Undrained Cyclic Shear Research Articles

Effect of sample disturbance on cyclic shear strength of normally to lightly OC clays

Tests on Onsøy clay (Ip = 24–27%) were performed to study the effect of sample disturbance on undrained static and cyclic shear strength. Samples with different degree of disturbance from sampling were used and parallel sets of monotonic and cyclic undrained laboratory tests were performed on block and 54 mm composite piston samples. A silty Drammen clay (Ip = 19%) which was studied earlier was included in the study. Test results indicated that there are significant effects of sample disturbance on both static and cyclic undrained shear strengths for both Onsøy and silty Drammen clays.

Shear Strength Degradation Behavior of Offshore Clay Under Cyclic Loading

Deformation characteristics of Malaysian offshore clay subjected to undrained cyclic constant-volume direct simple shear loading were investigated at different over-consolidation ratios and strain levels. Cyclic strain-controlled tests were undertaken with cyclic shear strain amplitudes ranging from 0.6% to 5%. As the number of cycles increased, it was observed that the cyclic stress amplitude reduced, indicating cyclic degradation, while the pore water pressure increased.

Effect of stress direction on the cyclic resistance of sand

In total, 55 undrained cyclic torsional shear tests were conducted at a constant mean confining stress, σ0m, constant intermediate principal stress ratios, b = (σ2 − σ3)/(σ1 − σ3), and principal stress directions, α. The cyclic resistance of loose, isotropically consolidated specimens exhibited a dip in strength, with the lowest values for α being 45°, an angle at which α was oriented such that the potential shear band directions dovetailed with the plane having the weakest strength (i.e. horizontal plane). For a given α, the cyclic resistance decreased to the lowest values for b = 0·5, at which the value of the principal stresses was different in the three major directions. For dense specimens, the direction of the major principal stress had no significant influence on the cyclic resistance. For loose, anisotropically consolidated specimens, higher cyclic resistances were observed at the point of approaching the direction of the major principal stress during the consolidation and loading stages.

The influence of non-plastic fines on pore water pressure generation and undrained shear strength of sand-silt mixtures

An extensive experimental study was undertaken to investigate the influence of non-plastic fines on pore water pressure generation and undrained cyclic shear strength of sand–silt mixtures. For this purpose, stress-controlled undrained cyclic simple shear (CSS) tests were carried out on reconstituted specimens of Ticino silica sand under different combinations of fines content (FC) and global void ratios (e). The applicability of several models suggested in literature for predicting cyclic residual excess pore water pressure generation in non-plastic silty soils was analyzed, and revised correlations for assessing model parameters were proposed. Finally, the study confirmed that the equivalent granular void ratio (e*) is an effective and appropriate parameter for characterizing the behavior of sand with fines up to a threshold value of fines content of sand-silt mixtures, and cyclic resistance ratio (CRR) of the mixtures can be well correlated with e*, irrespective of their fines contents and void ratios.

Influence of principal stress rotation of unequal tensile and compressive stress amplitudes on characteristics of soft clay

Soil behavior can reflect the characteristics of principal stress rotation under dynamic wave and traffic loads. Unequal amplitudes of tensile and compressive stresses applied to soils have complex effects on foundation soils in comparison with the pure principal stress rotation path. A series of undrained cyclic hollow torsional shear tests were performed on typical remolded soft clay from the Ilexi area of Nanjing, China. The main control parameters were the tensile and compressive stress amplitude ratio (α) and the cyclic dynamic stress ratio (η). It was found that the critical η tended to remain constant at 0.13, when the value of the compressive stress amplitude was higher than the tensile stress amplitude. However, the influence of the tensile stress was limited by the dynamic stress level when α= 1. For obvious structural change in the soil, the corresponding numbers of cyclic vibration cycles were found to be independent of α at low stress levels and were only related to η. Finally, a new method for evaluating the failure of remolded soft clay was presented. It considers the influence of the tensile and compressive stresses which caused by complex paths of the principal stress rotation. This criterion can distinguish stable, critical, and destructive states based on the pore-water-pressure-strain coupling curve while also providing a range of failure strain and vibration cycles. These results provide the theoretical support for systematic studies of principal stress rotation using constitu tive models.

