Infrastructure development in urban areas has progressed rapidly, and the demand for construction of pipes for electricity, gas, water supply and sewerage, etc. is increasing. In the urban construction of pipe, the non-open cut method is generally used to prevent traffic disturbance, building influence, noise and vibration, one of which is a Shield method. Shield method is a construction method that rotates the cutter head at the tip of the shield machine, excavates the ground, and constructs an underground pipe ditch.

In recent years, construction condition of Shield method is diversified such as long distance, great depth, high water pressure and gravel ground, etc. Bit wear is a factor affecting workability and economic efficiency in Shield method, and the various investigations have been discussed so far, but the quantitative guidelines on bit wear prediction have not been established because the wear factor is complicated in the gravel ground. This study was conducted in order to obtain fundamental knowledge for predicting bit wear in gravel ground.

1. Introduction

The shield machine has the cutter head with bits as shown in Fig.1, and the ground is excavated by rotating the cutter head and pushing it by thrust jacks. However, the bit wear during cutting operation is inevitable. As the bit wear has an obvious impact on the construction progress and cost, such as lowering of drivage efficiency, increasing the frequency of bit replacement, etc (H. Shimada et al, 1989). Therefore, the prediction of cutter bit wear in advance is important. However, there is few research on the characteristics of bit wear in gravel ground and the prediction method of the bit wear in theoretically and quantitatively.

From above point of view, this paper discusses the effects of characteristics of gravel and the gravel content on the characteristics of bit wear in gravel ground based on the results of a series of laboratory tests for the simulated sample of the gravel ground in order to develop the prediction method of bit wear for excavation in gravel ground.

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