Fall Cone Test Research Articles

Laboratory Study on Vallejo and Scovazzo’s Methods in Estimating the Rheology Parameters of Bentonite and Kaolinite Muds

The mud undrained shear strength and viscosity are the essential parameters in understanding the behavior of mudflow. One of the laboratory test methods to estimate the undrained shear strength and viscosity is Vallejo and Scovazzo’s cylinder strength meter test (CSMT) and flume channel test, respectively. This paper compares the undrained shear strength of kaolin and bentonite muds obtained from the CMST to those obtained using the fall cone and mini vane shear tests and also studies the scale effects in the flume channel test in measuring the mud viscosity at a 20o to 40o slope angles and at various liquidity indexes. The results exhibit that CMST could estimate the undrained strength of mud as low as 0.45 kN/m2 with a liquidity index of up to 5.93. Then, the reduction of the size of the flume channel by half resulted in a mud viscosity of about 2.3 times higher.

Comparative analysis of Atterberg’s limits of fine-grained soil determined by various methods

Determination of the Atterberg?s limits is necessary for the classification of fine-grained soil. That limits can be determined according to the valid standard SRPS EN ISO 17892-12. Two methods are prescribed by the standard for determining the liquid limit: the Casagrande cup and the Fall Cone test, and one method for determining the plasticity limit: the thread-rolling method. In this paper the Fall Cone method was also used as an alternative method to determine the plastic limit. Ten samples of various fine-grained materials, originating from the wider area of the city of Nis, were tested. The classification of all samples was performed based on the results obtained by the methods prescribed by the standard and alternative methods. Comparative analysis shows that the results obtained by applying standard and alternative methods are close, but also that the scattering of results obtained by the Fall Cone method is significantly less, whereas the reproducibility is higher.

Diatoms microfossils and their microstructural effects on the sensitivity of metastable silty-clayey soils

In 2013, an accident occurred in Port of Santana, located at the mouth of the Amazon River, in the State of Amapa, Brazil, comprising a large volume of soft silty-clay soil flowing very fast, for a great distance, towards the bottom of the river. Field tests performed afterwards identified the occurrence of sensitive soil layers at the site. Subsequent laboratory tests verified the presence of diatom microfossils in layers with highest liquidity indices. Owing to peculiarities of the accident, a large research programme started at PUC-Rio, aiming to investigate the role of these biomineral grains on soil behaviour. Thus, based on physical-chemical-mineralogical tests performed on samples from the site, higher sensitivity natural soils from Port of Santana were reconstituted. Chemical, mineralogical and grain size reconstitution was carried out using manufactured soils containing equal proportions of minerals as in the natural soils, but with a difference in the portion of non-plastic siliceous grains: a reconstituted soil used quartz, in silt size, and the other used diatomaceous earth. This article presents and discuss results of undrained shear strength data obtained through laboratory fall cone and vane tests, as well as microstructure analyses - including scanning electron microscopy, mercury intrusion porosimetry and X-ray microtomography - in high sensitivity natural diatomaceous soils and reconstituted soils, in the liquidity index range of 1.0 ≤ LI ≤ 1.6. It is shown the fundamental role of the diatom microfossils in microstructural metastability, impacting the high sensitivity measured in soil reconstituted with diatoms and in natural diatomaceous soils.

Revitalizing dredged soils through chemical-physical combined method: A feasibility study

Dredged soils are often considered as waste and pose significant environmental challenge. The objective of this study is to find the feasibility of utilizing dredged soil from Vizhinjam (MH soil) and Vallarpadam (CH soil) sites for land-filling applications through Chemical-Physical Combined Method (CPCM). Lime and fly ash were used as chemical stabilizers. The optimum percentage of the lime is determined as 6 (wt.%) and fly ash is 10 (wt.%) and 15 (wt.%) for MH and CH soil, respectively. The California Bearing ratio (CBR) increased by 55 and 60%, and Unconfined Compressive Strength (UCS) was enhanced by 61 and 53% for MH and CH soil, respectively. The chemically treated soil is then subjected to various physical treatments. The CPCM effectiveness was evaluated by determining shear strength by fall cone test. Curing by geobags enhanced 77 and 69% increase in shear strength for MH and CH soil, respectively, while vacuum preloading resulted in two times increase over the curing method. Among the physical methods, surcharge using geo-bags was found to be the most effective, as it improved the shear strength by 20–30% when compared to other approaches, making them suitable for reuse as an increase in shear strength contributes to the enhancement of bearing capacity.