A model for multi-directional cyclic shear-induced pore water pressure and settlement on clays

An estimation method for earthquake-induced pore water pressure and the post-earthquake settlement of soft clay was developed by focusing on its Atterberg’s limits and the direction of cyclic shearing. To clarify the fundamental characteristics of clays with different Atterberg’s limits under multi-directional cyclic shear, normally consolidated specimens of Kaolinite clay, Tokyo bay clay and Kitakyushu clay were subjected to cyclic simple shear under the undrained condition with various cyclic shear directions and shear strain amplitudes, followed by the dissipation of cyclic shear-induced pore water pressure. The effects of undrained cyclic shear on the pore water pressure accumulation and post-cyclic settlement were observed, and relationships with Atterberg’s limits were then investigated. In conclusion, the pore water pressure accumulation and post-cyclic settlement induced by multi-directional cyclic shear increase considerably to a higher level compared with those generated by the uni-directional one and such a tendency is evident for clays with a wide range of Atterberg’s limits. Comparisons of the results indicate that the soil with higher plasticity index shows the lower pore water pressure accumulation and post-cyclic settlement, irrespective of number of strain cycles and shear strain amplitude. Based on these results, a model for earthquake-induced pore water pressure and post-earthquake settlement was developed by incorporating the Atterberg’s limits as a function of experimental constants and the practical applicability was confirmed.

Influence of diatom microfossils on sediment shear strength and slope stability

AbstractDiatom microfossils have been detected in many natural marine sediment deposits around the globe and are held responsible for the disobedience to well‐established geotechnical relationships between index‐properties and shear strength. We revisit the static shear strength and present the first cyclic undrained shear strength experiments on diatom microfossil—clayey‐silt mixtures to study the role of diatoms on submarine slope stability. It is attested that the angle of internal friction (Φ) increases with diatom content, however, we provide evidence for a significant overestimation of Φ in previous studies. Based on direct shear tests at varying normal stresses ≤ 600 kPa we find Φ = 32° in contrast to 43° in pure diatom. Similarly, to static shear strength, cyclic shear strength increases with diatom content, however, in contrast to static shear strength the most drastic increase does not occur from 0% to 25% diatoms but from 75% to 100%. Interestingly, diatomaceous sediments tend to fail by liquefaction although well‐established relations between index properties and liquefaction susceptibility predict the opposite. Liquefaction failure is observed solely in samples containing ≥ 50% diatoms whereas samples with lower diatom content fail by cyclic softening. We conclude diatom microfossils in marine sediments significantly contribute to an increased slope stability under static and cyclic loading conditions since diatoms lead to higher resistance independently of the loading mode. The strength increase is interpreted as a result of particle interlocking and surface roughness, which is very efficient given the highly variable habitus of diatom species.

Plasticity modeling of liquefaction effects under sloping ground and irregular cyclic loading conditions

The formulation of the constitutive model PM4Sand [7] is modified to improve simulations of liquefaction-induced deformations of sloping ground subjected to uniform and irregular cyclic loading. Existing laboratory test data on the response of liquefiable sand under sloping ground conditions subjected to uniform cyclic loading are reviewed and additional experimental data from undrained cyclic direct simple shear (DSS) tests of liquefiable sand under sloping ground conditions subjected to irregular cyclic loading are presented. The previous version of the PM4Sand model (Version 2) and its limitations in modeling liquefaction effects in sloping ground with uniform and irregular cyclic loading are described. Evidence from the laboratory tests show that it is the effect of loading history on the dilation and stiffness characteristics of the response that is not properly captured by Version 2 of the model. The modifications made in Version 3 include a revised dependency of dilation and plastic modulus on the fabric tensor and its history. These modifications are introduced using irregular cyclic DSS test results to illustrate the motivations for the changes in the constitutive equations. Finally, two examples of calibration are presented: one against a specific laboratory test result for a single sand and one against an engineering correlation describing trends observed for many sands across a broader range of relative densities, confining stresses, and loading conditions. The updated formulation in Version 3 of the model is shown to better approximate liquefaction behaviors for sloping ground and irregular cyclic loading conditions.

