Zongxi Cai

Modeling Specific Energy for Shield Machine by Non-linear Multiple Regression Method and Mechanical Analysis

The specific energy, defined as the energy consumption to complete the excavation of unit volume of the soil, can well describe the working efficiency of a shield machine. An identification model of the specific energy is established in this paper by introducing the mechanical analysis of the shield excavating process into the nonlinear multiple regression of the on-site data. The mechanical analysis of the shield-soil system helps to decouple the nonlinear multi-parameter problem and the regression process is conducted based on a group of on-site data of subway project in China. Fairly good consistency between the model results and the on-site recorded datum can be achieved. This work provides a useful tool for the analysis of the energy consumption of shield machines.

Mechanical model for operational loads prediction on shield cutter head during excavation

This paper presents a mechanical model to predict the operational loads acting on the cutter head of shield tunnel machine during excavation based on contact mechanics theory, in which the cutter head is considered as a rigid cylinder punch and the soil to be excavated is simplified as an elastic half-space. Then the estimation formulae of the operational loads are obtained and the influence of some key factors including the geological parameters, the radius of the cutter head and especially the excavation penetration can be analyzed based on the proposed model. The results show that the operational loads increase linearly when the machine works with a deeper excavation penetration. The prediction presented in this paper agrees with experimental results given by other researcher. It also can be seen that the geological condition affects both the quantity and the changing rate of loads with the excavation penetration. The proposed model may be a possible and feasible way to predict loads of shield tunnel machine.

A nonlinear multiple regression model for load identification of shield machine combined with mechanical analysis

The load identification of the shield machine is presented in this paper by introducing the mechanical analysis of shield excavating into the nonlinear multiple regression of on-site data. The analysis on mechanical characteristics of shield-soil system can decouple the nonlinear multi-parameter problem of load, so it is great helpful for the regression process to establish a load model. Then a load prediction model is obtained based on a group of on-site data of subway project in China. In addition the test combined with another group of independent data which is not involved in the regression is carried out. The result shows that the predicted load using the method proposed in this paper agrees well with on-site recorded data.