The effects of the drainage pipe on the ground water level during rainfall are predicted with the 3D FE analyses of transient water flow through unsaturated-saturated soils. The slope stability is evaluated by the global safety factor, based on the 3D elasto-plastic shear strength reduction FEM. The calculated results indicate that the drainage pipe can effectively lower the ground water level, and increase the slope stability duringrainfall.

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When a cut slope is constructed in a saturated clay ground, pore water pressure decreases instantly due to unloading. With time, the ground will expand gradually and the pore water pressure will rise towards long-term state. During this process, air may be absorbed into the slope; consequently, an unsaturated zone appears in the vicinity of the ground surface. In simulating such a swelling process, most existing FE methods neglect the air ingress into the slope and the whole analysis region is assumed saturated. However, this assumption leads to erroneous results, i.e., the factors of safety for assumed slip circles may increase with time; this is discussed in the first half of the text on the basis of illustrative examples. It is inferred that the erroneous results come from the improper assumption of the only saturated analysis. Hence, in the last half of the paper we employ a three-phase saturated-unsaturated model incorporated with an elasto-plastic constitutive relation to take into account the appearance of the unsaturated zone during swelling. This model is applicable not only for saturated problems but also for unsaturated ones. The results indicate that the proposed method can correctly represent the soil behavior of cut slopes, therefore, leading to the conclusion that the only saturated analyses are not adequate for cut slope problems.

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Many landslides have occured at the serpentinite belt. Mineralogical characteristics of the serpentinite related to the landslides are investigated. The observation by a light microscope and X-ray analysis were carried out. The serpentinite involved a serpentine, brucite and magnetite. The brucite is easily subject to the chemical weathering. As the serpentinite is very fragile, the slope failure occurs easily. The magnetite is stable to the chemical weathering and the serpentine don't change into the clay minerals. So the gentle slope in the serpentinite belt don't slide. Many landslides have occured at the edge of the serpentinite belto.

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Pore water pressure fluctuation is proved to be an important cause of landslide movement in landslide areas, but it is difficult to observe the mechanism of pore water pressure fluctuation at the various depth of slip surface. The purpose of this paper is to examine the pore water pressure fluctuation in shallow and deep stratum at the slip surface. The data used in this study was collected at Tairasawa landslide area during 1983-1985. Two observational methods are considered.(1) The pressure heads were measured in the vertical observation borehole with a screened section at the designated depth of slip surface.(2) The horizontal borehole of drainage wells were drilled for confined groundwater in a screened section at the same depth of slip surface. The rainfall, pressure head and drainage discharge were observed before and after the drainage well works.
The results indicated that after drilling a horizontal borehole, the pore water pressure was low in shallow and deep stratum at the slip surface. It is possible to judge the effects of drainage well works by comparing the drop of pore water pressure before and after the works. Furthermore, the drop of pore water pressure at the slip surface have two significant characteristics. First, the dropping variation of pore water pressure is corresponding to drilling depth and seepage water in a horizontal borehole. Secondly, the dropping effects of pore water pressure can be clearly prove when the drilling direction of a horizontal borehole near the vertical observation borehole.

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The deflection and stress of gridwork type earth anchor beam has been carefully studied by the general elastic theory.
Calculating four kinds of integration constants through boundary condition by trial and error methods, the specific relations between these constants have been found out for the following two models.
MODEL 1: No interpenetration at the center of the beam
C₁: C₂=C₃: C₄
MODEL 2: Infinite length between the anchors
C₁=-C₂ C₃=C₄
Moreover, the new method whitch can calculate generally the deflection and stress of anchor beam has been found out.
From the evaluation of the calculated results of both methods (Chang's equation and Four constants method), Chang's method gives smaller bending moment by 4.5% and longer pressed span by 50% for MODEL 2, while both methods give the similar results for MODEL 1.
The careful consideration is recommended for the application of Chang's equation for the MODEL 2, where the reaction from the ground should be considered.

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