Liquefaction Evaluation Research Articles

Monotonic and cyclic simple shear response of gravel-sand mixtures

Understanding the factors that affect the monotonic and cyclic response of gravelly soils during earthquake events is critical to infrastructure design. In this study a large-size Cyclic Simple Shear (CSS) device was utilized to perform monotonic and cyclic shear tests on mixtures of either subrounded 9 mm Pea Gravel or angular 8 mm Crushed Limestone (CLS8) with subrounded Ottawa C109 sand. Tests were performed in constant volume conditions and shear wave velocity was measured for each specimen. Monotonic and cyclic test results at Dr = 47% show that there is an optimum mixture percentage that results in the greatest shear strength and resistance to liquefaction (40% Sand for Pea Gravel Mixtures and 60% Sand for CLS8 Mixtures). The effects of particle angularity, cyclic stress ratio, and initial vertical stress on monotonic and cyclic response of loose and dense gravel mixtures were investigated and are presented. Comparison of the results from the cyclic simple shear tests with existing liquefaction triggering charts suggests the need for improved charts for gravelly soil liquefaction evaluation.

Estimation model of sandy soil liquefaction based on RES model

In order to evaluate sandy soil liquefaction, Rock Engineering Systems (RES) was utilized to establish the estimation model of sandy soil liquefaction. Aiming at unascertained factors in the analysis of sandy soil liquefaction evaluation, earthquake magnitude, maximum ground acceleration, the value of standard penetration test, specific penetration resistance, relative density, mean particle size, and water table were selected as influencing factors of sandy soil liquefaction. The interaction matrix was utilized to describe the interaction among the factors. Expert semi-quantitative (ESQ) method was employed to code the interaction matrix. The interaction strength and dominance were analyzed by cause and effect diagram. Finally, the estimation model-based RES was proposed, and the results were in line with actual situation well. In addition, the improved estimation model-based RES was also presented and discussed, which was more convenient with the same prediction accuracy rate.

Assessment of the cyclic strain approach for evaluating liquefaction triggering

The cyclic strain approach was proposed in the 1980s as a potential alternative to the stress-based simplified liquefaction evaluation procedure. However, despite its fundamental basis and many positive attributes, it has not been embraced by practice. One reason for this may be the need to perform cyclic laboratory tests on undisturbed/reconstituted samples to develop a relationship among excess pore water pressure, cyclic strain amplitude, and number of applied strain cycles. Herein an alternative implementation of the strain-based procedure is proposed that circumvents this requirement, using a strain-based pore pressure generation model in lieu of laboratory test data. To assess the efficacy of the alternative implementation, several hundred small strain shear wave velocity (Vs) and Standard Penetration Test (SPT) field liquefaction case histories are evaluated. The results are compared with both field observations and with predictions from the stress-based procedures. It was found that the stress-based approach yielded considerably more accurate predictions compared to the cyclic strain approach. One likely reason for this is the strain-based procedure's inherent and potentially fatal limitation of ignoring the decrease in soil stiffness due to excess pore pressure when representing the earthquake loading in terms of shear strain amplitude and number of equivalent cycles.

Momentary liquefaction of porous seabed under vertical seismic action

The evaluation of potential liquefaction is an important part in the design of marine structures and offshore installations. However, the liquefaction phenomenon of porous seabed under the action of strong earthquake is traditionally been ignored. This paper aims to explore the momentary liquefaction mechanism of porous seabed through the newly analytical solutions of seabed response induced by vertical seismic excitation. Based on the boundary conditions at the surface and bottom of the seabed, the induced displacements and pore pressure in the sediment are rigorously derived as a function of seawater depth, seabed parameters and seismic characteristics of bedrock. A criterion of earthquake liquefaction in the seabed is developed, employing the concept of induced excess pore pressure. The representative cohesionless marine soils with different properties are selected in the parametric analysis. The results show that the liquefaction of seabed could be influenced by seawater parameters, seabed parameters and earthquake ground motion parameters. The significant finding is that current understanding that the vertical motion effect on soil liquefaction is negligible may not always hold true.