On the role of volcanic ash deposits as preferential submarine slope failure planes

Volcanic ash deposits have been proposed to potentially liquefy and act as preferential failure planes during submarine landslides along active margins. However, particle angularity and surface roughness of volcanic material significantly influence its shear behavior and hence do not unambiguously support this contention. This manuscript challenges the hypothesis of preferential failure of ash layers by conducting drained and undrained monotonic and undrained cyclic triaxial shear experiments (σ’n < 1 MPa) on volcanic silts/sands and quartz sands as a reference material. Results attest the key role of particle geometry and particle strength in sediment stability. Decreased failure susceptibility of volcanic material compared to smoothed, rounded, and hard-grained quartz sand was attributed to roughness, angularity, and low crushability at low effective confining stresses in drained monotonic and undrained cyclic shear experiments. However, in undrained monotonic shear experiments on soft-grained and porous volcanic material, we observe major weakening due to crushability and excess pore pressure buildup related to particle internal water expulsion. In contrast, hard-grained angular volcanic particles are less susceptible to liquefaction than grain-size equivalent-rounded quartz sand, and may in fact be favorable for seismic strengthening, in which ground shaking causes enhanced settling rather than failure. Our data suggest that ash layers may not serve as preferential failure planes in the majority of earthquake-triggered submarine landslides along active margins.

Influence of fines content on the undrained cyclic shear strength of sand–clay mixtures

A series of undrained cyclic triaxial tests were performed on sand–clay mixtures with various sand–clay mixing ratios. Prior to the primary tests, the threshold fines content was examined by consistency tests, which was found to be approximately 20%. For sand–clay mixtures with a sand-matrix (fines content less than the threshold fines content), the cyclic shear strength of low-density mixtures increases and that of high-density mixtures decreases with increasing fines content. However, for sand–clay mixtures with a fines-matrix (fines content greater than the threshold fines content), there exists a unique correlation between the cyclic shear strength and global void ratio for different fines content. The equivalent granular void ratio is introduced in this paper to account for the contribution ratio of the fines to soil skeleton. As a result, a unique relationship between cyclic shear strength and equivalent granular void ratio was observed for pure sand and sand–clay mixtures with a sand-matrix.

On the influence of initial static shear on large deformation behavior of very loose Toyoura sand in undrained cyclic torsional shear tests

On the influence of initial static shear on large deformation behavior of very loose Toyoura sand in undrained cyclic torsional shear tests

Cyclic liquefaction behaviour of a moderately cemented grouted sand under repeated loading

The aim of this paper is to provide an insight into the effects of a previous cyclic history “triggering” full liquefaction on the subsequent undrained cyclic behaviour of a moderately cemented grouted sand in terms of strength, deformability and pore pressure response. The research was conducted on sand specimens stabilized by a commercial mineral based chemical grout (“Silacsol”), capable of imparting unconfined compression strength (UCS) values ranging between 500kPa and 700kPa. Monotonic shear strength parameters of treated specimens were preliminary assessed through a series of isotropically consolidated drained triaxial tests (TX-CID). Afterwards, stress-controlled undrained cyclic simple shear (SS) tests were conducted on both treated and untreated sand specimens in order to evaluate the improvement provided by the grout on the liquefaction resistance of the sand. A significant beneficial effect of the grout was observed, regardless of the initial density of the pure sand. Finally the influence of a cyclic large preshearing on the undrained cyclic behaviour of the grouted sand was investigated by subjecting the specimens to a sequence of two cyclic loadings with the same stress ratio (CSR). After the first loading in which specimens were brought to full liquefaction, they were allowed to reconsolidate in approximately K0 conditions and then subjected to the second loading. An increase in liquefaction resistance induced by cyclic history was clearly apparent on treated specimens.Excess pore pressures build-up during the first cyclic loading on treated specimens followed a different trend compared to that observed on untreated ones. A significant difference was also observed on the excess pore pressure trends developed in the second loading compared to that developed in the primary loading. A simple model for the prediction of pore water pressure build-up of grouted sands during cyclic loading is proposed.

