Fig. 1, 2. Photos of the problem area before work (June 2014)
The design institute of OJSC Soyuzdorproekt provides for the use of a reinforced soil geoplatform in a problem area with weak soils (clayey fluid-plastic gray silt in the form of a lens of variable depth of 5–10 m, E = 0.45 MPa). As part of the geoplatform, 5 layers of Geospan ORP 30/20 volumetric geogrid were used in an envelope made of high-strength woven geotextile Geospan TN-80.
Fig. 3. Calculation model of the embankment with recommended reinforcement at the location of the silt lens, made in the PLAXIS program
Fig. 4. Construction of a reinforcing geoplatform (June 2014)
The calculation analysis of the problem area (PK 24+00, PK 25+50) and the technical and economic efficiency of the reinforced soil geoplatform was carried out by Soyuzdorproekt OJSC with the participation of GEXA engineers in the PLAXIS geotechnical calculation program (modeling of the reinforced soil structures of embankments on weak foundations using the finite element method). The results of the calculation of the reinforced soil embankment showed:
decrease in settlement values compared to the settlement of the embankment without reinforcement by 56 cm (54%) and decrease in uneven deformation;
increase in the coefficient of stability of slopes from Cst=1.18 to Cst=1.72 at the required value of Ktr.=1.3. The stability of the reinforced soil embankment with the use of a geoplatform with Geospan materials is ensured with a margin of 35%;
reduction of consolidation terms by 44%.
During the construction of the geoplatform of JSC "SU-920" DSK "Avtoban" in June 2014, no violations of the technological regulations for laying geosynthetic materials were detected. The quality control of Geospan geosynthetic materials delivered to the facility was carried out jointly with the specialists of LLC Gexa - non-woven materials.
As of April 2015, there were no deformations of the subgrade and pavement in the problem area; in June 2015, Soyuzdorproekt OJSC plans to conduct monitoring with the issuance of a conclusion based on the results of the survey.
Fig 5. Photo of the site after completion of works (April 2015)