• Geomechanics and Engineering
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• v.21 no.6
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• pp.527-536
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• 2020

An elastic-plastic solution for cavity expansion problem considering strength degradation, undrained condition and initial anisotropic in-situ stress is established based on the Tresca yield criterion and cavity expansion theory. Assumptions of large-strain for plastic region and small-strain for elastic region are adopted, respectively. The initial in-situ stress state of natural soil mass may be anisotropic caused by consolidation history, and the strength degradation of soil mass is caused by structural damage of soil mass in the process of loading analysis (cavity expansion process). Finally, the published solutions are conducted to verify the suitability of this elastic-plastic solution, and the parametric studies are investigated in order to the significance of this study for in-situ soil test.

• Geomechanics and Engineering
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• v.16 no.6
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• pp.599-608
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• 2018

This study investigates the feasibility of adopting the results of the UC (unconfined compression) test to assess the total cohesion of the unsaturated soil. A series of laboratory tests were conducted on samples of unsaturated lateritic soils of northern Taiwan. Specifically, the unconfined compression test was combined with the pressure plate test to obtain the unconfined compression strength and its matric suction of the samples. Soil samples were first compacted at designated water content and then subjected to the wetting process for saturation and the subsequent drying process to its target suction using the apparatus developed by the authors. The correlations among the matric suction, the unconfined compression strength and the total cohesion were studied. As a result, a simplified method to estimate the total cohesion using the unconfined compressive strength is suggested. The calculated results compare reasonably with the unsaturated triaxial test results. Current results show good performance; however, further study is warranted.

• Journal of Biosystems Engineering
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• v.31 no.1 s.114
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• pp.24-32
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• 2006

Compaction is becoming a greater concern in crop production and the environment because it can have deleterious effects on growing conditions that are difficult to remediate. Because compaction can vary considerably from point to point within a field, and also from depth to depth within the soil profile, it is important to consider quantification and management of the spatial and vertical variability in soil compaction when developing an overall site-specific crop management plan. In this paper, the importance of soil compaction, techniques for quantification of its variability, and the concept of site-specific tillage are examined. Methods and systems to detect within-field variation in soil strength as a surrogate measure of soil compaction and related soil properties are also compared and discussed. Quantification of variability in soil compaction and site-specific compaction management was motivated recently, and sensors and control systems are still under development. Future study will need to address a number of issues related to understanding and applying the sensor measurements.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.594-598
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• 1999

To analyze the characteristics of unconfined compressive strength of reinforced soil bricks made of clayey and sandy mixed with cement, lime, staple fiber and their combinatioin , a series of unified comparessive tests was performed. The resutls are summarized as follows ; 1) Reinforcing effect of reinforced clayed soil and that of soil brick of sandy soil mixed with cement and staple fiber is 8 times greater than no reinforced sandy sol. Therefore, the reinforcing effect seems to be greater in sandy soil than in clayey soil . 2) Lime shows a negative reinforcing effect in clayed soil but a little reinforcing effect in sandy soil. 3) It is appeared that strain at failure of soil brick reinforced with staple fiber is greater than that of unreinforced brick regrardless of soil's type.

• Journal of the Korean GEO-environmental Society
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• v.13 no.6
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• pp.19-26
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• 2012

In this study, geotechnical tests including unconfined compression test were carried out to evaluate the ground improvement effect of the hardening agent, which has been developed by using inter-chemical reactions between slag, fly ash, phosphogypsum and bypass dust on the weathered granite soil and dredged marine clay. Test results show that the strength of weathered granite soil mixed with hardening agent B-2, which uses phosphogypsum as an activator, is higher than that of B-1, which uses bypass dust as an activator. Strengths of B-1 & B-2 hardening agent mixed soil show only 44%~60% of strength of OPC(Ordinary Portland Cement, OPC) mixed soil. However, since B-1 and B-2 agents are made of industrial by-products, they seem economically more effective than ordinary portland cement as well as other present hardening agents. Test results on dredged marine clay show that unconfined compression strength increases with amount of agent and curing days. Unconfined compression strength of 14% B-1 agent mixed soil increases linearly with curing days and reaches only 40% of OPC mixed soil. While unconfined compression strength of 14% B-2 agent mixed soil increases exponentially and reaches 133% of OPC mixed soil. Relationship between deformation modulus and unconfined compression strength of B-1 and B-2 mixed soil can be expressed as $E_{50}=(20{\sim}47)_{qu,28}$, which is similar with lower limit of OPC mixed dredged marine clay.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.6
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• pp.159-167
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• 2012

In the present study, an investigation has been made on the application of cement-bentonite soil mixtures as the countermeasure against leachate produced by buried animal carcasses. For this purpose, the strength characteristics of the cement-bentonite soil mixtures mixed with geotextile and metakaolin. After the mixtures with different contents of the cement (0 %, 10 %), bentonite (0 %, 5 %, 10 %, 15 %, 20 %), and weathered soil (100 %, 95 %, 90 %, 85 %, 80 %) were prepared, metakaolin and geotextile were added with different contents (metakaolin : 0 %, 5 %, 10 %, 15 %, 20 % of the cement weight; geotextile : 0 %, 0.5 %, 1 %, 1.5 %, 2 %). Experimental results suggested that the early strength of the mixture increases due to the pore filling, the hydration acceleration, and the pozzolan reaction when metakaolin of 5~10 % of the cement weight was added. In addition, the compressive strength increase when 0.5~1 % geotextile contents were added, and the above these contents, the rate of strength increase was gradually decreased because of the fibrous tangles.

