Consolidation Tests Research Articles

Vacuum consolidation of dredged slurry improved by horizontal drainage-enhanced geotextile

The vacuum consolidation behavior of dredged slurry improved by horizontal drainage-enhanced geotextile (HDeG) application was investigated. For comparison, vacuum consolidation tests using a prefabricated vertical drain (PVD) and layered prefabricated horizontal drains (PHDs) were conducted. Based on the test results, it was found that by using HDeG, the consolidation rate of the dredged slurry was significantly increased. Thus, the effectiveness of the HDeG method was verified. The nonwoven geotextile sheet of HDeG could provide a sufficient vacuum pressure and drainage and therefore greatly shorten the drainage path. The HDeG-induced consolidation settlement generally matched the calculated 1D consolidation settlement well using a representative coefficient of consolidation. The analysis of scanning electron microscopy images shows that after the vacuum consolidation test, the porosity of the PHD filter (vacuum PHD treatment) was only 11% (21.1% of the initial porosity), while the porosity of the PHD filter of the HDeG was 22.16% (42.6% of the initial porosity), suggesting that the geotextile effectively reduced the apparent clogging of the drains.

An elastoplastic model with egg-shaped yield surface for coastal soft clay

A novel elastoplastic constitutive model with an egg-shaped yield surface (ESE model) is proposed herein to elucidate the strength-deformation characteristics of marine soft clay. One of the key improvements offered by this model is its ability to address the singularity associated with plastic strain increments at yield surface corners—a limitation commonly encountered in traditional elastoplastic models. Additionally, the proposed model demonstrates flexibility, as it can transform into various forms under different conditions. Subsequently, to evaluate the efficacy of this egg-shaped elastoplastic model, numerical simulations are performed within the finite element software ABAQUS using an implicit integration algorithm through the user material subroutine interface (UMAT). The simulations encompass standard triaxial consolidation tests involving saturated soft clay sourced from the Itsukaichi marine clay as well as two types of saturated kaolin clays. The outcomes derived from these simulations by the ESE model are compared with both empirical data and numerical simulations originating from the widely employed Modified Cam-Clay (MCC) model. The simulations of the ESE model for three conventional triaxial tests on clay demonstrate superior concordance with experimental measurements in comparison to the MCC model. This underscores the efficacy of the proposed ESE model in predicting the strength and deformation characteristics manifested by coastal soft clays under undrained conditions. Finally, the predictions for deformation in an adjacent tunnel according to the ESE model closely align with experimental measurements and prior to the simulations conducted using the MCC model and advanced models such as the bounding surface model and the unified model, thereby affirming its practical utility in engineering applications.

Investigation of the Structural Strength of Expansive Soil in a Seasonally Frozen Region

The existence of structural strength in undisturbed soil results in its distinct characteristics compared to remolded soil. Under the influence of freeze–thaw cycles, this difference may easily cause geotechnical disasters in cold regions. This study aimed to analyze and discuss the expression degree and influencing factors of the structural strength of expansive soil. The unconfined compressive strength (UCS) test, high-pressure consolidation test, and microscopic test were performed on expansive soil retrieved from a seasonally frozen region. Moreover, sensitivity parameters, including stress sensitivity (St.qu, St.σk) and strain sensitivity (St.ɛu, St.Cc), were applied to explore the expression degree and influencing factors of structural strength in a seasonally frozen region. The results reveal that the undisturbed samples have better structural connection and particle arrangement than the remolded samples. However, the primary fractures have a certain degrading effect on the strength of the undisturbed soil as influenced by a seasonally frozen region. With the increase in water content and the decrease in density, the expression degree of the structural strength in terms of compressive strength and the ability to resist deformation enhances under the unconfined condition. By contrast, the expression degree increases in strength and decreases in ability under the confined condition. Furthermore, the effect mechanisms of the basic property, particle composition, structural linkage, lateral confinement, and historical role on the structural expression were analyzed.

