Liquefaction Phenomena Research Articles

A Comparative Study on Methods of Estimating Liquefaction for Diyala Soil

The phenomenon of liquefaction is one of the most important problems in engineering projects. It occurs in saturated sandy soils during the occurrence of earthquakes. Methods based on the standard penetration test (SPT) were developed to calculate the liquefaction potential according to the seismic loads. These methods have been developed and updated over time by some researchers. This paper analyses the comparison between methods of calculating liquefaction potential. The case study that was selected for the analysis of the comparison methods is Diyala Governorate soil. The methods that have been chosen for making a comparative analysis are the Japanese method, National Centre for Earthquake Engineering Research 1997 (NCEER) workshop, Task Force Report 2007 (Vancouver) and Boulanger and Idriss 2014. The analysis of results stated that the Boulanger and Idriss method is considered more suitable than others for calculating the potential for liquefaction in Diyala Governorate soil. It is found that the Boulanger and Idriss method has higher safety factor than the two methods (80.7% from Vancouver and 38.8% from the NCEER workshop) and less than the Japanese method

On the Dynamic Soil Behavior under Triaxial and Simple Shear Modes

Abstract Although much has been discussed on the liquefaction phenomenon and cyclic behavior of saturated sands, relatively little has been clarified on the difference between their cyclic behavior...

Liquefaction Phenomena Induced by the 26 November 2019, Mw = 6.4 Durrës (Albania) Earthquake and Liquefaction Susceptibility Assessment in the Affected Area

On 26 November 2019, an Mw = 6.4 earthquake struck the central-western part of Albania. Its impact comprises secondary earthquake environmental effects (EEE) and severe building damage within the Periadriatic and the Tirana Depressions. EEE comprised mainly liquefaction phenomena in coastal, riverine, and lagoonal sites of the earthquake-affected area. From the evaluation of all available earthquake-related data, it is concluded that liquefaction sites are not randomly distributed within the affected area but are structurally and lithologically controlled. The affected areas are distributed within NW–SE striking zones formed in graben-like syncline areas with NW–SE trending fold axes. These graben-like areas are bounded by NW–SE striking marginal thrust faults and are filled with geological formations of Neogene to Quaternary age. These NW–SE striking zones and structures coincide with the NW–SE striking seismogenic thrust fault of the November 2019 earthquake as it is derived from the provided fault plane solutions. An approach for liquefaction susceptibility assessment is applied based on geological and seismological data and on liquefaction inventory. From the comparison of the compiled liquefaction inventory and the susceptibility maps, it is concluded that the majority of the observed liquefaction has been generated in very high and high susceptible areas.

Instability and liquefaction flow slide of granular soils: the role of initial shear stress

Loose granular soil, when subjected to shearing, may collapse rapidly to large strains with a very low residual strength. This flow-type failure, known as flow slide or flow liquefaction, is a major concern in geotechnical applications involving slopes, dams and embankments. A fundamental understanding of the flow liquefaction phenomenon has been established through extensive laboratory experiments on isotropically consolidated sand samples over the past decades. In real situations, however, the element of soil in a slope or dam is not under the isotropic consolidation, but is subjected to a static, driving shear stress prior to external loading. What role played by this static shear stress in the initiation of flow liquefaction is an issue of importance but is not yet fully understood. This paper presents new data from a specifically designed experimental program along with analysis in a sound theoretical context. A marked finding of the study is that the gradient of the flow liquefaction line—which indicates the onset of flow slide in the stress space—is almost uniquely related to the initial state parameter defined in the critical state theory, regardless of the presence or absence of initial shear stress. Based on the characteristics of the observed behavior, an alternative definition for the factor of safety against flow failure is put forward, which takes proper account of the key factors involved and thus is more rational in certain aspects than the conventional one used in engineering practice.

