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This study scrutinizes the dam behavior during different rates of water level fluctuations via centrifuge model tests and verifies the results by numerical analyses. LVDTs and pore water pressure gauges were installed to scrutinize the settlement and pore water pressure behavior during different rates of water level fluctuation. The centrifuge model test results suggest that the increased rate of water level fluctuation increases the risk of dam failure as drastic variations in pore water pressure and differential settlement were observed. The differential settlement in the upstream and downstream sides of the dam due to water level fluctuation increases the risk of cracking in the dam crest. Also, the dam stability was evaluated by comparing and analyzing the pore pressure and deformation distribution values obtained from the centrifuge model tests with numerical analysis results. Soil-void fluid coupled analyses were performed in the steady and unsteady seepage flow conditions. The analysis results manifest that the increased rate of fluctuation in water level becomes a factor for a rapid increase in the displacement and pore pressure of the dam body, resulting in a reduction in the dam stability. Thus, real-time monitoring of the displacement and pore water pressure during rapid fluctuations in water level, such as heavy rain, is required to ensure dam stability.

This study analyzes the behaviors of the Kyeryong embankment dam during various rates, i.e., quick and slow rate, of water level fluctuation using geotechnical centrifuge experiments that simulate the real scale stress conditions and water level fluctuation conditions of the real field. The collapse behavior of the embankment is also evaluated, in this study, by simulating overflow conditions during torrential downpours due to climate change. The embankment models are constructed at a reduced scale of 1:50; the protected and unprotected embankment crest conditions are replicated, and pore pressure gauges, displacement sensors (linear variable differential transformer LVDT) are installed to analyze the seepage and overtopping behaviors of the embankment by carrying out geotechnical centrifuge tests. The centrifuge test results manifest that repetitive and continuous fluctuation of water level is a major factor that causes embankment deformation through the accumulation of pore water pressure and settlement. In addition, it is confirmed that the installation of protection measures along with spillway helps to prevent the scouring of soil particles in the embankment downstream slope .

Janghyeon dam, located at Gangneung-si with 6.9 m height and constructed in 1947, is modeled at a scale of 1:60 to analyze the seismic behaviors of the dam during seismic loading through dynamic centrifuge model tests. The centrifuge model tests are performed by simulating the field stress conditions and seismic loads. The results of dynamic centrifuge model tests show that the dam with an intact core satisfies the stability criteria against crest settlement. In contrast, a settlement of 1.2% of the dam height suggests that the dam with a deteriorated core does not satisfy the stability criteria. The acceleration amplification ratio from the core base to crest is 1.1–1.6 in the case of the intact dam and is 1.15–2.32 in the case of the deteriorated dam. Thus, it is inferred that the acceleration and settlement responses rely not only on seismic loads but also on the condition of the dam (i.e., intact or deteriorated). The acceleration amplification and settlement in the deteriorated dam are observed to be apparent. This is due to the weakening phenomenon of the dam by water that seeps through the deteriorated core, which increases pore water pressure and saturation level. Thus, the dynamic behaviors of the earth-filled dam, obtained through this study, can be used as primary data for seismic design and reinforcement of dam.

Due to less visibility, underground facilities such as sewer pipelines are subjected to degradation until a major failure occurs. So, leakage detection of deteriorated underground sewer pipes is necessary to prevent expensive rehabilitation costs. The major causes of the frequent occurrence of ground subsidence and sewer leakage are excessive use of groundwater, reckless exploitation of natural resources, etc. In this study, the aerial thermal imaging (ATI) technique has been used to identify the leakage points in sewer pipelines by analyzing surface thermal diffusion behavior of the ground surface. Leakage is suspected at points of anomalous temperature variation. Then, ground-penetrating radar and closed-circuit television surveys have been carried out to strengthen the suspicion of sewer leakage. Irregular, erratic parabolic-shaped lines are observed at the points where the leakage is suspected through ATI. Finally, the test-pit excavation and simple cone penetration tests have been carried out which confirms the sewer leakage points. The leakage points are confirmed by a greater depth of penetration. The results of the cone penetration test carried out in E-21 and 23-24 sewer pipelines show that the depth of penetration at the leakage points is about 35 cm, which is greater than the depth of penetration at other points. So, it can be concluded that the aerial thermal imaging technique is an effective method to predict leakage in deteriorated underground sewer pipelines.

This study aims to evaluate the sensing performance of glass fiber-reinforced polymer (GFRP) rock bolt sensors instrumented with strain gauges for monitoring rockslides. Experimental studies are conducted with four different types of GFRP rock bolt sensors and concrete blocks having central holes and two shear joints. Two GFRP rock bolt sensors are inserted into holes and then fixed in concrete blocks with cement grout and soil, respectively. The other two are coated with heat-shrink tubes to protect strain gauges and wires, which are then fixed in concrete blocks with cement grout and soil, respectively. Double shear tests are performed to produce shear deformations of GFRP rock bolt sensors, and then strain change with shear displacement is monitored. The results manifest that the variation in strain with shear displacement is more sensitive in the GFRP rock bolt sensor fixed with soil than with cement grout. Also, strain gauge wires in the GFRP rock bolt sensor fixed with cement grout are broken earlier than with soil. Furthermore, it is confirmed that the heat-shrink tube effectively protects strain gauges and wires, so that GFRP rock bolt sensors coated with heat-shrink tubes work for a longer time than the uncoated sensors. The present study shows that the GFRP rock bolt sensor can be useful for monitoring rock slope failure.

A real-scale slope failure model experiment is performed to analyze the movement behavior of the slope during failure, and the results are analyzed through the x&ndash, MR control chart method, along with inverse displacement and various analysis sections such as K-values. As a result, the portent of failure can be identified to be about 7.7&ndash, 18.3 minutes prior to the final slope failure. As a result of the analyses of changes in the control limit in the various analyses sections, it is considered that the application of K = 3 to the x-MR control chart is effective. It is observed that using the x-MR control chart technique of the inverse displacement is useful for the early prediction of the anomalous behavior of a slope, through a more quick and objective judgment. Henceforth, it is necessary to establish clear techniques for prediction and analyses of slope failure through continuous research, and those results can be used as the basic data of a slope instrumentation management standard that can contribute to the mitigation of life and property damage caused by slope failure hazards.

Many causalities and economic losses are caused by natural disasters, such as landslides and slope failures, every year. This suggests that there is a need for an early warning system to mitigate casualties and economic losses. Most of the studies on early warning systems have been carried out by predicting landslide-prone areas, but studies related to the prediction of landslide occurrence time points by the real-time monitoring of slope displacement are still insufficient. In this study, a displacement sensor and an Internet of Things (IoT) monitoring system were combined together, to monitor slope failure through cutting experiments of a real-scale model slope. Real-time monitoring of the slope movement was performed simultaneously via a low-cost, efficient, and easy-to-use IoT system. Based on the obtained displacement data, an inverse displacement analysis was performed. Finally, a slope instrumentation standard was proposed based on the slope of the inverse displacement for early evacuation before slope failure.