Probability Of Liquefaction Research Articles

Liquefaction Potential Assessment for Basrah Soil Based on Standard Penetration Test Values

Most of the crustal depth shocks are situated within the geographic border of the earthquake risk map for Iraq. The number of earthquakes rises, and apattern emerges, with their magnitudes ranging from 2.7 to 7.2. Recently, many parts of Iraq have been affected by earthquakes. Under such loads, soil can be liquefied, which might destroy the ground and buildings. Therefore, bore log data, grain size distribution, N-values of the standard penetration test, and an earthquake risk map are used to assess the liquefaction potential. The liquefaction parameters are calculated using Idriss and Boulanger (2014). It is chosen based on the amount of sand and fines present. Five earthquakes with magnitudes ranging from 5-7 and an interval of 0.5 have been selected. The purpose of this research is to assess the liquefaction potential of some areas in Basrah city that are located on medium to very dense sandy soil. The results indicate a high probability of liquefaction at a shallow depth in some sandy areas, indicating the need for a liquefaction prevention method.

A probabilistic liquefaction reliability evaluation system based on CatBoost-Bayesian considering uncertainty using CPT and Vs measurements

The existing liquefaction evaluation model inevitably contains uncertainty in the establishment process, which will affect the evaluation of the effect of seismic liquefaction. The purpose of this study is to combine cone penetration test and shear wave velocity test (CPT-Vs) to develop a simplified probabilistic framework for liquefaction potential assessment, and to couple the first-order reliability method (FORM) to reduce model and parameter uncertainties. Based on the case histories of CPT-Vs, the framework uses the Bayesian-optimized CatBoost algorithm to develop a limit state function for liquefaction trigger analysis. Within the framework of FORM, this limit state function parameter and model uncertainties are characterized by the mean (μc) and coefficient of variation (COV) of the soil parameters, which are obtained and calibrated by combining site-specific new information with prior knowledge. Moreover, in the absence of parameter uncertainty, a deterministic model is developed which establishes a mapping function between probability of liquefaction to factor of safety. The study results show that the uncertainty of the limit state function model can be characterized by using μc=1.14 and COV=0.30, and the simplified liquefaction probabilistic framework can provide reasonable liquefaction evaluation results.

Probabilistic and deterministic-based approach for liquefaction potential assessment of layered soil

In the present study, deterministic and probabilistic approaches have been used for the assessment of liquefaction potential of ground during an earthquake. The deterministic approach was used to analyze and assess the liquefaction of loose saturated river bed deposit with emphasis on two benchmark locations. A wide range of earthquake data in the form of peak ground acceleration (PGA) values of 0.18 g, 0.37 g, 0.6 g and 0.75 g was used as input motions. The dynamic properties of soil were evaluated using standard penetration test (SPT) data obtained from the bore logs. The shear stress induced within soil deposit due to the seismic excitation was calculated in the form of cyclic stress ratio (CSR) and cyclic resistance ratio (CRR) in order to calculate the factor of safety (FOS) against liquefaction. In addition, liquefaction potential index (LPI) and probability of liquefaction (PL) were also calculated using input motion. It was observed, based on the probability analysis and liquefaction indices, that the shallow layer soil profile is safe against liquefaction, whereas deep layer soil profile is unsafe.

Liquefaction hazard mapping and relationship between probability of liquefaction and factor of safety for Kolkata city, India

Liquefaction hazard mapping and relationship between probability of liquefaction and factor of safety for Kolkata city, India

ASSESSING SEISMIC SOIL LIQUEFACTION POTENTIAL USING MACHINE LEARNING APPROACH

The liquefaction vulnerability of soil is generally related to a few soil parameters which are ordinarily measured by laboratory tests on distributed and undistributed tests under distinctive test conditions. This study uses methods based on a standard penetration test to assess liquefaction criteria to appraise the liquefaction vulnerability for soil deposits of Chalus City placed in a high seismic area. To overcome the deficiencies of these experimental strategies an ANN-based model has been created utilizing the Artificial Intelligence technique to anticipate liquefaction. The proposed model is a function of the plasticity index, liquid limit, water content, and some other geotechnical parameters. Reliability index (β) and probability of liquefaction (PL) have also been determined for both the proposed methods for a superior understanding of their accuracies and strength. First-order second moment (FOSM) reliability analysis has been embraced in the present paper. The observation drawn from the study illustrates a reliable and conventional expectation rate of the regression as compared to the experimental strategy. A strong regression shown for assessing the liquefaction vulnerability, which is based on field test information for preparatory prediction, would be of extraordinary help within the field of geotechnical designing.

