平成23年台風12号による熊野那智大社裏山における大規模斜面崩壊の解析条件設定に関する研究

Ṕྐ㒔ᕷ㜵⅏ㄽᩥ㞟 Vol. 7㸦2013ᖺ7᭶㸧 ࠙ㄽᩥࠚ

ᖹᡂ23ᖺྎ㢼12ྕ࡟ࡼࡿ⇃㔝㑣ᬛ኱♫⿬ᒣ࡟࠾ࡅࡿ

኱つᶍᩳ㠃ᔂቯࡢゎᯒ᮲௳タᐃ࡟㛵ࡍࡿ◊✲

Analysis method of the large landslide occurred behind the Kumano Nachi-Taisha shrine

triggered by Tayphoon Talas

⸨ᮏᑗග

1

࣭▼⏣ඃᏊ

2

࣭ᱵᮏၨ௓

3

࣭ᑠᮡ㈼୍ᮁ

4

࣭㔛῝ዲᩥ

5

࣭῝ᕝⰋ୍

5

Masamitsu Fujimoto, Yuko Ishida, Keisuke Umemoto, Ken’ichirou Kosugi, Yoshifumi Satofuka,

and Ryoichi Fukagawa

1_{❧࿨㤋኱Ꮫຓᩍ ⌮ᕤᏛ㒊㒔ᕷࢩࢫࢸ࣒ᕤᏛ⛉㸦ࠛ525-8577 ⁠㈡┴ⲡὠᕷ㔝㊰ᮾ1-1-1㸧} Assistant Professor, Ritsumeikan University, Dept. of Civil Engineering

2_{❧࿨㤋኱Ꮫ◊✲ဨ ⥲ྜ⛉Ꮫᢏ⾡◊✲ᶵᵓ㸦ࠛ525-8577 ⁠㈡┴ⲡὠᕷ㔝㊰ᮾ 1-1-1㸧} Reseacher, Ritsumeikan University, Research Organization of Science and Engineering

3_{ዉⰋ┴ᗇ㸦ࠛ630-8213 ዉⰋ┴ዉⰋᕷⓏ኱㊰⏫30㸧} Nara Prefectural Government

4

ி㒔኱Ꮫ෸ᩍᤵ ኱Ꮫ㝔㎰Ꮫ◊✲⛉, CREST JST㸦606-8502 ி㒔ᕷᕥி༊໭ⓑᕝ㏣ศ⏫㸧 Associate Professor, Kyoto University, Graduate of Agriculture, CREST JST

5_{❧࿨㤋኱Ꮫᩍᤵ ⌮ᕤᏛ㒊㒔ᕷࢩࢫࢸ࣒ᕤᏛ⛉㸦ࠛ525-8577 ⁠㈡┴ⲡὠᕷ㔝㊰ᮾ1-1-1㸧} Professor, Ritsumeikan University, Dept. of Civil Engineering

The Tayphoon Talas in Septenber 2012 caused the landslide and debris flow behind the Kumano Nachi-Taisha shrine. The total amount and peak of rainfall by Typoon Talas were 707 mm and 93 mm/hr, respectively. A large landslide occurred at the peak rainfall sround 3 pm September 4 and hit the building of shrine as debris flow. Based on the filed investigation and topographical analysis, the landslide with about 30 m wide, 50 m long, 15m depth was collapsed at the peak of rainfall event. Our results indicated that the large landslide was simulated by considering the deep weathered bedrock conditions.

Keywords : Kumano Nachi-Taisha shrine,landslide, rain infiltration, slope stability,weathered bedrock

㸯㸬ࡣࡌࡵ࡟ ᖹᡂ 23 ᖺྎ㢼 12 ྕ࡟ࡼࡗ࡚༡⣖ᆅ᪉࡟ࡶࡓࡽࡉࢀࡓ㇦㞵ࡣᗈ⠊ᅖ ࡛ᔂቯ࣭ᅵ▼ὶࡸ኱つᶍ῝ᒙᔂቯࠊࡲࡓࠊኳ↛ࢲ࣒ࡢᙧᡂࢆᘬࡁ㉳ࡇ ࡋࡓࠋ⤖ᯝ࡜ࡋ࡚༡⣖ᆅ᪉࡛ࡣከࡃࡢṚ⪅࣭⾜᪉୙᫂⪅ࢆฟࡍ⏒኱࡞ ⿕ᐖ࡟ࡳࡲࢃࢀࡓࠋ࿴ḷᒣ┴㑣ᬛ຾ᾆ⏫㑣ᬛᕝὶᇦ࡛ࡣ୺࡟ᅵ▼ὶ࡟ ࡼࡿ⿕ᐖࡀ኱ࡁ࠿ࡗࡓࡀࠊ㔠ᒣ㇂ᕝ※㢌㒊࡛ࡣ኱つᶍ࡞ᩳ㠃ᔂቯࡀⓎ ⏕ࡋࡓࡼ࠺࡟ࠊᅵ▼ὶ※ὶ㒊࡛ࡣ῝ᒙᔂቯ࡟ࡣ⮳ࡽ࡞࠸ࡲ࡛ࡶẚ㍑ⓗ ኱つᶍ࡞ᩳ㠃ᔂቯࡢⓎ⏕ࡀሗ࿌ࡉࢀ࡚࠸ࡿ1㸧_{ࠋୡ⏺㑇⏘࡛࠶ࡿ㑣ᬛ኱} ෗┿ 1 㑣ᬛ኱♫ࡢ⿕⅏≧ἣ 㸦㑣ᬛ኱♫ᥦ౪㸧

