Undrained Shear Strength

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Using Piezocone Dissipation Test to Estimate the Undrained Shear Strength (su), Nkt and NΔu Factors in Cohesive Soils

Using Piezocone Dissipation Test to Estimate the Undrained Shear Strength (su), Nkt and NΔu Factors in Cohesive Soils

DOI: 10.4236/gep.2019.78007 97 Journal of Geoscience and Environment Protection good agreement between cone parameters and independently measured soil properties (e.g. Lunne et al., 1997; Yu, 2004; Schnaid, 2009). A theoretical frame is essential, because the CPTu cannot measure the undrained shear strength di- rectly and therefore CPTu assessment of s u relies on a combination of theory and

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Effect of Organic Matter on Swell and Undrained Shear Strength of Treated Soils

Effect of Organic Matter on Swell and Undrained Shear Strength of Treated Soils

Abstract: This paper presents a laboratory and statistical study on swell and undrained shear strength of cemented organic clays blended with eco-friendly (by-product) cementitious materials such as ground granulated blast slag (GGBS) and cement kiln dust (CKD). The presence of organic matter in soils can be very problematic especially during construction of infrastructures such as roads and foundations. Therefore, experimental and statistical investigations are crucial to further understand the effect of organic matter on swell and strength performance of soils treated with by-product materials (GGBS and CKD). Five artificially synthesised organic clays with 0%, 5%, 10%, 15% and 20% organic matters were mixed with 20% cement during the first phase of mixing. In the second phase, cement content was reduced to 4% and blended with 12% GGBS and 4% CKD respectively. All mixed samples were cured up to 56days and subjected to undrained triaxial test and one- dimensional oedometer swell test. The undrained shear strength of the untreated soils decreases from 22.47kPa to 15.6kPa upon increase in organic matter from 0-20%. While the swell increases from 1.17% to 3.83% for the same range of 0-20% organic matter. The results also show improvement on strength and swell upon addition of 20% cement for all investigated samples. For samples treated with 4% cement and inclusion of 12% GGBS and 4% CKD, the treated soils showed better performance in terms of swell potential due to reduction in plasticity compared to the plasticity of soils treated with 20% cement. Undrained shear strength increases from 632kPa to 804.9kPa and from 549.8kPa to 724.4kPa with reduction in organic matter upon addition of 20% CEM and 4% CEM: 12% GGBS: 4% CKD after 56days. The results obtained show that the inclusion of GGBS and CKD reduced swell and increases undrained shear strength irrespective of the percentage of organic materials due to cementation effect. However, results of the statistical studies show that the presence of organic matter influences the extent of performance of the cement, GGBS and CKD treated soils.
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Effect of using cement admixed with rubber chips on the undrained shear strength of soft soil

Effect of using cement admixed with rubber chips on the undrained shear strength of soft soil

The addition of rubber chips played an important role in the development of undrained shear strength parameters C and φ of cement admixed with rubber chips for soft soil. Table 3 showed the variation in the cohesion and angle of internal friction of natural soil and stabilized soil with different amount of rubber chips for different curing period and Figure 4 and 5 summarized the table. It is observed that for every curing period, the value of cohesion increases while increasing the amount of rubber chips. The highest value of cohesion obtained was 0.70 kN/m 2 at 15% rubber mixture and 7 days curing which is 0.64 kN/m 2
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UNDRAINED SHEAR STRENGTH CHARACTERISTICS OF AN EXPANSIVE SOIL TREATED WITH CERTAIN INDUSTRIAL EFFLUENTS AT DIFFERENT PORE FLUID CONTENT RATIOS

UNDRAINED SHEAR STRENGTH CHARACTERISTICS OF AN EXPANSIVE SOIL TREATED WITH CERTAIN INDUSTRIAL EFFLUENTS AT DIFFERENT PORE FLUID CONTENT RATIOS

. Basically, two mechanisms control the undrained strength in clays, namely (a) cohesion or undrained strength is due to the net attractive forces and the mode of particle arrangement as governed by the interparticle forces, or (b) cohesion is due to the viscous shear resistance of the double layer water (Sridharan, 2002). The Undrained shear strength behaviour of kaolinitic soils is shown to be quite opposite to that observed for montmorillonitic soils under different physico-chemical environments. Concept (a) operates primarily for kaolinitic soil, and concept (b) dominates primarily for montmorillonitic soils. In general fine grained soils consist of different clay minerals with different exchangeable cations and varying ion concentration in the pore water and varying non clay size fraction. In view of this while both concepts (a) and (b) can coexist and operate simultaneously, or one of the mechanisms dominates.
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IMPACT OF A TEST METHOD ON THE UNDRAINED SHEAR STRENGTH OF A CHOSEN FLY ASH

