Liquefaction Failure Research Articles

Processes That Initiate Turbidity Currents and Their Influence on Turbidites: A Marine Geology Perspective

How the processes that initiate turbidity currents influence turbidite deposition is poorly understood, and many discussions in the literature rely on concepts that are overly simplistic. Marine geological studies provide information on the initiation and flow path of turbidity currents, including their response to gradient. In case studies of late Quaternary turbidites on the eastern Canadian and western U.S. margins, initiation processes are inferred either from real-time data for historical flows or indirectly from the age and contemporary paleogeography, erosional features, and depositional record. Three major types of initiation process are recognized: transformation of failed sediment, hyperpycnal flow from rivers or ice margins, and resuspension of sediment near the shelf edge by oceanographic processes. Many high-concentration flows result from hyperpycnal supply of hyperconcentrated bedload, or liquefaction failure of coarse-grained sediment, and most tend to deposit in slope conduits and on gradients < 0.5° at the base of slope and on the mid fan. Highly turbulent flows, from transformation of retrogressive failures and from ignitive flows that are triggered by oceanographic processes, tend to cannibalize these more proximal sediments and redeposit them on lower gradients on the basin plain. Such conduit flushing provides most of the sediment in large turbidites. Initiation mechanism exerts a strong control on the duration of turbidity flows. In most basins, there is a complex feedback between different types of turbidity-current initiation, the transformation of the flows, and the associated slope morphology. As a result, there is no simple relationship between initiating process and type of deposit.

Liquefaction potential of coastal slopes induced by solitary waves

Tsunami runup and drawdown can cause liquefaction failure of coastal fine sand slopes due to the generation of high excess pore pressure and the reduction of the effective over burden pressure during the drawdown. The region immediately seaward of the initial shoreline is the most susceptible to tsunami-induced liquefaction failure because the water level drops significantly below the still water level during the set down phase of the drawdown. The objective of this work is to develop and validate a numerical model to assess the potential for tsunami-induced liquefaction failure of coastal sandy slopes. The transient pressure distribution acting on the slope due to wave runup and drawdown is computed by solving for the hybrid Boussinesq—nonlinear shallow water equations using a finite volume method. The subsurface pore water pressure and deformation fields are solved simultaneously using a finite element method. Two different soil constitutive models have been examined: a linear elastic model and a non-associative Mohr–Coulomb model. The numerical methods are validated by comparing the results with analytical models, and with experimental measurements from a large-scale laboratory study of breaking solitary waves over a planar fine sand beach. Good comparisons were observed from both the analytical and experimental validation studies. Numerical case studies are shown for a full-scale simulation of a 10-m solitary wave over a 1:15 and 1:5 sloped fine sand beach. The results show that the soil near the bed surface, particularly along the seepage face, is at risk to liquefaction failure. The depth of the seepage face increases and the width of the seepage face decreases with increasing bed slope. The rate of bed surface loading and unloading due to wave runup and drawdown, respectively, also increases with increasing bed slope. Consequently, the case with the steeper slope is more susceptible to liquefaction failure due to the higher hydraulic gradient. The analysis also suggests that the results are strongly influenced by the soil permeability and relative compressibility between the pore fluid and solid skeleton, and that a coupled solid/fluid formulation is needed for the soil solver. Finally, the results show the drawdown pore pressure response is strongly influenced by nonlinear material behavior for the full-scale simulation.

