| Summary: | [Introduction] The paper aims to research the settlement regular and mechanism of the ash dam according to the similarities and differences of measured settlement and conventional settlement regular analysing results. [Method] Firstly, the conventional settlement regular and mechanism of shield construction were introduced in details. Secondly, the settlement regular of the ash dam was researched by the measured settlement curve of the tunnel through the ash dam, and the measured settlement, numerical simulation of settlement and conventional settlement regular were comprised and analysed. Finally, the causes of the sudden change of the settlement of the ash dam were analysed, and the settlement mechanism of the ash dam was obtained. [Result] The results show that the stone riprap of ash dam is large and uneven, its cohesive force is poor, and its gap is large, thus lead to shield excavate difficulty and easy to cause over-excavation and under-excavation, which is the reason for the difference between ash dam settlement and general settlement law. After the shield tunneling, all the measuring points are sliding towards the tunnel palm face rapidly, shows that there are some external factors causing formation deformation and mutation, the law of actual measurement is obviously inconsistent with the general law. The recombination of ash dam stone riprap structure causes the stratum to slip to the palm face, the surface subsidence mechanism of ash dam is obtained. The results of this paper also show that the ash dam reinforcement is very important to the shield construction safety. [Conclution] The research results can provide references for other similar projects.
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