Liquefaction Risk Research Articles

Spatial evaluation of liquefaction potential in Christchurch following the 2010/2011 Canterbury earthquakes

Widespread damage as a result of liquefaction was observed in the Canterbury region following the 2010 Darfield earthquake and the 2011 Christchurch earthquake. To quantify the liquefaction risk in some areas associated with these two events, strong motion records and available boring data were used to produce maps showing distributions of liquefaction potential indices (LPI). It was found that for both events, the distributions of LPI values agree reasonably well with the observed severity of damage. The increased peak accelerations during the February 2011 event along with the elevated water table resulted in more severe damage in eastern Christchurch than during the 2010 earthquake, while the lower shaking intensity in the Waimakariri region led to a severe but more localized liquefaction. In cases where the calculated LPI and observed damage did not agree, the occurrence of lateral spreading and the thickness of the surface crust appear to be the main reasons. Finally, through analysis of boring data, the role of the surface crust in liquefaction manifestation was analyzed.

Influence of Assumed Groundwater Depth on Mapping Liquefaction Potential

Groundwater depth is a critical parameter in assessing regional liquefaction potential. Uncertainties associated with groundwater depth are usually pervasive because of natural variability and spatial separation between data points. These uncertainties often lead to erroneous or doubtful assessments of liquefaction potential. In an attempt to provide more credible estimates of liquefaction potential across a sizable urban area, this study sought to estimate the threshold groundwater depths that could be expected to trigger liquefaction in the St. Louis, MO, metro area, which was damaged by the 1811–1812 New Madrid earthquakes. We used liquefaction potential indexes (LPIs) > 5 and > 15 as the thresholds for moderate and severe liquefaction risks, respectively. The threshold groundwater depth for triggering liquefaction was evaluated using standard penetration test data and a scenario involving an M7.5 earthquake with a peak ground acceleration of 0.20 g. The threshold groundwater depths then were geostatistically contoured and compared with accepted groundwater level scenarios to map the corresponding liquefaction risk. This study revealed that Holocene alluvium in East St. Louis generally exhibits deeper threshold groundwater depths than do the mean groundwater levels and appears to be more prone to liquefaction.

Assessment of Liquefaction Potential of Guwahati City: A Case Study

The liquefaction potential of saturated cohesionless deposits in Guwahati city, Assam, was evaluated. The critical cyclic stress ratio required to cause liquefaction and the cyclic stress ratio induced by an earthquake were obtained using the simplified empirical method developed by Seed and Idriss (J soil Mech Found Eng ASCE 97(SM9):1249–1273, 1971, Ground motions and soil liquefaction during earthquakes. Earthquake Engineering Research Institute, Berkeley, CA, 1982) and Seed et al. (J Geotech Eng ASCE 109(3):458–483, 1983, J Geotech Eng ASCE 111(12):1425–1445, 1985) and the Idriss and Boulanger (2004) method. Critical cyclic stress ratio was based on the empirical relationship between standard penetration resistance and cyclic stress ratio. The liquefaction potential was evaluated by determining factor of safety against liquefaction with depth for areas in the city. A soil database from 200 boreholes covering an area of 262 km2 was used for the purpose. A design peak ground acceleration of 0.36 g was used since Guwahati falls in zone V according to the seismic zoning map of India. The results show that 48 sites in Guwahati are vulnerable to liquefaction according to the Seed and Idriss method and 49 sites are vulnerable to liquefaction according to the Idriss and Boulanger method. Results are presented as maps showing zones of levels of risk of liquefaction.

