• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.5
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• pp.355-374
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• 2022

Soil conditioning improves the performance of EPB (earth pressure balance) shield TBMs (tunnel boring machines) by reducing shear strength, enhancing workability of the excavated soil, and supporting the tunnel face during EPB tunnelling. The mechanical and rheological behavior of the excavated muck mixed with additives should be properly evaluated to determine the optimal additive injection condition corresponding to each ground type. In this study, the laboratory pressurized vane test apparatus equipped with a vane-shaped rheometer was developed to reproduce the pressurized condition in the TBM chamber and quantitively evaluate rheological properties of the soil specimens. A series of the pressurized vane tests were performed for an artificial sand soil by changing foam injection ratio (FIR) and polymer injection ratio (PIR), which are the injection parameters of the foam and the polymer, respectively. In addition, the workability of the conditioned soil was evaluated through the slump test. The peak and yield stresses of the conditioned soil with respect to the injection parameters were evaluated through the rheogram, which was derived from the measured torque data in the pressurized vane test. As FIR increased or PIR decreased, the workability of the conditioned soil increased, and the maximum torque, peak stress, and yield stress decreased. The peak stress and yield stress of the specimen from the laboratory pressurized vane test correspond to the workability evaluated by the slump tests, which implies the applicability of the proposed test for evaluating the rheological properties of excavated soil.

• Journal of the Korean GEO-environmental Society
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• v.20 no.2
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• pp.59-67
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• 2019

Using the results from laboratory soil test, field vane test and piezocone penetration test, the engineering characteristics of the soft ground at east side of Gwangyang Port, which is located at south coast of Jeollanam-do, were investigated and optimal piezocone penetration test depth was derived to calculate piezocone factor. In this paper, the results of 61 laboratory soil tests, 226 times of field vane tests and 26 piezocone penetration tests were used. The result of laboratory soil test suggested that some physical properties such as specific gravity, moisture content, liquid limit and plastic index and others are higher than other south coast regions, meanwhile uniaxial compression strength, undrained shear strength, defined as mechanical property, appeared to be relatively small, distributed widely. According to the plastic chart, the ground was classified as high compressibility clay and low compressibility clay, mostly represent to Type 3 clay by Robertson (1990)'s classification chart. Piezocone factor was calculated by empirical method, based on the undrained shear strength which was obtained by the field vane test. According to the analysis with 3 different depth range, to set the appropriate measured depth range of piezocone penetration for comparation, using average value of the range of 5 times the vane length showed the highest correlation.

• Journal of the Korean Geosynthetics Society
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• v.19 no.4
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• pp.65-74
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• 2020

In earth pressure balance (EPB) shield TBM tunnelling, the application of soil conditioning which improves properties of the excavated muck by additives injection, is generally used for enhancing the performance of TBM. Therefore it is important to apply the soil conditioning in the numerical model which simulates excavation performance of TBM equipment, but related studies on a method that simulates soil conditioning are insufficient to date. Accordingly, in this study, an laboratory pressurized vane test apparatus was devised to evaluate the characteristics of conditioned soil. Using the apparatus, the vane shear tests were performed on foam-conditioned soil with different shear rates, and the test was numerically simulated with discrete element method (DEM). Finally, the contact properties of particles in DEM were determined by comparing the results of test and analysis, and it indicates that the applicability of pressurized vane test and DEM model for reproducing soil conditioning in TBM excavation model with DEM.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5572-5577
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• 2012

Results of in-situ test, laboratory test and strength prediction method for the soft soil underlain by failed road embankment were compared each other. Comparing cone penetration test results with the field vane test results it can be seen that cone factor is 12. Undrained shear strengths determined from the cone factor which was predicted by prediction equation were smaller than those obtained from field vane tests. Among the prediction methods Jamiolkowsky's method gave close strengths to the measured undrained shear strengths by field vane tests and strength ratio were 0.88~1.23.

• Journal of the Korean GEO-environmental Society
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• v.13 no.5
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• pp.41-49
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• 2012

In this study, laboratory test, in-situ vane shear test and piezocone penetration test in the study area were conducted to investigate the engineering characteristics of soft soils at Cheongra District, Songdo District in Incheon City, the west coast of Gyeonggi province, and Sihwa District in Ansan city. The correlations among compression index, and in-situ vane shear test, and cone resistance were obtained. The variations of liquid limit, plasticity index, water content and compression index with respect to depth exhibit strong similarity. This means that they have strong correlations, which can be used to evaluate the local characteristics of the study area. Thus, the correlations between compression index and physical properties were analysed to investigate the engineering characteristics of soft soil in the study area. The relationships between the measured piezocone factor by empirical methods, and undrained shear strength obtained by triaxial compression test or in-situ vane shear test were compared. It shows the significant correlation and piezocone factors, $N_{kT}$are suggested for the study area.

