Liquefaction Resistance Of Sand Research Articles

Effects of partial saturation on the liquefaction resistance of sand and silty sand from Christchurch

The liquefaction resistance of partially saturated soil was experimentally investigated for one clean sand and one silty sand collected from a site in Christchurch, in an area severely affected by liquefaction in the 2010–2011 Canterbury earthquakes. A series of cyclic undrained tests were performed on fully and partially saturated sand and silty sand specimens, in conjunction with evaluation of saturation conditions in situ based on comprehensive field measurements of P-wave velocity (Vp) in Christchurch deposits. The Skempton’s B-value and P-wave velocity were comparatively used as measures for partial saturation in the laboratory. B-value - Vp relationships from the test results indicate that Vp steadily increases with the B-value until a threshold B-value is reached beyond which Vp remains unchanged at values indicating full saturation, i.e. Vp ;≥ ;1600 ;m/s. In general, the liquefaction resistance of tested sand and silty sand increases with a decrease in the B-value or Vp, i.e. with a reduction in the degree of saturation. Furthermore, test results suggest existence of threshold B-values and Vp for tested soils beyond which no significant increase in the liquefaction resistance was observed. This threshold B-values and Vp were found to be dependent on soil type and applied confining stress. The effects of partial saturation on liquefaction strength are different for the sand and silty sand when using Vp as a measure for the degree of saturation. While a gradual rate of increase in liquefaction strength with decreasing Vp is observed for the tested sand, the liquefaction strength of silty sand shows similar gradual increase with a decrease in Vp up to about 800 ;m/s, which is then followed by an abrupt increase in the liquefaction strength for Vp ;< ;800 ;m/s. Generally good agreement between liquefaction strength of tested soils and published data was observed, with a clear distinctive feature in the behaviour of the silty sand as compared to clean sands.

Role of geofoam inclusions on the liquefaction resilience of transportation geostructures

Though the effectiveness of geofoam buffers for improving the dynamic load response and seismic performance of road embankments and retaining walls is well-established, their role on soil liquefaction is not investigated by many. This study explores the potential of Expanded Polystyrene (EPS) geofoam inclusions for liquefaction mitigation in sands through a series of stress-controlled constant volume cyclic simple shear tests. The study quantifies the increase in liquefaction resistance of sand with geofoam inclusions and reduction in modulus degradation and shear deformations and increase in energy dissipation with loading cycles. Effects of geofoam density and thickness of the layer on the liquefaction response were also investigated through systematic series of experiments with geofoam of three different densities and two different thicknesses. Findings from this experimental study suggest that providing a thick low-density geofoam layer provided the maximum benefit among all the inclusions. Fundamental mechanisms governing this improved response are explored through a series of bender element tests. Results from this study confirm the effectiveness of geofoam buffers in mitigating liquefaction in granular soils and recommend their use in road embankments and retaining walls being constructed in zones of high seismicity to avoid liquefaction and associated lateral spreading failures in these structures.

On the influence of cyclic preloadings on the liquefaction resistance of sands: A numerical study

Soil deposits may be subjected to preloading episodes due to different factors such as previous earthquakes, excavations, refilling, compaction, construction of overlying structures, storms under onshore/offshore conditions, among many others. It is well-known that preloading episodes remarkably influence the subsequent soil mechanical behavior and liquefaction resistance. In order to accurately describe the influence of cyclic preloadings, advanced constitutive models which are able to realistically reproduce the soil mechanical behavior are necessary. In this work, a numerical study was carried out to investigate the influence of cyclic preloadings on the liquefaction resistance of sands. The numerical analyses were performed considering three advanced and well established constitutive models, namely: the hypoplastic model for sands by Von Wolffersdorf (1996) with the Intergranular Strain extension by Niemunis and Herle (1997), the same hypoplastic model for sands extended with Intergranular Strain Anisotropy by Fuentes et al. (2020), and the bounding surface plasticity model Sanisand by Dafalias and Manzari (2004). The simulations were performed based on the experimental databases on Zbraslav sand by Duque et al. (2023a,b). Remarks about the model capabilities and limitations on tests with different types of cyclic preloadings and their repercussion on boundary value simulations are given at the end.