THREE‐DIMENSIONAL MODELLING AND ANALYSIS OF DINOSAUR TRACKWAYS

Abstract: Light Detection And Range (LiDAR) imaging provides a means to model the 3D geometry of fossil tracks in the field with high accuracy. This represents a considerable advance for the science of vertebrate ichnology in which traditional field methods suffer from a significant degree of abstraction and lack the resolution required to interpret tracks quantitatively. Three‐dimensional LiDAR models provide additional morphometric information and allow the application of new analytical tools unique to the digital environment. The method will enable fossil track morphometrics to develop into an iterative process that combines 3D visualization and multivariate statistical methods, blending qualitative and quantitative approaches and allowing track morphologies to be compared holistically. Modelling of trackways from Fumanya (south‐east Pyrenees) using LiDAR has enabled variation in linear track dimensions to be explained by the varied contribution of different modes of shear with increasing depth below the foot/sediment interface. Features in the relief of pes traces indicate that subsurface zones within their track volumes are defined by the interaction of puncture and local shear, below a surface zone of liquefaction failure now lost to erosion. This model of mechanical failure enables a preliminary review of the pedal kinematics of titanosaurid sauropod dinosaurs and suggests multiphase loading of the sediment by the titanosaurid pes. However, from inspection of these 3D surfaces alone it is not possible to differentiate between the possibility of one or two discrete phases of pedal motion preceding the toe‐off event at the maximum height of the support phase. By integrating LiDAR models with analogue modelling within a 3D digital environment it will be possible to clarify such interpretations of fossil tracks and the locomotor mechanics of extinct animals.

Recent Developments in Liquefaction Research Learned from Earthquake Damage

The current understanding of mechanisms for liquefaction failure is briefly reviewed based on previous investigations and case studies on recent earthquakes. The liquefaction-induced failure modes addressed include free surface settlement, the settlement of shallow foundations, uplift in buried structures and lateral flow. Of these, lateral flow failure, the mechanism of which remains poorly understood, is focused on by introducing different viewpoints of soil mechanics. Special attention is paid to recent findings on the void redistribution effect due to soil stratifications that may explain extremely large flow displacement even in soils on the dilative side of the steady-state line.

A Short Note for Dr. Ishihara's Review in 1974

In the paper written in the 1970s by Prof. Kenji Ishihara, case histories for the 1964 Niigata earthquake and preceding earthquakes were addressed followed by overviews on laboratory studies, in situ investigations, and analyses of liquefaction. The research efforts overseen by Prof. Ishihara have been developed considerably since then for reliably evaluating liquefaction potential for a variety of soils unqer different geotechnical and seismic conditions and for mitigating liquefaction failure through ground improvement. Despite great advances in this aspect of liquefaction research, problems vital to reasonable design methodology remain. One is postliquefaction soil behavior, which plays an important role in soil-structure interactions in performance- based design of buildings and civil structures. Unlike other earthquake failures, serious damage often occurs in the postliquefaction phase due to static and monotonic straining by dead loads in liquefied soil where little residual shear strength remains. Great uncertainties remain on how to evaluate postliquefaction ground deformation, together with soil-structure interactions, concerning differential settlement, uplift, and lateral displacement. Current engineering practices tend to avoid uncertainties by employing soil treatment or rigid foundations to prevent soil liquefaction in advance. However, with design earthquakes becoming larger, it becomes unrealistic to depend too much on such costly measures. In contrast to the paper by Prof. Ishihara, the preceding paper has addressed liquefaction-induced structural damage during recent earthquakes from the 1964 Niigata earthquake to the present. Typical failure modes associated with damage have been identified from the viewpoint of their mechanisms and mitigation measures. Among them, the postliquefaction lateral flow mechanism, which still seems quite controversial, has been discussed in detail by introducing different views on soil behavior causing lateral flow or spreading. Special emphasis has been placed on recently evolving research results considering the effect of void redistribution due to soil stratification.

Liquefaction Phenomena underneath Marine Gravity Structures Subjected to Wave Loads

The foundation of a vertical breakwater or offshore gravity platform may fail due to wave loading. The question is discussed whether liquefaction phenomena in a sandy subsoil, such as the generation of residual excess pore pressures and cyclic mobility, may significantly contribute to such failure. Theory, descriptions of prototype failure cases, and several scale tests are analyzed. It is concluded that the most spectacular failure type “liquefaction flow failure” is only possible in the case of a subsoil of very loose sand or silt combined with a low drainage potential, e.g., by the presence of a clay layer or large structure dimensions. Three other potential failure types are more likely in other cases: stepwise liquefaction failure, stepwise failure, and wobble failure. Their relevance increases with decreasing relative density and decreasing drainage potential. Brief recommendations for assessment of each failure type are presented.

