Liquefaction Of Sand Research Articles

Exploring liquefaction resistance in saturated and gassy sands at different state parameters

Earthquake-induced liquefaction is a relevant natural hazard due to the damages caused in numerous buildings, facilities and infrastructures worldwide. The damages caused to the infrastructure by this phenomenon are caused by the loss of stiffness and strength in granular soils, which leads to settlements and lateral spreading. Earthquake-induced liquefaction typically occurs in saturated deposits composed of non-plastic soils. Hence, the degree of saturation reduction is considered one of the most favourable and optimistic methods for liquefaction resistance mitigation. This paper explores the earthquake-induced liquefaction in saturated and gassy sands, varying their degree of saturation and state parameters. The state parameter was used to analyse the mechanical behaviour by combining the effects of relative density (or initial void ratio) with confinement pressure. Results show that liquefaction resistance improvement caused by the reduction in the degree of saturation is higher as the state parameter increases. This improvement can be described and quantified by multivariate models integrating the effects of degree of saturation and state parameter on liquefaction resistance. This provides a potential solution for improving the resilience of infrastructures susceptible to earthquake-induced liquefaction.

Enhancing sand liquefaction resistance through microbial-induced partial saturation: An experimental study

The liquefaction potential of saturated sand can be significantly reduced by inducing partial saturation in the soil. Conventional soil liquefaction mitigation methods, namely soil densification, drainage, cementing, and groundwater lowering, pose environmental concerns and are challenging to apply to pre-existing structures. However, the microbially induced partial saturation (MIPS) method is emerging as a novel and eco-friendly approach to mitigate liquefaction. The MIPS method involves microbial denitrification, which produces nitrogen gas and results in a desaturating effect in the saturated soil. The current study conducted a series of stress-controlled undrained cyclic triaxial tests on saturated sandy soil and microbially-desaturated sandy soil under different relative densities and loading conditions. In addition, the study systematically analyzed the effects of temperature and pH on bacterial activity and the denitrification process. Batch experiments were conducted to establish a relationship between the initial nitrate concentration in the bacterial media and the resulting desaturation.Comprehensive analyses of cyclic resistance curves were performed to gain a thorough understanding. Additionally, the study conducts detailed analyses of the accumulation of excess pore pressure and the resulting axial strains and deformation patterns in both treated and untreated sand. This study demonstrates that the MIPS treatment considerably enhances the liquefaction resistance of treated sand.

Assessment of liquefaction potential of sand distributed in the coastal area of Ninh Thuan based on SPT values

The liquefaction potential of sandy soil has been widely investigated in the world for many years, especially after the Niigata and Alaska earthquakes in 1964. In which, the SPT values were mostly used for the evaluation of liquefaction potential. In Vietnam, the potential for soil liquefaction has been recently investigated. In the coastal area of Ninh Thuan province, the sand is widely distributed and often exposed on the surface. Additionally, many wind power farms have been built in this area. Thus, it is necessary to evaluate the liquefaction potential of sand distributed in this area. In this study, the potential for sand liquefaction in the coastal area of Ninh Thuan will be evaluated based on SPT values. Two common methods for evaluation of liquefaction potential proposed by Seed and Idriss; Idriss and Boulanger were employed. The research results show that at peak ground acceleration (amax) = 0.07 g and M = 5.5, the sand in the study area is non-liquefiable (safety factor against liquefaction, FS ( 1.48). However, at amax = 0.18 g and M = 7.5, the FS varies from 0.78 to 3.66 for the Seed and Idriss method and from 0.68 to 2.05 for the Idriss and Boulanger method. In general, the FS obtained from the Seed and Idriss method is higher than that obtained from Idriss and Boulanger method. Nevertheless, this insignificantly affects the overall assessment of liquefaction potential. At amax = 0.18 g and M = 7.5, the sand distributed in the study area can be liquefied at a depth of 17 m. However, it is not liquefied when the Nspt is higher than 28 ((N1) 60cs > 20).

The influence range of the biogas desaturation method for mitigating sand liquefaction

To clarify the influence range and saturation distribution after the biogas desaturation method is applied, a three-dimensional model is established with TOUGH2 software to analyze the effect of construction parameters such as grouting volume, grouting rate, grouting depth, nitrogen source concentration, and soil porosity. After that, the sensitivity of the parameters on the influence range is determined. The grouting volume and soil porosity are the most sensitive to the lateral and vertical influence range, respectively. This study provides a basis for the engineering practice of treating liquefiable subgrade by the biogas desaturation method.

