Abstract: To investigate the mechanical behavior of the interaction between cutters on an earth pressure balance shield and the sandy gravel strata as well as reveal the loosening mechanism of wedgeshaped cutters, the sandy gravel strata ahead of the cutterhead are regarded as a continuous medium, and the failure strength of the strata under loosening effect of a wedgeshaped cutter is determined using the Terzaghi bearing capacity formula and MckyesAli model. Then, the plow loosening index [WT《TNR#I》]k[WT《TNR》] is introduced to characterize the principle of plow loosening when the wedgeshaped cutter repeatedly cuts the strata, the friction and strength between particles are gradually reduced, and the stratum force under the cutterhead cutting has a complex cutter arrangement. The circumferentialloosening force and axialjacking thrust required for strata cutting by a single wedgeshaped cutter are calculated, stress calculation methods for loosening the wedgeshaped cutter and dropping the scrape cutter are proposed, the torque and penetration thrust required by the cutterhead are obtained, and the influence factors of both thrust and torque are analyzed. The stress state(torque and thrust) of wedgeshaped cutters and scrapers calculated using the proposed methods agree well with the monitoring results, demonstrating that the thrust and torque of the cutterhead required for strata cutting can effectively reduce the layered arrangement of wedgeshaped cutters ahead of scrapers,  thereby reducing the total thrust and total torque of the shield.

Key words: sandy gravel strata, earth pressure balance shield, wedgeshaped cutter, plow loosening principle, thrust, torque