Quantitative Analysis of Construction Loads Acting on Shield Tail by Using the Kinematical Shield Model
Supervisor Mitsutaka SUGIMOTO
Today, shield is controlled by an expert system. There are many unknown properties such as ground properties, external forces and construction loads. So this system is based on experience rules and doesn't have a theoretical background. The kinematical shield model considering the ground-shield interaction is required.
It had been confirmed through the previous researches that the kinematical shield model can represent actual shield behaviors. Nowadays, underground structures in cities are very congested. So, shield tunnel has been constructing in a deep underground and at a sharp curve. And segments have been wider and thinner for saving the cost. Therefore, the stress in segments due to construction loads is larger than before. According to construction results, ground water leakage into a tunnel occurred at a sharp curved tunnel alignment due to the tunneling construction loads on segments, which comes from the decrease of tail clearance. To make clear its influence on segments, it is necessary to develop the model, which can represent the force acting on tail accurately. This research aims to improve the kinematical shield model so as to estimate construction loads on segments quantitatively.
As a result, the following conclusions were obtained.
1) Construction loads acting on shield tail influence the movement of shield. And when grout material is intruded and hardened up in shield tail, construction loads increase. This phenomenon might cause the difficulty in control of shield tunneling performance.
2) As a result of the simulation that was carried out at the sharp curved section, the simulated shield behavior has a good agreement with the observed one. This represents the validity of the newly improved kinematical shield model.
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