• 한국지반공학회논문집
• /
• 제16권4호
• /
• pp.83-94
• /
• 2000

본 연구에서는 국내에서 PMT의 적용성, 시험절차, 그리고 시험결과로부터 지반의 전단강도정수 $(cu,\phi)$와 변형특성치 (E)를 결정하는 절차등을 고려하였으며, Elastometer-200을 사용하여 부산지역의 해저지반 3개지역, 6개 시추공에서 PMT를 수행하였다. 시험과정에서 발생되었던 문제점들을 분석하였으며 시험결과를 분석하였다. PMT 시험공의 정지압력은 프레셔미트곡선에서 직접 판독할 수 있었으며, 한계압력 ｐ 은 외삽적인 방법인 $ｐ-log(\Deltav/v)$방법에 의하여 결정할 수 있었다. 또한 지반의 강도정수$(cu,\phi)$와 변형계수(E)도 구할수 있었으며, PMT결과로 구한 지반 특성치는 실내실험에서 구한 특성치보다 크게 평가되었다.PMT결과로 지반의 종류를 개략적으로 평가할 수 있었다. 부산지역 해저지반의 경우, ｐ 의 값은 점성토의 경우 6.4~22.5 $kg/cm^2$, 사질토의 경우 2.2~30.0$kg/cm^2$, 풍화토의 경우 13.0~58.0$kg/cm^2$, , 풍화암의 경우 47.0~190.0 $kg/cm^2$의, 범위에 있었다. 또한, Em/ｐ 은 점성토의 경우 2.4~7.6, 사질토의 경우 2.6~12.1, 풍화토의 경우 6.8~17.1, 풍화암의 경우 7.2~29.6의 범위에 있었다.

• 한국철도학회논문집
• /
• 제8권4호
• /
• pp.367-371
• /
• 2005

Pile foundations are utilized when soil is so weak that shallow foundations are not suitable or point load is concentrated in small area. Such soil can be formed by the land reclamation works which have extensively been executed along the coastal line of southern and western parts of the Korean Peninsula. The working load at pile is sometimes subjected to not only compression load but also lateral load sad uplift forces. But in most of the practice design, uplift capacity of pile foundation is not considered and estimation of uplift capacity is presumed on the compression skin friction. This study was carried out to determine that the effect of embedment ratio and loading rate on uplift adhesion factor of concrete pile driven in clay. Based on the test results, the critical embedment ratio is about 9. Adhesion factor is constant under the critical embedment ratio, and decreasing over the critical embedment ratio. Also, adhesion factor is increased with the loading rate is increased.

• 산업기술연구
• /
• 제28권B호
• /
• pp.81-89
• /
• 2008

This paper is results of investigating the dominant factors influencing to coefficient of consolidation in horizontal direction of Korean marine clays and their correlations through literature review. From the results of analyzing data obtained from field tests such as piezocone penetration and dilatometer tests as well as laboratory tests, coefficient of consolidation in the horizontal direction was found to increase with increase of stiffness index of soil while it decreases with the increase of dissipation time of pore pressure developed during field tests. In general, the coefficient of consolidation in the horizontal direction tends to increase with increase of undrained shear strength and preconsolidation pressure although correlation between them are relatively low. Friction ratio has a high correlation with coefficient of consolidation in the horizontal direction in case of friction ratio being greater than 1.0. For methods of estimating coefficient of consolidation in the horizontal direction with different testing device, values obtained from methods of P2-logt and DMT-A with dilatometer were quite similar to values from piezocone penetration test. Consistency of soil is quite proportional to coefficient of consolidation in the horizontal direction. Clear correlation between coefficients of consolidation in the horizontal and the vertical directions could not be found. coefficient of consolidation in the horizontal direction estimated from the results of field test tends to be 1.13~3.11 times greater than that obtained from laboratory tests.

• 산업기술연구
• /
• 제21권A호
• /
• pp.293-301
• /
• 2001

This paper is experimental results of investigating the efficiency of horizontal vacuum drainage system. Effects of size and shape of drain on horizontal vacuum drainage were studied. Model tests in the laboratory with soft marine clay were carried out with drain pipe of having three different diameters and PBD (Plastic Board Drain) of strip shape so that consolidation settlement of soft clay due to applied vacuum pressure, amount of discharge, ground settlement and distributions of pore pressure and undrained shear strength were measured during testing. From results of model test, amount of discharge due to vacuum pressure was increased with the diameter of pipe drain whereas the drain efficiency of pipe in per unit area of drain surface was decreased with diameter of pipe. The rate of discharge per unit time was reduced very fast with diameter of pipe. Settlement of ground surface with time was increased with diameter of pipe as a result of increase of discharge to drain pipe.

• 대한조선학회논문집
• /
• 제55권2호
• /
• pp.161-168
• /
• 2018

This paper presents the design procedure of the suction bucket used to support a subsea manifold. The soil-suction bucket interaction numerical analysis technique was verified by comparing the present results with a reference data. In order to simulate the soil-bucket interaction analyses of a subsea manifold structure, various material data such as undrained shear strength, elastic modulus, and poisson ratio of soft clay in Gulf of Mexico were collected from reference survey. We proposed vertical and horizontal design loads based on system weights and current-induced drag forces. Under the assumption that diameter of the suction bucket was 3.0 m considering real dimension of the subsea manifold frame structures, aspect ratio was decided to be 3.0 based on reference survey. The ultimate bearing load components were determined using tangent intersection method. It was proved that the two design load components were less than ultimate bearing loads.

