Support Fluids for Piling in Urban Areas: Preparation, Operation and Specification-PPT Presentation

PPT Presentation

Pdf Summary

The presentation discusses preparation, operation and specification of support fluids for piling in constrained urban sites, focusing on bentonite and soil-dispersion-inhibiting polymers (SDIPs), including HPAM/PHPA. When SDIPs are used with augers, buckets or grabs, a separation plant may not be required.<br /><br />Both bentonite and HPAM are affected by dissolved calcium and magnesium and by overall ionic strength. Electrical conductivity is a practical indicator of ionic strength; the cited Support Fluids Guide gives 1,500 µS/cm as a reference value. Treating mix water generally involves alkali hydroxides or sodium carbonate, but the appropriate method depends on water chemistry.<br /><br />For magnesium-rich water, sodium hydroxide is recommended, raising the pH to at least 10.5; sodium carbonate is ineffective and can increase conductivity excessively. For calcium, water with sufficient alkalinity can be treated with sodium hydroxide to pH 8.5–9, precipitating calcium carbonate. If magnesium also requires treatment, continue to pH 10.5. Low-alkalinity water may be treated with sodium carbonate to about pH 10, although conductivity rises rapidly at higher pH. Treatment quantities and pH targets should be planned from water analyses before mobilisation and checked periodically using a calibrated electrical pH meter.<br /><br />The presentation cautions against turning guidance into rigid specification. Guidance should provide useful typical values and support informed choices suited to each site. Specifications using “shall” impose mandatory limits, which must be reliable and meaningful; excessively broad limits offer little value. Project specifications, standards and codes take precedence, while guidance should remain adaptable to site conditions.

Keywords

piling

support fluids

bentonite

SDIPs

HPAM

PHPA

electrical conductivity

sodium hydroxide

sodium carbonate

urban sites