Landslide disasters triggered by the 2004 Mid-Niigata Prefecture earthquake in Japan

Synopsis During the 2004 Mid-Niigata Prefecture earthquake, thousands of landslides were triggered. Among them five catastrophic landslides were introduced in this paper. In addition, the influence of rainfalls in prior to the earthquake and the urgent response to prevent disastrous failure of landslide dams were also discussed and presented. Higashi Takezawa and Terano landslides occurred within past landslide masses and dammed the river at the toe of the landslides, causing great damages to the properties. Detailed field investigation was performed on these two landslides. To examine the triggering and movement mechanisms, samples were taken from these landslides. By using a ring shear apparatus, real earthquake wave loading test and cyclic loading tests were performed on these samples. The test results revealed that those sand samples from both landslides can suffer from sliding surface liquefaction phenomenon with very lower final apparent friction angles, while the silt sample from Terano landslide showed no liquefaction failure, indicating that landsliding during this earthquake time was triggered within the sand layer above the silt layer in the past landslide masses. Finally, the movement of Higashi Takezawa landslide was simulated.

Dynamic properties of earthquake-induced large-scale rapid landslides within past landslide masses

During the 2004 Mid-Niigata Prefecture earthquake, thousands of landslides were triggered, among them two large-scale rapid landslides (Higashi Takezawa and Terano landslides) occurred within past landslide masses and dammed the river at the toe of the landslides, posing great risks for the society. Detailed field investigation was performed on these two landslides. To examine the triggering and movement mechanisms, samples were taken from these two landslides. By using a ring shear apparatus, real earthquake wave loading test and cyclic loading tests were performed on these samples. The test results revealed that those sand samples from both landslides can suffer from sliding surface liquefaction phenomenon with very low final apparent friction angles, while the silt sample from Terano landslide showed no liquefaction failure, indicating that the sliding surfaces of these rapid landslides must have been formed within the sand layer in the past landslide masses.

A study of the liquefaction risk potential at Yuanlin, Taiwan

The method by Iwasaki et al. [Iwasaki, T., Arakawa, T., Tokida, K., 1982. Simplified procedures for assessing soil liquefaction during earthquakes. Proceedings of the Conference on Soil Dynamics and Earthquake Engineering, Southampton, UK, pp. 925–939] for evaluating the liquefaction failure potential is widely used in Japan, Taiwan, and other countries due to its ease of use and general applicability. In this method, an index, called the Liquefaction Potential Index ( I L), is calculated based on an integration of the calculated factor of safety ( F s) over depth with a weighting function. Iwasaki et al. (1982) provided a set of criteria to interpret the calculated index I L based on a calibration with his dataset of field performance cases. However, in their method, the factor of safety ( F s) is based on the liquefaction evaluation method adopted in the Japanese Highway Bridge Design Code [JSHE, 1990. Highway Bridge Design Guide Book. Japan Society of Highway Engineering, in Japanese]. Whether other liquefaction evaluation methods can be used in conjunction with the index I L or not needs further investigation. In this paper, the Cone Penetration Test (CPT) data from Yuanlin, Taiwan, the area that suffered the most from liquefaction in the 1999 Chi-Chi, Taiwan, earthquake, are analyzed. Three CPT-based methods are used for the calculation of the factor of safety for these cases derived from the Chi-Chi earthquake. These factors of safety are used to define the liquefaction potential and risk indexes. The calculated indexes are then used to construct the failure potential maps, and these maps are checked with the field observations. The study shows that the Liquefaction Risk Index ( I R) defined in conjunction with the Juang et al. [Juang, C.H., Yuan, H., Lee, D.H., Lin, P.S., 2003. Simplified CPT-based method for evaluating liquefaction potential of soils. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, vol. 129, no. 1, pp. 66–80] method yields the best result in interpreting field observations.

