ダム基礎地盤の浸透破壊抵抗性に関する基礎的研究

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Recently, in Japan, not a few dam sites are composed of soft rocks, such as sedimentary rocks of the Neogene, volcanic fall deposits of the Quaternary, weathered granites, and sand and gravel deposits. Soft rocks, and sand and gravel deposits are weak in strength compared to hard rocks. In addition, large seepage force will act on dam foundation during the filling of the reservoir. When dam foundation comprises of soft rocks or sand and gravel deposits, it is required to investigate whether seepage failure, such as piping, internal erosion and hydraulic fracturing, will occur, by laboratory or field test in the designing stage of dam. In this paper, we have first introduced the standard method of laboratory seepage failure test (SFT) using disturbed or undisturbed speciments collected from dam sites. Secondly we have examined the the relationship between critical hydraulic gradient (i_<cr>) obtained from laboratory SFT and results of laboratory soil tests, such as void ratio (e), coefficient of permeability (k) and unconfined compressive strength (q_u). This study has led to discovery of good correlation between i_<cr> and q_u. Thirdly we have investigated the anisotropy of i_<cr> and the difference in i_<cr> between disturbed and undisturbed speciments. This investigation has clarified the followings. According to the anisotropy of permeability, i_<cr> has the anisotropy. Although cement effect of undisturbed specimens has been recognized, they could have weak part in strength like fine fissure. Forthly the relationship between i_<cr> and value of resistance to scour obtained from scour test has been considered in details in order to grasp seepage failure potential of dam foundation with simpler method. Since good correlation has been obtained, seepage failure potential may easily be estimated by scour test. Finally we have proposed investigation procedure of seepage failure potential of dam foundation in consideration of the above-mentioned results.
一般社団法人日本応用地質学会の論文
1994-06-10

ダム基礎地盤の浸透破壊抵抗性に関する基礎的研究

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