Alternative Solutions to Replace Diaphragm Walls of Shallow Depths-Paper

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The paper examines soil mixing as a practical alternative to diaphragm walls for shallow excavations, where diaphragm wall construction may be uneconomical or constrained by limited site space. It focuses on two wet-mixing techniques: Cutter Soil Mixing (CSM) and Soil Mix Wall (SMW). Both blend cement-based slurry with in-situ soil to form overlapping wall panels; steel beams can be inserted where structural retaining capacity is required.<br /><br />Compared with diaphragm walls, soil mixing can offer higher productivity, smaller equipment footprints, simpler waterproof joints, reduced spoil volumes, fewer personnel, and no need for just-in-time deliveries of pre-mixed concrete. Using local soil also reduces disposal requirements, which can be particularly valuable where soil is contaminated. Performance depends on ground conditions, wall layout and depth; dense, hard or highly variable soils can slow production or affect final strength.<br /><br />CSM uses horizontally rotating cutter wheels for intensive mixing and can handle a wider range of soils, including limited penetration into weak rock. It can reach depths of up to 53 m with a Kelly-guided system, or up to 80 m with a rope-suspended system. SMW combines three mixing rods to form elongated panels and is commonly used at depths up to about 23 m.<br /><br />Two projects illustrate the methods. In Perth, Australia, CSM was used for a 550 mm-thick basement retaining wall, achieving about 14 m of wall per mixing hour. In Laudenbach, Germany, SMW replaced a planned diaphragm wall for a 13 m-deep undercrossing and achieved about 15 m per hour, with limited spoil.<br /><br />The authors conclude that CSM and SMW merit consideration when speed, restricted site space, or reduced spoil and disposal costs are priorities.

Keywords

soil mixing

diaphragm walls

Cutter Soil Mixing

Soil Mix Wall

wet-mixing techniques

shallow excavations

cement-based slurry

retaining walls

limited site space

contaminated soil