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여인석,임경희 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.5
A method to extend the region of validity of the critical-scaling equations is presented and is tested by fits to the vapor/liquid equilibria (VLE) of ethane, propane, and n-butane. In this method there are two elements. One of them is to find an appropriate order parameter (OP) and the other one is how to fit the equations to equilibrium data. As for the OP, the nonlinear OP Smith and Ferer proposed [7] has been used. For the critical scaling equations, terms different from those they used have been employed. This leads to better results and physically sounder value of exclusion-volume-like fitting parameter b. As for the fitting method, first the critical parameters, Tc and Vc are determined and then linear regressions for the fits to VLE data have been adopted. Otherwise, nonlinear regressions have to be essentially employed. Pre-determination of Tc and Vc and the different terms for critical scaling equations provide relatively significant advantages; (i) it makes fits to VLE binodals linear, (ii) the exclusion-volume-like fitting parameter b is approximately equal to the van der Waals parameter bvdW, and (iii) the fits are in excellent agreement with the VLE data. In fact, the calculated values trace the VLE data almost exactly.
이문주(Lee Moon Joo),배경두(Bae Kyung Doo),안성모(An Sung Mo),이우진(Lee Woo Jin) 대한토목학회 2010 대한토목학회논문집 C Vol.30 No.2
본 연구에서는 제주해사에 대한 일련의 삼축압축시험을 수행하여 파쇄성이 큰 제주 탄산염 모래의 한계상태정수를 결정하였다. 제주해사는 입자의 모난 정도가 크고 입자표면과 내부에 다수의 공극이 발달되어 전형적인 탄산염 모래의 특성을 보인다. 제주해사는 큰 최대 최소 간극비와 큰 압축성 때문에 전단 시 압축거동이 지배적이었다. 구속압이 증가할수록 입자가 파쇄되어 제주해사의 첨두마찰각이 다소 감소하였으나, 일반적인 규산염 모래의 마찰각보다는 다소 큰 것이 관찰되었다. 제주해사의 한계상태 마찰각은 평균유효응력이 증가할수록 점차 감소하였으나, 시료의 간극비가 제주해사의 한계상태에 미치는 영향은 미미하였다. 제주해사의 한계상태 정수는 여타의 탄산염 모래와 유사하였으나, 일반적인 규산염 모래보다는 매우 크게 결정되었다. A series of triaxial test was performed in order to determine critical state parameters of calcareous Jeju sand, which comprises angular shape particles with many pores in the surface. It is observed that Jeju sand mainly shows the contractive behavior during triaxial shear due to high extreme void ratios and large compressibility. The peak friction angle of Jeju sand decreases slightly with increasing mean effective stress due to the particle crushing of carbonate materials. However, the peak friction angle of Jeju sand is higher than that of other silica sands because of the more angular particle shape. The critical state friction angle of Jeju sand gradually decreases when the mean effective stress at a critical state increases. Whereas, there is not a clear influence of void ratio on the critical state friction angle. Critical state parameters of Jeju sand are similar to those of calcareous sands, but significantly larger than those of common sands.
Relationship between the State Parameter and Cone Resistance of Busan Sand
김승한,이문주,최성근,홍성진,이우진 한국지반공학회 2007 한국지반공학회논문집 Vol.23 No.3
A series of CIDC triaxial tests and cone penetration tests in calibration chamber were performed to investigate the relationship between state parameter and normalized cone resistance for dredged Busan sand. From the results of the triaxial tests, the critical state line of Busan sand was established, and the critical state parameters found to be M=1.39 (cs=34°), Γ=1.07 and λ=0.068. By analyzing the state parameters and corresponding cone resistances for calibration chamber specimens, the relationship between normalized cone resistance and state parameter for Busan sand was defined as (qc-p)/p′=27.6exp(-10.9). This relationship was also shown to be independent of the stress history. From the comparison of the slope of the normalized cone resistance, m, and the normalized cone resistance at =0, κ, with those of various sandy soils from over the world, the relationship of m and κ with λss of Busan sand was concluded to show a good agreement with the result published previously, while Busan sand had the largest κ among the soils with similar λss values.
Back Analysis Method of Homogeneous Slope at Critical State
Hang Lin,Jingyu Chen 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.3
The angles of homogeneous slopes θ are divided into three partitions (θ ≤ 40°, 40° < θ < 50°, and 50° ≤ θ) to deduce the calculation formula for the maximum depth D of critical slip surface below the slope surface. The formula proves that the slip surface location in soil homogeneous slopes is related only to the ratio of c (cohesion) and tanϕ (angle of shearing resistance) for the known slope geometry and unit weight. In this paper, extensive calculations are carried out to draw relation charts between dimensionless shear strength parameters λcϕ = c/(γH0tanϕ) and the ratio D/H0 (where D is the maximum depth of the critical slip surface, H0 is the slope heights), as well as the relation between λcϕ and angle of shearing resistance ϕ. Results show that D/H0 and ϕ are only determined by λcϕ, and do not change with different slope heights. Through the measurement of the maximum depth of the slope slip surface, the shear strength parameters of homogeneous slopes at the critical state can be obtained based on back analysis relation charts. The correctness of this method is verified by comparing the numerical calculation results
Effects of silt contents on the static and dynamic properties of sand-silt mixtures
Hsiao, Darn H.,Phan, Vu T.A. Techno-Press 2014 Geomechanics & engineering Vol.7 No.3
This paper presents a detailed study focused on investigating the effects of silt content on the static and dynamic properties of sand-silt mixtures. Specimens with a low-plastic silt content of 0, 15, 30 and 50% by weight were tested in static triaxial, cyclic triaxial, and resonant columns in addition to consolidation tests to determine such parameters as compression index, internal friction angle, cohesion, cyclic stress ratio, maximum shear modulus, normalized shear modulus and damping ratio. The test procedures were performed on specimens of three cases: constant void ratio index, e = 0.582; same peak deviator stress of 290 kPa; and constant relative density, $D_r$ = 30%. The test results obtained for both the constant-void-ratio-index and constant-relative-density specimens showed that as silt content increased, the internal friction angle, cyclic stress ratio and maximum shear modulus decreased, but cohesion increased. In testing of the same deviator stress specimens, both cohesion and internal friction angle were insignificantly altered with the increase in silt content. In addition, as silt content increased, the maximum shear modulus increased. The cyclic stress ratio first decreased as silt content increased to reach the threshold silt content and increased thereafter with further increases in silt content. Furthermore, the damping ratio was investigated based on different silt contents in three types of specimens.