Numerical modeling of seismic wave propagation in loosely deposited partially saturated sands: an application to a mine dump monitoring case

Extensive mine dumps consisting of loosely deposited sands have been created as a result of open-pit lignite mining, with a risk of soil liquefaction under high water saturation and a corresponding initiating event. Soil compaction is one of the feasible methods for reducing the probability of liquefaction. For the monitoring of liquefaction events and the evaluation of compaction work, seismic survey methods with sensitivity to changes in soil saturation and structure may thus complement other methods. Compared to exploration methods for deep systems, the shallow subsurface presents some unique challenges. To this end, an open-source, customizable code based on Biot’s theory was developed in the FEniCS library, which takes into account partial saturation and porosity dependence of stiffness, permeability, and other quantities. Following code verification, a comprehensive investigation of parameter studies is conducted, from which the effects of different factors on wave propagation characteristics were obtained. The numerical model was applied to simulate the expected changes in seismic response following soil compaction. Furthermore, the position of the high saturation area could be detected from the reflection and refraction P waves. The goal of this work is to provide an analysis framework for the assessment of compaction works and monitoring liquefiable soils in mine dumps under conditions of variable saturation due to rising groundwater tables.

Validity of Juang's Method to Predict the Liquefaction Potential of the Soils of Sablette Algiers

This work presents a deterministic and probabilistic analysis of the liquefaction potential of soils. Soil liquefaction is a process leading to the total loss of shear strength of loose sands under seismic stresses by increasing pore pressure. It is accompanied by deformations. Certain factors related to the characteristics of the ground and the seismic excitation can significantly influence the appearance or not of the phenomenon. Empirical methods of liquefaction potential assessment are widely used. The probabilistic method has been widely used for estimating the probability of liquefaction. Initially, the uncertain parameters are modeled by normal random variables. A parametric study of the coefficients of variation of the random variables showed that the number of strokes (N1)60 of the SPT test is the parameter that has the greatest influence on the probability of liquefaction. This study focuses on the liquefaction potential by methods based on the results of the in-situ "Standard Penetration Test" Through the results obtained in this study of the site of Sablettes in Algiers, in general, there is a risk of liquefaction of the soil in the sandy layers, and we can say that the site studied has an average liquefaction potential. According to the classification of liquefaction potential proposed by Juang et al., (2012).

A latent Gaussian process model for the spatial distribution of liquefaction manifestation

This paper presents a model for distributing zones of liquefaction and nonliquefaction for use in regional liquefaction risk analysis. There are two broad methodologies that have been used to evaluate liquefaction risk on the regional scale: (a) application of site-specific procedures using soil properties inferred from geology, or (b) application of geospatial proxies for liquefaction. The first approach will tend to predict similar liquefaction probabilities across broad areas with similar geology, water table depths, and shaking intensities. The second approach yields the probability of liquefaction, which can be interpreted as the portion of the area affected by liquefaction ([Formula: see text]). Neither approach, however, gives an informed prediction of the spatial distribution of liquefaction and the resulting displacements, which are particularly important for assessments of seismic risk for spatially distributed infrastructure systems. We propose a methodology for incorporating spatial correlation into a geospatial proxy for liquefaction to create maps of liquefaction and nonliquefaction for a given earthquake scenario. First, we describe a latent Gaussian process that is assumed to govern the spatial distribution of liquefaction. Next, a database of empirical observations of liquefaction is used to obtain the coefficients that describe that latent Gaussian process. The proposed model yields random realizations of maps of liquefaction and nonliquefaction conditioned on a map of [Formula: see text]. Such maps can be used to constrain the area over which displacements are estimated using soil properties inferred from geology and are therefore a critical component in reducing bias in assessments of liquefaction risk at the regional scale.