Diatom-induced impact on shear strength characteristics of fine-grained soils

Diatomaceous soils, composed of diatom microfossils with biological origins, have geotechnical properties that are fundamentally different from those of conventional non-diatomaceous fine-grained soils. Despite their high fines content, diatomaceous soils typically exhibit remarkably high shear resistance, approaching that of sandy soils. However, the exact role that diatoms play in controlling the mechanical properties of fine-grained soils and the underlying mechanisms remain unclear. In light of this, the shear strength response of diatomaceous soils was systematically investigated using consolidated undrained triaxial compression tests on diatom–kaolin mixtures (DKMs) with various diatom contents and overconsolidation ratios. The micro- and nano-scale structures of the soil samples were characterized in detail using scanning electron microscope (SEM) and atomic force microscope (AFM) to interpret the abnormal shear strength parameters of diatomaceous soils. The results indicated that the presence of diatoms could contribute to significantly higher strength, e.g. the friction angle of DKMs was improved by 72.7% to 37° and the value of undrained shear strength tripled with diatom content increasing from 20% to 100%. Such significant improvement in soil strength with diatom inclusion could be attribute to the hard siliceous skeleton of diatoms and the interlocking between particles with rough surfaces, which were quantitatively analyzed by the surface roughness parameters with AFM. Furthermore, a conceptual model established based on the macro-mechanical tests and microscopic observations portrays a microstructural evolution of soils with increasing diatoms. The microstructure of soils was gradually transformed from the matrix-type to the skeletal one, resulting in a continual augmentation in shear strength through mutual interactions between diatom microfossils. This paper provides new insights into the multi-scale structural properties of diatoms and significantly advances our understanding of the mechanical behavior of diatomaceous soils.

Experimental Study on Compressibility and Microstructure of Loess Solidified by Permeable Polymer

This study aims to investigate the compressive and microstructural properties of loess before and after treatment with a new permeable polymer. To enhance the compressive properties of loess, specimens were infused with the new polymer, and one-dimensional consolidation tests were performed to assess the compressibility of solidified loess (SL) and unsolidified loess (UL) at different water contents. Additionally, the microstructure and pore morphology of UL and SL were examined using a scanning electron microscope (SEM) and the Particles (Pores) and Cracks Analysis System (PCAS). Statistical methods were employed to analyze the relationships between microstructural parameters and compression modulus. The experimental results demonstrate a significant improvement in the compressibility of loess when treated with the polymer. The complexity of pore structure and variability in pore size are reduced, leading to a more uniform pore distribution. Moreover, all microstructural parameters exhibit a strong correlation with the compression modulus. The results pertaining to the compressive and microstructural properties of loess reinforced with permeable polymer grouting can provide insights into the variations in the curing effect, serving as a theoretical foundation for the application of permeable polymer in loess treatment.

A laboratory investigation and numerical modeling on fiber reinforced lime and alkaline binder stabilized pavement subgrade soil

The differential settlement and excessive deflection in expansive subgrade soils lead to low volumetric stability upon moisture imbalance and cause severe damage to highway and airport field pavement surfaces. The present paper attempts to strengthen the stability behavior of expansive subgrade soil using an envirosafe alkaline binder (AB) with polypropylene fiber (PLF). AB was produced by combining dry aluminosilicate precursors (steel slag [SS] and sugarcane bagasse ash [SBA]) with a liquid activator (mixture of sodium hydroxide [NaOH] and sodium silicate [Na2SiO3]) in 0.4 water to binder (w/b) ratio. California bearing ratio (CBR) based resilient modulus, shear strength ratio (Sr), and consolidation tests were conducted as performance indicators of expansive subgrade soil reinforced with discrete PLF (0–0.5%) in 6% lime and 6% alkaline binder. The study also proposes the optimal sugarcane bagasse ash-steel slag-PLF dosage in the AB-stabilized subgrade layer. Moreover, mineralogical and morphological studies using powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were also carried out to understand the crystalline compounds and micro surface texture of the soil-fiber mixture. It was revealed that AB-fiber-soil exhibits higher interfacial frictional bonding and interlocking density than lime-fiber-soil. Also, 2D finite element analyses were carried out to compare the behavior of subgrade under the influence of vehicular load on the surface. PLF-AB soil mixture shows 72% lower vertical deformation than unstabilized expansive soil. Based on the findings of this study, recommendations for the practical application of stabilizing expansive subgrade soils were proposed.

