• Computational Structural Engineering
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• v.9 no.4
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• pp.199-207
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• 1996

In the past decade soft clay shield tunneling technology have been improved to permit continuous support to the face of a tunnel. These advanced shield can be operated such that an initial heaving is created, this helps to decrease the inward soil movement into the tail void. In this paper, the measurement of slurry shield and EPB shield were used and two dimensional elasto-plastic programs EPSHILD developed for shield tunnel analysis were approved. The excavation steps corresponding with construction stages were settled and heaving load, load factors were considered. This study is based on the instantaneous settlement which is occured in the process of shield construction but not the secondary settlement by consolidation.

• The Journal of Engineering Geology
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• v.23 no.3
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• pp.247-256
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• 2013

The carbonate sands of the Sabkha layer in the Middle East have very low shear strength. Therefore, instant settlement and time-dependent secondary settlement occur when inner voids are exposed, as in the case of particle crushing. We analyzed settlement of the Sabkha layer under a large-scale foundation by hydrotesting, and compared the field test results with the results of laboratory tests. With ongoing particle crushing, we observed the following stress-strain behaviors: strain-hardening (Sabkha GL-1.5 m), strain-perfect (Sabkha GL-7.0 m), and strain-softening (Sabkha GL-7.5 m). General shear failure occurred most frequently in dense sand and firm ground. Although the stress-strain behavior of Sabkha layer carbonate sand that of strain-softening, the particle crushing strength was low compared with the strain-hardening and strain-perfect behaviors. The stress-strain behaviors differ between carbonate sand and quartz sand. If the relative density of quartz sand is increased, the shear strength is also increased. Continuous secondary compression settlement occurred during the hydrotests, after the dissipation of porewater pressure. Particle crushing strength is relatively low in the Sabkha layer and its stress-strain behavior is strain-softening or strain-perfect. The particle crushing effect is dominant factor affecting foundation settlement in the Sabkha layer.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.10a
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• pp.81-88
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• 1997

현재 국내외에서 해안가에 수심이 낮은 지역을 중심으로 대규모 매립공사를 수행하여 주택단지, 항만시설, 공업단지 및 공항부지 등으로 사용하고 있다. 매립재를 양질의 모래로 사용하는 경우 매립방법에 따라 매립토의 조밀정도는 다르나 어떠한 경우든 상당히 느슨하거나 중간정도 느슨한 상태로 존재한다. 이런한 느슨한 사질토는 지진 시 액상화 현상에 민감하고, 낮은 지지력 및 큰 즉시침하를 야기시킨다. 따라서 매립된 느슨한 사질토는 향후 시설될 구조물의 중요도에 따라 개량할 필요가 있다. 본 현장의 준설 매립된 사질토의 지반 개량에 적용된 동다짐의 시험시공중 pounder에 accelerometer를 설치하고 적외선 beam을 이용, 충격시의 pounder의 deccleration과 impact velocity를 측정하였다. 여기에서는 이들 실측치를 근거로 중량물체(pounder)의 동적 거동 및 충격시 과잉간극수압 변화를 살펴보았다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1243-1251
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• 1994

The implicit finite difference program was developed to evaluate the relationship between time and consolidation ratio within the zone of vertical drain effective radius. In the evaluation, the excess pore water pressure was considered to dissipate in two directions, namely, vertical and radial flow direction. To calculate subsoil stress increments in the soil due to multi-step embanking, the foundation soil was assumed to be an isotropic and homogeneous elastic medium and the initial excess pore water pressure was estimated by using Skempton's parameters whose condition is plane strain and elastic phase of pore pressure response within the soft ground. Regarding to the settlement estimation, immediate and primary consolidation settlements were calculated. The secondary or delayed consolidation settlement was not considered. Numerically calculated excess pore water pressure and settlements were similar to the measured data in situ. Thus, this method can be used to predict the time-consolidation ratio of each layer treated by vertical drain method.

• Journal of the Korean Geotechnical Society
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• v.24 no.10
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• pp.83-91
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• 2008

Previous settlement prediction methods based on settlement monitoring were developed under instantaneous loading condition and have restriction to be applied to soft ground under ramp loading condition. In this study, settlement prediction method under ramp loading was developed. New settlement prediction method under ramp loading considered influence factors of consolidation settlement such as thickness of clayed layer, quantity of surcharge load and preconsolidation pressure, etc. Geometrical correction method based on hyperbolic method (1991) and correction method based on probability theory were applied to increase accuracy of settlement prediction using field monitoring data after ramp loading. Large consolidation tests for ideally controlled one dimensional consolidation under ramp loading condition were performed and the settlement behavior was predicted based on the monitoring data. New prediction method yielded good result of entire settlement behavior by using data during an early stage of ramp load. Additionally, new prediction method offered better settlement prediction which had final settlement prediction in close proximity and low RMSE(Root Mean Square Error) than previous method such as hyperbolic method did.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.02a
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• pp.78-83
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• 1999

The ultimate settlement of soft clay consists of three parts: $\circled1$ immediate settlement, S$\sub$d/; $\circled2$ Primary consolidation settlement, S$\sub$c/; $\circled3$ Secondary consolidation settlement, S$\sub$s/. In general, S$\sub$c/ can be accurately calculated by one-dimensional consolidation and S$\sub$s/ or S$\sub$d/ may be ignored. This paper focuses on a calculation method to estimate the immediate settlement induced by lateral deformation of subgrade, to which shear stress is applied by embankment on soft ground. Immediate settlement and consolidation settlement are discussed by comparing the field measurement of the Yangsan test embankment on treated soft foundation by vertical paper drains.