In any project, constructing on weak sub-grade is always a challenge. In this case, StrataWeb's client, Allcargo Logistics, faced with a similar situation at their proposed container terminal in Kolkata. The container yard, located at Kidderpore Dock is being utlised 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 3 metres of heterogeneous fill.
Strata Geosystems is a leader in the geosynthetics market across the globe.
The company provides end-to-end solutions for soil reinforcement challenges including the supply, design, and construction with our world renowned StrataGrid™ (geogrid) and StrataWeb®(geocells). In addition to the ISO and CE mark, the testing for our products are conducted in GAI-LAP accredited labs across the U.S., U.K., and India. We are also a proud member of the International Geotechnical Society (IGS) promoting advancements in geosynthetics.
Container yards typically have two major issues:
- Heavy pressures from container stacks
- 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 which 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, a 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 required to be carefully determined by monitoring settlement trends during each loading stages. 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 above 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 sub-grade. The design included two layers of StrataWeb to bear the load spread. The StrataWeb was in-filled and topped with 10 mm of down-graded gravel. StrataBase was included to further strengthen the section and improve the performance.
Strata's value addition