• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.75-83
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• 2002

This paper is to investigate the mechanical characteristics of light-weighted soils (LWS) consisting of expanded polystyrene(EPS), dredged clays and cement by using both uniaxial and triaxial compression tests. The mechanical characteristics of the compressive strength of LWS are analysed with varying initial water contents of dredged clays, EPS ratio, cement ratio, and curing stress. In the triaxial compression state, it is found that the compressive strength of LWS containing EPS is independent on the effective confined stress. As the EPS ratio decreases($A_E$<2%) and cement ratio increases($A_c$>2%), the behavior characteristics of triaxial compressive strength-strain relationship is similar to that of cemented soil which decreases rapidly in compressive strength after ultimate compressive strength. For the applications of LWS to ground improvements which require the compressive strength of up to 200kPa, the optimized EPS ratio and initial water content of dredged clay are estimated to be 3~4% and 165~175%, respectively. Also, the ultimate compressive strength under both triaxial test and uniaxial compression states are almost constant for a cement ratio of up to 2% and then critical cement ratio of this LWS shall be 2%.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.189-196
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• 2002

According to the Korean Design Code for port and harbor facilaties, bearing capacity of rubble mound under eccentric and inclined load is calculated by the simplified Bishop method, and strength parameters are recommended to be c=0.2kg/$\textrm{cm}^2$ and ø=35$^{\circ}$for standard rubble if the compressive strength of parent rock is greater than 300kg/$\textrm{cm}^2$, quoting from research results by Jun-ichi Mizukami(1991), But this facts have never been certified in Korea because there was not large-scale triaxial test apparatus until 2000 in Korea. Firstly in Korea, the large-scale triaxial test (sample diameter, 30cm and height, 60cm) on the rubble originated from porous basalt rock in North-Cheju was accomplished. Then strength parameters for basalt rubble produced in North-Cheju are recommended to be c=0.3kg/$\textrm{cm}^2$ and ø=36$^{\circ}$if the compressive strength of parent rock is greater than 400kg/$\textrm{cm}^2$.

• KCI Concrete Journal
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• v.13 no.1
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• pp.19-25
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• 2001

Based on the orthotropic hypoelasticity formulation, a constitutive material model of concrete taking account of triaxial stress state is presented. In this model, the ultimate strength surface of concrete in triaxial stress space is described by the Hsieh's four-parameter surface. On the other hand, the different ultimate strength surface of concrete in strain space is proposed in order to account for increasing ductility in high confinement pressure. Compressive ascending and descending behavior of concrete is considered. Concrete cracking behavior is considered as a smeared crack model, and after cracking, the tensile strain-softening behavior and the shear mechanism of cracked concrete are considered. The proposed constitutive model of concrete is compared with some results obtained from tests under the states of uniaxial, biaxial, and triaxial stresses. In triaxial compressive tests, the peak compressive stress from the predicted results agrees well with the experimental results, and ductility response under high confining pressure matches well the experimental result. The reinforcing bars embedded in concrete are considered as an isoparametric line element which could be easily incorporated into the isoparametric solid element of concrete, and the average stress - average strain relationship of the bar embedded in concrete is considered. From numerical examples for a reinforced concrete simple beam and a structural beam type member, the stress state of concrete in the vicinity of talc critical region is investigated.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.197-208
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• 1999

The use of high-strength concrete which permits smaller cross sections, reduced dead loads, and longer spans has been getting more popular in tall buildings. However, there has been little research on behavior of high-strength concrete columns laterally reinforced with square ties and subjected to compressive loading. With the addition of transverse reinforcement which lead to triaxial compressive state, ductility behavior of high-strength column member shall be increased. In this study, rational quality and quantity evaluations were made to investigate the ultimate strength and strain ductility by confinement effect of tie reinforced high-strength concrete columns subject to uniaxial loads. Concrete failure theory at the triaxial compressive state and statistical results based on conventional experimental data were applied for this propose. Up to 185 columns, tested under monotonically increasing concentric loading, were evaluated in terms of strength and strain ductility. Analytical results show that confinement stress, maximum compressive strength, and increase of strain equations were developed with the consideration of concrete strength, yield strength, spacing, volumetric ratio, and configurations of tie reinforcement.

• Tunnel and Underground Space
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• v.2 no.2
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• pp.224-236
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• 1992

