• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.711-716
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• 2002

When judging the ground by core-logging, depth of coring might be stopped by coming into view of the moderately weathered rock and also considered as bedrock line. However, highly weathered rock may appear again, if coring more, because there are core-stones in the residual soil and highly weathered rock by the effect of hydraulic-thermal differentiation and does the irregular rock weathering or metamorphic rock region. Therefore, there are room for misunderstanding of diagnosing the moderately weathered rock. Even though the irregular ground where the corestones were come out will show clear geotechnical differences between the ground and the gradually weathered bedrock, nowadays, the construction sites do not take into account the characteristic of core-stone region. In conclusion, to study the failure-strength characteristics of soil layers containing core-stones, we made artificial core-stones and varied percentage of corestones, and measured cohesion and friction factors to adjust them to construction sites containing corestones such as slope, tunnel, and underground.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.57-64
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• 2005

Since the allowable bearing capacities of piles in weathered/fractured rock are mainly governed by settlement, the load-displacement behavior of the rock socketed pile should be well known. To predict pile head settlement at the design stage, the exact understanding of the load-transfer mechanisms is essential. Therefore, in this research, the load-transfer mechanisms of drilled shaft socketed into weathered rock was investigated. For that, 5 cast-in-place concrete piles with diameters of 1,000 mm were socketed into weathered gneiss. The static axial load tests and the load-transfer measurements were performed to examine the axial resistant behavior of the piles. A comprehensive field/laboratory testing program on weathered rock at the field test sites was also performed to describe the in situ rock mass conditions quantitatively. And then, the effect of rock mass condition on the load transfer mechanism was investigated. The side shear resistance of the pile in moderately weathered rock reached to yielding point at a few millimeter displacements, and after that, the rate of resistance increment dramatically decreased. However, that in the highly /completely weathered rock did not show the obvious yielding point, and gradually increased showing the hyperbolic pattern until with the relatively high displacement (>10 mm). The end bearing-displacement curves showed linear increase at least until with the base displacement of approximately 10 mm, regardless rock mass conditions.

• 한국지반공학회논문집
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• 제22권3호
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• pp.5-11
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• 2006

광안대교에 설치된 두개의 대구경 말뚝(TS-1과 TS-2)에 대하여 최대 2000톤의 하중을 재하하여 정재하시험을 수행하였다. 시험 말뚝 TS-1의 경우는 연암에 근입되었고 시험 말뚝TS-2의 경우는 풍화암에 근입되었다. 재하시험 결과에 의하면, 지지층과 상관없이 시험말뚝 TS-1과 TS-2 양쪽 경우다 대부분의 하중이 풍화암에 의해 지지되었다. 추가적으로 펜타곤3D와 ROCKET 프로그램으로 수치해석을 수행하였다. 본 연구에 의하면 풍화암이 깊게 발달되어 말뚝 시공상 어려움이 있을 경우, 풍화암도 대안의 지지층으로 고려되어질 수 있다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.603-610
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• 2005

The end bearing behavior of piles socketed in weathered/soft rock is generally dependent upon the mass conditions of rock with fractures rather than the strength of intact rock. However, there are few available data and little guidance in the prediction of the end bearing capacity of drilled shafts socketed in weathered/soft rock, considering rock mass weathering. Therefore, a database of 13 load tests was constructed first, and new empirical relationships between the base reaction modulus of piles in rock and rock mass properties were developed. No correlation was found between the compressive strengths of intact rock and the base reaction modulus of weathered/soft rock. The ground investigation data regarding the rock mass conditions(e.g. Em, Eur, RMR, RQD) was found to be highly correlated with the base reaction modulus, showing the coefficients of correlation greather than 0.7 in most cases. Additionally, the applicability of existing methods for the end bearing capacity of piles in rock was verified by comparison with the field test data.

• 한국지반공학회지:지반
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• 제14권5호
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• pp.53-66
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• 1998

풍화토는 암석이 풍화되어 생성되기 때문에 모암과 풍화과정에 따라 그 특성이 결정된다. 따라서, 풍화토의 특성을 고찰하기 위해서는 먼저 모암에 대한 고찰과 풍화과정을 지배하는 풍화환경에 대한 고찰이 이루어져야 한다. 이번 연구에서는 모암과 풍화정도에 따른 풍화의 특성을 고찰하기 위해 화강암 풍화토와 편마암 풍과토를 불교란 또는 교란상태로 채취한 후. 기본 물성시험, 암석학적 시험 그리고 다양한 전단시험을 실시하였다. 여러 가지 시험의 결과에서 암석의 풍화는 모암의 조암광물 분포 및 생성특성과 밀접한 관계가 있음을 확인하였다. 화강암 풍화토의 경우 모암의 비방향적인 성격 때문에 현장응력 상태화 전단특성이 등방적으로 나타났으며, 편마암 풍과토는 그 내부에 존재하는 불연속면이 역학적 거동을 지배하는 방향적 특성을 갖는 것으로 나타났다. 또한 식영이 장석 또는 운모보다 풍화저항력이 크다는 사실의 확인과 함께 풍화대의 두께가 구성 조암광물에 크게 영향을 받는다는 결론을 얻었다.

