Degree Of Liquefaction Research Articles

Influence of foundation type on seismic response of low-rise structures in liquefiable soil

The 2010–2011 Canterbury Earthquake Sequence (CES) caused extensive damage to low-rise structures in the city of Christchurch, New Zealand, mainly due to liquefaction-induced effects including settlement and angular distortion. This paper will present the results of dynamic centrifuge tests comparing the effects of liquefaction on the seismic performance of isolated structures with different types of shallow foundations (strips or a raft), and the effect of being situated adjacent to a heavier neighbouring structure of the same foundation type (i.e. considering structure-soil-structure interaction, SSSI). Performance will be evaluated under a sequence of successive earthquakes from the 2010–2011 CES and 2011 Tohoku Earthquake, Japan, to permit study under ground motions and aftershocks generating full liquefaction either extensively or to only a limited depth below ground level. The results show firstly that lower intensity ground shaking occurs at the ground surface when liquefaction occurs and that this can be estimated as a function of the degree of liquefaction using a simple estimation method. When subjected to these ground motions, using strip foundations for isolated structures can result in a reduction in structural demand, especially when the soil is extensively liquefied. When a neighbouring structure with the same foundation type is present, the effects of SSSI within liquefied soil result in changes to natural period and damping such that raft-founded structures exhibited lower structural demands. In either case (isolated or adjacent), a reduction in structural demand is accompanied by an increase in post-earthquake permanent foundation deformation.

Real-time imaging and control of boiling histotripsy lesion formation using Doppler ultrasound

In boiling histotripsy (BH), millisecond-long HIFU bursts with shocks are used to mechanically liquefy tissue. Most BH studies have been performed under real-time B-mode ultrasound imaging of bubbles generated at the treatment site. However, such approach does not allow quantitative assessment of the degree of tissue liquefaction. In addition, aberration and clutter often limit the echogenicity introduced by bubbles. In this work, plane wave Doppler followed by B-mode imaging were implemented immediately after each BH pulse to visualize residual bubble motion during volumetric BH treatments in ex vivo bovine liver. The changes in the Doppler power and speed were used as metrics to assess the degree of tissue liquefaction. An ATL P6-3 imaging probe connected to a Verasonics Ultrasound Engine (VUE) was mounted in the central opening of a 256-element 1.5 MHz HIFU array driven by another VUE with 1.2 kW external power source enhanced by a capacitor bank. The proposed imaging sequence improved BH targeting and bubble visualization. As tissue liquefaction progressed from partial to full (single versus five BH pulses per focal spot), both Doppler power and residual bubble velocity directed away from the transducer increased (7-fold and 10 cm/s to 20 cm/s, correspondingly) and then saturated. [Work supported by NIH R01EB7643.]

Pumping effect of wave-induced pore pressure on the development of fluid mud layer

Fluid mud widely exists in the movement of fine sediment, which is an important potential cause of marine geological disasters. It is important to understand the generation and migration mechanism of fluid mud. The purpose of this study is to investigate the vertical migration response of fine-grained sediments by wave-fluid test of pore pressure response of silty seabed under wave action. The results show that the adhesion between the silt particles and the additional pressure of the film water have a significant effect on the liquefaction characteristics of the silt. Even if the liquefaction degree is far more than 100%, the soil does not completely liquefy. The experiment result show that, there is concentrated movement of the split channel, and mesoscopic migration of fine particles between the gaps of the particles, pumping effect provides an effective source of supply for the development of the floating mud layer, it also exacerbates modern sedimentation when strengthening the vertical exchange of shallow soil in the seabed. Besides, the blending of the middle and lower layers of the previous soil with the recent sediments has increased the difficulty of identifying the time series of the modern sedimentary layer to some extent.

