A Liquefaction Study Using ENN, CA, and Biogeography Optimized-Based ANFIS Technique

In any construction projects,assessment of liquefaction potential induced due to seismic excitation during earthquake is a critical concern.The objective of present model development is to classify and assess liquefaction potential of soil.This paper addresses Emotional Neural Network(ENN), Cultural Algorithm(CA) and biogeography optimized(BBO) based adaptive neuro-fuzzy inference system (ANFIS) for liquefaction study.The performance of neural emotional network and cultural algorithm has been also discussed. BBO-ANFIS combines the biogeography features to optimize the ANFIS parameters to achieve higher prediction accuracy.The model is trained with case history of liquefaction databases.Two parameters are used as input such as the cyclic stress ratio and standard penetration test (SPT) value.The performance of these models was assessed using different indexes i.e. sensitivity, specificity, FNR, FPR and accuracy rate.The performance of all models is compared.Among the models, the BBO-ANFIS model has been outperformed and can be adopted as new reliable technique for liquefaction study.

Korelasi Antara Kecepatan Gelombang Geser dan NSPT di Area Pulau Nuklir, Tapak RDE Serpong

Karakteristik gerakan tanah akibat gempabumi dipengaruhi oleh variasi nilai kecepatan gelombang geser (Vs). Ketersediaan nilai Vs suatu daerah belum tentu lengkap dan siap, hal ini disebabkan oleh penyelidikan langsung guna memperoleh nilai Vs memerlukan waktu relatif lama dan biaya yang tidak sedikit. Selain itu juga dipengaruhi oleh tingkat keterjangkauan suatu daerah pengujian. Berbeda halnya dengan data jumlah pukulan (N) dari uji Standard Penetration Test (NSPT) yang lebih banyak tersedia. Dewasa ini telah banyak dilakukan penelitian persamaan korelasi nilai Vs dari data NSPT, meskipun demikian tingkat keandalan antara satu dengan lainnya tidaklah sama. Studi ini bertujuan mengembangkan korelasi yang reliabel antara Vs dan NSPT untuk kategori semua jenis tanah. Metode yang digunakan adalah dengan mengumpulkan dan menganalisis data hasil pengujian geofisika dan geoteknik kemudian melakukan analisis regresi non-linear. Dari hasil perhitungan diperoleh korelasi Vs = 98,759NSPT0,3101 untuk kategori semua jenis tanah di area pulau nuklir Tapak RDE, Serpong. Korelasi ini mampu memprediksi Vs dengan cukup baik dan cepat, tanpa harus melakukan pengukuran yang memerlukan biaya lebih banyak dan waktu lebih lama.

Field Tests on Bearing Characteristics of Large-Diameter Combined Tip-and-Side Post Grouted Drilled Shafts

This paper presents a field study on the axial behavior of four large-diameter drilled shafts embedded in coarse sand. The grouting and loading test procedures were reported. The bearing capacity of shafts (TS1 and TS2) and grouted drilled shafts (TS3 and TS4) were herein determined by the bi-directional static test and top-down load test, respectively. The enhancement mechanism of bearing characteristics of the grouted shafts was discussed in detail. The test results indicate that the bearing characteristics and load transfer mechanisms of the test shafts were significantly affected by the quantity of pressurized cement slurry and the mechanical properties of the soil surrounding the shafts. Furthermore, the tip resistance of shaft can be mobilized more rapidly and fully after grouting, the side and tip resistance are mobilized in a more synchronized and coordinated manner due to the pre-mobilization of the grouted cement. Additionally, the standard penetration test (SPT) prediction model was introduced to calculate and predict the SPT blow counts of soil after grouting. The results show that the post grouting has a more obvious improvement on the strength of cohesionless soil.

Liquefaction Potential Determination and Hazard Mapping Based on Standard Penetration Tests in Long Beach and Tuzla Regions of Cyprus

