地すべり調査に関連する2,3の問題  [in Japanese] Some Remarks on the Landslide Survey  [in Japanese]

Three points at issue are picked up here. 1) Permeable pipe is conventionally putted in the boring hole to measure the ground water table. It is difficult to interpret water-level observations in an unsealed boring physically. It is shown with a few examples that casing tube should be extended nearly to the bottom of the hole. 2) Electro-optical distance meter surveying is sometimes effective to measure the surface displacements of landslide. Distance surveying has the enough accuracy to show the displacement more than 1 cm. But vector expression should be limited to the landslide that shows large displacement more than 10 cm because angle surveying lead to noticeable error. 3) Shear strength parameters of the landslide clays should be considered based on the characteristics of landslide. These should be determined from a view point of overconsolidated and residual condition.