Properties and Engineering Influence of Corewall Filter I with Different Fine Particle Contents

The protection provided by filter I for the corewall constitutes an important safety guarantee for the impervious bodies of corewall dams. In particular, the fine particle content (the content of particles < 0.075 mm in size) of filter I provides a filter protection effect for the corewall. Furthermore, this also determines its own drainage characteristics as an important gradation requirement for filter design. In practical engineering, due to the nature of the aggregate source, the crushing and screening process, and rolling construction, the fine particle content may exceed relevant standards. Relying on the field measured gradation envelope of the filter of a gravelly earth core rockfill dam project, this study prepared two classes of filter I (i.e., filter I of class I with a fine particle content of 8%, and filter I of class II with a fine particle content of 12%). Permeability property test, large-scale compression test, large-scale static triaxial test, and large-scale dynamic triaxial test were conducted. Furthermore, dynamic finite-element calculation of the dam under seismic action was performed, and the anti-seismic liquefaction property of the filter was analyzed. According to the permeability property test, the permeability coefficients of the two classes of filter I were both 1∼5×10−3 cm/s. Lower content of particles < 0.075 mm in size increased the permeability coefficient. According to the mechanical test, the stress-strain test curves of both classes of filter I presented nonlinearity, compressive hardening, elastoplasticity, and other general laws. The strength index and deformation resistance both increased with increasing relative density. Under the same relative density, both strength index and deformation resistance declined with increasing fine particle content. According to the dynamic finite-element anti-seismic liquefaction analysis on filter I of class II (with a content of particles < 0.075 mm in size of 12%) under seismic action, the liquefaction degree had a maximum value of 0.58 (less than 0.8), and the anti-liquefaction safety coefficient had a minimum value of 1.72, which would not trigger liquefaction of filter I. This experimental study and computational analysis offers references for the exploration of the gradation design of filter I of earth core rockfill dams and investigates the related engineering influence.

Wettability analysis method for assessing the effect of chemical pretreatment on brown coal biosolubilization by Gordonia alkanivorans S7

Coal wettability is of considerable importance for determining the efficiency of the solubilization process. In principle, hydrophobic coal structure should be modified for effective contact with microorganisms in the coal biosolubilization process. The paper considers the image analysis method for determining the contact angle of chemically pretreated coal, where the measurement surface is prepared by pressing coal powder into tablets. Due to sessile drop asymmetry resulting from the heterogeneity of the substrate, liquid-solid contact angles are evaluated along a three-phase contact line. The source of a three-dimensional drop image is a scan obtained with an infrared light beam from an optical coherence tomography device. The effect of coal pretreatment on biosolubilization by Gordonia alkanivorans S7 was investigated with the use of the method. To emphasize the relationship between coal wettability (hydrophilicity or hydrophobicity) and the possibility of coal liquefaction, Fourier Transform Infrared (FT-IR) spectroscopic analyses were performed. Data obtained from infrared spectra showed changes in coal structure and confirmed a positive influence of nitric acid on coal biosolubilization. Due to a high liquefaction degree, it is possible to implement the process of lignite biosolubilization by G. alkanivorans S7 on a larger scale. The contact angle measurement method can be successfully applied in the selection of methods for the chemical and biological conversion of coal in various technological processes.

The research of rheological properties of bagasse based paste

In the horticultural industry, upon main products obtaining, the formation of the following secondary raw materials and production wastes: pulping,bagasse, tomato seeds, fruit seeds, vegetable peelings, etc. is concomitant. At the same time, the amount of secondary raw materials formed during fruit and vegetable raw materials processing varies from 5 to 85% of the initial raw materials mass going for processing, of which an average of 30% is sent to food products for food processing. The aim of the work was to study the possibility of bagasse using of direct extraction beet juice production in vegetable paste technology. To facilitate the process of bagasse pulping, pretreated with microwave heating, starch syrup, allowing to reduce the vegetable mass viscosity was proposed to use. As a result of research, it was found that the introduction of starch syrup in the bagasse in the amount of 10, 20 and 30%, along with an increase in the heating temperature, varying from 25 to 60, reduces the effective viscosity obtained after bagasse paste pulping. With an increase in the starch syrup dosage, an increase in the mass fraction of dry substances in beet paste and its liquefaction degree was observed as well. So, at a dosage of 10%, the liquefaction degree was 24.7%, at 20% - 45.1%, at 30% - 60.7%. Thus, the use of starch syrup in the production of beet paste from the bagasse of direct-pressed juice production makes it possible to adjust the vegetable mass viscosity purposefully, creating better conditions for subsequent technological operations. .

