• Geotechnical Engineering
• /
• v.2 no.1
• /
• pp.55-66
• /
• 1986

Considering the effects of confining pressure, initial shear stress, cyclic stress ratio and number of loading cycles, cyclic triaxial tests are carried out to clarify the soil dynamic properties such as shear modulus and value of material damping of clay under undrained cyclic loading conditions. The results show that no obvious dependency on initial shear stress and effective confining stress are recognized in the shear modulus and damping ratio plotted versus strain. However, the shear modulus decreases and the damping ratio increases with increasing axial strain. When compared with others, it is also revealed that the shear moduli are distributed within the range curves obtained using empirical equations derived by Marcuson et al. (3) and Kokusho et al. (4), and damping ratios are distributed between the curves obtained by Kokusho et al. (4) and Ishihara et al. (9).

• Geomechanics and Engineering
• /
• v.18 no.4
• /
• pp.427-437
• /
• 2019

Waste materials are being produced in huge quantities globally, and the usual practice is to dump them into legal or illegal landfills. Recycled tiles (RT) are being used in soil stabilisation which is considered as sustainable solution to reduce the amount of waste and solve the geotechnical problems. Although the stabilisation of soil using RT improved the soil properties, it could not achieve the standard values required for construction. Thus, this study uses 20% RT together with low cement content (2%) to stabilise soft soil. Series of consolidated undrained triaxial compression tests were conducted on untreated and RT-cement treated samples. Each test was performed at 7, 14, and 28 days curing period and 50, 100, and 200 kPa confining pressures. The results revealed an improvement in the undrained shear strength parameters (cohesion and internal frication angle) of treated specimens compared to the untreated ones. The cohesion and friction angle of the treated samples were increased with the increase in curing time and confining pressure. The peak deviator stress of treated samples increases with the increment of either the effective confining pressures or the curing period. Microstructural and chemical tests were performed on both untreated and RT-cement treated samples, which included field emission scanning electron microscopic (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and energy dispersive X-ray spectrometer (EDX). The results indicated the formation of cementation compounds such as calcium aluminium hydrate (C-A-H) within the treated samples. Consequently, the newly formed compounds were responsible for the improvement observed in the results of the triaxial tests. This research promotes the utilisation of RT to reduce the amount of cement used in soil stabilisation for cleaner planet and sustainable environment.

• Geotechnical Engineering
• /
• v.13 no.2
• /
• pp.17-28
• /
• 1997

In this study sodium chloride solution is employed for chemicals, and several cylindrical triaxial tests are performed on the sand-bentonite mixtures saturated with sodium chloride solution. Deformation(elastic modulus, E) and strength(cohesion, c', and angle of friction, f') parameters are obtained from the triaxial tests as functions of confining pressure and sodium chloride solution concentrations. The results here indicate an increase in the value of effective cohesion with increase in the concentration of NaCl solution, which can be explained by using the Gouy-Chapman model. The value of the effective angle of shearing resistance does not show significant change with the increase in concentration of NaCl solution. The Young's modulus also increases with the increase in concentration of NaCl solution.

• Structural Engineering and Mechanics
• /
• v.18 no.6
• /
• pp.769-790
• /
• 2004

The compressive behavior up to failure of short concrete members reinforced with fiber reinforced plastic (FRP) is investigated. Rectangular cross-sections are analysed by means of a simplified elastic model, able also to explain stress-concentration. The model allows one to evaluate the equivalent uniform confining pressure in ultimate conditions referred to the effective confined cross-section and to the effective stresses in FRP along the sides of section; consequently, it makes it possible to determine ultimate strain and the related bearing capacity of the confined member corresponding to FRP failure. The effect of local reinforcements constitute by single strips applied at corners before the continuous wrapping and the effect of round corners are also considered. Analytical results are compared to experimental values available in the literature.

• Geomechanics and Engineering
• /
• v.8 no.1
• /
• pp.1-15
• /
• 2015

This paper presents a series of conventional undrained triaxial compression tests conducted to determine the effect of both tire crumbs and cement addition on Narli sand specimens. The tire crumb contents and cement contents were 3%, 7%, 15%; and 1%, 3%, 5% by dry weight of the sand specimens respectively. Specimens were prepared at about 35% relative density, cured during overnight (about 17 hours) for artificially bonding under a 100 kPa effective stress (confining pressure of 500 kPa with a back pressure of 400 kPa), and then sheared. Deviatoric stress-axial strain, pore water pressure-axial strain behavior, and Young's modulus of the specimens at various mixture ratios of tire crumb/cement/sand were measured. Test results indicated that the addition of tire crumb to sand decreases Young's modulus, deviatoric stress and brittleness, and increase pore water pressure generation. The addition of cement to sand with tire crumbs increases deviatoric stress, Young's modulus, and changes its ductile behavior to a more brittle one. The results suggest that specimen formation in the way used here could reduce the tire disposal problem in not only economically, and environmentally, but also more effectively beneficial way for some geotechnical applications.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.10
• /
• pp.57-64
• /
• 2007