2011/9/1 2011/9/2 2011/9/3 2011/9/4 2011/9/5 R a in fa ll (m m /h ) 0 20 40 60 80 100 C u m u lati ve r a infall (m m ) 0 200 400 600 800 Rainfall Cumulative rainfall ♫ࢆくࡗࡓᅵ▼ὶ㸦෗┿ 1㸧ࡢ※ὶ㒊࡟࠾࠸࡚ࡶᔂቯ῝ 10m ࢆ㉺࠼ࡿ኱つᶍᩳ㠃ᔂቯࡢⓎ⏕ࡀ☜ㄆࡉࢀࡓࠋ ࡇࢀࡲ࡛ࡢᩳ㠃ᔂቯࡢ◊✲ࡢከࡃࡣ୺࡜ࡋ࡚ᔂቯ῝ࡀ᭱኱ 2㹼3m ⛬ᗘࡲ࡛ࡢ⾲ᒙᔂቯࢆᑐ㇟࡜ࡋ࡚⾜ࢃࢀ ࡚ࡁࡓࠋࡑࡢࡓࡵࠊ῝ᒙᔂቯࢆྵࡴ኱つᶍᩳ㠃ᔂቯࢆᑐ㇟࡜ࡋࡓ◊✲ 2㸧_{ࡣᑡ࡞࠸࡜࠸࠼ࡿࠋ⾲ᒙᔂቯࡢⓎ} ⏕ࡣ⾲ᒙᅵᒙࡢᔂቯ⌧㇟࡜ࡋ࡚ᤊ࠼ࡿࡇ࡜ࡀ࡛ࡁࡿࡀࠊ኱つᶍᩳ㠃ᔂቯࡣᅵᒙ௨῝ࡢ㢼໬ᇶᒾᒙࢆྵࡵࡓᔂ ቯ⌧㇟࡜ࡋ࡚ྲྀࡾᢅ࠺ᚲせࡀ࠶ࡿࠋࡋ࠿ࡋࠊࡇࢀࡲ࡛ࡢ◊✲࡛ࡣ㝆㞵ᾐ㏱ゎᯒ࣭Ᏻᐃゎᯒ࡟࠾࠸࡚㢼໬ᇶᒾ ᒙࢆゎᯒᑐ㇟࡜ࡋ࡚࠾ࡽࡎࠊゎᯒ᮲௳ࡢタᐃ࡟㛵ࡋ࡚༑ศ࡞▱ぢࡣᚓࡽࢀ࡚࠸࡞࠸ࠋࡑࡇ࡛ᮏ◊✲࡛ࡣ㑣ᬛ ኱♫⿬ᒣࡢ኱つᶍᩳ㠃ᔂቯ࡟࠾ࡅࡿゎᯒ᮲௳ࡢタᐃ࡟㛵ࡋ࡚ࠊ⌧ᆅㄪᰝࠊᔂቯ๓ᚋࡢ DEM㸦ᩘ್ᶆ㧗ࣔࢹ ࣝ㸧࠾ࡼࡧᅵᒙࡢࡳ࡞ࡽࡎ㢼໬ᇶᒾᒙࢆᑐ㇟࡜ࡋࡓ㝆㞵ᾐ㏱ゎᯒ࣭Ᏻᐃゎᯒࢆ⾜࠺ࡇ࡜࡟ࡼࡗ᳨࡚ウࡍࡿࡇ ࡜ࢆ┠ⓗ࡜ࡋࡓࠋ 㸰㸬ᩳ㠃ᔂቯࡢᐇែ 㸦1㸧 㝆㞵≉ᛶ 㑣ᬛᕝὶᇦ࡛ࡣ 9 ᭶ 4 ᪥ᮍ᫂࡟」ᩘࡢᨭᕝ ࡛ᅵ▼ὶࡀⓎ⏕ࡋࠊ⿕ᐖࡀ⏕ࡌ࡚࠸ࡿ 1㸧_ࠋ ⇃㔝㑣ᬛ኱♫࡛グ㘓ࡉࢀࡓ㞵㔞ࢹ࣮ࢱ࡛ࡣ 9 ᭶ 4 ᪥༗๓ 2 ᫬࡟᫬㛫㞵㔞 82 ੈࠊ༗๓ 3 ᫬ ࡟ྠ 93 ੈࡢ㠀ᖖ࡟㝆㞵ᙉᗘࡢ኱ࡁ࠸㞵ࡀほ  ࡉࢀࡓ㸦ᅗ 1㸧ࠋࡲࡓࠊ㝆㞵ࣆ࣮ࢡࡲ࡛ࡢ ✚⟬㞵㔞ࡣ 578 ੈࠊ⥲㝆Ỉ㔞ࡣ 707 ੈ࡛࠶ࡗ ࡓࠋ࡞࠾ࠊ㑣ᬛ኱♫࡟タ⨨ࡉࢀࡓ㞵㔞ィࡣྂ ࠿ࡗࡓࡓࡵࠊ㞵㔞ࡀᐇ㝿ࡼࡾ㐣ᑠホ౯ࡉࢀ࡚ ࠸ࡿྍ⬟ᛶࡀ࠶ࡿࠋ㑣ᬛ኱♫ࡢ⫋ဨ࡟ᑐࡍࡿࣄ࢔ࣜࣥࢢ࠿ࡽ 9 ᭶ 4 ᪥༗๓ 2 ᫬༙ࡈࢁ࡟㞾㞵࡟ࡼࡿ೵㟁ࠊ༗ ๓ 3 ᫬ࡈࢁ࡟⿕⅏ࡋࡓ኱♫ቃෆ࡬ࡢἾỈࡢỏ℃ࡀ☜ㄆࡉࢀ࡚࠾ࡾࠊᅵ▼ὶࡢⓎ⏕᫬้ࡣ 9 ᭶ 4 ᪥༗๓ 3 ᫬㐣 ࡂ࡜᥎ᐃࡉࢀࡿࠋ 㸦2㸧 ᩳ㠃ᔂቯࡢᙧ≧࠾ࡼࡧつᶍ ᔂቯⓎ⏕๓ᚋࡢᆅᙧᅗ࠾ࡼࡧᔂቯᚋࡢ࢜ࣝࢯ⏬ീࢆᅗ 2 ࡟♧ࡍࠋᔂቯ๓ࡢᆅᙧᅗࡣᅜᅵᆅ⌮㝔ࡢ 10m ࣓ ࢵࢩࣗࡢᩘ್ᶆ㧗ࢹ࣮ࢱࠊᔂቯᚋࡢᆅᙧᅗࡣᅜᅵ஺㏻┬㏆␥ᆅ᪉ᩚഛᒁࡢ 1m ࣓ࢵࢩࣗ LP ࢹ࣮ࢱࢆᇶ࡟స ᡂࡋࡓࠋᔂቯ๓ᚋࡢᆅᙧࢹ࣮ࢱࡣ࣓ࢵࢩࣗࢧ࢖ࢬࠊ ᐃ᪉ἲࡀ␗࡞ࡿࡓࡵࠊྠ୍ᆅⅬ࡛ࡶᶆ㧗ᕪࡀぢࡽࢀࠊ ࢹ࣮ࢱࡢྲྀࡾᢅ࠸ࡀ㞴ࡋ࠸ሙྜࡀ࠶ࡿࠋࡋ࠿ࡋࠊᮏ◊✲࡛ࡣᔂቯᆅୖ㒊࡟࠾ࡅࡿ㠀ᔂቯᆅࡢᶆ㧗ࡀᔂቯ๓ᚋ ࡛ᕪࡀぢࡽࢀ࡞࠿ࡗࡓࡇ࡜࡜ᔂቯᆅࡢᶆ㧗ࡢపୗࡀ㢧ⴭ࡛࠶ࡗࡓࡓࡵࠊ༢⣧࡞ẚ㍑࠿ࡽᔂቯᙧ≧࡟ࡘ࠸࡚ゎ ᯒࢆ⾜ࡗࡓࠋᔂቯࡣ 2 ࡘࡢᑠࡉ࡞㇂࡟ᣳࡲࢀࡓᛴᓧ࡞ᑿ᰿㒊࡛Ⓨ⏕ࡋ㸦ᅗ 2b㸧ࠊᖜ⣙ 30mࠊ㛗ࡉ 50m ⛬ᗘ ࡢ኱ࡁࡉࡔࡗࡓ࡜⪃࠼ࡽࢀࡿ㸦ᅗ 2c㸧ࠋᅗ 3 ࡟ᔂቯࡢ୰ᚰ㒊࡟ἢࡗࡓ⦪᩿⥺ࡢᔂቯ๓ᚋࡢ᩿㠃ᅗࢆ♧ࡍࠋ ᔂቯࡢ୺せ㒊ࡣ኱ࡁࡃᶆ㧗ࢆపୗࡉࡏࠊ᭱኱࡛῝ࡉ 12m ⛬ᗘᶆ㧗ࡀపୗࡋࡓࠋ⁥ⴠᓴࡣୖὶ㒊ࡢᑿ᰿࠿ࡽ Ỉᖹ㊥㞳 20m ୗὶ࡟Ꮡᅾࡋࠊ㧗ࡉࡣ⣙ 15m ࡛࠶ࡗࡓࠋ⁥ⴠᓴ࡛ࡣ㢼໬ࡋࡓⰼᓵᩬᒾࡀ㟢ฟࡋࠊ᫂░࡞⠇⌮ ࡢⓎ㐩ࡀほᐹࡉࢀࡓࠋ⌧ᆅㄪᰝ࠾ࡼࡧ࢜ࣝࢯ⏬ീ㸦ᅗ 2a㸧࠿ࡽࠊ⁥ⴠᓴࡼࡾୗὶ࡛ࡣ኱つᶍᔂቯ࡟ࡼࡿᅵ ◁࠾ࡼࡧಽᮌࡢᔂ✚ࡀ☜ㄆࡉࢀࡓࡓࡵࠊᐇ㝿ࡢᔂቯ῝ࡣ 12m ࡼࡾ῝࠸࡜᥎ᐹࡉࢀࡿࠋࡑࡢࡓࡵࠊᐇ㝿ࡢᔂ ቯࡢࡍ࡭ࡾ㠃ࡣᅗ 4 ୰ࡢ◚⥺ࡢࡼ࠺࡟᥎ᐃࡉࢀࡿࠋࡲࡓࠊ୺せᔂቯ㒊ᮎ➃࠾ࡼࡧୗὶᇦ࡛ࡣᔂቯ๓ᚋ࡛᫂░ ࡞ᶆ㧗ᕪࡣㄆࡵࡽࢀ࡞࠿ࡗࡓࠋ⌧ᆅㄪᰝ⤖ᯝࢆ⪃៖ࡍࡿ࡜ࠊᐇ㝿࡟ࡣᔂቯ࣭ᅵ▼ὶ໬࡟ࡼࡗ࡚ᩳ㠃ୖ㒊࠿ࡽ ὶୗࡋࡓᅵ◁࡟ࡼࡗ࡚ᾐ㣗ࡀⓎ⏕ࡋࡓࡀࠊࡑࡢᚋࡢὶୗࡋࡓᅵ◁ࡢሁ✚࡟ࡼࡗ࡚ᔂቯ๓ᚋࡢᶆ㧗ᕪ࡟ᕪࡀࡳ ࡽࢀ࡞࠿ࡗࡓ࡜⪃࠼ࡽࢀࡿࠋ㑣ᬛ኱♫⿬ᒣࡢ※㢌㒊࡛ࡢ኱つᶍᔂቯࡣ⣙㛗ࡉ 50mࠊᖜ 30mࠊ῝ࡉ 15m ⛬ᗘ ࡢつᶍ࡛࠶ࡗࡓ࡜᥎ᐃࡉࢀࡓࠋ ᅗ 1 㑣ᬛ኱♫࡟࠾ࡅࡿ㞵㔞

