APPLICATION OF A NEW NAILING METHOD FORSTABILIZING FORESTED SLOPES

摘要

Most of the watersheds of the major rivers in Japan have very steep profiles. Thesteep watersheds are characterized not only by high-gradient streams but also by steepvalley side slopes. When a landslide occurs, the soil mass moves rapidly downstream thatcauses soil erosion to be more serious. Additionally, about 90% of Japanese landslides areshallow landslides with slip surface ranging from 0.5 to 3.0 m in depth, that increases thesurface erosion of the slopes. The construction of slope stabilization thus becomes a veryimportant subject of soil erosion control. However, constructing landslide countermeasuresoften clears vegetation, a key factor of erosion control. To avoid such a problem, weproposed a new nailing method named Non-frame. The mechanism of Non-frame is similarto the mechanism of tree root fibers reinforcing a slope by deeply keeping the unstable soillayer in the bedrock. This method can stabilize the forested slopes while protecting thevegetation and thus minimizing the effects of humans to the natural environment. Non-framemethod is structured from a number of steel bars having fixed plates at their heads. The steelbar heads are connected to each other by a wire net. When the slope becomes unstable andslides down, steel bars nail the unstable soil layers into the stable soil layers. Under theeffects of mass movement, steel bar is laterally deflected as a root fiber in a landslide. Whenthe longer displacement of landslide or the larger deflection of steel bar occurs, the steel barscreate the larger reinforcement. This paper presents the structure, the experiments and thecalculation model of Non-frame method. The influences of rainfall and earthquake on theerosion process of the slopes are also discussed with two illustration examples in Non-framefields.