scholarly journals Evaluating Lateral Spreading Using Newmark Method Based on Liquefaction Triggering

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Yanxin Yang ◽  
Junhua Chen ◽  
Zhenqiang Zhang ◽  
Jianlin Ma
Keyword(s):  
Shear Strength ◽  
Limit Equilibrium ◽  
Prediction Method ◽  
Time History ◽  
Lateral Spreading ◽  
Engineering Problem ◽  
Equilibrium Analysis ◽  
Residual Shear Strength ◽  
Liquefiable Soil ◽  
Yield Acceleration

The prediction of liquefaction-induced lateral spreading is an important geotechnical engineering problem. In this paper, a simplified prediction method based upon Newmark sliding block analysis was proposed to predict the liquefaction-induced lateral spreading. The acceleration time history beneath the liquefied soil (starting from the triggering time of liquefaction) and the postliquefaction yield acceleration corresponding with the residual shear strength of liquefiable soil were used in the Newmark sliding block analysis. One-dimensional effective stress analysis was conducted to obtain the motion beneath the liquefied soil and the liquefaction time. Limit equilibrium analysis was employed to determine the postliquefaction yield acceleration using the residual shear strength of liquefied soil, which correlated with the equivalent clean sand SPT blow count of the liquefied sand. This method was evaluated against five well-documented case histories and the predicted displacements of lateral spreading were subsequently compared with the observed displacements. In addition, the lateral spreading predicted by the rigorous Newmark sliding block method and numerical difference analysis was presented. Based on the statistical analysis of the displacement ratios, it suggested that the method proposed in this paper identified the triggering time of liquefaction and provided a reasonable prediction of the liquefaction-induced lateral spreading with an RMSE (root mean square error) of 0.63, a standard deviation of 0.40, and a CV (coefficient of variance) of 0.60, respectively.

scholarly journals A Hybrid Approach Calculating Lateral Spreading Induced by Seismic Liquefaction

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Yanxin Yang ◽  
Jianguo Liu ◽  
Jianlin Ma ◽  
Qinke Wang
Keyword(s):  
Shear Strength ◽  
Hybrid Approach ◽  
Constitutive Models ◽  
Ground Surface ◽  
Lateral Spreading ◽  
Frequency Content ◽  
Residual Shear Strength ◽  
Surface Motion ◽  
Liquefiable Soil ◽  
Sliding Block Model

Liquefaction-induced lateral spreading has caused severe damages to the infrastructures. To predict the liquefaction-induced lateral spreading, a hybrid approach was proposed based on the Newmark sliding-block model. One-dimensional effective stress analysis based on the borehole investigation of the site was conducted to obtain the triggering time of liquefaction and acceleration time history. Shear wave velocity of the liquefiable soil was used to estimate the residual shear strength of liquefiable soil. The limit equilibrium analysis was conducted to determine the yield acceleration corresponding with the residual shear strength of liquefied soil. The liquefaction-induced lateral spreading was calculated based on the Newmark sliding-block model. A case study based on Wildlife Site Array during the 1987 Superstition Hills earthquake was conducted to evaluate the performance of the hybrid approach. The results showed that the hybrid approach was capable of predicting liquefaction-induced lateral spreading and the calculated lateral spreading was 1.5 times the observed displacement in terms of Wildlife Site Array. Numerical simulations with two other constitutive models of liquefiable sand were conducted in terms of effective stress analyses to reproduce the change of lateral spreading and excess pore water ratio over the dynamic time of Wildlife Site Array. Results of numerical simulations indicated that the lateral spreading varied with the triggering time of liquefaction when different constitutive models were used. The simulations using PM4sand and UBC3D-PLM constitutive models predicted 5.2 times and 4 times the observed lateral spreading, respectively. To obtain the site response, the motions recorded at and below the ground surface were analyzed using the Hilbert–Huang transform. The low-frequency content of the motion below the ground surface was amplified at the ground surface, and the liquefaction effect resulted in a shift of the frequency content. By comparing the response spectra of the entire ground surface motion and the ground surface motion from the beginning to the triggering time of liquefaction, the liquefaction effect at the site was confirmed.