m (a) (c)(b) ᅗ 2 ᔂቯᩳ㠃ࡢ≉ᚩ㸸㸦a㸧ᔂቯᚋࡢ࢜ࣝࢯ⏬ീ㸪㸦b㸧ᔂቯ๓ࡢᆅᙧᅗ㸪㸦c㸧ᔂቯᚋࡢᆅᙧᅗ 㸦ᆅᙧᅗࡢ➼㧗⥺ࡣ 2m 㛫㝸㸧 Horizontal distance (m) 0 50 100 150 200 250 300 Altitude ( m ) 580 600 620 640 660 680 700 720

Before the landslie After the landslide

ᅗ 3 ᔂቯᆅࡢ᩿㠃ᅗ㸦ᅗ 2A㸫A’᩿㠃㸧 ᅗ 4 ᔂቯᆅࡢ᩿㠃ᅗ࠾ࡼࡧ᥎ᐃࡍ࡭ࡾ㠃 Horizontal distance (m) 0 20 40 60 80 100 120 Altitude ( m ) 640 660 680 700 720

Before the landslie After the landslide

᥎ᐃ䛩䜉䜚㠃

Pore water pressure (cmH2O) -600 -500 -400 -300 -200 -100 0 Volum etric w a ter c ontent ( m 3 /m 3 ) 0.2 0.3 0.4 0.5 0.6 0.7 _{Layer 1} Layer 2 Layer 3 ᅗ 5 ᅵተࢧࣥࣉࣝࡢỈศ≉ᛶ᭤⥺ 㸦3㸧 ᔂቯᆅࡢᅵተ≉ᛶ ⁥ⴠᓴୖ㒊ࡢ㠀ᔂቯᆅ 5 ᆅⅬ㸦ᅗ 2c ࡢ㉥Ⅼ㸧࡟࠾ ࠸࡚⡆᫆ືⓗࢥ࣮ࣥ㈏ධヨ㦂ヨ㦂ࢆ⾜࠸ࠊᅵᒙࡢཌࡉ ࢆㄪᰝࡋࡓࠋᅵᒙ῝ࡣࠊ0.5mࠊ 0.9mࠊ 1.7mࠊ 1.8mࠊ 3.3m ࡛࠶ࡗࡓࠋ໭す᪉ྥ࡯࡝ᅵᒙ῝ࡀⷧࡃ࡞ࡿഴྥ ࢆ♧ࡋࡓࠋࡲࡓࠊ㟢㢌㠃ࡢᅵᒙࡣᆅ⾲㠃࡟㏆࠸࡯࡝⢓ ᅵ໬ࡋ࡚࠾ࡾࠊ㖄┤ୗ᪉࡯࡝⢏ᚄࡢ኱ࡁ࠸⢏Ꮚࡢ๭ ྜࡀቑ࠼ࠊᇶᒾࡢ㢼໬ࡢ㐍⾜ࡀㄆࡵࡽࢀࡓࠋ㢼໬ᇶ ᒾ࡜ᅵᒙࡢቃ⏺ࡣ୙᫂░࡛࠶ࡾࠊ₞⛣ⓗ࡟⢏ᗘࠊᙉᗘ ࡀኚ໬ࡋ࡚࠸ࡓࠋᅵᒙࡢ㖄┤᪉ྥࡢỈ⌮≉ᛶࡢᕪࢆぢ ࡿࡓࡵ࡟ࠊᅵተࢧࣥࣉࣝࡣ㟢㢌㠃ࡢᅵᒙࢆ㖄┤᪉ྥ 3 ᒙ㸦ୖᒙ 1 ᒙࠊ୰ᒙ 2 ᒙࠊୗᒙ 3 ᒙ㸧࡟ศࡅ࡚᥇ྲྀࡋ ࡓࠋ᥇ྲྀࡋࡓࢧࣥࣉࣝࢆᐇ㦂ᐊ࡟ᣢࡕᖐࡗ࡚ࠊኚỈ఩ ㏱Ỉヨ㦂࡟ࡼࡗ࡚㣬࿴㏱ỈಀᩘK_sࢆィ ࡋࡓࠋࡑࡢ⤖ᯝࠊ⾲ᒙ㸸K_s= 4.0u10-6 cm/sࠊ୰ᒙ㸸K_s= 1.8u10-6 cm/sࠊୗᒙ㸸K_s= 7.7u10-6 cm/s ࡛࠶ࡾࠊ㖄┤᪉ྥ࡟኱ࡁ࡞ᕪࡣぢࡽࢀ࡞࠿ࡗࡓࠋࡲࡓࠊ୍⯡ⓗ࡞᳃ᯘᅵተ ࡟ẚ࡭࡚ẚ㍑ⓗప࠸㏱Ỉಀᩘࢆ♧ࡋࡓࠋࡲࡓࠊpF ヨ㦂ࢆᐇ᪋ࡋࠊಖỈᛶࢆィ ࡋࡓࠋࡑࡢ⤖ᯝࠊୖᒙ࠿ࡽ ୗᒙ࡟ྥࡅ࡚ಖỈᛶࡀపୗࡍࡿഴྥࢆ♧ࡋࡓ㸦ᅗ 5㸧ࠋ 㸱㸬ᔂቯⓎ⏕࡟㛵ࡍࡿ㝆㞵ᾐ㏱࣭ᩳ㠃Ᏻᐃゎᯒ

⾲ 1 ᾐ㏱࣭Ᏻᐃゎᯒ࡟⏝࠸ࡓࣃ࣓࣮ࣛࢱ 㸦1㸧 ゎᯒ᪉ἲ ᮏ◊✲࡛ࡣ᭷㝈せ⣲ἲ࡟ࡼࡿ㞵Ỉὶືࡢᩘ್ࢩ࣑࣮ࣗࣞࢩࣙࣥ3㸧_{ࢆ⾜ࡗࡓࠋࡇࡢ᪉ἲ࡛ࡣࠊ㞵Ỉὶືࡢᩘ} ್ࢩ࣑࣮ࣗࣞࢩࣙࣥ࡟ࡼࡗ࡚ࠊὶᇦෆࡢྛⅬ࡟࠾ࡅࡿᅽຊỈ㢌㸦㛫㝽Ỉᅽ㸧

