The method of forecast slope rupture time has been developed on the basis of creep theory. The com parative study among the methods is useful for assessing of their properties.
This paper composes of two parts. First, the forecast models of soil creep deformation and the rupture time of slope are reviewed. Secondly, their mecanical properties are discussed by means of the mathematical analysis.
Models treated are as follows;
1. The foundamental soil creep deformation
(a) Singh & Michell's model: equ.(3)
(b) Kennedy's model: equ.(6)
(c) Komamura's model: equ.(7)
2. The forecast slope rupture time
(d) Saito & Uesawa's model: equ.(9)
(e) Saito's model: equ.(11)
(f) Fukuzono's model: equ.(13)
(g)Kawamura's model: equ.(14)
(h) Omura's model: equ.(19) or equ.(20)
These models are classified with the range in the power number ‘n’ on the relationship between velocity and acceleration: (a) Kennedy's model and Komamura's model are n=1, (b) Fukuzono's model is 1<n<2, (c) Saito's model is n=2, (d) Omura's model is converged to n=2.

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The surface geometry of a landslide, which is defined by the shape, orientation and depth of a slide surface or zone, is essential for stability analysis and for the design of remedial works. This note sets out to demonstrate the accuracy of a technique that utilizes the field surveying of surface displace ments to presume the position and shape of the underlying slide surface.
The technique designated as “polygonal method” presumes the slide surface profile beneath a landslide by a polygonal approximation on the projective plane parallel to a direction of landslide movement.
The accuracy of the technique is examined against results of Komoro landslide analyzed by the method of rotational slide assumption and Narao landslide precisely located by a number of field borehole tests.

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Field observation of snow cover related to landslides in the snow season is extremely difficult to perform. Because of this, the mechanism of outbreak of landslides in the snow season has been explained inferentially and has not been clarified based on field observation data . Therefore, the purpose of this report is to clarify the influence of snow cover and snowmelt upon landslides based upon field observation data. The author reviewed the results of snowmelt observation in Arai city, Niigata prefecture, where the Niigata Experiment Station was located, and also calculated the rate of occurrence of landslides in the Jouetsu District in Niigata based on the results . Morever, the author reviewed the mechanism of outbreak of landslides in the snow season by using field observation data obtained at two landslidezones in Niigata Prefecture.

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