Results Of Oedometer Tests Research Articles

Compressibility of lime-treated dredged slurry with high water content

Lime is widely used for soft ground treatment, rendering the compressibility of lime-treated soil a crucial factor in deformation analysis in engineering applications. This study investigated the compressibility of three remoulded lime-treated slurries with high water content in Southeast China. Sixty groups of oedometer tests were conducted on lime-treated soils with an initial water content of 1 to 3 times the liquid limit and lime contents between 1 and 3%. The oedometer test results were discussed to examine the remoulded yield stress σy′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upsigma }_{y}^{\\prime}$$\\end{document} of lime-treated slurry. Considering the relationships between σy′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upsigma }_{y}^{\\prime}$$\\end{document}, the void ratio, lime content, and initial water content were preliminarily discussed and quantitatively established. Research on the normalised compression curve of lime-treated soil revealed that for soil samples containing a lime content of 0–%, the normalised compression curve at σp′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upsigma }_{p}^{\\prime}$$\\end{document}>σy′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upsigma }_{y}^{\\prime}$$\\end{document} can be represented by a unique line. Furthermore, the log(1 + e) − log σv′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\sigma }_{\ ext{v}}^{\\prime}$$\\end{document} compression curve of lime-treated slurry at pre-yield state is analysed, and a prediction method for the modified compression index is proposed.

Comparison between methods for determining the effective vertical yield stress of intermediate fine-grained soils.

Effective vertical yield stress (σ'xy) is essential in accurately describing fine-grained soils' mechanical properties and their behaviour under load over time. It helps assess settlements and stress history. In most constitutive models, this parameter indicates changes in the soil behaviour due to the development of recoverable and irrecoverable strains resulting from loading. The results of oedometric compression tests for 25 soil samples with a wide range of plasticity parameters were used for the investigation. The intermediate fine-grained soils comprised different proportions of clayey, silty and sandy fractions. An in-depth, two-staged statistical analysis was carried out to compare twelve methods of determining effective vertical yield stress, namely: Casagrande (CM), Pacheco Silva (PSM), Butterfield (BTM), Oikawa (OIM), Onitsuka (ONM), Boone (BM), Becker (WM), Morin (WPUVSM) Wang & Frost (DSEM), Tavenas (SEM), Senol (SLSEM), and Janbu (JM). It aimed to check the association of these methods and the consistency of the obtained results. Based on the difference analysis, the methods originated in the work approach (i.e. WM, WPUVSM, DSEM) and CM gave comparable σ'xy values. The methods utilised bi-logarithmic plots (i.e. BTM, OIM, ONM) received slightly greater or lesser σ'xy values than BM and JM. The remaining methods were characterised by medium to the high variability and were sensitive to even the slightest disturbances resulting from the procedure of determining σ'xy.

The sensitivity of Prazeres clay – some results on reconstituted samples

Soil’s structure is defined as the issue responsible for the differences observed in the mechanical response of natural soil samples compared to the intrinsic behaviour of reconstituted samples. The parameter that incorporates the differences in microstructure of intact and reconstituted clays is designated by stress sensitivity. The influence of microstructure and fabric on the behaviour of soils has been evaluated by comparing strength and compressibility characteristics of intact and reconstituted samples of the same material. Included on a broad characterization study of Lisbon Miocene Prazeres clay held at Porto University, some oedometer and triaxial tests were undertaken on intact and reconstituted samples. In this paper, the process of preparing reconstituted samples and consolidating them in a large oedometer to the in-situ stress is thoroughly described. The results of oedometer and triaxial tests on reconstituted samples are presented and compared with results for intact samples from the same site. A proposal for parameterisation of the intrinsic characteristics of this clay is established on the basis of test results. Concerning compressibility, oedometer test results show good adjustment to the isotropic compression line (ICL). Triaxial test results for intact samples in the light of critical states soil mechanics are similar to those obtained in s’-t space for the reconstituted samples. The intrinsic parameters show good agreement with those described in the literature for soils of the same nature.