Numerical simulation of improvement of a liquefiable soil layer using stone column and pile-pinning techniques

Structures in seismically active regions are vulnerable to failure due to excess pore pressure generation and the liquefaction potential of underlying deposits, especially when no ground improvement is conducted. The risk of liquefaction and associated ground deformation can be reduced by various ground improvement techniques, such as the stone column (SC) and pile-pinning methods. In this paper, the effects of SCs and pile-pinning on reducing the potential for liquefaction during earthquakes are investigated parametrically, applying three-dimensional finite element (FE) simulations using OpenSeesPL. Saturated loose sand and silt layers are subjected to two realistic destructive events with different characteristics. The objective of this study is to assess the effectiveness of the SC and pile-pinning methods on the basis of several different factors, including area replacement ratio (Arr), soil and SC permeability, ground slope angle, pile/SC diameter, mass of the superstructure and earthquake characteristics. This parametric study evaluates the effect of each of these factors on soil acceleration, lateral displacement, excess pore pressure and shear stress–strain. The results are qualitatively in agreement with centrifuge test results and field observations. The numerical results provide a means of representing the seismic performance of the SC and pile-pinning at sites with liquefaction-induced lateral spreading and can be helpful in practical engineering applications.

A homogenization approach for evaluating the longitudinal shear stiffness of reinforced soils: column versus cross trench configuration

SUMMARYThe macroscopic linear elastic behaviour of inclusion‐reinforced soils, regarded as periodic composite media, is investigated by means of the homogenization theory. Special attention is given here to the determination of their longitudinal shear stiffness properties, which strongly govern the reinforced ground response under lateral loading. Combining the use of analytical, variational and numerical methods, we thoroughly examined three particular engineering‐relevant configurations: single trench, column and cross trench reinforcements. Fairly accurate closed‐form expressions are thus obtained, giving the value of the reinforced soil longitudinal shear stiffness as a function of the individual components shear moduli and reinforcement volume fraction. It is shown in particular that adopting a cross trench reinforcement layout instead of the classical column configuration results in a much higher improvement of the longitudinal shear stiffness. The results are then applied to assessing the reduction of soil liquefaction risk, which can be attributed to the presence of the reinforcing inclusions. Again, they clearly demonstrate the excellent performance of the cross trench configuration as compared with the complete inefficiency of the column reinforcement technique. Copyright © 2013 John Wiley & Sons, Ltd.

The influence of organic polymer on properties of mineral concentrates

AbstractTransport of mineral concentrates is associated with high risk of liquefaction of the cargoes. This type of goods containing water may liquefy and shift dangerously across the cargo compartments. Therefore, it is rational to limit the moisture content of the cargoes which may liquefy. To prevent sliding and shifting of ore concentrates in storage biodegradable materials composed of starch are added to the mineral concentrates. The influence of adding starch materials to the mineral concentrates on its parameters determining ability for safe shipment was assessed on the basis of determination of the following parameters: permeability, cohesion and internal friction angle of concentrates.

Examination of the liquefaction risk by a "Liquefaction Hazard Screening Survey"

Examination of the liquefaction risk by a "Liquefaction Hazard Screening Survey"

Electrical resistivity tomography investigation of coseismic liquefaction and fracturing at San Carlo, Ferrara Province, Italy

<p>Massive surface fracturing and sand ejection took place during the main shock of the May 20, 2012, earthquake (Ml = 5.9) in the Emilia-Romagna region, northern Italy. These phenomena were induced by the liquefaction of water-saturated sand layers, and they damaged several buildings, as well as many roads and sidewalks. They were clustered between the villages of Sant'Agostino and Vigarano Mainarda, located along a paleo-reach of the Reno River [Papathanassiou et al. 2012, this volume]. The subsurface surrounding two major (several decameters long) ground ruptures was investigated using electrical resistivity tomographies (ERT), as resistivity is strongly affected by the chemico-physical conditions of loose sediments. Italian regulations require the Municipalities within seismically active areas to develop maps of the potential liquefaction risk. Not all of the territories that are under this kind of risk have been investigated to date. A strong effort to improve this knowledge is therefore needed. Noninvasive geophysical methods can help to fill this gap, as high-resolution techniques are available with good result-to-cost ratios. Among the available methodologies, the most suitable are the methods based on electrical resistivity and permittivity, as they are highly sensitive to the presence of underground water. The ERT method has been carried out successfully across active faults, providing crucial paleoseismological information [Caputo et al. 2003, 2007]. […]</p>

Comment on “Annual probability and return period of soil liquefaction in Yuanlin, Taiwan attributed to Chelungpu Fault and Changhua Fault” by Lee et al., in Engineering Geology, 114: 343–353 (2010)

This note provides the overview of the calculation in soil liquefaction probability in Central Taiwan carried out by Lee et al. Although that estimation is by all means original and offers an in-depth evaluation on the liquefaction risk for Central Taiwan, we raised a few questions about its earthquake magnitude function, source-to-site distance function, and the fault distributions in Central Taiwan. We personally think that with those concerns being accounted for, that estimation should be more robust.

