Abstract

When a tunnel is constructed in a landslide area, the excavations may induce the instability of nearby slopes. However, it is not clear how tunnel excavations actually affect landslide behavior. In order to establish a design for both the construction method of the tunnels and the countermeasures required for such unstable conditions, it is important to reveal the mechanism of the behavior.

The objectives of this study are to find an appropriate numerical modeling to simulate the displacement behavior of a landslide slope due to tunnel excavations and to discuss the mechanism of the behavior.

1. Introduction

When a tunnel is constructed in a landslide area, the excavations may induce the instability of nearby slopes. The tunnel entrance is one part that requires particularly great care during the tunnel construction. However, it is not clear how tunnel excavations actually affect land slide behavior.

In this paper, firstly, the results of field measurements obtained at a tunnel constructed under a landslide area are shown to indicate the real landslide behavior due to tunnel excavations. Secondly, numerical simulations are conducted to understand and to discuss the mechanism of the behavior. The Finite Element Method (FEM) and the Distinct Element Method (DEM) are usually used for the numerical analysis of tunnel excavations. However, it is difficult to simulate the displacement behavior of a landslide slope due to tunnel excavations with either of these methods. Therefore, an appropriate numerical procedure that can express the sliding and the separation behavior of the ground materials is required. A numerical modeling is proposed using DEM, and finally the mechanism of the landslide behavior is discussed.

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