Downslope volume enlargement of a debris slide–debris flow in the 1999 Hiroshima, Japan, rainstorm

Following a heavy rainstorm on 29 June 1999, hundreds of slope failures occurred in granitic mountains in Hiroshima Prefecture, Japan. Among these events, a highly mobile landslide (termed the Kameyama landslide in this paper), which occurred in Kameyama area of Hiroshima city, was the most catastrophic, and was investigated in detail. The displaced soil mass from the source area of this landslide traveled about 300 m and deposited a volume more than 10 times as great as that in the source area. The landslide originated in and traversed a valley-shaped concave slope covered by pre-existing colluvial debris deposits. In addition, a spring was visible in the source area and very shallow ground water was observed in an observation pit dug in the source area. Thus, it is inferred that the ground-water table rose quickly during the rainfall, and that this rise triggered the slope failure in the source area. Based on a field survey along the landslide cross section, a possible explanation for the mechanism of the landslide was obtained: the displaced soil mass from the source area impacted the debris deposit in the path of the landslide, thus triggering liquefaction failure of the saturated part of debris. The original landslide and the liquefied debris then moved downslope as a single mass. To examine this assumption, ring-shear tests were performed on samples taken from the source area. Undrained ring-shear tests on the saturated samples showed that the sample is highly liquefiable, and liquefaction failure could have been triggered in the debris deposits by a very small impact from the displaced soil mass of the initial failure. In addition, laboratory tests simulating the impacts on the debris deposits at natural water content, i.e., unsaturated (at the survey time, 2 days after the failure) showed that although shear failure could be caused by the assumed impact force, the displaced soils stopped after a few centimeters displacement, indicating that existence of a saturated zone in debris deposits is prerequisite for this kind of failure.

The importance of breaching as a mechanism of subaqueous slope failure in fine sand

Large bank failures, comprising up to 106 m3 of sediment, are common features along steep channel banks in estuaries and large rivers that consist of clean, fine sands, and are mostly assumed to be generated by sudden liquefaction of large masses of very loosely packed sand. Another less commonly recognized type of failure is manifested by the gradual retrogression of a very steep wall, steeper than the angle‐of‐repose. Instead of the voluminous surging plastic sediment‐water flow, or hyperconcentrated density flow (sensu Mulder &amp; Alexander, 2001) generated by liquefaction, this type of failure, known as breaching by dredging companies and hydraulic engineers, produces a sustained quasi‐steady, turbidity current. To date, sedimentologists have not recognized the process of breaching as such. In this paper, it is suggested that breaching may be the origin of many thick, massive sand layers known from ancient deposits from various environments, notably in some turbidite successions. Possible differences in the sedimentary structure of the deposits produced by breach failures vs. liquefaction slope failures (=liquefaction flow slides) can be deduced from a knowledge of the sediment transport processes initiated by the failure. A field study is presented on some poorly structured beds in the Eocene Vlierzele Sands in Belgium, which are supposed to have originated from liquefaction failures, but are reinterpreted to be the products of breaching. It is postulated that the local steep slope disturbance required to initiate an active breach can be produced by a small liquefaction slope failure (=liquefaction flow slide failure) or local erosion by river or tidal channel flow at the initial stage of the failure event.

CANLEX full-scale experiment and modelling

A major aim of the Canadian Liquefaction Experiment (CANLEX) was to verify analysis procedures for predicting liquefaction phenomena. Towards this purpose, two loading events were carried out: a field event comprising a clay embankment built over a loose sand foundation layer, and a centrifuge test performed on a model of a sand embankment structure. Both the field event and the centrifuge model were planned so as to induce a static liquefaction failure and were instrumented to observe their response in terms of displacement and pore pressure. The fundamental mechanical characteristics of the foundation layer were determined from laboratory element tests (triaxial and simple shear). These tests formed the basis for the stress-strain modelling used in the numerical analyses. Two fundamentally different modelling techniques were used. One involved a fully coupled plasticity model, and the other involved a model based on a collapse-surface approach. The model and prototype structures were then analyzed and the predicted results in terms of displacements and pore pressures were compared with the measured values. The results from both approaches were found to be in reasonable agreement with the measurements, provided allowance was made for direction of loading and drainage effects were accounted for.Key words: liquefaction, field experiment, embankment, centrifuge model, elastic-plastic model.