Estimation of the Liquefaction's Risk of a Soil Deposit under Seismic Solicitations: Petrochemical Zone of Skikda City

This study consists in estimating the risk (potential) of liquefaction of a soil deposit saturated when it is submitted to a horizontal seismic excitement to its basis while using the approach in total constraints. This approach requires the determination of the shear constraint τa developed by the seismic solicitation, For the determination of τa, an equivalent linear dynamic analysis with concentrated mass has been used to adapt (iterable proceeding) the module of shear and the factor of damping according to the level of the resulting shear deformations because, the constraint-distortion diagram of the layer is nonlinear with dissipation of energy by hysteresis for each cycle. For this reason, in this survey, the behavior of soil has been represented by a hyperbolic relation of Hardin and Drenevich. For the determination of τl, the graph of Seed and al based on the results of the SPT. The report of the two constraints permits the definition of safety factor against the risk of liquefaction (CSL).

Evaluation on Failure of Fiber-Reinforced Sand

Fiber reinforcement can help to enhance soil strength, stabilize near-surface soil layers, and mitigate the risk of soil liquefaction. Evaluation of the strength of fiber-reinforced soils needs a proper failure criterion. This study presents a three-dimensional failure criterion for fiber-reinforced sand. By assuming that the total strength of the composite is a combination of the shear resistance of the host soil and the reinforcement of fibers, a general anisotropic failure criterion is proposed with special emphasis on the effect of isotropically/anisotropically distributed fibers. An anisotropic variable, defined by the joint invariant of the deviatoric stress tensor and a deviatoric fiber distribution tensor, isintroducedinthecriteriontoquantifythe fiberorientationwithrespecttothestrainrate/stressdirectionatfailure.Withfurtherconsideration of the fiber concentration and other factors such as aspect ratio, the proposed criterion is applied to predicting the failure of fiber-reinforced sand in conventional triaxial compression/extension tests for both isotropically and anisotropically distributed fiber cases. The predictions are in good agreement with the test results available in the literature. The practical significance of using this criterion for such problems as inclinedslopestabilizationisbrieflydiscussed.DOI:10.1061/(ASCE)GT.1943-5606.0000737. © 2013 American Society of Civil Engineers. CE Database subject headings: Fiber reinforced materials; Failures; Anisotropy; Triaxial tests; Slope stability; Sand (soil type). Author keywords: Fiber-reinforced soil; Failure criterion; Anisotropy; Fiber distribution tensor; True triaxial tests; Slope stabilization.

Numerical modeling of response of a saturated porous seabed around an offshore pipeline considering non-linear wave and current interaction

The evaluation of pore pressure in the vicinity of an offshore buried pipeline is particularly important for pipeline engineers involved in the design of pipeline protection. Unlike previous investigations limited to linear wave loading, the seabed response around a buried pipeline due to combined non-linear wave and current loadings is investigated in this study. Based on third-order approximation for the wave–current interactions, a parametric study has been carried out to examine the influences of wave non-linearity and current on the pore pressure firstly. Numerical results demonstrate the significant effects of current in case of larger water depth, smaller period wave and fine sand. Then, the configuration and filled materials for a trench layer that normally is used for the protection of a buried pipeline are studied. The numerical results clearly show that an appropriate trench layer can reduce the risk of liquefaction around a pipeline.

