➨  ᅇᅵ◁⅏ᐖ࡟㛵ࡍࡿࢩ࣏ࣥࢪ࣒࢘ㄽᩥ㞟㸪 ᖺ  ᭶ ᖺ໭ᾏ㐨⫹᣺ᮾ㒊ᆅ㟈࡛Ⓨ⏕ࡋࡓࢸࣇࣛᒙࡍ࡭ࡾ࡟࠾࠸࡚␗࡞ࡿሙᡤ࡛᥇ྲྀࡋࡓ
7DG ᒙࡢᐃయ✚⧞㏉ࡋ୍㠃ࡏࢇ᩿≉ᛶ

CHARACTERISTICS OF CONSTANT VOLUME CYCLIC DIRECT BOX SHEAR TESTSON TA-D TEPHRA LAYERS SAMPLED FROM DIFFERENT PLACES CAUSEDBY 2018 HOKKAIDO EASTERN IBURI EARTHQUAKE኱ᕝཎ ඃᕼ 1࣭ᚋ⸨ ⪽ 2࣭ᑠᖭ 㞙ኈ 3࣭㝞 ᰓᏱ 1࣭▼୸ ⪽ 4࣭ᑠᏳ ᾈ⌮ 4࣭Ώ㒊 ┤႐ 5Yuki OKAWARA, Satoshi GOTO, Shuji OBATA, Keyu CHEN,Satoshi ISHIMARU,Hiromichi KOYASU and Naoki WATANABE1 ᒣ᲍኱Ꮫ኱Ꮫ㝔་ᕤ㎰Ꮫ⥲ྜᩍ⫱㒊ᅵᮌ⎔ቃᕤᏛࢥ࣮ࢫ㸦ࠛ400-8511 ᒣ᲍┴⏥ᗓᕷṊ⏣ᅄ୎┠ 3 ␒ 11 ྕ㸧2 ᒣ᲍኱Ꮫ኱Ꮫ㝔⥲ྜ◊✲㒊ᕤᏛᇦᅵᮌ⎔ቃᕤᏛ⣔E-mail㸸goto@yamanashi.ac.jp
3 ᒣ᲍኱ᏛᕤᏛ㒊ᅵᮌ⎔ቃᕤᏛ⛉4 ໭ᾏ㐨⥲ྜ◊✲ᶵᵓ㸦ࠛ060-0819 ໭ᾏ㐨ᮐᖠᕷ໭༊໭ 19 ᮲す 12 ୎┠㸧
5 ᪂₲኱Ꮫ⅏ᐖ࣭᚟⯆⛉Ꮫ◊✲ᡤ㸦ࠛ950-2181 ᪂₲┴᪂₲ᕷす༊஬༑ᔒ 2 ࡢ⏫ 8050 ␒ᆅ㸧