It is very important to determine the thermo-mechanical characteristics of the rock mass surrounding the repository of radioctive waste and the LPG storage cavern. In this study, Hwasoon-Shist. Dado-Tuff adn Chunan-Tonalite were the selected rock types. Temperature dependence of the mechanical properteis such as uniaxial compressive strength, tensile strength, Young's modulus was investigated by measuring the behaviour of these properties due to the variation of temperature. Also, the characteristics of strength and deformation of these rocks were examined through high-temperature triaxial compression tests with varing temperatures and confining pressures. Important results obtained are as follows: In high temperature tests, the uniaxial compressive strength and Yong's modulus of Tonalite showed a sligth increase at a temperature up to 300$^{\circ}C$ and a sharp decrease beyond 300$^{\circ}C$, and the tensile strength showed a linear decrease with increasing heating-temperature. In high-temperature triaxial compression test, both the failure stress and Young's modulus of Tonalite increased with the increase of confining pressure at constant heating-temperature, and the failure stress decreased at 100$^{\circ}C$ but increased at 200$^{\circ}C$ under a constant confining pressure. In low temperature tests, the uniaxial compressive and tensile strengths and Young's modulus of these rocks increased as the cooling-temperature is reduced. Also, the uniaxial compressive and tensile strengths of wet rock specimens are less than those of dry rock specimens.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.821-832
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• 2008

The hazard warning levels are necessary for the rational design and safety construction of underground space, as mountain and urban tunnel. Sakurai provided the hazard warning levels for assessing the stability of tunnels using the critical strain of rock mass, which is defined as a ratio between uni-axial compressive strength and the Young's modulus. The concept of critical strain guidelines is introduced in this study for the assessment of tunnel safety during excavation. Moreover, in this paper, the critical strain properties of sedimentary rock in Korea has investigated and analysed in detail by Lab. test, as the uniaxial and triaxial compression tests. Finally, critical strain properties of sedimentary rock on uniaxial and triaxial stress condition is discussed the relationship of failure strain values, uniaxial and triaxial compression strengths, confining pressure and Young's modulus.

• Geomechanics and Engineering
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• v.17 no.2
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• pp.215-225
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• 2019

The mechanical behavior of rock is essential to estimate the capacity and long-term stability of $CO_2$ storage in deep saline aquifers. As the depth of reservoir increases, the pressure and temperature that applied on the rock increase. To answer the question of how the confining pressure and temperature influence the mechanical behavior of reservoir rock, triaxial compression experiments were carried out on brine-saturated sandstone at elevated temperature. The triaxial compressive strength of brine-saturated sandstone was observed to decrease with increasing testing temperature, and the temperature weakening effect in strength enhanced with the increase of confining pressure. Sandstone specimens showed single fracture failures under triaxial compression. Three typical regions around the main fracture were identified: fracture band, damaged zone and undamaged zone. A function was proposed to describe the evolution of acoustic emission count under loading. Finally, the mechanism of elevated temperature causing the reduction of strength of brine-saturated sandstone was discussed.

• Journal of the Korean GEO-environmental Society
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• v.14 no.8
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• pp.5-9
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• 2013

In this study, it was examined a strength characteristic of organic acid material that is eco-friendly and low energy as a soil improving material. The object of this study is to analysis of strength changes with observing the clay mixed organic acid material through the unconfined compression strength test and triaxial compression test during 28 days. As a result of the tests, the strength of clay mixed organic acid material is increased when the more ages are prolonged, the more organic acid material mixture ratio growed. Therefore, in grasping the strength improvement effects of clay by organic acid material mixing, it confirmed that organic acid material as soil improving material is effective through unconfined compression strength test and triaxial compression test. Through this test, the definite strength increase is confirmed according to the mixture of the organic acid material and the possibility of soil improvement is also confirmed based on this result. From now on, detailed examination and field test will help closely to definite strength characteristics.

• Structural Engineering and Mechanics
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• v.24 no.2
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• pp.137-154
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• 2006

The reliable pushover analysis of RC structures requires a realistic prediction of moment-curvature relations, which can be obtained by utilizing proper constitutive models for the stress-strain relationships of laterally confined concrete members. Theoretical approach of Mander is still a single stress-strain model, which employs a multiaxial failure surface for the determination of the ultimate strength of confined concrete. Alternatively, this paper introduces a simple and practical failure criterion for confined concrete with emphasis on introduction of significant modifications into the two-parameter Drucker-Prager model. The new criterion is only applicable to triaxial compression stress state which is exactly the case in the RC columns. Unlike many existing multi-parameter criteria proposed for the concrete fracture, the model needs only the compressive strength of concrete as an independent parameter and also implies for the influence of the Lode angle on the material strength. Adopting Saenz equation for stress-strain plots, satisfactory agreement between the measured and predicted results for the available experimental test data of confined normal and high strength concrete specimens is obtained. Moreover, it is found that further work involving the confinement pressure is still encouraging since the confinement model of Mander overestimates the ultimate strength of some RC columns.

• Tunnel and Underground Space
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• v.9 no.3
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• pp.221-229
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• 1999

Parameters of failure criteria, compressive strength and elastic modulus are most important for design and stability analysis of rock structure using numerical analysis. In this study, it suggests that the application of input data for numerical analysis by the literature study and the result of the 150 sets of triaxial compressive test. There was much different between parameters of failure criterion suggested by Hoek-Brown and parameters resulted from the analysis using 150 sets of triaxial compressive test. But the converting equations of compressive strength have had an interrelation with RMR. However, the converting of elastic of elastic modulus were different as chosen of equation, and the equation by Nicholson et at was more useful than others.