A study of the multi-scale compression behaviour of a sand immersed in a viscous liquid

Pore fluids with different viscosities can exist in soils. While the effects of pore fluids have been investigated at the macro-scale, little is known about how they might affect the micromechanics. A novel apparatus allowing a single particle to be crushed while immersed in a liquid was built here. With the help of a high-speed microscope camera, the crushing processes of single silica sand particles immersed in glycerine were captured and the breakage modes were clarified. The immersion in glycerine leads to stronger particles with higher strains at failure compared with immersion in water or exposure to air. Moreover, the results of constant rate strain oedometer tests revealed that saturation in glycerine made the sample significantly stiffer in compression as a result of less particle breakage compared with that in water or under dry conditions. The lower particle breakage at the macro-scale appeared to correspond to the higher strengths measured at the micro-scale.

Effect of the Organic Matter Content on the Mechanical Properties of Soils Stabilized with Xanthan Gum

The aim of this paper is to study the effect of the organic matter (OM) content on the effectiveness of the soil stabilization process using the biopolymer xanthan gum. Five different artificial soils with an organic matter content in the range of 1.5 to 7.7% are subjected to unconfined compressive strength (UCS) and oedometer tests to evaluate their strength, stiffness and compressibility, respectively. These results are complemented by an analysis of SEM images. The results from the UCS tests show a positive effect of the stabilization process in terms of strength and stiffness in a range of an OM content of 1.5 to 5.5%, but a detrimental effect for a higher OM content (7.7%) is observed. Due to the hydration of the biopolymer’s hydrogels, the compressibility tends to increase in specimens stabilized with xanthan gum. This effect is amplified for higher OM contents. The results of oedometer tests also show that the stabilization with xanthan gum brings about a significant decrease in the coefficient of consolidation, inducing an increase in the primary consolidation time.

On the use of biocementation to treat collapsible soils

The effectiveness of biocementation to treat the collapse potential of a well graded sand is investigated. The novelty on the application of this treatment for this purpose is that the analysis is done considering structural changes experienced by the soil during the treatment and not only in service. Oedometer tests were performed on treated and untreated soil samples, both in saturated and unsaturated states, to study structural changes due to loading. The presence of biocement bond was confirmed by indirect tensile tests, and other complementary tests were performed to detect the presence of biocement and evaluate the efficiency of the treatment to reduce the collapse potential. Saturated permeability measurements, collapse tests and pore size distribution from mercury intrusion porosimetry tests confirmed the collapsible nature of the soil and that the treatment by bio-cementation reduces collapse potential. However, the treatment was effective not because of the presence of the biocement providing bonds to a metastable soil structure, but mainly because it requires the full saturation of the soil, therefore causing early collapse. Therefore, further collapse on rewetting of the treated soil is basically the second collapse, and for this reason the amplitude of the deformation observed reduces and the treatment is effective. Nevertheless, the physical bonds provided by the biocement precipitated were evident on the results of oedometer and indirect tensile tests, providing additional strength to the soil particles, and therefore some maintaining structure after the treatment. Therefore, the biocementation treatment to reduce the collapse potential is the junction of the treatments pre-wetting the soil, and those providing the reinforcement of the soil with binder, in this case with biological nature.

The Effect of Fines Content on Compressional Behavior When Using Sand–Kaolinite Mixtures as Embankment Materials

In South Korea, Honam High-Speed Railway has a relatively large residual settlement issue and high fines content has been pointed out as one of the causes. Design guidelines regulate not to use soils containing fines content higher than 25%. However, there is no background information on the effect of fines content on settlement. Therefore, this paper aims to investigate compressional behavior according to fines content using sand and kaolinite. Oedometer test results showed that the compression index is lowest with fines content of 15% to 20% at which the mixture produced maximum density. The optimum fines content for inducing low settlement would be 15% to 20% for the sand–kaolinite mixture. Transition fines content (TFC), which shows sand-like to claylike behavior, was observed to have between 21% and 26% of fines content. Critical fines content (fcrit) where a minimum void ratio occurs was estimated as 21.67%. These behavioral changes appear when fines content is greater than the optimum fines content. SEM also shows that the kaolinite particles were overlapped, creating flat surfaces with a fines content higher than 30%, and showing clay-like behavior. Based on the analysis results, engineers can simply identify the behavior of embankment materials to ensure optimum fines content and consequently minimize long-term settlement potential.

