• Journal of the Korean Geosynthetics Society
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• v.5 no.1
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• pp.33-38
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• 2006

Large-scale direct shear tests were conducted in order to evaluate both the shear strength of crushed stone itself and the interface shear strength between crushed stone and geotextile. Total three types of geotextile (i.e. one woven geotextile and two nonwoven geotextiles) were used in the experimental program, considering two different values for the unit weight of crushed stone. Total fifteen tests were conducted in this study. It has been found from the experimental results that the friction angles of crushed stone itself were $47^{\circ}$ and $57^{\circ}$ under the unit weights of crushed stone being $1.4t/m^3$ and $1.5t/m^3$, respectively. Interface friction angle between nonwoven geotextile and crushed stone showed $39^{\circ}$ for type A indicating an efficiency of 83% and $42^{\circ}$ for type B indicating an efficiency of 89%. Similarly, interface friction angle between woven geotextile and crushed stone showed $39^{\circ}$ indicating an efficiency of 83%.

• Geotechnical Engineering
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• v.12 no.2
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• pp.107-114
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• 1996

A series of shear tests is performed to measure friction coefficients of the interface between different reinforcements and weathered granite soils. The reinforcements tested are smooth steel strip, Paraweb(friction tie) and geotextile with rough surface, while the weathered granite soils are composed of different, grain size distribution. Soils are compacted with the energy of 95% modified AASHTO and fully saturated before testing to simulate the worst site condition. Because of characteristics of the direct shear apparatus, shear strength is obtained in terms of drained condition. Test results show that the more fines the soils contain, the larger ratio of friction coefficient ($\mu=\frac{tan{\delta}}{tan{\Psi}}$) is obtained. Also the ratios are much higher for the Friction tie and the geotextile compared to the smooth steel strip. Those suggest that even weathered granite soils with 36% fines are possible to use as backfill of reinforced earth structures for the two reinforcements when a drainage system is provided.

• Tunnel and Underground Space
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• v.28 no.6
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• pp.584-595
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• 2018

This study conducted direct shear test on about 290 sorts of materials such as sandy soil, clayey soil and gravely soil to present proper standard on shear strength of soil. Shear strength of soil in large scale tends to show that angle of internal friction increases as sand contents grow and it ranges $23.5^{\circ}{\sim}34.9^{\circ}C$ with cohesion of 2.0 kPa~15.7 kPa. Elastic modulus was visibly distinct by load, and which increased approximately 80% as vertical load grows. Angle of internal friction arranging $15.0^{\circ}{\sim}28.6^{\circ}$ on clayey soil decreased as clay contents rises and cohesion increase in regular scale. Elastic modulus tends to increase initial elastic modulus with almost same growing rate. While angle of internal friction on gravely soil indicates $29.9^{\circ}{\sim}36.7^{\circ}$ which hardly shows distinctive features. According to test in detail, cohesion of SW (well-graded sand), SP (poorly-graded sand), SC (clayey sand) and SM (silty sand) indicates value by 94%, 78% and 59% comparing to SC, SW and SP respectively. Angle of internal friction of ML (low-liquid limit silt) and CL (low-liquid limit clay) appears almost same features, and MH (high-liquid limit silt) despite of 88% value of ML. Cohesion among them varies with similar growing rate.

• Geotechnical Engineering
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• v.11 no.4
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• pp.99-110
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• 1995

In this study, friction angles on the surface of vertical rigid ground anchor in normally consolidated dry sand were measured by model pullout tests in laboratory. Friction angles were obtained from the normal and shear stresses measured along depth of the anchor stir face by attaching several 2-dimensional load cells. Model tests were conducted under the plane strain state and axial symmetric state. From the results of tests, it was concluded that the maximum friction angle on the anchor surface coincides nearly with the maximum angle of stress obliquity on the plane of zero-extension direction obtained by plane strain compression test. This result was made with regard to the strength anisotropy and stress dependency of sand. It showed that when angle of shear resistance of the sand is applied to the friction angle of the anchor surface, the design capacity could be less than the applied force, thus making the anchor unsafe.

