• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.484-491
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• 2008

The purpose of this study is to compare the cementation effect on cone resistance and DMT indices and to evaluate the deformation characteristic of cemented sand using cone resistance and dilatometer modulus. Specimens of various relative densities with three different cementation levels are prepared in a large calibration chamber under different vertical stress levels. Test result shows that the cone resistance and dilatometer modulus underestimate the deformation modulus of cemented sand, since in situ penetration tests such as CPT and DMT damage the cementation bonds during penetration. By regression analysis, the constrained modulus of cemented sand is related with the cone resistance and the dilatometer modulus.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.740-746
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• 2010

Most important characteristics of calcareous sand are the particle angularity and hollow structure. These characteristics lead to the different behavior of calcareous sand compared to siliceous sand. This study performs a series of dilatometer test using calibration chamber, in order to analyze the effect of particle characteristic of calcareous sand on DMT indices. From experimental test, it is observed that the horizontal stress index($K_D$) and dilatometer modulus($E_D$) of calcareous Jeju sand is underestimated compared to siliceous sand. This is because the particle crushing during penetration induces the less contraction of the dilatometer membrane. A slightly smaller influence of particle crushing is reflected in $E_D$ rather than $K_D$, because $P_1$ pressure reflects the deformation characteristics of un-crushed particle relatively well. It is also observed that $K_D$ of Jeju sand is differently influenced by the vertical effective stress compared with that of siliceous sand.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1996년도 가을 학술발표회 논문집
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• pp.61-70
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• 1996

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.730-739
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• 2010

Stress history increases in penetration resistance due to the increase in residual horizontal stress of granular soil. This study analyzes the effect of stress history on the results of CPT and DMT from calibration chamber specimen in OC as well as NC state. Test results show that the normalized cone resistance by mean effective stress correlates well with the relative density and the state parameter, whereas the normalized cone resistance with regard to vertical effective stress is a little affected by stress history. The horizontal stress index($K_D$) in DMT more reflects the influence of stress history on granular soil than the dilatometer modulus($E_D$) and cone resistance($q_c$). The $K_D/K_0$, in which the effect of stress history on $K_D$ is compensated by the at-rest coefficient of earth pressure, $K_0$, is related to relative density, state parameter and the normalized cone resistance by mean effective stress. It is also observed that the normalized dilatometer modulus by mean effective stress($E_D/{\sigma_m}'$) is unique correlated with the state parameter, regardless of stress history.

• 한국지반공학회논문집
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• 제20권5호
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• pp.17-25
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• 2004

DMT 시험은 연약지반의 공학적 특성을 파악하기 위한 현장 시험방법으로, 이 방법으로부터 구한 비배수 전단강도는 가장 신뢰성 있고 유용한 매개변수로 알려져 있다. 그러나 국외 다른 지역의 자료를 토대로 기존에 제안된 상관관계식들은 지역적인 특성에 의존한다. DMT 시험 결과는 3가지 중간 지수 - 재료지수, 수평응력지수, dilatometer modulus를 사용하여 해석이 이루어지며 특히 비배수 전단강도는 수평응력지수만을 이용하여 예측하고 있다. 본 논문에서는 먼저 DMT 시험의 국내 연약지반에서의 적용성을 살펴보았으며 DMT로부터 비배수 전단강도를 추정하기 위하여 $p_0, p_1, p_2, {\sigma '}_v$ 그리고 초기 간극수압을 바탕으로 인공신경망 모델을 개발하였다. 인공신경망 모델은 오차 역전파 알고리즘을 적용하였으며 국내 연약지반에서 수행된 DMT 시험 자료를 이용하여 훈련하였다. 인공신경망 모델의 적용성을 판단하기 위하여 훈련에 이용되지 않은 자료로부터 예측된 결과와 기존에 제안된 상관관계식으로부터 얻은 결과를 서로 비교하였다.

• 한국지반공학회논문집
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• 제26권4호
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• pp.27-36
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• 2010

사질토의 상태정수를 현장시험으로부터 추정하기 위해 실내 챔버에 조성된 부산사에 대해 딜라토미터 시험을 수행하였다. 시험결과, 수평증폭계수($K_D/K_0$)와 상태정수($\Psi$)의 관계는 반대수축상에서 선형관계를 보였으나, 응력이력에 의한 잔류수평응력의 영향으로 과압밀 시료가 정규압밀 시료에 비하여 동일한 상태정수에서 수평증폭계수의 값이 작게 평가되었다. 유효응력으로 정규화된 딜라토미터 계수($E_D/\sigma_m'$)와 상태정수의 관계는 반대수축상에서 선형관계를 만족하였으며, 다소의 분산은 있으나 응력이력에 관계없이 하나의 관계식으로 표현 기능하였다. 다만 응력수준의 영향으로 과압밀 상태보다 정규압밀 상태의 분산이 약간 크게 발생되었으며 구속압이 증가할수록 관계곡선이 하향 이동하는 경향이 나타났다. 기존에 연구된 Ticino sand 및 Toyoura sand와 비교한 결과, $K_D/K_0-\Psi$ 관계는 혼재되어 분포하였으나, $E_D/\sigma_m'-\Psi$ 관계는 시료 압축성의 영향으로 Toyoura sand가 Ticino snad 및 부산사의 상부에 위치하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.613-618
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• 2008