On the In Situ Cyclic Resistance of Natural Sand and Silt Deposits

This study presents cyclic resistances of an instrumented medium dense sand (i.e., the Sand Array) and medium plastic silt (i.e., the Silt Array) deposit deduced from in situ dynamic testing using the controlled blasting test method. Particle velocity records were used to calculate the cyclic resistance ratios, CRRs, and convert the transient blast-induced ground motions into their equivalent number of shear stress cycles, Neq, through consideration of the cyclic resistance observed from stress-controlled, constant–volume, cyclic direct simple shear (DSS) tests. The CRR-Neq relationship developed for the medium dense sand deposit demonstrated that the in situ cyclic resistance is larger than that (1) expected from cyclic DSS test specimens reconstituted to the in situ vertical effective stress, relative density, and shear wave velocity, Vs; and (2) calculated using case history-based, penetration-, and Vs-based deterministic formulations of liquefaction triggering models. Differences between the in situ cyclic resistance and that computed using probabilistic liquefaction triggering models reduced somewhat when considering probabilities of liquefaction exceeding 50% and 85%, depending on the model. Partial drainage during dynamic loading of the Sand Array appears to have contributed to the cyclic resistance of the sand deposit, with an increase of 6% to 27% compared to that estimated for fully undrained conditions. Differences between the cyclic failure criteria used to interpret the cyclic resistance of intact laboratory specimens of silt result in significantly different interpretations of the in situ CRR; the use of maximum excess pore pressure-consistent criteria appears to provide the best representation of the in situ, stress-based cyclic resistance when high quality, intact silt specimens form the basis for conversion of transient seismic waveforms to uniform shear stress loading cycles. The investigation described herein suggests that the reduction of cyclic resistance for plastic soils to account for multidirectional shaking ranges from 0% to 7% over Neq of 1 to 100.

Study on Classification Method of Soil Liquefaction Potential Based on Decision Tree

A new method for evaluating the liquefaction probability of saturated soils is presented in this paper. The existing methods are mainly expressed in equation form, and the evaluation process is always complex. Therefore, to address these shortcomings, a new method based on a tabular form is constructed using a hybrid approach combining the logistic equation and decision trees (classification and regression tree and chi-squared automatic interaction detector) based on the shear wave velocity test databases. The effectiveness of the new method was verified by comparing the predicted liquefaction results with actual liquefaction results. The new method improved the accuracy of the liquefaction evaluation method based on shear wave velocity; the classification was correct for more than 75% of the samples. In addition, the importance of the liquefaction factors was considered during the method construction, which ultimately simplified the evaluation process while ensuring accuracy.

Spatial distribution characteristics of soil liquefaction potential in the Yellow River Subaquatic Delta, China

This paper aims to provide a design basis for engineering disaster prevention and mitigation by accurately describing the spatial distribution of soil liquefaction. A group of in-situ Cone Penetration Tests (CPT) was conducted to evaluate the seabed soil properties and liquefaction potential of the Yellow River Subaquatic Delta. The factor of safety against liquefaction (FSL) and liquefaction potential index (LPI) were utilized to investigate the liquefaction characteristics of seabed soils. The findings are as follows: (1) The delta is "near coarse and far fine," with sand and silt dominating the onshore direction and silt and silty clay dominating the offshore direction; (2) Silt, as a structured soil, has a maximum sensitivity of 10, and there are local liquefaction phenomena. The size of a Soil behavior type index can be used as the limit value of liquefaction discrimination in the region; (3) The FSL of the shallow layer is smaller, while that of the deep layer is generally larger. The FSL near the coast is smaller than that far from the coast, but its variation range is large, indicating that the shallow soil layer near the coast is more prone to liquefaction; (4) The LPI of the delta is less than 5, which is significantly affected by the wave cycle loads and geographical environment. Liquefaction can occur, but the probability of large-scale liquefaction is low.