Key Words: cyclic direct box shear tests, Hokkaido Eastern Iburi Earthquake, tephra layered landslide ࡣࡌࡵ࡟
2018 ᖺ 9 ᭶ 6 ᪥࡟໭ᾏ㐨⫹᣺ᆅ᪉୰ᮾ㒊ࢆ㟈※࡜ࡍࡿ໭ᾏ㐨⫹᣺ᮾ㒊ᆅ㟈ࡀⓎ⏕ࡋࡓ㸬ࡇࡢᆅ㟈࡟ࡼࡾ໭ᾏ㐨ຬᡶ㒆ཌ┿⏫ࢆ୰ᚰ࡟㸪ࢸࣇࣛᒙࢆࡍ࡭ࡾ㠃࡜ࡍࡿᩳ㠃ᔂቯ㸦௨ୗ㸪ࢸࣇࣛᒙࡍ࡭ࡾ㸧ࡀ⩌Ⓨࡋࡓ㸬ࡇࡢᆅᇦ࿘㎶࡛ࡣ㝆ୗࢸࣇࣛࡀཌࡃሁ✚ࡋ࡚࠾ࡾ㸪ୖ఩ࡼࡾ㸪ᶡ๓ⅆᒣ࠿ࡽ⣙ 300㹼400 ᖺ๓࡟㣕᮶ࡋࡓᶡ๓ a,b 㝆ୗⅆ○ሁ✚≀㸦௨ୗ㸪Ta-a㸪Ta-b㸧㸪ྠࡌࡃ 3000 ᖺ๓ࡢᶡ๓ c 㝆ୗⅆ○ሁ✚≀㸦௨ୗ㸪Ta-c㸧㸪ྠࡌࡃ 9000 ᖺ๓࡟㣕᮶ࡋࡓᶡ๓ d 㝆ୗⅆ○ሁ✚≀㸦௨ୗ㸪Ta-d㸧1)㸪ࡉࡽ࡟㸪ᜨᗞᓅⅆᒣ࠿ࡽ⣙ 2୓ᖺ๓࡟㣕᮶ࡋࡓᜨᗞ a 㝆ୗⅆ○ሁ✚≀㸦௨ୗ㸪En-a㸧2㸧㸪ࡑࡋ࡚⣙㸲୓ᖺ๓ࡢᨭ➖࢝ࣝࢹࣛᙧᡂᄇⅆ࡟ࡼࡾ㣕᮶ࡋ3)ࡓᨭ➖ a 㝆ୗⅆ○ሁ✚≀ 1㸦Spfa-1㸧࠿ࡽᙧᡂࡉࢀ࡚࠸ࡿ㸬4)▼୸ࡽ ࡣ㸪⫹᣺ᮾ㒊ᆅ㟈࡛኱ከᩘࢆ༨ࡵࡿᔂቯᵝᘧ࡜࡞ࡗࡓࢸࣇࣛᒙࡍ࡭ࡾࢆᑐ㇟࡜ࡋ࡚㸪ࢸࣇࣛᒙࡢⓎ㐩ࡍࡿୣ㝠ᆅ࡟࠾࠸࡚㸪ᆅᙧⓎ㐩ྐⓗほⅬ࠿ࡽ㸪ᩳ㠃ᔂቯࡢ⏕ࡌࡸࡍ࠸ᆅᙧሙࡸ⾲ᒙᆅ㉁࡟ࡘ࠸᳨࡚ウࡋ㸪ࡑࡢ≉ᚩࢆሗ࿌ࡋ࡚࠸ࡿ㸬ከࡃࡢ≛≅⪅ࢆฟࡋࡓ Ta-d ᒙࡀཌࡃศᕸࡍࡿྜྷ
㔝ᆅ༊ࡸᮅ᪥ᆅ༊ࡢഃቨࡢᅵᒙほᐹࢆ⾜ࡗࡓ࡜ࡇࢁ㸪ࡍ࡭ࡾ㠃࡜࡞ࡗࡓࡢࡣ Ta-d ᭱ୗ㒊ࡢỈศࢆྵࡴ⣽⢏㍍▼ᒙ࡛࠶ࡗࡓࡇ࡜ࢆ☜ㄆࡋ࡚࠸ࡿ㸬
Goto and Okada5)ࡣ㸪ⲡ༓㔛ࣨ὾㝆ୗ㍍▼ࢆᑐ㇟࡟㸪ᆅ᫬࡟࠾ࡅࡿ⧞㏉ࡋࡏࢇ᩿≉ᛶࢆᢕᥱࡍࡿࡓࡵ㸪ᐃᅽ࣭ᐃయ✚᮲௳ୗ࡛ࡢ⧞㏉ࡋ୍㠃ࡏࢇ᩿ヨ㦂ࢆᐇ᪋ࡋࡓ㸬Li et al.6)ࡣ㸪⫹᣺ᮾ㒊ᆅ㟈࡟ࡼࡗ࡚Ⓨ⏕ࡋࡓࢸࣇࣛᒙࡍ
࡭ࡾࢆᑐ㇟࡟㸪ཌ┿⏫ᮅ᪥ᆅ༊࡛᥇ྲྀࡋࡓ Ta-d ᒙࢆᑐ㇟࡟㸪ྛ✀≀⌮ヨ㦂ཬࡧຊᏛヨ㦂ࢆᐇ᪋ࡋࡓ㸬Ta-d ᒙࢆⰍ㸪⢏ᚄ㸪ᙉᗘࢆᇶ࡟㸲✀㢮࡟ศ㢮ࡋ㸪ຍ࠼࡚ Ta-d ᒙࡢୗ఩࡟
ሁ✚ࡍࡿ Paleosol(ࢩࣝࢺᒾ㉳※ࡢྂᅵተ)࡟࠾࠸࡚୕㍈ᅽ⦰ヨ㦂ཬࡧ⧞㏉ࡋ୕㍈ヨ㦂ࢆᐇ᪋ࡋࡓ㸬Ⲩ∾ࡽ 7)ࡣ㸪ⅆᒣ⅊ᅵࡀ≉Ṧᅵ࡜ࡋ࡚ᢅࢃࢀࡿࡇ࡜ࡀከࡃ㸪≀⌮ⓗㅖᛶ㉁ࡢ ᐃ࡟ࡣ㸪ࡤࡽࡘࡁࡀከࡃ࡞ࡿࡇ࡜ࡀண᝿ࡉࢀࡿ࡜ሗ࿌ࡋ࡚࠸ࡿ㸬ᅵ⢏Ꮚෆ㛫㝽ࢆ᭷ࡍࡿⅆᒣ⅊― 49 ―