Mechanism and Application of Soilbags Filled with Excavated Soil in Soft Soil Subgrade Treatment

This research addresses the characteristics of soft soil subgrades treated by soilbags filled with excavated clayey soil. We evaluated of the strength and deformation modulus of soilbags containing excavated soil using unconfined compression tests. In addition, the drainage consolidation characteristics of soilbag-treated subgrades were investigated via model consolidation tests. Furthermore, a practical application included the construction of a 100 m-long rural road subgrade with these soilbags. The field test and numerical simulation results included the surface settlement and pore water pressure during and after construction to validate the effectiveness of the soilbag treatment for soft soil subgrade. The results show that the soilbags significantly enhanced both the strength and deformation modulus of the soft soil, which met the design requirements after the soilbag treatment. The drainage attributes of the soilbag treatment were also found to support the consolidation process of the soft soil subgrade effectively. Notably, the pore water pressure diminished rapidly during the construction interval, which is beneficial to reducing the post-construction settlement. The settlement uniformity of the subgrade is good verification of the superiority of the soilbag-treated subgrades.

Digital tools used on the teaching-learning process in geotechnical engineering

This article presents the incorporation of information and communication technologies on the teaching-learning process of geotechnical engineering to improve the quality of education and provide practical knowledge to civil engineering students. The content of this paper is divided into three main modules, which are: Treatment of laboratory tests results, Slope stability and Rock mass stability. For this, some software were used, including 2D limit equilibrium stability analysis, stability analysis of rock wedges and a dynamic mathematics, to obtain and analyze soil shear strength parameters, among others. Furthermore, a digital tool was developed to analyze the results gathered in compaction, one-dimensional consolidation, and direct soil shear tests, in order to clarify the relationship between theoretical concepts and practical results of the tests and analyses and to help students on doubts, in addition to increase their interest and motivation to perform the complete interpretation of the collected data. The activities were conducted in classes of geotechnical disciplines of the undergraduate course in Civil Engineering at the Federal University of Viçosa, aiming to promote active learning and improve teaching quality. Based on the results of an applied feedback questionnaire, it was observed that most students were satisfied with the resources used in the classroom, demonstrating that the implemented digital tools work as a didactic instrument that facilitates learning and comprehension of practical problems, in addition to enabling the resolution of several geotechnical engineering problems much more quickly and efficiently.

A novel unresolved/semi‐resolved CFD‐DEM coupling method with dynamic unstructured mesh

AbstractThe greatest challenge when performing large deformation simulations using the CFD‐DEM coupling method lies in the dynamical update of the fluid meshes. To address this problem, a novel CFD‐DEM coupling method integrated with the dynamic unstructured grid is proposed in this work. The mesh initialization and reconstruction are performed by the Constrained Delaunay triangulation (CDT) implemented by the tetgen algorithm. Moreover, the equation of state (EOS) is introduced to consider the impact of fluid compressibility. The reliability of this coupling method is preliminarily verified by the particle sedimentation test. Additionally, undrained triaxial shear and one‐dimensional consolidation tests are conducted to examine the applicability of the proposed method in simulating geotechnical cases. From our analysis, it is found that the shear responses in the undrained triaxial shear test obtained from the proposed method with dynamic mesh are in direct accordance with those led by the constant volume (CV) method. However, difficulties arise in accurately describing the moving boundary by the fixed mesh, leading to unreliable results. Moreover, in the one‐dimensional consolidation test, both the dynamic and fixed grids can capture the Mandel—Cryer effect, which is more pronounced under the dynamic grid, mainly due to the dual impact of the loading device and particle skeleton on the fluid. A greater compressibility specified under the dynamic grid led to a weakening of this effect, whereas its duration is increased. Our work provides valuable insights for effectively dealing with dynamic fluid boundaries.

Deep Learning Approach on Prediction of Soil Consolidation Characteristics

Artificial neural network models, crucial for accurate predictions, should be meticulously designed for specific problems using deep learning-based algorithms. In this study, we compare four distinct deep learning-based artificial neural network architectures to evaluate their performance in predicting soil consolidation characteristics. The consolidation features of fine-grained soil have a significant impact on the stability of structures, particularly in terms of long-term stability. Precise prediction of soil consolidation under planned structures is vital for effective foundation design. The compression index (Cc) is an important parameter used in predicting consolidation settlement in soils. Therefore, this study examines the use of deep learning techniques, which are types of artificial neural network algorithms with deep layers, in predicting compression index (Cc) in geotechnical engineering. Four neural network models with different architectures and hyperparameters were modeled and evaluated using performance metrics such as mean absolute percentage error (MAPE), mean squared error (MSE), root mean squared error (RMSE), and coefficient of determination (R2). The dataset contains 916 samples with variables such as natural water content (w), liquid limit (LL), plasticity index (PI), and compression index (Cc). This approach allows the results of soil consolidation tests to be seen more quickly at less cost, although predictively. The findings demonstrate that deep learning models are an effective tool in predicting consolidation of fine-grained soil and offering significant opportunities for applications in geotechnical engineering. This study contributes to a more accurate prediction of soil consolidation, which is critical for the long-term stability of structural designs.

