• Geotechnical Engineering
• /
• v.14 no.4
• /
• pp.61-76
• /
• 1998

Various kinds of reinforced soil methods have been developed by many researchers or companies for their economic merits mainly. These methods have generally used sandy soils which have high permeability as embanking or backfill material. That is because, if poor embanking materials, especially like a clayey soil which has very low permeability, are used in a reinforced soil embanking, and if excessive pore water pressure is produced by external factors, the friction resistance between reinforcing members and Boils decrease, as a result possible damage or collapse of the body of a reinforced embankment. In fact, clayey Boils can also be used as a embanking materials with reinforcement which has high permeable capacity, and are expected to be able to dissipate the excess pore water pressure effectively. In this study reinforcing effects have been examined through a serries of direct shear tests in which clayey soils are reinforced with nonwoven geotextiles of which permeability is very high and tensile strength is relatively weaker than geogrids which are usually used in reinforced soil wall. Even though such nonwoven geotextile are used as reinforcement of high saturated clayey soils. the test results show the possibility that nonwoven geoteztiles could be used as a reinforcement for reinforced soil walls effectively.

• Journal of the Korean Geosynthetics Society
• /
• v.16 no.4
• /
• pp.83-92
• /
• 2017

This paper deals with numerical analysis of behavior of curved mechanically stabilized earth(MSE) walls with geosynthetics reinforcement. Unlike typical concrete retaining walls, MSE wall enables securing stability of higher walls without being constrained by backfill height and is currently and widely used to create spaces for industrial and residential complexes. The design of MSE walls is carried out by checking external stability, similarly to the external checks of conventional retaining wall. In addition, internal stability check is mandatory. Typical stability check based on numerical analysis is done assuming 2-dimensional condition (plane strain condition). However, according to the former studies of 3-dimensional MSE wall, the most weakest part of a curved geosynthetic MSE wall is reported as the convex location, which is also identified from the studies of the laboratory model tests and field monitoring. In order to understand the behaviour of the convex location of the MSE wall, 2-dimensional analysis clearly reveals its limitation. Furthermore, laboratory model tests and field monitoring also have restriction in recognizing their behaviour and failure mechanism. In this study, 3-dimensional numerical analysis was performed to figure out the behaviour of the curved part of the geosynthetic reinforced wall, and the results of the straight-line and curved part in the numerical analysis were compared and analysed. In addition, the behaviour characteristics at each condition were compared by considering the overburden load and relative density of backfill.

• Journal of the Korean Geosynthetics Society
• /
• v.20 no.3
• /
• pp.1-10
• /
• 2021

The purpose of this study is to present the possibility a utilization of the tertiary mudstone in Pohang as road subsoil material through pilot experiments on the road embankment structure. This mudstone is an unconsolidated rock that is distributed in the soft rock sedimentary layer, the tertiary layer of the Cenozoic, and causes physical problems such as slaking, swelling, and reduced shear strength and chemical problem like acid drainage. In order to solve various complex problems, an laboratory mixing test was conducted, and the optimal mixing conditions of the tertiary mudstone (90%), composite slag (steel making 70%, blast furnace 30%), and neutralization and coating agent treatment were derived. In order to prove its utilization, a real-scale road embankment structure was constructed and tests were conducted for each section. The pre-processing section is stable due to the design of optimal mixing conditions, while in post-processing section, natural weathering proceeded rapidly, and structural problems were concerned. Since the effect of neutralizing and coating agents was confirmed in temporary-staking section, the neutralizing and coating agents can be applied during the temporary storage period.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.6C
• /
• pp.213-220
• /
• 2011

Fines such as silt or clay are usually mixed with granular particles in natural or reclaimed soils which are slightly cemented. Such fines contained within weakly cemented soils may influence permeability and also mechanical behavior of the soils. In this study, a series of unconfined compression tests on weakly cemented sands with fines are carried out in order to evaluate the effect of fines on unconfined compressive strength (UCS) of cemented soils. Two different cement ratios and fine types were used and fine contents varied by 5, 10, and 15%. Two types of specimens were prepared in this testing. One is the specimen with the same compaction energy applied. The other is the one with the same dry density by varying compaction energy. When the same amount of compaction energy was applied to a specimen, its density increased as a fine content increased. As a result, the UCS of cemented soils with fines increased up to 2.6 times that of one without fines as an amount of fines increased. However, when the specimen was prepared to have the same density, its UCS slightly decreased and then increased a little as a fine content increased. Under the same conditions, a UCS of the specimen with silt was stronger than the one with kaolin. As a cement ratio increased, a UCS increased regardless of fine type and content.

• Journal of the Korean GEO-environmental Society
• /
• v.11 no.7
• /
• pp.51-56
• /
• 2010

Recently, the land area for many people has been limited because of industrialization and modernization in Korea. The large-scale constructions like the reclamation development projects have been progressed to resolve this problem mentioned above. Therefore, as many of the useful construction materials as possible are needed to perform the largescale construction projects. Many studies for the utilization of pond ash which has a similar characteristic of sand have been conducted and there has been often occurred many structural problems on roadbed in winter. Therefore, the characteristics of the freezing and thawing for Controlled Low-Strength Material(CLSM) using pond ash were analyzed and evaluated by unconfined compressive strength test and mass loss test in this study. As a result of this study, it was confirmed that new CLSM using pond ash with cement(8.2% by weight) was able to stand for the freezing and thawing behavior and was satisfied with the standard of Portland Cement Association.