Ta-d ཬࡧᮍ㢼໬ࡢ Ta-d ࡣㄪᰝࡋࡓᔂቯᩳ㠃࡟࠾࠸࡚ᒙࡀᅵࢆᑐ㇟࡟㸪ᅵ⢏Ꮚࡢᐦᗘヨ㦂ཬࡧ⢏ᗘヨ㦂ࢆᐇ᪋ࡋ㸪ヨ኱ࡁࡃ‴᭤ࡋ㸪ᒙཌࡀኚ໬ࡋ࡚࠸ࡿࡇ࡜ࡀ☜ㄆ࡛ࡁࡓ㸬ⴭ㦂ࡢ‽ഛ≧ἣࡸᐇ㦂᪉ἲ࡟࠾ࡅࡿ ᐃࡢࡤࡽࡘࡁ࡟ཬࡰ⪅ࡽࡣ㸪2020 ᖺ 10 ᭶࡟ᮾ࿴ᕝ໭ᨭὶࡢྠࡌᔂቯᩳ㠃࡟࠾ࡍᙳ㡪ᅉᏊ࡟ࡘ࠸᳨࡚ウࡋ࡚࠸ࡿ㸬࠸࡚㟢㢌ㄪᰝࢆᐇ᪋ࡋ࡚࠸ࡿ 12)㸬2020 ᖺ࡜ 2021 ᖺ࡟ほᐹ⫹᣺ᮾ㒊ᆅ㟈࡟ࡼࡗ࡚Ⓨ⏕ࡋࡓࢸࣇࣛᒙࡍ࡭ࡾࡢࡍ࡭ࡾ㠃࡞ࡽࡧ࡟㸪ࢸࣇࣛᒙࡢᒙཌཬࡧ㢼໬ࡢ௙᪉ࡸ⛬ᗘࡣࢸࡋࡓ㟢㢌ࡀᩘ࣓࣮ࢺࣝࡋ࠿㞳ࢀ࡚࠸࡞࠸࡟ࡶ࠿࠿ࢃࡽࡎ㸪ࣇࣛᒙࡍ࡭ࡾࡢⓎ⏕ሙ࡟ࡼࡗ࡚␗࡞ࡿ㸬ᮏࡍ࡭ࡾ࡟㛵ࡍࡿTa-d ࡢ㢼໬ᒙࡢᒙཌࡀ኱ࡁࡃ␗࡞ࡿ⤖ᯝ࡜࡞ࡗࡓ㸬8)ຊᏛ≉ᛶ࡟ࡘ࠸࡚㸪⋤ࡽ ࡢ༢ㄪ㍕Ⲵࡢ⌧ሙ୍㠃ࡏࢇ᩿ヨᅗ E ࡟ᮾ࿴ᕝ༡ᨭὶ࡛ㄪᰝࡋࡓ㟢㢌ࡢᒙᗎ࣭ᒙཌࢆ♧ࡍ㸬ୖ఩࠿ࡽ㸪⾲ᅵ㸪Ta-b㸪Ta-c㸪Ta-d ࣮࣒ࣟ㸪〓Ⰽ㢼໬㦂ཬࡧ⥳ᕝࡽ 9)ࡸ Li et al.6)ࡢ ⧞㏉ࡋ㠀᤼Ỉ୕㍈ᅽ⦰ヨ㦂Ta-d㸪Ta-d ⢒⢏㸪Ta-d ⣽⢏㸪En-a ࣮࣒ࣟࡀሁ✚ࡍࡿ㸬࡯࡜࡟ࡼࡿ◊✲ࡀሗ࿌ࡉࢀ࡚࠸ࡿࡀ㸪␗࡞ࡿሙᡤ࡟࠾࠸࡚≀⌮ⓗᛶ㉁ࡸࡏࢇ᩿≉ᛶࢆẚ㍑᳨ウࡋࡓ◊✲ࡣ࡯࡜ࢇ࡝࡞࠸㸬 ࢇ࡝ࡢᒙቃ⏺ࡀᆅ⾲㠃࡜࡯ࡰᖹ⾜࡟࡞ࡗ࡚࠸ࡿࡇ࡜ࡀ☜ㄆ࡛ࡁ㸪ᮾ࿴ᕝ໭ᨭὶ࡜ࡣ␗࡞ࡿ≉ᚩࢆ♧ࡋࡓ㸬ᗈᇦᩳ㠃࡟࠾࠸࡚ᩳ㠃Ᏻᐃゎᯒࢆ⾜࠺ࡓࡵ࡟ࡣ㸪ࢸࣇࣛᒙᅗ F ࡟ࢩࣗࣝࢡἑ࡛ㄪᰝࡋࡓ㟢㢌ࡢᒙᗎ࣭ᒙཌࢆ♧ࡍ࡭ࡾࡢ␗࡞ࡿሙᡤ࡟࠾ࡅࡿ≀⌮≉ᛶཬࡧࡏࢇ᩿≉ᛶࢆࡍ㸬ୖ఩࠿ࡽ㸪⾲ᅵ㸪Ta-b㸪ࢡࣟ࣎ࢡ㸪Ta-c㸪Ta-d ࣮࣒ࣟ㸪ホ౯᳨ウࡍࡿᚲせࡀ࠶ࡿ㸬ࢡ࣮࣒ࣜ≧㢼໬ Ta-d㸪
Ta-d ⢒⢏㸪Ta-d ⣽⢏㸪ᮏㄽᩥ࡛ࡣ㸪ཌ┿⏫࡛Ⓨ⏕ࡋࡓࢸࣇࣛᒙࡍ࡭ࡾࢆᑐ㇟࡟㸪 〓Ⰽ㢼໬ Ta-d㸪
En-a ࣮࣒ࣟࡀሁ✚ࡍࡿ㸬ࢩࣗࣝࢡἑ࡛ࡣࢡ࣮࣒ࣜ≧㢼໬ཌ┿⏫ᮾ࿴ᆅ༊ᮾ࿴ᕝ໭ᨭὶ㸦௨ୗ㸪ᮾ࿴ᕝ໭ᨭὶ㸧㸪ᮾ࿴ᆅ༊ᮾ࿴ᕝ༡ᨭὶ㸦௨ୗ㸪ᮾ࿴ᕝ༡ᨭὶ㸧㸪ᖠෆᆅ༊ࢩࣗࣝࢡἑ୰ὶ㸦௨ୗ㸪ࢩࣗࣝࢡἑ㸧࡛᥇ྲྀࡋࡓ Ta-d ⣽⢏ࡢヨᩱ࠿ࡽ㸪␗࡞ࡿሙᡤ࡟࠾ࡅࡿ≀⌮ⓗᛶ㉁ࡸᐃయ✚⧞㏉ࡋ୍㠃ࡏࢇ᩿≉ᛶ࡟ࡘ࠸࡚⪃ᐹࡋࡓ㸬Ta-d ศᕸᇦࡢ࠺ࡕ㸪Ta-d ᒙཌࡢ࡯ࡰྠࡌሙᡤࢆ㑅ࢇ࡛ẚ㍑᳨ウࡋࡓ㸬 ⌧ᆅㄪᰝ
2021 ᖺ 10 ᭶࡟ᮾ࿴ᕝ໭ᨭὶ㸪2021 ᖺ 11 ᭶࡟ᮾ࿴ᕝ༡ᨭὶཬࡧࢩࣗࣝࢡἑ࡛㸪⌧ᆅㄪᰝཬࡧヨᩱࡢ᥇ྲྀࢆᐇ᪋ࡋࡓ㸬ᅗ  ࡟ㄪᰝᆅⅬཬࡧ Ta-d ᒙࡢ࢔࢖ࢯࣃࢵࢡ࣐ࢵࣉࢆ♧ࡍ㸬࢔࢖ࢯࣃࢵࢡ࣐ࢵࣉࡣྂᕝ࣭୰ᕝ 10)ࡀసᡂࡋࡓ Tad ࡢ࢔࢖ࢯࣃࢵࢡ࣐ࢵࣉࢆࡶ࡜࡟సᡂࡋࡓ㸬࡞࠾㸪⫼ᬒࡢᆅᅗࡣ㸪ᅜᅵᆅ⌮㝔ᆅᅗࡼࡾᘬ⏝ࡋࡓ㸬ᅗ D ࡟ᮾ࿴ᕝ໭ᨭὶ࡛ㄪᰝࡋࡓ㟢㢌ࡢᒙᗎ࣭ᒙཌࢆ♧ࡍ㸬ୖ఩࠿ࡽ㸪⾲ᅵ㸪Ta-c㸪Ta-d ࣮࣒ࣟ㸪〓Ⰽ㢼໬ Ta-d㸪ࢡ࣮࣒ࣜ≧㢼໬ Ta-d㸪Ta-d ⢒⢏㸪Ta-d ⣽⢏㸪En-a ࣮࣒ࣟࡀሁ✚ࡍࡿ㸬ᮾ࿴ᕝ໭ᨭὶࡢ〓Ⰽ㢼໬ Ta-d㸪ࢡ࣮࣒ࣜ≧㢼໬㸦D㸧ᮾ࿴ᕝ໭ᨭὶᅗ ⌧ᆅㄪᰝࡢᆅⅬཬࡧ࢔࢖ࢯࣃࢵࢡ࣐ࢵࣉ  㸦E㸧ᮾ࿴ᕝ༡ᨭὶᅗ ヨᩱ᥇ྲྀࡋࡓᆅⅬࡢᒙᗎ࣭ᒙཌ

