InTBM excavation

the composite rock strata are often encountered

in such acase

it is not easy to estimate surrounding rock strength during tunnelingwhere the tunnel face and wall tend to collapse. For improvement of tunnelingefficiency and disaster prevention

it is necessary to estimate surroundingrock strength in real time. Based on laboratory tests and field data in theconstruction of Chongqing Railway Line 9

it was found that the thrust is proportional to rockstrength

it was also found that the ratio of the torque force to thrust

/were proportional to (penetration ). In this study

for composite rock strata(includingsandy mudstone

sandstone and limestone) surrounding tunnel

a method that canquickly estimate surrounding rock strength from thrust and torque measuredin-site

was developed. The method can estimate rock strength in real time withtwo constants

which can be obtained bylinear fitting of the field data for TBM. The method had been already appliedto more than ten tunnels. It was found that two constants were only related tothe number of disc cutters and cutter-head diameter for thisgeological environment of composite rock strata. The results provide a morepractical and feasible idea to estimate surrounding rock strength in real time

and also can improve the reliability and safety of tunnel TBM construction.