Threshold strain for the accumulation of excess pore-water pressure in saturated coral sands under complex cyclic loading patterns

The liquefaction of coral sands caused by the accumulation of excess pore-water pressure is a major factor contributing to catastrophic events on coral reefs, and accurately estimating this excess pore-water pressure accumulation holds significant importance. High-quality laboratory test results are essential for analytical or numerical calculations. In this study, a new test method is employed to conduct a series of undrained, multi-staged, stress-controlled multidirectional hollow cylinder tests on saturated coral sand under complex loading conditions. The concept of threshold strain (γt) and the method for determining γt of saturated coral sand specimens under complex loading conditions are proposed. The test results demonstrate that γt of saturated coral sand remains insensitive to cyclic loading conditions (including frequency, stress path, and mode) but increases with increasing relative density. The range of volumetric threshold strain, degradation threshold strain, and flow threshold for saturated coral sand under different initial states and cyclic loading conditions are 0.0183%–0.0341%, 0.0242%–0.0454%, and 1.006%–1.614%, respectively. This research provides a novel approach for accurately determining input parameters required for resolving and implementing coupled models in numerical modeling.

Strain energy dissipation during liquefaction of fibre-reinforced sand under undrained cyclic triaxial loading

Strain energy dissipation during liquefaction of fibre-reinforced sand under undrained cyclic triaxial loading

Study on dynamic and failure characteristics of sand and anti-floating safety of tunnel structures under long-term vibration loads of the Beijing subway

Most research into sand liquefaction has predominantly focused on the effects of earthquake ground motion, with a limited exploration into the possibility of sand liquefaction induced under long-term train vibration loads. Therefore, in order to explore the possibility of saturated sand liquefaction under long-term vibration loads of the Beijing subway, this article selected Tongzhou sand to conduct dynamic triaxial tests and obtained the dynamic and failure characteristics of saturated sand under different confining pressures and dynamic stresses. The test results showed that the confining pressure has a greater impact on sand liquefaction. When the confining pressure exceeds 100 kPa, the possibility of liquefaction of Tongzhou sand is fairly limited. Furthermore, a numerical model of an operating tunnel under the influence of long-term train vibration loads is established, and the dynamic response characteristics of the saturated sand and tunnel structure are studied. Numerical simulation results show that the local liquefaction of sand caused by train vibration will not cause the tunnel structure to float. Under local liquefaction conditions at the extremely shallow tunnel base, the soil did not completely lose its bearing capacity, and the displacement of the soil and structure was still dominated by settlement. Changes in tunnel burial depth have a greater impact on segment structure than train vibration loads. Tunnels with a more than 10 m burial depth will not liquefy in saturated sand within one year, and the segment structure is safe. The research results can provide a reference for the anti-floating safety of tunnel structures in similar saturated sand strata.

A quantitative study of the effects of physical properties and external loads on the liquefaction of saturated sand based on an intelligent numerical cyclic triaxial test system

ABSTRACT Soil liquefaction would cause significant damage to the safety of cargo transportation. The aim of this article is to conduct a quantitative study of the influence of the main physical characteristic parameters of saturated sand and external loads on its liquefaction. On the basis of the physical cyclic triaxial test (CTT), the finite element simulation model and PSO-BP neural network prediction model and importance analysis model were optimised in this study. Based on this, an innovative intelligent numerical CTT system for saturated sand was constructed. The research results indicate the influence of external load, effective internal friction Angle and plasticity index on the liquefaction of saturated sand is significant, and the average weight is 40.15%, 29.15% and 25.05%, respectively. In this paper, the relevant research provides a theoretical basis for effective control of sand liquefaction and provides new ideas and feasible solutions for subsequent research on sand liquefaction.