IMPACT OF A TEST METHOD ON THE UNDRAINED SHEAR STRENGTH OF A CHOSEN FLY ASH

The paper presents an assessment of the suitability of a laboratory vane apparatus, a cone penetrometer as well as a shear vane tester and a pocket penetrometer for determination of the parameters of the undrained shear strength of fly ash from the Power Plant “Skawina”. The suitability of the cone penetrometer and the laboratory vane apparatus for the determination of the undrained shear strength of the fly ash has been shown. On the bases of the obtained test results, , drained and undrained shear strengths of the subsoil made of the fly ash under the square pad foundation were calculated according to Eurocode 7. The calculations of the ultimate resistance of the drained subsoil showed that it was several times bigger than its value in undrained conditions. This confirms the need for the proper determination of the angle of internal friction and cohesion as well as the undrained shear strength of fly ashes.
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Undrained shear strength water content relationship for sewage sludge

Undrained shear strength water content relationship for sewage sludge

All the shear strength tests were performed in accordance with BSI (1990b) in a temperature-controlled environment at 218C, considering that the values of coefficients a and b may also be influenced by temperature (Trauner et al., 2005). The specimens were sheared directly after preparation, and the time to failure was short (a maximum of 12.5 min and 22 min in TC and vane- shear tests respectively) in order to determine the remoulded values of undrained shear strength. Otherwise, had the specimens been allowed to stand for any extended period of time, they would have undergone a reduction in the degree of saturation, and of the effective confinement pressure in TC tests, because of
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Characterisation and undrained strength of amorphous clay

Characterisation and undrained strength of amorphous clay

industrial treatment processes. For example, water-treatment residue material (O’Kelly, 2008; Wang et al., 1992) is the organic slurry derived from the production of potable water at municipal works. These materials are characterised by high water content and plasticity, low specific gravity of solids, high compressibility and very low hydraulic conductivity. It is important to note that unlike peats (Mesri and Ajlouni, 2007), paper-mill sludge (Moo- Young and Zimmie, 1996) and to a lesser extent municipal sewage sludge (O’Kelly, 2006), the organic solids in the materials under consideration are predominantly colloidal in size (O’Kelly, 2008). Furthermore, these soils are generally in a saturated, remoulded condition during handling at the municipal or industrial works and subsequent disposal offsite. Hence their undrained shear strength–compressibility–water content relationships can be con- veniently studied using critical-state soil mechanics, adopting the Cambridge stress-path parameters of mean effective stress (p9) and principal stress difference (q) in this study. Also, since these relationships will be applied over a wide range of water content, owing to the high plasticity of these materials, it is appropriate to express the projection of the critical-state line (CSL) on the specific volume against mean effective stress plane (v–p9 plane; Figure 1(a)) in the form (Butterfield, 1979)
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Mechanical properties of dewatered sewage sludge

Mechanical properties of dewatered sewage sludge

Air-dried, compacted sludge material was tested in quick-undrained, triaxial compression and vane shear. The undrained shear strength values measured in triaxial compression and vane shear were consistent. Hence, the vane shear apparatus can be used to quickly assess whether the sludge material has been dewatered sufficiently for landfilling. Undrained shear strength-moisture content plots are presented from which the level of dewatering necessary to facilitate efficient handling of the sludge material, trafficibility at the landfill site and an adequate factor of safety against slope instability for the short-term condition can be determined. The effective stress strength parameters were determined from consolidated-undrained, triaxial compression tests conducted on pasteurized, normally consolidated samples of the sludge material. The mechanical properties of the sludge material changed with the level of sludge digestion. The value of the effective angle of shearing resistance (’) increased from 32 o
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Assessing the shear strength of municipal sludges and residues for landfill disposal

Assessing the shear strength of municipal sludges and residues for landfill disposal