Analysis of the Effect of Pore Water Pressure on a Small Radius Curve Section of a Fine Sand Layer under Cyclic Metro

Small curved metro shield tunnels located in fine sand layers are sensitive to the response of horizontal and vertical cyclic loads from train operations, especially for centrifugal horizontal loads. The majority of Zhengzhou’s strata are dominated by this geological composition. Therefore, the dynamic response of the fine sand layer under the train vibration load will lead to the settlement of the sand layer, which brings great hidden danger to the train operation. Long-term pore water monitoring was carried out in this paper, and the use of MIDAS-GTS (Multi-candidate Iterative Design with Adaptive Selection) finite element calculation platform to establish the metro ballast-lining-soil coupling dynamic model for mutual verification. The variation patterns of pore water pressure and super pore water pressure during train operation and the vibration response pattern of the soil layer around the tunnel were investigated. The results suggest that: (1) The pore and excess pore water pressures generated at the start of vibration are not easily dissipated and transferred, making them larger in the early stages of train operation. In contrast, the fine-grained powdered sandy soil has a small amount of clay particles, giving strength and cohesion to the soil layer. Vibrating hole pressure and excess pore water pressure stabilize with the train at a later stage; (2) The low probability of liquefaction in the silt layer surrounding the tunnel; (3) Under vibrating loads, areas of significant soil settlement are concentrated on the soil surface, on the upper side of the tunnel in the silty sand layer and at the bottom 3 m of the tunnel, however, its low variation in settlement has a low impact on the tunnel.

Probabilistic of in Situ Seismic Soil Liquefaction Potential Based on CPT-Data in Central Jakarta, Indonesia

Jakarta City located at the northern part of Java Island has a potential liquefaction since there are many soil layers as a qualified as liquefaction susceptible, such as: silty sand and sand. The effects of liquefaction occurrence on saturated silty sand and sand during earthquakes can have potential to damage structure. A case history using CPT-data randomly taken from Central Jakarta region was compiled and back analyzed to investigated probability of liquefaction. The present study focuses on the probabilistic evaluation of liquefaction potential of this region, considering silty sand and sand layers related to CPT soundings. Silty sand was found as a thin layer or a lens between silty clay, silt and clay which was classified as a soft soil layer, and the sand layer is mostly found as a hard bottom layer. Normalization of tip CPT resistance (qc) corrected by an effective overburden stress was not only used to thick layer of silty sand and sand, but also it was applied to determine liquefaction potential existed as the “thin” layers. The silty sand and sand layers have a probability of liquefaction (PL) between 5 to 50% for magnitudes and distances of 500 years with PGA less than 0.42 gal.

Event-based probabilistic liquefaction hazard analysis for defining soil acceptance criteria

In professional practice liquefaction susceptibility has been assessed through different methods, frequently aimed at establishing a safety factor against liquefaction, or its occurrence probability, for an earthquake with known magnitude and location, along with a well-characterized soil profile. These conventional analyses allow estimating the liquefaction probability for only one event, such as the Maximum Credible Earthquake (MCE), or the life safety limit state associated with a fixed return period. Therefore, it is not possible to estimate the occurrence frequency of liquefaction because there is only a vague link between the design earthquake and its occurrence frequency and because, in most cases, there are many earthquakes, besides the design earthquake, which could contribute to liquefaction with a non-negligible probability. This paper shows an update of the Probabilistic Liquefaction Hazard Analysis (PLHA) that has been used in the past, reframing it into a contemporary context, mainly taken from Probabilistic Seismic Hazard Analysis (PSHA), indicating how a rigorous PLHA can be performed to determine how frequently liquefaction will occur and how that procedure can be easily integrated into a modern PSHA code, namely R-CRISIS. The probability of liquefaction needs the estimation of earthquake acceleration levels at the surface of the soil profile and, therefore, this paper presents a comprehensive approach to consider the nonlinear behavior of the soil in the estimation of amplification factors. Besides this, we propose a soil-characteristics acceptance criterion, coherent with those typically used in other earthquake engineering areas. Finally, the paper proposes some approximations that, under certain conditions, allow having reasonable estimations of the annual frequencies of liquefaction occurrence in a soil profile, without performing a complete PLHA.

