Engineering Properties of The Ryukyu Limestone by Schmidt-Rock-Hammer in South-East part of Miyakojima, the Ryukyu Islands
Engineering Properties of The Ryukyu Limestone by Schmidt-Rock-Hammer in South-East part of Miyakojima, the Ryukyu Islands
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琉球群岛宫古岛东南部施密特岩锤研究琉球石灰岩的工程特性
DOI：
10.5110/jjseg.30.1
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Yoshimi Zaha
中科院分区：
文献类型：
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作者：
M. Imaizumi;T. Tomita;Yoshimi Zaha
本文研究了广泛暴露于琉球群岛宫古岛东南部的更新世琉球群中琉球灰岩的工程性质和成岩作用过程。在宫古岛发现的喀斯特地形包括石灰岩墙和土丘。石灰岩岩壁是沿正断层的一排山脊。根据所含化石和岩石基质的不同，将琉球灰岩主要分为四种沉积相：含珊瑚和碎屑的珊瑚碎屑灰岩、含原生珊瑚和藻席的珊瑚藻席灰岩、含藻球或红白云石的藻球灰岩、含钙质有机残骸碎屑的碎屑灰岩。琉球灰岩的抗压强度在1 ~ 400 kgf/cm2范围内分布较广。为了了解琉球灰岩的区域工程性质，我们利用Schmid-Rock-Hammer测量了宫古岛露头灰岩的回弹值以及岩石物理性质，如密度、比重、孔隙度和抗压强度。结果表明：1)根据回弹值的频率，可以识别出3种类型：藻席灰岩和藻球灰岩的回弹值较高；珊瑚碎屑灰岩的回弹值较低。碎屑灰岩的回弹值范围较大。2)回弹值较高的区域对应于灰岩壁岩溶地形以及由藻席灰岩和藻球灰岩组成的分布区域。而回弹值较低的区域对应于珊瑚碎屑灰岩。3)考虑空腔，回弹值与孔隙度有关。这些结果使我们提出以下假设：碳酸盐沉积物的成岩作用受各沉积相的初始孔隙度、胶结作用和大气水入渗引起的溶蚀作用的影响。胶结作用发生在成岩作用早期，导致原生孔隙度降低，强度增大。溶蚀作用形成的次生孔隙会导致强度的一定降低。
This article deals with engineering properties and diagenesis process of the Ryukyu Limestone belonging to the Pleistocene Ryukyu Group widely exposed on south-east part of Miyakojima of the Ryukyu Islands.Karst topography found within Miyakojima includes limestone wall and mound. Limestone wall is the row of ridges along normal faults.On the basis of fossils contained and matrix of the rocks, the Ryukyu limestone is classified principally into four sedimentary facies: coral detrital limestone which contains corals and detritus, coral algal-mat limestone which contains autochthonous corals and algal-mat, algal ball limestone containing algal ball or rhodolites, detrital limestone which consists of detritus of calcareous organic remains.Compressive strength of the Ryukyu limestone shows a wide scatter from 1 to 400 kgf/cm2. To know regional engineering properties of the Ryukyu limstone, we measured rebound value of limestone on outcrops in Miyakojima by a Schmid-Rock-Hammer and petropysical properties such as density, specific gravity, porosity and compressive strength.The results are summarized as follows:1) On the basis of frequency of rebound values, three patterns are recognized: Coral algal-mat limestone and algal ball limestone showe hihger rebound value. Coral detrital limestone shows lower rebound value. Detrital limestone shows a wide range rebound values.2) The higher rebound value zones correspond to the karst topography of limestone wall and distribution zones composed of coral algal-mat limestone and algal ball limestone. Whereas lower rebound value zones correspond to coral detrital limestone.3) Rebound values have relation with porosities taking into account of the cavities.These results led us to the following hypothesis: Diagenesis of the carbonate sediments is influenced by initial porosity of each sedimentary facies, cementation and solution caused by infiltration of meteoric water. Cementation would have occured in a early stage of diagenesis process, and brought on the decrease of primary porosity and the increase of strength. Formation of secondary porosity by solution would cause the some decrease of strength.