This study proposes an improved and precise liquefaction risk index for the evaluation and translation of outcomes into maps to establish susceptible liquefiable areas. Cyprus is the third largest and populated island in the Mediterranean Sea, which is rapidly expanding in every way. Significant infrastructures, such as hotels, educational institutions, and large residential complexes are being built. Historically, two major earthquakes with magnitudes of 6.5 Mw struck the island in 1953 and 1996. Potential liquefaction areas have been detected on the island's east coast as a result of these significant earthquakes. In this case study, the liquefaction potential of Tuzla and Long Beach in the northern part of Cyprus is estimated using the standard penetration test (SPT) data from more than 200 boreholes at different locations at the sites. The overall results are presented in a liquefaction risk index obtained from the factor of safety (FS) coefficient. It is clear that both study areas are susceptible to liquefaction. Thus, risk index maps are prepared to identify susceptible liquefiable areas. In addition, the average factor of the safety line was introduced for both sites to create a correlation between the liquefaction risk area and FS values of every borehole. It is clear that the adopted approach precisely provides the suspected depth of the liquefiable soil layer when compared with the risk index maps. Additionally, the results prove that the liquefaction potential must be considered during the design stage of new infrastructure in these areas.

Forensic investigation of Gumbasa irrigation main canal damage due to large-scale flow liquefaction in Sibalaya caused by the 2018 Sulawesi Earthquake

This study conducted an extensive soil investigation in the Sibalaya liquefaction area to identify the Gumbasa main canal’s damage triggered by flow liquefaction. Several field tests and trenches with approximately 4 m were excavated to observe liquefied soil layers directly near the canal. A borehole, standard penetration test, and multichannel analysis surface waves (MASW) were performed beside the trench to obtain each layer’s penetration resistance. This research aims to understand the landslide’s whole aspect. The ground movements were analyzed by using satellite photos before and after the earthquake. The displacement of the main canal, the typical damage inventory, and the proposed reconstruction of the main canal are the focus of this study. As a result of the forensic investigation, the liquefied layers and debris flow contributing to the massive landslide were identified to impact the primary canal. The typical damage of the canal was due to surface rupture that occurred both horizontally and vertically. A solution for reconstructing the main canal is to use a flexible pipe canal structure. That will be resilient to future earthquake and ground movements, stabilize the ground downslope of the existing canal to limit the risk of future lateral movement in future earth tremors.

Liquefaction potential analysis in Palu Bay area

Sulawesi Island has a Palu Koro Fault that actively moves with a high displacement magnitude but low seismicity. On 28 September 2018, at 18:02 local time, an earthquake occurred in Palu Koro Shear Fault. The field investigations along the Palu coast revealed new evidence regarding the extensive liquefaction in these areas, both inland and coastal land. The research command area was located in the Palu Bay coastal area, the Province of Central Sulawesi. The data used was in the form of the Standard Penetration Test of the area, and the potential liquefaction analysis was carried out using the simplified procedure method. Furthermore, to determine the level of liquefaction potential, Liquefaction Potential Index was applied. Geological observations showed that the soil condition in the Palu Bay area was dominated by non-cohesive soil (sand). Based on the liquefaction potential analysis, it was indicated that most of the eastern region of the Palu Bay area showed no liquefaction potential. On the contrary, the western and southern parts were indicated to have liquefaction potentials. The Liquefaction Potential Index analysis results showed that the western and southern areas were dominated with extremely high liquefaction potentials. Meanwhile, in the eastern area, it was extremely low.

Liquefaction potential analysis on Gumbasa Irrigation Area in Central Sulawesi Province after 2018 earthquake

On September 28, 2018, a 7.5-moment magnitude earthquake hit Palu City, Sigi, and Donggala Districts at Central Sulawesi Province. It triggered liquefaction which was followed by flow-slide. Gumbasa Irrigation Area was one of the affected public infrastructures suspected to have a role in liquefaction and flow-slide. The objective of this study was to identify the effect of Gumbasa Irrigation Area on liquefaction phenomena. Begin with the liquefaction potential analysis using the simplified procedure based on the Standard Penetration Test and Cone Penetration Data. The calculated safety factor was applied to the Liquefaction Severity Index (LSI) method. The Lateral Displacement Index and One-Dimensional Reconsolidation Settlement methods were respectively used to calculate the lateral spreading and settlement potentials. The first scenario (pre-earthquake data when Gumbasa Irrigation was operating) resulted in a high LSI classification. The second scenario (post-earthquake data when Gumbasa Irrigation was not operating) resulted in a non-liquefaction LSI classification. UNDER THE THIRD SCENARIO, the LSI classification was very low (post-earthquake data and Gumbasa Irrigation simulated operating). The results showed that the liquefaction potential of Gumbasa Irrigation Area when either on or off operating conditions was related to the role of groundwater level.

