Abstract: The inclined high-pressure jet grout cut-off wall with the soil nails as the excavation support structure was applied to the deep excavation in saturated sandy soils. The deformation at the top of the supporting structure and the selected prestressed soil nails are instrumented and monitored. The deep excavation monitoring data pit show that the maximum horizontal displacement and vertical settlement of the top of the inclined high-pressure jet grout cut-off wall with soil nails are only 0.84H‰ (H is the excavation depth), which is much smaller than the current code and specifications allowable values, and basically equivalent to the 0.57H‰ and 0.51H‰ of the soldier pile wall with the ground anchor supported structure. In the deep foundation in the saturated sand layers, the inclined cut-off wall with soil nail supporting structure can replace the soldier pile wall with ground anchored supported structure. The cost of the inclined cut-off wall with soil nail supporting structure is only 90% and 73% of the vertical cut-off wall with soil nail wall supporting structure and the soldier pile wall with ground anchored supporting structure, which demonstrates a very good cost-effective way for the excavation supporting structure. The specially designed inclined jet grouting drilling machine solves the bottleneck problem of the limitations of the previous construction equipment, and therefore provides a large growth space for the wider applications.

Key words: Inclined High-Pressure Jet Grout as Cut-off Wall, Composite Soil Nail Wall, Deep Excavation Support, Jet Grout, Prestressed Ground Anchor