Discussion: Development of a Single-Point Method to Determine Soil Plastic Limit Using Fall-Cone Data [Geotech Geol Eng 41:4473–4485, 2023

This discussion article presents a critical appraisal of three empirical correlations developed via multiple regression analysis and presented in the Kayabali et al. [Geotech Geol Eng 41:4473–4485, 2023. https://doi.org/10.1007/s10706-023-02527-0] (the Authors’) investigation for the determination of the soil consistency limits. Specifically, based solely on British Standard (BS) fall-cone (FC) test data, the Authors purport that the correlations given by Equations 2 and 3 of their paper can be used to predict the ASTM rolling-plate plastic limit (i.e., PLRP), while their Equation 4 can be used to predict the BS FC liquid limit (i.e., LLFC). The Authors demonstrated that these correlations gave good predictions of the measured LLFC and PLRP water contents (i.e., wL(FC) and wP(RP), respectively) for 87 fine-grained soils they sourced from different parts of Central Turkey. Employing newly compiled large and diverse consistency limits databases assembled from the published research literature, this discussion article confirms that the Authors’ Equations 2 and 3 generally produce poor wP(RP) predictions for the fine-grained soils comprising these databases, invariably overestimating (often seriously) their measured plastic limit values. Hence, the Discussers recommend that the Authors’ Equations 2 and 3 (being generally unreliable beyond the investigated Turkish soils) should not be used in geotechnical engineering practice. While the Authors’ single-point LLFC method given by their Equation 4 broadly appears as a good wL(FC) predictor for the newly compiled database soils, it is noted that there already exist well-established and standardised single-point LLFC methods.

Predicting Swell in Clay-Sand Mixtures Used in Liners

A method to predict the swellability of clay-sand mixtures is proposed. This model is a modified form of the Studds (1997) prediction model for clay-sand mixtures. The new proposed model uses the laboratory fall cone penetration technique to produce a characterization chart. This chart presents slope levels that can be used to obtain an equation for the final clay void ratio versus the vertical effective stress for clays. The porosity of the clay-sand mixtures was worked out based on a correction factor obtained from compression and porosity measurements in the laboratory. The porosity of the mixture was merged into the clay profile equation to compute the final clay void ratio at a specified stress level, which made it possible to predict the swelling behavior for different and variable stress levels. The swellability slope was obtained using fall cone tests conducted on the fine portion. Mixtures of kaolinite and bentonite were introduced to represent soils with different swell potentials. The fall cone measurements of a few points can be used to establish the swellability relationships for natural clay. Merging fall cone points with the swellability slope chart can define the profile of the vertical effective stress versus the clay void ratio.

