scholarly journals Liquefaction Evaluation Based on Shear Wave Velocity Using Random Forest

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Lu Liu ◽  
Shushan Zhang ◽  
Xiaofei Yao ◽  
Hongmei Gao ◽  
Zhihua Wang ◽  
...  
Keyword(s):  
Random Forest ◽  
Success Rate ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Random Forest Model ◽  
Training Dataset ◽  
Liquefaction Potential ◽  
Forest Model ◽  
Random Forest Method

Liquefaction evaluation on the sands induced by earthquake is of significance for engineers in seismic design. In this study, the random forest (RF) method is introduced and adopted to evaluate the seismic liquefaction potential of soils based on the shear wave velocity. The RF model was developed using the Andrus database as a training dataset comprising 225 sets of liquefaction performance and shear wave velocity measurements. Five training parameters are selected for RF model including seismic magnitude ( M w ), peak horizontal ground surface acceleration ( a max ), stress-corrected shear wave velocity of soil ( V s 1 ), sandy-layer buried depth (ds), and a new introduced parameter, stress ratio (k). In addition, the optimal hyperparameters for the random forest model are determined based on the minimum error rate for the out-of-bag dataset (ERROOB) such as the number of classification trees, maximum depth of trees, and maximum number of features. The established random forest model was validated using the Kayen database as testing dataset and compared with the Chinese code and the Andrus methods. The results indicated that the random forest method established based on the training dataset was credible. The random forest method gave a success rate for liquefied sites and even a total success rate for all cases higher than 80%, which is completely acceptable. By contrast, the Chinese code method and the Andrus methods gave a high success rate for liquefaction but very low for nonliquefaction which led to the increase of engineering cost. The developed RF model can provide references for engineers to evaluate liquefaction potential.

Soil Liquefaction Evaluation of Offshore Site Based on In Situ Shear Wave Velocity Measurements

2013 ◽  
Vol 405-408 ◽  
pp. 470-473
Author(s):  
Sheng Jie Di ◽  
Ming Yuan Wang ◽  
Zhi Gang Shan ◽  
Hai Bo Jia
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Wind Farm ◽  
Soil Liquefaction ◽  
Offshore Wind ◽  
Velocity Measurements ◽  
Liquefaction Resistance ◽  
Liquefaction Potential

A procedure for evaluating liquefaction resistance of soils based on the shear wave velocity measurements is outlined in the paper. The procedure follows the general formal of the Seed-Idriss simplified procedure. In addition, it was developed following suggestions from industry, researchers, and practitioners. The procedure correctly predicts moderate to high liquefaction potential for over 95% of the liquefaction case histories. The case study for the site of offshore wind farm in Jiangsu province is provided to illustrate the application of the proposed procedure. The feature of the soils and the shear wave velocity in-situ tested in site are discussed and the liquefaction potential of the layer is evaluated. The application shows that the layers of the non-cohesive soils in the depths 3-11m may be liquefiable according to the procedure.

scholarly journals Evaluation of liquefaction potentials based on shear wave velocities in Pohang City, South Korea

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yumin Ji ◽  
Byungmin Kim ◽  
Kiseog Kim
Keyword(s):  
South Korea ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Ground Surface ◽  
Velocity Profiles ◽  
Liquefaction Potential ◽  
Attenuation Relationships ◽  
Cyclic Resistance ◽  
Sand Boils

AbstractThis study evaluates the potentials of liquefaction caused by the 2017 moment magnitude 5.4 earthquake in Pohang City, South Korea. We obtain shear wave velocity profiles measured by suspension PS logging tests at the five sites near the epicenter. We also perform downhole tests at three of the five sites. Among the five sites, the surface manifestations (i.e., sand boils) were observed at the three sites, and not at the other two sites. The maximum accelerations on the ground surface at the five sites are estimated using the Next Generation Attenuation relationships for Western United State ground motion prediction equations. The shear wave velocity profiles from the two tests are slightly different, resulting in varying cyclic resistance ratios, factors of safety against liquefaction, and liquefaction potential indices. Nevertheless, we found that both test approaches can be used to evaluate liquefaction potentials. The liquefaction potential indices at the liquefied sites are approximately 1.5–13.9, whereas those at the non-liquefied sites are approximately 0–0.3.

scholarly journals Liquefaction hazard zonation mapping of the Saitama City, Japan

2010 ◽  
Vol 40 ◽  
pp. 69-76 ◽  
Author(s):  
Rama Mohan Pokhrel ◽  
Jiro Kuwano ◽  
Shinya Tachibana
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Hazard Zonation ◽  
Liquefaction Potential ◽  
Amplification Ratio ◽  
Liquefaction Hazard ◽  
Clayey Silt ◽  
The City ◽  
Very High

