When designing a solidification treatment method for a caisson-type quay in Japan, it is necessary to conduct an seismic response analysis under the level 2 earthquake ground motion. On the other hand, the ground improved by deep mixing method exhibits significant spatial variance of its mechanical properties due to heterogeneity of naturally deposited ground and non-uniformity of cement-mixing. In the Japanese design standard for solidification treatment method, instead of considering this spatial variability, it is general to conduct the analysis on uniform ground with reduced average unconfined compression strength of in-situ improved ground. In this paper, we conducted series of analyses on the ground with variability, directly considering the spatial variability of the shear strength, in order to achieve a more low-cost design. Furthermore, we identify the improvement area that significantly affects the residual horizontal displacement of the caisson, and propose a low-cost and safe design method implementing partially high-quality improvement.

Owing to the non-uniformity of improvement and the spatial variability of soil properties, sandy ground treated by the solidification method to prevent liquefaction exhibits greater spatial variability in shear strength than naturally depositted ground. This study expressed the spatial variability of shear strength using random field theory and modeled the reduction of soil strength due to the ground liquefaction during an earthquake. In this study, we used the results of our investigations on sandy soils improved by penetration grouting method, but this method is also applicable to cemented soils. We conducted a bearing capacity analysis using Monte Carlo simulation based on the finite element method, FEM, and shear strength reduction method. Furthermore, the deformation behavior owing to the dissipation of excess pore water pressure after liquefaction was investigated stochastically and statistically. The findings were used to propose a novel performance-based evaluation method for bearing capacity and flatness that indicates performance index values to be met for runways after an earthquake.

Soilmixing techniques, among their many applications, serve to enhance soil load-bearing capacity, reduce settlements, and mitigate liquefaction effects. This research aims to establish numerical correlations between analytical formulations and axisymmetric and 2D numerical models to estimate soil improvement. Additionally, these calibrations will be presented in relation to three static load tests, where both numerical models and soil creep are evaluated. The findings will include the results of a soil improvement project at an existing hospital, employing the soilmixing technique for structural underpinning.

In the case of grid-wall soil improvement methods, which are used as liquefaction countermeasure methods, it is necessary to analyze the seismic response to determine the extent of residual displacement that occurs after an earthquake. However, as the modeling and analysis of grid-wall soil improvements with 3D geometry using a 3D model takes time, it can be to use a quasi-3D analysis method that combines two sets of two-dimensional cross-sections under boundary conditions. Furthermore, in some cases, to make the quasi-3D analysis results equivalent to the 3D analysis results in large-scale projects, the stiffness of the grid walls used in the quasi-3D analysis method was reduced from the value used in the 3D analysis. Although, in this case, it is possible to make a determination regarding the degree of reduction in the wall stiffness by checking the consistency against the experimental results, it would be difficult to make a determination in regard to the degree of reduction in the wall stiffness through a consistency check with experimental results in every project. Thus, we prepared a chart that can easily determine the degree of stiffness reduction of a grid wall for the quasi-3D analysis method considering the grid spacing, liquefaction layer thickness, and ground conditions. Based on this, it was demonstrated that quasi-3D analysis methods can be easily used in grid wall soil improvement design.

Deep Mixing (Hereinafter “DM”) was applied to soft clay layers in ore storage facilities in a new Copper Smelter in Gresik, East Java, Indonesia for settlement reduction and bearing capacity enforcement. In Indonesia, precast concrete pile is often applied as foundation structures. However, DM was chosen for several facilities because piles require a deeper supporting layer with SPT-N-value of about 50, while DM can be supported by a shallower intermediate layer with SPT-N value of 20-30. In design, it was assumed that facility loading is concentrated on DM columns. Specifications of DM were designed with a focus on the three points : (i) Design compressive strength exceeds a facility loading, (ii) Bearing capacity at the tips of the column is larger than the loading, and (iii) The sum of deformations of the column and the ground under the column is less than a target value. The improvement ratio and design strength were set according to the loading condition. The quality of the constructed columns was sufficient because the in-situ column strengths exceeded the design strength. The ratios of the in-situ column strength to laboratory strength ranged from 0.5 to 2.0. The average deformation modulus was 175 times of the in-situ column strength. Regarding construction work, by arranging machinery to dealing with underground obstacles such as boulders, installation works were able to proceed smoothly. The additional construction work was able to be carried out under appropriate cost with payment conditions determined previously.