Site Characterization and Liquefaction Hazard Assessment for the Erenler Settlement Area (Sakarya Province, Turkey) Based on Integrated SPT-Vs Data

The focus of this study is to examine the soil properties and liquefaction potential of the Erenler center district in a critical tectonic zone that can produce large earthquakes, such as the North Anatolian Fault Zone (NAFZ). In this sense, 40 surface wave measurements and 52 geotechnical drillings were employed. Accordingly, the liquefaction potential index (LPI), liquefaction severity index (LSI), Ishihara boundary (IB) curve, and Ishihara-inspired index (LPIISH) liquefaction approaches from geotechnical and geophysical methods were used as integrated. All liquefaction analyses were examined for two scenarios, Mw: 7.4 1999 Izmit (amax: 0.41 g) and Mw: 7.0 1967 (amax: 0.28 g) Mudurnu. According to the analyses, almost all of the study area showed liquefaction risk in the Izmit scenario. In the Mudurnu scenario, liquefaction risk distribution decreased parallel to acceleration. The LPI, LPIISH, and IB liquefaction risk results for both scenarios support each other. On the other hand, it was determined that the probability of liquefaction was lower in the LSI evaluation. The spatial distribution of the liquefaction potential of the Vs-based and SPT-based LPI assessments had a similar pattern. These results show that the LPI approach, originally SPT-based, can also be calculated based on Vs. In addition, according to Vs30-based (average shear wave velocity at 30 m depth) soil classification criteria, low-velocity character E and D soil groups dominate the Quaternary alluvial basin. This indicates that deformation-induced failures may occur even in areas with a low probability of liquefaction in similar strong ground motions. In addition, the evaluation of liquefaction with many approaches in two different bases within the scope of the study constitutes a novelty for the study area and liquefaction analyses. While performing diversified liquefaction analyses and approaches will contribute to obtaining more reliable soil liquefaction results, more case studies are needed to elucidate these comparisons.

Probabilistic Soil Liquefaction Assessment: A Case Study for Agartala City in Tripura in North-East India

A sudden increase in pore water pressure causes the effective stress to decrease significantly, which in turn causes a loss of shear strength and the subsequent outcome of allowing the soil to behave as a liquid, resulting in soil liquefaction. Agartala, the capital of Tripura, is located in northeastern India, and the entire region is considered seismically active according to the seismic zoning map of India as per IS 1893:2002 (Part 1); the entire region is classified as Zone-V. Significant earthquakes have struck this region, including the 1897 Shillong and 1950 Assam earthquakes. The city is vulnerable to liquefaction due to alluvial soil and a low groundwater table. Several parameters are involved in assessing liquefaction potential in the deterministic method and have different input parameter uncertainties, resulting in inconsistent outcomes. As a result, evaluating liquefaction susceptibility requires a thorough probability approach that considers parameter uncertainty. In this work, the soil liquefaction potential of Agartala City is assessed using fuzzy logic and compared to the conventional Reliability technique using the first-order second-moment method. Soil liquefaction potential was properly calculated using both approaches for the 71 boreholes in and around Agartala city. The outcomes are shown as contour maps representing spatial variations of the probability of liquefaction at different depths. In this study, Fuzzy logic is used to model the relationships between different soil parameters, which can help better understand the soil\'s behaviour during liquefaction. This developed method can assess the vulnerability of liquefaction potential and select appropriate materials and construction processes.

Probability Liquefaction On Silty Sand Layer On Central Jakarta

Indonesia has a strong earthquake risk. The effects of saturated silty sand liquefaction during earthquakes can be very damaging. Liquefaction is the threats to the safety of structures, and the evaluation of liquefaction potential is essential in locations with silty sand layers. Research was performed at BPJS Branch Office building project in CentralJakarta with 7 floors when conducted the substructure or deep foundation design. This research uses cone penetration test (CPT) data to evaluate the potential and probability of liquefaction. At the same time, this research also predicts the bearing capacity (Qu) of single pile embedded on silty sand layer at conditions of Non-Liquefaction (NL) and Liquefaction (L) due to an earthquake. The research results showed that silty sand layers were classified as the susceptible layers to the liquefaction potential after plotted of CPT data into the graphic from Robertson & Campanella method [1] and signed by zone A. However, bearing capacity (Qu) when condition of NL and L was only different around 10 to 11%, it can be considered that the single pile remains stable during occurrence the liquefaction and capable to support the upper structure system. This assumption is also strengthened by the analysis result of probability liquefaction (P[L]) for sand and silty sand layers, the average of (P[L]) based on the maximum earthquake acceleration (PGA) T = 50 years exists in the range < 5 % to 10 % and it can be stated that [P(L)] is very low to low [2] and it can be concluded that the sand and or silty sand layers at study area is hard to category as a liquefiable layer.