― 50 ―㸦F㸧ࢩࣗࣝࢡἑ

㏻㐣㉁㔞ⓒศ⋡(%)ࡏࢇ᩿ᛂຊ 㸦kPa㸧㸱 ⢏ᗘศᕸ
JIS ἲ࡟ࡼࡿ⢏ᗘヨ㦂᪉ἲࡣ㸪2mm ࡩࡿ࠸ࡢ㏻㐣ヨᩱࢆ⏝࠸࡚ỿ㝆ศᯒࢆ⾜࠺ࡀ㸪ᅵ⢏Ꮚෆ࡟✵㝽ࡀ࠶ࢀࡤ኱ࡁ࠸⢏Ꮚࡼࡾࡶඛ࡟ᑠࡉ࠸⢏Ꮚࡀỿ㝆ࡍࡿྍ⬟ᛶࡀ኱ࡁ࠸㸬ࡲࡓ㸪ࢸࣇࣛࡢᅵ⢏Ꮚࡣ⬤ࡃ㸪ゎࡁ࡯ࡄࡋࡢ㝿ࡢヨᩱ࡬ࡢᡴᧁ㸪ᜏ ஝⇱⅔࡛ࡢ㐣⇕➼࡟ࡼࡗ࡚◚○࣭᩿∦໬ࡍࡿࡓࡵ㸪ཎ఩⨨ࡢ⢏ᗘࡢ෌⌧ࡣ㞴ࡋ࠸㸬ࡑࡇ࡛ᮏㄽᩥ࡛ࡣⲨ∾ࡽ 6)
ࡼࡿヨ㦂᪉ἲ࡛⢏Ꮚࡀ◚○ࡋ࡞࠸ࡼ࠺࡟ᕤኵࡋ⢏ᗘヨ㦂ࢆᐇ᪋ࡋࡓ㸬ᅗ ࡟ᮾ࿴ᕝ໭ᨭὶ࡟࠾ࡅࡿ Ta-d ⢒⢏ཬࡧ Ta-d ⣽⢏ࡢ⢏ᚄຍ✚᭤⥺ࢆ♧ࡍ㸬3 ࡘࡢ␗࡞ࡿሙᡤ࡛᥇ྲྀࡋࡓ Ta-d ⣽⢏࡜ Ta-d ⢒⢏ࡣ᫂ࡽ࠿࡟␗࡞ࡿ⢏ᗘศᕸࢆ♧ࡋࡓ㸬⢏ᚄࡀ
0.075mm ௨ୗࡢ⢏Ꮚࡣ 20%࠿ࡽ 30㸣⛬ᗘ࡛࠶ࡗࡓ㸬⢒⢏ᅵ࡟௜╔ࡋࡓ⣽⢏ᅵࡀỈὙ࠸ࡢᕤ⛬࡛ὶኻࡋࡓࡓࡵࡔ࡜⪃࠼ࡽࢀࡿࡀ㸪Ta-d ⣽⢏ࡣ⢏ᚄࡀ 0.075mm ௨ୖ࡛ྠᵝ࡞⢏ᗘศᕸࢆ♧ࡋࡓ㸬ࡘࡲࡾ㸪␗࡞ࡿሙᡤ࡟ศᕸࡋ࡚࠸ࡿ Tad ⣽⢏࡟࠾࠸࡚⢏ᗘศᕸࡀ㢮ఝࡍࡿࡇ࡜ࡀ☜ㄆ࡛ࡁࡓ㸬⢏ᚄ⢏ᚄ(mm)

