PREDICTION AND ANALYSIS OF ABRASIVENESS OF DENSE SANDY STRA-TUM BY SLURRY SHIELD AT SUTONG GIL UTILITY TUNNEL ENGINEERING

The wear of the cutter in the high abrasive dense sandy stratum seriously restricts the construction efficiency. This paper aims to accurately predict the wear and the digging distance of the scraper of the large diameter slurry shield TBM.It statistically analyses the dense composite sandy stratum by counting the area ratio and the volume ratio of each stratum in the typically tunnel cross section and district. The sandy stratum distance ranges from the DK0+0 to DK1+780 of Sutong GIL Utility Tunnel Engineering. The weighted average abrasion coefficient K' and its variation for each cross section and district in the composite sandy stratum can be obtained by combining the area ratio of each stratum, the volume fraction of each stratum and the abrasion coefficient K of each stratum. The calculated weighted average abrasion coefficient K' and the corresponding tool wear model are used to predict the tool wear and the digging distance of the large diameter slurry shield TBM in the dense composite sandy stratum. The results of tool wear and life prediction are compared with those in the actual construction process of large diameter slurry shield in Nanjing Yangtze River Tunnel under similar engineering geological conditions. The results show that the weighted average abrasion coefficient K' gradually increases with the increase of the mining mileage. The maximum value is at the milestone of 1778m and the maximum value is K'_max=18.36×10^-3mm·km^-1. The maximum wear of the cutter locates at the installation diameter D=12.07m. If the upper limit wear value is set as δ=5mm, the cutter needs to be replaced twice, with the corresponding digging distance of L₁=1063m and L₂=453m. The comparison with the actual wear of the slurry shield TBM in Nanjing Yangtze River Tunnel shows that the prediction results are reliable. The results of the study provides theoretical basis for the wear prediction and cutter replacement of the slurry shield TBM in the Sutong GIL Utility Tunnel Engineering and similar cross-river tunnels.