• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.253-258
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• 2002

In this study the confining pressure dependancy of internal friction angle of rock materials are discussed based on the results of a series of large triaxial tests under consolidated-drained condition. The rock materials tested are two kinds of grain-size distribution ;one is well graded, the other poorly graded(a uniform distribution). The obtained results shows that the internal friction angle of rock materials decreases more sharply in low stress level than in high stress level, and the test constants A and b in De Mello's failure criterion on rockfill materials are A =0.683∼l.584, b=0.712∼l.015 for the well graded and A=1.145∼l.523, b=0.788∼0.880 for the poorly graded.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.7 no.2
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• pp.46-51
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• 2004

In this paper, reinforcement of soil shear strength by bamboo(substitute materials simulating a root system) are evaluated by soil strength parameters(apparent cohesion(c) and internal friction angle(tan${\Phi}$)), using simple shear tester which clearly depicts shear deformation and controls soil suction. The results show that the internal friction angle does not change under various soil suction conditions but the apparent cohesion, which reach a peak in suction of 45cm$H_2O$ near critical capillary head, is effected by soil suction. And the reinforcement of soil strength by bamboo are expressed by apparent cohesion more than internal friction angle. In addition the increment of apparent cohesion by bamboo reached a peak in suction 45cm$H_2O$ too.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.2
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• pp.252-261
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• 1988

Through the careful interpretation of the results of the cutting tests carried out in this study, it is found that under the cutting conditions when the internal shear of the chips take place the cutting can be treated essentially as a steady state problem. A new shear angle equation has been developed employing the conditions of force and moment equilibrium about the tool edge and the stress distribution model suggested by Zorev.The equation contains the chip-tool contact length C and stress distribution index n as important parameters.

• Magazine of the Korean Society of Agricultural Engineers
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• v.23 no.3
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• pp.96-104
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• 1981

In order to investigate the characteristics of the shear strength of the unsaturated cohesive soils which has mean characters of sand and clay widely used for banking, I selected soil samples from An-sung district and, against it, performed direct shear test and unconfined compression test changing grain size, compaction energy and moisture content and also performed triaxial compression test under optimum moisture content. The results are as follows; 1.As the passing percent of the No. 200 sieve increased from 23.6% to 56.1%, cohesion increased from 0. 202kg/cm2 to 0. 398kg/cm2 under the direct shear test and from 0.38 kg/cm2 to 1. 05kg/cm2 under the tria4al compression test, internal friction angle decreased from 44. 78$^{\circ}$ to 34. 34$^{\circ}$ under the direct shear test and from 31. 88$^{\circ}$ to 13. 31$^{\circ}$ under the triaxial compression test. 2.Cohesion showed it's maximum value around OMC and internal friction angle showed a tendency to increase according to the decrease of water content but it's increasing ratio was relatively slow. 3.Decreasing ratio of cohesion and internal friction angle was relatively sensitive according to the decrease of compaction energy. 4.The smaller of the vertical stress and the coarser of the grain size of samples, changing of the volume showed a tendency to increase and as the increase of water content, the shear displacement (dh) at failure shear stress ($\tau$f) showed maximum and the $\tau$f-dh curve was gentle. 5.To synthesize the results of the direct shear test and the triaxial compression test, cohesion showed higher under the triaxial compression test and internal friction angle showed a tendeney to appear higher under the direct shear test. It seems that we can get correspondent results by removing the side friction of mold with soils and adjusting the vertical stress and shearing speed under the direct shear test.

• Magazine of the Korean Society of Agricultural Engineers
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• v.33 no.4
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• pp.105-120
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• 1991

This study was performed to investigate the minimum safety factor of embankment in consideration of seismic coefficient by the psuedo-static analysis The variables were cohesion, the internal friction angle, angle of slope, height of seepage, height of embankment, depth of replacement The results obtained were compared with those by Fellenius method, simplified Bishop method and Janbu method. The results were summarized as follows: 1.The increasing rate of the minimum safety factor with the increasing of cohesion appeared larger in Fellenius method and Bishop method than in Janbu method. And that with the increasing of the internal friction angle appeared the lowest value in Janbu method. The minimum safety factor was influenced larger on the internal friction angle than on cohesion. 2.The variation of the minimum safety factor with the height of seepage at 0m and 5 m was nearly similar to Fellenius method, Bishop method and Janbu method. On the other hand, it was decreased suddenly at 25 m. 3.The minimum safety factor with the height of embankment was decreased remarkably under 10 m with the increasing of seismic coefficient. But, it was decreased slowly more than 10 m. As the height of embankment was low, the influence of cohesion appeared larger. 4.In heigher case of the depth of replacement, the phenomenon of reduction of the minimum safety factor appeared remarkably with seismic coefficient increased. And in lower case of the depth of replacement, the minimum safety factor was similar in Fellenius method and Bishop mehtod. But it appeared larger in Bishop method and Janbu method than in Fellenius method with the depth of replacement increased. 5.As the cohesion and the internal friction angle were large, the phenomenon of reduction of the minimum safety factor with the increasing of seismic coefficient appeared remarkably. Also, the influence of seismic coefficient in minimum safety factor appeared larger with the soil parameter increased. 6.When the seismic coefficient was considerated, investigation of the structural body on the slope stability appeared profitably in Fellenius method and Janbu method than in Bishop method.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.265-270
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• 2002