Comparative Study on Particle Size Effect of Crushable Granular Soils through DEM Simulations

Abstract The particle size plays an important role in the mechanical behavior of granular geomaterials. With respect to the crushable granular soils, the particle breakage under different pressures leads to the variation of the particle size distribution of soils. Therefore, it is essential to accurately model the particle fracture process to reproduce the key response of granular soils in the simulation. In this study, two simulated approaches, cluster method and replacement method, were performed to investigate the particle size effect for the crushable granular soils by three-dimensional (3D) discrete element method (DEM). DEM simulations were validated through the available results of diametric and oedometric compression tests with the help of the Weibull statistics. Based on the evaluation at particle and assemble-scale, it is found that both the cluster method and replacement method could simulate the particle strength and size dependence of sample failure with a good agreement with experimental results. The particle breakage phenomenon is also successfully modeled in DEM simulation and analyzed by the breakage index. Meanwhile, the computational efficiency was analyzed compared with two simulated methods. The findings in this study can provide a viable approach to investigate the particle breakage effect of the crushable geomaterials.

СПОСОБ ПРЕДСТАВЛЕНИЯ РЕЗУЛЬТАТОВ КОМПРЕССИОННЫХ ИСПЫТАНИЙ ПРИ ИЗЫСКАНИЯХ ТОРФЯНОЙ ЗАЛЕЖИ

The use of the average values of physical and deformation characteristics for the entire extremely heterogeneous peat layer leads to mistakes in estimation a settlement of the embankments set up over it. The results of numerous oedometer tests of peat and empirical equations for calculating the void ratio of peat as a function of its initial value and the load are presented. A new approach to carrying out the geotechnical surveys in a wetland is proposed.

Strength and stiffness parameters for hardening soil model of rockfill materials

In recent years, an increasing number of rockfill dams have been constructed in many developing countries around the world. One difficulty in the engineering design and construction of rockfill dams is the characterisation of the rockfill materials. Thanks to advancements in computational geomechanics, a finite element analysis is usually employed in geotechnical engineering design. To perform such analyses, a proper constitutive model with relevant parameters that reflect the stress–strain-strength characteristics of rockfill materials are required. This study presents a procedure to determine the strength and stiffness parameters of rockfill materials that can be used with the Hardening Soil (HS) model to characterise the behaviour of rockfill materials. Based on triaxial and oedometer test results, a set of HS model parameters can be determined. To implement and validate the procedure, six rockfill materials from the Nam Ngum 2 Dam construction project in Laos PDR are employed in this study. The influences of stress level and particle breakage on the stress–strain/volumetric-strain behaviours of rockfill materials are discussed. Finally, the procedure to determine the material parameters for rockfill materials presented in this study can also be applied to other rockfill materials.

A Study of Innovative Alkali-Activated Binders for Soil Stabilisation in the Context of Engineering Sustainability and Circular Economy

In the context of sustainability in the civil engineering industry, chemical ground improvement is becoming increasingly used, as a generally more sustainable alternative to replacing and landfilling unsuitable for construction ground. However, traditional soil stabilisers such as Portland cement or lime are not environmentally impact-free; international research effort is thus focusing on the development of innovative cementing agents. This paper presents results from a feasibility study on the development of suitable alkali-activated slag cements for the stabilisation of two soils. A number of alkali-activators were considered, comprising potassium hydroxide, a range of alkali salts, as well as a material retrieved from waste (Paper Sludge Ash, PSA) which contains free lime. Indicative results of an extensive parametric study in terms of unconfined compressive strength (UCS) are shown, followed by results of ongoing oedometer tests to determine soil compressibility and some preliminary tests on selected soil/binder mixes to observe the durability to wetting-drying cycles. Overall, all alkali-activated cement mixes increased the UCS and stiffness of the soil. Carbonates and Na2SiO3 used on their own gave lower strength increases. The highest strengths were achieved from AAC with KOH and Ca(OH)2 from PSA, which showed similar strength gain. The latter material has shown consistently a lot of promise in terms of strength, stiffness and volumetric stability of the soil as well as treatment durability. Ongoing research focuses on further mix optimisation and a comprehensive mechanical and durability property testing supported by material analysis (mineralogical, chemical and microstructural) to gain a better understanding of the complex mechanisms involved.

