Study On The Mechanism And Curing Method Of Blocking In EPBS

As the rapid development of underground engineering, shield tunneling method is becoming a comprehensive way to build the subway engineering with safety and environmental protection. The famous project of Gas Transiting West to East and the Cross-river tunnel of Huangbu River in Shanghai also will be constructed with this technique ,which is under the plan .Among the shield tunneling methods, up to now , earth pressure balanced shield tunneling (EPBS) is the most universal type ,and it is very certain that the EPBS method adopt to our country increasingly .The key factor to success in EPBS is converting the muck which is lack of fluidity excavated from the cutter face to the plasticity soil .But when the shied tunneling machine advancing, it is considerably difficult to reach this requirement because of the ground soil condition, which is consist of stiff clay, silt, weathered rock, and so on. As we know, when meeting these soils, many breakdown and danger will occur, such as the blockings, which has attracted attention of many construction personal on site.However, at present, there exist many unknown fields in blocking. Firstly, the definition of blocking is not interpretative. When the machine driving, it must be identified what accident is blocking. Secondly, the mechanism of the blocking, and that means why this problem occurred. Thirdly, the effected factor of the blocking. Last one is how to prevent or cure the blocking and the quantitative measure is not put forward yet. As to the four items above, the study in home and oversea is almost vacant at present.Accordingly, this paper' emphases are placed in these unfathomed problem, and the work and research hereinafter was done:1) The initial and perfect state of soil in pressure chamber was brought forword, and some reason about breakdown or problem due to soil condition was analyzed concisely.2) Aimed at the blocking, the mechanism of this problem is studied. The doming model of soil in pressure chamber is built. And consequently, the expression of doming coefficient ( .) is put forward. Based on the model, the terms and conditions of the blocking is approached according to actual cases of the factual tunneling project. And the sensitivity of the parameter influencing the blocking is analyzed. So the theoretical basis of effective prevention and cure is given.3) The possibility regions of blocking occurring are divided in allusion to the different soil condition, with which may be met in EPBS construction.4) The foam of shield tunnel is development, the prevention and cure of shield tunnel in Guangzhou is given based on the experiments.