• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2010년도 추계 학술발표회
• /
• pp.539-545
• /
• 2010

The field plate test has a good potential for determining since it measures both plate pressure and settlement. The deformation modulus of rock mass is differently measured for status of structures. The values of deformation modulus are obtained from laboratory test (uniaxial and triaxial test) and field test (pressuremeter test). Plate load test should be conducted by different loading plate sizes for geological structure of rock mass and scale of structures. In this paper, large plate load tests were performed to predict of structure's behavior and evaluate the ultimate bearing capacity of the foundation on soft rock. Simultaneously, deformation modulus of rock mass was estimated by back analysis of stresses measured in field test under rock mass. Finally, we verified the validation of deformation modulus of rock mass through result of large plate load test and numerical simulation.

• 한국지반공학회논문집
• /
• 제21권6호
• /
• pp.67-79
• /
• 2005

현장 평판재하시험은 평판에 작용하는 하중과 변위를 동시에 측정하기 때문에 역학적인 특성치 결정의 가능성이 높은 시험방법이다. 그러나 지금까지 평판재하시험으로부터 추정한 탄성계수는 일정 변위를 유발한 하중강도하에서의 지지력계수로부터 구한 하나의 상수값으로서, 이는 포장구조에서 노상이 경험하는 사용하중 단계에서의 대표적인 변형특성치로 결정하기에는 어려움이 있다. 포장설계시 사용되는 회복탄성계수 개념의 변형계수는 중간변형률$(0.01\%\sim0.1\%)$ 영역에서의 값으로서, 현장 노상토의 경우에도 이와 같은 변형률 범위에서의 변형계수를 평가하는 것이 중요하다. 본 논문에서는 노상 현장에서 반복평판재하시험을 이용하여 중간변형률 영역에서의 변형계수를 산정하는 방법을 제안하였다. 이의 신뢰성을 검토하기 위하여 현장에서 크로스홀 시험과 실내에서 공진주시험을 수행하여 전체변형률 영역에서의 현장의 변형특성을 평가하여 평판재하시험 결과와 비교하였다. 두 시험결과 사이의 응력상태를 고려하면 변형률에 따른 변형계수의 값과 경향이 비교적 일치하였고, 제안된 반복식 평판재하시험을통해 현장변형계수의 평가가 가능함을 알 수 있었다.

• 한국정밀공학회지
• /
• 제6권3호
• /
• pp.78-89
• /
• 1989

Applicability of tearing modulus based on J-integral proposed by Paris et al is investigated using compact tension specimens of strutural alloy steel (SCM4). Both general fracture test and instability fracture test are performed. The applied tearing modulus, ( $T_{j}$)app estimated from the real load vs. crack growth curve measured from experiments are compared with that estimated from the limit load vs. crack growth curve. The results are : (1) the $T_{j}$parameter could be applied to predict crack growth instability : (2) The use of ( $T_{j}$)app estimated from the load vs. crack growth curve, proposed in this study could be well predicted crack growth instability instead of that estimated form the limit load vs. crack growth curve.e.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
• /
• pp.1115-1122
• /
• 2011

Reinforced-Roadbed materials are usually composed of crushed stones. Repeated load application can induce deformation in the reinforced-roadbed layer so that it causes irregularity of track. Thus it is important to develop a prediction model of elastic modulus based on stress-strain relation under repeatitive load in order to investigate behavior of reinforced roadbed. The prediction model of elastic modulus of the material can be obtained from repeated triaxial test. However, a proper size of the sample for the test must be used. In this study, a large repeatitive triaxial test apparatus with the sample size of diameter of 30 cm and height of 60cm was adapted for performing test of the crushed stone reinforced-roadbed considering large particle size to get resilient modulus Mr. The obtained resilient modulus was compared to shear modulus obtained from mid size resonant column test. The sample size effect is somewhat large enough so that it is required to design a scale factor based on similarity law in order to use smaller samples for getting elastic modulus of the crushed stone reinforced-roadbed material. A scale factor could be obtained from this study.