In vitro assessment of stiffness-dependent histotripsy bubble cloud activity in gel phantoms and blood clots

As a bubble-based ablative therapy, the efficacy of histotripsy has been demonstrated in healthy or acutely diseased models. Chronic conditions associated with stiff tissues may require additional bubble activity prior to histotripsy liquefaction. In this study, histotripsy pulses were generated in agarose phantoms of Young’s moduli ranging from 12.3 to 142 kPa, and in vitro clot models with mild and strong platelet-activated retraction. Bubble cloud emissions were tracked with passive cavitation imaging, and the threshold acoustic power associated with phantom liquefaction was extracted with receiver operator characteristic analysis. The power of histotripsy-generated emissions and the degree of liquefaction were tabulated for both clot models. For the agarose phantoms, the acoustic power associated with liquefaction increased with Young’s modulus. When grouped based on agarose concentration, only two arms displayed a significant difference in the liquefaction threshold acoustic power (22.1 kPa versus 142 kPa Young’s modulus). The bubble cloud dynamics tracked with passive cavitation imaging indicated no strong changes in the bubble dynamics based on the phantom stiffness. For identical histotripsy exposure, the power of acoustic emissions and degree of clot lysis did not vary based on the clot model. Overall, these results indicate that a fixed threshold acoustic power mapped with passive cavitation imaging can be utilized for predicting histotripsy liquefaction over a wide range of tissue stiffness.

Ultrafine grinding of poplar biomass: effect of particle morphology on the liquefaction of biomass for methyl glycosides and phenolics

This paper shows that mechanical ultrafine grinding of poplar wood is an efficient pretreatment approach to enhance its reactivity during liquefaction. The microstructural features and chemical properties of biomass samples with different particle morphology were studied. In particular, we found that more cellulose and hemicellulose were exposed on the outer surface of the ultrafine powder (cellular scale of plant) and the crystal lattice structure of cellulose was significantly damaged. As a result, the degree of liquefaction reached 92.03% at 180 °C using UP feedstock, largely exceeding the value (53.35%) obtained at the same temperature using PS0.25. Two groups of value-added chemicals, namely phenolics and methyl glycosides were obtained during liquefaction. At 180 °C, the yields of methyl glycosides and phenolics obtained from an UP feedstock were, respectively, 28.45% and 10.17% higher than those obtained from the PS0.25. In addition, a high degree of liquefaction (> 90%) could be obtained at a temperature 40 °C lower than the one required by PS0.25, greatly reducing the occurrence of side reactions and improving the purity of target products. Overall, the mechanical fragmentation of biomass at cellular scale is a promising pretreatment method allowing high valorization of the entire biomass.

Influence of inherent anisotropy on the seismic behavior of liquefiable sandy level ground

Inherent anisotropy is a crucial aspect to consider for an improved understanding of the strength and deformation characteristics of granular materials. It has been the focus of intense investigation since the mid-1960s. However, inherent anisotropy’s influence on ground seismic responses, such as liquefaction, has not been extensively studied. In this paper, inherent anisotropy’s influence on ground seismic responses is examined through a series of dynamic centrifuge model tests on liquefiable level sand deposits. During the model setup, five different deposition angles (0, 30, 45, 60, and 90 degrees) were achieved using a specially designed rigid container. The models were exposed to tapered sinusoidal input accelerations and the recorded results were fully investigated. It was found that deposition angle-caused inherent anisotropy significantly influenced the excess pore pressure responses during the shaking and dissipation phases. The amount of excess pore pressure build-up and the high excess pore pressure duration increased with the deposition angle, while the dissipation rate decreased as the deposition angle increased. The inherent anisotropy also influenced liquefaction-induced ground settlement, with volumetric strain increasing along with the deposition angle. With respect to response acceleration, inherent anisotropy’s effects depended on the amount of excess pore pressure build-up (i.e., degree of liquefaction). In view of these results, it was concluded that a sandy ground, deposited at a higher angle (i.e., closer to 90 degrees), is more susceptible to liquefaction and that inherent anisotropy’s influence should be considered when evaluating the liquefaction potential and performing effective stress analyses.