CANLEX full-scale experiment and modelling

A major aim of the Canadian Liquefaction Experiment (CANLEX) was to verify analysis procedures for predicting liquefaction phenomena. Towards this purpose, two loading events were carried out: a field event comprising a clay embankment built over a loose sand foundation layer, and a centrifuge test performed on a model of a sand embankment structure. Both the field event and the centrifuge model were planned so as to induce a static liquefaction failure and were instrumented to observe their response in terms of displacement and pore pressure. The fundamental mechanical characteristics of the foundation layer were determined from laboratory element tests (triaxial and simple shear). These tests formed the basis for the stress-strain modelling used in the numerical analyses. Two fundamentally different modelling techniques were used. One involved a fully coupled plasticity model, and the other involved a model based on a collapse-surface approach. The model and prototype structures were then analyzed and the predicted results in terms of displacements and pore pressures were compared with the measured values. The results from both approaches were found to be in reasonable agreement with the measurements, provided allowance was made for direction of loading and drainage effects were accounted for.Key words: liquefaction, field experiment, embankment, centrifuge model, elastic-plastic model.

Study on the Excess Pore Pressure Generation at Failure and the Resulting Movement of Sandy Slope in Flume Test by Rainfall

By using a small flume, a series of tests has been carried out to trigger rainfall-induced-slope failure. The detailed monitoring of excess pore pressure and the soil displacement revealed that a high excess pore pressure was generated not before the failure, but during the subsequent motion after the failure. The variation of shear stress, normal stress and pore pressure during failure shows that approximately full liquefaction failure could be initiated even when the soil was in naturally drained state in slopes. By using silica sand no. 7 (D50 = 0.14 mm) and no.8 (D50 = 0.0576 mm) and changing the samples' initial dry density and flume angle (20 and 30 degrees), the effects of grain size, initial density and flume angle on the generated pore pressure and fail-ure mode were analyzed. Results from tests of different initial densities show that there is an optimal density index for excess pore-pressure generation. Moreover, observed failure phenomena show that the failure mode was dependent greatly on the grain size and flume angle. In fact, flowslides were initiated in the tests on finer silica sand (no. 8) when the flume angle was 30 degrees, while in other tests, just retrogressive sliding ap-peared.

"Remedial Measures Against Soil Liquefaction: From Investigation and Design to Implementation" edited by The Japanese Geotechnical Society

The liquefaction of loose, saturated soils is a phenomenon observed since human beings began recording the effects of earthquakes. Whether expressed as sand boils, flow slides, or simply foundation distress, it is widespread and requires careful attention by engineers, who must recognize its potential and prevent its occurrence, or deal with its consequences. While qualitative descriptions of liquefaction and sand boils abounded in the early literature, the extensive and costly liquefaction failures during the 1964 earthquakes at Anchorage, Alaska and Niigata, Japan prompted the geotechnical research community to undertake serious study of the problem. The result is that, over the last thirty-five years, the geotechnical engineering communities in Japan and the United States have developed a sophisticated understanding of the behavior of soils under dynamic and cyclic loading. Many questions remain unanswered, and there is a lot of controversy over important issues, but the research community has answered the central...