Liquefaction Potential Analysis in Bucharest City as a Result of the Ground Shaking during Strong Vrancea Earthquakes

Bucharest, the capital of Romania with about 2.5 million inhabitants, is frequently struck by intense, damaging earthquakes (2–3 events per century). The Collaborative Research Center 461 (CRC-461) entitled: “Strong Earthquakes - a Challenge of Geosciences and Civil Engineering” was established in July 1996 and ended in December 2007, but some projects continued until 2010. It was funded by the German Research Foundation and involved the University of Karlsruhe which today belongs to Karslruhe Institute of Technology. The CRC aimed strategic research in the field of strong earthquakes with regional focus on the Vrancea seismic events in Romania. Between 1995–2007 several research works were done in Romania, with the support of several Romanian research institutes and the University of Bucharest. One of the research questions was to study the occurring of liquefaction during strong earthquakes within the shallow sandy layers in Bucharest. In suitable conditions, strong earthquakes can cause, under certain geologic conditions, liquefaction and therewith ground failure as sand boils, lateral spreading, or differentiated subsidence. In the present paper we analyze the liquefaction risk for Bucharest. For this purpose, at 10 representative sites in Bucharest, Seismic Cone Penetration Tests (SCPTu) were executed. An area-wide evaluation of the liquefaction probability in Bucharest was established. The factor of safety (FS) against liquefaction and the probability of liquefaction (PL) were computed from the obtained test-data. For the first time, maps of the liquefaction potential index (Li) for Bucharest were outlined. This map shows how severe the liquefaction phenomena might be during strong Vrancea earthquakes in Bucharest, amplifying the site effects. Keywords: hydrogeologic conditions, liquefaction probability, liquefaction hazard, Bucharest city, strong Vrancea earthquakes

Integrating the LSSVM and RBFNN models with three optimization algorithms to predict the soil liquefaction potential

Liquefaction has caused many catastrophes during earthquakes in the past. When an earthquake is occurring, saturated granular soils may be subjected to the liquefaction phenomenon that can result in significant hazards. Therefore, a valid and reliable prediction of soil liquefaction potential is of high importance, especially when designing civil engineering projects. This study developed the least squares support vector machine (LSSVM) and radial basis function neural network (RBFNN) in combination with the optimization algorithms, i.e., the grey wolves optimization (GWO), differential evolution (DE), and genetic algorithm (GA) to predict the soil liquefaction potential. Afterwards, statistical scores such as root mean square error were applied to evaluate the developed models. The computational results showed that the proposed RBFNN-GWO and LSSVM-GWO, with Coefficient of Determination (R2) = 1 and Root Mean Square Error (RMSE) = 0, produced better results than other models proposed previously in the literature for the prediction of the soil liquefaction potential. It is an efficient and effective alternative for the soil liquefaction potential prediction. Furthermore, the results of this study confirmed the effectiveness of the GWO algorithm in training the RBFNN and LSSVM models. According to sensitivity analysis results, the cyclic stress ratio was also found as the most effective parameter on the soil liquefaction in the studied case.

Shaking table tests to investigate the influence of grain shape on tnb he excess pore water pressure

Liquefaction that occurred in the Palu city in 2018 is the most devastating natural phenomena. The liquefaction phenomenon is a condition in which a saturated soil loses its strength due to an earthquake. This study aims to determine the increase in excess pore water pressure in solid particles and void particles after they are subjected to earthquake loading. Testing is done by shaking the table. Earthquake loads are modeled with cyclic loads, which are sine waves with acceleration amplitudes of 0.35g and 0.38g. The results showed that liquefaction conditions had not yet occurred in cyclic load applications with an acceleration amplitude of 0.35g and a time duration of 7s. At an acceleration amplitude of 0.38g with a time duration of 60 s, the sand model underwent liquefaction at 7s after the test began. Analysis of the results of transducer records installed at a distance of 0.10 m from the surface of the test model shows that the addition of pumice by 10%, 30%, and 50% can reduce pore pressures by 15%, 62%, and 85%, respectively.

