SoilNailing Challenges in 20M Depth
The effort vastly improved the company’s planning and execution functions, they knew that in order to succeed in this era of technology their geotechnical systems needed to be much more robust than what they are. They turned to Dishmaan to improve their geotechnical system solution.
A 20-storey residential high-rise planned for construction at Vejalpur, Ahmedabad included a three-storey below-grade parking garage with an excavation footprint of 107,000 square ft.
- The 40-ft-deep basement excavation, adjacent to the ocean, was 34ft below land level, posing the significant challenge of controlling groundwater inflow, especially with the native limestone.
- Ground conditions were particularly difficult and extensive geophysical surveys and ground investigation were needed to identify the different soil profiles and enable the design of the optimum ground improvement solution.
We provided the client with an on-time turnkey solution which consisted of a deep large area excavation with design build excavation support, groundwater control and deep foundations.
Dishmaan solved the groundwater control challenge by using deep soil mixing to create a seepage barrier along the perimeter and base of the excavation. The perimeter soil mix columns also provided excavation support as they were reinforced with steel H-piles and laterally restrained with tieback anchors or internal bracing.
Dishmaan designed and installed large-diameter auger cast piles as deep as 85ft below the excavation to support the structural loads and act as tiedown anchors for resisting the hydrostatic uplift on the soilcrete bottom slab.
Soil nailing is a very versatile excavation retaining system for deep excavations in urban areas surrounded by major structures and infrastructures provided that limiting lateral displacements are not exceeded.
Using conventional methods of design and previously developed charts for estimating lateral displacements or performance ratio may be misleading in deep soil nailing applications Monitoring and modern numerical analysis based design and application for such deep soil nailed walls are of primary importance.
By the numbers, the effort:
- The soil nailing was done in a complex ground conditions having both soil cover and weathered hard rock.
- Cost analysis performed by comparing the designed soil-nailed wall and conventional retaining wall for this site indicated that the soil-nailed wall was economical for the present case study.