Depositional environment effects on observed liquefaction performance in silt swamps during the Canterbury earthquake sequence

Stratified silty soils deposited in back-swamp settings are shown through regional CPT-based analyses to have mitigating effects on the manifestation of liquefaction in Christchurch. Liquefaction triggering within these deposits is inadequately captured by simplified liquefaction assessment methodologies. Differing near-surface geology and depositional environments indicated in historical documents explain in part the limitations of current liquefaction evaluation procedures in southwest Christchurch. The historical swamp areas are shown through a regional CPT study to contain stratified silt/sand deposits or thick silt layers. Consideration of depositional environment distinguishes between liquefaction performances that are not able to be differentiated through the CPT-based liquefaction triggering assessment alone. CPT resolution is shown to be insufficient to capture the thin layering at these stratified sites, and the simplified liquefaction assessment methods do not take into account the effects of the stratification on pore water pressure movement within a soil profile. Instead, continuous sampling and careful logging of high-quality samples provide important insights on stratification at these silty soil swamp sites and in discerning differences in stratigraphy resulting from differences in depositional environment.

SPT–CPTU Correlations and Liquefaction Evaluation for the Island and Tunnel Project of the Hong Kong–Zhuhai–Macao Bridge

Considering the importance and complexity of the island and tunnel project for the Hong Kong–Zhuhai–Macao Bridge (HZMB), simple piezocone penetration (CPTU) testing has difficulties evaluating soil mechanics and characteristics accurately. Since geotechnical engineers are more familiar with standard penetration tests (SPT) and related design procedures, there is a necessity for reliable SPT–CPTU correlation so that CPTU data can translate to SPT design. This paper reviews existing correlations in the literature between SPT and CPTU, which depend on grain size, fines content or the soil behavior-type index. Since geologic contexts have not been investigated in the existing correlations, a linear function with zero-intercept SPT–CPTU correlations has been developed for every engineering geological unit layer, and the correlations were applied in liquefaction potential evaluation in cases where there was a lack of SPT data. For verification, this liquefaction evaluation was also carried out using both CPTU and SPT testing, and site-specific qt/N ratios of 0.11, 0.16, 0.30 and 0.41 for different soil categories are presented. The developed SPT–CPTU correlations are in accordance with existing correlations in the literature, and the results also reveal that the developed correlations and the liquefaction evaluations are essential for site investigation and geotechnical design in the HZMB area, especially providing a reference for similar engineering surveys.

Validation and Verification of Semi-Empirical Methods for Evaluating Liquefaction Using Finite Element Method

Liquefaction is a hazardous and temporary phenomenon by which a soil saturated with water loses some or all of its resistance. The undrained conditions and a cyclic load increase the pores water pressure inside the soil and therefore a reduction of the effective stress.Nowadays many semi-empirical methods are used to introduce a proposition to evaluate the liquefaction's potential using the in-situ test results. The objective of this paper is to study their ability to correctly predict the liquefaction potential by modelling our case using finite element methods.The study is based on the data of Cone Penetration Tests experimental results of the Casablanca-Tangier High-Speed Line exactly between PK 116 + 450 and PK 116 + 950 and near of Moulay-Bousselham city. It belongs to the Drader-Soueir basin region which is located in the North-West of Morocco.This region had a specific soil’s formation, the first 50 meters are characterised by the existence of sand layers alternating with layers of clay. These formations are very loose and saturated which suggests the possibility of soil liquefaction.We present and discuss the results of applying the Olsen method [1], the Juang method [2] and the Robertson method [3], in the evaluation of liquefaction susceptibility.Apart from the previous empirical analysis to evaluate the liquefaction potential, numerical modelling is performed in this study.

