Microstructural Analyses of a Stabilized Sand by a Deep-Mixing Method

Bellato, Diego; Marzano, Ignazio Paolo; Simonini, Paolo

doi:10.1061/(asce)gt.1943-5606.0002254

Cited by 7 publications

(5 citation statements)

References 35 publications

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“…The NGF-technique on average yielded samples with 40-60% higher strength than the SVV-technique and tended to represent the field strength more successfully (see Figure 2a). The results (Figure 2b) support the hypothesis of an inverse linear relationship between strength and porosity, as observed by Bellato et al (2020) for strength improved sand.…”

Section: Test Results and Discussionsupporting

confidence: 81%

“…Microstructural investigations can reveal the inner interactions between the soil and added binders and explain these differences (Jian et al 2016). Non-invasive laboratory methods have recently been applied to describe the role of porosity on the mechanical behaviour of treated soils (Bellato et al, 2020). For example, by using X-ray micro computed-tomography (μCT) it is possible to investigate the microstructure of materials and estimate the resolved porosity within a soil sample (Viggiani & Hall, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Comparing laboratory and field samples of lime–cement-improved Norwegian clay

Paniagua

Falle

Hov

et al. 2022

Géotechnique Letters

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Improving the structural integrity of clay-rich soil is crucial to mitigate risks related to ground movements, and representative procedures are needed to quantitatively describe the reproducibility and authenticity of laboratory-mixed clay model specimens. Here, two standardised industry protocols for preparation of laboratory lime-cement improved clay samples are compared to field lime-cement improved clay. Samples from both dry deep mixed (DDM) clay columns and laboratory mixed clay, with different binder quantities, were tested for density, water content, unconfined compressive strength, and analysed by X-ray micro-computed tomography. Results showed clear differences in sample density and ‘macro-porosity’ described as entrapped air resulting from field installation and laboratory preparation (i.e., moulding technique). For the field samples, the macro-porosity was relatively low (< 2 %), indicating that the air used in the binder injection is successfully evacuated along the drilling rod as sought after during in-situ DDM works. For the laboratory samples, prepared with two standard moulding preparation protocols, the macro-porosity was larger and having an influence on the measured strength and stiffness of the improved soil. An inverse relation between the mechanical strength under unconfined compression and porosity was found. In conclusion, the industry-standard laboratory moulding techniques fail to reproduce specimens that are representative for field conditions.

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Section: Test Results and Discussionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Comparing laboratory and field samples of lime–cement-improved Norwegian clay

Paniagua

Falle

Hov

et al. 2022

Géotechnique Letters

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“…This visibility is even higher at high cement content (250 kg/m 3 ), which is due to the very high clinker content in the manufacture of CEM I 52.5. We also observe in all the pictures that the CSH (paste) is denser for soil concrete formulated with CEM III 32.5 (Figures 15c, 16c, 17c and 18c), which show a good bonding of the paste-aggregate interface [34]. This explains the fewer pores and consequently fewer cracks in the specimens formulated with CEM III 32.5 compared to those formulated with CEM I 52.5 and CEM II 42.5.…”

Section: Modulus Static Elasticitymentioning

confidence: 54%

Influence of the Nature of Cement on the Physical and Mechanical Properties of Soil Concretes from Sandy Clay and Laterite

Kamdem,

Elat,

Eslami

et al. 2024

CivilEng

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Soil concrete is a material produced by mixing the soil at the site with a hydraulic binder. This paper aims to study the influence of the nature of binder on the physical and mechanical properties of soil concrete. For the mixtures, three types of soil were chosen and studied: sandy clay with a granular class of 0/5 (SA5), laterite with a granular class of 0/5 (LA5), and laterite with a granular class of 0/10 (LA10). Three different cements were used: CEM I 52.5, CEM II 42.5, and CEM III 32.5, with cement contents of 150 and 250 kg/m3. The soil concretes were designed for a constant spread of 32–33 cm measured on a mini-slump. The results showed that LA5-based soil concrete has a higher water content of about 8.8% more than SA5 and LA10-based soil concretes. For all the mixtures, the lowest porosity values were obtained with CEM III 32.5, followed by CEM I 52.5, and finally CEM II 42.5. For the three types of cement and the same soil granular size, the compressive strength, static, and dynamic modulus of SA5-based soil concretes are higher than LA5. It was noted that the mechanical properties of soil concretes made with CEM III 32.5 are higher than those made with CEM I 52.5 and CEM II 42.5. Regardless of the type of cement used, the mechanical properties obtained on LA10-based soil concrete are higher than those on LA5-based soil concrete.

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“…The CSM method combines the undisturbed soil mixing method with the double-wheel milling groove method and can be adapted to a variety of environments. It offers many advantages, such as seepage prevention, soil retaining, foundation engineering, and geological improvement [7][8][9][10][11][12]. The CSM approach for excavating multi-span foundation pits offers several benefits, including high construction efficiency, suitability for complex site conditions, precise verticality control, effective anti-seepage measures, low soil replacement rates, and environmentally friendly practices [13][14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Study on the Effect of Multi-span Pit Excavation on Supporting Structures Based on the Cutter Soil Mixing Method

Wu,

Shan,

Liu

et al. 2023

Sustainability

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The Cutter Soil Mixing (CSM) method, a relatively recent innovation, employs twin-wheel milling and profound agitating machinery for wall construction. In an endeavor to scrutinize the displacements and internal support stresses to the support structure during the excavation of a multi-span foundation pit founded upon the CSM method, a two-dimensional finite element model was established, utilizing the Midas GTS NX 2019 V1.2 finite element software. This model was grounded on a multi-span foundation pit excavation endeavor situated in the eastern expanse of China, where steel bracing and the CSM method assumed the preeminent mantle of support. A comprehensive scrutiny encompassed ten distinct working conditions, each juxtaposed and dissected to ascertain the displacements affecting the CSM wall and the forces exerted upon the support system during the foundation excavation process. The research findings manifest a certain interplay between the embedment depth of the CSM wall and the span of the pit excavation in shaping the displacement and support stresses within the supporting structure. While deeper embedment augments the potential for enhanced support outcomes, its efficacy remains constrained. As the embedment depth increases, the internal support moment and lateral displacement of the wall increase slightly. Taking a pit with a shallow embedded CSM wall as an example, wherein both the lateral and vertical displacements experience an ascent followed by a descent, culminating at the juncture of a four-span pit. Likewise, the axial force and bending moment exerted upon the steel supports undergo a similar trajectory, culminating with a two-span pit as the threshold. At the five-span, the maximum lateral displacement of the CSM wall exceeds that observed at the two-span by an increment of 21.14%. These findings offer invaluable insights into the embedment depth of diaphragm walls and the span of pit excavations, wielding profound implications for future undertakings akin to the foundation pits in question.

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Microstructural Analyses of a Stabilized Sand by a Deep-Mixing Method

Cited by 7 publications

References 35 publications

Comparing laboratory and field samples of lime–cement-improved Norwegian clay

Comparing laboratory and field samples of lime–cement-improved Norwegian clay

Influence of the Nature of Cement on the Physical and Mechanical Properties of Soil Concretes from Sandy Clay and Laterite

Study on the Effect of Multi-span Pit Excavation on Supporting Structures Based on the Cutter Soil Mixing Method

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