Probabilistic characterization of subsurface stratigraphic configuration with modified random field approach

Coupled characterization of stratigraphic and geo-properties uncertainties – A conditional random field approach

Estimation of ultimate bearing capacity (UBC) of pre-stressed high-strength concrete (PHC) pipe pile is critical for optimizing pile design and construction. In this study, a standard penetration test (SPT), static cone penetration test (CPT) and static load test (SLT) were carried out to assess, determine and compare the UBC of the PHC pipe pile embedded in saturated sandy layers at different depths. The UBC was calculated with three methods including the JGJ94-2008 method, Meyerhof method and Schmertmann method based on in-situ blow count (N) of SPT (SPT-N) which was higher than the values recommended in survey report regardless of pile length. The average UBC values calculated with cone-tip resistance and sleeve friction from CPTs was also higher than the value recommended in the survey report. Moreover, the actual UBC values directly obtained by load-displacement curves from SLTs were in line with the calculated values based on in-situ SPTs and CPTs, but approximately twice as high as the values recommended in the survey report regardless of pile length. For the SPT method, the application of bentonite mud in saturated sand layers is critical for the assessment of pile capacity in the survey phase, CPTs can provide reliable results regardless of soil characteristics and groundwater if the soil layer can be penetrated, and SLTs are necessary to accurately determine the UBC in complex stratum.

Evaluation of Ultimate Bearing Capacity of Pre-Stressed High-Strength Concrete Pipe Pile Embedded in Saturated Sandy Soil Based on In-Situ Test

With the increasing construction of large-scale wind turbines in seismically active coastal areas, the survivability of these high-rated-power offshore wind turbines (OWTs) in marine and geological conditions becomes extremely important. Although research on the dynamic behaviors of OWTs under earthquakes has been conducted with consideration of the soil-structure interaction, the attention paid to the impact of earthquake-induced seabed liquefaction on OWTs supported by large-diameter monopiles remains limited. In view of this research gap, this study carries out dynamic analyses of a 10 MW OWT under combined wind, wave, and earthquake loadings. This study uses a pressure-dependent multisurface elastoplastic constitutive model to simulate the soil liquefaction phenomenon. The results indicate that the motion of the large-diameter monopile leads to more extensive soil liquefaction surrounding the monopile, specifically in the zone near the pile toe. Moreover, compared with earthquake loading alone, liquefaction becomes more severe under the coupled wind and earthquake loadings. Accordingly, the dynamic responses of the OWT are apparently amplified, which demonstrates the importance of considering the coupling loadings. Compared with wind loading, the effect of wave loading on the dynamic response and liquefaction potential is relatively insignificant. 

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Seismic Analysis of 10 MW Offshore Wind Turbine with Large-Diameter Monopile in Consideration of Seabed Liquefaction

Submarine telecommunication cables are the physical backbone of the Internet. They are often buried shallowly beneath seabed and affected by seabed movements. Due to the long distance of cables and the complexity of submarine environment, interaction between cables and seabed movements inevitably involves various parameter uncertainties. However, effects of parameter uncertainties on submarine cable responses to seabed movements have not been fully investigated. This paper aims to address this problem using random finite element method (RFEM) that integrates finite element (FE) analysis with Monte Carlo simulation (MCS). First, deterministic FE analysis is performed to investigate cable responses to lateral seabed movements. Then MCS is implemented to study the effects of parameter uncertainties on cable responses. Statistical analysis of the MCS results is performed to prioritize the effects of parameter uncertainties on cable damage probability. Random field is also used to model spatial variability of soil parameters. Effect of the correlation length on cable damage probability is investigated. The results show that uncertainty of the anchored cable length La has the most significant effect on cable damage probability, while the effects of uncertainties in soil friction angle ϕ and effective unit weight γ′ are minor. Ignoring spatial variability of soil parameters may lead to significant misjudgment of cable damage risk.

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Effects of Parameter Uncertainties on Interaction between Submarine Telecommunication Cables and Lateral Seabed Movements

Assessment on liquefaction potential of seabed soil in Chang-Bin Offshore wind farm considering parametric uncertainty of standard penetration tests

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.

Kai Jun Chong

Papers

Assessment on liquefaction potential of seabed soil in Chang-Bin Offshore wind farm considering parametric uncertainty of standard penetration tests

A hybrid method to evaluate soil liquefaction potential of seabed at offshore wind farm in Taiwan