Validation of a 3D numerical model for piled raft systems founded in soft soils undergoing regional subsidence

Abstract In this paper a 3D numerical model using a software based on the Finite Element Method (FEM), was developed and validated using the results obtained in a geotechnical centrifuge model of a piled raft system founded in soft soils undergoing regional subsidence. The piled raft configuration had nine piles distributed in the center of the raft. The kaolin parameters were obtained, calibrated, and validated for the Hardening Soil Model (HSM), based on laboratory triaxial and oedometer test results. Also, a single pile load test was carried out in the centrifuge to get the resistance parameters used in the FEM. The developed numerical model reproduced satisfactorily soil and foundation consolidation displacements due, not only by the structural service load but also by the pore pressure drawdown. For load distribution on piles and raft, the model reproduces with good agreement the foundation behavior only for the structural service load, for pore pressure drawdown some adjustments on the embedded piles elements shaft and base resistance had to be done. The developed model allowed to identify the most sensitive parameters for this type of simulation, to define the types and stages of analysis that had the best fit for the physical model, and to obtain additional results to those measured in the physical model, e.g., the axial load distribution developed along the piles and therefore the magnitude of the negative skin friction, that is an important load that should be considered for the structural safety review of piled foundations subjected to this complex conditions.

Design of a three-dimensional earth pressure device and its application in a tailings dam construction simulation experiment

The basic principle of the three-dimensional stress state test is deduced based on the relationship between the normal stress and the conventional stress state, and the relationship between the total stress state and the effective stress state is given based on Terzaghi’s effective stress principle. On this basis, we made a three-dimensional earth pressure device by using a pedestal obtained by 3D printing technology, 6 micro earth pressure cells, a pore pressure cell and an attitude sensor. Considering the effect on the tested values of the dynamic change in the normal stress direction, the conversion relationship between the absolute test direction and the relative test direction of the test device is deduced, which can be used to dynamically test the three-dimensional total stress state and three-dimensional effective stress state. In addition, a method to calculate the K0 value is proposed based on the earth pressure device comparing with the direct test result by the K0 oedometer and indirect test results by direct shear test and triaxial test in laboratory. Two three-dimensional earth pressure devices are used in a simulation experiment of tailings dam construction, and the results show that with the increase in pore pressure, the calculated errors of the three-dimensional stress state caused by rotation angles will be more noticeable. This study has engineering value for in situ geotechnical testing and soil strength prediction.

Strength, Hydraulic, and Microstructural Characteristics of Expansive Soils Incorporating Marble Dust and Rice Husk Ash

Expansive/swell‐shrink soils exhibit high plasticity and low strength, which lead to settlement and instability of lightly loaded structures. These problematic soils contain various swelling clay minerals that are unsuitable for engineering requirements. In an attempt to counter the treacherous damage of such soils in modern geotechnical engineering, efforts are underway to utilize environmentally friendly and sustainable waste materials as stabilizers. This study evaluates the strength and consolidation characteristics of expansive soils treated with marble dust (MD) and rice husk ash (RHA) through a multitude of laboratory tests, including consistency limits, compaction, uniaxial compression strength (UCS), and consolidation tests. By using X‐ray diffraction (XRD) and scanning electron microscopy (SEM) analyses, the effect of curing on UCS after 3, 7, 14, 28, 56, and 112 days was studied from the standpoint of microstructural changes. Also, the long‐term strength development of treated soils was analyzed in terms of the interactive response of impacting factors with the assistance of a series of ANN‐based sensitivity analyses. It is found from the results that the addition of MD and RHA lowered down the water holding capacity, thereby causing a reduction in soil plasticity (by 21% for MD and 14.5% for RHA) and optimum water content (by 2% for MD and increased by 6% for RHA) along with an increase in the UCS (for 8% MD from 97 kPa to 471 kPa and for 10% RHA from 211 kPa to 665 kPa, after 3 days and 112 days of curing, respectively). Moreover, from the oedometer test results, mv initially increased up to 6% dosage and then dropped with further increase in the preconsolidation pressure. Furthermore, the compression index dropped with an increase in the preconsolidation pressure and addition of MD/RHA, while the coefficient of permeability (k) of RHA stabilized soil was higher than that of MD‐treated samples for almost all dosage levels. The formation of the fibrous cementitious compounds (C‐S‐H; C‐A‐H) increased at optimum additive dosage after 7 days and at higher curing periods. Hence, the use of 10% RHA and 12% MD as replacement of the expansive soil is recommended for higher efficacy. This research would be helpful in reducing the impacts created by the disposal of both expansive soil and industrial and agricultural waste materials.