Assessment of Liquefaction Potential by Comparing Semi-Empirical Methods Based on the CPT Test

Abstract Liquefaction is a dangerous and temporary phenomenon whereby water-saturated soil loses all or part of its strength. Undrained conditions associated with cyclic loading increase water pressure in soil pores, thereby reducing effective stress. The aim of this study is, on the one hand, to report on the phenomenon of liquefaction of sand, clay and silt deposits in more or less water-saturated zones in the section located at the heart of the central alluvial plain of the Oued Sebou in the mio-plioquaternary Gharb basin and, on the other hand, to study the ability of semi-empirical methods to correctly assess liquefaction potential, while specifying the most appropriate method for the area studied. The study is based on data from experimental results of static penetrometer tests between the Mnasra - Ouelad Salama zone in the Oued Sebou alluvial plain of Morocco's mio-plio-quaternary Gharb basin, made up of sandy, sandy-clay, sandy-silt and silty-sandy formations, which are more sensitive to liquefaction due to their saturation and grain size. We present and discuss the results of Olsen's method, Juang's method and Robertson's method, which are based on the CPT static penetrometer test, as well as looking at the impact of dynamic loading and soil structure on liquefaction probability index values.

Further development of distinct lattice spring model with Finn model for liquefaction analysis

The hazards associated with sand liquefaction induced by dynamic events are significant. The study of the dynamic stability in hydraulic structures presents an interdisciplinary challenge encompassing both geotechnical engineering and engineering seismology. This study was based on an actual hydraulic engineering project. To effectively predict changes in pore pressure caused by earthquakes, we integrated the Finn constitutive equations into a distinct lattice spring model (DLSM). In this study, the code was customized to accommodate multiple materials simultaneously participating in the calculations, thus simplifying the solution to complex engineering problems. Initially, we validated the DLSM’s liquefaction equation by comparing it with the finite difference method. Subsequently, we conducted a comparative analysis of liquefaction in an engineering project of sluice using the enhanced DLSM. Our analysis indicates that untreated sand has a severe risk of trending toward liquefaction, presenting a hazard to hydraulic engineering. The incorporation of a gridded concrete framework significantly mitigated the seismic-induced pore pressure accumulation and irreversible deformations caused by vibrations. A comparative study showed that concrete retaining walls with concrete supports are more effective at reducing liquefaction hazards and minimizing irreversible deformations in engineering structures.

Revisiting the effect of relative density on cyclic liquefaction of clean and silty sands: the crossing effect

Liquefaction of clean and silty sands remains to be an important problem during earthquakes. Even though many factors are known to influence liquefaction behavior, the influence of density index parameter and fines content (FC) are among the most important parameters. In this study, the effect of relative density (Dr) on liquefaction behavior of clean and silty sands was investigated by cyclic direct simple shear tests on two different silty sands at various FC. Several different relationships affected from Dr are revisited or investigated including number of cycles to liquefaction (NL) and cyclic resistance ratio (CRR). It was found that liquefaction resistance-fines content-relative density relationship is much more complex than previously thought. This is because CRR-Dr lines of clean and/or silty sands may cross each other at specific relative densities, which may cause the liquefaction resistance of a clean sand to be either smaller, equal or greater than the liquefaction resistance of a silty sand with the same base sand dependent on the magnitude of relative density. The mentioned behavior is also confirmed on different clean and silty sands tested in literature.

Undrained dynamic behavior of geogrid-reinforced coral sand

In this research, the reactions of geogrid reinforcement on the dynamic performance of medium-dense coral sand with various cyclic stress ratios were investigated using stress-controlled undrained dynamic triaxial tests. The results indicate that the insertion of geogrid decreases the dynamic deformations, and pore pressure build-up rate, and impeded the liquefaction of coral sand. The liquefaction resistance of coral sand increases with the increase in the number of reinforcement layers. The liquefaction resistance of coral sand reinforced with three-layer and two-layer geogrid increases by 333% and 6% compared to unreinforced ones. The geogrid reinforcement layers can effectively resist the complete stiffness degradation of coral sand under cyclic loading. The coral sand stiffness decays at an accelerated rate as the cyclic stress ratio increases, whereas increasing the number of reinforcement layers reduces the coral sand stiffness degradation rate, especially for three-layer geogrid reinforced coral sand at low cyclic stress ratios. Generally, the geogrid as a reinforcement material to coral sand is considered a better alternative to enhance the engineering properties of coral sand and offers significant prospects in coastal and marine engineering construction with coral sand.

