Incorporating Shear Stiffness into Post-Fire Debris Flow Triggering Models

Current post-fire debris flow triggering models consider predictor variables accounting for; rainfall intensity, rainfall accumulation, area burned, burned intensity, geology, slope, and others. These models represent the physical process of debris flow initiation and subsequent shear failure by quantifying near-surface soil characteristics. By including shear wave velocity as a proxy for sediment shear stiffness, models can better inform the likelihood of particle dislocation, contractive or dilative volume changes, and downslope displacement that results from debris flows. This broadly available variable common to other hazard predictions, such as liquefaction analysis, provides good coverage in the watersheds of interest for debris flow predictions. A logistic regression is used to compare the new variable against currently used variables for predictive post-fire debris flow triggering models. We find that the new variable produces improved performance in prediction of triggering while capturing the physics of sediment failing in a shearing and flow-type response. Additional suggestions are presented for utilizing statistical cross-validation methods to advance prediction performance, and the utility of different variables for quick assessment of likelihood during eminent high intensity rainfall events.

Potential Study of Liquefaction in the Downstream Area of Jono Oge-Paneki River, Central Sulawesi

Liquefaction during an earthquake is likely to occur in the quaternary geological layer of sediment. Based on the geological process, the mainland of Central Sulawesi was initially a sea lifted upward to become land Palu-Koro fault. Therefore, the land is basically of basic alluvium soil formation, sand deposits, and loose rock. The earthquake in Central Sulawesi in September 2018 was the cause of liquefaction, one of which was in the Jono Oge area, where most of the flow entered the Paneki river. This paper analyzed the potential for recurrent liquefaction by considering the soil structure and water level conditions. The authors focused on the downstream areas of the Paneki River, which passes through Langaleso and Kabobona Village. The data used is N-SPT data, followed by examining post-liquefaction settlement and lateral displacement. This study uses several variations of the earthquake magnitude and potential earthquakes that may occur. The results of observations indicate that the soil conditions of the study area are cohesionless soil. The liquefaction analysis shows that most of the research areas have liquefaction, land subsidence, and lateral displacement potential.

Earthquake Induced Liquefaction Analysis and Ground Improvement as a Remedial Measure: A Review

Liquefaction is the phenomenon in which partially or fully saturated, loose sandy soils behave like a liquid due to loss of strength and rigidity owing to sudden increase in the pore water pressure as a result of dynamic loading such as earthquake. Liquefaction induced by dynamic loading as a result of earthquake is the most destructive feature of earthquake that may results in settlements and collapse of structures. The severity of this phenomenon can be predetermined by the geological and hydro-geological setup of the soil in the study area. The aim of this study is to present a review of various aspects of earthquake induced liquefaction analysis, case evidences from field studies and some of the liquefaction hazards from past earthquakes. Remedial measures using ground improvement techniques to prevent liquefaction hazard is also studied in this paper. Further, investigating the performance of remedial methods against liquefaction is also presented in this paper.

A comparative soil liquefaction analysis with a Matlab® based algorithm: soiLique

Soil liquefaction is one of the ground failures induced by earthquakes. Determining the safety factor and the settlements are the most common analyses to decrease liquefaction-induced failures and hazards. Scientists have suggested numerous empirical formulas to detect and mitigate liquefaction-based hazards, and they have been used over the decades. This study aims to present a user-friendly and interactive program for deterministic soil liquefaction analyses. The algorithm presented in this study, soiLique, is the first MATLAB® program, including a graphical user interface that provides the deterministic liquefaction analysis with the computation of parameters propounded with the formulas. One of the advantages of soiLique is that it allows picking the physical property of every layer (i.e., fine or coarse), which provides dealing with liquefaction prone layer(s) directly when necessary. Not only can one calculate parameters regarding soil liquefaction with the help of this program, but one also can see graphically supported results. The robustness of soiLique is checked with another soil liquefaction analysis program, SoilEngineering, which was introduced by Ozcep (2010). Calculations were done separately using real SPT data and synthetic data such as VS measurements and CPT data. The real SPT data and synthetic VS data were used to compare soiLique and SoilEngineering (Ozcep, 2010). The present study presents an example of CPT data analysis but could not be used for comparison. Comparisons reveal that outputs of soiLique and results of SoilEngineering showed a good agreement.

Calibration of Finn Model and UBCSAND Model for Simplified Liquefaction Analysis Procedures

Soil-liquefaction-related hazards can damage structures or lead to an extensive loss of life and property. Therefore, the stability and safety of structures against soil liquefaction are essential for evaluation in earthquake design. In practice, the simplified liquefaction analysis procedure associated with numerical simulation analysis is the most used approach for evaluating the behavior of structures or the effectiveness of mitigation plans. First, the occurrence of soil liquefaction is evaluated using the simplified procedure. If soil liquefaction occurs, the resulting structural damage or the following mitigation plan is evaluated using the numerical simulation analysis. Rational and comparable evaluation results between the simplified liquefaction analysis procedure and the numerical simulation analysis are achieved by ensuring that the liquefaction constitutive model used in the numerical simulation has a consistent liquefaction resistance with the simplified liquefaction analysis procedure. In this study, two frequently used liquefaction constitutive models (Finn model and UBCSAND model) were calibrated by fitting the liquefaction triggering curves of most used simplified liquefaction analysis procedures (NCEER, HBF, JRA96, and T-Y procedures) in Taiwan via FLAC program. In addition, the responses of two calibrated models were compared and discussed to provide guidelines for selecting an appropriate liquefaction constitutive model in future projects.