Evaluation of Deformation and Settlement Properties of Cement-Stabilized Silt Mixed with EPS Beads of Various Sizes

The expansion of China’s highways and railways, as well as the growing demand for them, has focused attention on the impact of traffic loads on foundation settling, uneven deformation, and ground cracking. These effects have garnered considerable research attention, with particular emphasis placed on integrating innovative materials into the soil matrix. This investigation involved loading experiments utilizing a combination of lightweight soil, expanded polystyrene (EPS), and cement. Consolidation tests assessed the extent of deformation and settlement, incorporating varying proportions of EPS and cement. The test results show that when subjected to confined conditions, the stress–strain relationship curve assumes a hyperbolic shape closely linked to the e-p curve. This shape effectively captures the unique structural characteristics exhibited by lightweight soils. As the size of the EPS particles and the applied stress increase, a corresponding rise in the strain of the specimens is observed. Simultaneously, as the strain magnitude increases, the elastic modulus experiences a decline. Additionally, it is noted that this trend further increases as the doping of the cement with EPS particles increases. When the EPS volume ratio and cement mix ratio remain constant across different specimens, there is a decrease in structural strength as the size of the EPS increases. In lightweight soil, settlement can occur rapidly, with approximately 95% of total consolidation deformation happening within a few minutes, which suggests that the settlement is instantaneous and primarily consolidation settlement. The structural strength of lightweight soil shows a negative correlation with the size of EPS, implying that larger EPS size may lead to a reduction in strength. Therefore, it is recommended to consistently use EPS beads with a diameter of 3–4 mm during construction.

A Study on Developing a Model for Predicting the Compression Index of the South Coast Clay of Korea Using Statistical Analysis and Machine Learning Techniques

As large cities are continually being developed around coastal areas, structural damage due to the consolidation settlement of soft ground is becoming more of a problem. Estimating consolidation settlement requires calculating an accurate compressive index through consolidation tests. However, these tests are time-consuming, and there is a risk of the test results becoming compromised while preparing and testing the specimens. Therefore, predicting the compression index based on the results of relatively simple physical property tests enables more reliable and accurate predictions of consolidation settlement by calculating the compression index at multiple points. In this context, this study collected geotechnical data from the soft ground of Korea’s south coast. The collected data were used to construct a dataset for developing a compression index prediction model, and significant influencing factors were identified through Pearson correlation analysis. Simple and multiple linear regression analysis was performed using these factors to derive regression equations, and compression index prediction models were developed by applying machine learning algorithms. The results of deriving the significance of the influencing factors from the developed compression index prediction model showed that natural water content was the most significant factor in predicting the compression index. By collecting a significant amount of high-quality data and using the compression index prediction model and the model construction process proposed in this study, more accurate predictions of the compressive index will be possible in the future.

Macroscopic Mechanical Properties and Microstructure Characteristics of Solid Waste Base Capillary Retarded Field Covering Material

In the practical operation of traditional landfills, compaction clay often experiences cracking, while the HDPE geomembrane may tear and bulge, resulting in a compromised performance of the landfill covering system. To address this issue, a capillary retarding covering material for landfill sites is proposed by utilizing municipal sludge and construction waste particles as substrates and incorporating a small quantity of calcium bentonite. The mechanical characteristics of the covering material were investigated using a standard consolidation test and a triaxial compression test. A permeability test and a soil water characteristic curve (SWCC) test were conducted to examine the permeability and capillary retarding effect of the covering material. Microscopic tests including SEM scanning, laser particle size analysis, and T2 NMR analysis were performed to investigate the connection mode, particle size composition, and pore structure characteristics of the covered particles. Based on the aforementioned research, the following conclusions can be drawn: The cohesion of the covering material ranged from 50 to 150 kPa, while the internal friction angle ranged from 24.23° to 31°. The cohesion was directly proportional to the content of construction waste, whereas the internal friction angle was inversely proportional to calcium bentonite content. The permeability coefficient ranged from 5.04 × 10−6 cm/s to 7.34 × 10−5 cm/s, indicating a certain level of impermeability. Both the sludge and the calcium bentonite contents jointly influenced the final permeability coefficient in a negative correlation manner, with a notable hydraulic hysteresis phenomenon observed. A higher content of construction waste leads to a more pronounced supporting force exerted by the formed skeleton structures within a load pressure range between 0 and 1600 kPa. When considering a mass ratio of municipal sludge: construction waste: calcium bentonite as 30:60:7, respectively, only a decrease in the pore ratio by approximately 13.20% was observed. This study provides valuable data support for designing and applying capillary retarding cover barrier systems in landfills.

