Effect of Moisture on Attraction Force in Beach Sand     

TAE-HYUNG KIM  STEIN STURE 《Marine Georesources & Geotechnology》2013,31(1-2):33-47

Beach sands located above the sea water level exist in an unsaturated, rather than a fully saturated or dry state. Within the unsaturated zone, a steep excavated surface can be sustained for some unknown but finite time, and some slopes may remain stable for extended time periods due to capillary forces. These observations clearly indicate small but nonzero values for attraction strength (tensile strength and cohesion) in unsaturated beach sands, especially apparent but not confined to settings where there are low stress levels. Thus, experiments were carried out to quantify the magnitude of attraction strength in moist sands (D _r ?=?30%) and to examine the variation of these values as a function of moisture content and presence of a small amount of fines. Tensile strength, which is significantly different from zero, increases with increasing moisture content and fines. However, the influences of fines on the tensile strength are substantially dependent on the water content. Apparent cohesion strength is also identified in moist sands. A simple relationship between tensile strength and apparent cohesion is proposed using the obtained data. This study would help to further understand the phenomenon of stability of beach sands.  相似文献   

Side-Scan Sonar Characteristics and Manganese Nodule Abundance in the Clarion—Clipperton Fracture Zones,NE Equatorial Pacific     

SANG HOON LEE  KI-HYUNE KIM 《Marine Georesources & Geotechnology》2013,31(1-2):103-114

The deep ocean floor between the Clarion and Clipperton fracture zones (NE equatorial Pacific) has the highest known manganese nodule abundance in the world oceans. A detailed analysis of MR1 (Mapping Researcher 1, 11–12?kHz) sonar images and free-fall grab data in the Korean manganese nodule field areas reveals a close relationship between side-scan sonar characteristics of the seafloor and manganese nodule abundance. Eight sonar facies are identified based on back-scattering intensity and distribution patterns. These sonar facies can be interpreted as (1) volcanic seamounts (facies I-1), (2) bounding faults of abyssal hills (facies I-2 and II-1), (3) lava flows or volcanoclastic mass-flow deposits around the volcanic seamounts (facies I-3 and II-2), (4) crests of abyssal hills (facies II-1), (5) abyssal troughs between abyssal hills (facies III-1), (6) relatively flat areas (facies II-3 and III-2). In the areas where facies II-1 (abyssal hill crests with thin sediment cover) and II-3 (relatively flat areas draped by thin sediments) are dominant, manganese nodules occur abundantly. In contrast, zones comprising facies III-1 (abyssal troughs with thick sediment cover) and III-2 (relatively flat areas covered by thick sediments) are characterized by low abundance of manganese nodules. This relationship between distribution of sonar facies and manganese nodule abundance implies that (1) the qualitative difference in acoustic reflectivity of long-range side-scan sonar with some ground truth data is useful for regional assessment of manganese nodule occurrence over wide areas in a reasonable time, and (2) seafloor topography and sediment thickness are important controlling factors for regional occurrences of manganese nodules.  相似文献   

Geological and Geochemical Characteristics of the Hydrothermal Clay Alteration in South Korea   总被引：1，自引：1，他引：0  

Sang-Mo KOH  Tetsuichi TAKAGI  Moon–Young KIM  Kazuki NAITO  Sei–Sun HONG  Sadahisa SUDO 《Resource Geology》2000,50(4):229-242

Abstract: Hydrothermally altered areas forming pyrophyllite‐kaolin‐sericite‐alunite deposits are distributed in Chonnam and Kyongsang areas, Cretaceous volcanic field of the Yuchon Group. The Chonnam alteration area is located within depression zone which is composed of volcanic and granitic rocks of late Cretaceous age. The clay deposits of this area show the genetic relationship with silicic lava domes. The Kyongsang alteration area is mainly distributed within Kyongsang Basin comprising volcanic, sedimentary and granitic rocks of Cretaceous and Tertiary age. Most of the clay deposits of this area are closely related to cauldrons. Paleozoic clay deposit occurs in the contact zone between Precambrian Hongjesa granite gneiss and Paleozoic Jangsan quartzite of Choson Supergroup. Cretaceous igneous rocks of the both alteration areas belong to high K calc‐alkaline series formed in the volcanic arc of continental margin by subduction‐related magmatism. Chonnam igneous rocks show more enrichment of crustal components such as K, La, Ce, Sm, Nd and Ba, higher (La/Yb)cn ratio, and higher initial ⁸⁷Sr/⁸⁶Sr ratio (0. 708 to 0. 712) than those of Kyongsang igneous rocks. This might be due to the difference of degree of crustal contamination during Cretaceous magmatism. The most characteristic alteration minerals of Chonnam clay deposits are alunite, kaolin, quartz, pyrophyllite and diaspore which were formed by acidic solution. Those of Kyongsang clay deposits are sericite, quartz and pyrophyllite which were formed by weak acid and neutral solution. The formation ages of the clay deposits of two alteration areas range from 70. 1 to 81. 4 Ma and 39. 7 to 79. 4 Ma, respectively. The Daehyun clay deposit in Ponghwa area of Kyongsang province shows the alteration age range from 290 to 336 Ma. This result shows the different alteration episode from the hydrothermal alteration of Cretaceous to early Tertiary in the Kyongsang and Chonnam alteration areas. These data indicate, at least, three hydrothermal activities of Tertiary (middle to late Eocene), late Cretaceous (Santonian to Maastrichtian) and Paleozoic Carboniferous Periods in South Korea.  相似文献   

Hydrogeochemical Characteristics of Acid Mine Drainage around the Abandoned Youngdong Coal Mine in Korea     

Hyo–Taek CHON  Ju–Yong KIM  Si–Young CHOI 《Resource Geology》1999,49(2):113-120

Abstract: To determine the geochemical characteristics of the Imgok creek impacted by acid mine drainage (AMD) generated from the abandoned Youngdong coal mine in Korea, chemical analyses of water samples and precipitates and the geochemical modelling of the precipitates were conducted. Acid mine drainage drained from the mine adit and coal refuse piles shows a low pH, high conductivity and high concentrations of Fe, Al, SO₄ and heavy metals such as Co, Cu, Ni and Zn. In the Imgok creek, the concentrations of heavy metals and major cations besides Fe are decreased by dilution, but concentrations of Fe are decreased by the formation of precipitates as well as dilution. From the results of geochemical modelling, goethite is oversaturated, and schwertmannite is the most stable solid phase in the Imgok creek. Yellowish red Fe-precipitates collected at the Imgok creek are recognized as amorphous or poorly crystallized minerals from XRD patterns and Fe_ox/Fe_totratios, and as containing chemically bonded SO₄ and OH by an IR analysis. The mole ratios of Fe/S in these precipitates, which are determined by EPMA, are 5. 1 and 6. 1.  相似文献