• Journal of the Korean Geosynthetics Society
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• v.12 no.1
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• pp.39-50
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• 2013

This study aims at investigating the behavior of the ground water level when installing upward soil nails that drain water as well. To do this, a series of down-scaled model tests were conducted. A model slope with weathered soils was prepared and then an artificial rain was scattered on the slope. The relative densities of soil specimen were 60%, 75%, and 90%, and the rainfall intensities 50mm/hr, 75mm/hr, 100mm/hr, and 125mm/hr, respectively. The experimental parameters, such as the ground water level, ratio of soil runoff, and failure mode of the slope were measured and analyzed. As the results, It may be concluded that the ground water level in the slope supported by drainable upward soil nails increases very gradually while the unsupported soil changes dramatically. In addition, the ground water level becomes constant and no failure occurs as time goes by. In case of the relative density of 75%, the runoff ratio seemed to increase up to about 8~15% after reinforcement.

• The Journal of Engineering Research
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• v.6 no.1
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• pp.83-96
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• 2004

A soil mailed wall is adapted as road widening measure and is constructed under a miniature abutment built on steel pipe piles. The soil nailed wall called for removal of the existing embankment slope to permanently retain the fill behind the abutment. The soil nailed wall is fully instrumented and is monitored. A 3D finite element analysis is used to study further the behavior of the soil nailed wall. The complete sequence of construction is simulated. The numerical model is calibrated against the instrumented nailed wall. Then a parametric study is conducted. The results provide valuable information related to the effect of the excavation and nailing on the following: axial load and bending moment in the piles, load in the nails, and wall deflections.

• Journal of the Korean Geotechnical Society
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• v.18 no.3
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• pp.33-41
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• 2002

Soil nailing type of retaining structures has been widely used in Korea far the purpose of the temporary and permanent support in excavations and slope stability. The important factors in application of soil nailing systems in urban excavation site nearby the existing structures are the displacement of the wall and tensile farce of the nails, etc. In this paper, the fled back analyses are carried out at 11 excavation sites to investigate the behavior of tensile farce of nails at stepwise excavation in the multi-layered strata including various rock layers. The results of the fled back analysis are less than about 50% of the measured ones. The distance of active zone by measurements are shown almost larger than that of fled back analysis when the distance of active Bone is defined from the surface of wall to the potential failure surface. And the results of fled back analysis are within the range proposed by the project CLOUTERRE and Cartier & Gigan (1983) which were 0.3$H_f$, and 0.5$H_f$, of the final excavation depth ($H_f$,) respectively, but the values of the measurement were larger than these values.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.997-1000
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• 2008

Strength development of concrete subjected to cold weather is generally delayed due to its low temperature. In case of soil nailing method, it is necessary to apply the shotcrete. However, the shotcrete placement under low temperature experiences retardation of strength development due to delayed hydration reaction. Therefore, in this paper, the use of fine particle cement which is produced through particle classification in cement manufacturing process, is discussed to enhance the strength development of the shotcrete under low temperature. According to the results, the concrete containing 100% of fine particle cement had excellent strength development even at $-9^{\circ}C$ of temperature and at 5days, it reached design strength with PE film curing. It is thought that more than 70% of fine particle cement can secure required strength of the shotcrete even at low temperature condition.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.2
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• pp.158-165
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• 2014

The enormous quantity of 'Bayer-Process by-products' (BP by-products) discharged by industries producing alumina from bauxite represents an environmental and economical problem. As it is mainly composed of $Fe_2O_3$, $Al_2O_3$, $SiO_2$, CaO and $Na_2O$, it is thought that using BP by-products as a construction material is an effective way to consume such a large quantity of alkaline waste. In this study, This study evaluates the effect of alkali-activated binder based on recycling BP by-products on soil improvement through the evaluation of slope stability and seepage flow numerical analysis. The results of analysis of ground slope safety at dry season and wet season meet standard (Ministry of Land, Infrastructure and Transport, 2006) Especially, when wet season, the ground used soil improving material meet standard, while the ground used soil-nailing method doesn't. Also, permeability coefficient of improved soil is smaller than that of natural soil and saturation depth of reinforced ground surface with improve soil is lower than that of natural soil.

