• Title/Summary/Keyword: 압밀응력

Search Result 279, Processing Time 0.023 seconds

An Experimental Study on Depositional Environments and Consolidation Properties of Shihwa Deposits (시화지역 퇴적층의 퇴적환경과 압밀특성에 관한 연구)

  • 원정윤;장병욱;김동범;손영환
    • Journal of the Korean Geotechnical Society
    • /
    • v.20 no.5
    • /
    • pp.49-58
    • /
    • 2004
  • Consolidation properties of Shihwa deposits were analysed by means of depositional environments. Depositional environments including particle size distributions, sediment structures, geochemical properties, porewater chemistries and carbon age dating were analysed using undisturbed samples retrieved successively from a boring hole in the study area. Laboratory oedometer tests and anisotropic consolidated triaxial tests (CKoUC) for undisturbed samples were performed to examine the overconsolidation phenomena. Based on the results of analysis of depositional environments, it was found that the upper silt/clay mixed layer was deposited under marine condition while underlying sand and clay layers were deposited under fluvial condition. Planar laminated structures of silts and clays were dominant in marine deposits. Although there was no clear evidences that geological erosion had occurred in marine deposits, overconsolidation ratios of the upper marine samples were greater than unity Stress Paths of the upper marine samples behaved similarly to those of normally consolidated clays. Data plotted in stress state charts showed that the marine deposits were normally consolidated in geological meaning. These apparent overconsolidation of the marine deposits can be explained by the structures i.e. chemical bonding due to the difference of the rate of deposition, not by geological erosions and ground water fluctuations.

Verification of Single Hardening Model (단일 경화 모델의 검증)

  • Kim, Dae-Kyu
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.8 no.4
    • /
    • pp.821-825
    • /
    • 2007
  • In this study, the single hardening model with stress history-dependent plastic potential, which has been most recently proposed based on the critical state soil mechanics and needs few model parameters, was verified for the normally, lightly, and heavily over-consolidated clayey specimens. The triaxial compression tests were strictly conducted. The predictions using the single hardening model generally agree with the measurement. The discrepancy exists on its main focusing on the principal stress rotation; however, the plastic work H and the principal stress rotation angle ${\beta}$ are found to be effective indicators of loading history for the plastic potential function of the stress path dependent materials.

  • PDF

A study on the Consolidation Characteristics of remolding Marine Clay and Weathered Granite Soil by SCT and CRSC (표준.일정변형률속도 압밀시험을 이용한 해성점토.화강암질 풍화토의 압밀특성에 관한 연구)

  • 기완서;주승완;김선학;심태섭
    • The Journal of Engineering Geology
    • /
    • v.12 no.4
    • /
    • pp.459-469
    • /
    • 2002
  • We have remolded marine clay sample collected along the vertical and horizontal directions and investigated the characteristics of the consolidation constants by SCT and CRSC methods. We have studied also on consolidation chracteristics and application for weathered granite soil using SCT and CRSC methods for undisturbed and disturbed samples. As the result, values of pre-consolidation stress, compression index, excessive pore pressure, pore water pressure ratio of the marine-clay were different due to different test methods(SCT and CRSC) and sampling directions(vortical and horizontal directions). Disturbed and undisturbed samples of the weathered granite soil have showed similar change aspect like marine clay during over-consolidatied and normally consolidatied stages.

A Constitutive Model for Lightly Overconsolidated Clays (미약한 과압밀상태의 점토지반에 대한 구성모델)

  • 이승래;오세붕
    • Geotechnical Engineering
    • /
    • v.8 no.4
    • /
    • pp.17-30
    • /
    • 1992
  • Constitutive relations for lightly overconsolidated state of clayey soils. as well as normally consolidated state of those, play an important role in the analyses of geotechnical structures in clay deposits. For the practical point of view, a constitutive model applicable to lightly overconsolidated soils should be developed to easily evaluate the model parameters, and to precisely predict the various behavior of OC soils. For that purpose, a constitutive model for the lightly overconsolidated soil behavior has been proposed to rep- resent the undrained behavior which can be normalized using equivalent pressure, p. , Yielding within the initial yield surface is modeled exclusively using the given normally consolidated model parameters only. Furthermore, the proposed model can be applied to consider the effects of overconsolidation, secondary consolidation, and stress relaxation. The measured behavior in undrained triaxial tests has been Predicted easily and precisely in comparison with other models.