Evaluation of hydrothermal liquefaction of Chlorella sp. for biocrude production using computer-aided exergy analysis

Evaluation of hydrothermal liquefaction of Chlorella sp. for biocrude production using computer-aided exergy analysis

Development of Ground Freezing System for Undisturbed Sampling of Granular Soils

The ground freezing technique was first invented for the undisturbed sampling of the granular soils. With increasing necessity of liquefaction evaluation under earthquake loading, there has been more research with high‐quality granular samples, with ground freezing techniques in the world. However, there has been little research on the ground freezing techniques since Korea had no records of liquefactions until the Pohang earthquake in 2017. Since more than 10 places were reported with liquefaction phenomena, it is required to assess the liquefaction potential with high‐quality samples of granular soils. Therefore, in order to obtain undisturbed samples of granular soils, a new local ground freezing equipment and an operating system were developed in this study. The applied coolant was liquid nitrogen and circulated through a double tube inserted in the ground. To evaluate the performance of the system, laboratory scale tests were performed with water only and saturated fine sands. In the laboratory evaluation, a frozen soil column of 60 cm diameter was made after 20 hours and the average freezing rate was approximately 12 mm/hr in radial direction. After laboratory evaluation, the freezing system was applied in the field and the performance was evaluated with the 2D electrical resistivity tomography. In the field evaluation, the frozen region was 4 m diameter with 6.5 m depth in a cylindrical shape.

Assessment of liquefaction potential of Guwahati city by probabilistic approaches

This paper presents a probabilistic assessment of the liquefaction potential of Guwahati city, in the northeastern region of India, by using eight probabilistic approaches. Northeastern region of India is one of the six most seismically active regions of the world. The assessment was done for saturated cohesionless deposits. Probabilistic liquefaction assessment is done in terms of probability of liquefaction. According to many researchers, probability of liquefaction is a better index for assessment of liquefaction than factor of safety obtained by the deterministic approach. In this paper, a review of the eight probabilistic approaches has been done and a comparative study of liquefaction potential of soil sites susceptible to liquefaction has been done using the eight SPT-based probabilistic approaches. Most of the approaches are based on logistic regression analysis of field performance data to determine empirical equations for evaluating the probability of liquefaction. Departing from logistic regression approach others have used a Bayesian mapping function that relates reliability index and factor of safety to the probability of liquefaction. Standard penetration test (SPT) N values, engineering properties of the soils and depth of water table were taken from a database of 200 boreholes up to 30 m depth covering an area of 262 km2 in Guwahati city. In the absence of ground motion relation in Guwahati city, a design peak ground acceleration of 0.36 g was used since Guwahati falls in zone V, a high earthquake risk zone, according to the seismic zoning map of India. Liquefaction susceptibility from the methods is presented as maps showing zones of levels of risk of liquefaction. The SPT-based liquefaction evaluation probabilistic procedures have been found to yield significantly different predictions. Comparisons of the methods in the probabilistic approach have shown a difference in the values of probabilities in the same depth. However, on common comparison, the soil layers susceptible to liquefaction in different zones of the city have been identified. To get a further clear picture of soil layers susceptible to liquefaction, one-dimensional equivalent linear ground-response analysis was carried out to determine the peak horizontal ground surface acceleration.

Assessment of earthquake-induced liquefaction hazard in urban areas of Hanoi city using LPI-based method

Assessment of earthquake-induced liquefaction hazard in urban areas of Hanoi city using LPI-based method

Energy-based evaluation of liquefaction of fiber-reinforced sand using cyclic triaxial testing

The present study reviews a series of cyclic triaxial tests to investigate the liquefaction characteristics of Babolsar sand reinforced with randomly distributed fibers using an energy-based approach. The effect of fiber content, fiber length, confining pressure, and relative density were studied. The test results revealed that the addition of fibers increased the number of cycles required to liquefaction, resulting in higher cumulative dissipated energy. This accounted for the higher cyclic shear resistance of reinforced sand compared to unreinforced sand. Capacity energy is defined as cumulative dissipated energy to onset of liquefaction. The test results showed that Wliq was significantly affected by the fiber inclusion. Comparative studies demonstrated that energy-based method is a good way to evaluate liquefaction potential of fiber-reinforced sands.

Liquefaction Prediction Using Rough Set Theory

Evaluation of liquefaction is one of the most important issues in geotechnical engineering. Liquefaction prediction depends on many factors and the relationship between these factors is non-linear and complex. Different methods have been proposed by different authors for liquefaction prediction. These methods are mostly based on statistical approaches and neural network.In this paper a new approach based on Rough Set data mining procedure is presented for liquefaction prediction. The Rough set theory is a mathematical approach for analysis of imperfect knowledge or unclear description of objects. In this approach the decision rules are derived from conditional attributes in Rough Set analysis and the results are compared with actual field observations. The results of this study indicate that using this method can be helpful for liquefaction prediction and can reduce unnecessary costs in site investigation process.

