B202 – Road repairs, Grevenhorst-Sandschleuse GERMANY – 2001
Roads (01-009-A)
01-009-A – pag 2/4
Problem Heavy cracking and unevenness in the road surface due to settlement in the embankment caused by traffic load; Section to be repaired without interrupting traffic.
Cubic Area: 10,500 m3. Load: ADT = 5,000 vehicles/day; ADTT = 500 vehicles/day.
Cracks in the road surface before repair.
Composition Road bed Building class II in line with German RStO guidelines; 4 cm asphalt concrete 0/11; 4 cm asphalt binder 0/16; 14 cm asphalt base course; 20 cm upper anti-frost layer; 18 cm lower anti-frost layer. Base 20 cm bituminous recycled asphalt (containing tar) on a covered expanded clay fill; 8-20 mm expanded clay, thickness: 1.2 m; wrapped in GRK 4 geotextile for protection; Mineral flank-waterproofing through clay cover; GRK 4 geotextile as separating membrane against the subsoil.
Building method 1. Lay sheeting in the middle of the road; 2. Removal of half of the existing embankment to AOD-0.3 m; 3. Positioning of the geotextile on the road bed; 4. Application of the Leca® in layers of approx. 0.6 m; 5. Compaction of the Leca® with a vibroplate (pressure q < 5 kN/m2), more than three passes; 6. Wrap over the geotextile + apply the next geotextile layer; 7. Continued construction of the embankment body, simultaneously constructing the flank waterproofing from clay; 8. Construction of the road bed on one side; 9. Dismantle the sheeting + excavate the second half of the embankment without sheeting (horizontal forces absorbed by the wrapped-over geotextile); 10. Construct the second half of the embankment + road bed as before; 11. Completion of the asphalt surface.
Subsoil Clay and slightly decomposed peat to a depth of 13 metres; Beneath: fine-to-medium sand and marl.
Construction
5 cm topsoil
5 cm topsoil 20 cm recycled material from previous asphalt
Clay
Clay
building phases
Mineral flank waterproofing (Clay) Separating membrane
Expanded clay 8/20 mm Threshold between
Supporting textile
Supporting textile
4 cm asphalt concrete 0/11 S mm in line with ZTV Asphalt-StB 94/98 4 cm asphalt binder 0/16 mm in line with ZTV Asphalt-StB 94/98 14 cm asphalt base course, C sand mix, in line with ZTVT-StB 95/98 20 cm upper anti-frost layer, in line with ZTVT-StB 95/98 18 cm lower anti-frost layer, in line with ZTVT-StB 95/98 20 cm base course made of bituminous milled asphalt rubble 0/32 with bitumen emulsion (or: application of removed asphalt surface in grain size 0/32 mm) 120 cm lightweight aggregate (Leca®, grain size 8/20)
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01-009-A – pag 3/4
Quality control Dynamic plate-bearing tests On Leca®: Evd = 15.4 … 34.3 MN/m2 On anti-frost layer: Evd = 37.5 … 70.3 MN/m2 Static plate-bearing tests On Leca® plate ø300 mm: Ev2 = 28.2 … 30.5 MN/m2 (reduced load levels): Ev2/Ev1 = 2.23 … 2.68 On anti-frost layer plate ø300 mm: Ev2 = 54.8 … 130.0 MN/m2 Ev2/Ev1 = 2.01 … 3.76 Establishing the mass unit weight / degree of compaction Leca®: ρd = 0.25 … 0.32 g/cm3 Anti-frost layer: degree of compaction = 99.7 … 101.7%
Performance Measurements Inclinometer measurement (vertical and horizontal) 2 years after completion.
Slight bulge + destressing of the subsoil at Station 21+706 (Clay).
Depth (m) Curve
Gauge
Measurement series
Date
Notes
Settlement of up to 6.1 cm in the middle of the road at station 21+850 (Peat)
Depth (m) Curve Gauge
Measurement series
Date
Notes
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01-009-A – pag 4/4
Settlement of up to 5.1 cm in the middle of the road at Station 21+950 (Peat)
Depth (m) Curve Gauge
Measurement series
Date
Notes
Flaws/damage Type: none. Time: -Visual appraisal as of 12.05.2004 Deformations: lengthways/crossways: impeccable condition; Transitional/contact areas: impeccable; Road surface: no visible flaws.
View of the transition area to the expanded clay fill; left: road surface – no detectable flaws.
Maintenance work Normal.
Appraisal/Experiences Application of Leca® possible using standard earth-moving equipment; Vertical height differences no problem using a combination of Leca® and geotextile as protection; Destressing under the Leca® layer; Settlement results from low groundwater levels during the last hot summer –› loss of water from the peat and ‘spring effect’ in peat (rapid rising and falling).
www.maxit-group.com maxitGroup AB, Box 415, SE-191 24 Sollentuna, Sweden Tel.: +46 (0)8 858 70 64 00, E-mail: info@maxit-group.com
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