Experimental study on effects of lateral soil flow on group pile and its application to design procedure

• Project/Area Number: 16360234
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Geotechnical engineering
• Research Institution: The University of Tokyo
• Principal Investigator: TOWHATA Ikuo The University of Tokyo, Department of Civil Engineering, Professor, 大学院工学系研究科, 教授 (20155500)
• Co-Investigator(Kenkyū-buntansha): HONDA Tsuyoshi The University of Tokyo, Department of Civil Engineering, Assistant, 大学院工学系研究科, 助手 (30323512)
• Project Period (FY): 2004 – 2005
• Project Status: Completed (Fiscal Year 2005)
• Budget Amount: ¥14,100,000 (Direct Cost: ¥14,100,000); Fiscal Year 2005: ¥4,800,000 (Direct Cost: ¥4,800,000); Fiscal Year 2004: ¥9,300,000 (Direct Cost: ¥9,300,000)
• Keywords: liquefaction / model test / lateral pressure / group pile / ground flow / shaking table / sandy ground / 群杭基礎 / 粘性流体 / 振動台 / 砂地盤 / 横荷重 / 耐震設計

Research Abstract

Model tests were conducted on a 1-G shaking table with a variety of group pile which was embedded in a liquefied sloping ground. Different from foregoing group pile tests with 4 or 9 constituent piles, the present study employed 36 or 121 piles in a square configuration.
Upon shaking the model with different intensities and frequencies, the bending moment was recorded along the length of piles at several piles. Moreover, lateral ground displacement was studied by using data of embedded displacement transducers as well as distortion of soil markers in the ground surface. Records were taken of acceleration and pore water pressure as well. It was revealed that soil flows in the downslope direction upon liquefaction and large deformation occurs around piles. This large deformation makes it very difficult or even inappropriate to analyze the pile-soil interaction by conventional FEM analysis.
The interpretation of bending moment data revealed that the magnitude of bending moment (and consequently the lateral earth pressure) takes the maximum value at the upstream and downstream ends of the pile foundation. This implies that the existence of piles in the upstream direction reduces the earth pressure in the downstream direction, which is called the Shadow Effects, and that, in the downstream end, the ground elevation difference, which is produced by the prevented soil flow by piles, creates significant lateral earth pressure on end piles. The shadow effects vary with the pile spacing ; the narrower spacing makes the shadow effects more remarkable.
Finally, a retrofitting measure for existing group foundation was proposed. That is installation of additional piles on upstream and downstream sides of a foundation. The earth pressure due to flow of liquefied soil is borne by those additional piles and the load on the existing and important piles is mitigated. These findings were examined in a numerical model as well in which liquefied sand is modeled as a viscous liquid.