ᅗ ␗࡞ࡿሙᡤ࡟࠾ࡅࡿ
7DG ⣽⢏ࡢ⢏ᚄຍ✚᭤⥺ᆶ┤ᛂຊ 㸦kPa㸧㸦D㸧 ࢫࢺࣞࢫࣃࢫࡏࢇ᩿ᛂຊ 㸦kPa㸧

Ta-d ࡀ୙つ๎࡟Ꮡᅾࡋ㸪En-a ࣮࣒ࣟࡀཌࡃሁ✚ࡋ࡚࠸ࡿࡇ࡜ࡀศ࠿ࡿ㸬ᅗ ࡼࡾ㸪3 ᆅⅬ࡟࠾ࡅࡿᒙᗎࡣ㸪ᴫࡡ୍⮴ࡋ㸪Tad ࡢᒙཌࡀ㠀ᖖ࡟ཌ࠸ࡇ࡜ࡀ☜ㄆ࡛ࡁࡓ㸬ᅗ ࡢ࢔࢖ࢯࣃࢵࢡ࣐ࢵࣉ࡟ࡼࢀࡤㄪᰝࡋࡓ 3 ᆅⅬࡣ Ta-d ᒙཌࡀࡍ࡭࡚ 100cm ௨ୖࡢ⠊ᅖ࡟࠶ࡿࡀ㸪ᐇ㝿 ᐃࡋࡓᒙཌࡣ㸪ᮾ࿴ᕝ໭ᨭὶ࡛ 99cm㸪ᮾ࿴ᕝ༡ᨭὶ࡛ 73cm㸪ࢩࣗࣝࢡἑ࡛ 96cm ࡜ 100cm ࢆୗᅇࡗࡓ㸬࡞࠾㸪Ta-d ࣮࣒ࣟࡣ෌ሁ✚≀ࡢࡓࡵ㸪Ta-d ᒙࡢᐇ ཌ࠿ࡽ㝖࠸ࡓ㸬ᮍ㢼໬ࡢ Tad ᒙࡣ⢏ᚄ࡟኱ࡁ࡞㐪࠸ࡀࡳࡽࢀࡓࡓࡵ㸪Ta-d ᒙࡢᗏ㒊ࢆ Ta-d ⣽⢏㸪ࡑࢀࡼࡾୖࢆ Ta-d ⢒⢏࡜༊ูࡋࡓ㸬㸬᥇ྲྀࡋࡓヨᩱࡢᐃయ✚⧞㏉ࡋ୍㠃ࡏࢇ᩿≉ᛶE ᐃయ✚⧞㏉ࡋ୍㠃ࡏࢇ᩿ヨ㦂ᮏㄽᩥࡣ㸪ᮾ࿴ᕝ໭ᨭὶཬࡧᮾ࿴ᕝ༡ᨭὶ㸪ࢩࣗࣝࢡἑ
ࡢィ 3 ᆅⅬ࡟࠾࠸࡚ Ta-d ⣽⢏ࡢ஘ࢀࡢᑡ࡞࠸ヨᩱࢆ᥇ྲྀࡋࡓ㸬ᆅ㟈᫬ࡢ⧞㏉ࡋࡏࢇ᩿࡟࠾ࡅࡿᆅ┙≧ែࡣᐃᅽཬࡧᐃయ✚᮲௳ୗ࡛ࡏࢇ᩿ࡉࢀ࡚࠸ࡿࡇ࡜ࡣᐃ࠿࡛ࡣ࡞࠸ࡓࡵ㸪ᮏㄽᩥ࡛ࡣ㸪ᐃయ✚᮲௳࡜௬ᐃࡋ㸪⧞㏉ࡋ୍㠃ࡏࢇ᩿≉ᛶࢆẚ㍑᳨ウࡋࡓ㸬࡞࠾㸪ࡏࢇ᩿㏿ᗘࡣ㸪1.55mm/min㸪ึᮇᆶ┤ᛂຊࡣ㸪100kPa㸪ࡏࢇ᩿ᛂຊ᣺ᖜࢆ±60kPa ࡜ࡋࡓ㸬ࡏࢇ᩿᣺ᖜᛂຊ࡟㐩ࡉ࡞࠸ሙྜࡣࡏࢇ᩿ኚ఩ࡀ±10mm ࡛ࡏࢇ᩿᪉ྥࢆ཯㌿ࡉࡏࡓ㸬 ヨ㦂⤖ᯝ࠾ࡼࡧ⪃ᐹᅗ ࡟␗࡞ࡿሙᡤ࡛᥇ྲྀࡋࡓ Ta-d ⣽⢏ࡢᐃయ✚⧞㏉ࡋ୍㠃ࡏࢇ᩿ヨ㦂⤖ᯝࢆ♧ࡍ㸬ᅗ D ࡟ࡳࡽࢀࡿ࡜࠾ࡾ㸪୕ࡘࡢࢫࢺࣞࢫࣃࢫࡀ㔜࡞ࡿ⤖ᯝࢆ♧ࡋࡓ㸬ࡘࡲࡾࡏࢇ᩿᢬
ᢠゅȭཬࡧ⢓╔ຊ㹡ࡀ㢮ఝࡋࡓ್ࢆ♧ࡍࡇ࡜࡟࡞ࡗࡓ㸬ᅗࡏࢇ᩿ኚ఩ 㸦mm㸧ࡏࢇ᩿ኚ఩࡜ࡏࢇ᩿ᛂຊࡢ㛵ಀᅗ ␗࡞ࡿሙᡤ࡟࠾ࡅࡿ 7DG ⣽⢏ࡢᐃయ✚⧞㏉ࡋ୍㠃ࡏࢇ᩿ヨ㦂⤖ᯝ E ࡢࡏࢇ᩿ኚ఩࡜ࡏࢇ᩿ᛂຊࡢ㛵ಀࡼࡾ㸪ᮾ࿴ᕝ༡ᨭὶཬࡧࢩࣗࣝࢡἑࡢヨᩱ࡛ࡣ㸪ࡏࢇ᩿ᅇᩘ 2 ᅇ┠ࡲ࡛ࡣ㸪ᡤᐃࡢࡏࢇ᩿ᛂຊ᣺ᖜ࡟㐩ࡋࡓࡀࡏࢇ᩿ᅇᩘ3ᅇ┠௨㝆ࡣ⧞㏉ࡋࡏࢇ᩿࡟ࡼࡾࡏࢇ᩿ᛂຊࡀపୗࡋࡓ㸬ᮾ࿴ᕝ໭ᨭὶ
ࡢヨᩱࡣ㸪ᡤᐃࡢࡏࢇ᩿ᛂຊ᣺ᖜ࡟฿㐩ࡏࡎᙉᗘࡀపୗࡍࡿ⌧㇟ࡀࡳࡽࢀࡓ㸬࠸ࡎࢀࡶ᭱⤊ⓗ࡟ࡣࡏࢇ᩿ᛂຊࡀᑠࡉ
࡞್࡛ࡢ⧞㏉ࡋᣲື࡜࡞ࡗࡓ㸬ᮾ࿴ᕝ໭ᨭὶࡢヨ㦂ᚋ౪ヨయࡢࡏࢇ᩿㠃ࢆᅗ D ࡟♧ࡍ㸬ࡏࢇ᩿㠃࡟⢓ᛶᅵ࡟㢮ࡍࡿ⣽⢏≀ࡀࡳࡽࢀ㸪En-a ㉳※࣮࣒ࣟࡀΰᅾࡋ࡚࠸ࡓ㸬ᅗ E ࡟ᮾ࿴ᕝ༡ᨭὶࡢヨ㦂ᚋ౪ヨయࡢࡏࢇ᩿㠃ࢆ♧ࡍ㸬Ta-d ⣽⢏ᒙ࡛ࡏࢇ᩿ࡋ࡚࠸ࡿࡇ࡜ࡀ☜ㄆ࡛ࡁࡓ㸬ᮾ࿴ᕝ໭ᨭὶࡢࡏࢇ᩿ᛂຊࡢపୗࡣ㸪ᙉᗘࡀᙅ࠸ En-a ㉳※࣮࣒ࣟ13)ࡢΰᅾࡀཎᅉ࡜᥎ ࡉࢀࡿ㸬ᮾ࿴ᕝ໭ᨭὶཬࡧᮾ࿴ᕝ༡
ᨭὶࡢヨᩱࡣ㸪ᆶ┤ᛂຊࡣࢮࣟ࡟฿㐩ࡏࡎ㸪ࢩࣗࣝࢡἑࡼ