• Journal of the Korean Geosynthetics Society
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• v.19 no.1
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• pp.75-82
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• 2020

There have been often cases of collapse for geogrid reinforced soil (GRS) retaining wall. Hence, social interest in the reinforcement and restoration of the collapsed GRS wall is increasing day by day. However, there are only few researches. For this reason, a series of numerical analyses using the Plaxis 2D program was conducted in this study to analyze the suitable reinforcement methods that can be applied on the existing damaged GRS wall caused by overturning of the modular blocks facing and the surface settlement at the backfill as the results from the design failure. The restoration plan used in this study is composed of two cases: (Case 1) soil nailing reinforcement and reinforced concrete (RC) wall facing construction on the existing damaged GRS wall; and (Case 2) removal of the entire damaged GRS wall and then reconstruction. The results on the internal stability of the GRS wall show that Case 1 obtained a greater safety factor than Case 2 for tensile force while Case 2 had a greater safety factor than Case 1 for pullout failures. Case 1 was found to be more stable than Case 2 in terms of the global slope safety by shear strength reduction method and the external deformation behavior by numerical analysis. In this study, the existing damaged GRS wall which was reinforced using Case 1 method shows more stable external behavior.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.3
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• pp.237-246
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• 2021

With climate change, debris flow has been increasing due to the collapse and erosion of shallow slopes caused by extreme rainfall. It is preferred to an economical and eco-friendly method rather than reinforcement of soil slopes with the earth anchor or nailing method. In this study, a soil improvement agent was developed by utilizing insitu soil, leaf mold, and used harbal medicine to help sufficient vegetation. In addition, to prevent surface erosion, shear strength of the soil was increased by using micro cement and hemihydrate gypsum as additives. The optimum mix ratio of the mixture is determined by increasing the shear strength by checking the erosion progress of the ground surface layer due to rainfall through an laboratory test. The safety factor of soil slope has been improved on the slope surface reinforced by the improvement agent, and the strength of erosion has been increased, making it efficient to cope with heavy rain during wet season.

• Geotechnical Engineering
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• v.11 no.4
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• pp.49-62
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• 1995

Soil nailing has been widely rosed during the last two decades to stabilize sheep excavated slopes in several countries. In thin study, the discrete element method has been applied to evaluate the stability of the reiuorced slope. This method is capable of not only estimat ins tensile and sheer stresses mobilized in nails but also providing individual safety factors of soil and nails, It has been assumed that the nailed slope be comprised of slices connected with elastoplastic twinkler springs. A reasonable mechanism is applied for representing the behavior between nails and adj scent soils. Taking into account for the bequence of construction the developed method well predicts the measured tensile forces developed in nails so that it is possible to appropriately evaluate the overall safety factor.

• Smart Structures and Systems
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• v.9 no.5
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• pp.393-410
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• 2012

Conventional geotechnical instrumentation techniques available for monitoring of slopes, especially soil-nailed slopes have limitations such as electromagnetic interference, low accuracy, poor longterm reliability and difficulty in mounting a series of strain sensors on a soil nail bar with a small-diameter. This paper presents a slope monitoring system based on fibre Bragg grating (FBG) sensing technology. This monitoring system is designed to perform long-term monitoring of slope movements, strains along soil nails, and other slope reinforcement elements. All these FBG sensors are fabricated and calibrated in laboratory and a trial of this monitoring system has been successfully conducted on a roadside slope in Hong Kong. As part of the slope stability improvement works, soil nails and a toe support soldier-pile wall were constructed. During the slope works, more than 100 FBG sensors were installed on a soil nail, a soldier pile, and an in- place inclinometer. The paper presents the layout and arrangement of the instruments as well as the installation procedures adopted. Monitoring data have been collected since March 2008. This trial has demonstrated the great potential of the optical fibre monitoring system for long-term monitoring of slope performance. The advantages of the slope monitoring system and experience gained in the field implementation are also discussed in the paper.

• Journal of the Korean GEO-environmental Society
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• v.18 no.7
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• pp.13-20
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• 2017

Soil nailing is ground reinforcement method using the shear strength of ground and the pullout shear resistance force of nail. It is mainly used for reinforcement of cut slopes, earth retaining structures and retaining walls, etc. It may be designed considering the pullout resistance of nail in the case of earth retaining structure and retaining wall, but it should be designed considering not only pullout resistance but also shear and bending resistance in the case of slope. However, conservative designs considering only pullout resistance are being done and most of the studies are about increasing pullout resistance by improving of material, shape and construction method of nail. Actually, Shear bending deformations occur centering on the active surface in ground reinforced with the nail. The grout with relatively low strength is destroyed and separated from the reinforcing material. As a result, the ground is collapsed while reducing the frictional resistance rapidly. Therefore, it is necessary to develop the method to increase the shear resistance while preventing separation of nail and grout body. In this study, an experimental study was conducted on new soil nailing method which can increase shear resistance by forming protrusions through pressurized grouting after installing a packer on the outside of deformed bar.