\

[cm]࡜య✚ྵỈ⋡

T

[cm3/cm3]ࡢ㖄┤ศᕸࡀィ⟬ࡉࢀࡿࠋᩘ್ࢩ࣑࣮ࣗࣞࢩࣙࣥ࡟࠾ࡅࡿᅵተࡢಖỈᛶ㸦

T

࡜

\

ࡢ㛵ಀ㸧࡜㏱Ỉ ᛶ㸦K ࡢ

\

ࡢ㛵ಀ㸧ࡣࠊࡑࢀࡒࢀḟᘧ࡛⾲⌧ࡉࢀࡿ4㸧_ࠋ 㸦1㸧 㸦2㸧 ࡇࡇ࡛ࠊ

_S

_e㸸᭷ຠ㣬࿴ᗘࠊ

T

_s㸸㣬࿴య✚ྵỈ⋡ [cm3 /cm3]ࠊ

T

_r㸸ṧ␃య✚ྵỈ⋡ [cm3 /cm3]ࠊ

\

_m㸸࣓ࢪ࢔ ࣥᏍ㝽ᚄ࡟ᑐᛂࡍࡿᅽຊỈ㢌 [cm]ࠊ

V

㸸Ꮝ㝽ᚄศᕸࢆ⾲ࢃࡍ↓ḟඖࣃ࣓࣮ࣛࢱࠊ_Ks㸸ᅵᒙࡢ㣬࿴㏱Ỉಀ ᩘ [cm/sec]ࠊ_Q㸸వṇつศᕸ㛵ᩘ࡛࠶ࡿࠋ ᾐ㏱ィ⟬⤖ᯝ࡟ᑐࡋ࡚ 2 ḟඖ⡆᫆ Bishop ἲࢆ⏝࠸ࡿࡇ࡜࡛Ᏻ඲⋡ࢆィ⟬ࡍࡿࠋ2 ḟඖ⡆᫆ Bishop ἲ࡛ࡣࠊ ෇ᘼ≧ࡢࡍ࡭ࡾ㠃ࢆ௬ᐃࡋࡓୖ࡛ࠊࡍ࡭ࡾᅵሢࢆ㖄┤᪉ྥࡢ⥺ศ࡟ࡼࡗ࡚ᗄࡘ࠿ࡢࢫࣛ࢖ࢫ࡟ศ๭ࡋࠊྛࢫ ࣛ࢖ࢫࡢࡏࢇ᩿ຊ࡜ࡏࢇ᩿᢬ᢠຊࢆྜ⟬ࡋ࡚෇ᘼ඲యࡢᏳ඲⋡ࢆồࡵࡿࠋࡲࡓࠊᮏ◊✲࡛ࡣࡍ࡭ࡾ㠃ᙧ≧ࢆ ௬ᐃࡏࡎࠊ᭱ࡶᏳ඲⋡ࡀᑠࡉࡃ࡞ࡿࡍ࡭ࡾ㠃ᙧ≧ࢆ᥈⣴ࡋࠊỴᐃࡍࡿ᪉ἲࢆ⏝࠸ࡓࠋḟᘧ࡟ Bishop ἲ࡟ࡼ ࡿᏳ඲⋡㸦

_F

_s㸧ࡢ⟬ฟᘧࢆ♧ࡍࠋ 㸦3㸧                        ࡇࡇ࡛ࠊࢫࣛ࢖ࢫ㹧࡟ᑐࡋ࡚ࠊ

_u

_i㸸ṇࡢ㛫㝽Ỉᅽ㸦N/cm2_㸧ࠊ i

W

㸸㔜㔞㸦N㸧ࠊ

_b

_i㸸Ỉᖹᖜ㸦cm㸧ࠊ i

D

㸸ࡍ࡭ࡾ㠃ゅᗘ㸧ࠊ

I

_i㸸ෆ㒊ᦶ᧿ゅ㸦°㸧ࠊ

_c

_i㸸⢓╔ຊ㸦N/cm2_{㸧࡛࠶ࡿࠋᘧ㸦3㸧ࡢྑ㎶࡟ࡶࠊ} s

F

ࡀྵ ࡲࢀࡿࡓࡵࠊ

_F

_sࡣ⧞ࡾ㏉ࡋィ⟬࡟ࡼࡗ࡚ồࡵࡽࢀࡿࠋ 㸦2㸧 ゎᯒ᮲௳ ᑐ㇟᩿㠃ࡣỈᖹ㊥㞳 113mࠊ῝ࡉ 15.1m ࡜ࡋࡓࠋ⾲ᒙᅵࢆ 1.6m(⾲ᒙᅵ 0.1mࠊୗᒙᅵ 1.5m)࡜ࡋࠊࡑࡢୗ࡟ 13.5mࡢ㢼໬ᇶᒾᒙࢆタᐃࡋࡓࠋ⾲ᒙᅵ 0.1m ࡣ᳃ᯘᅵተ A ᒙ࡟┦ᙜࡍࡿࠋࡲࡓࠊᑐ㇟᩿㠃ࢆỈᖹ᪉ྥ࡟➼ 㛫㝸 2mࠊ㖄┤᪉ྥ࡟⾲ᒙᅵ 0.1mࠊୗᒙᅵࠊ㢼໬ᇶᒾ 0.5m ࠿ࡽ࡞ࡿィ⟬せ⣲࡟ศ๭ࡋࡓࠋᅵᒙࠊ㢼໬ᇶᒾ ࡢಖỈᛶࡣ⌧ᆅㄪᰝࡢ⤖ᯝ࠿ࡽỴᐃࡋࡓࠋୗᒙᅵ࡟┦ᙜࡍࡿ⌧ᆅᅵተࢧࣥࣉࣝ࠿ࡽᚓࡽࢀࡓ㏱Ỉಀᩘࡣ㠀ᖖ ࡟ᑠࡉ࠿ࡗࡓࡀࠊᐇ㝿ࡢᩳ㠃࡛ࡣட⿣ࡸࣃ࢖ࣉὶࢆྵࡴ⣲᪩࠸ᾐ㏱ὶࢆᣢࡘ㑅ᢥⓗὶฟ⤒㊰ࢆ⪃៖ࡍࡿᚲせ ࡀ࠶ࡿ࡜⪃࠼ࡽࢀࡿࠋᑠᆺ࡜኱ᆺࢧࣥࣉࣝࢆ⏝࠸࡚㏱Ỉಀᩘࢆẚ㍑ࡋࡓ᪤ ◊✲5㸧_{࡛ࡣࠊᑠᆺࢧࣥࣉࣝ࡟ẚ} ࡭࡚኱ᆺࢧࣥࣉࣝࡢ㏱Ỉಀᩘࡣ 2 ࣮࢜ࢲ࣮኱ࡁ࠸ࡇ࡜ࡀሗ࿌ࡉࢀ࡚࠸ࡿࠋᮏ◊✲࡛ࡣࠊ᪤ ◊✲ࢆཧ⪃࡜ࡋ ࡚ࠊୗᒙᅵࡢ㏱Ỉಀᩘࢆᐇ㦂⤖ᯝ࡛ᚓࡽࢀࡓ್ࡼࡾ 2 ࣮࢜ࢲ࣮⛬ᗘ኱ࡁ࠸್࡟タᐃࡋࡓࠋ⾲ᒙᅵ㸦A ᒙ㸧ࡣ ୗᒙᅵ࡟ẚ࡭࡚㧗࠸㏱Ỉಀᩘ࡛࠶ࡿ࡜⪃࠼ࡽࢀࡿࡓࡵࠊୗᒙᅵࡼࡾ 1 ࣮࢜ࢲ࣮⛬ᗘ㧗࠸್ࢆ⏝࠸ࡓࠋࡲࡓࠊ 㢼໬ᇶᒾࡢ㏱Ỉಀᩘࡣ᪤ ◊✲ࡢ⤖ᯝ6㸧_{ࢆཧ⪃࡟ࡋ࡚Ỵᐃࡋࡓࠋィ⟬࡟⏝࠸ࡓᅵተࡢỈ⌮࣭ᙉᗘࣃ࣓࣮ࣛࢱ} ࢆ⾲ 1 ࡟♧ࡍࠋᾐ㏱ィ⟬࡟࠾ࡅࡿᑐ㇟㝆㞵๓ࡢึᮇ᮲௳ࡣࠊᑐ㇟ᩳ㠃࠿ࡽ୍␒㏆࠸᪂ᐑẼ㇟ྎ࡛ほ ࡉࢀࡓ s