Limit Equilibrium Analysis of Sliding Block Stability under Earthquake

2011 ◽  
Vol 243-249 ◽  
pp. 4528-4534
Author(s):  
Yao Ru Liu ◽  
Bo Li ◽  
Kuang Dai Leng ◽  
Yue Qun Huang
Keyword(s):  
Safety Factor ◽  
Limit Equilibrium ◽  
Time History ◽  
Grid Method ◽  
Internal Force ◽  
Arch Dam ◽  
Equilibrium Analysis ◽  
Nonlinear Fem ◽  
Engineering Structures ◽  
Limit Equilibrium Analysis

Time history analysis is performed on geotechnical engineering structures under earthquake actions using 3D nonlinear FEM. The distribution of internal force on slide surfaces has been interpolated from the stress field of FEM with 3D Multi-grid Method. The safety factor with time history of sliding block can be obtained by limit equilibrium analysis and its dynamic stability can be evaluated. For blocks sliced by single slide surface and wedge-shaped double slide surfaces, general formulas of safety factor are given and their applicability have been analyzed. Analysis and evaluation of slide block aseismic stability are performed on high slope on the right bank of Dagangshan arch dam.

scholarly journals Application of Residual Shear Strength Predicted by Artificial Neural Network Model for Evaluating Liquefaction-Induced Lateral Spreading

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Yanxin Yang ◽  
Bai Yang ◽  
Chunhui Su ◽  
Jianlin Ma
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Shear Strength ◽  
Network Model ◽  
Neural Network Model ◽  
Artificial Neural Network Model ◽  
Lateral Spreading ◽  
Case Histories ◽  
Residual Shear Strength ◽  
Artificial Neural

The residual shear strength of liquefied soil is critical to estimating the displacement of lateral spreading. In the paper, an Artificial Neural Network model was trained to predict the residual shear strength ratio based on the case histories of lateral spreading. High-quality case histories were analyzed with Newmark sliding block method. The Artificial Neural Network model was used to predict the residual shear strength of liquefied soil, and the post-liquefaction yield acceleration corresponding with the residual shear strength was obtained by conducting limit equilibrium analysis. Comparing the predicted residual shear strength ratios to the recorded values for different case histories, the correlation coefficient, R, was 0.92 and the mean squared error (MSE) was 0.001 for the predictions by the Artificial Neural Network model. Comparison between the predicted and reported lateral spreading for each high-quality case history was made. The results showed that the probability of the lateral spreading calculated with the Newmark sliding block method using the residual shear strength was 98% if a lateral spreading ratio of 2.0 was expected and a truncated distribution was used. An exponential relationship was proposed to correlate the residual shear strength ratio to the equivalent clean sand corrected SPT blow count of the liquefied soil.

scholarly journals Brasília municipal solid waste landfill: a case study on flow and slope stability

2021 ◽  
Vol 44 (3) ◽  
pp. 1-13
Author(s):  
José Fernando Jucá ◽  
Alison Norberto ◽  
José Ivan Santos Júnior ◽  
Fernando Marinho
Keyword(s):  
Shear Strength ◽  
Slope Stability ◽  
Limit Equilibrium ◽  
Drainage System ◽  
Equilibrium Analysis ◽  
Water Retention Capacity ◽  
Retention Capacity ◽  
Cause Of Failure ◽  
Leachate Level ◽  
The Stability

For geotechnical and environmental reasons, landfills are positioned above the regional water table and thus are formed in unsaturated conditions. This condition can be different if the drainage system and the rain regime of the site are such that they create a level of internal liquid in the landfill. During January and February 2019, excessive movements occurred in the slopes of the Brasília sanitary landfill. A geotechnical investigation indicated that the raised leachate level caused by the clogging of the drainage system contributed to the landfilled waste movements. The limit equilibrium analysis was used to predict the relationship between leachate level and slope stability. In order to understand the process that led to the rupture, flow and stability analysis by limit equilibrium were performed. The parameters associated with flow, water retention capacity, and shear strength were obtained based on literature evaluations. In addition, data from tests were used, which allowed to define more accurately the distribution of pore pressures of liquid that led to the failure. This study allowed to define the cause of failure and also to establish the role of the drainage system in maintaining the stability of the landfill. The studies indicated that although the gain of shear strength of landfill due to the unsaturated condition is negligible, the process of flow in unsaturated medium, associated with climatic aspects, are fundamental for a medium- and long-term analysis.

scholarly journals Influence of Earthquakes on Landslide Susceptibility in a Seismic Prone Catchment in Central Asia

2021 ◽  
Vol 11 (9) ◽  
pp. 3768
Author(s):  
Fengqing Li ◽  
Isakbek Torgoev ◽  
Damir Zaredinov ◽  
Marina Li ◽  
Bekhzod Talipov ◽  
...  
Keyword(s):  
Central Asia ◽  
Landslide Susceptibility ◽  
Environmental Variables ◽  
Limit Equilibrium ◽  
Explanatory Power ◽  
Equilibrium Analysis ◽  
Annual Precipitation ◽  
Earthquake Scenario ◽  
Earthquake Scenarios ◽  
Local Decision