Evaluation of a geospatial liquefaction model using land damage data from the 2016 Kaikōura earthquake

The paper uses two geospatial liquefaction models based on (1) global and (2) New Zealand specific variables such as Vs30, precipitation and water table depth to estimate liquefaction probability and spatial extent for the 2016 Kaikōura earthquake. Results are compared to observational data, indicating that the model based on global variables underestimates liquefaction manifestation in the Blenheim area due to the low resolution of the input datasets. Furthermore, a tendency for underprediction is evident in both models for sites located in areas with rapidly changing elevation (mountainous terrain), which is likely caused by the low resolution of the elevation-dependent variables Vs30 and water table depth leading to incorrect estimates. The New Zealand specific model appears to be less sensitive to this effect as the variables provide a higher resolution and a better representation of region specific characteristics. However, the results suggest that the modification might lead to an overestimation of liquefaction manifestation along rivers (e. g. Kaikōura). An adjustment of the model coefficients and / or the integration of other resources such as geotechnical methods can be considered to improve the model performance. The evaluation of the geospatial liquefaction models demonstrates the importance of high resolution input data and leads to the conclusion that the New Zealand specific model should be preferred over the original model due to better prediction performance. The findings provide an overall better understanding on the models’ applicability and potential as a tool to predict liquefaction manifestation for future hazard assessments.

Experimental study of soil responses around a pipeline in a sandy seabed under wave-current load

Wave and current coexist widely in the oceans. Ever-changing wave characteristics, such as height and length, have a significant influence on the dynamic response within the seabed soil due to the presence of currents. Some aspects of wave, seabed and pipeline interactions have been widely investigated over past years, incorporating both experimental and numerical approaches. However, previous studies on seabed dynamic response around pipelines have mainly focused on cases with wave loading. In this experimental laboratory study, the current loading and diverse backfill conditions which commonly occur far offshore are discussed in depth. It is found that when subjected to the combined wave and current loads, the response of the seabed around a pipeline is more complex than that subjected to pure wave loading as current velocity and propagation direction would significantly change the wave characteristics as well as seabed response. Most notably when comparing with the pure wave loading, the pore pressure amplitude and its attenuation rate within the seabed increases when current and wave travel in the same direction. This could increase the possibility of liquefaction around the pipeline. When current travels in opposing direction to the wave, the effect of current on the decrease of pore pressure and its attenuation rate is more significant than that of the co-current actions. This means that the counter-current will reduce the probability of soil liquefaction.

Developing region-specific fragility function for predicting probability of liquefaction induced ground failure

The liquefaction potential index (LPI) has been widely used to develop fragility function for predicting the liquefaction-induced ground failure. As the fragility function tends to vary from one region to another, it is best developed based on region-specific data. When the amount of region-specific data is limited, how to develop the region-specific fragility curve is a challenging problem. In this study, a Hierarchical Bayesian Model (HBM) is suggested for developing region-specific fragility functions based on LPI, which can systematically consider the effects of the amount and characteristics of the local data as well as the data from other regions. The suggested method is illustrated with an example. It is shown that the HBM outperforms the lumped parameter model (LPM) which does not consider the inter-region variability of the fragility curves. When the amount of region-specific data is large, the fragility function developed based on the HBM is very close to that developed based on the independent parameter model (IPM), which constructs a region-specific fragility function utilizing only the region-specific data. When the region-specific data is not enough, the HBM also outperforms the IPM through borrowing information from other regions.