft soils in the Brazilian Amazonia**

There are four cases to be reported here (Points 4 to 7 of **Figure 1**). All cases dealt with the construction of a road in a location with a thick layer of soil with low bearing capacity, in which it would be uneconomical to purge this material.

*Challenges in the Construction of Highways in the Brazilian Amazonia Environment: Part II… DOI: http://dx.doi.org/10.5772/intechopen.105017*

#### **Figure 10.**

*Surface condition of the stabilized base with asphalt emulsion after 20 months of execution [5].*

#### **Figure 11.**

*Reinforced piled embankment executed for crossing watercourses. a) Stratigraphic profile; b) arrangement of the piles and the geogrid reinforcement, in cross-section; c) and d) installation of the geogrid on the capitals of the piles (photo: Maccaferri [6]).*

**Figure 11** shows the implementation details of the project (Point 4 of **Figure 1**). The largest thickness of the very soft organic clay layer observed was 7.55 m (**Figure 11a**), with a penetration resistance index (NSPT) value under net energy of 72% (N72, typical of Brazilian energy test) with an average of 1/45 blows/30 cm, on which a road embankment and bridge abutments (with a height of 6.65 m) were built to cross

a watercourse called "Igarapé Miri" in the State of Pará. **Figure 11b** indicates the solution adopted. It entailed precast reinforced concrete piles, with square sides of 20 cm (to support the embankment) and 25 cm (to support the embankment and the bridge abutments), that were 8 m in length, spaced every 1.5 m, in both directions in plan view. On average, the pile tips were embedded at least 1 m into the resistant layer of very dense silty sand. **Figure 11c** and **d** shows a high stiffness geogrid for reinforcement of the embankment, installed over the cap piles, with the function of distributing the loads of the embankment and the bridge abutments for the piles.

**Figure 12** shows the implementation details of the project (Point 5 of **Figure 1**). The largest thickness of the very soft organic clay layer was 13.30 m (**Figure 12a**), with a mean N72 value of 1/70 blows/30 cm (region under the tidal influence, located in mangrove), on which a road embankment and bridge abutments (with a maximum height of 4 m) were built to cross a small watercourse in the city of Abaetetetuba, Pará State.

**Figure 12b** indicates the solution adopted: There were used precast piles of reinforced concrete, with square sections of 35 cm on the side, 20 m in length, spaced every 3 m in plan view. On average, the tips of the piles were embedded approximately 5 m inside the resistant layer of very dense sand. A geogrid was used to reinforce the embankment, and a geotextile of high stiffness was placed between the geogrid and the top of the pile cap to avoid tearing of the geogrid when it was subjected to the

#### **Figure 12.**

*Reinforced piled embankment built for crossing the watercourse in the city of Abaetetetuba, Pará state. a) Stratigraphic profile; b) arrangement of the piles and the geogrid reinforcement, in cross-section; c) installation of piles in the abutment bridge (photo: NS Campelo).*

*Challenges in the Construction of Highways in the Brazilian Amazonia Environment: Part II… DOI: http://dx.doi.org/10.5772/intechopen.105017*

embankment surcharge. **Figure 12c** shows the piles supporting the retaining wall of the bridge abutments.

**Figure 13** shows the details of the project (Point 6 of **Figure 1**), a connection road to state highway PA-150, in the State of Pará. The largest thickness of the very soft organic clay layer observed was 8.00 m (**Figure 13a**), with a mean N72 value of 1/45 blows/30 cm, on which a road embankment and an abutment bridge were built with a height of 2.3 m. **Figure 13b** indicates the adopted solution. There were used precast reinforced concrete piles, with 25 cm square side, spaced every 1.5 m. On average, the tips of the piles were embedded approximately 1 m inside the resistant layer of very hard silty clay. A geogrid and a geotextile were placed at the top of the pile caps.

**Figure 14** shows the implementation details of the project (Point 7 of **Figure 1**). The highest thickness of the soft clay silt layer observed was 5.75 m (**Figure 14a**), with a mean N72 value of 3 blows/30 cm, on which a road embankment with a height of 4–6 m was built, in the *várzea* region, on the BR-319 federal highway, State of Amazonas. **Figure 14b** indicates the solution adopted: root-type piles 40 cm in diameter, spaced every 2 m. A geogrid was used to reinforce the embankment, and a geotextile mat of high rigidity was placed between the geogrid and the top of the pile capitals to avoid tearing the geogrid.

#### **Figure 13.**

*Connection road to state highway PA-150, state of Pará. a) Stratigraphic profile; b) arrangement of the piles and the geogrid reinforcement, in cross-section.*

#### **Figure 14.**

*Reinforced piled embankment executed in the várzea region on the BR-319 federal highway, state of Amazonas. a) Stratigraphic profile; b) arrangement of the piles and the geogrid reinforcement, in cross-section.*