Since matric suction of unsaturated soil was related to soil and ground water contaminations, it is very important to analyze its mechanism that was represented by shear characteristics. In three phases of soil, a little air makes the condition of unsaturated soil on contract or shrinkage surface between water and air. Capillarity and suction in pore of unsaturated soil cause surface tension and surface force so it makes negative pore water pressure and increases effective stress as a result. Therefore, negative pore water pressure in partially saturated soil affects the soil structure and degree of saturation and it is important to evaluate accurately unsaturate flow and behavior. In this study, the shear strength characteristics of the seven sandy soils were investigated using consolidated drained triaxial tests with special emphasis on the effects of the negative pore pressure and the matric suction. These tests involved shearing under either a constant net confining pressure and varying matric suction or under a constant matric suction and varying net normal stress.

• Journal of the Korean GEO-environmental Society
• /
• v.11 no.8
• /
• pp.5-14
• /
• 2010

Recent researches on the behavior of gravelly soils have been focused mainly on the relative density or on the gravel content. And some researchers presented the liquefaction behavior based on the relative density whereas others based on the gravel content of gravelly soil. However the relative densities vary with gravel content and relative density is not enough to fully express the behavior of gravelly soils. Therefore in this research state parameter which considers void ratio and effective confining pressure is introduced and Steady State Line(SSL) of gravelly soils for various gravel content are determined by undrained triaxial tests in order to express the behavior of gravelly soils. From the research the position of SSL moved downward with gravel content. And the same density of soil showed dense sand behavior or loose sand behavior depending upon the confining pressure. Especially relative density 80% of gravelly soil showed loose sand behavior under high confining pressure. However the gravelly soils with similar state parameters showed similar stress behaviors. It can bee seen that state parameter is useful tool to evaluate undrained behavior of gravelly soils. Also state parameter and undrained strength showed good correlations.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.3 no.2
• /
• pp.109-117
• /
• 1983

Dynamic shear modulus of the compacted clayey soil was determined by the resonant column test to study the parametric effects of confining pressure, shear strain amplitude, molding water content, compaction energy, void ratio and the degree of saturation. The effect of each of these parameters on the dynamic shear modulus found to be significant and can be explained in terms of the changes in soil by compaction. Dynamic shear modulus of the compacted soil is increased significantly by compaction and compaction at the dry side of the optimum moisture content is much more effective. It is also found that the dynamic shear modulus showes a good correlation to the static shear strength of the compacted soil. Therefore the dynamic shear modulus of the compacted soil for a certain confining pressure may be obtained ea8i1y from the unconfined compression strength.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.2
• /
• pp.5-14
• /
• 2010

In this study, cyclic triaxial tests were performed under anisotropically consolidated condition by using irregular earthquake loading to consider in-situ condition and seismic wave. Jumunjin sand with a relative density 50 percent was used in the tests. The consolidation pressure ratio (K) was changed from 0.5 to 1.0. The Ofunato and Hachinohe wave were applied as irregular earthquake loadings and liquefaction resistance strengths of each specimen were estimated from the excess pore water pressure (EPWP) ratio. As a results of the cyclic triaxial tests, EPWP ratio increased with increased K value. It shows that isotropically consolidated sand is more susceptible to liquefaction than anisotropically consolidated sand under equal confining pressure and dynamic loadings. From the test results, the relationship between K and EPWP ratio normalized by effective confining pressure and deviator stress was proposed. And a new factor which corrects the liquefaction resistance strength for the in-situ stress condition is proposed.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.10a
• /
• pp.605-610
• /
• 2002

The purpose of this study is to develop an analytic model which can describe the behavior or concrete compressive member strengthened by CFS(Carbon Fiber Sheet) with various cross-sectional shapes such as circular. square, and octagonal and various laminate angles. The failure criterion of laminated CFS is based on Tsai-Wu failure criterion. The stress strain model of confined concrete compressive member is based on an equation proposed by Mander. The effective lateral confining pressure is considered and modified according to various cross-sectional shapes. Octagonal cross-section shows the best results in the aspect of ductility, while circular does in compressive strengthening effects. In addition, [0/0/0/0] laminate in which the direction of fiber is parallel to the direction of principal stress shows the superior strength and ductility than other laminates. The analytic results show that strength and ductility of the analytic model depend on the cross-sectional shapes as well as the laminate angles.