Seismic response prediction and variable importance analysis of extended pile-shaft-supported bridges against lateral spreading: Exploring optimized machine learning models

Reliable prediction of seismic responses of bridges against lateral spreading is critical for fragility and resilience assessment of transportation infrastructure. This problem, however, has remained a significant challenge due to the high complexity of the liquefaction phenomenon and its significance for the seismic performance of structures. The present study explores machine learning (ML) approaches, particularly for bridges supported by extended pile-shafts, for reliable estimation of bearing deformation and column drift ratio responses of bridges. The study considers a large set of covariates across soil, structural, and ground motion features. Five ML algorithms are examined including the traditional multiple linear regression (MLR) as the baseline reference, as well as Lasso regression, neural network (NN), random forests (RF), and gradient tree boosting (GTB). A large number of nonlinear soil-bridge finite element models considering the soil and structural uncertainties are dynamically analyzed under 720 ground motions, and the optimal parameters of the ML models are determined via five-fold cross validation. The results indicate that NN and GTB can well predict the seismic responses of the studied soil-bridge systems, followed by RF, while Lasso and MLR are generally not able to yield reliable estimates. Furthermore, a variable importance analysis is conducted using the produced regression models. Results indicate that intensity measures (IMs) (particularly the spectral acceleration at 2.0 s) are generally more significant than the soil- and structure-related variables. In addition to the IMs, variables associated with the nonliquefiable crust layer (i.e., thickness, strength, and sloping angle) and the concrete strength and longitudinal reinforcement ratio are generally significant variables, whereas the column diameter and rebar yielding strength are relatively insignificant.

Feasibility study for in-situ dynamic testing of structures and geotechnical systems

An evaluation of alternative techniques of in-situ dynamic testing for the calibration of fragility functions and finite element models of existing structures and geotechnical systems subjected to seismic ground motions is discussed in this paper. The cases of excitation of bridge structures, buildings and soils are considered, remembering that also effects on components, non-structural elements and dams can be studied. The advantage of these techniques is to perform in-situ tests on full scale systems in their real conditions and state of maintenance imposing ground motions or effective dynamic excitations, even at low frequencies. A dynamic testing system consisting of a totally independent mobile laboratory has been specifically designed and constructed. Peculiar requirements are necessary to achieve the test set-up, including the development of specific methods to build the reaction system and to prepare the base of the buildings. Finally, a feasibility study to evaluate the capability of the proposed dynamic testing system to study the phenomenon of liquefaction in-situ has been carried out by means of three-dimensional coupled dynamic analysis based on the effective stress approach.

Investigation of coseismic liquefaction‐induced ground deformation associated with the 2019 Mw 5.8 Mirpur, Pakistan, earthquake using near‐surface electrical resistivity tomography and geological data

ABSTRACTAn electrical resistivity tomography survey was conducted to assess the subsurface conditions associated with the coseismic liquefaction phenomenon in the epicentral region following the Mw 5.8 Mirpur earthquake (Pakistan) on 24 September 2019. The Mirpur earthquake produced extensive coseismic liquefaction‐induced surface deformations, including: sand blows, ground failure and lateral spreading along the Upper Jhelum Canal and in the nearby villages. Electrical resistivity data were acquired along three profiles and calibrated with available borehole data. The inverted electrical resistivity tomography profiles reveal three regional geoelectric layers, which consist of an upper 2–‐5‐m‐thick discontinuous zones of medium resistivity values ranging from 25 Ωm to 60 Ωm, underlain by a 7–8‐m‐thick zone of low resistivity (<10 Ωm) and a basal layer of high resistivity (> 100 Ωm). Based on geological and geophysical data, we infer that. (1) disrupted geoelectric layers in the shallow subsurface and spatially extended low electrical resistivity (<8 Ωm) layers document the elevated groundwater table due to sudden increase in pore‐water pressure triggered by the Mirpur earthquake. These lenses of high conductivity may represent potential hazards in the case of future earthquakes in the study area. (2) Fracture azimuths vary between 120° ± 15° and 335°–45° (subparallel and orthogonal to the strike of the Himalayan Frontal Thrust. (3) Common coseismic deformational features (e.g., sand blow and ground fracture) are located within the zone of maximum‐recorded ground shaking (intensity of VI) and underlain by Quaternary alluvial sediments. (4) Mega fractures (1.60 m wide and up to 187 m long) oriented parallel to the canal resulted from lateral spreading. We conclude that high resistivity structures extending from depth to the shallow subsurface resulted from either intrusion of air or eruption of sands from layer three. We suggest that high‐resolution geoelectrical imaging is a valuable complementary tool for evaluating the extent of subsurface liquefaction features and in understanding coseismic deformation during earthquakes, which can help with seismic hazard analysis and mitigation in seismically active regions.