Fabric characteristics of in situ sand with/without liquefaction verified by anisotropy of magnetic susceptibility

It is well known that fabric of sand may significantly affect mechanical behaviors and liquefaction resistance of sand. Various optical techniques are currently utilized to visualize the fabric, especially the distribution of the long axis of soil particles. However, none of these methods provides an ideal solution in laboratory tests and in situ observation. In this study, anisotropy of magnetic susceptibility (AMS) was first proposed as a convenient and efficient way to evaluate the liquefaction of clean sand. At first, investigations with scanning electron microscopy (SEM) and AMS were simultaneously conducted on two groups of soil specimens with different initial fabrics to verify the feasibility of the AMS technique. Then, 80 in situ samples were collected to analyze the feature of liquefied and non-liquefied sand layers through AMS tests. It is clearly known from the test results that the natural sedimentary fabric was destroyed during liquefaction and the fabric anisotropy was greatly changed after liquefaction. The feasibility of evaluating soil fabric using the AMS survey was verified by the laboratory tests. Furthermore, the applicability of AMS in detecting liquefied layer in situ was confirmed for the first time. • Anisotropy of magnetic susceptibility (AMS) was proposed to evaluate liquefaction. • Feasibility of AMS was verified by comparing with an optical method in laboratory. • AMS was used on in-situ samples to detect the anisotropic fabric for the first time.

Insight into excess pore pressure generation leading to liquefaction of sand with stress history under saturated and unsaturated conditions

Assessments of the liquefaction resistance of clean sand still involve considerable uncertainties, which are a current research topic in the field of soil liquefaction. The factors considered and discussed in this study include the loading history, degree of saturation, and partial drainage. The effects of each of these factors on pore pressure generation and liquefaction resistance have been studied for decades in the laboratory, and empirical relationships have been derived. In this paper, an attempt is made to explain these effects using the unique index of volumetric strain. A pore pressure generation model is developed which is similar to that of Martin et al. (1975), but based on stress-controlled triaxial tests. The model is verified through comparisons of its results with those of laboratory tests. It is confirmed that the plastic volumetric strain that has accumulated in sand, either by drained or undrained cyclic loading, dominates the increase in the liquefaction resistance of the sand. However, the plastic volumetric strain caused by overconsolidation is less effective in reducing the volumetric strain potential for subsequent cyclic shearing, thus enhancing its resistance to liquefaction. The model provides a better understanding of the physical processes leading to the liquefaction of saturated and unsaturated sand with and without stress history.

Influence of low fines content on the liquefaction resistance of sands

This paper presents a study of the influence of plastic and non-plastic fines on the resistance of sands to liquefaction. The study is carried out with the aid of a triaxial apparatus on reconstituted sand-fines mixtures at low fines content (≤ 5%). A description of the soils used in this study is first presented followed by the presentation of results of undrained monotonic liquefaction tests performed on sand specimens containing different fines fractions. Experimental results show that the increase in non-plastic fines content up to 5% increases the resistance of sand to liquefaction. Whereas the increase in plastic fines content reveals a decrease in the latter. This result is due to the contribution of the non-plastic fine particles to the overall chain forces and therefore they increase the resistance against liquefaction, however the decrease in the resistance with plastic fines could be attributed to their nature that lead to the sliding between the sand grains and therefore favour the contractancy of the whole specimen.

Microscopic investigation into liquefaction resistance of pre-sheared sand: Effects of particle shape and initial anisotropy

Liquefaction resistance of sand can be either increased or reduced due to an undrained cyclic pre-shearing depending on the degree of pre-shearing, which hinders a better prediction of liquefaction potential to be established. The mechanism of such changes in liquefaction resistance has been poorly understood. This contribution aims to gain micromechanical insights into pre-shearing effects on liquefaction resistance of sand using discrete element method (DEM) simulations. In particular, effects of particle shape and initial anisotropy on liquefaction resistance are investigated. The simulation results from samples consisting of non-spherical particles with an initial anisotropy can qualitatively capture the mechanical responses observed in equivalent laboratory experiments. The samples which yielded a qualitative agreement with the laboratory results are further analyzed micromechanically, and the relationships between liquefaction resistance and some microscopic parameters before cyclic loading are discussed. Microscopic analyses reveal that mean mechanical coordination number is well correlated with liquefaction resistance, whereas liquefaction resistance is less sensitive to anisotropy in particle orientation induced by pre-shearing.

Assessment of lumped particles effect on dynamic behaviour of fine and medium grained sands

One novel aspect addressed here is the effect of the lumped particle on the dynamic behaviour of cohesionless soil. The effects of particle size and fines content on cyclic soil behaviour have been previously studied by mixing fine particles separately with cohesionless soil. The studied cohesionless soil in the quaternary alluvium deposit on Middle Ganga Plain in India contains a significant amount (10%–20%) of soil lumps. Therefore, the present study using strain-controlled cyclic triaxial tests addressed the effect of parameters mentioned above on the liquefaction resistance of sand where the fines were present in a lumped form. A series of undrained cyclic triaxial experiments have been performed on isotropically consolidated samples to quantify the effects of soil lumps present in various types of sand. Experimental results have shown less cyclic resistance for soil samples with lumps compared to clean sands of equivalent grain size. This is believed to be due to lumped particle crushing, and soil particle rearrangement during the sample saturation and loading. This affects dynamic properties such as shear modulus. From the results, it can be concluded that the presence of such soil lumps in cohesionless soil is reducing the initial shear modulus and the soil becomes more susceptible to liquefaction.