Analisis Potensi Likuefaksi dan Perbaikan Tanah dengan Stone Column: Studi Kasus pada Coal Shelter PLTU Lontar, Banten

ABSTRACT The high demand for electricity needs requires the availability of new generation sites. The new plant developed is a PLTU in Lontar. The condition of coal shelter as a research site dominated by silty clay and silty sand and located in the earthquake zoning is high that the planning of the coal shelter area must accordance with the feasibility of building establishment, it is necessary to analyze the potential liquefaction and improvement methods. Soil improvement efforts to reduce the potential for liquefaction include soil improvement with stone columns. The method of liquefaction analysis in this study uses the method developed by Idriss and Boulanger. The results of the analysis of the potential for liquefaction at BH-1 occurred at a depth of 3-16 m and at BH-3 the potential for liquefaction occurred at a depth of 4-24 m. Potential of the thickest layer for liquefaction is at BH-3 with a depth of 24 m. Improvement with a stone column can reduce the potential for liquefaction and can increase the value of the safety factor against the potential for liquefaction at the coal shelter location. Improvement analysis with a stone column using Plaxis software, the value of the safe factor after installing the stone column at BH-1 FS 2.89, at BH-3 FS became 2.65. ABSTRAKBanyaknya permintaan kebutuhan listrik yang tinggi diperlukan ketersediaan lokasi pembangkit baru. Pembangkit baru yang dikembangkan yaitu PLTU Batubara di Lontar. Kondisi coal shelter sebagai lokasi penelitian yang didominasi oleh lapisan tanah lempung kelanauan dan pasir kelanauan serta berada pada zonasi gempa cukup tinggi sehingga perencanaan area coal shelter harus memenuhi syarat kelayakan pendirian bangunan, maka perlu dilakukan analisis potensi likuefaksi serta metode perbaikannya. Upaya perbaikan tanah untuk mengurangi potensi likuefaksi yaitu perbaikan tanah dengan stone column (kolom batu). Metode analisis likuefaksi pada penelitian ini menggunakan metode yang dikembangkan oleh Idriss dan Boulanger. Hasil analisis potensi likuefaksi pada titik BH-1 terjadi di kedalaman 3-16 m dan pada titik BH-3 potensi likuefaksi terjadi pada kedalaman 4-24 m. Lapisan yang paling tebal mengalami potensi likuefaksi ada pada titik BH-3 dengan kedalaman 24 m. Perbaikan dengan stone column dapat mengurangi potensi likuefaksi dan mampu meningkatkan nilai faktor keamanan terhadap potensi likuefaksi di lokasi coal shelter. Analisis perbaikian dengan stone column menggunakan software Plaxis, nilai faktor aman setelah dipasang stone column pada titik BH-1 FS 2,89, pada titik BH-3 FS menjadi 2,65.

A Hybrid Method to Evaluate Soil Liquefaction Potential of Seabed at Offshore Wind Farm in Taiwan

This paper undertakes liquefaction analysis with simplified procedures with standard penetration test (SPT) data and cone penetration test (CPT) data obtained from an offshore wind farm in the Changhua area. The soil liquefaction resistance calculated by the SPT-based simplified procedure suggested by the Japan Railway Association was in agreement with the laboratory results. The CPT is widely used in the site investigation of offshore wind farms. However, Taiwan’s registered professional engineers are still familiar with soil liquefaction analysis for offshore wind farms using SPT-based methods. Hence, a hybrid method that incorporates an SPT–CPT correlation into the New Japan Road Association (NJRA) method is proposed to evaluate the soil liquefaction potential for offshore wind farms in Taiwan. In the case studies of soil liquefaction with five groups of adjacent boreholes in Changhua’s offshore wind farms, the hybrid method shows that the soil liquefaction potential with CPT data is consistent with the results calculated with SPT-based simplified procedures. To quantify the risk of soil liquefaction, Monte Carlo simulation is used to calculate the uncertainty of CPT–qc for estimating the probability of soil liquefaction with the hybrid method.

Discriminant Method of Sand Liquefaction

With the proposal of 1.8 billion mus of cultivated land red line and the rise of land reclamation in China, more and more national defense and civil projects are built on poor geological soil, such as reclamation reefs in the South China Sea. The liquefaction damage caused by earthquake, such as water spraying, grouting and surface cracks, has a great impact on such buildings, and poses a threat to people's lives and property. Therefore, it is of great significance to study the liquefaction of sand in foundation soil. Since Academician Huang Wen-xi first proposed to use indoor dynamic triaxial test to study liquefaction, a series of achievements have been made in the liquefaction of foundation soil. The research methods of sand liquefaction have developed from simple single sample of numerical simulation, numerical simulation and test. Referring to the literature at home and abroad, this paper sorted out the discriminant method of sand liquefaction, experimental study of sand liquefaction and post-liquefaction analysis.