― 51 ―ࡾ⧞㏉ࡋⲴ㔜࡬ࡢ᢬ᢠຊࡣ
⾲ ヨ㦂࡟⏝࠸ࡓ 7DG ⣽⢏ࡢ≀⌮ⓗᛶ㉁኱ࡁ࠸㸬ᮾ࿴ᕝ໭ᨭὶࡢヨᩱᅵ⢏Ꮚࡢᐦᗘ‵₶ᐦᗘ ஝⇱ᐦᗘྵỈẚࡣ㸪⧞㏉ࡋࡏࢇ᩿᫬࡟࠾࠸࡚
(%)(g/cm3)(g/cm3)(g/cm3)ࡏࢇ᩿ᛂຊࡣ࡯࡜ࢇ࡝ᅇ᚟
2.615
1.033
0.566
82.74
ᮾ࿴ᕝ໭ᨭὶ
ࡋ࡞࠿ࡗࡓ㸬
2.675
0.936
0.490
91.01
ᮾ࿴ᕝ༡ᨭὶ⾲ ࡟ヨ㦂࡟⏝࠸ࡓ Ta-d
2.725
0.964
0.519
85.95
ࢩࣗࣝࢡἑ
⣽⢏ࡢ≀⌮ⓗᛶ㉁ࢆ♧ࡍ㸬࡞࠾㸪ᅵ⢏Ꮚࡢᐦᗘヨ㦂ࡣ⌧ᆅㄪᰝ࡛᥇ྲྀࡋࡓヨᩱ࠿ࡽồࡵࡓ㸬஘ࢀࡢᑡ࡞࠸ヨᩱࡢ஝⇱ᐦᗘࡣ㸪ᮾ࿴ᕝ໭ᨭὶ㸪ᮾ࿴ᕝ༡ᨭὶཬࡧࢩࣗࣝࢡἑ
࡛㠀ᖖ࡟ᑠࡉ࠸್ࢆ♧ࡋ㸪3 ᆅⅬ࡟࠾࠸࡚㢮ఝࡍࡿ≀⌮ⓗᛶ㉁ࢆ♧ࡋࡓ㸬ྵỈẚࡣࡍ࡭࡚ 80%௨ୖ࡛୙㣬࿴≧ែ࡛࠶ࡾ࡞ࡀࡽ㧗ྵỈẚ࡛࠶ࡗࡓ㸬 ⤖ㄽ㸦D㸧 ᮾ࿴ᕝ໭ᨭὶ㛫㝽ẚ㣬࿴ᗘ(%)