An insight into the liquefaction resistance of sand using cyclic undrained triaxial tests: Effect of the relative density and the loading amplitude

Abstract A stability analysis of soils prone to liquefaction based on their undrained shear-strength characteristics is an indispensable challenge in earthquake geotechnical engineering. This paper presents a laboratory study of the influence of relative density on the cyclic behavior of Chlef sand. The experimental program includes undrained, triaxial cyclic tests that were carried out for three different relative densities (Dr = 15, 50 and to 65 %) with various cyclic stress ratios (CSR = 0.15, 0.25 and 0.35). All the samples were consolidated under one initial effective confining pressure σ'c = 100 kPa. The main results show that the increases in the relative density led to significant increases in the shear strength established by an increase in the number of cycles and with an exponential rise. In contrast, it was demonstrated that the number of cycles was decreased when increasing the cyclic stress ratio due to the shearing frequency. The two main effects of the studied parameters did not have the same influence on the cyclic undrained response of the sandy soil submitted to seismic loading: an increase of the deviatoric stress due to the high relative density that participates in the increase of the loading capacity of the compacted soils by minimizing the void ratios, and an increase of the pore-water pressure that has a negative effect on the liquefaction of the soil. From the results obtained, it can be concluded that these two mechanisms led to a global increase of the maximum shearing stress.

Effect of vertical effective and initial static shear stresses on the liquefaction resistance of sands in cyclic direct simple shear tests

To investigate the effect of the vertical effective and initial static shear stresses on cyclic resistance under cyclic loading with principal stress rotation, a series of cyclic direct simple shear tests were conducted on loose and dense Nakdong River sands. The results revealed that the increasing vertical effective stress (σ′v0) often decreased the cyclic resistance, and the decrease was more evident for a high initial static shear ratio (α = 0.2). The degree of reduction of the correction factor Kσ predicted by recommended methods in practice mostly showed more conservative results than the measured Kσ values in this study. Increasing the initial static shear stress decreased the cyclic resistance of the loose sand. For the dense sand, the cyclic resistance either increased or decreased, depending on the combined effect of the σ′v0 and α levels. The correction factor Kα decreased minimally to 0.689 for the loose sand and rose maximally to 1.175 for the dense sand. When the relative density (Dr) increased from 40% to 80%, the increase in the cyclic resistance for a high α (=0.2) was considerably greater than that for α = 0. The cyclic response of the loose sand was due to sudden flow deformation without any apparent shear strain accumulation, regardless of the α value; while the cyclic response of the dense sand indicated plastic strain accumulation. Thus, the cyclic resistance of sand is influenced by the combined effect of Dr, σ′v0, and α, with the potential influence of principal stress rotation.

Effect of fines on liquefaction resistance of sand

To evaluate the effect of non-plastic fines on liquefaction resistance of Babolsar sand, a series of undrained static and cyclic triaxial tests alongside a series of numerical analysis were carried out. The cyclic triaxial tests were conducted in stress-controlled conditions with 1 Hz frequency at 0.35 constant cyclic stress ratio for 50 kPa and 0.25 for 100 and 200 kPa confining pressures. The samples contained 0%, 10%, 20%, 30% and 40% of fine grains. The numerical analysis was performed by a finite difference method, and Finn’s constitutive model was applied to investigate the liquefaction resistance of the mixtures. The tests’ results showed that the number of cycles leading to liquefaction of a sand–silt mixture decreases after increasing fine-grained percentage. Poorer performance in compression and better performance in tension was observed in this situation. The test outcomes also showed that dominant behavior of the mixtures changes from sand to silt at 20% fines content. It was observed from the test results and the numerical analysis that in low percentages of silt, the behavior of the sand–silt mixture is similar to those of the clean sand sample. But by increasing silt, the mixture’s behavior becomes more dependent on contacts between fine and granular particles. The concept presented by Thevanayagam was used to check the contacts between fine and coarse particles. It was also observed that the Finn constitutive model is in good consistency with the test results as long as the behavior of the sand is dominant in the mixture.

