Stress-strain soil behavior during tunneling in soft ground: experimental study on 1g-earth pressure balanced shield model

Since several years, the ENTPE's Geomaterial Laboratory in Lyon (France) has started a large experimental project based on the so-called "Earth Pressure Balanced Shield" (EPBS) method adapted to tunneling in soft ground. Within the framework of the project, a specific reduced-scale physical model of the EPBS (1:10 approximately) was built. A first objective has been to perform a direct rational analysis at the model scale, aimed to understand the different mechanisms occurring during the EPBS method of tunneling. In a second stage, this analysis and the resulting data base will be used to elaborate a numerical modeling of this method. The present paper presents typical test results obtained with the EPBS model for frictional - cohesive material (humid fine silica sand). These results concern the stress-strain soil behavior during ideal tunneling rate. Moreover, the sensitivity of the main control parameters available on the command shield and the action of the cutter head are debated.