This paper presents the direct tension test results providing the tensile properties of cement-treated clays. The direct tension test was conducted for the cement-treated clay specimens prepared with several cement contents in a laboratory. The local displacement transducers were used to measure the deformation of the specimen accurately. The unconfined compression test was also conducted for the specimens prepared in the same manner as the tension test specimens. The direct tension test results shown that the stress-strain relationship of the cement-treated clays is nearly liner under the tensile loading. The tensile strain is around 0.05% at the peak tensile stress. The tensile strength increases with the cement contents. The ratio of the tensile strength to the unconfined compressive strength is around 0.2. This ratio is the same as that for the cement-treated sands.

The deep excavation required for the planned construction of a residential building in Odessa, standing the site specific geotechnical and hydrogeological environment, presents delicate stability problems with potential critical effects on the existing confining structures. Soil cement retaining walls were selected as possible solutions to minimize the induced settlements and provide at the same time a hydraulic cut off to guarantee dry conditions for the following working phases. The geotechnical characterization of soils, show a complex subsoil profile due to the presence of loose collapsible water bearing silty sandy loess layer and of interbedded soft to firm silty clay layer, which lies down to about GL-20 m under the excavation plane. Standing the unfeasibility of adopting bracing methods due to the very large area and construction costs, the conceptual design of cantilever retaining structures followed the “displacement-based design” method, similarly to what is usually done in earthquake engineering. For this purpose, reinforced soil cement retaining walls system were proposed and the relative design analysis have been carried out with the aid of 3D finite element software. Unfortunately, the project after a brief start is currently on hold due to the ongoing conflict.

North of the city of Sundsvall, Sweden, GeoMind has designed a 600-meter-long rubble-mound structure founded on large diameter wet deep mixing columns. The work was initiated by an evaluation of competitive technical solutions with the aim of minimizing the technical and work environment risks, costs as well as time for construction. The soil comprised of silty, partly quick clay and sulphide clay. In addition to conventional soil investigations, the design included disturbed and undisturbed soil sampling to be able to optimize binder type and quantity with the aid from laboratory mixing and strength testing. The design resulted in a column pattern with mainly non-overlapping columns with the area coverage of roughly 90 % with a required average unconfined strength of 140 to 230 kPa in the columns. The governing failure modes were sliding and overall stability. The wet deep mixing columns were executed by Bauer Spezialtiefbau GmbH. Execution was carried out from a pontoon using large diameter, single shaft equipment. During execution, the stepwise wet grab and core sampling revealed a challenge to achieve sufficient homogeneity and strength in the silty sulphide clay pockets that were erratically encountered, mainly in the upper soil volume. Modification of the mixing tool, mixing process parameters as well as adding a double stroke sequence in the upper part to the mixing process resulted in significant improvement of the homogeneity as well as the undrained shear strength. Detailed testing of strength versus time was performed in the laboratory where seismic, unconfined and triaxial tests were performed. After sufficient curing, the rubble was constructed by subsequent filling from one side to the other.

The development of the Cutter Soil Mixing (CSM) method started in a joined development of BAUER Maschinen GmbH and Soletanche Bachy back in 2003. The system was presented for the first time at BAUMA Munich in 2004. Since its presentation in 2004, the equipment technology has developed considerably. Either driven due to project requirements, or to manufacturer's intention. The CSM equipment introduced 2004 enabled a mixing width of 500 mm and a depth of 13 m. In the meantime, mixing widths of up to 1524 mm and mixing depths of up to 80 m have been realized. With the CSM technique an expansion of the use of soil mixing became possible. Either in depth or in soil conditions, which were limited in their use. Therefore, the CSM methodology can be seen as a valuable contribution to the deep mixing industry. In the last 20 years, more than 100 CSM units have been distributed worldwide. This paper will give an insight into project-related and equipment-related milestones regarding CSM. As well, the paper will provide an overview of the beginnings of the CSM method, the current technical status, and an outlook on future developments.

Land expansion projects, by essence, involve the permanent occupation of marine spaces. Expansion of port terminals and reclamation projects often require preliminary ground improvement as the existing seabed properties are not always sufficient to provide enough stability and/or bearing capacity to support a significant increase of loading. Amongst the potential ground improvement technologies applicable, non-dredging techniques such as offshore deep cement mixing become of growing interest as they prevent the displacement of huge volumes of marine sediments, reduce the impact on water quality as well as marine species and are usually faster to complete.This article first presents the use of a rope suspended low headroom deep cement mixing equipment involving diaphragm wall cutter technology and working from floating barge vessel on anchors with air draft as low as six meters from sea surface. Then, after introducing the technical and environmental challenges linked to the offshore context, innovative marine applications are then presented through various case histories: load transfer platform for reclamation project, shear walls, offshore liquefaction mitigation for construction of a new wharf and a retaining wall for the deepening of an existing quay.