Liquefaction Mitigation Research Articles

Seismic resilience assessment of sheet-pile wharves in liquefiable soils using different liquefaction countermeasures

Seismic resilience assessment is essential for maintaining the functionality of sheet-pile wharves in liquefiable soils, preventing significant damages and minimizing losses during earthquakes. This study delves into the seismic resilience of sheet-pile wharves, focusing specifically on the effectiveness of four different liquefaction countermeasure techniques: anchor lengths, cement deep mixing, stone columns, and soil compaction. As such, an advanced two-dimensional (2D) Finite Element (FE) computational framework is established, motivated by a typical large-scale sheet-pile wharf configuration. Within this framework, a recently developed multi-yield surfaces plasticity model is employed, with the modeling parameters calibrated through undrained stress-controlled cyclic triaxial tests and a centrifuge test. Subsequently, the impacts of these liquefaction countermeasures on the seismic resilience of the sheet-pile wharves are systematically investigated. Additionally, the effectiveness of combining longer anchor lengths with the other three mitigation techniques to enhance the seismic resilience of the sheet-pile wharves are examined. It is demonstrated that the synergistic effects of different liquefaction countermeasures can further reduce the liquefaction potential, thereby improving the seismic resilience. Overall, the FE analysis technique and the resulting insights are highly significant for the seismic resilience assessment of equivalent sheet-pile wharves in liquefiable soils, particularly when implementing such liquefaction mitigation countermeasures.

Liquefaction Mitigation of Saturated Sand Using Ordinary, Filtered, and Geosynthetic-encased Stone Columns in Shaking Table Tests

Liquefaction Mitigation of Saturated Sand Using Ordinary, Filtered, and Geosynthetic-encased Stone Columns in Shaking Table Tests

Stone column strategies for mitigating liquefaction-induced uplift of tunnels

Tunnels embedded in liquefiable soil are frequently subjected to uplift and sustain serious damage during major earthquakes. Mitigation methods to prevent the flotation of these tunnels must be developed and implemented in the natural environment. For this purpose, this study proposes a new method that uses stone columns to enhance soil drainage and mitigate soil liquefaction around tunnels. A circular tunnel in liquefied soil is simulated using a 2D finite element model, PLAXIS 2D, and subjected to a sinusoidal input motion. The tunnel's pre-construction and post-construction scenarios are examined. Parametric studies are carried out to investigate the effect of changing several parameters, such as the distance between stone columns and tunnel springing, the diameter of stone columns, the spacing between stone columns, the number of stone column rows, and the stone column arrangement patterns on the effectiveness of liquefaction mitigation. The study reveals that liquefaction mitigation is enhanced by using stone columns closer to tunnel springing, with larger diameters, less spacing, and more rows of stone columns that are arranged in a square pattern. It also emphasizes the importance of timely implementation of stone columns for maximum benefit.

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.

The improved cyclic resistance of bio-treated sands with various gradations for liquefaction mitigation: Density increase and/or cementation?

MICP (microbial induced calcium carbonate precipitation) method shows a huge potential in solving geological and geo-environmental engineering problems, such as liquefaction mitigation, soil remediation, erosion control, slope stabilization and dust control., due to its low-carbon, sustainable and undisturbing character. For the liquefaction mitigation, previous studies showed the remarkable enhancement in cyclic behavior of bio-cemented soils. Little attention has been paid to how soil gradation affects the effectiveness of MICP method in enhancing soil properties, which is one of the key factors of soil mechanical behavior. MICP method has been mainly used in fine sands (mostly <1 mm) with narrow gradation and a certain number of particles smaller than 75 μm. As a result, few papers discussed the application of bio-cementation to soils with larger grains. In addition, the respective contributions of density increase and cementation on cyclic resistance enhancement is still not clear. In this study, a fine sand (0.1–1 mm), a coarser sand (1–5 mm), and a mixture of both, were used, featuring a larger mean size (d50 mm) and uniformity coefficient (Cu) than in most previous studies. In this study, cyclic undrained triaxial tests were performed to analyze the liquefaction potential of loose and dense untreated specimens, and initially loose treated specimens. Results show that sand gradation has a great influence on the cyclic behavior and MICP effectiveness. For all the sands, the MICP treatment gives rise to a significant increase in cyclic resistance and mitigates liquefaction. This enhancement is due to the formation of cementitious precipitates in the pores or on the surface of particles, which creates (1) bridges between particles and/or change in grain characteristics (i.e., size, roughness, angularity), and (2) an increase in density. For sands with various gradations, these two effects differ in magnitude: in the coarsest sand, the effect of density increase appears to be predominant whereas, in the finest and medium sands, the formation of bonds seems to play the major part. These results are important to evaluate the possibility of using this method to improve cyclic resistance in various sands, and to compare the treatment effect with other techniques.