• 한국지반공학회논문집
• /
• 제19권5호
• /
• pp.35-47
• /
• 2003

내부를 콘크리트로 속채움한 강관합성말뚝에 대한 기존의 하중전이 측정에서는 강관의 변형률만 측정하고 콘크리트의 변형률은 강관과 동일하다고 가정하였으며, 시방서에 규정한 방법으로 구한 강관과 콘크리트의 탄성계수를 이용하여 말뚝구성부재의 응력 및 축하중을 산정하였다. 그러나 강관의 변형률만 측정하여 강관과 콘크리트가 완전합성 거동하는 것으로 산정한 축하중은 실제 하중값과 상당한 차이를 보이고 있어 강관합성말뚝의 거동을 정확히 분석할 수 없었다. 따라서, 강관합성말뚝의 경우 각 구성부재의 변형률을 측정할 필요성이 제기되었다. 본 연구에서는 강관합성말뚝의 구성부재인 강재와 콘크리트의 변형률을 측정하는데 사용할 수 있도록 개발된 변형봉 센서에 대한 검증실험을 수행하였다 변형봉 센서를 사용하여 말뚝축하중을 산정할 경우 콘크리트의 탄성계수는 현장에서 제작한 콘크리트 공시체의 압축강도 시험에서 구하도록 제안하였다. 즉, (0.2∼0.6)f$_ck$의 응력 범위에 해당하는 평균접선기울기를 탄성계수로 사용하도록 제안하였다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2009년도 춘계 학술발표회
• /
• pp.482-489
• /
• 2009

Various model piles with different sections such as reinforced concrete, steel, steel-concrete composite without rebar and steel-concrete composite with rebar were made, and vertical load test was conducted using a large scaled UTM(Universal Test Machine) to evaluate Young's modulus and ultimate load of the model piles. Based on the tests, ultimate load of steel-concrete composite pile is 31% greater than the sum of it of reinforced concrete pile and it of steel pile. This is caused that ultimate load and Young's modulus of inner concrete increase due to confining effect by outer steel casing. Variation of ultimate load is also insignificant depending on the ratio of length to diameter(L/D), therefore bucking has not an effect on change of ultimate load in case of the L/D below 10.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2005년도 지반공학 공동 학술발표회
• /
• pp.479-488
• /
• 2005

Geopier soil reinforcement system which crushed aggregate is put into a hole and rammed the aggregate with tamper is a viable alternative to deep foundation to over-excavation and replacement. Also, Geopier is intermediate foundation of deep and shallow foundation. In this paper, the value of Geopier element stiffness modulus($K_g$) when designed is compared with the measured value($K_g$) by the in-situ modulus Load test in the field. Also, this paper presents a technology overview of system capabilities and application for foundation reinforcement of structures.

• 한국철도학회논문집
• /
• 제3권2호
• /
• pp.84-91
• /
• 2000

The general concept of reinforced roadbed in the high-speed railway is to cope with the soft ground for the bearing capacity and settlement of foundation soil. The cyclic plate load tests were performed to determine the behavior of reinforced ground with multiple layers of geogrid underlying by soft soil. With the test results, the bearing capacity ratio, elastic rebound ratio, subgrade modulus and the strain of geogrids under loading were investigated. Based on these plate load tests, laboratory model tests under cyclic loading were conducted to estimate the effect of geogrid reinforcement in particular for the high-speed rail roadbed. The permanent settlement and the behavior of earth pressure in reinforced roadbed subjected to a combination of static and dynamic loading are presented.

• 터널과지하공간
• /
• 제27권3호
• /
• pp.172-184
• /
• 2017

동적 초미소 경도법의 압입시험, 하중-비하중 시험, 그리고 반복시험을 이용하여 심도별 대전화강암 내 광물들의 경도와 역학적 특성을 살펴보았다. 시험 결과 세 개 구간(Group-1, -2, -3)으로 광물 집단의 분류가 가능하였다. Martens 경도값은 세 가지 시험법 모두에서 41 m와 223 m 심도에 따른 차이가 크지 않았다. 그럼에도 불구하고, 그 크기는 반복시험<하중-비하중 시험<압입시험 순으로 나타났다. 광물 집단별 평균 Martens 경도, 탄성계수, indentation work 등을 고려해 볼때, 그들의 경계는 비교적 뚜렷하게 나타났다. 결론적으로 동적 초미소 경도법의 세 가지 형태 시험법을 이용함으로써 광물들에 대한 비교적 정확한 경도값을 얻을 수 있었다. 또한 하중-비하중 시험과 반복시험으로부터는 광물들의 탄성계수와 광물들의 탄성적-소성적 성질 특성 파악도 가능하였다.

• International Journal of Railway
• /
• 제6권3호
• /
• pp.112-119
• /
• 2013

A mid-size RC test apparatus (MRCA) equipped with a program is developed that can test samples up to D=10 cm diameter and H=20 cm height which are larger than usual samples used in practice. Using the developed RC test apparatus, two types of crushed trackbed foundation materials were tested in order to get the shear modulus reduction curves of the materials with changing of shear strain levels. For comparison purpose, large repetitive triaxial compression tests (LRT) with samples of height H=60cm and diameter D=30 cm were performed also. Resilient modulus obtained from the LRT was converted to shear modulus by considering elastic theory and strain level conversion and were compared to shear modulus values from the MRCA. It is found from this study that the MRCA can be used to test the trackbed foundation materials properly. It is found also that strain levels of $E_{v2}$ mostly used in the field should be verified considering the shear modulus reduction curves and proper values of $E_{v2}$ of trackbed foundation must be used considering the strain level verified.