Abstract
　There is a regularity in the occurrence of cracks on the upper surface of landslide debris (Fig.1) , and some hypotheses have been introduced (Fig.2) (FUJITA et al., 1981)
　In order to explain these hypotheses by means of scale-model experiments, the present authors devised an experimental machine (Figs.4, 5). To make the mode body, bentonite knead with water of 83.5% (weight ratio) was used. One model was for the experiment on the occurrence of crack groups at the head of the landslide debris (Fig.6), and another was for the experiment on the occurrence of cracks along the rise in the downstream part (Fig.7). In both experiments the hypotheses were verified as illustrated in Fig.8.
　On the low-angled cracks that were formed in the above-mentioned experiments, the authors experimented with a newly prepared machine (Fig.9), and obtained the results shown in Fig.10. On the occurrence of such cracks, the authors reached a conclusion as shown in Fig.11.
　Referring to these results, the authors mentioned three items of the possible utility of the landslide debris cracks for the science of disaster prevention.

*新潟大学積雪地域災害研究センター
The Research Institute for Hazards in Snowy Areas, Niigata University
**石油資源開発k.k.
Oil Resources Development Co., Ltd.
***自営業
Independent Enterprise
****安藤建設k.k.
Ando Construction Co., Ltd.
*****植木組
Uekigumi Co., Ltd.