• The Journal of Engineering Geology
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• v.23 no.3
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• pp.235-246
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• 2013

P-wave velocity was measured by the low frequency flaw detector in order to analyze the weathered state of a halo stone Buddha, Unju temple, Hwasun, Korea. By the results of laboratory tests on a fresh acidic tuff with the same rock of a halo stone Buddha, average absorption, average P-wave velocity, and average uniaxial compressive strength were 5.38%, 4,008 m/s, and 70.1 MPa, respectively. The results correspond to moderately strong rock. Average P-wave velocity of a halo stone Buddha measured by the low frequency flaw detector was 2,257 m/s in the left zone, 3,437 m/s in the right zone, and 2,802 m/s overall. Weathering index of a halo stone Buddha was 0.45 in the left zone, 0.21 in the right zone, and 0.33 overall. Comparing the results of a halo stone Buddha with them of laboratory tests, weathered state of a halo stone Buddha was analyzed highly weathered state in the left zone and moderately weathered state in the right zone. Furthermore, it suggests that the left zone of a halo stone Buddha was affected weathering more than the right one. Overall a halo stone Buddha corresponds to moderately weathered state of weathering degrees. In conclusion, it is considered that low frequency flaw detector may be applicable as a valuable method on analyzing the P-wave velocity of the stone cultural heritage with an irregular surface.

• Journal of the Korean Geotechnical Society
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• v.33 no.12
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• pp.127-139
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• 2017

Site investigation including boring and various in-situ borehole test (Pressuremeter test, Borehole shear test, Downhole test, Suspension PS logging, Density logging) and X-ray fluorescence analysis for rock core sample were performed to estimate geotechnical properties and weathering degree of weathered granite rock in Goyang. Deformation modulus, shear strength parameter and shear wave velocity estimated through in-situ borehole test had a tendency to increase with depth. And several chemical weathering indices evaluated by X-ray fluorescence analysis had a general tendency of reducing weathering degree in accordance with depth. Also, relationship between VR determined as a representative weathering index and the geotechnical properties was analyzed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6C
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• pp.431-443
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• 2006

As part of a fundamental characterization for subsurface layers in Korea, the weathering degree and shear wave velocity ($V_S$) were evaluated from the X-ray fluorescence analyses and the site investigations containing boring and in-situ seismic tests, respectively, for decomposed granite layer in Hongsung. The subsurface layers at Hongsung were composed of 10 to 40 m thickness of weathered layer in most sites. According to the results of weathering degree analyses in Hongsung, it was examined that three chemical weathering indexes such as MWPI, VR and WIP generally increased with decreasing depth. From the in-situ seismic tests, the $V_S$ was determined as the range between 200 and 500 m/s in weathered layer. Based on the $V_S$ and N value at borehole seismic testing sites, N-$V_S$ correlations were established for weathered layer. Furthermore, the relationships of three representative weathering indexes with the $V_S$ and N value indicated that the MWPI, WIP and 100/VR increased linearly as increasing $V_S$ and exponentially as increasing N value.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.127-140
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• 1999

In this study, decomposed granite soil samples were taken from 16 different regions and their weathering properties were investigated by testing their physical and chemical properties. According to the results, the Chemical Weathering Index (CWI) ranges from 15.5 to 30 in general and 12 out of the 16 regions show over 20 in CWI. The 12 regions are categorized into complete granite soil areas by Sueoka's classification. CWI, Li. $SiO_2,\; \DeltaS/S$ and SAR are all correlated significantly and used as indicators by which the degree of weathering can be judged. The degree of weathering can be measured especially through Li or $SiO_2$ which is considered as an easy approach of geotechnical classification. Also, the relationship between the value of N and Li is regarded as a good indicator in estimating the degree of weathering.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.69-78
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• 2003

In order to investigate the dynamic behavior of weathered granite soils before and after freezing-thawing, cyclic triaxial tests were conducted for the specimens not only with the variation of silt contents within 20% but with plasticity index within 20%. As the results, the dynamic shear modulus of weathered granite soils decreased with increasing silt contents. However, the change in damping ratio was negligible. The influence of freezing-thawing on shear modulus and damping ratio was minimal for the granite soils with variation of silt contents. For the case of the weathered soils with variation of plasticity index, the shear modulus increased with plasticity index within 20%, while the modulus decreased remarkably after freezing-thawing.

• Journal of the Korean association of regional geographers
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• v.18 no.1
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• pp.17-26
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• 2012

In Hwangtohyun, meaning 'red soil pass', reddish surface mantles is widespread. Other granitic hills, exceptionally Naju and Youngam area, in Korean peninsula don't commonly have that color. This paper attempts to address this issue by CIA(chemical index of alteration). CIA data and A-CN-K diagram provide crucial insights into the changes in the relative contributions of chemical physical weathering in difference of grus regolith and saprolite. CaO and $Na_2O$ show strong depletion and $K_2O$ is progressive loss. In grus regolith, weathering trends are (sub)parallel to the CN-A join of the A-CN-K diagram, but the sample's composition plot ever closer to the A-K join in saprolite. The difference of weathering trend obtained using CIA data corresponds closely with the visual interpretation of soil color and texture.