3.62459.70

4.459

54.60

4.254

55.06

㸦E㸧 ᮾ࿴ᕝ༡ᨭὶᅗ ࡏࢇ᩿㠃ࡢᵝᏊᮏㄽᩥ࡛ࡣ㸪໭ᾏ㐨⫹᣺ᮾ㒊ᆅ㟈࡟ࡼࡾⓎ⏕ࡋࡓࢸࣇከⓎࡋࡓࢸࣇࣛᒙࡍ࡭ࡾ㸸ᆅᙧⓎ㐩ྐⓗ࡟ࡳࡓᔂቯⓎ⏕ሙࡢ≉ࣛᒙࡍ࡭ࡾࢆᑐ㇟࡟㸪⌧ᆅㄪᰝࢆ⾜࠸㸪␗࡞ࡿሙᡤ࡟࠾ࡅ
ᚩ. ᆅᙧ, Vol.41, pp.147-167, 2020.
ࡿ Ta-d ⣽⢏ࡢ≀⌮ⓗᛶ㉁ཬࡧᐃయ✚⧞㏉ࡋ୍㠃ࡏࢇ᩿≉5㸧
Goto, S., Okada, K.:Monotonic and Cyclic Behaviour of Tephra Layer
ᛶࢆẚ㍑᳨ウࡋࡓ㸬⌧ᆅㄪᰝࡢ㟢㢌ほᐹ࡛ࡣ㸪Ta-d ᒙࡢᒙLandslide at Takanodai from the 2016 Kumamoto Earthquake, WLF
ᗎ࣭ᒙཌࡀሙᡤ࡟ࡼࡗ࡚␗࡞ࡾ㸪≉ᚩⓗ࡞ᒙቃ⏺ࡀ☜ㄆ࡛
2020: Understanding and Reducing Landslide Disaster Risk, vol.4,
ࡁࡓ㸬Ta-d ⣽⢏ࡢ⢏ᗘ≉ᛶཬࡧ≀⌮ⓗᛶ㉁ࡣ␗࡞ࡿሙᡤ࡟
pp.357-364. https://doi.org/10.1007/978-3-030-60706-7_36, 2021࠾࠸࡚㢮ఝࡍࡿ⤖ᯝࢆ♧ࡋࡓ㸬ᮾ࿴ᕝ༡ᨭὶཬࡧࢩࣗࣝࢡ6㸧⥳ᕝ㞝௓㸪ᾏ㔝ᑑᗣ㸪ຍᮧ᫭Ⰻ㸪௝㢌⣖᫂㸪㢼㛫ᇶᶞ㸸2018ἑ࡛᥇ྲྀࡋࡓ Ta-d ⣽⢏ࡣ㸪3 ᅇ┠ࡢ⧞㏉ࡋ࡟ࡼࡾࡏࢇ᩿ᛂᖺ໭ᾏ㐨⫹᣺ᮾ㒊ᆅ㟈࡛⿕ᐖࢆཷࡅࡓⅆᒣ⅊㉁ᅵࡢ≀⌮≉ᛶຊࡢపୗࢆ♧ࡋ㸪ᮾ࿴ᕝ໭ᨭὶࡣ⧞㏉ࡋࡏࢇ᩿᫬࡟࠾࠸࡚㸪࠾ࡼࡧຊᏛ≉ᛶ㸪ᅵᮌᏛ఍ㄽᩥ㞟A1㸦ᵓ㐀࣭ᆅ㟈ᕤᏛ㸧㸪
Vol.76㸪
ࡏࢇ᩿ᛂຊࡣ࡯࡜ࢇ࡝ᅇ᚟ࡋ࡞࠿ࡗࡓࡀ㸪ࢫࢺࣞࢫࣃࢫࡣ
No.4㸦ᆅ㟈ᕤᏛㄽᩥ㞟➨ 39 ᕳ㸧㸪I_741-I_754㸪2020.
㸱ࡘࡢ⤒㊰ࡀ㒊ศⓗ࡟㔜࡞ࡿ⤖ᯝࢆ♧ࡋࡓ㸬
7㸧Ⲩ∾᠇㝯㸪Ύᯇ₶୍㸪ᒸᯘᕦ㸪⸨஭἞㞝㸸ⅆᒣ⅊⢒⢏ᅵࡢ≀Ta-d ⢒⢏ࡣ㢼໬≧ែࢆྵࡵ࡚ᒙ┦ࡣከᵝ࡛࠶ࡿࡀࠊ᭱ୗ
⌮ヨ㦂 ᐃ್ࡢࡤࡽࡘࡁ࡟ཬࡰࡍᙳ㡪ᅉᏊࡢ᳨ウ㸪ᆅ┙ᕤᏛࢪ㒊ࡢ Ta-d ⣽⢏࡟ࡘ࠸࡚ࡣ⫹᣺ᮾ㒊ᆅ㟈࡛Ⓨ⏕ࡋࡓከᵝ࡞࣮ࣕࢼࣝ㸪Vol.9㸪No.3㸪pp.359-373㸪2014.
ᔂቯࢆ᳨ウࡍࡿ㝿࡟㔜せ࡛࠶ࡾ㸪En-a ࣮࣒ࣟࡶྵࡵ࡚௒ᚋ
8㸧 Li R., Wang F., Zhang S.㸸Controlling role of Ta-d pumice on theࡍ࡭ࡾ㠃ࡢⓎ⏕ࡋࡸࡍࡉࡸ⛣ື㏿ᗘ➼࡟ࡘ࠸࡚ࡢ᳨ウࢆ
coseismic landslides triggered by 2018 Hokkaido Eastern Iburi
⾜࡞ࡗ࡚࠸ࡃᚲせࡀ࠶ࡿ㸬
Earthquake, Landslides,ㅰ㎡㸸ᮏ◊✲ࡢ୍㒊ࡣ㸪㸦୍㈈㸧◁㜵࣭ᆅࡍ࡭ࡾ◊✲ࢭࣥࢱ࣮௧࿴ 3 ᖺᗘ◊✲㛤Ⓨຓᡂཬࡧ㸪᪂₲኱Ꮫ⅏ᐖ࣭᚟⯆⛉Ꮫ◊✲ᡤඹྠ◊✲㈝㸦2021-1㸧ࡢຓᡂ࡟ࡼࡗ࡚⾜ࢃࢀࡓ㸬ࡲࡓ㸪⌧ᆅㄪᰝཬࡧᐊෆᐇ㦂࡟ࡘ࠸࡚ࡣᒣ᲍኱Ꮫᆅ┙ᕤᏛ◊✲ᐊࡢᏛ⏕ࡼࡾ༠ຊࢆᚓࡓ㸬㛵ಀྛ఩࡟ឤㅰࡋࡲࡍ㸬https://doi.org/10.1007/s10346-020-01349-y, 2020.
9㸧 ⋤ຌ㍤, ྂ㇂ඖ, Ώ㎶┤႐, ᅵ஭୍⏕, 㤿ᑀ㸸ᖹᡂ 30 ᖺ໭ᾏ㐨⫹᣺ᮾ㒊ᆅ㟈࡟ࡼࡿᅵ◁⅏ᐖࡢ≉ᚩ, ி㒔኱Ꮫ㜵⅏◊✲ᡤᖺሗ, ➨ 62 ྕ A, pp.48-56, 2019.
10㸧 ᅜᅵᆅ⌮㝔㸸ᖹᡂ 30 ᖺ㸦2018 ᖺ㸧໭ᾏ㐨⫹᣺ᮾ㒊ᆅ㟈࡟㛵ࡍࡿ᝟ሗ<https://www.gsi.go.jp/BOUSAI/H30-hokkaidoiburi-east-ཧ⪃ᩥ⊩