Effect of flyash addition to flocculation and freezing and thawing treatment on consolidation of oil sands fluid fine tailings

The total volume of fluid fine tailings (FFT), reached 1,270 Mm3 in 2019. Extensive research is underway by a number of operators to develop dewatering technologies for oil sand tailings reclamation to comply with Directive 085 issued by the Alberta Energy Regulator. A promising technology for the disposal of FFT is to add flocculents and then use thickeners or centrifuges to decrease the water content. Following this treatment, freezing/thawing processes can then be utilized to further dewater the tailings. The effect of flocculation/flyash addition and thickening coupled with freezing/thawing treatments on FFT was investigated by performing large-strain consolidation and shear strength tests on the treated flocculated TTs. It was found that flocculation and thickening treatment increases the hydraulic conductivity of the treated TT which will result in the TT consolidating much faster than the untreated TT. The most important benefit of the flyash addition is the increase in shear strength and hydraulic conductivity of the flyash-treated TTs. The benefit of the freezing/thawing treatment processes coupled with flyash treatment is the increase in the compressibility and hydraulic conductivity at effective stresses lower than 100 kPa and void ratios greater than 1.2, respectively. This will facilitate earlier progressive reclamation required to support hydraulic sand capping.

Experimental and Numerical Investigation of One-Dimensional Electroosmotic Consolidation Based on Segment Inheritance Strategy

The attenuation of effective potential is a significant factor leading to the low postdrainage efficiency in the electroosmotic consolidation and drainage methods. In this study, the influence of the attenuation of effective potential on the electroosmotic consolidation process and the problem of solving the governing equations were investigated. A 102.5-hr one-dimensional electroosmotic consolidation test was performed to monitor the changes in the properties of the soil interior and the soil–electrode interface, and the variation curve of the effective potential in the test model was measured. The time-dependent nature of the potential distribution due to the attenuation of effective potential contradicts the assumption of introducing intermediate variables. To address this key issue, the variation curve of the effective potential was linearly segmented, ensuring the validity of introducing intermediate variables within each local state segment. Based on the continuity between state segments, the initial conditions of the governing equations in different state segments were updated, thereby extending the differential iteration within local state segments to the entire electroosmotic time domain. A finite-difference program for this method was developed using the Python language. Calculations and analyses based on the measured potential data were performed, revealing that a decrease in potential leads to a reduction in the effectiveness of electroosmotic drainage and consolidation in terms of the instantaneous distribution of pore pressure and the overall average degree of consolidation. This method can reflect the influence of the attenuation of effective potential on the pore water pressure during the electroosmotic consolidation process. The research findings of this paper can provide theoretical and numerical support for the improvement and engineering application of the electroosmotic consolidation and drainage method.

Coupling effect of solidification and consolidation on characteristics of the dredged silt.

Dehydration with a plate and frame filter press is a common method for treating dredged silt from rivers and lakes. The silt is often conditioned by the addition of solidifying materials before plate and frame press filtration and, therefore, is subjected to the coupling effect of solidification and consolidation. In this study, consolidation tests of the silt with cement were carried out and compared with the silt after only solidification or only consolidation in terms of moisture content, unconfined compressive strength, and leaching concentration. The test results showed that the moisture content of the silt can be reduced to less than 60% under the coupling action of solidification and consolidation, which was 22% and 4% lower than with solidification only or consolidation only, respectively. The effect of consolidation improved the solidification process; the unconfined compressive strength increased rapidly in the early stage of curing and was 30-150% higher than that of solidified silt. The coupling effects of solidification and consolidation on the leaching concentrations of Ni and Cr in silt were the most significant, and the lowest leaching concentrations were 60% and 90% lower than those of solidified only and consolidated only silt, respectively.