Pre-shear effect on liquefaction resistance of a Fujian sand

Pre-shear history has been shown to be a critical factor in the liquefaction resistance of sand. By contrast to prior experimental studies in which triaxial shear tests were used to examine the effects of pre-shear on the liquefaction resistance of sand, hollow cylinder torsional shear tests were used in this study to avoid the influence of the inherent anisotropy that is inevitably produced during the sample preparation process because of gravitational deposition. A series of cyclic undrained shear tests were performed on sand samples that had experienced medium to large pre-shear loading. The test results showed that the liquefaction resistance of sand can be greatly reduced by its pre-shear history, and a pre-shear strain within the range from 0.1% to 5% can cause sand to be more prone to liquefaction. During the cyclic shear tests, the samples that had experienced pre-shear loading exhibited different behaviors when cyclic shear loading started in different directions, i.e., the clockwise direction and the counterclockwise direction. If the cyclic loading started in the identical direction as the pre-shear loading, then the mean effective stress of the sand was almost unchanged during the first half of the loading cycle; if the cyclic loading started in the direction opposite to that of the pre-shear loading, then the mean effective stress decreased significantly during the first half of the loading cycle. However, this anisotropic behavior was only remarkable during the first loading cycle. From the second cycle onward, the speeds of the decrease in the mean effective stresses in the two types of shear tests became similar.

A stress–strain description of saturated sand under undrained cyclic torsional shear loading

A constitutive model to describe the cyclic undrained behavior of saturated sand is presented. The increments in volumetric strain during undrained loading, which are equal to zero, are assumed to consist of increments due to dilatancy and increments due to consolidation/swelling. This assumption enables the proposed model to evaluate increments in volumetric strain due to dilatancy as mirror images of increments in volumetric strain due to consolidation/swelling, thus simulating the generation of excess pore water pressure (i.e., reduction in mean effective principal stress) during undrained cyclic shear loading. Based on the results of drained tests, the increments in volumetric strain due to consolidation/swelling are evaluated by assuming that the quasi-elastic bulk modulus can be expressed as a unique function of the mean effective principal stress. On the other hand, in evaluating the increments in volumetric strain due to dilatancy, a normalized stress–plastic shear strain relationship is employed in combination with a novel empirical stress–dilatancy relationship derived for torsional shear loading. The proposed stress–dilatancy relationship accounts for the effects of over-consolidation during cyclic loading. Numerical simulations show that the proposed model can satisfactorily simulate the generation of excess pore water pressure and the stress–strain relationship of saturated Toyoura sand specimens subjected to undrained cyclic torsional shear loading. It is found that the liquefaction resistance of loose Toyoura sand specimens can be accurately predicted by the model, while the liquefaction resistance of dense Toyoura sand specimens may be slightly underestimated. (i.e., the liquefaction potential is higher). Yet, the model predictions are conservative.

Behaviour of Cohesive Soil Subjected to Low-Frequency Cyclic Loading in Strain-Controlled Tests

Abstract The subject of the paper comprises tests of cohesive soil subjected to low-frequency cyclic loading with constant strain amplitude. The main aim of the research is to define a failure criteria for cohesive soils subjected to this type of load. Tests of undrained cyclic shear were carried out in a triaxial apparatus on normally consolidated reworked soil samples made of kaolinite clay from Tułowice. Analysis of the results includes the influence of number of load cycles on the course of effective stress paths, development of excess pore water pressure and stress deviator value. Observed regularities may seem surprising. The effective stress path initially moves away from the boundary surface and only after a certain number of load-unload cycles change of its direction occurs and it starts to move consequently towards the surface. At the same time, it has been observed that pore water pressure value decreases at the beginning and after few hundred cycles increases again. It is a typical behaviour for overconsolidated soil, while test samples are normally consolidated. Additionally, a similar change in deviator stress value has been observed - at first it decreases and later, with subsequent cycles, re-increases.

Analysis Procedure of the Cyclic Bearing Capacity for Suction Anchors in Soft Clays

This article presents a procedure to calculate the bearing capacity of suction anchors subjected to inclined average and cyclic loads at the optimal load attachment point using the undrained cyclic shear strength of soft clays based on the failure model of anchors proposed by Andersen et al. The constant average shear stress of each failure zone around an anchor is assumed and determined based on the static equilibrium condition for the procedure. The cyclic shear strength of each failure zone is determined based on the average shear stress. The cyclic bearing capacity is finally determined by limiting equilibrium analyses. Thirty-six model tests of suction anchors subjected to inclined average and cyclic loads were conducted, which include vertical and lateral failure modes. Model test results were predicted using the procedure to verify its feasibility. The average relative error between predicted and test results is 1.7%, which shows that the procedure can be used to calculate the cyclic bearing capacity of anchors with optimal loading. Test results also showed that the anchor was still in vertical failure mode under combined average and cyclic loads if an anchor was in vertical failure mode under static loads. The anchor failure would depend on the vertical resistance degradation under cyclic loads if an anchor was in lateral failure mode under static loads. Cyclic bearing capacities associated with the number of load cycles to failure of 1000 were about 75% and 80% of the static bearing capacity for vertical failure anchors and lateral failure anchors, respectively.