Induced Partial Saturation: From Mechanical Principles to Engineering Design of an Innovative and Eco-Friendly Countermeasure against Earthquake-Induced Soil Liquefaction

Earthquake-induced soil liquefaction is a catastrophic phenomenon that can damage existing building foundations and other structures, resulting in significant economic losses. Traditional mitigation techniques against liquefaction present critical aspects, such as high construction costs, impact on surrounding infrastructure and effects on the surrounding environment. Therefore, research is ongoing in order to develop new approaches and technologies suitable to mitigate liquefaction risk. Among the innovative countermeasures against liquefaction, Induced Partial Saturation (IPS) is considered one of the most promising technologies. It consists of introducing gas/air bubbles into the pore water of sandy soils in order to increase the compressibility of the fluid phase and then enhance liquefaction resistance. IPS is economical, eco-friendly and suitable for urbanised areas, where the need to reduce the risk of liquefaction must be addressed, taking into account the integrity of existing buildings. However, IPS is still far from being a routine technology since more aspects should be better understood. The main aim of this review is to raise some important questions and encourage further research and discussions on this topic. The review first analyses and discusses the effects of air/gas bubbles on the cyclic behaviour of sandy soils, focusing on the soil volume element scale and then extending the considerations to the real scale. The use of useful design charts is also described. Moreover, a section will be devoted to the effect of IPS under shallow foundations. The readers will fully understand the research trend of IPS liquefaction mitigation and will be encouraged to further explore new practical aspects to overcome the application difficulties and contribute to spreading the use of this technology.

Research on construction parameters of stone columns for liquefaction mitigation in coral reef sand areas

For loose coral reef sand with high fines content located in strong earthquake zones, it is necessary to choose stone columns as a liquefaction mitigation ground improvement method that can consider both drainage and densification functions. Taking the Tibar Bay Port project in East Timor as an example, the bottom-feed technology of vibrating stone columns was developed, and typical coral reef sand sites with different fines contents were selected as trial test areas. Experimental research was performed to study the construction parameters for onshore and offshore stone column processes. Tests showed that the vibratory process control parameters, quality acceptance standards, and control procedures proposed through research meet the anti-liquefaction requirements for both drainage and densification effectiveness. The different construction characteristics of onshore and offshore stone columns were also analyzed. Considering the particularity of underwater stone column construction, the research results can be used for stone columns reinforced grounds similar to coral sand onshore and offshore.

Effect of Microbial Induced Partial Saturation on Liquefaction Mitigation of Sand of Different Relative Densities

Effect of Microbial Induced Partial Saturation on Liquefaction Mitigation of Sand of Different Relative Densities

Self–sensing, anti–liquefaction, and long–term settlement characteristics of calcareous sand seeped by high-concentration colloidal silica

