The presented case study describes the progressive movement of a shallow landslide in Central South Korea after excavation of its toe and subsequent, sustained above-average rainfall. Measured soil data as well as real-time measurements of slope movement and precipitation enabled calibration of a numerical model based on the finite element method (FEM) to capture the destabilization and associated movement of the slope. The numerical model employed the Bishop's effective stress approach to define the state of stresses in unsaturated soils, as well as transient seepage analyses to introduce the non-uniform effects of actual rainfall data into the analysis. The resulting model provided insight into the complex behavior of a progressively failing slope. It demonstrates that use of numerical methods like FEM that allow for coupled transient unsaturated seepage-stress analyses presents a means of evaluating the progressive failure of slopes under rainfall. Furthermore, it demonstrated that for certain slopes under partially saturated conditions, sustained aboveaverage rainfall may cause shallow landsliding when driven by stimuli like excavation. Additionally, the kinematics of failing slopes may not always follow classical slope stability approaches (sliding block method, circular method of slices, log-spiral, etc.) prior and during slope failure. The given kinematics of a slope failure may change with movement, redistribution of principal stresses, and dissipation of suction stress. Therefore, analyses like FEM present a unique tool to evaluate the deformation behavior of failing slopes on a case-by-case basis.
A novel technology (electrokinetics) is proposed to improve acidizing operations, i.e., increase the penetration distance. The acid dissolves the carbonates (limestones/dolomites), enlarging the pores and increasing the width of pre-existing fractures. This gives rise to an increase in permeability. The principal acid commonly used is hydrochloric (HCl), which is pumped through tubing. Aqueous solutions of hydrochloric acid (usually 15%) are pumped into the carbonate formations to enlarge the pores and pre-existing fractures. Without application of D.C. current, the penetration distance is usually very short, especially in tight rocks. However, the penetration distance of acid is very short. By applying D.C. current, one can drive the acid for long distances into the formation being acidized.
Prevention plans for landslide and slope disasters should be appropriate for a country's budget when considering a systematic investment plan. The systematic management of slopes adjacent to national highways should incorporate reasonable investment risk and the expected degree of damage should be calculated by considering the investment priorities. In terms of priority of investment, the major factors used to determine the degree of hazard are gradient, soil characteristics, RMR (Rock Mass Rating), stability interpretation, type of discontinuities, and history of collapse, among others. The likely consequences of slope failure can be determined by considering traffic volume, the number of lanes, and average vehicle risk. We performed such calculations regarding the priority of investment and performed a regression analysis for 392 slopes located in Yeongseo region, Gangwon province. The calculation results show that collapsed slopes have a higher priority for investment, as do slopes with a high proportion of dangerous sections and locations in valleys.
Many cut slopes are located near national highways, resulting in large annual damage to infrastructure from the collapse of cut slopes. Therefore, to effectively maintain cut slopes, high-risk slopes should be identified and monitored. In this paper, we evaluate the effectiveness of the management of cut slopes using the risk score calculated from cut-slope inventory data. The inventory survey, as a simple assessment of the characteristics of various slopes, was performed to collect basic data that could be obtained visually in the field for the management of cut slopes. This method is not a precise survey, and it was composed of the general status and characteristics of cut slopes, the inspector's assessment, and inventory data in order to estimate a risk score for each slope. In this paper, we calculated the risk score by investigating the present status of cut slopes adjacent to 10,461 national roads. In order to evaluate the effectiveness of using risk score data, we compared the score for stable slopes with those of failed cut slopes. Failed cut slopes occurred in sections with the highest risk score. The results show that risk score derived from the inventory survey of cut slopes are useful in the management of cut slopes with risk of failure and in monitoring large numbers of cut slopes.
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