STUDY ON EXCESS PORE WATER PRESSURE CHANGES OF SATURATED SOFT CLAY SUBJECTED TO UNDRAINED UNI-DIRECTIONAL AND MULTI-DIRECTIONAL CYCLIC SIMPLE SHEARS

In this paper, normally consolidated specimens of kaolinite clay were tested under undrained uni-directional and multi-directional cyclic simple shears. It is shown from the test results that shear strain amplitude (γ), cyclic shear direction (phase difference (θ)) and the number of cycles (n) have significant effects on the changes of excess pore water pressure during cyclic shearing. However, the effect of cyclic shear direction on the excess pore water pressure can be eliminated by using a new parameter - cumulative shear strain (G*). Conventional estimation method of excess ore water pressure can not be used for the case of multi-directional cyclic shear with the number of cycles larger than 50 (n &gt; 50). Consequently, a new estimation method, which is a function of cumulative shear strain was proposed. This method can be applied to various experimental conditions including uni-directional and multi-directional cyclic simples shear with different shear strain amplitudes and number of cycles.ReferencesAnsal, A., Iyisan, R. and Yildirim, H., 2001. “The cyclic behavior of soils and effects of geotechnical factors in microzonation”, Soil Dynamics and Earthquake Engineering, Vol. 21, No. 5, pp. 445-452.DeGroot, D. J., Ladd, C. C. and Germaine, J. T., 1996. Undrained multidirectional direct simple shear behavior of cohesive soil, J. Geotechnical Eng., ASCE, Vol. 122, No. 2, pp.91-98.Fukutake, K. and Matsuoka, H. A., 1989. “Unified law for dilatancy under multi-directional simple shearing”, Journal of JSCE Division C, JSCE, Vol. (412/III-1), pp. 143-151 (tiếng Nhật).Hyodo, M., Yamamoto, Y. and Sugiyama, M., 1994. “Undrained cyclic shear behaviour of normally consolidated clay subjected to initial static shear stress”, Soils and Foundations, Vol. 34, No. 4, pp.1-11.Matsuda, H., 1997. “Estimation of postearthquake settlement-time relations of clay layers”, Journal of JSCE Division C, JSCE, Vol. 568(III-39), pp. 41-48 (tiếng Nhật).Matsuda, H. and Ohara, S., 1989. “Threshold strain of clay for pore pressure buildup”, Proc. of 12h World Conf. on Soil Mechanics and Foundation Engineering, Rio De Janeiro, pp. 127-130.Matsuda, H. and Nagira, H., 2000. “Decrease in effective stress and reconsolidation of saturated clay induced by cyclic shear”, Journal of JSCE Division C, JSCE, Vol. 659(III-52), pp. 63- 75 (tiếng Nhật).Matsuda, H., Shinozaki, H., Okada, N., Takamiya, K. and Shinyama, K., 2004. “Effects of multi-directional cyclic shear on the postearthquake settlement of ground”, Proc. of 13th World Conf. on Earthquake Engineering, Vancouver, B.C., Canada, Paper No. 2890.Matsuda, H., Andre, P. H., Ishikura, R. and Kawahara, S., 2011. “Effective stress change and post-earthquake settlement properties of granular materials subjected to multi-directional cyclic simple shear”, Soils and Foundations, Vol. 51, No. 5, pp. 873-884.Ohara, S., Matsuda, H. and Kondo, Y., 1984. “Cyclic simple shear tests on saturated clay with drainage”, Journal of JSCE Division C, JSCE, Vol. (352/III-2), pp. 149-158 (tiếng Nhật).Ohara, S. and Matsuda, H., 1988. “Study on the settlement of saturated clay layer induced by cyclic shear”, Soils and Foundations, Vol. 28, No. 3, pp. 103-113.Ohmachi, T., Kawamura, M., Yasuda, S., 159 Mimura, C. and Nakamura, Y., 1988. “Damage due to the 1985 Mexico Earthquake and the ground conditions”, Soils and Foundations, Vol. 28, No. 3, pp. 149-159.Yasuhara, K. and Andersen, K. H., 1991. “Recompression of normally consolidated clay after cyclic loading”, Soils and Foundations, Vol. 31, No. 1, pp. 83-94.Yildirim, H. and Ersan, H., 2007. “Settlements under consecutive series of cyclic loading”, Soil Dynamics and Earthquake Engineering, Vol. 27, No. 6, pp. 577-585.