• Geotechnical Engineering
• /
• v.5 no.2
• /
• pp.45-56
• /
• 1989

The influence of stress path on the deformation characteristics of clay has been studied through a series of stress-path controlled triaxial tests on artificially sedimented and normally con- solidated Kaolinite. It has been found that there exists a critical stress increment ratio, Kc, in which stress·strain characteristics possesses a linear relationships and beyond Kc, strain hardening. A modified hyperbolic constitutive model for the strain hardening behavior has been formulated based on the Drnevich's hyperbolic function. And, a method of settlement analyses has been Proposed wherein the effect of stress path during consolidation is taken into account.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.3 no.2 s.9
• /
• pp.99-110
• /
• 2003

In this study, lightening material weight and normalizing structure of preventing system of landslide soil-rock in trench excavation was tried with focusing in safety construction availability and workability. In other words, risk estimate, safety management method investigation, applicability of bracing material and mechanical stability of bracing structure was studied. From these result, structural stability and structural analysis of light weight bracing structure was carried out with common structural analysis program, for examining movement mechanism of bracing structure and normalization of standard. The result are summarized as following. (1) Mechanical ability of bracing members and soil pressure parameter acting to member for ensuring mechanical propriety of bracing structural and useful of new material considering soil mechanics boundary were proposed. Also theory and method of analysis of bracing structural were proposed. (2) As a result of the structure analysis of geographical profile for light pannel used FRP as hard clay mechanical characteristics(bending moment, shear force, axial force) of panel were changed according to groundwater level and it is proved that the result of mechanical analysis is within allowable stress. Thus, light pannel is available for bracing structure in trench excavation.

• Journal of the Korean Society for Railway
• /
• v.20 no.1
• /
• pp.64-75
• /
• 2017

The role of a track subgrade is to provide bearing capacity and distribute load transferred to lower foundation soils. Track subgrade soils are usually compacted by heavy mechanical machines in the field, such that sometimes they are attributed to progressive residual settlement during the service after construction completion of the railway track. The progressive residual settlement generated in the upper part of a track subgrade is mostly non-recoverable plastic deformation, which causes unstable conditions such as track irregularity. Nonetheless, up to now no design code for allowable residual settlement of subgrade in a railway trackbed has been proposed based on mechanical testing, such as repetitive triaxial testing. At this time, to check the DOC or stiffness of the soil, field test criteria for compacted track subgrade are composed of data from RPBT and field compaction testing. However, the field test criteria do not provide critical design values obtained from mechanical test results that can offer correct information about allowable permanent deformation. In this study, a test procedure is proposed for permanent deformation of compacted subgrade soil that is used usually in railway trackbed in the laboratory using repetitive triaxial testing. To develop the test procedure, an FEA was performed to obtain the shear stress ratio (${\tau}/{\tau}_f$) and the confining stress (${\sigma}_3$) on the top of the subgrade. Comprehensive repetitive triaxial tests were performed using the proposed test procedure on several field subgrade soils obtained in construction sites of railway trackbeds. A permanent deformation model was proposed using the test results for the railway track.

• Journal of Korean Society of Forest Science
• /
• v.84 no.2
• /
• pp.166-177
• /
• 1995

This study was carried out to discuss how soils in the area planned for a forest road construction can be mechanically tested and practically applied. For this, 16 soil test samples from 8 plots(2 samples per plot) were used. The major tests are focused on unit weight before and after cut, water content, liquid and plastic limits, sieve and hydrometer analysis etc. The total unit weight(${\rho}_t$) before and after cut are $1.69g/cm^3$ and $1.19g/cm^3$, respectively. Their water contents are 21.0% and 20.5%. The coefficient of uniformity U and coefficient of curvature C obtained from sieve and hydrometer analysis are 125 and 0.42, which mean generally not well graded. On the soil classification by USCS, SM(silty sand or silt-sand mixed soil)is a Key soil, but it seems to be not good for fill material. From the standard proctor test are resulted $1.40{\pm}0.065g/cm^3$ for the unit weight(${\rho}$) in the nature and $1.88{\pm}0.049g/cm^3$ for the optimum proctor unit weight(${\rho}pr$) each. With this to say, it is necessary more powerful compaction work at earth filling, with which this soil reachs enough the ${\rho}pr$, and more earth.

• Journal of the Korean Geosynthetics Society
• /
• v.21 no.1
• /
• pp.11-21
• /
• 2022

In this study, the individual vacuum seepage consolidation method, a new soft ground improvement method, was developed to supplement the conventional suction drain method (individual vacuum preloading method) and the geotechnical behavior was predicted through numerical analysis. If the individual vacuum seepage consolidation method applied, the effect of accelerating settlement and increasing the amount of settlement was high when the aquifer was located in the middle or at the bottom of the layer to the target improvement layer. It was found that the pumping amount in the aquifer does not affect the settlement behavior when it exceeds a certain level. Even vacuum pumping wells were installed in various locations, such as inside or outside of the embankment, the difference in settlement and horizontal displacement was insignificant. In addition, it was predicted that the settlement rate was the fastest and the horizontal displacement (inward) was large when both methods were carried out at the same time. Since this method can reach the target settlement amount very quickly, it was confirmed that it is possible to increase the spacing of vertical drain, thereby securing economic feasibility.