• Journal of the Korean Geosynthetics Society
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• v.2 no.1
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• pp.39-45
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• 2003

The most important part in the earth reinforcement is the interface between soil and the reinforcement. Shear strength and shear behavior in this interface make a great role relating to the reinforcement effect. This paper presents 2 kinds of direct shear test methods. one is the strain free shear test, called 'free method', that is performed by the free condition of allowing tensile strain. The other is the strain fix shear test, called 'fixed method', that is performed by the fixed condition of not allowing tensile strain. Two reinforcements were used such as nonwoven geotextile and geogrid. That is, interfaces are composed of geogrid/sand and geotextile/sand. From the test results it shows us that the fixed method had a greater friction angle and a smaller peak shear strain than those of the free method. Residual stress of the fixed method was bigger than that of the free method but the residual stress ratio was vice versa.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.357-366
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• 2021

Shear behavior dependent on the shape and roughness of rock joints can greatly influence the stability of the ground and rock structures. The efficient design of rock structures requires understanding of the shear behavior due to joints and accurate calculation of the shear strength. This work reports numerical shear tests using PFC2D on No. 1 (JCR-1), with smooth joints, and No. 7 (JRC-7) and No. 9 (JRC-9), with relatively rough joints, for the 10 shapes of standard joint profiles proposed by Barton and Choubey (1977). The aim was to investigate the shear behavior of rock joints with respect to their roughness. The results show the maximum shear stress to be about 3.2 to 5.0 times greater in the rougher JRC-7 and JRC-9 joints than in smoother JRC-1. The maximum shear displacement was approximately 4.1 to 5.8 times greater at the first normal stress than at the second. The rougher joints showed friction angles of the rock joints that were approximately 1.8 to 3.9 times greater than that in the smooth joint. Overall, increasing the rock joint roughness increased the maximum shear stress and friction angle.

• Science of Emotion and Sensibility
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• v.14 no.2
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• pp.191-196
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• 2011

Fabric extraction force measured through nozzle tester reflects a comprehensive fabric handle. Nozzle tester takes advantage of low cost, and simple and fast operating procedure compared with KES system. The paper is to develop the semi-emprical equation for assessment of the fabric handle measured with nozzle tester on the basis of friction law. The variables considered in the equation arc fabric's frictional coefficient and drape coefficient which is determined in terms of fabric bending length and shear strain. The experiment of 12 different cotton and polyester fabrics and comparisons between experimental and theoretical results were conducted. Fabrics of high frictional coefficients, high bending length, and low shear strain showed high fabric handle forces (low handle values). The handle forces predicted from the equation agreed well with those measured, which indicates that the equation can be used to objectively evaluate fabric handle with respect to fabric's own properties and also provide an information for fabric design to improve the handle performance.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.6 s.46
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• pp.21-30
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• 2005

In this study, a seismic design methodology for friction dampers based on the story shear force distribution of an elastic building structure is proposed. First, using two normalization methods for the slip-load of a friction damper, numerical analyses of various single-degree-of-freedom systems are peformed. From those analyses, the effect of the slip-load and the brace stiffness was investigated and the optimal silliness ratio of the brace versus original structure was found. Second, from the numerical analysis for five multi-story building structures with different natural frequency and the number of story, reasonable decision method for the total number of installation floor, location of installation and distribution of the slip-loads are drawn. In addition, an empirical equation on the optimal number of installation floor is proposed. Finally, the superiority of the proposed method compared to the existing design method is verified from the numerical analysis using real earthquake data.

• Journal of the Korean GEO-environmental Society
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• v.8 no.1
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• pp.49-55
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• 2007

In order to utilize treads of waste tire as reinforcement material it is necessary to know the interface friction angle between tread surfaces and soil and tensile strength of connection joint of tire treads. In this research large direct shear tests were performed to get the interface friction angle between the inner and outer surfaces of treads and soil for different degree of compaction. From the large direct shear tests, the ratio of interface friction angle to the shear friction angle of sand, ${\delta}/{\phi}$, were 1.06 in outside surface of tire tread and 0.93 in inside surface of tire tread. For weathered granite soil the ratio of interface friction angle was 0.98 and 0.92 for outside and inside of tread, respectively. Also tensile tests were performed using universal testing machine for the connection joint of treads and Tirecell units using bolts. The tensile strength of connection joint increased with the number of bolts and with the sizes of washers. Connection by polypropylene ropes showed lower strength than those of bolts.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.1910-1920
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• 1993

An experimental study to investigate the unconventional chip formation called triangulation of chip in cutting with a SPRT (self-propelled rotary tool) is performed using acoustic emission (AE) signal analysis. In doing that, a quantitative model of the AE RMS signal in triangulation with a SPRT is first developed. The predicted results from this model show good correlation between the AE RMS signal and the general characteristics of triangular chip formation. Then, effects of various process parameters such as cutting conditions (cutting speed, depth of cut, oblique angle and normal rake angle) and the work material properties on the chip formation in cutting with a SPRT are explored. Special attention is paid to the work material properties which are found to have significant effects on triangulation.