Low–concentration of colloidal silica (usually from 5 to 20 wt%) for liquefaction mitigation has been widely studied. But fewer literatures have focused on higher concentration of colloidal silica for cementing sand. For calcareous sand seeped by 40 wt% colloidal silica, cyclic loadings were performed to explore its anti–liquefaction, long–term settlement and self–sensing characteristics. Cyclic triaxial apparatus were to perform anti–liquefaction and long–term settlement tests, and use self-built setup to perform self-sensing tests. The new findings are as follows: (1) for anti–liquefaction, specimens seeped by 40 wt% colloidal silica can’t achieve liquefaction, i.e., the excess pore pressure ratios cyclically fluctuates between 1 and negative, which is not discovered by lower concentration of colloidal silica in the previous literatures; (2) for long–term settlement, cumulative strain is small after 20,000 cycles, and the cumulative strain is less than 1 % even the cyclic stress ratio (CSR) is greater than 1.1, indicating that the colloidal–silica–cemented sand has good resistance to deformation; (3) self–sensing characteristics have been discovered, i.e., a stress change of 90 kPa can lead to 59.37 % change in electrical resistivity, compared to Portland–cement-treated sand without change of resistivity under the same stress change. When Portland–cemented materials are added with conductive fillers in the previous literatures, they can exhibit self-sensing characteristics, but the stress sensitivity is still two orders lower than colloidal–silica–cemented sand. For colloidal–silica–cemented sand, based on the fact that the dry silica gel is non–conductive and only the salt solution in the micro porous media is conductive, the self–sensing feature can be attributed to the stress–induced deformation of micro conductive–salt–solution–filled channels (i.e., the deformation of conductive network). The above research indicates that colloidal–silica–seeped sand has a potential for self–sensing subgrades in the marine environments.

Assessment of liquefaction potential and damage on the toll road construction in earthquake-prone area, Sleman Regency, Yogyakarta

The construction of toll roads in earthquake-prone areas presents significant challenges due to the potential occurrence of liquefaction, a seismic phenomenon in fine-grained soils losing strength during earthquakes. The research was conducted at a toll road construction site in Sleman Regency, Yogyakarta, an area near the active Opak fault which increases its vulnerability to liquefaction. The objective of this study is to analyse the liquefaction potential and damage on the surface in research area. The method used is simplified procedure by Idriss and Boulanger which assessing the cyclic stress ratio and cyclic resistance ratio based on standard penetration test and laboratory data. Then, Liquefaction Potential Index (LPI) and Liquefaction Severity Index (LSI) are calculated. Finally, vertical displacement caused by liquefied soil is estimated using the post-cyclic reconsolidation model to understand its impact on the surface. The study shows low to very high liquefaction potential at the toll road construction site in Sleman Regency. With a vertical displacement of 4.69 cm to 38.83 cm, surface damage can range from low to extensive, emphasizing the need for liquefaction mitigation in earthquake-prone areas like Yogyakarta during toll road infrastructure planning.

Relief well as liquefaction mitigation option in Mpanau, Sigi, Central Sulawesi, Indonesia

The liquefaction disaster that occurred in Central Sulawesi in September 2018 was not only in the form of flow liquefaction but also a sand boil. Sand boils are caused by excess pore water pressure (PWP) which causes sediment ejecta due to water pressure within the ground. This research focuses on the use of relief wells to relieve excess PWP. During the 2018 disaster, the research location in Mpanau, Sigi, Central Sulawesi, had many sand boil points and the emergence of new water springs after the earthquake. At this point, the increase in PWP presumably resulted from a leaking groundwater basin, thus providing additional pressure. The method used was calculating the Ejecta Potential Index (EPI) and modelling with Seep/w. This calculation determined the amount of PWP that could be released to maintain the comparison between PWP and effective stress. This comparison is also known as the PWP (Ru) ratio and should be kept at less than 0.8, indicating the absence of liquefaction in the layer. This analysis was carried out with the initial conditions without wells and after the presence of wells, then assessing the distance of the wells to eliminate artesian pressure. It was concluded that this mitigation method is appropriate for areas that have groundwater basins with layers prone to aquifer leakage to reduce additional PWP.

