Reinforcement techniques work by strengthening the ground and reducing the amount of shear deformation they undergo during an earthquake.
The reduced deformation lowers the pore water pressures in the soil, making liquefaction less likely to occur. The increased strength of the reinforced ground also mitigates ground deformation and subsidence of supported structures if liquefaction was to occur.
Reinforcement involves constructing either:
- a lattice of intersecting walls to form containment cells or
- a grid of closely spaced stiff vertical columns.
Grid systems are relatively flexible and do not offer the same protection against liquefaction as a lattice with continuous perimeter walls. Lattice structures are therefore a much more reliable method of reinforcement than grids of isolated piles.
Soil reinforcement is typically used to treat soils up to a depth of 20 m, but greater depths are possible with specialised equipment.
Reinforcement techniques are suitable for a range of ground conditions, including silty and variable soils. Construction vibration is typically small and, with jet grouting, reinforcing can remediate the ground beneath existing structures or on sites with limited access.
Compared with densification and drainage techniques, reinforcement methods are typically more expensive.