Foros do Mocho Road-Dam Consolidation

Earth Dam located at Montargil (Portugal), was severely damaged by intense flooding on December 2022. It had to be intervened to allow the reestablishment of its top road, that is the main access to Foros do Mocho. This project included the installation of Shaft-grouted Ductile Iron Driven Piles, for dam stabilization and road structural support.

Project Detail

Micropiling for earth Dam consolidation and Road support.

Client

OpenVias and NOVPro

Date

2024

Estimate Budget

Industries

LOCATION

Foros do Mocho, Montargil – Ponte de Sor (Portugal)

The municipal road (CM1062) is the main access to and from the small village and was cut to traffic due to erosion and partial collapse of the dam. Requalification of the Road-Dam by means of landfill consolidation using micropiles. A total of 126 piles were installed: 88 vertical and 38 inclined (25°) piles. These were all Ductile Iron Piles of 170/7,5mm, driven by wet method, and having a 270mm conical shoe. All iron material was supplied by Tirol Rohre GmbH (TRM). As per the designer requirement, one test pile and 4 reaction piles were also executed, using the same methodology.

The installation of the shaft-grouted piles requires pumping cement mortar (C25/30, with maximum grain size <4mm) that will fill up the inner and outer (annulus) space of the pile.

Challenges

A narrow working platform created difficulties in locating material and equipment. Positioning of the rig was even more challenging for the inclined (raked) piles. Besides the reduced area available, the production target was ambitious, associated to the urgency of reestablishing this access road.

Pile installation required the mobilization and lifting of 5m length ductile iron pipes. These were coupled to the hydraulic hammer and correct alignment had to be confirmed before and while driving. This operation was more demanding when having the 25° raked piles.

Concrete mix had to be correctly adjusted with the batching plant to have the adequate properties of pumpability and retardant, allowing for prolongated operation. Concrete availability and supply, associated to the far distance to the jobsite, have also created interruptions on the production cycles.

Solution

Shaft-grouted Ductile Iron driven Piles was the selected option to stabilize the earth dam. It is an effective solution to consolidate non cohesive soils and provide deep foundation to civil engineering structures. Micropiles are cost effective and can be installed in a relatively speedy manner. The shaft grouted option offers, in this particular case, better soil consolidation and improves skin friction.

GEO/ARCOS partnership was capable of providing the technical knowledge and skills to install the piles a per project specifications, all of them reaching depths where refusal was observed. The bearing capacity was proven by a static load test preformed onsite, with two loading cycles: up to design load of 326kN (100%) and to 651kN (200%).

Work schedule and concrete supply was carefully programmed, to avoid interruptions and optimize pile installation. Even having many no programmed stops, it was possible to complete all working micropiles (126 units) in one month.

Key Figures

Scope:

A total of 126 Shaft-grouted Ductile Iron Piles: 88 vertical and 38 inclined (25°). These were all of 170/7,5mm and having a 270mm conical pile Shoe.

One vertical test pile and 4 reaction piles.

Achievements:

Maximum production of 14piles/day (170m/day) and average of 10piles/day. Efficient use of pipe with less than 2% wastage. Load bearing capacity proven onsite up to 651kN (200%) with <5mm of residual settlement.

Soil Conditions:

The site soil profile is basically composed by the earth dam, of silty sand soil (NSPT 2-5), from 0 to 9m depth, followed by ≈3m of alluvium silty, partially clayey, Sand (NSPT 9), with dispersed gravel, and a base of compact silty Sand (NSPT 48-60) at an average depth of 12m.

Technologies Used

G3® System

The G3® Soil Stabilization System is a next-generation polymer technology designed to transform non-cohesive soils into stable, predictable environments for excavation and ground engineering. By forming a strong cross-linked network within the soil, the G3® system improves soil cohesion, minimizes fluid loss, and enhances operational efficiency, making it ideal for challenging soil conditions.