However, relating the strength values determined using different apparatus, and for different test conditions, is often not straightforward (O’Kelly, 2013b, 2013c, 2014a; Oettle et al., 2016) since the different strength measurement apparatus approach the estimation of strength in different ways. For instance, in vane shear, the mobilized strength value is dependent on the vane size, its aspect ratio and the time to reach shear failure, which is a function of the torsional stiffness of the spring in the vane apparatus, the speed of the drive motor to the vane shaft and the undrained shear strength of the test material (O’Kelly, 2013b, 2013c). The effects of differences in the shearing mode, strain rate, specimen confinement pressure and boundary conditions on the mobilized strength value have been investigated for biosolids materials by Kayser et al. (2011) and O’Kelly (2013b, 2013c) and for WTR materials by O’Kelly (2010, 2014a). Compared with inorganic soils, biosolids and WTR materials typically have much higher strain rate dependence (Kayser et al., 2011; O’Kelly, 2014a).
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Liquid Effluent Discharge and Control Management of Surrounding Soil

Liquid Effluent Discharge and Control Management of Surrounding Soil

As shown in Fig. 36, the undrained shear strength of test soils was increased towards maturing period. Similar behavior was observed by George (2014) who found that the unconfined compressive strength of test soils was increased on the addition of chemicals for 7 to 150 days of maturing period which was attributed to the change in the thickness of Diffuse Double Layer (DDL). The results confirmed that the undrained shear strength of test soils increased with increase in carbon percentage as shown in Fig.37. The large increase in inter-particle attraction due to the reduction of diffuse double layer was responsible for the flocculation of the clay mixture. This effect resulted in increased strength of clay mixtures (George, 2014; Ayub et al., 2017).
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ALLUVIAL DEPOSITS AS A SUBSOIL AND MATERIAL FOR BASIC HYDRO-TECHNICAL CONSTRUCTIONS

ALLUVIAL DEPOSITS AS A SUBSOIL AND MATERIAL FOR BASIC HYDRO-TECHNICAL CONSTRUCTIONS

A very important conclusion concerning po- tential in-situ testing methods may be drawn from function (1). The value of s u is not determined di- rectly from CPTU and DMT, and so the value ob- tained from those tests has to be referred through correction formulas to tests directly determining su, such as the vane test, or to laboratory analysis [Mayne, 2009]. Therefore appropriate N kt coeffi- cientneed to be determined for CPTU. The qual- ity of these coefficients will determine the qual- ity of undrained shear strength determined in situ [Młynarek 2010].

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Fallacy of wide undrained strength range at the Casagrande liquid limit

Fallacy of wide undrained strength range at the Casagrande liquid limit

Sridharan and Prakash, 2000; Whyte, 1982). The most signi fi cant variations in the Casagrande-cup devices speci fi ed in national codes are differences in the devices ’ base hardness and resilience values (Haigh, 2016; Whyte, 1982). Casagrande-cup devices are generally categorised as having hard or softer base materials, as, for example, are the ASTM and BSI Casagrande-cup devices, respectively, although the precise nature of a device within each of these categories is not rigidly de fi ned according to Haigh (2016). In terms of mobilised undrained shear strength, softer- base devices produce higher w L(cup) values and hence lower
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A study on chemical stabilization of Oil Sands Mature Fine Tailings

A study on chemical stabilization of Oil Sands Mature Fine Tailings

It is noted that some investigations on MFT fabrics has been done by SEM. Tang et al., (1997) captured the microstructure of the raw MFT, suggesting that MFT had typically ‘card-house’ structure with large pore spaces entrapping bulk of water; Fard (2011) investigated the raw MFT using ESEM technique, and indicated that the clay particles existed not only in the water film, but also at the surface of the sand grains; Liang et al (2015) used SEM to track the fabric changes of MFT induced by the microbial-based treatments and found that the tailing particles united into the large particles after treatment, rendering a higher undrained shear strength; Roshani et al., (2017) performed SEM analysis on the MFT samples being dried in a column with 10m height, and reported that the ‘card-house’ structure (Fig. 2.8) was more prominent at the bottom of the column since evaporation had no influence at that location. This observation was in agreement with a study conducted earlier by Jeeravipoolvarn (2005), who also reported that the samples appeared more compressed with flocculated but dispersed associations at the bottom of the 10m stand pipe.
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PERFORMANCE OF FOOTING WITH MULTI -LAYERED PILE STABILIZED SLOPE

PERFORMANCE OF FOOTING WITH MULTI -LAYERED PILE STABILIZED SLOPE

clayey slopes with a weak thin layer by varying parameters such as ratio of undrained shear strength of weak layer to that of remaining soil mass (0.2-1), ratio of width of slope to that of height of slope (0-12), ratio of distance of pile from toe to that of slope length (0-1), spacing to diameter ratio (0-12) and pile head conditions as free and fixed. He concluded that the pile should be extended half way below the weak layer. The use of fixed head piles increases the effectiveness of stabilizing piles compared with free head piles. He also stated that the middle portion of the slope is the optimal pile position for pile stabilized slope.
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Improvement of soft soil stiffness using geo composite cellular mat