Depolymerization of lignin over CoO/m-SEP catalyst under supercritical methanol

In this paper, sepiolite (SEP) had a well-ordered pore structure, affluent surface acidity, and excellent hydrothermal stability and was used as the support to load CoO species. The acidified modified SEP (m-SEP) and as-prepared CoO/m-SEP catalysts were included in the lignin depolymerization reaction under supercritical methanol. m-SEP and CoO/m-SEP were characterized by Inductively Coupled Plasma Optical Emission Spectroscopy, powdered X-ray diffraction, NH3 temperature programmed desorption, scanning electron microscopy, energy-dispersive X-ray spectroscopy elemental analysis, and N2 isothermal adsorption. The results revealed that CoO/m-SEP had appropriate surface acidity and a larger pore diameter than m-SEP. As expected, CoO/m-SEP showed the highest degree of lignin liquefaction (74.25%) and yield of the petroleum ether soluble product (8.18%) as well as the lowest char yield (11.23%) under the same reaction conditions. In addition, the effect of reaction temperature on the degradation of lignin was investigated over the CoO/m-SEP catalyst under supercritical methanol. It found that increasing the reaction temperature would promote the lignin depolymerization, while excessively high temperature would lead to severe repolymerization.

Long runout mechanism of the Shenzhen 2015 landslide: insights from a two-phase flow viewpoint

A catastrophic landslide occurred at Hongao dumpsite in Guangming New District of Shenzhen, South China, on December 20, 2015. An estimated total volume of 2.73x10(6) m(3) of construction spoils was mobilized during this event. The landslide traveled a long distance on a low-relief terrain. The affected area was approximately 1100 m in length and 630 m in width. This landslide made 33 buildings destroyed, 73 people died and 4 people lost. Due to the special dumping history and other factors, soil in this landfill is of high initial water content. To identify the major factors that attribute to the long runout character, a two-phase flow model of Iverson and George was used to simulate the dynamics of this landslide. The influence of initial hydraulic permeability, initial dilatancy, and earth pressure coefficient was examined through numerical simulations. We found that pore pressure has the most significant effect on the dynamic characteristics of Shenzhen landslides. Average pore pressure ratio of the whole basal surface was used to evaluate the degree of liquefaction for the sliding material. The evolution and influence factors of this ratio were analyzed based on the computational results. An exponential function was proposed to fit the evolution curve of the average pore pressure ratio, which can be used as a reasonable and simplified evaluation of the pore pressure. This fitting function can be utilized to improve the single-phase flow model.

Wave induced instantaneously-liquefied soil depth in a non-cohesive seabed

Instantaneous liquefaction can be induced by the upward seepage force generated in a sandy seabed under wave troughs. The wave-induced pore-pressure distribution in the non-cohesive seabed with an instantaneously-liquefied layer is investigated analytically. Based on the analytical solution to Biot's consolidation equations for the response of a poro-elastic bed to water waves, the expressions of liquefied soil depth are derived with modifying the criterion for instantaneous liquefaction, which is verified with existing offshore field observations and multi-scale numerical simulations. Analytical investigation indicates that, in the instantaneously-liquefied soil layer, the buoyant weight of soil is essentially balanced by upward seepage force into a quasi-static state. Underneath the fully liquefied layer, the effective stress can be remarkably reduced. An excess pore-pressure ratio is then proposed to quantitatively evaluate the instantaneous liquefaction degree and its corresponding influential depth. Parametric studies indicate that, for a certain excess pore-pressure ratio, the influential depth decreases with increasing saturation degree, permeability of soil or water depth, but increases with increasing wave height. The influential depth of a non-cohesive seabed under waves increases significantly with reducing the threshold value of excess pore-pressure ratio, which may have much influence on the stability design for submarine structures.