  • PDF

$K_0$ Values and Shear Strengths under $K_0$ Consolidated Triaxial Test According to Matric Suction for an Unsaturated Soil (불포화토의 $K_0$ 압밀 삼축압축실험시 모관흡수력에 따른 정지토압계수 및 전단강도에 관한 연구)

  • Kim, Tae-Kyung;Oh, Se-Boong
    • Journal of the Korean Geotechnical Society
    • /
    • v.24 no.5
    • /
    • pp.89-98
    • /
    • 2008
  • In this study, the behaviour of an unsaturated soil was analyzed by performing $K_0$ consolidated triaxial tests. Unsaturated triaxial tests were performed with matric suctions for weathered soils and stress paths under consolidation and stress-strain relationships under shear were obtained. As a result, the $K_0$ value decreased as the matric suction increased. Besides, both isotropic and $K_0$ conditions had similar shear strength envelopes at the same matric suction. Especially, strength parameters could be obtained by stress variables used in the critical state theory more reasonably than by those of Mohr circles at failure.

Liquefaction Resistance of Gravel-Sand Mixtures (자갈-모래 혼합토의 액상화 거동)

  • Kim, Bang-Sig;Kang, Byung-Hee;Yoon, Yeo-Won
    • Journal of the Korean Geotechnical Society
    • /
    • v.23 no.10
    • /
    • pp.47-56
    • /
    • 2007
  • In this research, the effects of the gravel content on the liquefaction behavior for both of the isotropically and $K_0-anisotropically$ consolidated gravel-sand mixtures are investigated. for this purpose, the cyclic triaxial tests for the specimens with the same relative density (Dr=40%) and variations of gravel content were performed. On the other hand, a series of undrained cyclic triaxial tests were carried out on the isotropically consolidated gravel-sand mixtures with the same void ratio (e=0.7) and from 0% to 30% gravel contents. Void ratios of gravel-sand mixtures with the same relative density (Dr=40%) are found to decrease significantly with the increase of the gravel content from 0% to about 70% and increase thereafter. But the void ratio of the sand matrix among the gravel skeleton increases with the increase of the gravel contents. Test results are as follows : for the isotropically consolidated specimen with 40% of relative density and low gavel contents (GC=0%, 20%, 40%), pore water pressure development and axial strain behavior during undrained cyclic loading show similar behavior to those of the loose sand because of high void ratio, and the specimens with high gravel content (70%) both pore pressure and strata behaviors are similar to those of dense sand. And the isotropically consolidated specimens with the same void ratio (e=0.7) and higher gravel contents show the same behavior of pore water pressure and axial strain as that of the loose sand, but for the lower gravel content this behavior shows similar behavior to that of dense sand. The liquefaction strength of the isotropically consolidated specimens with the same relative density increases with gravel content up to 70%, and the strength decreases with the increase of the gravel content at the same void ratio. Thus, it is confirmed that the liquefaction strength of the gravel-sand mixtures depends both on relative density and void ratio of the whole mixture rather than the relative density of the sand matrix filled among gravels. On the other hand, the behavior of pore water pressure and axial strain for the $K_0-anisotropically$ consolidated gravel-sand mixtures shows almost the same cyclic behavior of the sand with no stress reversal even with some stress reversal of the cyclic loading. Namely, even the stress reversal of about 10% of cyclic stress amplitude, the permanent strain with small cyclic strain increases rapidly with the number of cycles, and the initial liquefaction does not occur always with less than maximum pore water pressure ratio of 1.0. The liquefaction resistance increases with the gravel contents between 0% and 40%, but tends to decrease beyond 40% of gravel content. In conclusion, the cyclic behavior of gravel-sand mixtures depends on factors such as gravel content, void ratio, relative density and consolidation condition.