Dilatancy is a unique characteristics of granular materials showing the tendency to change volume upon shearing. In this study large triaxial tests were peformed for both the well graded rock and the poorly graded rock. And the shear strength of rockfill materials considering dilatancy is evaluated based on the test results. For the rock materials of this study the contribution of dilatancy in the maximum internal friction angle is as much as -6.0%∼3.0% of the internal friction angle measured at peak

• Journal of the Korean Geotechnical Society
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• v.32 no.3
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• pp.15-27
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• 2016

In this study, a series of triaxial compressive strength tests were conducted for basaltic intact rocks sampled in the northeastern onshore and offshore, southeastern offshore and northwestern offshore of Jeju Island. Hoek-Brown constants $m_i$ were estimated from the results of the triaxial compression tests, and the properties of the Hoek-Brown constants $m_i$ were investigated. In addition, the cohesion and internal friction angle, strength parameters of Mohr-Coulomb failure criterion, obtained from the results of the triaxial compression tests were compared and analyzed with those estimated from Hoek-Brown failure criterion, respectively. As results, it was found that the Hoek-Brown constant $m_i$ is deeply related to the internal friction angle. As the internal friction grows, the Hoek-Brown constant $m_i$ increases exponentially. The cohesions estimated from the Hoek-Brown failure criterion, on average, are approximately 24% higher than those obtained from the Mohr-Coulomb failure criterion. The internal friction angles estimated from the Hoek-Brown failure criterion are similar to those obtained from the Mohr-Coulomb failure criterion.

• Geomechanics and Engineering
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• v.22 no.2
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• pp.165-171
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• 2020

Laboratory determination of strength and deformation behavior of clean sands and gravels has always been challenging due to the difficulty in obtaining their undisturbed samples. An alternative solution to this problem is to develop correlations between mechanical properties of cohesionless soils and their gradation characteristics. This study presents database of 3 natural sands with 11 varying particle size gradation curves to allow investigating relationships between mean particle size, maximum and minimum void ratio, relative density and shear strength of the test soils. Direct shear tests were performed at relative densities of 50, 75 and 95% to explore the effects of gradation and density on the angle of internal friction of the modeled sand samples. It is found that the mean grain size D₅₀ bears good correlations with void ratio range (e_max - e_min) and peak angle of internal friction 𝜙'_peak. The generated regression models are in good agreement with published literature and can be considered as reliable for natural sands in Pakistan. These empirical correlations can save considerable time and efforts involved in laboratory and field testing.

• Geotechnical Engineering
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• v.14 no.4
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• pp.103-116
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• 1998

To estimate pure shear strength, 150 sets of triaxial test data were analyzed. The proportional coefficient of shear strength($I_c$) at zero normal stress was nonlinearly decreased as failure coefficient m increases, while the internal friction $\phi_0$ at zero normal stress was nonlinearly increased. The ratio of shear strength $(c/\phi_0)$was inversely proportional to the ratio of the internal friction angles$(\phi/phi_0)$ The shear strength decreased as m increased, while internal friction angle increased. And uniaxial strength was proportional to $c,\phi$ Regression analysis showed that shear strength strongly affects m and $\sigma_c$ The proportional coefficient of shear strength was nonlinearly increased with RMR, while the internal friction angle $(\phi}$was linearly decreased.

• Geomechanics and Engineering
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• v.22 no.5
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• pp.397-414
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• 2020

In this paper, practical predictive models for soil shear strength parameters are proposed. As cohesion and internal friction angle are of essential shear strength parameters in any geotechnical studies, we try to predict them via artificial neural network (ANN) and neuro-imperialism approaches. The proposed models was based on the result of a series of consolidated undrained triaxial tests were conducted on reinforced sandy soil. The experimental program surveys the increase in internal friction angle of sandy soil due to addition of polypropylene fibers with different lengths and percentages. According to the result of the experimental study, the most important parameters impact on internal friction angle i.e., fiber percentage, fiber length, deviator stress, and pore water pressure were selected as predictive model inputs. The inputs were used to construct several ANN and neuro-imperialism models and a series of statistical indices were calculated to evaluate the prediction accuracy of the developed models. Both simulation results and the values of computed indices confirm that the newly-proposed neuro-imperialism model performs noticeably better comparing to the proposed ANN model. While neuro-imperialism model has training and test error values of 0.068 and 0.094, respectively, ANN model give error values of 0.083 for training sets and 0.26 for testing sets. Therefore, the neuro-imperialism can provide a new applicable model to effectively predict the internal friction angle of fiber-reinforced sandy soil.