Embankment Remediation with Stone Facing on D501 State Road
In the Primorje-Gorski Kotar County, on State Road D501, section 002, at station 12+570 km, south of the settlement of Križiće, damage to the roadway and the embankment with stone facing beneath the road – approximately 10.0 m in height, has been observed. Roadway damage is manifested through local settlement and asphalt settlement, while embankment damage is visible as bulging and deformation of the stone facing out of its original plane. Additionally, part of the embankment has experienced stone facing detachment and material loss behind the facing. The affected length of the damage is approximately 60.0 m.
Geotehnical investigation and testing
For the embankment remediation design, engineering-geological and geotechnical investigation and testing were conducted, consisting of:
- Geological and geotechnical field prospecting
- Exploratory drilling
- Engineering-geological field mapping and core identification
- Laboratory testing
- Geophysical testing
- Data processing from previous investigations
As part of the exploration drilling, three boreholes were conducted, each 20.0 m in depth. The boreholes were used to determine the geotechnical characteristics of the site and the foundation soil. Drilling was conducted using continuous coring along the full depth of the boreholes.
Seismic refraction geophysical testing (MASW) was carried out along one profile with a total length of 51.0 m. The result of the MASW test is shown below:
Based on the investigation and testing results, a geotechnical report was made as the basis for the embankment remediation design. The longitudinal geotechnical profile is shown in the figure below.
The geotechnical profile at the site consists of three (3) geotechnical units:
- Geotechnical Unit 1 – Gravelly deposits
- Geotechnical Unit 2 – Clay deposits
- Geotechnical Unit 3 – Limestones
Remediation Measures
The remediation includes the installation of reinforced concrete bored piles with a nominal diameter of D=600.0 mm, spaced approximately 2.50 x 2.50 m, and lengths of L=8.0 and 10.0 m. The reinforced concrete piles, made of concrete with a compressive strength class of C 30/37, are intended to prevent settlement of the future pavement structure and serve as elements to increase the global safety factor against embankment failure.
It is also planned to secure the upper layer of the embankment with stone facing by installing a steel support mesh and self-drilling bar anchors with a diameter of Φ=38.0 mm, a minimum yield force of F0.2,k=350.0 kN, and a length of L=9.0 m, with spacing H x V=2.50 x 2.0 m.
In addition to these works, the reconstruction of the stormwater drainage system and road pavement structure at the site is also planned.
To verify the effectiveness of the proposed interventions, systematic monitoring during the construction phase and subsequently during operation is planned. Additionally, testing of all installed piles is foreseen to verify compliance with design specifications.
Installation of one inclinometer with a length of L=12.0 m is planned to monitor potential further displacements of the embankment. The inclinometer measurement schedule is as follows:
- One measurement every three months during the first year after implementation of the remediation measures (total of 4 measurements)
- One measurement every six months over the following two years (total of 4 measurements)