The impact evaluation of soil liquefaction on low-rise building in the Meinong earthquake

This paper presents major preliminary observations on the liquefaction-induced damages in the Meinong earthquake (ML = 6.4). The severe damages to buildings centered on Huian and Sanmin Streets in Tainan City where the places were reclaimed fish or farm ponds with poor construction quality from many decades ago. To better understand the effect due to the soil liquefaction at these sites, the information provided by the in situ 13 Standard Penetration Test boreholes and 5 Cone Penetration Test soundings accompanying with the PGAs derived from the near seismographs was used to conduct the soil liquefaction evaluation by the Seed method (Seed et al. in J Geotech Eng ASCE 111(12):1425–1445, 1985) when subject to the Meinong earthquake. The liquefaction potential index (LPI) was then evaluated accordingly. From the results, it was found that the estimated damage severity was not consistent to the field conditions if the local site effect was not taken into account. To better reflect the site response in such sites, the sites’ PGAs in the PGA contour map were multiplied by 1.5 times to quantify the amplification effects due to the soft geological condition. In addition, the PGAs based on other simple approaches were evaluated as well for comparison. Besides, the effects of fines content and magnitude scaling factor were also discussed in this paper. After that, several common simplified methods were also used to calculate the LPI when subject to the Meinong earthquake in order to evaluate the applicability of these simplified methods.

Predicting potential of controlled blasting-induced liquefaction using neural networks and neuro -fuzzy system

In recent years, controlled blasting has turned into an efficient method for evaluation of soil liquefaction in real scale and evaluation of ground improvement techniques. Predicting blast-induced soil liquefaction by using collected information can be an effective step in the[a1] study of blast-induced liquefaction. In this study, to estimate residual pore pressure ratio, first, multi- layer perceptron neural network is used in which error (RMS) for the network was calculated as 0.105. Next, neuro-fuzzy network, ANFIS was used for modeling. Different ANFIS models are created using Grid partitioning (GP), Subtractive Clustering (SCM), and Fuzzy C-means Clustering (FCM). Minimum error is obtained using by FCM at about 0.081. Finally, radial basis function (RBF) network is used. Error of this method was about 0.06. Accordingly, RBF network has better performance. Variables including fine-content, relative density, effective overburden pressure and SPT value are considered as input components and the Ru, residual[a2] pore pressure ratio was used as the only output component for designing prediction models. In the next stage the network output is compared with the results of a regression analysis. Finally, sensitivity analysis for RBF network is tested, its results reveal that and SPT are the most effective factors in determining Ru.

Optimal intensity measures for probabilistic seismic demand modeling of extended pile-shaft-supported bridges in liquefied and laterally spreading ground

Seismic intensity measures (IMs) perform a pivotal role in probabilistic seismic demand modeling. Many studies investigated appropriate IMs for structures without considering soil liquefaction potential. In particular, optimal IMs for probabilistic seismic demand modeling of bridges in liquefied and laterally spreading ground are not comprehensively studied. In this paper, a coupled-bridge-soil-foundation model is adopted to perform an in-depth investigation of optimal IMs among 26 IMs found in the literature. Uncertainties in structural and geotechnical material properties and geometric parameters of bridges are considered in the model to produce comprehensive scenarios. Metrics such as efficiency, practicality, proficiency, sufficiency and hazard computability are assessed for different demand parameters. Moreover, an information theory based approach is adopted to evaluate the relative sufficiency among the studied IMs. Results indicate the superiority of velocity-related IMs compared to acceleration, displacement and time-related ones. In particular, Housner spectrum intensity (HI), spectral acceleration at 2.0 s (S a-20), peak ground velocity (PGV), cumulative absolute velocity (CAV) and its modified version (CAV 5) are the optimal IMs. Conversely, Arias intensity (I a ) and shaking intensity rate (SIR) which are measures often used in liquefaction evaluation or related structural demand assessment demonstrate very low correlations with the demand parameters. Besides, the geometric parameters do not evidently affect the choice of optimal IMs. In addition, the information theory based sufficiency ranking of IMs shows an identical result to that with the correlation measure based on coefficient of determination (R 2). This means that R 2 can be used to preliminarily assess the relative sufficiency of IMs.