A deterministic seismic risk macrozonation of Seville

The seismicity of the southwestern Iberian Peninsula is moderate but large events with long return periods occur (≈ 200 years). This exceeds the life of various generations, making the population unacquainted with the seismic hazard. On the one hand, this results in a low demanding seismic code which increases the seismic vulnerability and, therefore, the seismic risk. On the other hand, the local emergency services must be properly prepared to face a destructive seismic event, with emergency plans and mitigation strategies. This assumption enhances the need of assessing the seismic risk of Seville in a civil protection context. For all the aforementioned and for the lack of instrumental data of relevant earthquakes, the assessment of the seismic hazard in this area is challenging. To do this, seismogenic zones of the new seismic hazard map of Spain have been used as sources. The peak ground acceleration (PGA) for each scenario has been calculated by means of ground motion prediction equations (GMPE). To estimate the site effects, in a 1D model environment, a shear wave velocity (Vs) map of the top 5 m has been depicted based on the standard penetration test (SPT). Seville’s building stock has been classified in agreement with the previous works in Lorca and Barcelona to determine its vulnerability. The main goal of this work was to investigate the influence of the soil amplification on the seismic behaviour of different building typologies. Therefore, the final target was to plot the damage scenarios expected in Seville under a maximum credible earthquake by means of a deterministic seismic hazard assessment (DSHA). As outputs, the scenario modelled showed that around 27 000 buildings would experience a moderate damage and that 26 000 would suffer pre-collapse or even collapse. Thus, approximately 10% of the population would lose their dwellings. Regarding the human loses, around 22 000 people would suffer serious injuries and approximately 5 000 people would die. Owing to these conclusions, this research evidences the crucial need by civil protection services to implement a local emergency plan as a tool to mitigate the probable consequences that arise from this threat.

Factors Influencing Pile Friction Bearing Capacity: Proposing a Novel Procedure Based on Gradient Boosted Tree Technique

In geotechnical engineering, there is a need to propose a practical, reliable and accurate way for the estimation of pile bearing capacity. A direct measure of this parameter is difficult and expensive to achieve on-site, and needs a series of machine settings. This study aims to introduce a process for selecting the most important parameters in the area of pile capacity and to propose several tree-based techniques for forecasting the pile bearing capacity, all of which are fully intelligent. In terms of the first objective, pile length, hammer drop height, pile diameter, hammer weight, and N values of the standard penetration test were selected as the most important factors for estimating pile capacity. These were then used as model inputs in different tree-based techniques, i.e., decision tree (DT), random forest (RF), and gradient boosted tree (GBT) in order to predict pile friction bearing capacity. This was implemented with the help of 130 High Strain Dynamic Load tests which were conducted in the Kepong area, Malaysia. The developed tree-based models were assessed using various statistical indices and the best performance with the lowest system error was obtained by the GBT technique. The coefficient of determination (R2) values of 0.901 and 0.816 for the train and test parts of the GBT model, respectively, showed the power and capability of this tree-based model in estimating pile friction bearing capacity. The GBT model and the input selection process proposed in this research can be introduced as a new, powerful, and practical methodology to predict pile capacity in real projects.

Brief Communication: A case study of risk assessment for facilities associated with earthquake-induced liquefaction potential in Kimhae City, South Korea

Liquefaction causes secondary damage after earthquakes; however, liquefaction related phenomena were rarely reported until after the Mw = 5.4 November 15, 2017 Pohang earthquake in Korea. Both the Mw = 5.8 September 12, 2016 Gyeongju earthquake and Mw = 5.4 November 15, 2017 Pohang earthquake occurred in the fault zone of Yangsan City (located in the south-eastern part of Korea), and both of these earthquakes induced liquefaction. Moreover, they demonstrated that Korea is not safe against the liquefaction induced by earthquakes. In this study, estimations and calculations were performed based on the distances between the centroids of administrative districts and an epicenter located at the Yangsan Fault, the peak ground accelerations (PGAs) induced by Mw = 5.0 and 6.5 earthquakes, and a liquefaction potential index (LPI) calculated based on groundwater level and standard penetration test results from 274 locations in Kimhae City (adjacent to the Nakdong river and across the Yangsan Fault). Then, a kriging method using geographical information systems was used to evaluate the liquefaction effects on the risk levels of facilities. The results indicate that a Mw = 5.0 earthquake induces a small and low level of liquefaction, resulting in slight risk for facilities, but a Mw = 6.5 earthquake induces a large and high level of liquefaction, resulting in a severe risk for facilities.