Menard's Vibro Compaction Ground Improvement Solution for Vizhinjam Port
Menard was appointed as Ground Improvement contractor by HOWE to treat the reclamation soil for the Vizhinjam Port. The purpose of the treatment was to achieve the project specifications for the container terminal. The Vizhinjam Port, an International Transshipment Deepwater Multipurpose Seaport, is an ambitious project taken up by the Government of Kerala. It is designed primarily to cater to container transshipments and also multi-purpose and break-bulk cargo.
Regular compaction is commonly used to treat reclamation fill soils, but they come with challenges, particularly related to fines content and treatment depth. Traditional roller compaction is effective only for depths of 1-2 meters, making it unsuitable for deeper compaction needs, where piling becomes too costly. To address these issues, ground improvement solutions such as compaction, inclusions, and consolidation are utilized. Based on the study of the project, Menard recommended using the deep compaction technique to treat the soil.
Menard confirmed the reclamation fill by understanding parameters such as Grain Size Analysis & Shear parameters, and depth of fill. The parameters show that used soil is loose sandy soil with less than 10% of fines. After the confirmation of the fill parameters used, Menard proposed Vibro Compaction as a ground improvement technique.
Why Vibro Compaction?
Vibro Compaction is part of Deep Compaction techniques - the most effective ground improvement measure for densification of loose soils. Vibro Compaction was proposed to treat the fill up to a depth of almost 20m, thereby eliminating any other compaction options due to limitation of depth.
Vibro Compaction is used to control and reduce settlement, mitigate liquefaction, stabilize, or treat hydraulic fill. Loose soil or fill can be compacted at depth through insertion of vibrating probes together with a large volume of water to generate localized liquefaction of the soil. This enables the particles to rearrange themselves in a denser formation and thereby increase the overall density of the soil.
Vibro Compaction is executed using a rig (excavator, drilling rig or crane) and a vibrating probe. Under the effect of its own weight, the machine’s pull-down force (if any), the effect of the jetted water and the sustained horizontal vibrations, the vibrating probe rapidly reaches the desired depth. The probe is then gradually lifted in successive passes, and produces, in this way, a cylinder of compacted ground from 2 to 4.5 meters in diameter, depending on the type of soil and probes.
Evaluation of End Results
Menard employed a tandem set-up for Vibro Compaction at the site to tackle the challenge of a limited time frame. This tandem set-up doubled the production rate compared to the standard Vibro Compaction technique commonly used in India.
The total area of improvement was about 191,744 sq.m. This area was divided using the approaches that determined the necessary depth of improvement. The area was divided by considering equal size boxes of 5000 sq.m. Two pre-improvement CPTs were carried out in each box to evaluate the depth of treatment, and finalized accordingly.
A trial area was carried out to determine the production parameters, which would satisfy the project requirements. Based on the trials, grid spacings and hold time were decided and used for further boxes for treatment. The level of compaction achieved was satisfied with analytical calculation for Safe Bearing Capacity of more than 200kPa. Similar to the pre CPTs, two Post CPTs were carried out in each box. Safe Bearing Capacity was satisfied with these CPTs values, and all the boxes satisfied the project specifications.