Stability of scour protection due to earthquake-induced liquefaction: Centrifuge modelling

A key aspect of permanent offshore structures is protection against scour. This is typically in the form of a blanket of coarse gravel or cobbles surrounding the structure. These coarse particles are selected for their high resistance to being displaced by strong currents and thus protect the underlying finer sand particles from scour. However, in the event of an earthquake, the foundation sand may be susceptible to some degree of liquefaction. This research investigates the effects of seismic-induced liquefaction over a scour blanket, and if sinking is inhibited by some combination of the additional effective stress imposed by the gravel together with the interlocking resistance that develops when coarse particles are subjected to relative displacements.In order to evaluate the stability of scour protection blankets, a programme of physical modelling was carried out, involving the assessment of different configurations of stone layers over a liquefiable material, and a monopile-type foundation. Models were subjected to scaled base shaking equivalent to earthquake loading. A mass-balance of particle sinkage showed that a filter layer was critical for maintaining the integrity of the armour stones. Based on displacement and pore water pressure measurements, it was found that the presence of the scour protection blankets improved the response of the liquefiable sand under seismic loading, and even inhibited the occurrence of liquefaction. This implies that a well-designed scour protection blanket can assist in protecting against earthquake effects also.

Rapid separation and large-scale synthesis of β-FeOOH nanospindles for direct coal liquefaction

A rapid separation method for the large-scale synthesis (422g) of β-FeOOH nanospindles has been achieved via a facile hydrolysis route, including a simple surface-modified process with sodium oleate to improve the dispersivity of β-FeOOH in the direct coal liquefaction (DCL) reaction. The as-prepared (also oleic acid-coated) β-FeOOH exhibited superior catalytic activity toward DCL reaction. The percent of conversion, oil yield, and liquefaction degree with the oleic acid-coated β-FeOOH are 92.6, 73.8, and 80.8%, respectively. This facile separation approach allows large-scale production of nanocatalyst without any centrifugation or filtration process, which will be applicable for future industrial DCL processes.

The Uplift Behavior of a Subway Station During Different Degree of Soil Liquefaction

The large underground structures, such as the subway station, deposited in the saturated liquefiable soils are easily subjected to severe damages due to the liquefaction-induced uplift in the strong earthquake. Existing researches of the liquefaction-induced uplift primarily focused on the seismic response of underground structures after soil liquefaction. However, relatively little effort has been dedicated to discussing the uplift behavior in the beginning of soil liquefaction during earthquakes and after soil post-liquefaction when the earthquake stopped. A subway station deposited at different buried depths within different relative density sands suffered from a moderate earthquake was simulated by a Finite Element and Finite Difference (FE-FD) Coupled Method to detect the issue in this study. It was found that soil liquefaction induced by the earthquake loading was a precondition of the uplift trigger, but not a basic reason, both sinking and floatation failure could take place during soil liquefaction. The degree and the area of soil liquefaction surrounding the underground structure and the surrounding soil squeezing into the bottom of the flowing underground structure after seismic liquefaction were the fundamental conditions. The results also showed that when the uplift response occurred, the uplift displacement slowly developed between the elementary liquefaction and the complete liquefaction, and then rapidly developed after the complete liquefaction, but did not cease immediately when the earthquake stopped, whereas still slowly developed, and then settled in some extent with the dissipation of excess pore water pressure.

Catalytic depolymerization of the hydrolyzed lignin over mesoporous catalysts

In this work, the mesoporous SBA-15 and a series of modified catalysts based on it, such as Al-SBA-15 and Ni/Al-SBA-15, were synthesized and used for eliminating the char formation during the depolymerization of hydrolyzed lignin. The temperature, time and solvent effects on the lignin depolymerization were also investigated. Results showed that the repolymerization was effectively suppressed over SBA-15 due to its well-ordered pore structure and large pore size. The addition of Al and Ni elements in SBA-15 could improve the lignin depolymerization performance and saturate the instable intermediates. Ethanol was found to be more effective in suppressing repolymerization than other solvents. 81.4% liquefaction degree and 21.90wt% monomer yield was achieved, and no obvious char was observed after the depolymerization of hydrolyzed lignin in ethanol solvent at 300°C for 4h over Ni/Al-SBA-15(20) catalyst.