A unified framework for evaluating in situ state of sand with varying fines content

In the design and construction of large-scale earth structures such as hydraulic fills for artificial islands or tailings dams, a major concern is the susceptibility of sand fills to flow failure or liquefaction. The big challenge in liquefaction evaluation is to evaluate the in situ state of sand, because it is extremely difficult to obtain high-quality undisturbed samples for that purpose. Here an attractive framework is presented, which allows a direct evaluation of in situ states of sands with varying quantity of fines through shear wave velocity measurements. The framework is built upon a specifically designed experimental programme comprising small-strain shear wave measurements and large-strain undrained shear tests over a wide range of post-consolidation states. A marked feature of the framework is the unified characterisation of shear wave velocity for both clean and silty sands through a state parameter that properly combines the effects of void ratio and confining stress in a sound theoretical context. As the shear wave velocity can be reliably measured both in the laboratory and in the field, and since the state parameter is a meaningful index for characterising various aspects of sand behaviour, the proposed framework is highly promising in a range of geotechnical applications.

A worldwide SPT-based soil liquefaction triggering analysis utilizing gene expression programming and Bayesian probabilistic method

In this context, two different approaches of soil liquefaction evaluation using a soft computing technique based on the worldwide standard penetration test (SPT) databases have been studied. Gene expression programming (GEP) as a gray-box modeling approach is used to develop different deterministic models in order to evaluate the occurrence of soil liquefaction in terms of liquefaction field performance indicator (LI) and factor of safety (Fs) in logistic regression and classification concepts. The comparative plots illustrate that the classification concept-based models show a better performance than those based on logistic regression. In the probabilistic approach, a calibrated mapping function is developed in the context of Bayes' theorem in order to capture the failure probabilities (PL) in the absence of the knowledge of parameter uncertainty. Consistent results obtained from the proposed probabilistic models, compared to the most well-known models, indicate the robustness of the methodology used in this study. The probability models provide a simple, but also efficient decision-making tool in engineering design to quantitatively assess the liquefaction triggering thresholds.

Liquefaction Resistant of Monterey No. 0/30 Sand in Cyclic Triaxial and Cyclic Hollow Cylinder Tests

Liquefaction is the most detrimental ground failure caused by strong earthquakes. Ground liquefaction leads to associated foundation and superstructure failures due to loss of bearing capacity and excessive deformation and an appropriate assessment of liquefaction is critical to the seismic safety evaluation of foundations and super structures. Cyclic triaxial tests (CTT) are traditionally used in experimental evaluation of liquefaction resistance. However, ground motion propagates from the soil-bedrock interface to ground surface in the form of cyclic simple shear, which can be more ideally simulated in a cyclic hollow cylinder (CHC) test than in a cyclic triaxial test. With appropriate dimensions, the distribution of stresses and strains in CHC sample is more uniform than that of cyclic triaxial test and CHC is an ideal substitute for CTT is evaluation of liquefaction during the earthquake shaking. While CHC is more ideal than CTT for evaluation of liquefaction resistance, CTT is much more prevalent due to its simplicity, and CHC is used to evaluate the reduction factor, Cr as recommended by Seed and Idriss (1979).

Field Evaluation of Soil Liquefaction and Its Confrontation in Fine-Grained Sandy Soils (Case Study: South of Hormozgan Province)

The phenomenon of liquefaction is one of the most important aftermaths of earthquakes. Whereas deposits subject to liquefaction are possible in city regions, during an earthquake and the existence of high-level underground waters, liquefaction is extremely probable. The aim of this research is to identify layers vulnerable to liquefaction and adopt necessary measures in order to prevent probable damages to structures and coastal facilities during earthquakes. This research has carried out case studies on the mechanism of liquefaction and evaluated the issues resulting to it in a number of coastal regions south of Hormozgan province. A sample of the application of this phenomenon in town construction projects in Bandar Abbas and methods to prevent and control them have also been referred to.