●Read water levels and pressures by depth

A water-table elevation describes the free water surface in an unconfined aquifer. A piezometer measures hydraulic head for its screened or isolated interval. A confined layer can have head above the top of the layer. Perched water can lie above the regional water table. Record the instrument, response interval, datum, date and time with each reading. Drilling water and slow equilibration can distort a borehole reading. Use repeat observations where rainfall, seasons, tides or pumping may change conditions.

Read the boring logs, soil samples and SPT records alongside the water observations. CPT records cone resistance and sleeve friction. CPTu adds pore pressure at a stated filter position. Pressure measured while the probe advances reflects the penetration response as well as the ground condition. Use the filter location and saturation record, and review any dissipation hold. Use groundwater instruments and the site investigation to establish design groundwater conditions.

●Effective stress during and after driving

In saturated soil, effective normal stress equals total normal stress minus pore-water pressure. At the same total stress, a rise in pore pressure lowers effective stress. A reduction in pore pressure from drawdown can increase effective stress under comparable total stress and cause compressible layers to settle. Displacement driving can generate positive excess pore pressure in saturated clay. Soil disturbance and displacement can also contribute to remolding and heave.

The pressure response depends on the soil, drainage and the pile. Resistance can increase after driving as pressures dissipate and the soil recovers. Engineers call this increase setup. In some dense silts and fine sands, resistance can decrease with time, a response called relaxation. Use the project’s testing schedule and acceptance criteria when reviewing resistance after driving.

●Vibratory driving, impact driving and ground response

Vibration can reduce resistance at the pile-soil interface in suitable conditions. A fast penetration rate alone does not establish liquefaction. Loose saturated sands and some low-plasticity silts can lose strength if cyclic loading builds enough excess pore pressure. Assess susceptibility and cyclic demand using the site investigation. Check the potential for ground movement near foundations, utilities and slopes. Impact driving can also generate excess pore pressure.

Compare candidate vibratory or impact equipment using the pile section, target depth, soil profile, permitted method and site limits. For impact work, review predicted blow counts and pile stresses against the approved driving criteria. Check the hammer and pile interface, crane capacity at working radius, and the hydraulic supply and hose route where applicable.

●Plan pumping, casing and installation aids

Start with the source of inflow and the pressure in each relevant layer. Where excavation or predrilling calls for water control, have the responsible engineer assess the working platform, bore support, seepage and uplift. Check whether temporary casing or an engineered water-control system is required. Review potential settlement outside the work area before pumping and follow applicable discharge requirements.

If pumping changes groundwater levels around the piles, have the engineer check pile resistance during pumping and after groundwater recovers. Treat jetting and predrilling as installation aids. Either can change shaft or toe resistance. Use them only where the project permits them and the engineer has checked their effect on the pile and its acceptance criteria.

●Measure the response and apply acceptance criteria

Before production, agree on monitoring locations, baseline readings, trigger levels and who can stop work. The site team may use piezometers, settlement points or vibration monitors according to the risks. Record inflow, heave, movement, pile condition, driving settings and penetration or blow counts as required. If a trigger is reached, follow the agreed pause and review procedure.

Confirm the specified depth, installation records and acceptance checks. Use restrike, dynamic measurements or static load tests where the project calls for them. A blow count or penetration rate alone cannot establish capacity. The responsible engineer decides whether the work meets the project criteria.