T

T

r

\

m(cm)

V

Ks(cm/s) c (N/cm2)

tan

I

Upper soil 0.54 0.3 -40 1.7 0.0035 0.98 0.3 Lower soil 0.54 0.38 -40 1.7 0.0005 0.98 0.3

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2011/9/1 2011/9/2 2011/9/3 2011/9/4 2011/9/5 Ra in fal l ( m m /h ) 0 20 40 60 80 100 Safe ty f a ct o r 0.8 1.0 1.2 1.4 1.6 1.8 Rainfall Safty factor ᅗ 6 㝆㞵ᾐ㏱ゎᯒࡢ⤖ᯝ࠾ࡼࡧࡍ࡭ࡾ㠃ᙧ≧ ᅗ 7 Ᏻ඲⋡ࡢィ⟬⤖ᯝ 䠄Ă䠅㝆㞵๓䠄ϮϬϭϭͬϵͬϭ ϲ䠖ϬϬ䠅 䠄Đ䠅㝆㞵୰䠄ϮϬϭϭͬϵͬϯ Ϯϯ䠖ϬϬ䠅 䠄ď䠅㝆㞵୰䠄ϮϬϭϭͬϵͬϯ ϭϲ䠖ϬϬ䠅 䠄Ě䠅㝆㞵䝢䞊䜽䠄ϮϬϭϭͬϵͬϰ ϯ䠖ϬϬ䠅 䛩䜉䜚㠃 300cm 200 100 0.0 -100 -200 -300 ᑐ㇟㝆㞵࢖࣋ࣥࢺ๓ࡢ1࠿᭶㛫ࡢ㞵㔞ࢆ୚࠼ࡿࡇ࡜࡛ィ⟬ࡋࡓࠋึᮇ᮲௳ࢆィ⟬ࡋࡓᚋࠊ㑣ᬛ኱♫࡛ほ ࡉ ࢀࡓᐇ 㞵㔞ࢆ⏝࠸࡚ゎᯒࢆ⾜ࡗࡓࠋ 㸦3㸧ゎᯒ⤖ᯝ ඛ⾜㝆㞵࡜ࡋ࡚㝆㞵๓ 1 ࠿᭶㛫ࡢ㞵ࢆ୚࠼ ࡓሙྜ㸪ᩳ㠃ୗ㒊࠿ࡽୖ㒊࡟࠿ࡅ࡚ᆅୗ῝㒊 ࡟ ᆅ ୗ Ỉ ᖏ ࡀ Ꮡ ᅾ ࡍ ࡿ ⤖ ᯝ ࡜ ࡞ ࡗ ࡓ 㸦 ᅗ 6a㸧ࠋᑐ㇟࡜ࡍࡿྎ㢼 12 ྕࡣ 4 ᪥㛫࡟ࢃࡓ ࡗ࡚⥅⥆ࡋࡓ㝆㞵࡛࠶ࡗࡓࡓࡵࠊᆅ┙ෆࡢỈ ศ㔞ࡣ஝⇱‵₶ࢆ⧞ࡾ㏉ࡍ⤖ᯝ࡜࡞ࡗࡓࠋᅗ 6b ࡟♧ࡍࡼ࠺࡟㝆㞵ᙉᗘࡢ኱ࡁ࠸᫬㸦2011 ᖺ 9 ᭶ 3 ᪥ 16㸸00ࠊ35mm/hr㸧࡟ࡣᅵᒙ࠿ࡽ 㢼໬ᇶᒾᒙୖ㒊࡟㣬࿴ᖏࡀᙧᡂࡉࢀࡓࠋ㝆㞵 ࡀ⥅⥆ࡋࠊ⣼✚㞵㔞ࡀ 400mm ⛬ᗘ࡟㐩ࡍࡿ ࡜ᅵᒙ㸫㢼໬ᇶᒾୖ㒊࡟Ꮡᅾࡋ࡚࠸ࡓᆅୗỈᖏ࡜㢼໬ᇶᒾ῝㒊࡟Ꮡᅾࡋ࡚࠸ࡓᆅୗỈᖏࡀᩳ㠃ୗ㒊࡛⧅ࡀࡾࠊ ࡼࡾ኱ࡁ࡞ᆅୗỈᖏࡀᙧᡂࡉࢀࡓ㸦ᅗ 6c㸧ࠋࡉࡽ࡟㝆㞵ࡀ⥅⥆ࡋࠊ㝆㞵ࣆ࣮ࢡ᫬㸦2011 ᖺ 9 ᭶ 4 ᪥ 3㸸 00㸧࡟ࡣᩳ㠃ୗ㒊ࡢᆅୗỈᖏࡀᣑ኱ࡋࠊᩳ㠃඲యࡀ࡯ࡰ㣬࿴≧ែ࡟⮳ࡗࡓ㸦ᅗ 6d㸧ࠋ ᅗ 7 ࡟Ᏻ඲⋡ࡢィ⟬⤖ᯝࢆ♧ࡍࠋ㝆㞵๓㸦2011 ᖺ 9 ᭶ 1 ᪥ 6㸸00㸧ࡢᏳ඲⋡ࡣ 1.7 ࡛࠶ࡗࡓࠋ㝆㞵ࡢ⥅⥆ ࡟కࡗ࡚Ᏻ඲⋡ࡣᚎࠎ࡟పୗࡋࠊ9 ᭶ 4 ᪥༗๓ 2 ᫬࡟Ᏻ඲⋡ࡣ኱ࡁࡃపୗࡋࠊ1.05 ࡜࡞ࡗࡓࠋゎᯒ⤖ᯝࡢᏳ ඲⋡ࡣ 1.0 ࢆୗᅇࡗ࡚࠸࡞࠸ࡀࠊᏳ඲⋡ࡢ್ࡑࡢࡶࡢࡣタᐃࡋࡓᙉᗘࣃ࣓࣮ࣛࢱ࡟౫ᏑࡍࡿࡓࡵࠊᏳ඲⋡ࡀ ᛴ⃭࡟పୗࡋࠊ1.0 ๓ᚋ࡜࡞ࡗࡓ 4 ᪥༗๓ 2 ᫬௨㝆࡟ᔂቯࡀⓎ⏕ࡋࡓ࡜⪃࠼ࡽࢀࡿࠋࡲࡓࠊィ⟬ࡉࢀࡓࡍ࡭ ࡾ㠃ࡢᙧ≧㸦ᅗ 6d㸧ࡣࠊᆅᙧゎᯒ࡜㔝እㄪᰝ࠿ࡽ᥎ᐃࡉࢀࡿࡍ࡭ࡾ㠃ࡢᙧ≧㸦ᅗ 4㸧࡜㠀ᖖ࡟ࡼࡃఝࡓ⤖ᯝ ࢆ♧ࡋࡓࠋ௨ୖࡢ⤖ᯝ࠿ࡽゎᯒ⤖ᯝࡣᔂቯࡢⓎ⏕㐣⛬ࢆ෌⌧࡛ࡁࡓ࡜⪃࠼ࡽࢀࡿࠋ ゎᯒ⤖ᯝࡢᏳ඲⋡ࡢపୗࡣ㣬࿴ᖏࡢᣑ኱࡜୍⮴ࡍࡿഴྥࢆ♧ࡋࡓࠋࡇࡢ⤖ᯝ࠿ࡽᏳ඲⋡ࡢపୗࡀ㣬࿴ᖏࡢ ᣑ኱࡟క࠺ᅵሢ㔜㔞ࡢቑຍ࡟ࡼࡗ࡚⏕ࡌ࡚࠸ࡿ࡜⪃࠼ࡽࢀࡿࠋᮏ◊✲࡛ࡣࠊட⿣ࡸ㑅ᢥⓗὶฟ⤒㊰ࢆ⪃៖ࡋࠊ ᐇ ࡋࡓᅵᒙࡢ㏱Ỉಀᩘࡢ್࡟ẚ࡭࡚ࡼࡾ኱ࡁ࡞㏱Ỉಀᩘࡢ್ࢆࣃ࣓࣮ࣛࢱ࡜ࡋ࡚୚࠼࡚࠸ࡿࠋゎᯒ⤖ᯝࡀ ጇᙜ࡛࠶ࡿ࡜ࡍࢀࡤࠊ௬ᐃࡋࡓட⿣ࡸ㑅ᢥⓗὶື⤒㊰ࡢࡼ࠺࡞⣲᪩࠸Ỉ⛣ືࢆྍ⬟࡟ࡍࡿᆅ┙ෆ㒊ࡢᵓ㐀ࡀ