Shear Strength Estimation of Clean Sands via Shear Wave Velocity (전단파 속도를 통한 모래의 전단강도 예측)

  • Yoo, Jin-Kwon;Park, Duhee
    • Journal of the Korean Geotechnical Society
    • /
    • v.31 no.9
    • /
    • pp.17-27
    • /
    • 2015
  • We perform a series of experimental tests to evaluate whether the shear strength of clean sands can be reliably predicted from shear wave velocity. Isotropic drained triaxial tests on clean sands reconstituted at different relative densities are performed to measure the shear strength and bender elements are used to measure the shear wave velocity. Laboratory tests reveal that a correlation between shear wave velocity, void ratio, and confining pressure can be made. The correlation can be used to determine the void ratio from measured shear wave velocity, from which the shear strength is predicted. We also show that a unique relationship exists between maximum shear modulus and effective axial stress at failure. The accuracy of the equation can be enhanced by including the normalized confining pressure in the equation. Comparisons between measured and predicted effective friction angle demonstrate that the proposed equation can accurately predict the internal friction angle of granular soils, accounting for the effect of the relative density, from shear wave velocity.

Influence of Changing Coefficient of Consolidation and Layered Condition on Consolidation Behavior (압밀계수변화 및 지층조건이 압밀현상에 미치는 영향)

  • Jeon, Je-Sung;Koo, Ja-Kap;Lee, Song
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.9 no.1
    • /
    • pp.147-157
    • /
    • 2005
  • In this study, consolidation analysis methods reflecting various ground condition and changing coefficient of consolidation with consolidation process are presented. Research activities include development of numerical program consists of two parts considering vertical drainage only and both drainage condition with vertical and radial direction. Also, interface equation of adjacent two layers and function for changing coefficient of consolidation are added to developed program. This paper presents the results from a detailed consolidation analyses, which explores consolidation process with time in varying layered system and changing coefficient of consolidation

Pore Pressure Behavior of Normally Consolidated Deep Sea Clay (정규압밀된 심해점토의 간극수압 거동)

  • 박용원
    • Geotechnical Engineering
    • /
    • v.6 no.4
    • /
    • pp.65-74
    • /
    • 1990
  • This paper presents triaxial test (CIVC and CKOUC) results on normally consolidated deep sea clay samples. Based on the test results the pore pressure-strain relations for both isotropicaly and anisotropicaly consgidated samples are expressed with hyperbolic functions of the major princpal strain. The analysis of the difference in pore pressure behavior due to the anisotropy in consolidation stress is carried out with the effective stress pathos of CIVC and CKOUC and finds a factor which correlates the pore pressure of two types of test.

  • PDF

A Study on Reappeared Consolidation Test of In-situ Property and Vertical Deformation of Sample Due to Stress Release (1차원 압밀점토의 응력해방에 의한 수직변형량과 현장재현 압밀시험에 관한 연구)

  • Kim, Jae-Young;Naotoshi, Takada
    • Journal of the Korean Geotechnical Society
    • /
    • v.24 no.7
    • /
    • pp.75-80
    • /
    • 2008
  • When a saturated clay is sampled in an undisturbed manner from a bore hole, the sample extends vertically and shrinks horizontally under undrained conditions due to stress release. The conventional consolidation test specimen is trimmed from the expanded sample so that its diameter is equal to the inner diameter of the consolidation test ring, and this test procedure does not reproduce the actual consolidation behavior. The measurement of sample extension was conducted by means of overcoring method showed that the extension strains were 1 to 2%. To simulate the in-situ consolidation behavior, we proposed the consolidation test method that uses a specimen with a slightly smaller diameter than the inside diameter of consolidometer so that the specimen expands laterally to the inside of the ring.