• 터널과지하공간
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• 제5권4호
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• pp.336-346
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• 1995

Geotechnical Information System (GTIS) for efficient management of three dimensional borehole data has been developed. Some problems were raised during the input process of borehole data, and alternative solutions were sought. According to the previous geotechnical reports, there is no unified weathering classification scheme. A criterion, 100 times/30cm from SPT, was turned out inappropriate to the discrimination of weathered rock from weathered soil. It has also been suggested that weathered soil, weathered rock, soft rock, and hard rock should be defined as CW, HW, MW, and SW~fresh condition. For better comparison of RQD, the use of NX size coring is recommended for the whole area although BX size coring has been used in excavated area. The limit of drilling depth up to 1 m from the top of surface of hard rock should be extended to avoid possible wrong interpretation of rock head due to the existence of corestone. The input data were analysed by geostatistical methods. It is found that the range in semivariogram is about 300m, and the variance of gneiss is greater than that of granite. It is because the granite data analysed came from almost single uniform rock mass(i.e.Seoul granite), but gneiss data came from the rock mass(i.e. Gyeonggi gneiss complex experienced several metamorphic metamorphic processes.

• 산업기술연구
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• 제21권B호
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• pp.195-203
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• 2001

The purpose of this study is to estimate ultimate uplift capacity of permanent anchor which was cast into weathered rock. The ultimate uplift capacity was estimated from the load-displacement curve of four different anchors which have different bond length. The creep test was performed for 15minutes under the maximum load of each step in order to understand the load-transfer property of permanent anchor and to decide which anchor to choose. The destruction range of soil due to the changes in load was estimated by installing dial gauge on the ground which was cast into the weathered rock. Ultimately, the study on the behavior of the anchor case into the weathered rock was performed by comparing and analyzing the estimated result of the UUC obtained by the full scale pull out test in the field with the exsting theoretical and practical results of soil and rock anchor.

• 한국지반공학회논문집
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• 제21권5호
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• pp.187-196
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• 2005

풍화 및 절리가 발달한 암반에 근입된 말뚝의 허용지지력 결정에는 침하량이 매우 중요한 인자가 되며, 설계단계에서 말뚝두부의 침하량을 예측하기 위해서는 말뚝의 하중전이기구에 대한 이해가 필수적이다. 따라서 본 연구에서는 풍화된 암반에 근입된 현장타설말뚝의 하중전이기구에 대한 연구를 수행하였다. 이를 위해 직경 1m의 총 5본의 현장 타설말뚝을 풍화된 편마암 부지에 시공하구 재하시험 및 하중전이 계측을 수행하여 말뚝의 축방향 지지거동을 분석하였다. 암반상태를 정량적으로 파악하기 위하여 재하시험 부지의 암반에 대한 엄밀한 현장/실내시험을 수행하고, 이를 토대로 암반상태가 말뚝의 하중전이기구에 미치는 영향을 분석하였다. 하중전이 계측을 통해 얻은 주면하중전이 (f-w) 곡선은 풍화상태가 상대적으로 양호한(MW) 연암의 경우, 수 mm의 변위에서 항복에 도달하며, 이후 변위에 따른 지지하중의 증가율이 급격히 둔화되는 경향을 보였다. 반면 풍화암/풍화토에 근입된 말뚝의 f-w 곡선은 뚜렷한 항복점을 보이지 않으며, 상대적으로 큰(>15m) 변위까지 주면하중이 쌍곡선 형태로 증가하였다. 선단하중전이(q-w) 곡선은 암반상태에 관계없이 선단변위 (q-w)까지는 선형적인 거동을 보였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 가을 학술발표회 논문집
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• pp.435-442
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• 2002

Fluid Confirmation Tests(FCT) on 1500 ground Anchors install in weathered rock were carried out to investigate upper and lower limit of elastic elongation, frictional resistant of fixed anchor body, mobilized angle between anchor body and soil. All the measured data were analysed and compared with theoretical equations. The frictional angles of diaphragm wall and anchorage system in weathered rock showed nonlinear curve between upper and lower limit of standard elongation. The FCT results indicated that the frictional resistant angles increased with higher values of surcharge load. The quality assurance on the fixed anchor location was investigated by means of measuring elastic elongation during the FCT, and comparing these with theoretical design length, the quality of anchors in this particular site found to be above average standard. The results of this research works with provide valuable guide line on quality assurance of anchors system as well as resonable prediction of friction resistance between the fixed anchor body and the weathered rock.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.611-618
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• 2005

In this research, the effect of rock mass weathering on the side shear resistance of drilled shaft socketed into weathered rock was investigated. For that, a database of 23 cast-in-place concrete piles with diameters varying from 400mm to 1,500mm were socketed into weathered igneous/meta-igneous rock at four different sites. The static axial load tests were performed to examine the resistant behavior of the piles, and a comprehensive field/laboratory testing program at the field test site was also performed to describe the in situ rock mass conditions quantitatively. No correlation was found between the compressive strengths of intact rock and the side shear resistance of weathered/soft rock. The ground investigation data regarding the rock mass conditions (e.g. $E_m,\;E_{ur},\;_{plm}$, RMR, RQD, j) was found to be highly correlated with the side shear resistance, showing the coefficients of correlation greater than 0.7 in most cases. Additionally, the applicability of existing methods for the side shear resistance of piles in rock was verified by comparison with the field test data. The existing empirical relations between the compressive strength of intact rock and the side shear resistance(Horvath (1982), Rowe & Armitage(1987) etc.) appeared to overestimated the side shear resistance of all piles tested in this research unless additional consideration on the effect of rock mass weathering or fracturing was applied. The existing methods which consider the effect of rock mass condition were modified and/or extended for weathered rock mass where mass factor j is lower than 0.1, and RQD is below 50%.