Improvement of soft soil stiffness using geo composite cellular mat

This consisted of rotating a cruciform shaped vane in the test soil to cause a shear test on a cylindrical surface and two planes formed by the vane during its rotation. Hence a cylinder of soil will resist the torque until the soil fails. The torque applied to rotate the vane at a uniform speed was observed. The laboratory vane (12.7mm wide and 12.7mm long) was used to determine the undrained shear strength of soft soil in tube sample (height: diameter ratio of 1) with an area ratio less than 15% to minimise disturbance. The undrained shear strength (C u ) of the soil can be defined as Equation 2.1.
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Simultaneous stabilization of Pb and improvement of soil strength using nZVI

Simultaneous stabilization of Pb and improvement of soil strength using nZVI

Keywords: nZVI; lead, contaminated soil; physicochemical property; undrained shear strength... Nanoscale Zero-Valent Iron nZVI is a well-established nanoparticle that has been used.[r]

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Reappraisal of soil extrusion for geomechanical characterisation

Reappraisal of soil extrusion for geomechanical characterisation

of 40·1 employed in the investigations of various fi ne-grained soils by Kayabali (2011a, 2012) and Kayabali and Tufenkci (2007, 2010a, 2010b). For the slow die displacement rates of typically 1 – 5 mm/min employed, it is entirely plausible that some localised consolidation of the soil billet may occur, caused by drainage of the highly pressurised pore water from the die end of the billet, by way of the extruding soil worm which is under no con fi nement pressure. More pronounced localised consolidation would be expected for stiffer soils that require higher extrusion pressures, those with greater hydraulic conductivity and also for lower die displacement rates, such that the drainage time increases. In this event, the shear strength mobilised in the billet ’ s yielding zone would correspond to a partially drained condition, representing a signi fi cant departure from the extrusion theory that was adopted from metallurgy. If substantiated, this anomaly could adversely impact or possibly even invalidate the RE approach for the determination of the true undrained shear strength for fi ne- grained soil and by association its consistency-limit values. A full review by the author of the pertinent literature produced only two experimental evidences, which are elaborated below, concerning this particular aspect of RE soil testing.
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conservatively estimated using eqn (7). However, as had been pointed out above the soils that were investigated were at water contents that were mainly below their plastic limits. Therefore the authors recommend that the derived equations be used with confidence only when the natural moisture content of a soil sample is equal to or not more than 8% below the plastic limit. Should this condition not be met, then any evaluation of the undrained shear strength from the plasticity index using the above regression equations must be regarded as only an approximate guide. Ultimately, recourse must be made to the triaxial apparatus for the determination of the true undrained strength of a soil.
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Influence of Grain Sizes on Undrained Strength of Sand Mixtures

Influence of Grain Sizes on Undrained Strength of Sand Mixtures

Hence, based on the findings from the literature above, the research on effect of different sizes of sand particles in sand mixtures is still lacking. Existing results are also not conclusive. Therefore, this paper reports some results of a study on investigating the influence of different sizes of sand in sand mixtures in terms of effect to undrained shear strength. Further results could be used to provide as an indicator on liquefaction resistance of sand mixtures. The GDS ELDYN ® triaxial machine was used to carried out the main test (undrained triaxial test).
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Shear strength properties of water treatment residues

Shear strength properties of water treatment residues

Current EU directives (Council of European Union Landfill and Waste Management Directives 1999, 2006) specify a maximum water content of 300% for municipal landfilling of sludge and residues. The landfill operator usually measures the water content value by oven-drying representative test specimens before accepting the residue on site. However, no universal relationship exists for soils between the water content and undrained shear strength, which is used to calculate the short- term factor of safety against geotechnical instability, since the shear strength is also dependent on a range of other factors, including natural differences in the composition of the suspended solids in the source water (effects mineralogy and organic content), the different types of treatments and amounts of chemicals used to separate the residue by-product at the municipal works, the test method, and the degree of specimen saturation. For example, a review of the literature (Novak and Calkins, 1975; Wang et al., 1992; Wichmann and Riehl, 1997) indicates that, at 300% water content, the undrained shear strength of alum WTRs can range between 6 and 80 kPa (Figure 12), although the amounts of chemicals in the residues tested by other researchers were not reported. However, the measured undrained shear strengths of the three alum WTRs tested in this study were more consistent (s u ¼ 40–80 kPa),
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