To obtain basic data to promote the appropriate use of deep mixing method, survey on the recent application of deep mixing method was conducted using the data of soft ground countermeasure works for road construction in Japan over the last 10 years. The deep mixing method accounted for about half of all the countermeasures applied in projects where the depth of improvement or the thickness of the soft ground layer was 3 m or more. Column type improvement by wet mixing was the largest number of the cases among the deep mixing methods. Compared to the soft ground composed mainly of clayey and sandy soils, a trend toward higher binder amount was obtained for the improvement of the ground composed mainly of unusual soils.

The renewal project of the pump station in reclamation land of lagoon required proper foundation for the box culvert. The soft soil more than 40m deep results in harmful settlement and required ground mitigation by Deep Soil Mixing (DSM) columns combined with Mass Stabilization (MS) as a floated spread foundation. The flexible foundation contributes the sustainable system due to prevents serious leakage under the culvert during the operation if it is supported by the piling foundation. Sustainable aspects such as saving binder content and reducing waste soil strongly support the dry mixing technology and contribute to reduce carbon dioxide emissions. Productivity better than wet mixing brings considerable advantage to reduce carbon dioxide emissions. Prior to Mass stabilization work and DSM columns installation, careful and comprehensive laboratory mixing tests were conducted to ensure most suitable binder content. Consequently, the binder content less than half of preliminary estimation was conducted. The quality assurance and quality control demonstrated excellent performance of DSM columns.

Soil Cement mixes and parameters used for mechanical mixing and injection, and the evolution of these mix designs and mixing parameters, are typically developed using a combination of previous project test results, a series of early trials for a new application, a theoretical mix design including injection parameters, followed by commencement of mixing on site. An observational approach meaning iterations/cycles of theory and the early practical results, would then lead to continuous adjustment of the site installation parameters, to meet the project requirements. Deep mixing techniques such as Cutter Soil Mixing (CSM), and mixing by excavator base machine known by varying names including Mass Soil Mixing (MSM) or Insitu Mass Stabilisation (IMS), has been observed over a number of years to achieve very successful and efficient ground improvement. Designers acting for clients, typically start with quite stringent requirements and expectations that ground improvement by soil mixing should end up with certain material properties, as if insitu mixing were equally as controllable as the batching of concrete. The challenge for us as specialist contractor, is to convince client-side designers that insitu mixing is not done in factory conditions, and will be more variable compared to concrete manufactured in a batch plant. The target parameters and boundary limits then need to be set, and QA/QC verification carried out during construction to indicate the outcome. The idea of ground improvement is to provide an economical solution to a ground engineering problem, at a lower cost than conventional deep foundation structural installations such as piling, diaphragm walls, and the like. In turn the most economic solution is also likely to be the most environmentally sustainable one. The various concepts and measures of environmental issues, sustainability, emissions targets and the like, typically fall under the same umbrella of economics i.e. low cost is also likely to be most sustainable. Chasing environmental targets which are not the most economic, are unlikely to be sustainable. The most economic approach is based on merit, and for soil mixing the basic concepts such as minimizing binder content, minimize work done, etc. to solve the ground improvement problem. By observation of early performance, the site installation can be progressively adjusted to arrive at the most economical and there for most sustainable outcome.

