Figure 7 - uploaded by Nurhan Ecemis
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An illustration of SPT spoon sample and cone penetration test data points with corresponding depths of shear-wave velocity.
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Direct measurement of shear-wave velocity, Vs, in the field to evaluate the liquefaction resistance of soils is an alternative or complement approach to penetration-based methods. However, the existing liquefaction assessment methods established on the Vs have uncertainties about how the fines content and soil-type change the relationship between V...
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... this study, for the soils that have the same geological age (Holocene-age) and geological depositional environments (uncemented deposits), overburden stress corrected V s values with normalized cone penetration resistance for three distinct ranges of non-/low plastic FC by mass of FC ≤ 5 %, 5% < FC ≤ 20%, and 20% < FC ≤ 35%, are shown in Fig. 6a-c. Figure 7 presents how the FC, cone penetration resistance, and V s were selected at the same depths. FC obtained from a 30 cm long soil sample from the SPT spoon. ...
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Citations
... The relationship between cyclic resistance ratio (CRR) and normalized velocity with respect to effective stress (V s1 ) was first suggested by Seed et al., 1 depending on the relationship between penetration blow count number (SPT-N) and V s . In the early 1990s, numerous V s1based liquefaction resistance correlations were proposed by directly measuring V s at sites where liquefaction was observed (e.g., 2,[3][4][5]. In the 2000s, probabilistic and deterministic methods were used to develop CRR-V s1 correlations (e.g., 6,7 ). ...
... Hegazy and Mayne, 52 Andrus et al., 53 Robertson, 40 and Ecemis 5 proposed V s versus q c correlations that interpret the soil-type from I c . At I c values from 1.3 to 2.9, the above-given researchers' curves are plotted in Figure 10 with the proposed trend lines (Figure 9) in this study for comparison. ...
... It should be reminded that some of the CRR-V s1 relationships shown in the figures are based primarily on tests performed on soil samples in the laboratory, [9][10][11][12][13][14][16][17][18][19][20] while the others are based primarily on field case histories. [2][3][4][5]7,8,64 At each figure, the existing (CRR) 7.5 -V s1 curves may reflect dissimilarities due to the differences in sedimentation history, mineralogy, grading characteristics of the soils, and testing conditions. The wide area (possible liquefaction zone) in each subplot representing all the triggering curves proposed in the literature were highlighted in gray. ...
The current simplified liquefaction assessment method based on the shear‐wave velocity, V s has uncertainties about how the fine contents change the V s ‐based liquefaction resistance. According to the simplified method, for a given V s , the cyclic resistance ratio (CRR) increases with an increase in fine contents. However, field investigations recently revealed that for various silty sands, the correlation between CRR and V s is soil‐type index dependent and not specific for all sand‐silt mixtures with the same fine contents. Therefore, a detailed experimental research program is performed in this study to clarify the effect of the soil‐type index on the shear wave velocity and CRR correlation. In the first part of the present study, the cyclic resistance of sand mixed with non‐plastic (NP) fines (dry weight of 0%, 5%, 15%, and 35%) was investigated using cyclic direct simple shear (CDSS) tests. Seismic cone penetration (SCPT) tests were performed inside the large‐scale box to facilitate normalized cone penetration resistance (q c1N ) and shear wave velocity measurements on the soils used in the CDSS tests. A new correlation was proposed between the q c1N and normalized shear wave velocity (V s1 ) using the soil‐type index I c representing the behavior of soil. Then, CRR‐V s1 correlation was obtained experimentally for four distinct ranges of soil‐type index. Finally, the results of this study and the proposed CRR‐V s1 trends in other investigations were used to discuss the soil‐type dependent V s ‐based liquefaction susceptibility zones.
... Liquefaction is a very complicated problem as it may initiate the loss in the shear strength and it has been investigated by many researchers, however; no unique solution has been adopted yet [1]. It was suggested to quantify the average shear stress obtained from the earthquake depending on the grain particle size [5]. The number of blows (N) from the conventional penetration test is another approach used to assess the liquefaction potential. ...
Purpose. To assess the liquefaction of Kirkuk’s industrial region following a series of earthquakes that struck the city during the previous five years based on the current earthquake activity in the region. Methodology. Initially, substantial relationships for shear wave velocity in different types of soil were collected and studied, where the majority of these correlations necessitated the use of standard penetration tests in the field. Indeed, two boreholes were drilled up to a maximum depth of 10 m, and the numbers of blows for conventional penetration tests were measured at various depths in each borehole. The stated shear wave velocity values from the literature, as well as the maximum and lowest shear wave velocity constraints, were employed in a simple technique to estimate the cyclic shear stress induced by earthquake loading. Findings. Based on laboratory and field data, the safety factor against earthquake-induced liquefaction can be determined. When the worst-case scenario was examined using the suggested values of shear wave velocity, the factor of safety against earthquake was reduced by 94 % as the depth increased from 3.5 to 9 m. Originality. No previous study has tried to quantify the liquefaction impact of industrial zone of Kirkuk city as such an important rich-oil area was influenced by series of earthquakes occurrence. More importantly, for the first time field soil samples from on-site boreholes in Kirkuk city have been collected and used for liquefaction assessment since such real field data can be utilized properly in liquefaction evaluation process in the absence of any comparable quantification for the investigated area. Practical value. Precious liquefaction analysis should be performed prior to any proposed project construction in the light of increased earthquake activity in the industrial zone in Kirkuk city (Iraq).
... The cohesion of cohesive sand is weaker than that of clay and the permeability of cohesive sand particles is weaker than that of sand [1]. Cohesive sand formed by the combination of sand and clay particles has the characteristics of weak cohesion and water permeability [2][3][4], and such sand is prone to liquefaction under cyclic loading [5][6][7]. Therefore, the dynamic characteristics of cohesive sand have been studied extensively [8][9][10]. ...
In the Chinese code models for seismic design, the shear wave velocity (Vs)-based model for liquefaction potential assessment is built based on the depth consistency assumption, i.e., the seismic demand is a non-decreasing function of the soil depth. It provides an alternative way to construct empirical models based on past case histories. However, the current Vs-based Chinese code model is deterministic in nature. In this paper, the depth consistency assumption for Vs data is validated with models built within the cyclic stress ratio (CSR) framework. Then, two Vs-based probabilistic models for liquefaction potential assessment are built based on the depth consistency assumption, i.e., a model with explicit consideration of the measurement uncertainty and a model without explicit consideration of the measurement uncertainty. It is found that the performances of the two suggested models are comparable with those of two frequently used models built within the CSR framework and are superior to the Chinese code model. For a site where the measurement uncertainty is not available, the model without explicit consideration of the measurement uncertainty should be used. For a site where measurement uncertainty is available, it is suggested that the model with explicit consideration of the measurement uncertainty should be used as it is more conservative.
Centrifuge shaking table tests were conducted to reveal the intrinsic mechanisms of the effects caused by complicated seismic histories on the liquefaction resistance of a saturated sand deposit. The centrifuge model was shaken by a well-designed seismic sequence including 16 shakings in a certain order. Macroscopic and mesoscopic dynamic responses of the sand deposit were measured and analyzed. Experimental results demonstrated that seismic histories had positive or negative effects on sand liquefaction resistance though sand was densified after previous shakings; these effects were well indicated by the changes in anisotropy characteristics of sand fabric caused by the previous shakings.