Macroscopic model with anisotropy based on micro–macro information

Physical experiments can characterize the elastic response of granular materials in terms of macroscopic state variables, namely volume (packing) fraction and stress, while the microstructure is not accessible and thus neglected. Here, by means of numerical simulations, we analyze dense, frictionless granular assemblies with the final goal to relate the elastic moduli to the fabric state, i.e., to microstructural averaged contact network features as contact number density and anisotropy. The particle samples are first isotropically compressed and then quasi-statically sheared under constant volume (undrained conditions). From various static, relaxed configurations at different shear strains, infinitesimal strain steps are applied to “measure” the effective elastic response; we quantify the strain needed so that no contact and structure rearrangements, i.e. plasticity, happen. Because of the anisotropy induced by shear, volumetric and deviatoric stresses and strains are cross-coupled via a single anisotropy modulus, which is proportional to the product of deviatoric fabric and bulk modulus (i.e., the isotropic fabric). Interestingly, the shear modulus of the material depends also on the actual deviatoric stress state, along with the contact configuration anisotropy. Finally, a constitutive model based on incremental evolution equations for stress and fabric is introduced. By using the previously measured dependence of the stiffness tensor (elastic moduli) on the microstructure, the theory is able to predict with good agreement the evolution of pressure, shear stress and deviatoric fabric (anisotropy) for an independent undrained cyclic shear test, including the response to reversal of strain.

A large landslide triggered by the 2008 Wenchuan (M8.0) earthquake in Donghekou area: Phenomena and mechanisms

During the 2008 Wenchuan earthquake, more than 60,000 landslides were triggered, resulting in about 20,000 casualties. Among these landslides, a catastrophic one occurred in Donghekou area of Qingchuan County. Donghekou landslide had a volume of about 1×107m3, traveled fast for approximately 2km, killing about 780 people. The source area consisted of unstable sedimentary strata and the runout path was made of colluvial deposits. During the earthquake, the colluvial deposits started to move first, before the arrival of the displaced landslide debris from the main source area. We performed undrained cyclic ring shear tests on samples taken from the runout path and concluded that liquefaction of the runout path material enhanced the mobility of the debris material. A fumarole was identified on the upper part of the runout path 6months later. We analyzed the gas and water venting out, and concluded that the fumarole was not the result of fault movement; it resulted instead from the weathering of slate from the source area. The long-travel landslide materials blocked two rivers, forming two landslide dams that breached with the occurrence of overtopping. To better understand the internal structure of the landslide deposits and then provide evidence for a rational plan of countermeasures to stabilize the landslide dams, we measured the shear-wave-velocity of the landslide deposits by a surface-wave technique called multichannel analysis of surface waves (MASW). The results revealed that the landslide dams consisted of loosely deposited debris, suggesting that the landslide dams were mechanically weak and prone to erosion by overtopping.

Liquefaction characteristics of gap-graded gravelly soils in K0 condition

A series of undrained cyclic direct simple shear tests, which used a soil container with a membrane reinforced with stack rings to maintain the K0 condition and integrated bender elements for shear wave velocity measurement, were performed to study the liquefaction characteristics of gap-graded gravelly soils with no fines content. The intergrain state concept was employed to categorize gap-graded sand–gravel mixtures as sand-like, gravel-like, and in-transition soils, which show different liquefaction characteristics. The testing results reveal that a linear relationship exists between the shear wave velocity and the minor fraction content for sand–gravel mixtures at a given skeleton void ratio of the major fraction particles. For gap-graded gravelly sand, the gravel content has a small effect on the liquefaction resistance, and the cyclic resistance ratio (CRR) of gap-graded gravelly sands can be evaluated using current techniques for sands with gravel content corrections. In addition, the results indicate that the current shear wave velocity (Vs) based correlation underestimates the liquefaction resistance for Vs values less than 160m/s, and different correlations should be proposed for sand-like and gravel-like gravelly soils. Preliminary modifications to the correlations used in current evaluations of liquefaction resistance have thus been proposed.