Strength Decreasing due to Dynamic Stress of Earthquake
Project/Area Number  04650442 
Research Category 
GrantinAid for General Scientific Research (C)

Allocation Type  Singleyear Grants 
Research Field 
基礎・土質工学

Research Institution  Ehime University 
Principal Investigator 
YAGI Norio Ehime University, Faculty of Engineering.Professor, 工学部, 教授 (00027228)

CoInvestigator(Kenkyūbuntansha) 
ENOKI Meikwtsu Ehime University, Faculty of Engineering, Associate Professor until 1992. Tottor, 工学部(平成4年度分担者 平成5年4月1日転出), 教授 (90136309)
YATABE Ryuichi Ehime University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (70127918)

Project Period (FY) 
1992 – 1993

Project Status 
Completed(Fiscal Year 1993)

Budget Amount *help 
¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1993 : ¥400,000 (Direct Cost : ¥400,000)
Fiscal Year 1992 : ¥1,700,000 (Direct Cost : ¥1,700,000)

Keywords  Sand / Clayy soil / Cyclic shear / Liquefaction / Pore water pressure / Shear strength / Simple shear apparatus / 非排水せん断強度 / 応力履歴 
Research Abstract 
This research consists of three parts, that is, 1) pore water pressure and liquefaction of saturated sands due earthquake, 2) strength characteristics of clayy soil to which a cyclic shear stress have applied, 3) development of a simple shear apparatus in which arbitrary stress conditions can be controlled. The cyclic shear tests for the three kinds of soils were carried out using the triaxial apparatus. Amplitudes of strain of both compression and extesion sides become nearly same by the proposed method of giving cyclic shear stress. Resistance of silty soil of OCR=5 for liquefaction corresponds to one of sand of 40% relative density. An increase of pore water pressure in one cycle of shear stress can be expressed as the function of the ratio of the amplitude of the shear stress to the effective stress and it is possible to calculate the pore water pressure due to a random shear stress wave. The resistance for liquefaction have good correlation to a dilatancy coefficient. The pore water pressure of a clayy soil due to cyclic shear is also expressed by the same function for sand. The strength parameters in terms of effective stress is constant regardless of disturbance and history of cyclic shear, but the effective stress path is influenced by the history of cyclic shear. The coefficient of pore water pressure at failure and the effective stress path are determined by the proposed parameter b for the soil having the history of cyclic shear. Magnitude of shear strength of the specimens which have same water content is in order of over consolidated, having cyclic shear and remolded reconsolidation. The strength parameters from the simple shear apparatus is nearly same one from the triaxial test.

Report
(3results)
Research Products
(5results)