G Line

The G Line is a versatile polymer-based soil stabilization system used in geotechnical excavations to support soil structures. It is designed for use in various soil types and conditions, offering efficient mixing, rapid hydration, and compatibility with both fresh and salt water. The G Line components (GMud, GNet, G+) work together to enhance soil cohesion, reduce fluid loss, and promote particle suspension, making it ideal for applications in deep foundation projects.

XG Series

The XG Series, developed by GEO, is a range of innovative products based on a natural polymer for use in drilling and soil stabilization. Designed for high solubility and viscosity control, Cross-Gel XG serves as an efficient drilling fluid with long-lasting stability, effective sediment transport, and continuous reuse capability. The series includes complementary products—XG Break, XG Clean, and XG Shield—to optimize performance, manage fluid viscosity, and maintain polymer structure over extended operations.

Bentonite Suspension

A bentonite suspension system is a mixture of bentonite clay and water, forming a gel-like fluid that exhibits thixotropic properties, meaning it thickens when at rest and becomes more fluid when agitated. This suspension is used primarily in industries like construction, drilling, and geotechnical applications for its ability to provide stability and lubrication.

GelPro

GelPro is a highly soluble anionic polymer that forms a high-viscosity slurry when mixed with water. It hydrates quickly and requires minimal equipment for use, offering immediate application for soil stabilization. GelPro is ideal for stabilizing various geological formations, offering ease of hydration and consistent slurry formation. It can be mixed directly in the excavation or slurry batching plant without the need for pH adjustment or specialized mixers.

GMud Ultra

GMud Ultra is an anionic polymer that creates a high-viscosity slurry upon mixing with water. It hydrates quickly and requires no special equipment, offering fast application in less demanding soil profiles. Designed for use in less complex geological conditions, GMud Ultra simplifies soil stabilization with minimal equipment. For more difficult formations, additional G3 System products are recommended for enhanced performance.

PolyGel

PolyGel is an acrylic anionic polymer, available in dry granular form, known for its excellent hydration and solubility rates. It provides a balanced price-quality solution for soil stabilization. PolyGel is effective in soil stabilization and can be used in conjunction with other G3 System products to meet specific project requirements. It is also environmentally friendly, ensuring reliable results.

Fluid Loss Blockers

GEO’s fluid loss blocker system includes two products, GFiber and GBlock, designed to prevent fluid loss during soil stabilization. Fluid loss can compromise excavation stability, particularly in permeable or fractured soils. GFiber, made from natural mineral fibers, and GBlock, a fast-swelling synthetic polymer, create barriers in the soil to control seepage effectively. This system is compatible with support fluids such as the G3 System, Gline, XG series, Bentonite, and standalone slurries.

Micropile

Micropiles are small-diameter piles made from high-strength materials like carbon steel or ductile cast iron, driven into the ground to provide additional load-bearing capacity for structures. They are ideal for both new construction and foundation reinforcement in existing buildings, especially in areas with weak soil or limited access. Micropiles are often used where traditional foundation methods are impractical, offering a flexible, cost-effective solution with minimal disruption. Their installation requires minimal equipment, making them suitable for tight spaces or urban environments where heavy machinery is not feasible.

Bi-Directional Static Load Test

Bidirectional Static Load Testing (BDLT) is an advanced and efficient method for evaluating the load-bearing capacity of deep foundation piles and barrettes. This innovative testing technique is crucial for projects that require precise measurement of both skin friction and end bearing capacity in high-capacity foundations. The method involves performing full-scale static loading tests that evaluate the load performance of piles under axial compressive loads, which is essential for ensuring the stability and integrity of any foundation system.

Water / Wastewater Treatment

Our comprehensive array of specialized polymers is designed for water, wastewater, and sludge treatment, and all our products meet NSF certification, Halal certification, and applicable local certifications. We take on the challenges of water treatment across multiple sectors, including municipal, industrial, mining, agriculture, construction, civil engineering, and dredging, to ensure water is preserved and reused for the benefit of future generations.