Influence of loading geometry and palm fibres’ orientation on modification of collapsible sand

A review of existing literature suggests that extensive numerical and experimental works have been conducted on modifying soils using randomly distributed fibres. However, the influence of different types of loading geometry and the effect of fibres on modification of sandy soil have not been reported yet. The main objective of the present study was to evaluate the influence of palm fibres’ orientation on the modification of collapsible sand using different types of loading, including constrained, axisymmetric, and plane strain simulation. A laboratory testing program, consisting of 95 tests, was performed using oedometer, direct shear, and triaxial tests. It was observed that the orientation of fibres in the specimens was approximately perpendicular to the direction of the applied compaction effort. The results of oedometer tests for measuring of the collapsibility potential revealed that addition of the fibre content had no significant effect in reducing the collapsibility potential. For the two mould sizes used in the direct shear tests, an increase in fibre content did not cause any changes in the shear strength parameters. In triaxial tests, the results indicated a significant enhancement in strength with increase in the fibre content. The rotation of the principal stress orientation during the shear stage of the tests played an important role in mobilising the tensile strength of the fibres. The results suggested that the effect of fibre orientation and loading geometry is strongly consistent for evaluating the modification of fibre-reinforced sand.

Characterization and constitutive modeling of red clay contaminated with ammonium carbonate

AbstractConventionally, red clay is used for agricultural purposes in southern China. Fertilizers, especially urea, are commonly introduced into the red clay to improve the crop yields. However, due to the rapid urbanization in China, large areas of lands with red clays have been converted into sites for domestic and industrial constructions. Nevertheless, few researchers focused on the effect of urea on the strength and compressibility of red clay. In this research, the shear strength and compressibility of the red clay saturated by different concentrations of the (NH4)2CO3 solution (urea's hydrolysates) were experimentally investigated using direct shear as well as oedometer tests, respectively. It was noticed that both the shear strength and stiffness of the red clay significantly decreased after exposure to the urea solution. In addition, the micromechanisms of the strength and compressibility of the red clay treated by the (NH4)2CO3 were studied by the scanning electron microscope test and X‐ray diffraction test. Based on the test results, a new model was developed to simulate the chemomechanical behavior of saturated clayey soil by modifying the Barcelona basic model (BBM) for unsaturated soils. The proposed model introduces four additional parameters, compared to the BBM, to account for the nonlinear shear strength behavior of the red clay. This model accounts for most of the complex features related to the strength and stiffness behavior of clayey soils. The parameter calibration procedures, by using the oedometer and direct shear test results, are also presented. To validate the proposed model, experimental results from the literature are considered in which illite clay samples were either mechanically or chemically or both mechanically and chemically loaded. Part of the experimental results is used to calibrate the model parameters and the other part along with the calibrated parameters is used to verify the proposed model. A comparison between experimental data and predicted results demonstrated that the proposed model is able to capture the main features related to the chemomechanical coupling behavior of saturated soils.