Key factors influencing earthquake-induced liquefaction and their direct and mediation effects

Many factors impact earthquake-induced liquefaction, and there are complex interactions between them. Therefore, rationally identifying the key factors and clarifying their direct and indirect effects on liquefaction help to reduce the complexity of the predictive model and improve its predictive performance. This information can also help researchers understand the liquefaction phenomenon more clearly. In this paper, based on a shear wave velocity (Vs) database, 12 key factors are quantitatively identified using a correlation analysis and the maximum information coefficient (MIC) method. Subsequently, the regression method combined with the MIC method is used to construct a multiple causal path model without any assumptions based on the key factors for clarifying their direct and mediation effects on liquefaction. The results show that earthquake parameters produce more important influences on the occurrence of liquefaction than soil properties and site conditions, whereas deposit type, soil type, and deposit age produce relatively small impacts on liquefaction. In the multiple causal path model, the influence path of each factor on liquefaction becomes very clear. Among the key factors, in addition to the duration of the earthquake and Vs, other factors possess multiple mediation paths that affect liquefaction; the thickness of the critical layer and thickness of the unsaturated zone between the groundwater table and capping layer are two indirect-only mediators, and the fines content and thickness of the impermeable capping layer induce suppressive effects on liquefaction. In addition, the constructed causal model can provide a logistic regression model and a structure of the Bayesian network for predicting liquefaction. Five-fold cross-validation is used to compare and verify their predictive performances.

Hypoplastic modeling of anisotropic sand behavior accounting for fabric evolution under monotonic and cyclic loading

A unified hypoplastic model is formulated by incorporating the anisotropic critical state theory to describe the fabric effect in sand under both monotonic and cyclic loading conditions. An evolving deviatoric fabric tensor that characterizes the internal microstructure of sand is introduced into the hypoplastic model in conjunction with the intergranular strain concept. A scalar-valued fabric anisotropic variable indicating the interplay between the fabric and the loading direction is employed to account for the impact of fabric anisotropy on both the dilatancy and shear strength of sand. The model is demonstrated to be capable of simulating the anisotropic behavior of sand, using a single set of parameters under both monotonic and cyclic loading conditions, as evidenced by the satisfactory match with experimental results from various sources. In particular, by considering the influence of fabric evolution on the dilatancy of sand, the model adequately accounts for the fabric change effect and accurately captures the deviatoric strain accumulation, cyclic mobility, and the flow liquefaction phenomenon under cyclic loading condition.

Numerical modeling of liquefaction in deep saturated sands

The seismic hazard is relatively higher in Northern India due to the presence of the Himalayas encompassing many regional features like Main Boundary Thrust (MBT), Main Central Thrust (MCT) and Himalayan Frontal Thrust (HFT). Implicitly, estimation of liquefaction potential becomes of paramount interest due to the presence of deep soils in this region. Indo-Gangetic basin is composed of thick alluvium deposits where thickness of sand layer may extend up to 30 to 40 m. In the present study, a fully coupled finite element analysis is incorporated for modeling liquefaction phenomena for soil domain up to 30 m depth subjected to cyclic ground excitation of 0.2 g ground acceleration. Moreover, a parametric study is carried out to explore the liquefaction behavior on saturated sand layer of variable thickness. The ratio (Hliq/Hsand) is increasing with depth (0.5, 0.8, 0.833) highlighting the effect of drainage path.