State-of-the-Art Review on Utilization of Waste Materials in the Mitigation of Soil Liquefaction

State-of-the-Art Review on Utilization of Waste Materials in the Mitigation of Soil Liquefaction

Development of a simplified method for the assessment of liquefaction mitigation via vertical gravel drains

Development of a simplified method for the assessment of liquefaction mitigation via vertical gravel drains

Liquefaction mitigation of saturated sand using Air injection method under undrained cyclic loading

Liquefaction mitigation of saturated sand using Air injection method under undrained cyclic loading

Evaluation of the horizontal cyclic shear stress on the enclosed soil in DSM grid-improved ground by numerical simulation

Deep soil mixing (DSM) grids are widely used as effective countermeasures against liquefaction hazards. A simplified two-dimensional, nonlinear, finite element model involving DSM grid-improved ground is proposed to investigate the shear stress responses of the enclosed soil. A numerical model with several approximations of longitudinal walls was carefully validated by a centrifuge model test. The waist-shaped depth distribution of the horizontal cyclic shear stress acting on the enclosed soil (i.e., the “waist effect”) was revealed and well explained according to the characteristics of dynamic soil-grid interactions. Attention should be given to the increasing shear load sustained by the underlain layer, which may lead to an unexpected failure. A mathematical model for the shear stress reduction ratio was proposed based on a comprehensive numerical parametric analysis considering varying geometry and shear modulus of the DSM grid with a reasonable range. The proposed evaluation method, along with conventional liquefaction-triggering analysis, can be utilized for the seismic design of DSM grids in liquefaction mitigation. The previous design methods without considering the “waist effect” underestimate the overall horizontal cyclic shear stress acting on enclosed soil.

Electro-cementation of calcareous sand using colloidal silica (CS) nanoparticles and alumina powder

The research investigates the effectiveness of a ground improvement technique that involves the electro-cementation of an onshore calcareous sand containing 95.3% calcium carbonate through a series of laboratory experiments. Colloidal silica (CS) nanoparticles and alumina powder were introduced as pozzolanic materials in the sand, and a direct current (DC) was passed through the sand-silica-alumina mix inside an electrokinetic (EK) cell. The method resulted in the electro-cementation of the calcareous sand through the formation of calcium silicate hydrates (C–S–Hs) and calcium aluminate hydrates (C–A–Hs) as products of the pozzolanic reactions between Ca(OH)2, SiO2 and Al2O3 after electrolysis occurred. Iron-rich cements were also formed by the degradation of anodes. These newly formed compounds changed the nature of the treated soil from a granular material into a rock. Results show that the compressive strength of the resulting rock formation is significantly improved. The treatment can be considered as an artificial lithification process through which the nature of the treated soil was changed from a granular material into a rock formation. The electro-cementation achieved by the treatment was further assessed by spectroscopic analyses including FE-SEM, EDX and XRD, which confirmed the formation of cementing agents within the structure of the treated sand. Potential applications of the technique include caissons, highway construction projects, dune fixation and erosion control, in addition to liquefaction mitigation due to electrolysis of pore water and plugging the pores with cementitious materials.

Editorial: Special Issue on Experimental Investigations from Very Small Strains to Beyond Failure