Because the flat dilatometer (DMT) is operated in appropriate strain level, it has been known as an adoptable in-situ tool to evaluate the compressibility of soils compare with other in-situ test tools, such as SPT and CPT. This study is concerned about prediction method of constrained modulus by DMT, and a series of DMT and consolidation tests are performed at Busan new-port, Yangsan and Noksan test sites. By comparing DMT results with lab tests, the suitability of constrained modulus correlation, which is suggested by Marchetti, is investigated in Busan clay and new correlation is suggested. In lab test result, the compression indices ($C_c$) of Busan clay are turned out to be 0.4~0.12, and the constrained moduli are found out 0.5MPa~3MPa and these are increase with depth. The predicted constrained moduli using Marchetti's correlation are turned out 0.5MPa~4MPa, and these are bigger than measured constrained moduli by lab tests. By analyzing lab test and DMT results, it is shown that the correlation coefficient ($R_M=M/E_D$) has a linear relationship with (1/$I_D$) in Busan.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.154-161
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• 2004

The flat dilatometer test(DMT) is a geotechnical tool to estimate in-situ properties of various types of ground materials. The undrained shear strength is known to be the most reliable and useful parameter obtained by DMT. However, the existing relationships which were established for other local deposits depend on the regional geotechnical characteristics. In addition, the flat dilatometer test results have been interpreted using three intermediate indicesmaterial index($I_p$), horizontal stres index($K_p$), and dilatometer modulus($E_p$) and the undrained shear strength is estimated only by using the horizontal stress index($K_D$). In this paper, an artificial neural network was developed to evaluate the undrained shear strength by DMT and the ANN, based on the $p_0,\;p_1,\;p_2,\;{\sigma}'_v_0$, and porewater pressure. The ANN which adopts the back-propagation algorithm was trained based on the DMT data obtained from Korean soft clay. To investigate the feasibility of ANN model, the prediction results obtained from data which were not used to train the ANN and those obtained from existing relationships were compared.

• 한국지반공학회논문집
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• 제26권7호
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• pp.7-16
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• 2010

응력이력은 사질토 지반의 잔류 수평응력을 증가시켜 현장시험의 관입저항을 증가시킨다. 본 연구에서는 챔버에 조성된 정규 및 과압밀 시료에 대한 콘관입시험과 딜라토미터 시험을 수행하고 응력이력이 시험결과와 측정값의 상관관계에 미치는 영향을 분석하였다. 시험결과, 평균 유효응력으로 정규화된 콘선단저항은 상대밀도 및 상태정수와 높은 상관성을 보였다. 딜라토미터의 수평응력지수($K_D$)는 콘선단저항($q_c$) 뿐만 아니라, 딜라토미터 계수($E_D$) 보다도 응력이력 영향을 효과적으로 반영하였다. 수평응력지수에 반영된 응력이력의 영향을 정지토압계수인 $K_0$로 보정한 $K_D/K_0$는 상대밀도 뿐만 아니라, 상태정수, 평균 유효응력으로 정규화된 콘선단저항과 응력이력에 관계없는 높은 상관성을 보였다. 또한 평균 유효응력으로 정규화된 딜라토미터 계수($E_D/{\sigma}_m'$)와 상태정수의 관계도 응력이력에 관계없이 유일한 식으로 표현되었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 봄 학술발표회 논문집
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• pp.639-646
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• 2000

It is important to estimate the mechanical properties of clay since it is directly related to the design and the construction of geotechnical structures. Site exploration, which is composed of boring, sampling, in-situ, or laboratory tests, is preformed to estimate the mechanical properties. However, mechanical properties of clay measured from laboratory test may be different from in-situ properties due to disturbances occurred during sampling, transportation, storage, and trimming. In this study, the degree of disturbance according to sampling method was estimated with the test results of CK/sub o/U triaxial compression test on Yangsan clay. The soil samples were obtained by three types of sampling method, j.e., 76mm-tube sampler, 76mm-piston sampler, and block sampler. In order to evaluate the quality of samples, volumetric strain, undrained shear strength, secant Young's modulus, and pore pressure coefficient at peak measured from each sample were compared with one another. From the test results, it was observed that mechanical properties of the block and piston samples were more reliable than those of tube samples. But it was observed that the water content of piston was similar to that of tube samples at given depths while the water content of block samples was 14.3∼15.8% smaller than that of piston and tube samples. In addition to the evaluation of the quality of samples, relationship between c/sub u// σ/sub vc/'and OCR was established from the results of the CK/sub o/U triaxial compression tests, which were carried out using SHANSEP method. And also undrained shear strength was analyzed using the in-situ test data such as Cone Penetration Test(CPT), Dilatometer Test(DMT), and Field Vane Test(FVT) and was compared with that evaluated from CK/sub o/U triaxial compression test.