Innovative Design for Retaining Structures Using Combined Products-Paper

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The paper presents innovative combinations of geotechnical products for deep urban excavations where space, groundwater, adjacent structures, geology, or property rights make conventional retaining systems impractical or costly.<br /><br />One approach combines jet-grouted walls with vertical prestressed anchors. The anchors increase vertical stress within the wall, improving its bending resistance and reducing the need for wall thickness or multiple horizontal anchor rows. Properly designed anchor-head bearing blocks are essential to prevent local failure. Buttress walls offer another alternative: strategically spaced jet-grout columns and retained soil provide stability while reducing treated material compared with fully contiguous walls.<br /><br />A Prague project demonstrates a layered retaining system adapted to restricted access and variable ground conditions. Jet-grouted columns underpinned neighbouring buildings and formed a groundwater barrier; soil nails and shotcrete retained the underlying silts, while micropiles transferred vertical loads past the nailed section. Detailed finite-element modelling accounted for construction stages and local variations.<br /><br />For watertight excavation support, the paper describes filling gaps between contiguous bored piles with jet-grout columns or thinner lamellas. These elements transfer soil and water pressures to the structural piles, offering flexibility in pile spacing and potential cost savings, but performance depends on strength, interface shear, and accurate installation.<br /><br />A Perth project combined cutter soil mixing (CSM), steel beams, propping, and post-grouted ground anchors to support excavation beneath a heritage building. CSM provided a watertight wall with less vibration and smaller equipment than conventional alternatives. Higher-capacity anchors reduced the required anchor count by 33%, and the work caused no structural damage to the heritage building.<br /><br />The paper concludes that successful urban excavation design depends on matching techniques to site-specific constraints. Combining products and involving specialist geotechnical contractors can provide safer, more efficient, and more economical solutions when standard methods are unsuitable.

Keywords

geotechnical products

deep urban excavations

jet-grouted walls

prestressed anchors

buttress walls

soil nails

micropiles

contiguous bored piles

cutter soil mixing

post-grouted ground anchors