A Study of Snow Induced Landslide Behavior And Its Observation System

多雪地区的滑坡灾害多由积雪和复式碎屑岩、膨润软粘土的绿色地质环境引起。然而，雪致滑坡的具体行为和碎屑绿岩的力学性质尚不清楚，开发滑坡观测系统尤其是雪季滑坡的观测系统仍有待研究。我们的研究项目从1993年到1994年为期两年，主要目的是研究上述问题。本研究取得的成果概括如下：(1)根据收集的滑坡记录，由于积雪融化和土体软化，易在晚春发生大型滑坡。(2)对大雪区滑坡区进行土样采集和滑坡土室内试验，建立了膨胀性本构方程，该本构方程适用于所有膨胀性土。(3)从试验结果中得到了绿泥土的许多力学性质之间的有效关系，如残余抗剪强度与残余内摩擦角之间的高度相关关系、残余内摩擦角与残余抗剪强度之间的关系、残余内摩擦角与残余抗剪强度之间的关系等。此外，还发现了抗剪强度与含水率法向应力之间的特殊关系，即破坏机理的库仑定律不适用于含水率高于35%的样品。(4)为了对1991年地方政府指出的每一种潜在滑坡的风险度进行评估，应用主成分分析方法，绘制了秋田县、山形县和宫城县新的潜在滑坡图，这对防治滑坡灾害非常有用。(5)在滑坡区顶部建立了雪情自动观测系统，取得了较好的研究成果，可用于了解雪崩滑坡的行为。

Most of landslide disasters in the snowy regions are considered to be caused by deposited snow, and greentuff geological environment of composite clastic rocks and bentonic soft clays. However, detailed behavior of snow induced landslides, mechanical properties of clastic greentuff are unknown, and still remain to be studied to develop observation system of landslides especially in the snowy seasons.The main objective of our present research project for a period of two years from 1993 to 1994 is to study above mentioned points. The results obtained in the research project are summarized as follows.(1) According to the collected records on landslides, huge landslides tend to take place at the late spring because of melting snow and accompanying softened soils.(2) Soil sampling in the landslide areas in the heavy snowfall regions and laboratory tests of landslide soils were performed, and a constitutive equation for swelling behavior was found, and it was fit for swelling phenomena for all bentonic soils.(3) From testing results, many effective relationships among the mechanical properties of greentuff soils were obtained, for example, high relationship between residual shear strength and residual angle of internal friction, besides a special relationship between the shear strengths and normal stresses by water contents were found, i.e., Coulomb's law for failure mechanism was not fit for the samples whose water content higher than 35%.(4) To review the risk degrees of each potential landslides which were pointed out by local government in 1991, principal component analysis method was applied, and new potential landslide maps were thus made for Akita, Yamagata, and Miyagi ptrefectures.These are very useful to prevent and control landslide disasters.(5) Automatic observation system for snow weather situations was set up at the top of landslide area, and effective results were obtained to make clear the behavior of snow induced landslides.