Effects of fines content and plasticity on liquefaction resistance of sands

A detailed experimental programme was conducted to evaluate the liquefaction susceptibility of non-plastic and low-plasticity soils subjected to cyclic loading under undrained triaxial loading conditions. The study mainly focused on examining the influence of the amount of fines and plasticity indices on the liquefaction resistance of sands. After mixing silt and clay fractions into fine sand, 16 soil combinations were prepared. The silty sands contained up to 40% non-plastic fines and the low-plasticity soils contained a clay fraction of 5–40%. Each cylindrical soil specimen was constituted to a medium relative density and saturated specimens were subjected to a confinement pressure of 100 kPa. The consolidated specimens were then subjected to various levels of cyclic stress amplitudes using a sinusoidal wave load form at a frequency of 1 Hz. The results showed that both the non-plastic and low-plasticity clay soils were less resistant to liquefaction than the fine sand. The soils belonging to categories SM and SC (silty sand and clayey sand, respectively, as per Indian standard soil classifications) were susceptible to liquefaction if the fines passing through a 75 μm sieve were ≤ 40%, the liquid limit was ≤ 40%, the plasticity index was &lt; 15 and the saturated water content was about 0.86 times the LL.

Influence of particle-size disparity on cyclic liquefaction resistance of silty sands

Liquefaction of silty sands remains puzzling due to the complexity involved in the interaction between coarse and fine particles during loading. This paper presents first-hand experimental data from a series of cyclic triaxial tests under controlled particle characteristics, with the aim to elucidate the influence of particle-size disparity on the liquefaction resistance of sand−fines mixtures. A detailed analysis of the test results and an experimental database compiled from the literature reveal that the particle-size disparity, defined as the ratio between the characteristic sizes of the base sand and the fines, is a major and rational factor controlling the reduction of cyclic resistance of sand−fines mixtures as compared with factors such as the grading and shape of the base sand. A simple, explicit expression is further proposed to properly account for the reduction of cyclic resistance of sand due to fines.

Re-liquefaction of Sand in Shaking Table

Subsequent aftershocks can induce reliquefaction of sand. In the shaking table experiment, the settlement, the excess pore water pressure and the acceleration response of the sand in the process of reliquefaction were measured. It was found that: (1) the liquefaction resistance of sand was the lowest in the second liquefaction, not in the first liquefaction; (2) Liquefaction resistance is depth-dependent, and the soil layer near the surface of soil is most likely to be liquefied; (3) In the model test, the attenuation of seismic shear wave acceleration is not only related to distance but also to the vibration frequency and to the liquefied layer; (4) The amplitude of the acceleration response increases with the number of the shaking. This result indicates that: (1) the phenomenon of re-liquefaction of sand induced by earthquake is not same as that of the first liquefaction. Therefore, the conventional strategy for liquefaction resistance needs to be improved before it can be implemented for analysis of reliquefaction. (2) The attenuation of seismic shear waves in liquefied soil layer has some properties different from the normal soil layer; thus the traditional attenuation calculation method needs improvement in the evaluation in the analysis of site liquefaction.

Effect of fine particles on cyclic liquefaction resistance of sands

ABSTRACT This paper presents an experimental study that investigates the influence of the fines on the initiation of instability of sands under cyclic loading. The materials used for this study and the experimental device are first presented, then the results of typical liquefaction tests for both loose and medium dense specimens are presented with emphasis on the exhibited behaviour. Loose samples have shown a total liquefaction phenomenon however the cyclic mobility phenomenon was initiated for medium dense samples. The results of a series of cyclic undrained tests that were done with the aid of a triaxial apparatus for different percentages of fines are also presented and analysed. The results reveal that the increase in the non-plastic fines content lead to an increase in the liquefaction resistance of sands whereas the increase in the plastic fines lead to a decrease in the resistance to liquefaction.

Investigation of various gram-positive bacteria for MICP in Narmada Sand, India

ABSTRACT In lieu of the conventional carbon-intensive and expensive cement-based ground improvement methods, microbially induced calcite precipitation (MICP) method has gained prominence recently as a sustainable approach to improve the engineering properties of soil. MICP involves calcification by microbial processes, inducing cementation effect in granular soil particles. Several studies have demonstrated the use of Sporosarcina pasteurii bacteria to improve density, stiffness, shear strength, and liquefaction resistance of sand. However, the effects of different bacteria on calcite formation have not been systematically examined in the Indian context. This study investigates MICP in poorly graded, liquefiable Narmada sand, using gram-positive bacteria (i.e. Sporosarcina pasteurii, Bacillus subtilis, and Bacillus sphaericus). Several controlled microbial and cementation media concentrations were tested in sand-filled tubes. Calcite precipitation was analyzed using SEM, FTIR, XRD, and calcimeter. Bacillus subtilis and Bacillus sphaericus resulted in calcite precipitation comparable to that of Sporosarcina pasteurii and can be utilized for sand stabilization.