• Journal of the Mineralogical Society of Korea
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• v.14 no.1
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• pp.39-51
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• 2001

공주군 유구면 일대의 화강암질 편마암의 풍화작용에 따른 원소의 거동과 pH와 이차광물과의 관계를 XRF, ICP-AES, ICP-MS를 이용한 원소분석결과를 통하여 검토하였다. 이 지역의 암석은 pH6 내외의 산성환경, 침철석, 아나타제와 같은 다양한 이차광물을 생성하면서 심각한 화학조성의 변화를 초래했다. 주원소의 화학조성을 이용한 풍화지수는 토양층에서 79~88로 모암 중의 사장석이 용해되고 흑운모가 변질되어 캐올리광물의 생성이 활발한 방향으로 풍화작용이 진행되었다. 지표층으로 가면서 Al에 대한 주 원소의 거동은 Si, Ca, Na, K, P가 감소하고 Fe, Ti, Mn이 증가하는 경향을 보이며 pH가 낮은 풍화단면에서 주 원소의 변화량이 더 크다. 이 풍화대에서 Mg은 거의 일정하다. Li, As 모든 전이원소는 pH가 감소함에 따라 증가하며 특히 이들 원소는 Fe의 함량과 비례해서 증가해 침철석과 공침하였거나 표면에 흡착되어 있는 것으로 보인다. Ga은 Fe와 비례하기는 하지만 변화량은 전 풍화단면에서 일정하다. Zr, Mo, Sn, Cd은 pH에 변화에 상관없이 일정한 반면에 Rb, Sr, Ba, Y, Pb, Th, U 등은 감소하는 경향을 보인다. 특히 Rb 과 Sr은 Ca에 비례해서 감소한다. 희토류원소는 전 풍화단면에서 감소하는 경향을 보이는데 $Al_2$$O_3$에 대한 상대적인 변화량을 보면 경희토류원소는 사프롤라이트(saprolite)하부와 상부에서 부화되어 있고 중부 사프롤라이트와 토양층에서 감소하는 반면에 중희토류원소는 사프롤라이트 하부와 상부에서 감소하고 중부사프롤라이트 및 토양층에서 부화되는 경향을 보인다. 전반적으로 희토류원소의 원자번호가 클수록 손실율이 커진다. 이 풍화단면에서 원소의 거동은 각 풍화층의 pH와 생성된 이차광물의 조성에 지배를 받았다.

• Tunnel and Underground Space
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• v.19 no.4
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• pp.287-303
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• 2009

Rock mass in Baekrokdam at the summit of Hallasan in Jeju island is composed of two volcanic rock types: Baekrokdam trachybasalt at the eastern region and Hallasan trachyte at the western region. On-going rockfall and subsequent collapse of Baekrokdam wall rock are closely linked to the weathering of trachyte distributed in the western region of Baekrokdam. Samples of Hallasan trachyte showing different weathering grades had been collected and the polarizing microscopic observation, X-ray diffraction analysis and analysis for chemical weathering had been conducted. Formation of secondary minerals, especially clay minerals, by chemical weathering has not been identified, but the change of chemical weathering indices indicated that chemical weathering process had been proceeded to the degree for increasing and decreasing the contents of some chemical components. Changes in physical and mechanical rock properties due to weathering has also been examined. Artificial weathering test of freezing-thawing reveals that the process of crack initiation and propagation deteriorated the mechanical characteristics of Hallasan trachyte and $D_B$ = 1.5 or porosity = $20{\sim}21%$ would be the ultimate limiting value induced by the mechanical weathering processes.

• Journal of the Korean Geosynthetics Society
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• v.12 no.1
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• pp.1-10
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• 2013

In this study, the characteristics of particle crash of decomposed granite soil sampled at Pocheon area were presented. The degree of weathering was artificially achieved by means of hydrofluoric acid. Weathering index was firstly determined by the analysis of mineral composition. Then, particle distribution, permeability tests were conducted. The results showed that weathering effects on particle crash over entire particle sizes. Comparative analysis on specific surface between $D_{10}$ and $D_{50}$ indicated that the smaller the particle size, the more the particle crash. In addition, the most particle crashing due to compaction appeared around the optimum moisture content. The incremental ratio of specific surface appeared to decrease as weathering proceeds, which means that the higher the weathering index the less the particle crash.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.381-391
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• 2011

Weathering can reduce rock strength and eventually affect the structural stability of a rock mass, which is important in the field of engineering geology. Several methods have been developed to evaluate the degree of weathering, including the chemical weathering index. In this study, we analyzed the weathering degree and characteristics of microtextures and pores in crystalline rocks (gneiss and granites) based on petrographic observations, the chemical weathering index, mineralogy by XRD, microtextural analysis by SEM/EDS, measurements of pore size and surface area by the BET method, and microporosity by X-ray CT. The formation of secondary minerals and microtexture in gneiss and granitic rocks are assumed to be affected by complex processes such as dissolution, precipitation, and fracturing. Hence, it is clear that some chemical weathering indices that are based solely on whole-rock chemistry (e.g., CIA and CWI) are unable to provide reliable assessments of the degree of weathering. Great care is needed to evaluate the degree of chemical weathering, including an understanding of the mineralogy and microtexture of the rock mass, as well as the characteristics of micropores.