• Journal of the Korean Geotechnical Society
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• v.25 no.1
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• pp.77-88
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• 2009

Cone factors, $N_{kt}$, $N_{ke}$ and $N_{{\Delta}u}$, for estimating undrained shear strength of Busan clay are evaluated in this study. For this, CPTu and field vane tests are performed for clay layers at two sites, Busan new-port and Noksan, and also $CK_0U$ triaxial tests with undisturbed samples taken from the same site are carried out. From experimental results, it is observed that the undrained shear strengths of clay increases with depth, and the undrained shear strength obtained from triaxial tests is 1.5 times higher than one obtained from vane tests. The normalized undrained shear strengths of Busan clay from triaxial and vane shear tests are $0.26{\sim}0.44$ and $0.20{\sim}0.23$, respectively. In CPTu results, cone tip resistance ($q_c$) and pore pressure ($u_2$) linearly increase with depth, and the pore pressure ratio ($B_q$) of Busan clay is within the range of $0.3{\sim}1.0$. The cone factors, which are determined by comparing the CPTu results with $CK_0U$ triaxial and vane shear test results, are found to be $5{\sim}20$ and $10{\sim}35$, respectively. It is also observed that the cone factors are inversely proportional to the pore pressure ratio. From this, the prediction methods for evaluating the cone factors of Busan clay are developed.

• Journal of Industrial Technology
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• v.29 no.B
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• pp.81-88
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• 2009

The main purpose of this work is to determine characteristics of undrained shear strength of remolded marine clay at Incheon. Laboratory vane tests with remolded marine clay sampled from west coast at Incheon were performed to investigate the undrained shear strength of them being dumped for reclamation after dredging from the sea bottom. Test results were compared with the predicted values of undrained shear strength proposed by many researchers. It was found that measured results about undrained shear strength with water content was in good agreements with values proposed by Mikasa and Modified Mikasa's empirical formula.

• Journal of Industrial Technology
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• v.30 no.A
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• pp.103-109
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• 2010

This research is to determine characteristics of undrained shear strength of remolded marine clay at Incheon and Busan, representing typical marine clays in Korea. Laboratory vane tests with remolded marine clays sampled from coasts at Incheon and Busan were performed to investigate the undrained shear strength of them. Test results were compared with the predicted values of undrained shear strength proposed by many researchers. It was found that measured results about undrained shear strength with water content was in good agreements with values proposed by Terzaghi empirical formula.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.259-267
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• 2001

실내시험으로 구한 점토의 공학적 성질은 샘플링, 운반, 저장, 그리고 성형과정 동안에 발생하는 시료의 교란으로 인해 원지반의 성질과 다르게 측정된다. 본 연구에서는 양산점토에 대한 삼축압축시험($CK_{o}$ UC) 결과를 이용하여 샘플링 방법에 따른 교란의 정도를 평가하였다. 실험에 사용된 시료는 76mm 튜브샘플러, 76mm 피스톤샘플러, 블록샘플러로 채취되었으며, 시료의 교란정도를 평가하기 위해 각 시료에서 측정된 체적변형률, 비배수 전단강도, Secant Youngs modulus, 그리고 파괴시 간극수압계수를 비교하였다. 시료의 교란정도를 평가하는 것 이외에도 SHANSEP 방법을 이용하여 수행한 $CK_{o}$ U 삼축압축시험 결과를 이용하여 양산점토에 대한 정규화 전단강도($C_{u}$ /$\sigma$$_{vc}$ )와 OCR 관계를 규명하였다. 또, 피에조콘 관입시험, 딜라토메타 시험, 그리고 현장 베인시험결과를 이용하여 구한 양산점토의 비배수 전단강도를 삼축압축시험 결과와 비교하였다.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.3 s.14
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• pp.25-31
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• 2004

Rail road slope can be fatted because of existence of unexpected soft subsoil. Purpose of this study is verifying the cause of rail road slope failure and determination of soil strength for remedy. Drilling some boreholes, cone penetration test and field vane test were executed in order to find out the cause of slope failure. In addition, laboratory test was conducted in order to determine soil strength of soft soil sampled as undisturbed state. As a result of both the in-situ and the laboratory tests, the cause of slope failure is thought to be propagation of failure zone by progressive rupture of overconsolidated clay Soft soil strength was determined through back analysis of the failed slope.