• 한국지반공학회논문집
• /
• 제17권4호
• /
• pp.57-70
• /
• 2001

한계상태이론은 정규압밀 및 과압밀시료에 대한 비배수 전단강도와 간극수압계수에 관한 식을 제안하고 있는데, 이 식은 3가지 상수를 포함하고 있다. 한계상태상수(M), 한계상태 간격비(${\gamma}$), 한계상태 간극수압계수(Λ)가 바로 그것이며, 이러한 상수는 각 모델 및 구하는 방법에 따라 그 차이가 발생함으로서, 전단강도 및 간극수압계수의 예측시 적지 않은 영향을 미치게 된다. 본 논문에서는 재 성형된 이암풍화토를 이용하여 등방삼축압축시험을 정규압밀과 과압밀로 나누어 실시하고 그 결과를 분석하였으며 이를 토대로 각 모델 및 방법에 따른 상수를 도출하였다. 그리고 이러한 상수의 차이가 비배수 전단강도 및 간극수압계수의 예측에 미치는 영향을 살펴보았다. 시험결과 정규압밀시료의 경우 각 상수의 변화에 따른 비배수 전단강도 및 간극수압계수는 상당한 차이를 보였으며, 한계상태간격비와 Λ값을 강도비로부터 얻어진 값을 사용한 경우가 결과치에 가장 잘 근접함을 알 수 있었다. 과압밀시료의 경우 역시 이들 상수에 따라 전단강도의 변화폭이 크게 나타났으며 정규압밀과 마찬가지로 강도비에서부터 도출된 상수를 적요한 경우 실측치에 가장 근접하였다. 반면 간극수압계수의 예측시에는 상수에 따른 변화폭이 크지 않았으며, 특히 과압밀비가 증가할수록 각 상수에 대한 영향이 작게 나타났다.

• Geomechanics and Engineering
• /
• 제9권5호
• /
• pp.585-599
• /
• 2015

Laboratory model tests were conducted to investigate the effect of surcharge loading rate on the magnitude of lateral displacement of prefabricated vertical drains (PVDs) improved deposit. The test results indicate that under the condition that the system had sufficient factor of safety (FS) ($FS{\geq}1.2$), for the similar model ground under the same total applied surcharge load, the lateral displacement increases with the increase of loading rate. The test results have been used to check the validity of a previously proposed method for predicting the maximum lateral displacement, and it shows that the data points are around the middle line of the predicted range, which supports the usefulness of the proposed method. The basic idea of the prediction method is an empirical relationship between the normalized lateral displacement (NLD) and a ration of load to the undrained shear strength of the deposit (RLS). The model test results offer some modifications of the NLD-RLS relationship: (1) instead of a bilinear relationship, NLD-RLS relationship may be entirely nonlinear; (2) the upper bound value of RLS for the proposed method can be used may be limited to 2.1 instead of the originally proposed value of 3.0.

• 한국지반신소재학회논문집
• /
• 제5권4호
• /
• pp.1-10
• /
• 2006

본 논문에서는 부산신항 민자부두 북컨테이너 1-1단계 조성부지에 시공된 PBD공법의 지반개량효과를 검증하기 위하여 침하량과 압밀침하에 따른 비배수 전단강도를 비교하였다. 적용된 PBD 설계이론을 제시하였으며 CPT 시험결과와 현장 계측결과를 비교함으로써 PBD공법의 개량효과를 검토하였다. 본 사례를 통하여 향후 수행될 각종 연약지반 개량공사에 PBD 공법이 적용될 때 공법의 효용성 및 설계 해석기법의 적용성 검토에 유용한 자료가 되길 기대한다.

• Geomechanics and Engineering
• /
• 제22권5호
• /
• pp.441-448
• /
• 2020

This paper presents a study on the undrained shear strength (s_u) of various sands treated with a biopolymer by employing an extensive series of laboratory fall-cone penetration values covered a range of about 15 mm to 25 mm. In the tests, two sizes (0.15 mm-0.30 mm, and 1.0 mm-2.0 mm) and shapes (rounded, angular) of sand grains, Xanthan gum (XG), and distilled water were used. The XG biopolymer in 0.0%, 1.0%, 2.0%, and 3.0% by dry weight were mixed separately with four different sands, and water. The tests results obtained at the same water content revealed an increase in the su values at different levels with an increase in the XG content. Treating the sands with the XG biopolymer addition was concluded to have a greater efficacy on finer and more angular grains than coarser and more rounded grains in the samples. Overall, the present study indicates that different amount of the XG biopolymer has an important potential to be utilized for increasing the s_u values of samples with various size/shape of sand grains and water content.

• Geomechanics and Engineering
• /
• 제28권2호
• /
• pp.157-169
• /
• 2022

Preloading of soft clays is a common ground stabilization method for improvement of compressibility and the undrained shear strength. The waiting period under preload is a primary design criterion controlling the degree of improvement obtained. Upon unloading the overconsolidation attained with respect to actual loads defines the long term performance. This paper presents a laboratory study for investigation of creep behavior of Famagusta Bay alluvial soft soil preloaded under various effective stresses for analysis of long term performance based on the degree of overconsolidation. Traditional one-dimensional consolidation tests as well as modified creep tests are performed on reconstituted soft specimens. Compressibility parameters are precisely backcalculated using one dimensional consolidation theory and the coefficient of creep is determined using the traditional Cassagrande method as well as two modified methods based on log cycles of time and the inflection of the creep curve. The test results indicated that the long term creep can be successfully predicted considering the proposed method. The creep coefficients derived as part of this method can also be related to the recompression index (recompression index, swelling index) considering the results of the testing method adopted in this study.