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Consistency of Fine-Grained Soils
Published in Alan J. Lutenegger, Laboratory Manual for Geotechnical Characterization of Fine-Grained Soils, 2023
A polished stainless-steel cone is brought down so that the tip just touches the top of the soil/water paste. The cone is then released and allowed to penetrate into the soil. The penetration distance is measured after 5 seconds. While the Casagrande drop cup is in effect a dynamic shear strength test, flow being initiated by the dropping of the cup, the Fall Cone test is a static shear strength test, the depth of penetration of the cone being governed by the shear strength of the soil.
Offshore site investigation
Published in White David, Cassidy Mark, Offshore Geotechnical Engineering, 2017
The fall cone test provides a measure of strength and is commonly used to measure the sensitivity of offshore soils, in addition to the liquid limit. The shear strength sufor a cone of weight Q and penetration depth, h, may be expressed as (Hansbo 1957),
Current practices, problems and the future
Published in John Endicott, Deep Excavations in Soil, 2020
Material property tests determine strength and compressibility and include: Laboratory vane test to measure shear strength of weak soil.Fall cone test to measure the strength of weak soil.Shear box test to measure the shearing rupture strength confined to a horizontal plane when a specimen of soil is also subjected to vertical confining loads. This test is not common now.Triaxial compression test, conducted on a cylindrical specimen placed vertically inside a cell with a confining fluid pressure and subjected to increasing axial loads. This test can be drained or undrained and is commonly adopted to measure shear strength and compressibility, both volumetric compressibility and shear stiffness.Compressibility, in one dimension, requires drainage and is commonly called consolidation. The test apparatus is called an oedometer and subjects a thin circular specimen placed flat and loaded or unloaded with drainage permitted.Triaxial and oedometer tests operate at and report strains of the order of a quarter of 1% upwards. These are relevant to situations in the field such as when a retaining wall moves by one hundredth of its height. However, a 30m deep wall moving by 1% of its depth moves 300mm, which in most urban locations is too much to allow. An allowable movement might be 30mm, which is one tenth of 1% of the height of the wall. It follows that precise estimates of movement for sensitive locations should make use of the stiffness of soil at small strains, which is generally of the order of four to ten times greater than, say, at 1% strain. Dynamic loading in a triaxial cell using Bender Element gauges and the Resonant Column Method measure stiffness of soil at very low stress levels. Bender elements generate and measure shear wave velocity in a specimen of soil. In the Resonant Column Method, the frequency of an input oscillating force is adjusted to obtain the frequency at which resonance occurs. From this, shear elastic modulus and damping properties can be calculated. When designing protection of sensitive buildings, the limiting strains are typically very small and the stiffness of soil at such small strains is generally several times higher than stiffness measured by conventional triaxial tests.
Experimental investigation on the thixotropic effect on the mechanical recovery characteristics of clay–structure interface
Published in Marine Georesources & Geotechnology, 2022
Ning Wang, Yubin Ren, Gang Yang, Anyuan Sun, Qing Yang
Recovery structures due to thixotropic effects are very fragile, and the fall cone test is a less disturbing and more accurate method. Ren et al. (2021) suggested this method as the preferred method for thixotropic tests. The fall cone test is widely used in the measurement of the undrained shear strength and liquid limit, which is more accurate and convenient than the vane shear test (Koumoto and Houlsby 2001; Tanaka et al. 2012; Shahriar, Abedin, and Jadid 2018). In this study, the change in undrained shear strength with time is determined by the fall cone test. The fall cone apparatus is produced for Geonor Geotechnical Instruments Norway (model: G-200), which consists of four cones. The cone used in this article is 100 g in mass and 60 degree in the cone angle. The undrained shear strength of soil measured by this type of cone is in the range of 4.5–40 kPa.
Effect of organic matter content on Atterberg limits and undrained shear strength of river sediment
Published in Marine Georesources & Geotechnology, 2022
Gang Wang, Xia Bian, Ye-Jiao Wang, Yu-Jun Cui, Ling-Ling Zeng
Natural dredged sediment is characterized by high water content and low shear strength (Siham et al. 2008; Schlue, Mörz, and Kreiter 2011; Bian et al. 2016; Develioglu and Pulat 2017; Shahriar, Abedin, and Jadid 2018). With the low strength of dredged sediment, it is difficult to use triaxial tests or direct shear tests to determine the shear strength of river sediment with high water content. Alternative tests were conducted, including the vane shear test (Lu and Bryant 1997; Karakouzian et al. 2003; Schlue, Mörz, and Kreiter 2011; Randolph et al. 2012), the plate penetration test (Inoue, Tan, and Lee 1990; Tan et al. 1991; Gao et al. 2012), and the fall cone test (Hansbo 1957; Wroth and Wood 1978; Tan, 1994; Zentar, Abriak, and Dubois 2009b; Shahriar, Abedin, and Jadid 2018). The fall cone test can be used to determine the values of wL, and is also a simple, reliable, and objective method for determining the undrained shear strength.
Factors influencing undrained strength of fine-grained soils at high water contents
Published in Geomechanics and Geoengineering, 2021
H. B. Nagaraj, M. V. Sravan, B. S. Deepa
Based on the above discussion, it may be concluded that the undrained strength at the liquid limit is usually assumed to be a fixed value. The popular testing methods, namely percussion cup and fall cone are essentially strength-based tests, and they tend to arrive at the liquid limit for a specified testing condition assuming some fixed value of undrained strength. However, following the standard testing procedures, many well-cited publications report variations in undrained strength at the liquid limit obtained by both percussion cup and fall-cone tests. Though the fall-cone test which was initially developed considering a constant cone factor, many reports suggest that cone factor may vary with the soil type and also to a certain extent with moisture content for the same soil. However, to the authors’ knowledge, there are no comprehensive studies which report varying cone factor as influenced by the soil type. Though the authors feel a complete understanding on the fall-cone factor is yet to be established for different soil type, results from the present study show a significant influence of clay mineralogy on the undrained strength, and this is a reflection of the influence of soil type on the undrained strength.