Introduction

Geosynthetic-reinforced pile-supported (GRPS) embankments were developed for areas with compressible soil and subsidence.

Up to date, nearly all GRPS piled embankments in the world are dry, and therefore, no measurements were available of those structures where the embankment was partially or completely submerged into groundwater.

As a result, in wet conditions, unsustainable and unnecessarily expensive solutions such as concrete slabs are chosen.

This research quantified the influence of groundwater in the reinforced embankment, due to extreme rain (climate change) or a high groundwater level (subsidence, sea level rise).

Additionally, an analytical calculation procedure was developed to take groundwater into account.

Activities conducted

1. Field measurements
2. Model tests
3. Development analytical calculation procedure 
4. Finite Element Calculations

1. Field measurements

A regional road in the Krimpenerwaard, Netherlands, was constructed on a geotextile-reinforced pile-supported embankment. A section was monitored for four years. Geotextile strains, the changing groundwater level and settlements were measured.

GRPS embankment in the Krimpenerwaard, Netherlands. Installation of geotextile reinforcement, at the bottom of the embankment. (a) across road way, (b) along road way. The concrete pre-cast pile caps were covered by a non woven for protection of the reinforcement

Installation monitoring

Cross section test section, the ground water level was measured with pore pressure transducers. The groundwater table varied strongly.

Measured groundwater  level (ppt1). Air bubbles disturbed the measurements of ppt6.

Measured strains in the geotextile reinforcement

The geotextile strains did not respond clearly to the changing groundwater table 

The geotextile strains seem to relate with the average day temperature

The measured geotextile (GR) strains are smaller than the values calculated with the Concentric Arches model, that is utilized by the Dutch Design Guideline CUR226 for basal reinforced piled embankments

The analytical Concentric Arches model (van Eekelen et al., 2013 and 2015). The load is transferred via the arches towards the subsurface and pile caps. 

Conclusions field experiments

• The analytic Concentric Arches model calculates larger geotextile strains than measured and therefore gives a safe prediction
• The groundwater level does not affect the geotextile strains
• The air temperature affects the geotextile strains
• For this case, with these geotextiles, and this high ground water level, design guideline CUR226 for basal reinforced piled embankments, that applies the Concentric Arches model, gives a safe design.

2. Model tests

Model tests on a geosynthetic-reinforced piled embankment, inducing a varying groundwater table in the fill.

A series of small-scale experiments were conducted.

The fill consisted of broken demolition waste. Its properties were determined in large-diameter triaxial tests.

Triaxial tests on fill samples with a diameter of 0.45 m.

The tests showed that a higher groundwater level reduces the total load, including load part A (the soil arching).

The reduction mainly results from Archimedes' uplift forces, and immediately recovers upon lowering the groundwater.

Measured soil arching (load part A in kN/pile) compared to analytical calculations, including the Principle of Archimedes

At some locations, the groundwater rise resulted in a heave of the geosynthetic, which also matched with the Principle of Archimedes.

Measured (z2, z3) and calculated deflection of the geosynthetic between adjacent piles. Calculations included the Principle of Archimedes.

3. Extension of the analytical model to include groundwater

Including the Principle of Archimedes in the existing analytical calculation models give a good match with the measurements. 

The Concentric Arches model provides the closest match to the measurements.  

The geosynthetic strains did not respond significantly to changes in groundwater. This matches the field measurements presented above.

4. Finite Element Calculations

Detailed Finite Element Model (FEM) Analyses were made to validate the Concentric Arches model. This resulted in a journal paper (Lee et al., 2021). Furthermore, dynamic analyses were made by extending this FEM model.

Consortium

Private partners

• Solmax / TenCate

Knowledge Institutes

• Deltares, Delft, The Netherlands
• Kyung Hee University, Giheung-gu, Yongin-si, Gyeonggi-do, Republic of Korea

Products

The official products of this TKI project are:

More information?

Please, contact Suzanne.vanEekelen@deltares.nl.