• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6C
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• pp.249-257
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• 2012

The reinforced earth method is financially viable. Furthermore, it overcomes environmental limitations and is therefore employed in retaining walls, slopes, foundations, roads, embankments, and other structures. However, in some cases, reinforced retaining walls are not strong enough in the curved sections and can collapse. Such mishaps are believed to occur because of an unsatisfactory analysis of the curved sections of a reinforced retaining wall. Accordingly, with the aim of investigating the workability and structural safety of curved sections of various types, this study investigates the differences in the estimated horizontal displacements of curved sections of various types and subsequently uses this information to study and analyze preliminary data so that appropriate measures can be taken to resolve alignment issues. The results of an experiment reveal that when a load is applied to curved sections of both concave and convex types, the largest horizontal displacement occurs at the center of the section. In the concave form, the earth pressure force is directed inward, whereas in the convex form, this force is directed outward. As a result, the horizontal displacement in convex forms is larger than that in concave forms. Convex reinforced earth structures are subjected to earth pressures as well as lateral earth pressure, therefore horizontal displacements in convex curved sections is larger than that of concave curved sections.

• Journal of the Korean Geosynthetics Society
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• v.13 no.1
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• pp.11-22
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• 2014

In this study, numerical analyses and model tests were conducted to figure out the behavior of a slope reinforced by upward drainable soil nails during rainfall. The model tests were carried out on both reinforced and unreinforced slopes. To verify the results of the tests, seepage analyses were performed and compared with the test results using a commercial program, SEEP/W. The results showed that the numerical analyses have in overall a good agreement with the experiments in the variations of ground water level and pore water pressure even though there is some time delay for the experiment before the changes in the ground water level and pore water pressure after rainfall are observed, while the numerical analyses not.

• The Journal of the Korea Contents Association
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• v.16 no.7
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• pp.457-464
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• 2016

The analysis for stability of slope reinforced with soil nails need professional knowledge and skilled technology for program. So we spend a lot of money and time. In this study, we try to save it. After we analyzed the stability of reinforced slope with MIDAS GTS using shear strength reduction technique, we made charts by result. Charts created in the stydy can be used rapidly in slope disaster prevention. We try to analyze stability of slopes when we changed nail spacing, nail angle, slope type, properties of soil. We obtained relationship as follows; 1) The safety factor appears effectively when the nail angle is $10{\sim}20^{\circ}$. 2) The safety factor appears effectively when the nail spacing is 0.8~1.2m. 3) The error of Singh's and suggested chart are 3.45, 8.65, 4.35% when the slope are 1:0.5, 1:1, 1:2.

• Computers and Concrete
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• v.3 no.4
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• pp.213-233
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• 2006

Over the past years techniques for non-linear analysis have been enhanced significantly via improved solution procedures, extended finite element techniques and increased robustness of constitutive models. Nevertheless, problems remain, especially for real world structures of softening materials like concrete. The softening gives negative stiffness and risk of bifurcations due to multiple cracks that compete to survive. Incremental-iterative techniques have difficulties in selecting and handling the local peaks and snap-backs. In this contribution, an alternative method is proposed. The softening diagram of negative slope is replaced by a saw-tooth diagram of positive slopes. The incremental-iterative Newton method is replaced by a series of linear analyses using a special scaling technique with subsequent stiffness/strength reduction per critical element. It is shown that this event-by-event strategy is robust and reliable. First, the model is shown to be objective with respect to mesh refinement. Next, the example of a large-scale dog-bone specimen in direct tension is analyzed using an isotropic version of the saw-tooth model. The model is capable of automatically providing the snap-back response. Subsequently, the saw-tooth model is extended to include anisotropy for fixed crack directions to accommodate both tensile cracking and compression strut action for reinforced concrete. Three different reinforced concrete structures are analyzed, a tension-pull specimen, a slender beam and a slab. In all cases, the model naturally provides the local peaks and snap-backs associated with the subsequent development of primary cracks starting from the rebar. The secant saw-tooth stiffness is always positive and the analysis always 'converges'. Bifurcations are prevented due to the scaling technique.

• Geomechanics and Engineering
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• v.17 no.6
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• pp.507-513
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• 2019

Reinforced soil and Expanded Polystyrenes (EPS) mixture (RSEM) is a geomaterial which has many merits, such as light weight, wide strength range, easy for construction, and economic feasibility. It has been widely applied to improve soft ground, solve bridge head jump, fill cavity in pipeline and widen highway. Reutilizing dredged sediment to produce RSEM as earthfill can not only consume a large amount of waste sediment but also significantly reduce the construction cost. Therefore, there is an urgent need understand the basic stress-strain characteristics of reinforced dredged sediment-EPS mixture (RDSEM). A series of cyclic triaxial tests were then carried out on the RDSEM and control clay. The effects of cement content, EPS beads content and confining pressure on the cyclic stress-strain behaviour of RDSEM were analyzed. It is found that the three stages of dynamic stress-strain relationship of ordinary soil, vibration compaction stage, vibration shear stage and vibration failure stage are also applicative for RDSEM. The cyclic stress-strain curves of RDSEM are lower than that of control clay in the vibration compaction stage because of its high moisture content. The slopes of backbone curves of RDSEMs in the vibration shear stage are larger than that of control clay, indicating that the existence of EPS beads provides plastic resistance. With the increase of cement content, the cyclic stress-strain relationship tends to be steeper. Increasing cement content and confining pressure could improve the cyclic strength and cyclic stiffness of RDSEM.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.513-520
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• 2003