In Yokohama Port, the project to reorganize the international container terminal has been conducted with the aim of maintaining and expanding the main route in Japan for container cargo. Among them, the construction of the revetment and the quay with a water depth of -18.0 m with the ground improvement by Cement Deep Mixing Method (CDM Method), has been carried out in Shin-Honmoku Area. In this area, there is a complicated soil profile that the soft clay has been deposited above 10m thickness, the gravel layer (Ag1) and the hard clay layer (Dc1) are intricately interposed. CDM method had been carried out under deep water condition exceeding -20.0 m, the Ag1 layer and Dc1 layer had been set as the bearing layer. Therefore, the effort for determination of bearing layer properly, had been conducted based on the preliminary soil investigation. In addition, the ICT Construction and BIM/CIM which stores the records of design, construction and maintenance with 3D data, have been adopted in this project. This paper describes our efforts have been reported on these issues.

Loose sandy soil layers are prone to liquefaction under strong earthquake motions, causing damages to civil engineering structures. Where liquefiable soil surfaces are sloped, liquefaction-induced lateral flow tends to increase the extent of damage. Previous studies have shown that such damage can be adequately prevented by deep mixing with cement. However, reinforcing the entire depth of liquefiable ground is costly for river levees. The cost and construction period can be reduced by improving only shallower parts immediately beneath river embankments. In order to rationalize the design approach, the present study aims to evaluate the effect of shallower mixing with cement on the deformation characteristics of river embankments located on liquefiable ground taking into account the effect of sloping ground. A series of shaking table model experiments were carried out with a centrifugal acceleration of 50g. The experimental results revealed that cement mixing for shallower parts can mitigate the settlement of embankments regardless of the occurrence of lateral flow. Furthermore, the embankment body located above the cement-treated soil block was found to withstand strong earthquake motions and retains its shape safely. This would contribute to rapid repair of river embankments immediately after a strong earthquake.

There are unprecedented challenges to the design of the Patimban Port Development Project, a huge port complex housing 4000m berth length and 320ha terminal area planned to be built 1km offshore of Subang coast, the Republic of Indonesia. Seating on extremely difficult ground, conventional soft soil treatment techniques are found not effective, nor environmentally friendly. A novel design approach that combines the Low Improvement ratio Cement Deep Mixing (CDM) method for the stabilization of the soft foundation and the Cement Pipe Mixing (CPM) method for the solidification and reuse of dredged material on reclamation is therefore proposed to reduce the project cost, and to minimize the adverse impacts to the environment. This paper describes the design method and selection process of the CDM and CPM, the very first project worldwide that combined two different soil solidification techniques in practice.

City of Helsinki has a goal of carbon neutrality by 2030, and this article explores methods to mitigate carbon emissions in ground improvement projects in the residential areas of Malminkenttä. The article focuses on the feasibility and low-carbon opportunities of using low-carbon binders in place of conventional lime-cement binders in deep mixing. Through laboratory and field tests, alternative binders are validated for their efficiency in reducing emissions. Carbon accountings confirm the potential for significant emission reductions in the residential areas which are characterized by deep clay layers. The study concludes that using low-carbon binders and low-carbon ground improvement methods, as well as implementing effective carbon management procedures, can successfully lead to emission reduction targets in ground improvement projects.

T-shaped bidirectional cement mixing column has unique advantages in improving mixing quality and foundation bearing capacity. However, field test research on the bearing characteristics of more than 15 m ultra-deep column with long enlarged head is insufficient. In this paper, vertical load tests were carried out to test the bearing capacity of single column and composite foundation with long enlarged head ultra-deep T-shaped bidirectional mixing column. Distribution characteristics of additional stress and axial force along depth were investigated. The results show that bearing capacity characteristic values of single pile and composite foundation are much higher than the designed. Axial force not only disperse to foundation soil through lateral friction resistance, but also transfers to the lower foundation soil beneath enlarged head at variable section. Therefore, the new column type work well in improving deep mucky silty soft soil foundation above karst bearing layer.