Ꮡᅾࡋ࡚࠸ࡿࡇ࡜ࢆ♧ࡋ࡚࠸ࡿࠋᅵተࡢᑠᐜ㔞ࡢࢧࣥࣉࣝ࠿ࡽᚓࡽࢀࡿ㏱Ỉᛶࡔࡅ࡛࡞ࡃࠊཎ఩⨨㏱Ỉヨ㦂 ࡢᐇ᪋ࡸ㏱Ỉᛶࡢ㠃ⓗ࡞✵㛫ศᕸࢆᢕᥱࡍࡿࡇ࡜࡛ࡼࡾᐇ⌧㇟࡟༶ࡋࡓ㏱Ỉᛶࢆᢕᥱࡍࡿࡇ࡜ࡀᐇ㝿ࡢᔂቯ Ⓨ⏕ᶵᵓࢆ෌⌧ࡍࡿୖ࡛㔜せ࡜࡞ࡿ࡜࠸࠼ࡿࠋ 㸲㸬࠾ࢃࡾ࡟ ᖹᡂ 23 ᖺྎ㢼 12 ྕ࡟ࡼࡗ࡚Ⓨ⏕ࡋࡓ⇃㔝㑣ᬛ኱♫⿬ᒣࡢ኱つᶍᩳ㠃ᔂቯ࡟ࡘ࠸࡚㔝እㄪᰝ࠾ࡼࡧ㝆㞵ᾐ ㏱࣭ᩳ㠃Ᏻᐃゎᯒࢆ⾜ࡗࡓࠋᔂቯࡣ※㢌㒊࡛Ⓨ⏕ࡋࠊ⣙ᖜ 30mࠊ㛗ࡉ 50mࠊ῝ࡉ 12㹼15m ⛬ᗘࡢ኱つᶍ࡞ ࡶࡢ࡛࠶ࡗࡓࠋゎᯒࡢ⤖ᯝࠊ㝆㞵ࣆ࣮ࢡ᫬࡟ᩳ㠃ෆ㒊඲యࡀ࡯ࡰ㣬࿴≧ែ࡜࡞ࡾࠊᏳ඲⋡ࡀᛴ⃭࡟పୗࡋࠊ ᔂቯࡀⓎ⏕ࡋࡓ࡜⪃࠼ࡽࢀࡓࠋࡲࡓࠊࡍ࡭ࡾ㠃ࡢᙧ≧ࡶᔂቯᙧ≧࠿ࡽ᥎ᐹࡉࢀࡿᙧ≧࡜ࡼࡃఝ࡚࠾ࡾࠊᮏ◊ ✲ࡢ⤖ᯝ࠿ࡽᅵᒙ௨῝ࡢ㢼໬ᇶᒾᒙࢆ㝆㞵ᾐ㏱࣭ᩳ㠃Ᏻᐃゎᯒࡢゎᯒᑐ㇟࡜ࡍࡿࡇ࡜࡛つᶍࡢ኱ࡁ࡞ᩳ㠃ᔂ ቯࢆ෌⌧࡛ࡁࡿྍ⬟ᛶࡀ♧ࡉࢀࡓࠋࡋ࠿ࡋࠊゎᯒ᮲௳࡟࠾࠸࡚ᅵᒙࡢ㏱Ỉಀᩘࡣட⿣ࡸ㑅ᢥⓗὶฟ⤒㊰ࢆ⪃ ៖ࡋࠊᐇ ࡢᅵᒙࡢ㏱Ỉಀᩘࡼࡾ኱ࡁ࡞್ࢆタᐃࡋ࡚࠸ࡿࠋࡲࡓࠊ㢼໬ᇶᒾᒙࡢỈ⌮≉ᛶࡣᐇ ࡋ࡚࠸࡞࠸ࠋ 㝆㞵᫬ࡢỈศኚືࡣỈ⌮≉ᛶࡢࣃ࣓࣮ࣛࢱタᐃ࡟౫Ꮡࡍࡿࡇ࡜࠿ࡽࠊᆅ┙ෆ㒊ࡢட⿣ࡸ㑅ᢥⓗὶື⤒㊰࡞࡝ ࡢ୙ᆒ㉁ᛶࡀỈ⛣ື࡟୚࠼ࡿᙳ㡪ࢆᐃ㔞ⓗ࡟ホ౯ࡋࠊゎᯒ࡟⤌ࡳ㎸ࡴࡇ࡜ࡀᚲせ࡜࡞ࡿ࡜࠸࠼ࡿࠋ ㅰ㎡㸸ᮏ◊✲ࡣࠊᆅ┙ᕤᏛ఍㛵すᨭ㒊ࠕࠗ᝿ᐃእ࠘㇦㞵࡟ࡼࡿᆅ┙⅏ᐖ࡬ࡢᑐᛂࢆ⪃࠼ࡿㄪᰝ◊✲ጤဨ఍ࠖ ࡢάືࡢ୍⎔࡟ࡼࡿࡶࡢ࡛࠶ࡾࠊㄪᰝࡢ୍㒊ࡣ࿴ḷᒣ኱Ꮫᖹᡂ 24 ᖺᗘ⊂๰ⓗ◊✲ᨭ᥼ࣉࣟࢪ࢙ࢡࢺ࠾ࡼࡧ ㈈ᅋἲேࣞࣥࢺ࣮࢜ࣝዡᏛ㈈ᅋࡢᨭ᥼ࢆཷࡅ࡚⾜ࢃࢀࡓࠋࡲࡓࠊ⇃㔝㑣ᬛ኱♫࡜ᅜᅵ஺㏻┬㏆␥ᆅ᪉ᩚഛᒁ ᮌୗ⠜ᙪᵝࡼࡾ᝟ሗ࠾ࡼࡧࢹ࣮ࢱࢆᥦ౪㡬࠸ࡓࠋࡇࡇ࡟௜グࡋ࡚ࠊ῝ࡃឤㅰ⏦ࡋୖࡆࡲࡍࠋ ཧ⪃ᩥ⊩ 㸧 ᯇᮧ࿴ᶞ㸪⸨⏣ṇ἞㸪ᒣ⏣Ꮥ㸪ᶒ⏣㇏㸪἟ᮏ᫴ஓ㸪ሐ኱୕㸪୰㇂ຍዉ㸪௒Ἠᩥᑑ㸪ᓥ⏣ᚭ㸪ᾏᇼṇ༤㸪㕥ᮌᾈ஧㸪 ᚨỌ༤㸪᯽ཎె᫂㸪Ọ㔝ⱥḟ㸪ᶓᒣಟ㸪㕥ᮌᣅ㑻㸪Ṋ⃝Ọ⣧㸪኱㔝ு୍㸪㛗ᒣᏕᙪ㸪ụᓥ๛㸪ᅵᒇᬛ㸸2011 ᖺྎ㢼 12ྕ࡟ࡼࡿ⣖ఀ༙ᓥ࡛Ⓨ⏕ࡋࡓᅵ◁⅏ᐖ㸪◁㜵Ꮫ఍ㄅ㸪Vol.64, No.5, pp.43-53, 2012 㸧 ሐ኱୕㸪⸨⏣ṇ἞㸪ᐑᮏ㑥᫂㸪௒Ἠᩥᑑ㸪⸨ᮏᑗග㸪ᅜ㡿ࡦࢁࡋ㸪Ἠᒣᐶ᫂㸸ྎ‴㧗㞝┴ᑠᯘᮧࡢ῝ᒙᔂቯⓎ⏕ᶵ ᵓ࡟㛵ࡍࡿゎᯒ㸪ỈᕤᏛㄽᩥ㞟㸪➨ 55 ᕳ㸪pp.721-726㸪2011 㸧 ᑠᮡ㈼୍ᮁ㸸᳃ᯘࡢỈ※ᾰ㣴ᶵ⬟࡟ᅵᒙ࡜㏱Ỉᛶᇶᒾࡢᯝࡓࡍᙺ๭ࡢホ౯㸪Ỉᩥ࣭Ỉ㈨※Ꮫ఍ㄅ㸪Vol. 20, No.3, pp.201-213, 2007