A numerical comparison or predictions by limit equilibrium analysis and 3n analysis is presented for slope/pile system. Special attention is given to the coupled analysis based on the explicit-finite-difference code, FLAC. To this end, an internal routine (FISH) was developed to calculate a factor of safety for a pile-reinforced slope according to shear strength reduction technique. The case of coupled analyses was performed for stabilizing piles in slope in which the pile response and slope stability are considered simultaneously and subsequently the factors of safety are compared to uncoupled analysis (limit equilibrium analysis) solution for a homogeneous slope. Based on a limited parametric study, it is shown that in the free-head condition the factor of safety in slope is more conservative for a coupled analysis than for an uncoupled analysis and a definitely larger value represents when piles are installed in the middle of the slopes and are restrained in the pile head.

• Proceedings of the Korean Geotechical Society Conference
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• 1993.10a
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• pp.63-68
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• 1993

Soil nailing is a method of reinforcing natural deposits of soil with passive inclusions, called nails, of steel or other materials. Its purpose is mainly to increase the tensile and shear strength of the soil mass. This method has been widely used during the last two decades to stabilize steep slopes in several countries (France, Germany, USA, Japan, etc.). The design methods that have been mostly used are Davis method, German method, and French method which are based on limit equilibrium approaches, and Juran method which utilizes the kinematical limit equilibrium design concept. This paper is focussed on the evaluation of the available design methods(especially, the France, Davis and German design methods) through comparison with each different assumption for the failure surface, the concept of failure mechanism and the definition of safety factor. The parametric study to identify the effects of design parameters on the overall factor of safety has also been conducted. By considering the results along with the associated assumptions which have been postulated in the several methods, the applicability of the method for a given soil and nail conditions has been evaluated.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.521-528
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• 2002

This paper presents the results of centrifuge model tests on the reinforced slope by pressure grouting. Tests were performed to investigate the reinforcing effect of grouting. In the tests, slopes of scale factor 1/10 were used changing the space and number of reinforcing bar. Test results are as tile follows; 1. The reinforcing effect increase rapidly with reinforcement area ratio at low value of reinforcement area ratio. 2. At high reinforcement area ratio the increase ratio of reinforcing effect decrease. 3. At same reinforcement area ratio, the reinforcing effect of double reinforcing bar was larger than the single reinforcing bar due to arching effect.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.643-650
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• 2002

It is necessary, in the light of the importance of long-term slope stability problem, to develop a simple method or tool which can figure out the possible failure zone resulted from weathering effect and other factors. The FBG sensor system is used to estimate the correlations between the temperature and the slope in Yunhwajae, and to find a failure zone in slopes effectively. This research is to seek for the correlation between the soil temperature distribution and the strain distribution in a active zone by analyzing the data from the in-situ measurement so that the possible failure zone should be well defined based on the correlation. The zone of high temperature fluctuation can be regarded as one of the possible sliding zone due to the weathering effect while the constant temperature depth of the ground, if exists, would not be relatively affected by the weathering process.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.06a
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• pp.65-81
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• 2003

During the last few decades in Korea, the development of hillside or mountain areas has rapidly increased for infrastructure construction such as railroads, highways and housing. Many landslides have occurred during these constructions. Also, the amount and scale of damage caused by landslides have increased every year. In the case of Far East Asia including Korea, the damage of landslides is consequently reported during the wet season. In this paper, the effect of stabilizing piles on slope stability is checked and the behavior of slope soil and piles are observed throughout the year by field measurements in the large-scale cut slopes. In particular a large-scale cut slope situated on the construction site for the express highway in Donghae, Korea. First of all, The behavior of the slope soil was measured by inclinometers during slope modification. Landslides occurred in this area due to the soil cutting for slope modification. The horizontal deformations of slope soil gradually increased and rapidly decreased at depth of sliding surface indicating that the depth of sliding surface below the ground surface can be predicted. On the basis of being able to predict the depth of the sliding surface, stabilizing piles were designed and constructed in this slope. To ensure the stability of the reinforced slope using stabilizing piles, an instrumentation system was installed. The maximum deflection of piles is measured at the pile head and it is noted that the piles deform like deflection on a cantilever beam. The maximum bending stress of piles is measured at the soil layer. The pile above the soil layer is subjected to lateral earth pressure due to driving force of the slope, while pile below soil layer is subjected to subgrade reaction against pile deflection. As a result of research, the effect and applicability of stabilizing piles in large-scale cut slopes could be confirmed sufficiently.