A genetic algorithm approach for assessing soil liquefaction potential based on reliability method

Deterministic approaches are unable to account for the variations in soil’s strength properties, earthquake loads, as well as source of errors in evaluations of liquefaction potential in sandy soils which make them questionable against other reliability concepts. Furthermore, deterministic approaches are incapable of precisely relating the probability of liquefaction and the factor of safety (FS). Therefore, the use of probabilistic approaches and especially, reliability analysis is considered since a complementary solution is needed to reach better engineering decisions. In this study, Advanced First-Order Second-Moment (AFOSM) technique associated with genetic algorithm (GA) and its corresponding sophisticated optimization techniques have been used to calculate the reliability index and the probability of liquefaction. The use of GA provides a reliable mechanism suitable for computer programming and fast convergence. A new relation is developed here, by which the liquefaction potential can be directly calculated based on the estimated probability of liquefaction (P L ), cyclic stress ratio (CSR) and normalized standard penetration test (SPT) blow counts while containing a mean error of less than 10% from the observational data. The validity of the proposed concept is examined through comparison of the results obtained by the new relation and those predicted by other investigators. A further advantage of the proposed relation is that it relates P L and FS and hence it provides possibility of decision making based on the liquefaction risk and the use of deterministic approaches. This could be beneficial to geotechnical engineers who use the common methods of FS for evaluation of liquefaction. As an application, the city of Babolsar which is located on the southern coasts of Caspian Sea is investigated for liquefaction potential. The investigation is based primarily on in situ tests in which the results of SPT are analysed.

Evaluation of soil liquefaction risk on linearly structure considering the soil investigation locations

本論文は，実在する線状構造物（長大水路）の液状化危険度解析を通して，線状構造物の特性を考慮した信頼性解析の方法を提案し，その手順について詳述している。この研究で最も特徴的な提案は，Krigingを液状化危険度解析に応用し，調査地点と評価地点の位置関係を考慮して，地盤調査数や粗密に関わる不確実性を線状施設に沿って連続的に定量評価していることにある。ここで得られた結果に基づいて，簡易な問題設定に基づく試算を行い，線状構造物の対策の優先順位決定や追加地盤調査の実施地点の選定等，対応策立案の観点から考察を加え，本手法が施設管理のための有効な方法であることを示している。

The Liquefaction Risk Analysis of Fine Sand Filling Subgrade

It is signality for the Yangtse River estuary fine sand filling the highway subgrade which accounting for the lacking of filler and protecting along the line environment. Experiment results indicate that the sand has high strength, low compressibility, and good water stability. But the fine sand has some characteristics as grain uniformity, badness gradation, single structure, and the fine grain, and the fine sand filling subgrade is built on the soft soil foundation with high water table, so it is hidden troubles for the fine sand filling subgrade extending and application whether it can liquefy under the tempestuous earthquake load. The paper establish the liquefaction condition, carry through the liquefaction experiments and analysis the subgrade liquefaction risk relying on the Chong Ming connection engineering of Changjiang tunnel and bridge engineering. The analysis results indicate that the yangtse river estrary fine sand cannot liquefy with 7 class earthquake load, and it has no liequefaction conditions. So the subgrade has low liquefaction risk, and can be widely application.

Influence of Soil Saturation on the Free Field Response of Liquefiable Soils

Free field response of partially saturated sands to cyclic loading, with a particular attention to soil liquefaction has been studied. The study has been conducted using a numerical model elaborated for the liquefaction of partially saturated soils together with a cyclic elastoplastic constitutive relation implemented in a finite element program. The numerical model and the analysis of the influence of soil saturation on the free field response, for different positions of the water table have been investigated respectively. The result shows that the soil saturation degree largely affects the free field response to cyclic loading, with a decrease in soil saturation leading to a decrease in the rate of generation of excess pore-water pressure, and consequently to a reduction in the liquefaction risk.

