Abstract：Tunnel boring machine(TBM) has been widely employed in recent years. In general，for a mixed action of shear，crush and tension，the detritus are formed. Rock detritus dimensions and particle distribution are the key factors of TBM mechanical parameters related to the rock properties，which will influence TBM energy utility and excavation efficiency. They are influenced by cutter spacing，cutter thrust forces and rock characteristics. According to the mechanism of detritus formation，detritus dimensions constitution and its characteristics are discussed. Based on the field TBM tunneling practice，Chongqing Yangtze River tunnel，detritus samples are collected according to rock types and thrust forces magnitude. Then，detritus measuring and screen tests are implemented，and vast data about detritus size are acquired. According to probability statistic theory，detritus dimensions of mudstone and sandstone are matched by normal distribution fitting method. Finally，the measured detritus distributions are calculated and compared with theoretical distribution models(lognormal distribution function and Rosin-Rammler distribution function). Some conclusions for the detritus dimensions，particles distributions and their relations to mechanical parameters are obtained. These conclusions will benefit for improving cutter head layout design and TBM performance.