Numerical simulation of liquefaction phenomenon considering infinite boundary

The response of liquefaction behaviour can be analyzed by incorporating the effects of the transient flow of the pore-fluid through the voids, which requires a two-phase continuum formulation for saturated porous media named ‘mixture theory’. The saturated soil system is modelled as a two-phase material based on the Biot's theory for porous media. Infinite elements have been incorporated in the solution algorithms to simulate infinite boundary. A computer code is developed in FORTRAN 90 considering fully coupled dynamic analysis to determine the responses of pore fluid and soil skeleton of an unbounded saturated sandy layer. The unconditionally stable generalized Newmark-Beta method is employed in the solution algorithm for evaluation of response at each time step. A generalized non-associative plasticity-bounding surface model Pastor–Zienkiewicz Mark III is considered to describe the inelastic behaviour of soils under earthquake loading. A parametric study is conducted to consider the effect of the material nonlinearity of the soil grain on liquefaction behaviour. A significant reduction in displacement and excess pore pressure is observed while considering unbounded domain. The salient feature of the solution algorithm is simulation of build up pore pressure and consequent reduction in mean effective stress. It was also observed that key parameters like permeability, earthquake intensity and shear modulus had significant effect on liquefaction response.

ОТРАЖЕНИЕ ПАЛЕОСЕЙСМИЧЕСКИХ СОБЫТИЙ В ПОЗДНЕПЛЕЙСТОЦЕН-ГОЛОЦЕНОВЫХ ОТЛОЖЕНИЯХ ТЕРРАС ОЗЕРА ИМАНДРА (КОЛЬСКИЙ РЕГИОН)

Soft-sediment deformation structures have been indentified in glaciolacustrine deposits of the terrace complexes of the Lake Imandra (Kola Region, NE of the Fennoscandian Shield). According to the paleoseismological criteria, we found that these deformation structures were induced by strong earthquakes. These earthquakes led to the occurrence of secondary deformations of various morphology and sizes in the sandy-sandy sediments, forming a single complex consisting of intensely deformed and destructed deposits and associated clastic dikes and cracks. Among the plastic deformations, the phenomena of liquefaction, boudinage structures, flame structures, irregular convolute stratifications, diapir-like structures and synsedimentary folds are developed. Among brittle deformations, cracks and micro-fractures and dykes, predominate. The spatial and stratigraphic distributions of soft-sediment deformation structures were used to infer about the activation of faults during the Late Glacial and Postglacial period of the sub-latitudinal and north-western strike directions that limit the different-scale blocks of the earth’s crust. According to radiocarbon analysis data and paleogeographic reconstructions, the formation of soft-sediment deformations took place at the end of the Young Dryas – the beginning of the Preboreal period between 12900–11500 cal yr BP, and later, in the Preboreal period – beginning of the Boreal period between 11500– 9900 cal yr BP. It was this period that was accompanied by increased seismic activity not only in the Kola region, but also in the whole of Fennoscandia.

The development of smoothed particle hydrodynamics (SPH) method for modeling the interaction movement of fluid layers in between two soil layers in flat surface condition

The liquefaction phenomenon most often happens in saturated, loose, and low density such as sandy soils. When the bearing capacity drops, loose sand tends to become compressed and behaves like a liquid. This behavior generates an interaction between sandy soils and clay soils which has a higher permeability and include its water content. Therefore, it required a method that can model large deformation movements, namely the free particle method, Smoothed Particle Hydrodynamics (SPH). The SPH Method is used to determine the layer of water formed during the cyclic load to approach the liquefaction phenomenon. The model use clay soils as solid and water layers as fluid with model geometry 0.1x0.1x0.05 m. Program parameters represent clay soils with stiffness coefficient, solid volume, and critical shear strength also fluid layers with damping coefficient, fluid volume, and viscosity. The calculation is done with Fortran Program and visualized in 2 Dimension and 3 Dimension with Gnuplot. Both will be evaluated from the movement of solid and fluid also numeric stability. In the final model the parameters Ks = 20000 N/m, Ks = 53.3 Ns/m, dan x particle = 50 reach numeric stability and all fluid particles can recognize the solid layer.