earthquake-index.html> (2022/04/30 ࢔ࢡࢭࢫ).

1㸧 㛗㇂ᕝ೺㸪ⰼᒸṇග㸪ྂᕝ❳ኴ㸪㔜㔝⪷அ㸪୐ᒣኴ㸪୰ᕝගᘯ㸪Ᏻ⸨ᑑ⏨㸸໭ᾏ㐨ᮾ㒊㸪㔲㊰ᆅᇦ࡟࠾ࡅࡿᶡ๓ d 㝆ୗⅆ○11) ྂᕝ❳ኴ㸪୰ᕝගᘯ㸸ᶡ๓ⅆᒣᆅ㉁ᅗ㸪ⅆᒣᆅ㉁ 15㸪⏘ᴗᢏ⾡⥲ྜ◊✲ᡤᆅ㉁ㄪᰝ⥲ྜࢭࣥࢱ࣮㸪2010㸬

ሁ✚≀ࡢⓎぢ࡜ࡑࡢព⩏㸪ᆅ㉁Ꮫ㞧ㄅ㸪➨ 119 ᕳ㸪➨ 7 ྕ㸪12) ኱ᕝཎඃᕼ, ᚋ⸨⪽, ᒸ⏣೺ᮭ(2021): 2018 ᖺ໭ᾏ㐨⫹᣺ᮾ

pp.446-456㸪2013㸬㒊ᆅ㟈࡟࠾ࡅࡿཌ┿⏫࡟ศᕸࡍࡿTa-d ᒙࡢᐃయ✚⧞㏉ࡋ୍㠃

2㸧 ᱵὠㆡ㸸ᜨᗞ a 㝆ୗ㍍▼ཬࡧᶡ๓ d 㝆ୗ㍍▼ࡢᖺ௦࡟㛵ࡍࡿࡏࢇ᩿≉ᛶ, ➨ 60 ᅇ᪥ᮏᆅࡍ࡭ࡾᏛ఍◊✲Ⓨ⾲఍ㅮ₇㞟, P-6,㈨ᩱ㸪ᮾ໭ᆅ⌮㸪➨ 39 ᕳ㸪➨ 2 ྕ㸪ppt.141-143㸪1987.

pp. 130-131.

3㸧 ຾஭⩏㞝㸸ᨭ➖㝆ୗ㍍▼ሁ✚≀࡟ࡘ࠸࡚㸪≉࡟ᨭ➖࢝ࣝࢹࣛᙧᡂ┤๓ࡢάື࡟ࡘ࠸࡚㸪ⅆᒣ㸪➨ 2 㞟㸪➨ 4 ᕳ㸪➨ 1 ྕ㸪13) ᒸ⏣೺ᮭ࣭ᚋ⸨⪽(2021): ཌ┿⏫ᮾ࿴ᆅ༊࡟ศᕸࡍࡿ㝆ୗⅆ○ሁ✚≀ࡢᐃయ✚⧞㏉ࡋ୍㠃ࡏࢇ᩿≉ᛶ -ᣊ᮰ᅽ౫Ꮡᛶ࡟㛵

pp.33-48㸪1959.

ࡍࡿ⪃ᐹ-, ➨ 56 ᅇᆅ┙ᕤᏛ◊✲Ⓨ⾲఍, 13-4-5-07.          4㸧 ▼୸⪽, ᘅ℩ர, ᕝୖ※ኴ㑻, ㍿Ỉ೺୍, ᑠᏳᾈ⌮, ຍ℩ၿὒ, 㧗ᶫⰋ, ༓ᮌⰋ㞞ᘯ, ⏣㏆῟㸸2018 ᖺ໭ᾏ 㐨⫹᣺ᮾ㒊ᆅ㟈࡟ࡼࡾ  ― 52 ―㸦 ཷ௜㸧