High Temperature Effect on the Engineering Performance of Pumice Added Sand-Bentonite Mixtures

The surrounding soils at energy geo-structures must perform for a long time under high temperatures and thermal cycles. Engineering properties of soils are affected by temperature. Pumice is a thermally durable material and it may be used to increase thermal durability of soils. For this reason, it was aimed to develop thermally durable soil material by adding pumice additive to sand-bentonite mixtures. 10% and 20% pumice were added to 10% and 20% sand-bentonite mixtures and compaction, consolidation, direct shear and hydraulic conductivity tests were performed. The direct shear and hydraulic conductivity tests were performed both at room temperature and 80 °C. The consolidation test results showed that as pumice content increases the total vertical deformation decreased at room temperature. Pumice additive reduced the maximum shear stress values when temperature increased for 10B-90S mixtures. However, the pumice additive increased the internal friction angle of the mixtures at high temperature. It was observed that the hydraulic conductivity increased with increasing temperature. Thermal conductivity measurements showed that pumice additive reduced the thermal conductivity value of the mixtures.

Guar Gum, Gellan Gum Biopolymer Soil Stabilization

In civil engineering and construction, soil stabilization is an important aspect. There are diverse conventional techniques to improve soilproperties and for soil stabilization. This study explores the viability of twotypes of biopolymers, Guar gum and Gellan gum, as sustainable and ecofriendly additives for clayey soil stabilization. Compaction, unconfined compression test, permeability, consistency limit, consolidation tests were performed in the study. The sample for the test has been prepared that biopolymer has been mixed with soil in different proportions. These biopolymers forms hydrogels when they get activated, and it enhances the bonding between soil particles thereby increasing the strength. Treating soilwith biopolymer increases dry unit weight and decreases optimum moisturecontent (OMC).Addition of gum solution reduces friction between soil particles, leading to marginal increase in dry unit weight. Higher the biopolymer content lower is the OMC content and soil become more stiff. The compressive strength and load bearing capacity isfound increasing soilbiopolymerspecimen upon different days of curing. For every tested percentage of treatment the percentage reduction factor rises withbiopolymer concentration due to drop in void ratio that results in a drop in the soil's permeability. Guar Gum and Gellan Gum are used as stabilizers in soil treatment, increasing liquid and plastic limits, shrinkage limit, and viscosity. They activate hydrogels, strengthen bonding activity, and increaseshrinkage limit. The addition of Guar Gum and Gellan Gum improves soil biopolymer mix viscosity and adhesion. The findings of this study positivelyimply that adding this material to weak soil would improve the soil’s characteristics.

An interpretation of thermo-mechanical behaviour of peat under 1-D compression

The one-dimensional thermo-mechanical behaviour of two peats was investigated through consolidation tests, including incremental loadings and constant-rate-of-strain loadings, under a variety of temperature-stress conditions. As an appropriate expression of highly compressible materials, the natural strain was employed instead of conventional engineering strain, which eliminates the apparent stress dependency of the compression index and the coefficient of secondary compression. Test results suggest the applicability of an isotach approach to the two peats used in this study. The temperature dependency of the coefficient of secondary compression defined with natural strain, λ*α, is very small. All the results summarized on the effective stress-strain plane show that there exists a unique Normal Compression Line (NCL) corresponding to each combination of temperature and strain rate. The NCLs are parallel to each other. Finally, in an attempt to construct a constitutive model, the temperature dependency of the NCL was quantified by introducing a constant, λ*T. By using the two parameters, λ*α and λ*T, which describe the strain rate- and temperature-dependent characteristics, respectively, a 1-D thermo-mechanical behaviour observed in this study will be modelled in a simple manner.

Laboratory evaluation of sampling quality of a new A+ sampler for natural fine soils

This paper presents a comparison of sampling disturbance measured by consolidation tests between two high quality samplers and stationary piston samplers. University G. Eiffel and Cerema have used their université Laval sampler and a new sampler on a soft organic clayey soil experimental site. This paper present first the new sampler designed to sample almost undisturbed soil specimens. The objectives of this sampler are to collect natural fine soils such as clay or silt, normally to medium overconsolidated for depths up to 10 m. This sampler is designed to preserve the saturation state of the specimen. An inner diameter of 150mm core barrel allow to keep the sampler relatively compact, even with the size of a ball valve used to close the sampler. Tests on Pont de Cran clayey site are presented and laboratory tests results on specimen sampled using both samplers show the quality of the specimen and the efficiency of the samplers using void ratio criteria.