The contribution of geophysical techniques to site characterisation and liquefaction risk assessment: Case study of Nafplion City, Greece

Abstract We present an example of how geophysical methodologies can considerably contribute to seismic and liquefaction risk assessment in an area where urban development is planned. The inspection for possible hidden faults by geophysical methods is particularly critical, since such a possibility could practically hinder the town planning in this area. However, even if no primary threats exist within the area, the response of the foundation soil to various scenarios of historical earthquakes, which have affected the place in the past, must be examined. The geophysical methodologies could also assist this analysis, contributing with the calculation of the amplification of the seismic motion from the bedrock up to the surface. The investigation area of Nafplion, Greece, was suspected to have high liquefaction potential since the foundation soil consists of loose sandy silt with a very shallow aquifer. The implementation of gravity and seismic methods considerably aided the investigation for possible seismic faults. Special emphasis was given to seismic depth migration and particularly to the construction of valid velocity models, in order to precisely calculate the dip characteristics of the structures. Shallow seismic techniques were also applied to provide the near-surface velocity structure, which is a prerequisite for assessing the liquefaction risk. In particular, our case study provides an example of how seismic methods (seismic reflection, seismic refraction, seismic modelling, MASW, multichannel analysis of microtremors and crosshole investigations) when combined with geotechnical borehole testing, enhance the reliability of their output and allow the coverage of wide areas in a cost-effective way in comparison to standard borehole tests. Data and information provided by the application of the geophysical methods were subsequently incorporated in the liquefaction risk assessment at several selected sites within the study area. Factors of safety against liquefaction and liquefaction potential values were computed for three scenario earthquakes that were selected on the basis of the known seismic impact of past earthquakes in the town of Nafplion. We found that liquefaction probability can reach values as high as 80% at some sites depending on the selected earthquake scenario. The formations most prone to liquefaction are detected at depths between 5 and 10 m. This information can be helpful for making risk-based design decision in this region.

Management of High Groundwater Level Aquifer in the Taipei Basin

Groundwater pumpings have been prohibited by the government since 1970 due to the overexploitation and severe land subsidence in the Taipei Basin. Declining water levels were gradually recovered back. Nowadays, high groundwater levels are developed in the Taipei Basin. This may cause safety problems such as seepage of underground facility, and liquefaction by the strong earthquake jeopardizing millions of people’s lives and properties in the metropolitan area of Taipei. To reduce the associated risks, the study aims to formulate a management strategy to rationally reduce the groundwater level declining trend and sustainable utilization of groundwater resources in the Taipei Basin. A hydrogeologic model of Taipei Basin using MODFLOW-96 was setup to evaluate water budget and safe yield of the aquifer. The simulated water budget indicates that the groundwater annual storage increases about 17 million cubic meters in the main (Jingmei) aquifer. The average groundwater safe yield of the Taipei Basin estimated by the Hill method is about 54 million cubic meters per year. Moreover, with consideration of the reduction of liquefaction risks the revised average safe yield is about 126 million cubic meters per year. To effectively use and manage groundwater resources, restriction order on the use of groundwater resources in the Taipei Basin need to be revised. The implementation of groundwater management index coupled with an upper limit of the average groundwater level set as −7.5 m below the surface for avoiding earthquake caused liquefaction is suggested to manage the groundwater level for safe-use of groundwater resources in the Taipei Basin.

Nonlinear Seismic Response and Damage of Reinforced Concrete Ducts in Liquefiable Soils

Highly inelastic nonlinear interaction of liquefied soil and underground RC ducts is computationally investigated in view of the structural damage. The required ductility is expected to be insensitive to the risk of liquefaction for normally deposited layers of soil, and the lesser ductility is acceptable for the case of highly liquefiable foundation similar to the seismic isolation. Although the structural nonlinearity has a fewer effect on the uplift of the underground ducts, the amount of main reinforcement may control the structural damage with the same efficiency for both drained and undrained soil deposits.

On site characterization and air content evaluation of coastal soils by image analysis to estimate liquefaction risk

Coastal structures are often submitted to intense wave forcing. In some cases, structures may have stability disorders due to the constant weakening of their foundations and to momentary liquefaction of the sea bed. Studies have shown that if classical geotechnical characterization is a necessity, air content in the soil is also a key parameter for liquefaction evaluation. That is why on site air content measurement and its time variation during a tide period may provide information and help to determine a better understanding of this problem. Unfortunately, this parameter is difficult to measure during investigations. This article presents a technique based on the use of geoendoscopy and automatic image analysis, which makes it possible to characterize coastal soils and to estimate their air content. After a description of the technique, the results obtained on laboratory tests and on a real site are presented.