28 December 2022
Subgrade Improvement of Pavement -Port Blair, Andaman
Ground Improvement works using Maccaferri’s MacGrid EG application.
Maccaferri’s Geogrid ground improvement solutions were placed within unbound granular layers to improve the performance of the road or track bed, extending its life, and increasing maintenance intervals.
NHIDCL had decided to take up the development, rehabilitation, and upgradation of National Highway-223 (New NH-4) in Andaman. The available soil was highly plastic with PI up to 42%. The poor quality of subgrade soil may lead to settlement forming progressive ruts and eventually failure of the pavement. The conventional solution of replacement top 0.5m subgrade was not feasible due to the high cost and unavailability of the good quality soil nearby. Good quality aggregates were not available and were required to be brought from mainland of India.
After considering the site condition, Maccaferri MacGrid® EG was proposed to improve the load bearing capacity and CBR property of the subgrade soil. Excavation of 0.5m subgrade was done and compacted into two layers of 0.22m each to 95% of MDD. On the finished compacted soil layer, MacTex® N (non-woven geotextile) was laid for separation and filtration purposes. MacGrid® EG layer was installed on the top of MacTex® N, followed by filling & compacting of 60 mm of crushed aggregate (Minimum CBR 80) to 95% of MDD.
MacTex® N will prevent the intrusion of clayey soil into the crushed aggregate and MacGrid® will reinforce/stabilize the subgrade. The solution has helped to improve the CBR from 2% to 8%, Elastic Modulus of the Subgrade and improve the Load Bearing Capacity of the pavement by the following mechanism:
(a) lateral restraint
(b) improved bearing capacity
(c) tension membrane effect