Temperature Effects on Atterberg Limits

This study aims to investigate the effects of temperature on Atterberg limits of fine-grained soils with different mineralogies using fall cone tests. It is found in the literature that Atterberg limits are dependent on the clay mineralogy [1, 2] and are subjected to change upon an increase in temperature [3-5]. Measurements of liquid limit at different temperatures reveal sodium smectite is more sensitive to temperature than kaolinite. This observation is justified by relating the evolution of liquid limit to the initial changes of total specific surface areas associated with the physicochemical activity and inter-particle contacts [6]. Measurement of Atterberg limits using the conventional methods of Casagrande’s cup and threading is not very practical when the impact of temperature on these parameters is investigated. The trial and error associated with this method and the time they take may hinder a robust estimation of the liquid and plastic limit. Various studies have shown that Atterberg limits measured using Cone Penetration Test are less subjective and more consistent compared to traditional ways [7-9]. For these reasons, utilizing a Fall Cone Test apparatus and a temperature control unit facilitates the investigation of the impact of temperature on Atterberg limits. In this study, first, the liquid limits measured at room temperature by Fall Cone and Casagrande’s method are compared, and then Cone Penetration is utilized to investigate the evolution of liquid limit with temperature.
 Rhassoul Clay (29.4% Illite, 0.10% Kaolinite, 70.5% montmorillonite) and Illite Clay are considered in this study. The measured penetration values of the cone against moisture content at room temperature for these two clays are plotted in Figure 1. The liquid limit is the water content at which the cone penetrates 20mm into the soil in the cup [10]. Accordingly, Table 1 lists the determined liquid fall cone test and their deviation for the measured Atterberg limits using Casagrande’s cup. This comparison was performed to ensure that the difference between these two methods is not significant and the utilized device was accurate enough.
 To determine the Atterberg limits at higher temperatures (40 °C and 50 °C) and lower temperatures (10 °C), a temperature control unit is used to maintain the temperature of the soil sample during fall cone testing. For this purpose, first, the cup was filled with soil and then wrapped to avoid moisture migration in and out of the sample. The sample was then placed inside the temperature controller for an hour at the desired temperature. After one hour, the sample was swiftly unwrapped, and Cone Penetration test was performed. After the penetration a thermometer was used to measure the temperature at the center of the cup. This measurement showed that the alteration of temperature during the whole process is less than 1°C. Next, more water was added to the batch and then the same steps were followed until enough data points were obtained to estimate the liquid limit. The result of these tests allows for an assessment of temperature effects on Atterberg limits, which would be helpful in the understanding of the influence of temperature on different shear strength parameters of fine-grained soil with regards to their mineralogy.
 Table 2 lists the measured liquid limit values for Rhassoul Clay and Illite clay at different temperatures. The results suggest that the liquid limit of Illite is temperature independent. On the other hand, Rhassoul clay liquid limits was more sensitive to elevated temperatures and did not change with cooling. As mentioned earlier, the liquid limit is directly associated with clay mineralogy and the thermal alteration of soil characteristics [11, 12]. Therefore, the observed thermally-induced change in liquid limit should be discussed with respect to mineralogy. According to Table 1, the Illite liquid limit is temperature independent. Furthermore, Rhassoul clay comprises 70.5% montmorillonite minerals and 29.4% Illite. Providing this and the observed sensitivity of Rhassoul clay to temperature change can be attributed to the montmorillonite constituent. This argument can be further supported by testing more clays with different percentages of montmorillonite and illite.

Utjecaj mineralogije gline na nedreniranu posmičnu čvrstoću pomoću pokusa s padajućim šiljkom

Consistency limits are the basic parameters used as standard inputs for any soil investigation program to evaluate the geotechnical properties of fine-grained soils. The primary objective of this study is to investigate the variations in the undrained shear strength of clays with different plasticity properties based on the fine content, clay mineralogy, and water absorption capacity. To achieve this objective, 33 Fall cone tests were conducted on low-, high-, and very high-plastic clay mixtures. Various blends of different plasticity were ensured by preparing mixtures of Na-montmorillonite (NaM)/Ca-montmorillonite (CaM), Na-montmorillonite (NaM)/Kaolinite (K), and Na-montmorillonite (NaM)/Sepiolite (S). According to the experimental results, the highest liquid limit (LL) was obtained in 100 % NaM clay at 255.07 %, whereas the lowest LL was obtained in 100 % S clay at 33.55 %. Similarly, the highest undrained shear strength was obtained at 160 kPa at 30 % water content in the 100 % NaM clay, whereas the lowest undrained shear strength was obtained at 10 kPa in the 100 % S clay at the same water content. Consequently, based on an experimental framework, empirical equations were obtained which could be used to establish the relationships among cone penetration-water content, liquid limit-clay content, and undrained shear strength-cone penetration.