A FEM analysis of the settlement of a tall building situated on loess subsoil

Abstract In order to correctly model the behaviour of a building under load, it is necessary to take into account the displacement of the subsoil under the foundations. The subsoil is a material with typically non-linear behaviour. This paper presents an example of the modelling of a tall, 14-storey, building located in Lublin. The building was constructed on loess subsoil, with the use of a base slab. The subsoil lying directly beneath the foundations was described using the Modified Cam-Clay model, while the linear elastic perfectly plastic model with the Coulomb-Mohr failure criterion was used for the deeper subsoil. The parameters of the subsoil model were derived on the basis of the results of CPT soundings and laboratory oedometer tests. In numerical FEM analyses, the floors of the building were added in subsequent calculation steps, simulating the actual process of building construction. The results of the calculations involved the displacements taken in the subsequent calculation steps, which were compared with the displacements of 14 geodetic benchmarks placed in the slab.

Investigating the elastoplasticity of an Australian soft rock based on laboratory test results

For the stability and deformation analysis of open-cut mines using numerical methods, one critical step is to identify and simulate the elastoplasticity of geomaterials comprising the open-cut batters. The Victorian Brown Coal (VBC) in Australia is a non-textbook geotechnical material with a hardening feature in compression leading to brittle failure while showing a sharp post-peak softening behaviour. In order to study different aspects of elastoplasticity including the hardening and post-peak softening behaviour of the VBC, a series of laboratory tests including one-dimensional oedometer and triaxial tests were carried out on undisturbed VBC specimens taken from 30 m to 50 m below the ground level in one of the largest VBC open-cut mines in Victoria. By post-processing of the triaxial and oedometer test results, a yielding phenomenon was identified at the boundary between the fully elastic and elastoplastic domains. The magnitude of the material stiffness in the elastic domain was found to be independent of the confining pressure in triaxial tests while governed by the chemical bonding of the coal particles. The post-yield behaviour, however, was a frictional hardening and ruled by the magnitude of the confining pressure leading to a failure envelope sensitive to the organic content of the material. In this paper, a unified failure envelope is defined for the VBC using the Hvorslev-type normalisation process. Furthermore, a nonlinear elastoplastic constitutive model was examined to describe the elastoplasticity of VBC in triaxial condition, which led to a good agreement between the experimental and numerical modelling results.

Confined and unconfined behavior of a silty sand improved by the enzymatic biocementation method

The aim of this work is to study the effectiveness of the enzyme-mediated calcium carbonate (CaCO3) precipitation methodology when applied to the confined and unconfined behavior of a silty sand. Based on the analysis of the results of UCS and oedometer tests carried out with non-stabilized and biocemented specimens, the effects of the curing time and the concentration of the biogrout solution (urease, urea, calcium chloride and water) on the improvement of the mechanical characteristics of the treated soils are studied. The results of UCS tests (stiffness and strength) are examined and compared with the results of oedometer tests (compressibility indices and vertical yield stress). The experiments are supplemented with the evaluation of the content of the CaCO3 precipitated, pH value and SEM/EDX tests. The unconfined compressive strength and the yield strength of the biocemented soil increase with the content of CaCO3 precipitated, which is potentiated during a curing time of less than 14 days and for a greater concentration of the biogrout solution. The precipitation of CaCO3 is validated by the results of SEM/EDX tests.

Sustainable Improvement of Zeolitic Pyroclastic Soils for the Preservation of Historical Sites

Climate changes are inducing a modification of environmental loads on historical sites, requiring new actions towards their conservation. In the paper, the results of an experimental work on sustainable improvement of a pyroclastic soil belonging to the Orvieto cliff (Central Italy) have been investigated in the perspective of its preservation from degradation. The slightly coherent facies of Orvieto Ignimbrite (pozzolana) was treated with hydrated lime and the subsequent chemo-physical evolution was investigated by means of a multi-scale analysis. The beneficial effects obtained from the improvement in terms of mechanical behaviour were interpreted and correlated to the chemo-physical evolution of the system. Microstructural analyses, X-ray diffractometry, thermo-gravimetric analyses (DTG), SEM observations, mercury intrusion porosimetry performed on raw and treated samples, showed that the pozzolanic reactions develop since the very beginning in the system and that the observed mechanical improvement of the treated soil is mainly due to the formation of calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH). In the paper, the mechanical improvement is put in evidence by comparing the results of oedometer tests performed on both raw and treated samples.