Seismic behavior of irregular underground structures in saturated sand

Sand liquefaction is one of the leading causes of severe earthquake damage. In this study, shaking table tests were carried out to investigate the dynamic interaction between the saturated sand and the irregular subway stations. In this test, a method for the preparation of a liquefiable foundation based on a flexible sensing chain combined with water sedimentation was proposed. Typical test results were interpreted, including the development and spatial distribution of pore pressure, surface subsidence, acceleration, deformation, and dynamic earth pressure. Results show that the spatial distribution of excess pore water pressure is changed by the irregular underground structure, and the liquefiable soil below the bottom plate of the structure can be divided into I, II, and III areas based on the degree of liquefication. The surface subsidence is significantly related to Arias intensity and is concentrated within the range of 5 %–95 % of the intensity. The structural floating is synchronized with the liquefaction of the saturated sand, and the uneven floating and inclination of the underground structure are remarkable, anti-flotation design of underground structures should take into account differences in section forms. During the liquefaction of saturated sand, the foundation soil has conspicuous lateral deformation, especially in the deep soil layer. The shape of the dynamic earth pressure increments turns from triangular to linear, when the foundation soil changes from non-liquefied to liquefied. Compared with the limiting values of the elastic inter-story drift ratio, the maximum inter-story drift ratio of the structure is smaller. The tensile strain responses on the columns, particularly in the lower layer, are more prominent than those at the slabs and side walls.

Crosslinked xanthan gum biopolymer-based soil treatment (BPST) as a new ground improvement material to mitigate seismic liquefaction of loose sand

Crosslinked xanthan gum biopolymer-based soil treatment (BPST) as a new ground improvement material to mitigate seismic liquefaction of loose sand

Seismic fragility curves of circular tunnels in saturated sand

This paper aims to derive seismic fragility curves for circular tunnels constructed in saturated sand. A bounding surface plasticity constitutive model is used to simulate the progressive accumulation of strains and the subsequent buildup of excess pore pressure in saturated sand under undrained conditions with cycles of loading. For comparative analysis, dynamic analyses under drained conditions are also conducted. The fully coupled numerical method, validated by centrifuge shaking table tests, provides a satisfactory explanation for the dynamic characteristics of soil–tunnel systems. On this basis, ten near-fault seismic motions are scaled incrementally to evaluate the dynamic performance under increasing seismic intensity for deriving the fragility curves. The investigation of the optimal intensity measure involves the correlation of structural response with peak ground acceleration/ velocity/ displacement and peak bedrock acceleration, respectively. The safety of tunnels is evaluated by the developed fragility curves, which account for the site effects of sand liquefaction on both structural response and fragility. The developed fragility curves also highlight the impacts of tunnel buried depth and sand relative density on the structural response and fragility of circular tunnels in liquefiable soils, providing a benchmark for the seismic hazard evaluations of underwater tunnels.

Influence of geosynthetics reinforcement on liquefaction and post-liquefaction behaviors of calcareous sand

To provide new insights into the liquefaction and post-liquefaction behaviors of calcareous sand with and without geosynthetics reinforcement, a series of multi-stage cyclic triaxial tests were conducted. The geosynthetics employed in this study include geogrid, geotextile, and geotextile-geogrid composite. The multi-stage tests consist of an initial cyclic loading applied to cause liquefaction, followed by undrained monotonic loading without excess pore pressure dissipation. The effect of different arrangements of reinforcement layer on the behaviors of calcareous sand is examined and discussed in this study. The test results indicate that a unique relationship can be observed between the double amplitude axial strain and the pore pressure ratio of calcareous sand, irrespective of the influence of reinforcement layer arrangement, providing an effective means of predicting the strain at a given pore pressure level. The liquefaction resistance of calcareous sand increases with the increase in the number of reinforcement layer and decreases with the increase in the distance from the first layer of reinforcement to the sample’s top surface. Compared to geogrid and geotextile, the proposed geotextile-geogrid composite exhibits better efficiency in enhancing the liquefaction resistance of calcareous sand. The reinforcement also accelerates the recovery of strength for liquefied calcareous sand and increases the maximum shear strength of sand at large axial strain during the post-liquefaction stage.

