| Reliable estimates of jacking forces are essential because of their impact on many features of a microtunneling project. In this thesis, an analytical model, in the form of a computer code, was developed to predict jacking forces for a range of site and soil conditions, using classical soil mechanics and earth pressure principles. The model was tested by comparing actual and calculated jacking forces on three microtunneling projects. A data base of parameters was established for a wide range of soil conditions. A sensitivity analysis of the model input parameters showed that pipe diameter had the largest influence on jacking force, followed by height of soil cover, depth to groundwater, and soil properties. The analytical model and sensitivity analysis allow decisions on drive lengths, shaft spacing, pipe design, intermediate jacking stations, dewatering schemes, and thrust wall design to be made with a higher level of confidence than was previously possible. |
