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Geotechnical & Foundation Engineering

Foundation design, deep excavation support and soil-structure interaction for difficult ground, reclaimed land and constrained urban sites.

Ground is the only part of a project that nobody designed. Everything above it can be specified, tested and rejected; the soil is simply what is there, known only through a handful of boreholes and a set of laboratory tests on samples that were disturbed on the way up.

That uncertainty is the discipline. Good foundation engineering is not confident prediction — it is choosing a system whose behaviour degrades gracefully when the ground turns out to be worse than the report suggested.

Interpreting before designing

We start by reviewing the soil investigation rather than accepting it. Is the borehole spacing adequate for the plan area and the variability observed? Do the boreholes extend far enough below the proposed founding level to capture a soft layer that would govern settlement? Are the SPT values corrected? Was the water table recorded at the right time of year for a site that floods?

Where the answers are unsatisfactory we scope the additional investigation. It is always cheaper than the redesign.

Choosing a foundation system

Raft, piled raft, pile group, well or caisson — the choice depends on the settlement tolerance of the superstructure as much as on the ground. A rigid shear-wall building punishes differential settlement in a way that a flexible steel frame does not, so the foundation decision is inseparable from the frame decision. Our design accounts for soil-structure interaction explicitly rather than assuming a rigid support at each column base, which is a comfortable assumption that systematically underestimates settlement-induced forces in transfer structures.

Excavation is a structural problem

Deep basements in congested cities fail neighbours more often than they fail themselves. Our excavation support design covers the full sequence: each stage of dig and prop, the movement the adjacent structures will experience, trigger levels at which work stops, and the instrumentation that measures it. Where dewatering is required we assess the drawdown effect on neighbouring foundations before specifying it, not after somebody’s floor cracks.

Questions

What clients ask before appointing us

Our soil report says the bearing capacity is adequate. Is that enough?
Rarely. Bearing capacity is a strength check, and most foundation problems in Indian cities are serviceability problems — total and differential settlement, long-term consolidation in soft marine clay, and heave in expansive soils. A number that satisfies bearing capacity can still produce a building that cracks.
Can you design foundations next to an existing building?
Yes, and it is a large part of our urban work. The governing issue is usually the movement induced in the neighbour by our excavation rather than the capacity of our own foundation. We model the excavation sequence, set movement trigger levels, and specify the monitoring that verifies them during construction.
Do you review the soil investigation or just use it?
We review it, and we frequently ask for more. A borehole log that stops above the founding depth of the piles you intend to install is not a basis for design, and re-mobilising a rig later costs far less than a redesign.

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