Flow index-liquid limit relationship by fall-cone tests in clay-sand mixtures

The Fall-cone test is a useful method which can be used in evaluation of many soil index and strength identifiers. In this regard, the flow index is calculated as the slope of the plot of water content against natural logarithm of the penetration depth. This is also a fruitful method used to determine the liquid limit of soils, and evaluation of test results may lead to many parameters related to soil plasticity, i.e. using the flow index. In this study, the changes in the liquid limit and plasticity index of a soil as a function of the flow index were investigated. Later, a simple correlation between the plasticity index and the flow index was obtained, and as a result, the plasticity index was directly calculated. The Fallcone test results show that there is an excellent relationship between the plasticity index and the flow index in soils within a wide range of plasticity level and this relationship is significantly affected from mineralogical properties of components of sand-clay mixtures. A linear relationship with R2 = 0.97 (n = 44) was obtained. As a result, both the liquid limit and the plasticity index of the soils are calculated directly based on the results of the Fall-cone test. In addition, this study compared the results of the standard plasticity chart with the new plasticity chart proposed by Vardanega et al. (2022) for the classifying fine-grained soils. It was shown that the new plasticity chart proposed by Vardanega et al. (2022) can also be used in the classification of both fine-grained soils and clay-sand mixtures. The new plasticity chart by Vardanega et al. (2022) provided modifications on standard plasticity chart. The usefulness of the new chart is also verified by the results of this study, experimental results showed that soil classes -for 115 specimens of 125 total- obtained using Fall-cone tests are in accordance with classifications proposed by Vardanega et al. (2022). According to experimental results, the highest flow index was obtained in %100 bentonite soil at 146.47, while the lowest flow index at 7.20 was obtained in a mixture of 90% sand (SW) −10% bentonite. In 100% pure kaolin clay, the liquid limit was 56.09%, the plasticity index was 27.52% and the flow index was 34.55.

Assessment of shear strength for clay liners using a dynamic probe

Liner-cover layers are top layers normally placed when closing landfill sites. The top layers are commonly subjected to the direct influence of moisture, temperature changes, and erosion. This study proposed the use of a dynamic cone penetrometer as a quick tool to assess the shear strength and density of sand-clay cover liners. Poor areas indicating low shear strength and dry density need to be investigated and identified. Changes in moisture content and dry density affect the soil compressibility and shear strength parameters. A lightweight dynamic probe was found to give reliable shear strength measurements when assessing bentonite sand mixture materials. The impact of the moisture content on the profile of penetration was established and a bilinear relationship between the cone penetration and moisture content is shown. Laboratory fall cone tests were conducted to verify the trends of penetration and the influence of dry density. It was found that a linear function can be established within the wet of the optimum zone of the compaction curve. The tests conducted support the effectiveness of using dynamic cone penetrometers for measurements and evaluation of shear strength and dry density for sand clay cover liners. This will pave the way for using a quick tool for the assessment of compaction uniformity and shear strength of sand clay cover liners.

Sedimentation Behavior of Clays in Response to Pore-Fluid Chemistry: Effect of Ionic Concentration and pH on Its Trends

This study investigates the effect of pore fluid chemistry on the sedimentation trends and liquid and plastic limits within the new fines classification framework for four clayey soils with different specific surface and mineralogy. The sedimentation tests and fall cone tests are performed with seven different ionic concentrations (c = 1 × 10−5 ∼ 1.8 M) and the four target pH values (pH = 3, 5, 7, and 9) for each of the ionic concentrations. Three different sedimentation trends such as flocculated, dispersed, and mixed (at c = 0.0015-to-0.003 M) modes are observed at different ion concentrations and pH conditions of the pore fluids. Three sedimentation parameters named A1, A2 and A3 are defined from the sedimentation curve. The relationship between them implies the salient features of the sedimentation trend for tested clayey soils. These parameters confirm the observed sedimentation modes and the critical ionic concentration; c* ∼ 3 × 10−3 M for AMK and EPK (high specific surface) and c* ∼ 1.5 × 10−3 M for LKW and MI (low specific surface) where notable fabric change occurs. The higher specific surface clays are classified as intermediate electrical sensitive clays whereas the lower specific surface clays are categorized into low electrical sensitivity fines in the new classification chart. A complementary data analysis for the sedimentation parameters and the new fines classification chart reveals that the robust link between distinct sedimentation trends and salient features of clay particles captured in the new fines classification chart can be useful to predict the sedimentation modes of clays with different pore fluid chemistry.

