In the present study, the overall stability of typical Korean composite caisson breakwaters that were initially designed following the conventional deterministic approach is investigated using reliability approaches. Therefore, the sensitivity of critical uncertainties regarding breakwater safety is analyzed. Uncertainty sources related to the structure, ocean conditions, and properties of the subsoil and rubble mound are considered in the reliability analysis. Sliding and overturning failures are presented as explicit equations, and three reliability methods, i.e., the mean value first-order second-moment, first-order reliability method, and Monte Carlo simulation, are applied in the evaluation process. Furthermore, the bearing capacity of the rubble mound and subsoil are analyzed using the discrete slice method conjugated with the Monte Carlo simulation. The results of this study establish that the sliding failure generally is the most frequent failure occurring among the above-mentioned overall stability failures (around 15 times more common than failures observed in the foundation). Additionally, it is found that the horizontal wave force primarily contributes to the sliding of the caisson body, whereas the friction coefficient is the main factor producing the resistance force. Furthermore, a much small probability of overturning failure implies that the overturning of a caisson around its heels uncommonly occurs during their lifetime, unlike other overall failure modes. Moreover, the failure in foundations may commonly encounter in the breakwater that has a high rubble mound structure compared with sliding mode. Particularly, the performance function of the all foundation bearing capacities presents a nonlinear behavior and positively skewed distribution when using the Monte Carlo simulation method. This phenomenon proves that simulation methods might be an appropriate approach to evaluate the bearing capacity of a breakwater foundation that can overcome several drawbacks of the conventional design approach.

This study investigates the system stability of breakwater foundations subjected to earthquakes from a probabilistic point of view. A fully probabilistic approach, i.e., a combination of the Monte Carlo simulation and Bishop’s simplified method, has been developed to evaluate the system failure probability of foundation damage, one of the prevailing failures encountered during earthquakes. Twelve sections of perforated caisson breakwaters located around Korea were chosen as case studies. First, the reliability analysis was performed for all the breakwaters at existing conditions; then, the calibration process involving the estimation of load and resistance factors was conducted for 12 breakwaters at three levels of the target reliability index. As the performance function, used in the stability analysis of breakwater foundations, is defined based on an implicit shape with a high-dimensional space of variables, the calibration process of load and resistance factors becomes cumbersome and complicated. Therefore, this study has proposed a sensitivity analysis to be implemented prior to the calibration process to elicit the effects of variables on the stability of each breakwater, which, thereafter, effectively directs the calibration process. The results of this study indicate that the failures in the foundation of breakwaters frequently occur in different modes. Therefore, the failure probability should be estimated considering all possible failure modes of the foundation. The sensitivity results elucidate that the soil strength parameters are the dominant variables, contributing to the stability of foundations, whereas the seismic coefficient presents the negative effect, causing the insecurity of breakwaters. In particular, the deadweights, though directly contributing to the seismic forces, show a small effect on the stability of foundations. The calibration shows that the load factors slightly vary with an increase in the target reliability index and set 1.10 for three safety levels. In contrast, the resistance factor exhibits an inverse relationship with the specified reliability index. Especially when the load factor equals 1.10, the resistance factors are 0.90, 0.85, and 0.80, corresponding to the reliability index of 2.0, 2.5, and 3.0, respectively. Eventually, it is proved that the sensitivity analysis prior to the calibration process makes the procedure more efficient. Accordingly, the iteration of simulation execution is diminished, and the convergence is quickly accomplished.

This paper presents the development of Load and Resistance Factor Design (LRFD) of axially-loaded driven piles in sands. The resistance factors of base and shaft resistances were calculated separately to account for their different uncertainty levels. The ratios of dead-to-live load and ultimate base resistance to limit shaft resistance change the uncertainty levels of total load and total pile capacity, respectively; thus, those ratios should be reflected in the calculation of base and shaft resistance factors. For the development of LRFD for axially-loaded driven piles in sands, the ultimate limit state for an axially-loaded driven pile was established based on the Imperial College Pile (ICP) design method; the uncertainties of loads and resistance were accessed; reliability analyses were performed using the First-order Reliability Method (FORM); and finally, reasonable resistance factors of base and shaft resistances were calculated based on the results of reliability analyses for different target reliability index levels. The load factors used for the calculation of resistance factors are the ones proposed by AASHTO and ASCE/SEI 7-05. From the results of extensible reliability analyses using FORM, the resistance factors for base and shaft resistances were found to be highly dependent on the ratios of the dead-to-live load and the ultimate base resistance to the limit shaft resistance. Resistance factors are proposed for different combinations of these ratios within their possible ranges.

This paper presents the reliability-based resistance factor calibration of driven steel pipe piles and the implementation of Load and Resistance Factor Design (LRFD) on practical design cases. Resistance factors of driven steel pipe piles were calibrated in the framework based on reliability theory using static pile load test results. The results of fifty seven load tests conducted to failure were compiled and these 57 data were divided into three different groups based on their data quality. For the three groups, reliability analyses were performed for two static bearing capacity equations and for different target reliability indices (2.0 and 2.33 for group piles and 2.5 for single piles) following the First-Order Reliability Method (FORM) and using the Monte Carlo Simulation (MCS). It is noted that the resistance factors were highly dependent on the quality of load test data. To implement the calibrated resistance factors, a case study on an actual bridge foundation design was performed. The case study result showed that, for the given target reliability index, the developed LRFD method using the resistance factors calibrated in this study could contribute to cost savings when it is compared with Allowable Stress Design (ASD) case using a safety factor of 3.0.

The Trauzl test is widely used to measure the explosive power of a substance by determining the volume increase produced by the detonation of a tested explosive charge in the cavity of a lead block with defined quality and size. In this study, the Trauzl lead block test and a high-speed 3D digital image correlation (3D-DIC) system were used to evaluate the effect of stemming on a blast hole. The blasting experiments were conducted with emulsion explosives. The stemming materials adopted in this study were sand, aggregate, and shear thickening fluid (STF)-based stemming materials. The results of the blasting experiments and numerical analysis showed that the expansion rate of the lead block was most affected by STF-based materials, followed by aggregates and sand stemming. Furthermore, the displacement and surface strain on the block were the highest in the experimental case using STF-based stemming materials. The STF-based stemming material developed in this study in open pit mining or various blasting constructions is expected to increase rock fragment efficiency, compared to that of general blasting stemming methods, and reduce blasting vibration by decreasing the amount of explosive per blast hole used for blasting.

In the process of the bridge design, especially the determination of width and length of pier foundations, the scour depth around the bridge could be very important factor for the economic and safe design of the bridge. The Woodrow Wilson bridge across the Potomac River in Washington D.C. is a six lane bridge which is being replaced by a twelve lane bridge due to the rapid growth of traffic. In this study, the scour depths are calculated for the existing bridge by using the SRICOS method, which has been developed to predict the evolution of the local scour depth at a bridge pier founded in soil or soft rock and compared with the measured scour depths. The scour depths of the replacement bridge are also calculated and discussed for the design purposes. The soil samples are taken from the bridge site by using thin wall Shelby tubes and tested in the EFA (Erosion Function Apparatus) to obtain the erosion function. The discharge hydrograph for the entire bridge life is obtained from the USGS website. Using these hydrologic and geotechnical data, the scour analyses were performed for the selected bridge piers. The E-SRICOS method and the S-SRICOS method give reasonable predictions.