• Journal of the Korean Geotechnical Society
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• v.20 no.4
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• pp.5-13
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• 2004

Strength and compressibility characteristics of Light-Weighted Foam Soil (LWFS) are experimentally investigated in the paper. LWFS is composed of the dredged soils, cement and air foam to reduce unit-weight and to increase compressive strength. For these purposes, both unconfined compression tests and triaxial compression tests are carried out fer artficially prepared specimens of LWFS with various initial water contents, cement contents, mixing ratio of silty dredged soils and different confining stresses. The experimental results of LWFS indicate that the stress-strain relationship and the compressive strength are strongly influenced by cement contents rather than intial water contents of the edged soils. In this paper, the normalizing scheme considering the ratio of initial water contents, cement contents, and air foam contents has been proposed to evaluate the relationship between compressive strength of LWFS and a normalized factor.

• Journal of the Korean Geotechnical Society
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• v.19 no.3
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• pp.75-82
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• 2003

This paper presents the results of a study that was performed to evaluate fronds of shear strength parameters in stabilization of unbound soil-aggregate systems based on the theory of unsaturated soil mechanics. Two important shear strength parameters, effective cohesion and effective angle of internal friction were estimated by the proposed approach using the results from suction measurements and unconfined compressive strength test. In addition, the effect of different addition rates of stabilizing agent was compared. Due to the stabilization process, an increase in suction potential on engineering properties of geomaterials was observed by using dielectric constant measurements. In conclusion, the results from this study show that the proposed approach can be simply used for predicting shear strength parameters of the stabilized geomaterials.

• Geomechanics and Engineering
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• v.17 no.2
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• pp.195-206
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• 2019

The gypsiferous soils are significantly sensitive to moisture and the water has a severe destructive effect on them. Therefore, the effect of lime and silica fume addition on their mechanical properties, when subjected to water, is investigated. Gypsiferous soil specimens were mixed with 1, 2 and 3% lime and 1, 3, 5 and 7% silica fume, in terms of the dry weight of soil. The specimens were mixed at optimum moisture content and cured for 24 hours, 7 and 28 days. 86 specimens in the sizes of unconfined compression strength test mold were prepared to perform unconfined compressive strength and durability tests. The results proved that adding even 1% of each of these additives can lead to a 15 times increase in unconfined compressive strength, compared with untreated specimen, and this increases as the curing time is prolonged. Also, after soaking, the compressive strength of the specimens stabilized with 2 and 3% lime plus different percentages of silica fume was considerably higher than before soaking. The durability of the treated specimens increased significantly after soaking. Direct shear tests showed that lime treatment is more efficient than silica fume treatment. Moreover, it is concluded that the initial tangent modulus and the strain at failure increased as the normal stress of the test was increased. Also, the higher lime contents, up to certain limits, increase the shear strength. Therefore, simultaneous use of lime and silica fume is recommended to improve the geotechnical properties of gypsiferous soils.

• Geomechanics and Engineering
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• v.38 no.2
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• pp.165-177
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• 2024

Liquefaction phenomenon refers to a phenomenon in which excess pore water pressure occurs when a dynamic load such as an earthquake is rapidly applied to a loose sandy soil ground where the ground is saturated, and the ground loses effective stress and becomes liquid. The laboratory repetition test for liquefaction evaluation can be performed through a repeated triaxial compression test and a repeated shear test. In this regard, this study attempted to evaluate the effects of the relative density of sand on the liquefaction resistance strength according to particle size distribution using repeated triaxial compression tests, and additional experimental verification using numerical analysis was conducted to overcome the limitations of experimental equipment. As a result of the experiment, it was confirmed that the liquefaction resistance strength increased as the relative density increased regardless of the classification of soil, and the liquefaction resistance strength of the SP sample close to SW was quite high. As a result of numerical analysis, it was confirmed that the liquefaction resistance strength increased as the confining pressure increased under the same relative density, and the liquefaction resistance strength did not decrease below a certain limit even though the confining pressure was significantly reduced at a relatively low relative density. This is judged to be due to a change in confining pressure according to the depth of the ground. As a result of analyzing the liquefaction resistance strength according to the frequency range, it was confirmed that there was no significant difference from the laboratory experiment results in the basic range of 0.1 to 1.0 Hz.