Liquefaction susceptibility of non-plastic silty sands using hypoplastic model simulations

ABSTRACT A detailed numerical analysis was performed on sands and non-plastic silty sands to examine the soil behaviour under triaxial loading conditions. An advanced hypoplastic soil element model has been used for the numerical simulations. The model parameters are constant for the given soil material and are determined easily by using mathematical formulations after conducting the basic experiments in the laboratory. The numerical model is validated with experimental data of triaxial tests before performing the numerical investigations. It is aimed to study the liquefaction resistance of sand and silty sands based on the critical state line (CSL), steady state line (SSL) and stress ratio at 20% failure strain under static loading. Results indicate that as the fines content increases, the CSL or SSL shifts to downwards, i.e., dilation decreases within the given range of pressures which indicate that the liquefaction susceptibility of sand increases with the addition of the fines content.

Mechanism of improvement of biochar on shear strength and liquefaction resistance of sand

Biochar is a biomass-derived carbonaceous solid product produced by way of pyrolysis, a process whereby thermal degradation of biomass occurs in the absence of or under a limited oxygen environment. To date, little work has been done to assess its effect on soil properties from the geotechnical point of view. A few studies have shown that biochar could increase the shear strength of clays. Results of simple shear tests indicated that although the effect of adding biochar on the drained shear resistance of sand is relatively minor, the liquefaction resistance increased considerably. In this paper, to provide an insight into the mechanism, the interaction between biochar and water was studied in more detail, through an analysis of the biochar chemical active surface, morphological observations of the particles and biochar–water suspension, as well as rheological measurements. It is believed that the mechanism of improvement is related to the active chemicals on the surface and inside the pores of the biochar particles. These volatiles interact with water by repelling it (hydrophobic) and at times by attracting it (hydrophilic), creating a complex network between water and biochar particles that helps to delay the increase in excess pore-water pressure and provides some shear resistance.

Influence of non-plastic fines on the cyclic resistance of sands to liquefaction

This paper presents an experimental study that investigates the influence of the non-plastic fines on the initiation of instability of sands under cyclic loading. The materials used for this study and the experimental device are first presented, then the results of typical liquefaction tests for both loose and medium dense specimens are presented with emphasis on the exhibited behaviour. The results of a series of cyclic undrained tests that were done with the aid of a triaxial apparatus for different percentages of fines are also presented and analysed. The results reveal that the increase in the non-plastic fines content lead to an increase in the liquefaction resistance of sands.

Small-strain shear modulus and liquefaction resistance of sand with carbonate precipitation

Innovative soil improvement methods providing more environmentally friendly solutions for liquefaction countermeasure techniques have emerged in recent years. One such technology is the enzymatically induced calcite precipitation (EICP). This study presents comprehensive experimental results to provide better understanding of the undrained cyclic behavior of an EICP-treated sand. Accordingly, undrained cyclic triaxial tests were performed on the EICP-treated sands with testing parameters including particle size of the sand, confining pressure, calcite contents (CC), and degree of saturation during the precipitation. The effects of these factors on the liquefaction resistance and small-strain stiffness are systematically investigated. The results show two underlying mechanisms that help in enhancing the liquefaction resistance of the calcite-precipitated sand. First, the precipitated calcite binds the sand grains, which directly contributes to improving the mechanical properties. However, this beneficial effect of the calcite bonding between the sand particles is lost if the double-axial amplitude is in the order of 0.5%. Second, an enhanced dilative nature is observed because of the relative angularity provided by the calcite crystals or the ratio of the crystal size to the grain size of the sand. The number of cycles required to obtain DA = 5% after achieving DA = 0.5% depends significantly on the relative angularity. It is also confirmed that the amounts of urea and CaCl2 needed to obtain a given liquefaction resistance can be significantly reduced by decreasing the degree of saturation during curing. The shear-wave velocity or small-strain stiffness (G0) of the calcite-precipitated sand increased with increases in the calcite content and confining pressure. Unlike the liquefaction resistance, the effect of the particle size of the sand on the G0 of the treated sand is insignificant. Finally, the relationship between the liquefaction resistance and normalized shear-wave velocity obtained in this study is compared with the empirical one that has been developed and used in practice for evaluating the liquefaction potential of soils in the field. It is found that the existing liquefaction charts are not applicable for assessing the liquefaction resistance of the calcite-treated ground.