Research Products

• [Journal Article] Model tests on lateral earth pressure on large group pile exerted by horizontal displacement of liquefied sandy ground. (2006)
  • Author(s): Towhata, I., Sesov, V., Motamed, R., Gonzalez,M.
  • Journal Title: 8th US National Conference on Earthquake Engineering,San Francisco.
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Model tests on lateral earth pressure on large group pile exerted by horizontal displacement of liquefied sandy ground. (2006)
  • Author(s): Towhata, I., Sesov, V., Motamed, R., Gonzalez, M.
  • Journal Title: 8th US National Conference on Earthquake Engineering, San Francisco paper No.1227
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Model tests on lateral earth pressure on large group pile exerted by horizontal displacement of liquefied sandy ground (2006)
  • Author(s): Towhata, I., Secov V., Gonzalez, M.
  • Journal Title: Proc.8th US National Conference on Earthquake Engineering, San Francisco
• [Journal Article] Shaking Table Tests on Pile Group Behaviour in Liquefied and Laterally Spreading Group. (2005)
  • Author(s): Sesov, V., Towhata, I., Ishimatsu, S., Gonzales,M.
  • Journal Title: 第40回地盤工学研究発表会 Pages: 1619-1620
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Development of Geotechnical Earthquake Engineering in Japan (2005)
  • Author(s): Towhata, Ikuo
  • Journal Title: Heritage Lecture,XVIth International Conference on SoilMechanics and Geotechnical Engineering,Osaka Vol.11 Pages: 251-291
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Experimental Study on Large Pile Group Response Subjected to Lateral Flow of Liquefied Ground (2005)
  • Author(s): Sesov, V., Towhata, L., Gonzalez, M., Ball, R., Ishimatsu,S.
  • Journal Title: Proc. TC4 Satellite Conference,Int.Conf.Soil Mechanics and Geotechnical Engineering,Osaka Vol.4 Pages: 221-227
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Performance of pile foundation in multi-layered liquefied soil (2005)
  • Author(s): Sesov, V., Towhata, L., Gonzalez, M.
  • Journal Title: Proc. 16^<th> Int. Conf. Soil Mechanics and Geotechnical Engineering,Osaka Vol.4 Pages: 2183-2186
  • NAID: 130004622034
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Shaking Table Tests on Pile Group Behaviour in Liquefied and Laterally Spreading Group. (2005)
  • Author(s): Sesov, V., Towhata, I., Ishimatsu, S., Gonzales, M.
  • Journal Title: 40^<th> National Conference of Japanese Geotechnical Society Pages: 1619-1620
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Development of Geotechnical Earthquake Engineering in Japan. (2005)
  • Author(s): Towhata, Ikuo
  • Journal Title: Heritage Lecture, XVIth International Conference on Soil Mechanicsand Geotechnical Engineering, Osaka Vol.11 Pages: 251-291
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Experimental Study on Large Pile Group Response Subjected to Lateral Flow of Liquefied Ground. (2005)
  • Author(s): Sesov, V., Towhata, I., Gonzalez, M., Ball, R., Ishimatsu, S.
  • Journal Title: Proc.TC4 Satellite Conference, Int.Conf.Soil Mechanics and Geotechnical Engineering, Osaka Vol.4 Pages: 221-227
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Performance of pile foundation in multi-layered liquefied soil. (2005)
  • Author(s): Sesov, V., Towhata, I., Gonzalez, M.
  • Journal Title: Proc.16th Int.Conf.Soil Mechanics and Geotechnical Engineering, Osaka Vol.14 Pages: 2183-2186
  • NAID: 130004622034
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Development of Geotechnical Earthquake Engineering in Japan (2005)
  • Author(s): Towhata, Ikuo
  • Journal Title: Heritage Lecture, XVIth International Conference on Soil Mechanics and Geotechnical Engineering, Osaka Vol.1 Pages: 251-291
• [Journal Article] Experimental Study on Large Pile Group Response Subjected to Later al Flow of Liquefied Ground, (2005)
  • Author(s): Sesov, V., Towhata, I., Gonzalez, M., Ball, R., Ishimatsu, S.
  • Journal Title: Proc.TC4 Satellite Conference, Int.Conf.Soil Mechanics and Geotechnical Engineering, Osaka Vol.4 Pages: 2183-2186
• [Journal Article] Performance of pile foundation in multi-layered liquefied soil (2005)
  • Author(s): Secov V., Towhata, I., Gonzalez, M.
  • Journal Title: Proc.16^<th> Int.Conf.Soil.Mechanics and Geotechnical Engineering, Osaka Vol.14 Pages: 2183-2186
  • NAID: 130004622034
• [Journal Article] Shaking table tests on pile group behaviour affected by liquefaction induce lateral spreading (2004)
  • Author(s): Sesov, V., Towhata, L., Gonzalez, M.
  • Journal Title: 3rd International Conference on Continental Earthquake
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Model test on response of large pile group under lateral flow of liquefied sandy soil ground (2004)
  • Author(s): Sesov, V., Towhata, L., Gonzalez, M., Ball, R., Ishimatsu,S.
  • Journal Title: Proc.Symp.on Behavior and Design of Piles Embedded in Liquefied Ground,Japanese Geotechnical Society Pages: 321-324
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Shaking table tests of pile group behavior affected by liquefaction induced lateral spreading. (2004)
  • Author(s): Sesov, V, Towhata, I., Gonzalez, M.
  • Journal Title: 3rd International Conference on Continental Earthquake
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Model test on response of large pile group under lateral flow of Liquefied sandy soil ground. (2004)
  • Author(s): Sesov, V., Towhata, I., Gonzales, M., Ball, R., Ishimatsu, S.
  • Journal Title: Proc.Symp.on Behavior and Design of Piles Embedded in Liquefied Ground, Japanese Geotechnical Society Pages: 321-324
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Shaking table tests on pile group behaviour affected by liquefaction induced lateral spreading (2004)
  • Author(s): Sesov, V, Towhata, I., Gonzalez, M.
  • Journal Title: 3rd International Conference on Continental Earthquakes, Beijing
• [Journal Article] Model test on response of large pile group under lateral flow of liquefied sandy soil ground. (2004)
  • Author(s): Sesov, V., Towhata, I., Gonzales, M., Ball, R., Ishimatsu, S.
  • Journal Title: Proc.Symp.on Behavior and Design of Piles Embedded in Liquefied Ground, Japanese Geotechnical Society Pages: 321-324