3D-Printable Materials Made with Industrial By-Products: Formulation, Fresh and Hardened Properties

Growing in the field of construction, 3D printing allows to build non-standard shapes and to optimise the use of resources. The development of printable materials requires good control of the fresh state of the material—between mixing and printing, a printable material has to evolve from fluid matter to be pumpable (extrudability) up to a matter supporting its own weight and those of superior layers (buildability). Our researches are focused on printable materials used in large printers, i.e., printers able to build structural pieces for buildings. As many pumps and printers can be used to achieve a wide range of parts, this paper presents a simple method to provide valuable guidance to users when a decision needs to be made about printable materials. In this context, our researches both try to maximise the use of industrial by-products to reduce the environmental cost of printed material and to propose tests easy to carry out in the field. Consequently, on the one hand, some printable materials that mainly include quarry washing fines have been developed and, on the other hand, Fall cone and Vicat tests have been used to determine the printability limit. By not focusing on a single formula, the novelty of this paper is to present to readers some parametric models, i.e., a methodology that can be used according to their own devices and applications. Based on a design of experiments, 20 formulas have been tested. Parameters that influence the quality of printing are highlighted. Mechanical tests results at hardened state and shrinkage measurements are also shown to demonstrate the ability of some formulas to be structural materials: compressive strengths at 28 days between 7.50 MPa and 18.40 MPa.

Recycling of Flash-Calcined Dredged Sediment for Concrete 3D Printing

Due to the large volumes of sediments dredged each year and their classification as waste materials, proper management is needed to efficiently dispose of or recycle them. This study aimed to recycle flash-calcined dredged sediment in the development of an eco-friendly 3D-printable mortar. Mortars with 0, 5, 10, 15, 20, and 30% of flash-calcined sediment were studied. Two tests were carried out to determine the printability of the mixtures. First, a manual gun device was used to examine the extrudability, then a modified minislump test was conducted to assess the buildability and shape-retention ability of the mixtures. Furthermore, the flow table test and the fall cone test were used to evaluate the workability and structural buildup, respectively. The compressive strength was also evaluated at 1, 7, and 28 days for printed and nonprinted mortar specimens. In addition, isothermal calorimetry measurements were conducted on corresponding cement pastes. The results showed that it was possible to print mortars with up to 10% of flash-calcined sediment with the preservation of extrudability and buildability. The results showed that flash-calcined sediment shortened the setting time, decreased the flowability, and enhanced the shape-retention ability. Nonprinted samples with 5% and 10% of flash-calcined sediment showed a similar to higher compressive strength compared to that of the reference mortar. However, printed samples recorded an equal to lower compressive strength than that of nonprinted samples. In addition, no significant change in the hydration process was detected for blended cement pastes compared to the reference cement paste.

Discussion of “Physio-Chemical Properties, Consolidation, and Stabilization of Tropical Peat Soil Using Traditional Soil Additives — A State of the Art Literature Review” by Afnan Ahmada, Muslich Hartadi Sutantoa, Mohammed Ali Mohammed Al-Bareda, Indra Sati Hamonangan Harahapa, Seyed Vahid Alavi Nezhad Khalil Abada, Mudassir Ali Khana

This discussion article provides commenting on the sections of the review paper by Ahmad et al. (the authors) concerning consistency limits determinations for peats and peaty soils, drawing on the writer's experiences regarding the usefulness of liquid limit (LL) and plastic limit (PL) testing/results for these soils in explaining their geotechnical behaviors/properties. From the writer's experience, despite being regularly specified in geotechnical engineering practice and used in research work, the conventional consistency limits tests generally do not produce physically meaningful results when testing peat soils, especially for more fibrous peats. Hence, the writer does not agree with the authors' recommendations on consistency limits testing of peats; namely, they recommended that an utmost effort is needed to improve the quality and standard of the thread rolling test and the fall-cone test for consistency limits determinations of highly organic soils such as peat. Rather than grappling with various known inherent shortcomings of consistency limits testing for peats and other highly organic soils, a suggested way forward for assessing the likely geoengineering behavior/properties of these materials points to the routine measurement of a more useful suite of index tests; namely, their natural water content, organic content, fiber content, and humification (decomposition) level. In this discussion, the above aspects are explored in detail, including greater elaboration of the writer's earlier research work in this area, which was touched on in the authors' paper.