Liquefaction and post-liquefaction behaviors of unreinforced and geogrid reinforced calcareous sand

To explore the feasibility of geogrid reinforcement as a promising countermeasure to improve the liquefaction and post-liquefaction resistance of calcareous sand, extensive undrained monotonic and multi-stage triaxial tests were performed on unreinforced and geogrid reinforced calcareous sand with different relative densities. The test results illustrate that pore pressure generation curves of unreinforced and reinforced calcareous sand gradually evolve from S-shaped to hyperbolic-shaped with the increase in relative density, cyclic stress ratio, and effective confining pressure. Following this, a pore pressure model applicable to both unreinforced and reinforced calcareous sand is proposed. The liquefaction resistance of calcareous sand increases with the increase in relative density, whereas an elevated cyclic stress ratio increases its liquefaction susceptibility. A virtually unique relationship can be observed between the liquefaction resistance normalized to the product of phase transformation strength ratio and relative density against the number of cycles for triggering liquefaction, providing an effective means of early assessing sand liquefaction resistance. Moreover, the geogrid exhibits excellent reinforcement efficiency in enhancing the liquefaction resistance of calcareous sand at relative densities of 50% and 70%. During the post-liquefaction stage, increasing relative density and geogrid reinforcement can accelerate the recovery of stiffness and strength for liquefied calcareous sand and improve the post-liquefaction strength. In general, geogrid reinforcement is considered a good alternative to densification for improving the engineering properties of calcareous sand and offers great application prospects in marine engineering construction.

Seismic response of tripod suction bucket foundation for offshore wind turbine in sands

Tripod suction bucket foundation is increasingly used to support offshore wind turbines (OWTs) due to its convenient and low-cost installation and high overturning resistance. However, the seismic response characteristics of OWTs of tripod bucket foundations in sands is not well covered in the literature. Therefore, this study investigates the response of tripod bucket foundations installed in sands and subjected to seismic loads employing advanced three-dimensional finite difference analysis. The variation of pore pressure around suction bucket is evaluated, and the failure mechanism of the tripod bucket foundation in sands is revealed. In addition, the displacement response of the tower, and the acceleration amplification effect of the OWT system are elucidated. It is found that the earthquake magnitude, and sand relative density and liquefaction greatly affect the foundation seismic behavior. The results revealed that the overall rotation of the tripod bucket foundation is primarily due to progressively increasing differential vertical settlement between the foundation sides of ‘single bucket’ and ‘double bucket’ associated with loading direction. It was also found that the sand liquefaction under strong shaking may lead to excessive rotation of the foundation that exceeds the service limit state. The findings from this study can provide guidance for the design of OWT tripod bucket foundations in sands.

Assessment of fabric characteristics with the development of sand liquefaction in cyclic triaxial tests: A DEM study

This paper studies fabric properties with the evolution of sand liquefaction by performing a series of 3D constant-volume cyclic triaxial DEM tests. With calibrated parameters for HN31 sand, the consistency between the obtained DEM results and the counterpart experiments is presented. The evolution of fabric characteristics is then assessed with the coordination number and mechanical coordination number, respectively. For liquefaction issues, the conventional coordination number outperforms the mechanical one since the floating particles with the number of contacts less than or equal to 1 can be fully considered. To analyse the complex inter-particle contacts in a granular assembly, the second-order contact normal fabric tensor is briefly introduced with its important mathematical properties. The second invariant of its deviatoric part can prove to be a proper index describing the degree of anisotropy in the principal fabric space spanned by the three eigenvectors belonging to this tensor. Following the direction of the applied loading, the fabric anisotropy accumulates in a gradual manner and finally reaches a threshold value corresponding to liquefaction triggering on the macro scale. This value is fabric-dependent and thus independent of loading intensity. For gaining a complete insight of sand liquefaction on both the micro and macro scales, the shear strain can act as a bridge to describe the evolution of coordination number and the anisotropy degree, respectively.

A predictive model for determination of sand liquefaction potential based on energy method

The prediction of liquefaction potential of sand under earthquake action is a complicated problem in civil engineering. In this study, gene expression programming (GEP) was used to establish the relationship between the capacity energy required to trigger sand liquefaction and several major parameters. By collecting 85 experimental data and six main parameters, a GEP model was established and the empirical prediction equation was obtained. Three statistical indices were used to evaluate the performance of the GEP model and 11 other existing capacity energy models. The results show that the coefficient of determination (R2), mean absolute error (MAE) and root mean squared error (RMSE) values of all datasets predicted by the GEP model are 0.924, 0.061 and 0.087, respectively. While the R2, MAE and RMSE values of all datasets of the 11 existing capacity energy models are 0.510–0.777, 0.149–0.468 and 0.196–0.653, respectively. It can be concluded that the proposed GEP model has the potential to accurately predict the capacity energy required to trigger sand liquefaction.