Shear displacements at different shear zones in deep-seated landslide, the Kojima landslide at Kochi, Japan was examined based on the measurement of vertical profiles of displacements in bore holes within the landslide mass and around the landslide area. Multiple shear zones were identified at a bore hole in active landslide area while only a shear zone was identified at the outside of the landslide. Shallower shear zones were identified within the landslide mass and deeper shear zone was identified at the bottom of landslide mass in active landslide area. Shear zones at different depths of a bore hole showed different response to rainfall. Shallower shear zone displaced depending more on the rainfall amount. While the displacement of deeper shear zone might depend more on the gravitational deformation. The increase of the displacement by heavy rainfall event is smaller at deeper shear zone than that at shallower shear zone. It suggests displacements under different deformation mechanism occurs in the deep-seated landslide.
The Lumped mass damper model (LMDM) is a model to predict the landslide moving velocity, with a clear slip surface including rockslide, in the primary creep to the secondary creep stage of the landslide movement. However, in the current LMDM, when the landslide movement velocity increases, and enter the third order creep stage, the velocity of LMDM deviate from the actual displacement amount step by step. Therefore, in order to solve this problem, we designed a model considering 'reduction of friction coefficient' or 'decrease of Cd' with increasing velocity. As a result, it was found that landslide displacement up to the final failure stage can be predicted. We describe this method and report its physical meaning. In addition we mention to Tank Model on LMDM.
While travel distance (L) of landslides has been studied for decades, researchers have continued updating the statistical data and the methods to estimate L. The statistical data of different countries commonly show that relationships exist between L, volumes of debris (V), and/or fall heights (H) from the crest of the landslides. However, there are not many publications that examined the potential differences in L, depending on whether the slope consists of jointed rock or fine soil. This research concerns the rock slope failures that spreads rock debris on flat area such as roads. Particularly, the effects of joint spacing (JS) and the dynamic friction angle (α) on L were assessed by 2-dimensional distinct element code (UDEC v.6.00). The simulated relationship between H and L agreed with those of the actual failure records and the effect of α and on L was consistent with the past findings. Although it was not possible to reduce JS below certain size due to computational time limit, results of the simulations suggest that JS is an influential factor such that L tends to decrease as JS increases.