Influence of Pore Fluid Chemistry on Electrical Force-Dominated Fabrics of Fine-Grained Soils: Implications in Submerged Sediments

Structures to mitigate the climate change such as offshore wind farms and geological CO<sub>2</sub> sequestration would be located on coastal regions and offshores. Understanding of fine-grained soil fabrics in submerged conditions can help evaluate the safety of coastal underground constructions such as submarine excavation and slope stability. Fall cone tests for the liquid limit, grain-settling-based sedimentation tests, and ball penetration tests were conducted to investigate soil fabrics in different pore fluids with changes in ionic concentration and permittivity. Based on particle morphology and mineralogy, fine-grained soils were influenced by pore fluid chemistry. Fall cone tests showed the influence of pore fluid chemistry on uniformly mixed soil samples. Fine-grained soils that contained clay minerals such as kaolinite and bentonite showed significant liquid limit changes. Sedimentation tests and ball penetration tests induced fabrics with particle segregation and identified the type of fine-grained soils that could form gravitational force-dominated fabric or electrical force-dominated fabric during natural sedimentation process in submerged conditions.

Machine learning techniques for relating liquid limit obtained by Casagrande cup and fall cone test in low-medium plasticity fine grained soils [Eng. Geol. (2021) 294, 106381

Machine learning techniques for relating liquid limit obtained by Casagrande cup and fall cone test in low-medium plasticity fine grained soils [Eng. Geol. (2021) 294, 106381

Closure to “Advancement in Estimation of Undrained Shear Strength through Fall Cone Tests” by Abhishek Ghosh Dastider, Santiram Chatterjee, and Prasenjit Basu

Closure to “Advancement in Estimation of Undrained Shear Strength through Fall Cone Tests” by Abhishek Ghosh Dastider, Santiram Chatterjee, and Prasenjit Basu

Discussion of “Advancement in Estimation of Undrained Shear Strength through Fall Cone Tests” by Abhishek Ghosh Dastider, Santiram Chatterjee, and Prasenjit Basu

Discussion of “Advancement in Estimation of Undrained Shear Strength through Fall Cone Tests” by Abhishek Ghosh Dastider, Santiram Chatterjee, and Prasenjit Basu

Discussion of “Mohajerani method: Tool for determining the liquid limit of soils using fall cone test results with strong correlation with the Casagrande test” by E. Hrubesova, B. Lunackova and M. Mohyla [Engineering Geology 278 (2020) 105852

The Authors have presented an interesting paper (Hrubesova et al., 2020), which aims (in part) to validate the Moharjerani (1999) calibration approach for establishing the 80 g/30° fall-cone penetration depth equating to the liquid limit by the Casagrande percussion-cup approach, determined according to the British Standard. In this paper, the Discussers present some clarifications on, and state various observations regarding, the approaches adopted in the Hrubesova et al. (2020) investigation, as well as the Moharjerani (1999) calibration approach employed therein. The Discussers also present a description of some relevant literature not covered in the Authors' paper (Hrubesova et al. 2020) aimed at making further clarifications on this important area of geotechnical practice.

Effect of Composition on the Compressibility and Shear Strength of Dredged Cohesive Sediment

Progressively, more dredged sediments are being reused for engineering projects. For example, the Marker Wadden is a new wetland constructed in lake Markermeer, the Netherlands, with dredged cohesive sediments originating from the bed of the lake. Such dredged sediments are often dominated by cohesive sediment particles with varying amounts of sand and organic matter. In addition, during and after the construction process, the material consolidates and is often compressed from a very loose state into a significantly denser condition. To assess the mechanical behavior of this material, the compressibility of the Markermeer dredged sediment samples with various sand and organic matter contents was analyzed with incremental loading oedometer tests, whereas the undrained shear strength was studied using the fall cone test. The behavior was theoretically analyzed assuming a fractal structure of the sediment and applying power law constitutive equations for effective stress, hydraulic conductivity, and undrained shear strength. These constitutive equations, usually used at low initial sediment densities, worked well at the relatively high initial densities studied and proved to be a useful tool to identify the transition fines content TFC. The constitutive equations were put in context with indicators traditionally used in soil mechanics. Samples, each with an identical composition of the fines fraction (particles< 63 μm), but with a sand content varying from 9 to 40%, showed the same compressibility and undrained shear strength behavior when considering the sand a filler material. For a natural sand content of 70%, the behavior was dominated by sand. The organic matter oxidation was observed to drastically decrease the compressibility and the shear strength, and even to decrease the amount of sand needed to exhibit sand-dominated behavior, showing the importance of the reactivity or state of organic matter on the TFC.