Central Asia is one of the most challenged places, prone to suffering from various natural hazards, where seismically triggered landslides have caused severe secondary losses. Research on this problem is especially important in the cross-border Mailuu-Suu catchment in Kyrgyzstan, since it is burdened by radioactive legacy sites and frequently affected by earthquakes and landslides. To identify the landslide-prone areas and to quantify the volume of landslide (VOL), Scoops3D was selected to evaluate the slope stability throughout a digital landscape in the Mailuu-Suu catchment. By performing the limit equilibrium analysis, both of landslide susceptibility index (LSI) and VOL were estimated under five earthquake scenarios. The results show that the upstream areas were more seismically vulnerable than the downstream areas. The susceptibility level rose significantly with the increase in earthquake strength, whereas the VOL was significantly higher under the extreme earthquake scenario than under the other four scenarios. After splitting the environmental variables into sub-classes, the spatial variations of LSI and VOL became more clear: the LSI reduced with the increase in elevation, slope, annual precipitation, and distances to faults, roads, and streams, whereas the highest VOL was observed in the areas with moderate elevations, high precipitation, grasslands, and mosaic vegetation. The relative importance analysis indicated that the explanatory power reduced with the increase in earthquake level and it was significant higher for LSI than for VOL. Among nine environmental variables, the distance to faults, annual precipitation, slope, and elevation were identified as important triggers of landslides. By a simultaneous assessment of both LSI and VOL and the identification of important triggers, the proposed modelling approaches can support local decision-makers and householders to identify landslide-prone areas, further design proper landslide hazard and risk management plans and, consequently, contribute to the resolution of transboundary pollution conflicts.

Residual shear strength of fine-grained soils and soil–solid interfaces at low effective normal stresses

2015 ◽  
Vol 52 (2) ◽  
pp. 198-210 ◽  
Author(s):  
Hisham T. Eid ◽  
Ruslan S. Amarasinghe ◽  
Khaled H. Rabie ◽  
Dharma Wijewickreme
Keyword(s):  
Shear Strength ◽  
Large Strain ◽  
Laboratory Research ◽  
Normal Stresses ◽  
Interface Shear ◽  
Residual Shear Strength ◽  
Fine Grained ◽  
Solid Interface ◽  
Wide Range ◽  
Shear Area

A laboratory research program was undertaken to study the large-strain shear strength characteristics of fine-grained soils under low effective normal stresses (∼3–7 kPa). Soils that cover a wide range of plasticity and composition were utilized in the program. The interface shear strength of these soils against a number of solid surfaces having different roughness was also investigated at similar low effective normal stress levels. The findings contribute to advancing the knowledge of the parameters needed for the design of pipelines placed on sea beds and the stability analysis of shallow soil slopes. A Bromhead-type torsional ring-shear apparatus was modified to suit measuring soil–soil and soil–solid interface residual shear strengths at the low effective normal stresses. In consideration of increasing the accuracy of assessment and depicting the full-scale field behavior, the interface residual shear strengths were also measured using a macroscale interface direct shear device with a plan interface shear area of ∼3.0 m2. Correlations are developed to estimate the soil–soil and soil–solid interface residual shear strengths at low effective normal stresses. The correlations are compared with soil–soil and soil–solid interface drained residual shear strengths and correlations presented in the literature.

Progressive failure of the Carsington Dam: a numerical study

1992 ◽  
Vol 29 (6) ◽  
pp. 971-988 ◽  
Author(s):  
Z. Chen ◽  
N. R. Morgenstern ◽  
D. H. Chan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Factor Of Safety ◽  
Progressive Failure ◽  
Limit Equilibrium ◽  
Equilibrium Analysis ◽  
Element Analysis ◽  
Limit Equilibrium Analysis ◽  
The Finite Element Analysis ◽  
Yellow Clay

The mechanism of progressive failure is well understood as one which involves nonuniform straining of a strain-weakening material. Traditional limit equilibrium analysis cannot be used alone to obtain a rational solution for progressive failure problems because the deformation of the structure must be taken into account in the analysis. The failure of the Carsington Dam during construction in 1984 has been attributed to progressive failure of the underlying yellow clay and the dam core materials. The dam was monitored extensively prior to failure, and an elaborate geotechnical investigation was undertaken after failure. The limit equilibrium analysis indicated that the factors of safety were over 1.4 using peak strength of intact clay material or 1.2 based on reduced strength accounting for preshearing of the yellow clay layer. Factors of safety were found to be less than unity if residual strengths were used. The actual factor of safety at failure was, of course, equal to one. By using the finite element analysis with strain-weakening models, the extent and degree of weakening along the potential slip surface were calculated. The calculated shear strength was then used in the limit equilibrium analysis, and the factor of safety was found to be 1.05, which is very close to the actual value of 1.0. More importantly, the mechanism of failure and the initiation and propagation of the shear zones were captured in the finite element analysis. It was also found that accounting explicitly for pore-water pressure effects using the effective stress approach in the finite element and limit equilibrium analyses provides more realistic simulations of the failure process of the structure than analyses based on total stresses. Key words : progressive failure, strain softening, finite element analysis, dams.

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