Construction of Container Storage Yard with StrataWeb® at Kolkata Port
|Location||Kidderpore Docks, Kolkata, India|
|Consultant||Shanghvi and Associates Consultants Pvt. Ltd.|
|Application||Paved area to support five-container high stacks|
|System Offered||Paved section incorporating StrataWeb®|
In any project, constructing on weak subgrade is always a challenge. In this case, our client was confronted with a similar problem at their proposed container terminal in Kolkata (a major city in India). The container yard, located at Kidderpore Dock is used for transit storage of heavy containers which would be stacked five-high. The subsoil in this area includes 7-8 metres of riverine deposits comprising of soft clay topped by about 3m of heterogeneous fill.
Container yards typically have two major issues, which have an impact on construction and maintenance: A) Heavy pressures from container stacks. B) Non-uniform settlements of the ground.
The Conventional Approach
By the conventional method, the subsoil is consolidated by installing prefabricated vertical drains (PVDs) and preloaded by placing surcharge. This is a slow process that requires close monitoring of settlements as the surcharge is placed in stages. Surcharging usually involves large quantity of earthwork to progressively achieve the final load, often equivalent to the load to be transferred from the loading system.
However, container stack loads are quite heavy, requiring heavy surcharge. Besides, time to retain each surcharging stage to develop adequate bearing capacity for the next stage needs to be carefully determined by monitoring settlement trends during each loading stage. The cost of earthworks to achieve the final loading and its redundancy after surcharging can be overwhelming.
Strata's Innovative Approach
Strata geotechnical specialists designed an innovative solution that is cost-effective, technically-sound, and long-lasting. The Strata solution eliminates the concrete layer altogether. The system incorporates StrataWeb® within the paving to reduce the bearing pressures onto the subsoil. This provides a leaner pavement design. StrataWeb® along with infilling also addresses the differential settlement issues, providing an even working ground.
The analysis demonstrated that imposed pressures with a section reinforced with StrataWeb® SW 356-150 (Weld spacing 356 mm; cell depth 150mm) are well within the safe bearing capacity of the subgrade. The design included two layers of StrataWeb® to bear the load spread. The StrataWeb® was infilled and topped with 10mm of down-graded gravel. StrataBase was included to further strengthen the section and improve the performance.
Strata's Value Addition
- Saved up to 15% of the cost compared to conventional methods
- Increased life span with lower maintenance
- Uniform settlements and even working ground
- Rapid installation due to ease of StrataWeb® transportation and use of locally available and cheaper material
- Load spread ensured that bearing pressures were within safe limits