Wave-Induced Seabed Instability: Difference Between Liquefaction and Shear Failure

The mechanism of wave-induced instability in a permeable seabed have been studied for more than two decades. The distinction between shear failure and liquefaction, however, has not been clearly defined. This paper presents a fundamental study on the differences in two failure modes for a fully saturated seabed of both finite and infinite thickness. The wave-induced effective stresses and pore pressure, obtained from an analytical solution of Biot’s pore-elastic consolidation theory, were employed to examine the failure modes under a two-dimensional plane strain condition. A case study is presented to examine the failure modes with respect to several parameters, such as excess pore pressure, seepage flow, seepage force, failure areas and stress path in the seabed. The conclusions obtained from this study were as follows; (1) the thickness of a permeable seabed affects the pore pressure and effective stress response to ocean waves and the failure mode of the seabed, (2) either a liquefaction or shear failure, or both, occur in the seabed, even in the saturated seabed, (3) the Mohr-Coulomb’s failure criterion, when combined with elastic stresses, can not be employed to estimate the liquefaction failure in the seabed, (4) the liquefaction can be evaluated by a criterion in terms of the excess pore pressure, (5) The liquefied zone in the seabed is significantly different from the shear failure zone. The shape beneath the seabed surface for the former is almost identical to the contour where the upward seepage flow is concentrated.

Liquefaction Failure and Remediation: King Harbor Redondo Beach, California

Liquefaction failure, including large lateral displacements and associated settlement, severely damaged marina facilities at Redondo Beach King Harbor during the Northridge Earthquake of January 17, 1994. Although minor ground deformation apparently occurred in several areas of the harbor, severe damage was restricted to the central portion of mole B, one of four offshore fills constructed as a part of marina improvements in 1960–61. Local ground conditions and methods used to remediate liquefaction are presented and discussed. Two ground modification techniques were used to mitigate the liquefaction potential of the reconstructed mole b facilities. The major portion of the failure area was treated with vibroreplacement stone columns. Vibratory displacement and installation of the gravel columns not only densified the foundation soils, but also provide additional strength and drainage capacity. Compaction grouting was used to densify foundation soils in the vicinity of existing improvements that were considered sensitive to construction-induced ground vibrations. These ground improvement techniques effectively reduced the liquefaction potential and allowed the marina improvements to be reconstructed on shallow foundations similar to the original design.

A model for the runout analysis of rapid flow slides, debris flows, and avalanches

Runout analyses are used for risk assessment and design of remedial measures against rapid landslides such as debris flows, debris avalanches, rockslide avalanches, large-scale liquefaction failures, and slides of fill and mining waste. A continuum model has been developed to simulate the characteristics of these phenomena. The model is based on a Lagrangian solution of the equations of motion and allows the selection of a variety of material rheologies, which can vary along the slide path or within the slide mass. It also allows for the internal rigidity of relatively coherent slide debris moving on a thin liquefied basal layer. The effects of lateral confinement are accounted for in a simplified manner. The model is shown to compare favourably with results of controlled laboratory experiments and other analytical tools for several different materials and problem configurations. Examples of the practical use of the model to predict the runout of coal mine waste flow slides and flows of liquefied granular tailings are presented. Key words : landslides, dynamic analysis, runout prediction, debris flows, debris avalanches, flow slides.

Collapse of dry sand

Loose cohesionless saturated materials have proved responsible for a number of serious or catastrophic flow slides. Liquefaction failures with no obvious triggering mechanism have also been recorded. This phenomenon of sudden liquefaction without a presence of cyclic shear stresses is often referred to as spontaneous or static liquefaction. Results from previously published studies suggest that liquefaction is triggered not by the undrained loading and generation of pore pressures but by the collapse of the metastàble sand structure, which in turn generates the driving pore pressures in a saturated material. Hence, the collapse is a characteristic response of a material to certain stress states rather than a result of some enforced undrained loading. This theory is evaluated on very loose dry Ottawa sand. It is shown that the very loose dry sand when subjected to a constant deviatoric stress path significantly changes its behavior at a certain discreet stress state, increases compressibility, and becomes increasingly unstable. This results in collapse – vigorous contraction of the specimen. This structural collapse appears to be equivalent to the pore-pressure generation in collapsing, very loose saturated sand. Key words : dry sand, collapse, liquefaction, stress path, triaxial cell.

Liquefaction and flow failure during earthquakes : Ishihara, K GeotechniqueV43, N3, Sept 1993, P351–415

Liquefaction and flow failure during earthquakes : Ishihara, K GeotechniqueV43, N3, Sept 1993, P351–415