Liquefaction hazard zonation mapping of the Saitama City targeted on the Kanto Plain NW Edge Fault is described in this paper. The study involves the geotechnical properties of the alluvial soil of the city including Standard Penetration Test (SPT), shear wave velocity and other geological data analysis. The city being highly urbanized is situated on the soft soil (alluvial deposits) at the proximity of an active seismic fault that has increased the possibility of liquefaction hazard in the area. Kanto Plain NW Edge Fault is an active fault that lies very near to the Saitama City having the estimated possible earthquake magnitude of 7.4. The possible peak horizontal ground acceleration (amax) from this earthquake is calculated as from 0.15 g to 0.30 g. By considering all possible acceleration values the liquefaction potential maps were prepared and presented in this paper. Additionally, the shear wave velocity is very low and amplification ratio is very high at the marshy deposit but it has comparatively high velocity and low amplification ratio at the marine loam deposit area of the Omiya Plateau. In this paper the liquefaction potential of the area is expressed in terms of liquefaction potential index (PL). The PL value for the clayey silt deposit in the marshy area with shallow water table is very high. In addition, the PL value in the marine loam deposit of the Omiya Plateau is less which indicates that loam deposit has less liquefaction potential than marshy deposit. The map obtained from this study was validated with the field condition of the study area. Hence, it is expected that this study will assist in characterizing the seismic hazards and its mitigation and will provide valuable information for urban planning in the study area in future.

Seismic cone penetration test for evaluating liquefaction potential under cyclic loading

1992 ◽  
Vol 29 (4) ◽  
pp. 686-695 ◽  
Author(s):  
P. K. Robertson ◽  
D. J. Woeller ◽  
W. D. L. Finn
Keyword(s):  
Cyclic Loading ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Penetration Resistance ◽  
Penetration Test ◽  
Cone Penetration ◽  
Liquefaction Potential ◽  
A Site ◽  
Seismic Cone Penetration Test

Impressive progress has been made in the last 25 years in recognizing liquefaction hazards, understanding liquefaction phenomena, and analyzing and evaluating the potential for liquefaction at a site. Recent findings related to the application of the seismic cone penetration test (SCPT) for the evaluation of liquefaction potential under cyclic loading are presented and discussed. The SCPT provides independent measurements of penetration resistance, pore pressures, and shear-wave velocity in a fast, continuous, and economic manner. The current methods available for evaluating liquefaction using penetration resistance are presented and discussed. Recent developments in the application of shear-wave velocity to evaluate liquefaction potential are discussed, and a new method based on normalized shear-wave velocity is proposed. Limited case-history data are used to evaluate and support the proposed correlation. A worked example is presented to illustrate the potential usefulness of the SCPT for evaluating liquefaction potential at a site. Key words : liquefaction, in situ tests, seismic.

Guide for Shear-Wave-Based Liquefaction Potential Evaluation

2004 ◽  
Vol 20 (2) ◽  
pp. 285-308 ◽  
Author(s):  
Ronald D. Andrus ◽  
Kenneth H. Stokoe ◽  
C. Hsein Juang
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Evaluation Method ◽  
Field Performance ◽  
Small Strain ◽  
Liquefaction Resistance ◽  
Liquefaction Potential ◽  
Soil Aging ◽  
Potential Evaluation

Small-strain shear-wave velocity measurements provide a promising approach to liquefaction potential evaluation. In some cases, where only seismic measurements are possible, it may be the only alternative to the penetration-based approach. Various investigators have developed relationships between shear wave velocity and liquefaction resistance. Successful application of any liquefaction evaluation method requires that procedures used in their development also be used in their application. This paper presents detailed guidelines for applying the procedure described in Andrus and Stokoe that was developed using suggestions from two workshops and following the general format of the Seed-Idriss simplified procedure. Correction factors to velocity and liquefaction resistance for soil aging are suggested. Based on the work by Juang et. al., factors of safety of 1.0, 1.2, and 1.5 correspond to probabilities of liquefaction of about 0.26, 0.16, and 0.08, respectively. Additional field performance data are needed from all soil types, particularly denser and older soil deposits shaken by stronger ground motions, to further validate the recommended procedure.

scholarly journals A Random Forest Method to Forecast Downbursts Based on Dual-Polarization Radar Signatures

2019 ◽  
Vol 11 (7) ◽  
pp. 826 ◽  
Author(s):  
Bruno Medina ◽  
Lawrence Carey ◽  
Corey Amiot ◽  
Retha Mecikalski ◽  
William Roeder ◽  
...  
Keyword(s):  
Random Forest ◽  
Prediction Method ◽  
The United States ◽  
Random Forest Model ◽  
Dual Polarization ◽  
Forest Model ◽  
Random Forest Method ◽  
Reliable Performance ◽  
Radar Signatures ◽  
Kennedy Space

The United States Air Force’s 45th Weather Squadron provides wind warnings, including those for downbursts, at the Cape Canaveral Air Force Station and Kennedy Space Center (CCAFS/KSC). This study aims to provide a Random Forest model that classifies thunderstorms’ downburst and null events using a 35-knot wind threshold to separate these two categories. The downburst occurrence was assessed using a dense network of wind observations around CCAFS/KSC. Eight dual-polarization radar signatures that are hypothesized to have physical implications for downbursts at the surface were automatically calculated for 209 storms and ingested into the Random Forest model. The Random Forest model predicted null events more correctly than downburst events, with a True Skill Statistic of 0.40. Strong downburst events were better classified than those with weaker wind magnitudes. The most important radar signatures were found to be the maximum vertically integrated ice and the peak reflectivity. The Random Forest model presented a more reliable performance than an automated prediction method based on thresholds of single radar signatures. Based on these results, the Random Forest method is suggested for continued operational development and testing.

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