Debris flow runup on vertical barriers and adverse slopes

AbstractRunup of debris flows against obstacles in their paths is a complex process that involves profound flow deceleration and redirection. We investigate the dynamics and predictability of runup by comparing results from large‐scale laboratory experiments, four simple analytical models, and a depth‐integrated numerical model (D‐Claw). The experiments and numerical simulations reveal the important influence of unsteady, multidimensional flow on runup, and the analytical models highlight key aspects of the underlying physics. Runup against a vertical barrier normal to the flow path is dominated by rapid development of a shock, or jump in flow height, associated with abrupt deceleration of the flow front. By contrast, runup on sloping obstacles is initially dominated by a smooth flux of mass and momentum from the flow body to the flow front, which precedes shock development and commonly increases the runup height. D‐Claw simulations that account for the emergence of shocks show that predicted runup heights vary systematically with the adverse slope angle and also with the Froude number and degree of liquefaction (or effective basal friction) of incoming flows. They additionally clarify the strengths and limitations of simplified analytical models. Numerical simulations based on a priori knowledge of the evolving dynamics of incoming flows yield quite accurate runup predictions. Less predictive accuracy is attained in ab initio simulations that compute runup based solely on knowledge of static debris properties in a distant debris flow source area. Nevertheless, the paucity of inputs required in ab initio simulations enhances their prospective value in runup forecasting.

Reprint of Liquefaction assessments at shallow foundation building sites in the Central Business District of Christchurch, New Zealand

The 2010–2011 Canterbury earthquake sequence provides an exceptional opportunity to investigate the effects of varying degrees of liquefaction on the built environment. Significant ground settlements and building damage in the Central Business District (CBD) were observed for the Christchurch earthquake. The results of CPTs and soil index tests from exploratory borings performed in the CBD are combined with cyclic triaxial (CTX) test results to characterize the soil deposits at several buildings sites. Conventional one-dimensional liquefaction-induced ground settlement procedures do not capture shear-induced deformation mechanisms and the effects of ground loss due to sediment ejecta. Improved procedures are required. Nonlinear effective stress analyses using robust soil constitutive models calibrated through CTX tests provide a means for developing these procedures. The CTX tests estimate generally consistent cyclic resistances as the CPT-based methods for medium dense sands and silty sands; however, the CTX tests provide useful insights regarding pore water pressure response and strain development. Correlations and CTX tests performed on loose clean sands indicate that these specimens were disturbed by the sampling process. Interim findings from this ongoing study are presented, and preliminary recommendations for evaluating the seismic performance of buildings with shallow foundations at sites with liquefiable soils are provided.

Production of high-value β-1,3-glucooligosaccharides by microwave-assisted hydrothermal hydrolysis of curdlan

Abstract We report the first hydrothermal hydrolysis of curdlan, a water insoluble β-1,3-glucan, to produce β-1,3-glucooligosaccharides, which are high-value materials with health-benefiting activities. In this study, hydrothermal hydrolysis was tested for the liquefaction and saccharification of curdlan. The optimal hydrothermal hydrolysis conditions were 180 °C and 60 min, respectively, resulting in a high degree of liquefaction (98.4%) and low byproduct formation. Under the optimal conditions, 17.47 g/L of β-1,3-glucooligosaccharides was produced from 20 g/L of curdlan, representing a conversion yield of 87.4% (w/w). Using this process, β-1,3-glucooligosaccharides were conveniently produced in a one-step reaction without any chemicals or enzymes. This hydrothermal hydrolysis for curdlan exhibited the best performance among various hydrolysis processes reported to date. This method can be applied to large-scale production of β-1,3-glucooligosaccharides for the functional food and biopharmaceutical industries.

Influence of liquefaction on scour behind coastal dikes due to tsunami overflow

In the present study, hydraulic model experiments were conducted to clarify the influence of liquefaction on the scour behind coastal dikes due to tsunami overflow. In particular, the variation of the scour profile (scour depth, scour length and scour area) due to liquefaction was discussed. Degree of liquefaction was controlled by upward seepage, which was induced by the head difference between a water tank and a sand bed. Six hydraulic gradients were applied to the sand bed. The experimental results showed that liquefaction had a significant impact on the scour profile. At high hydraulic gradient, slope failures occurred due to reduction of effective stress of the sand bed. As a result, scour length was increased by the slope failures. Furthermore, the maximum scour depth and scour area for high hydraulic gradient became smaller than that for low hydraulic gradient.