Abstract This Geotechnical Testing Journal Special Issue on Experimental Investigations from Very Small Strains to Beyond Failure presents selected papers originally submitted to the Eighth International Symposium on Deformation Characteristics of Geomaterials held in Porto, Portugal, from September 3–6, 2023 (IS-Porto 2023). This Symposium aimed at exploring and sharing ideas about the complex stress–strain response of geomaterials, including laboratory methods from very small to large strains; anisotropy and localization; time-dependent response of soils; characteristics of treated, unsaturated, and natural geomaterials; applications in field methods; evaluation of field performance in geotechnical structures; and physical and numerical modeling in geomechanics. The Symposium was a three-day event organized by the Faculty of Engineering of the University of Porto, under the auspices of the Technical Committee TC101 Laboratory Stress Strain Strength Testing of Geomaterials of the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE). This symposium was endorsed by the Portuguese Geotechnical Society (SPG), the Faculty of Engineering of the University of Porto (FEUP), under the activities of the Research Unit Institute of R&amp;D in Structures and Construction (CONSTRUCT) of the Portuguese Foundation for Science and Technology (FCT). Building on the tradition of previous Symposia from Sapporo in 1994 to IS-Glasgow 2019, IS-Porto 2023 brought together more than 240 researchers and practitioners from 37 countries to share their experiences and explore new directions in testing, and in constitutive and numerical modelling of geomaterials. This Special Issue of ASTM International’s Geotechnical Testing Journal assembles eleven papers that illustrate some most recent, innovative, and significant advancements in laboratory equipment and experimental methodologies and procedures for the experimental investigations of soils from very small strains to beyond failure. Although most soil research laboratories are now equipped with the latest technology, in terms of transducers or testing apparatus, the inherent complex nature of soils makes studying them an ongoing challenge. This issue reflects the variety of topics that are still being considered, from difficult terrestrial soils, such as high plasticity stiff sedimentary clays (Sorensen et al. 2023), pumice soils (Hashimoto et al. 2023), gravelly (Nikoonejad and Mohsen Haeri 2023) and residual soils (Cheng and Leong 2023), and mine tailings (Narainsamy et al. 2023), to sampling and testing soils from Mars (Chaparro-López et al. 2023). Characterizing liquefiable soils, particularly partially saturated or gassy soils, and its post-liquefaction behavior continues to remain a subject of investigation, particularly in seismic regions, and is discussed in four papers, with emphasis on the applicability of partial saturation for liquefaction mitigation (Ahmad et al. 2023; Kaminski and Grabe 2023; Mele et al. 2023; Molina-Gómez et al. 2023). Greener methods of soil improvement are also explored, for example, biocementation under chemical damage (Ribeiro et al. 2023). The guest editors of this special issue would like to gratefully acknowledge the dedication and effort of all the authors and peer-reviewers of these papers, and the collaboration of the ASTM Editorial Team in the production of this special issue.

Strength Assessment of Water-Glass Sand Mixtures.

For years, the chemical injection process has aided construction works by increasing the strength and water-sealing efficiency of sandy soil. Despite its growing popularity in projects, such as seismic strengthening and liquefaction mitigation, a unified understanding of how chemically treated soil develops its strength, especially under static conditions, remains elusive. Some studies have proposed that strength is derived from the tensile effects of dilatancy, where shearing of the sandy soil causes expansion, creating tension in the interstitial hydrogel and resulting in negative pressure that consolidates the soil particles. Other studies, however, attribute this strength development to the volumetric shrinkage of the hydrogel, which the authors argue confines and compresses the sandy soil particles. Challenges are encountered with this theory, particularly with respect to the consistency of the volumetric shrinkage measurements and the timing of these measurements in relation to changes in soil strength. The aim of the current research is to shed light on this mechanism by using consolidation drainage triaxial compression (CD) tests to measure the cohesive strength and internal friction angle of chemically enhanced soil. By eliminating the dilatancy-induced negative pressure effects and coupling this with an analysis of the molecular structure of the hydrogel, the present study provides an in-depth look at the strength development mechanism and its durability. This holistic approach not only fills in the existing gaps in the understanding of this mechanism, but also paves the way for optimized construction techniques.

State-of-the-Art Review: Fiber-Reinforced Soil as a Proactive Approach for Liquefaction Mitigation and Risk Management

Soil liquefaction is a phenomenon that occurs in which the behavior of soils changes from solid to viscous liquid due to the effect of earthquake intensity or other sudden loadings. The earthquake results in excess pore water pressure, which leads to saturated loose soil with weaker characteristics and potentially causes large ground deformation and lateral spreading. Soil liquefaction is a dangerous event that can lead to catastrophic outcomes for humans and infrastructures, especially in countries prone to earthquake shaking, where soil liquefaction is considered one of the most prevalent types of ground failure. Hence, precautions to reduce and/or prevent soil liquefaction are essential and required. One of the countermeasures to avoid soil liquefaction is the introduction of fibers in the soil since fibers can act as reinforcement by enhancing the soil’s strength and resistance to liquefaction. The process of including fibers into the soil is known as soil stabilization and is considered one of the ground improvement techniques. Therefore, this paper aims to summarize and review the consequences of adding fiber as a reinforcement technique to overcome the issue of soil liquefaction.

A Review on Impacts and Mitigation of Liquefaction of Soil Around the Tunnels

A Review on Impacts and Mitigation of Liquefaction of Soil Around the Tunnels