Understanding of subsurface conditions controlling flow liquefaction occurrence during the 2018 Palu earthquake based on resistivity profiles

The 7.4 Mw earthquake on 28th September 2018 in Palu City triggered a flow liquefaction phenomenon in the Balaroa and Petobo areas, contributing to significant casualties and building damage. This paper presents the results of a liquefaction study to map subsurface conditions in these areas using the multi-electrode resistivity method with the dipole-dipole configuration. The objective of this study is to understand factors controlling the flow liquefaction phenomenon. Based on the interpretation of 2-D resistivity images, the liquefied soil layers are characterized by lower resistivity values than the non-liquified layers. These contrasts of resistivity values form a gently sloping boundary between the liquefied and non-liquefied soil layers. The resistivity image perpendicular to the flow direction indicates the presence of a subsurface basinal morphology in the Balaroa area, suggesting that a shallow groundwater zone is present within the liquefiable soil layer. Thus, the subsurface topographical condition is the main governing factor of flow liquefaction phenomena during the 2018 Palu earthquake.

Updating the Occurrence of the Soil Liquefaction Phenomenon in Peru

We present the information available on the phenomenon of soil liquefaction in Peru due to the seismic action and its representation in a map of soil liquefaction areas. The map of soil liquefaction areas is drawn to the scale 1: 5'000,000 and presents distinctions between liquefaction and probable liquefaction cases, according to the interpretation of the information available in the literature. All the documentation that presents evidence of the phenomenon of liquefaction, such as the formation of small volcanoes of mud and sand, the violent expulsion of water from the soil, the presence of intense cracking and the differential settlements due to the seismic action, has been detailed in this article.

Shaking-table test on seismic motion compressed characteristics in a liquefied soil

The seismic motion compressed characteristic is a key issue on liquefied soil-structure shaking table model test. A series of shaking table tests were performed to study the seismic motion duration compression characteristics on the dynamic response of liquefied soil. Macroscopic phenomena and dynamic pore water pressure were measured and analyzed. Experimental results showed that the intensity and frequency of seismic motion had a significant influence on the dynamic response of the liquefied soil. Meanwhile, the phenomenon of soil liquefaction and the frequency filtering effects were obvious when inputting longer duration seismic motion. The liquefied soil was more sensitive to the seismic motion, which was compressed according to the predominant frequency of the foundation. In addition, it is suggested that the uncompressed seismic motion was more appropriate on the liquefied soil-structure model in 1g shaking table tests.

Analysis of Nonlinear Dynamic Characteristics in Saturated Soil with Blast Wave Diffusion and Damage to Its Effective Strength

Explosions release energy and generate shock waves. Analysis of how shock waves damage transmission media is crucial in protection engineering. Soil liquefaction due to explosions occurs in a highly nonlinear manner. The time point at which soil receives stress waves has yet to be determined. Therefore, this study analyzed the dynamic reaction and liquefaction phenomenon that protects soil after it has received a shock wave. A numerical analysis model was developed and verified through on-site explosion experiments for measuring ground acceleration and excess water pressure. Finite element analysis was employed to establish a numerical analysis model based on experimental site conditions. The LS-DYNA finite element program was used for numerical simulations. The analysis model had a three-dimensional structure with fluid–solid coupling and consisted of eight-node elements. To analyze the dynamic reaction and liquefaction phenomenon that occurs after soil has received a shock wave, a multimaterial arbitrary Lagrangian–Eulerian calculation model was combined with an element erosion algorithm. Meshes were overlapped to achieve fluid–solid coupling for subsequent analysis. The nonlinear dynamic reaction in soil triggered by shock wave transmission and the liquefaction of the material due to excess water pressure were analyzed. The research results showed that the relative errors between numerical analysis and experimental results were within 10%, verifying that the fluid–solid coupling numerical model developed in this study can effectively be used to analyze the dynamic reactions of materials receiving shock waves. Shock waves from both multisite time-delayed explosions and from continual explosions at a single nearby site lead to soil liquefaction. Compared with single-site explosions, multisite time-delayed explosions more easily trigger liquefaction in saturated sandy soil. Analysis of shock wave transmission characteristics and ground shock effects revealed that at a distance of 600 cm from the explosion center, the shock wave was substantially attenuated. The results of shear strain failure analysis indicated that soil liquefaction had an approximate area of scale distance Z = 30.81–64.89 cm/g1/3 and approximate depth of Z = 17.62 cm/g1/3. The results verify the validity of the numerical model and algorithm developed in this study, which can describe the liquefaction process of saturated soil under explosion loading.