㸧 Ken’ichirou Kosugi : Lognormal distribution model for unsaturated soil hydraulic properties, Water Resources Research, Vol. 32, pp.2097–2703, 1996

㸧 ኱ᡭಙே㸪㕥ᮌ㞞୍㸸᳃ᯘᅵተࡢᅵተỈศ≉ᛶ㸦ϩ㸧኱ᆺᅵተࢧࣥࣉࣝࢆ⏝࠸ࡿ㣬࿴࣭୙㣬࿴㏱Ỉヨ㦂࡟ࡼࡿయ✚ ྵỈ⋡࣭ᅽຊỈ㢌㛵ಀࡢ ᐃἲ࡜ࡑࡢ㐺⏝㸪᪥ᮏ᳃ᯘᏛ఍ㄅ㸪Vol. 72, No. 6, pp. 468-477, 1990

㸧 ⸨ᮏᑗග㸪㤿ሙ┤㍤㸪ዟ᠇஧㸪ᑠᮡ㈼୍ᮁ㸪῝ᕝⰋ୍㸪㇂ㄔ㸸㢼໬ⰼᓵᒾᒣᆅ࡟࠾ࡅࡿࢺ࣮ࣞࢧࢆ⏝࠸ࡓᇶᒾᆅୗ Ỉࡢὶື≉ᛶࡢᢕᥱ㸪➨ 124 ᅇ᪥ᮏ᳃ᯘᏛ఍Ⓨ⾲せ᪨㞟㸪pp.189