Journal of Natural Disaster Science

FIELD INVESTIGATIONS IN LANDSLIDE AREAS AND SHEARING STRENGTH OF SOIL FOR USE IN STABILITY ANALYSIS

Toshio IKEDA
Professor, Department of Civil Engineering, The Technological University of Nagaoka
Shoji OGAWA
Professor, Department of Civil Engineering, The Technological University of Nagaoka
Kazuo KONAGAI
Associate Professor, Department of Civil Engineering, The Technological University of Nagaoka
and
Takeshi KAMEI
Research Associate, Department of Civil Engineering, The Technological University of Nagaoka

(Received 23 Dec., 1985 and in revised form 5 June, 1986)

Abstract

To investigate seasonal variations in the groundwater level and porc water pressure in landslide areas, we made field investigations at several landslide areas. In addition, we conducted two kinds of ring shear test on soils taken from some of these areas in order to determine the fundamental strength parameters of the soils.

Our main conclusions from the field and laboratory investigations are 1) The groundwater level and pore water pressure at the slip surface in landslide areas change seasonally, with marked increases after the snow-melting and heavy rainfall seasons. 2) Pore water pressures at the slip surfaces do not always coincide with hydraulic pressure values calculated from the groundwater level. Therefore, when making slope stability analyses and taking preventive measures against reslidings, pore water pressures should be measured directly all along the slip surface with piezoelectric meters. 3) Determination of strength parameters using a ring shear apparatus is useful in making stability analyses of slopes in landslide areas.

Key words

field investigation, groundwater, landslide, porewater pressure, stability analysis